Form 8-K
8-K — Paramount Gold Nevada Corp.
Accession: 0001193125-26-303179
Filed: 2026-07-14
Period: 2026-07-14
CIK: 0001629210
SIC: 1000 (METAL MINING)
Item: Other Events
Item: Financial Statements and Exhibits
Documents
8-K — d112598d8k.htm (Primary)
EX-23.1 (d112598dex231.htm)
EX-23.2 (d112598dex232.htm)
EX-23.3 (d112598dex233.htm)
EX-23.4 (d112598dex234.htm)
EX-23.5 (d112598dex235.htm)
EX-99.1 (d112598dex991.htm)
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8-K
8-K (Primary)
Filename: d112598d8k.htm · Sequence: 1
8-K
false 0001629210 0001629210 2026-07-14 2026-07-14
UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
WASHINGTON, D.C. 20549
FORM 8-K
CURRENT REPORT
Pursuant to Section 13 or 15(d)
of the Securities Exchange Act of 1934
Date of Report (Date of earliest event reported): July 14, 2026
Paramount Gold Nevada Corp.
(Exact name of Registrant as Specified in Its Charter)
Nevada
001-36908
98-0138393
(State or Other Jurisdiction
of Incorporation)
(Commission
File Number)
(IRS Employer
Identification No.)
665 Anderson Street
Winnemucca, Nevada
89445
(Address of Principal Executive Offices)
(Zip Code)
Registrant’s Telephone Number, Including Area Code: 775 625-3600
(Former Name or Former Address, if Changed Since Last Report)
Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:
☐
Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)
☐
Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)
☐
Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))
☐
Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))
Securities registered pursuant to Section 12(b) of the Act:
Title of each class
Trading
Symbol(s)
Name of each exchange
on which registered
Common Stock, $0.01 Par Value Per Share
PZG
NYSE American LLC
Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§ 230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§ 240.12b-2 of this chapter).
Emerging growth company ☐
If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐
Item 8.01
Other Events
On July 14, 2026, Paramount Gold Nevada Corp. (the “Company”) filed a technical report summary, effective as of May 27, 2026, which had been prepared in accordance with the requirements of subpart 1300 of Regulation S-K, for its Grassy Mountain Gold Project (the “Report”). The Report and the corresponding consent of the “Qualified Persons” are filed as Exhibits 99.1, 23.1, 23.2, 23.3, 23.4 and 23.5, respectively, to this Current Report on Form 8-K and are incorporated herein by reference.
Item 9.01
Financial Statements and Exhibits.
(d) Exhibits.
Exhibit
Number
Description
23.1
Consent of Qualified Person – Ausenco Engineering Canada Inc.
23.2
Consent of Qualified Person – RESPEC Company LLC
23.3
Consent of Qualified Person – WSP USA Inc.
23.4
Consent of Qualified Person – Geotechnical Mine Solutions
23.5
Consent of Qualified Person – SLR International Corporation
99.1
Technical Report Summary for the Grassy Mountain Gold Project effective May 26, 2026.
104
Cover Page Interactive Data File (embedded within the Inline XBRL document)
SIGNATURES
Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.
Paramount Gold Nevada Corp.
Date: July 14, 2026
By:
/s/ Rachel Goldman
Rachel Goldman, Chief Executive Officer
EX-23.1
EX-23.1
Filename: d112598dex231.htm · Sequence: 2
EX-23.1
Exhibit 23.1
Ausenco Engineering Canada ULC,
1050 West Pender Street, Suite 1200,
Vancouver,
British Columbia, V6E 3S7
Consent of Ausenco Engineering Canada ULC (Ausenco)
We had appropriate individual Qualified Persons prepare the content in the Sections they were responsible for, identified below, in the technical report
summary titled “Technical Report Summary on the Grassy Mountain Project, Oregon, U.S.A.” (the “TRS”) current as of May 27, 2026 for Paramount Gold Nevada Corp., portions of which are summarized on this Current Report on Form 8-K (the “Form 8-K”).
Furthermore, we state that:
i.
The TRS was prepared in accordance with Subpart 229.1300 of Regulations
S-K promulgated by the U.S. Securities and Exchange Commission and supports the Company’s Form 8-K;
ii.
We consent to the incorporation by reference of the TRS in the Registration Statements on Form S-3 (333-275376) and Form S-8 (No. 333-205024,
No. 333-262857 and No. 333-291058) (the “Registration Statements”);
iii.
We consent to the use of and references to our name in connection with the TRS,
Form 8-K and the Registration Statements; and
iv.
the information derived, summarized, quoted or referenced from the TRS, or portions thereof, that was prepared
by us, that we supervised the preparation of, and/or that was reviewed and approved by us, that is included or incorporated by reference in the Form 8-K and the Registration Statements.
Ausenco is responsible for authoring, and this consent pertains to, the following sections of the TRS: 1.1, 1.10, 1.16, 1.17.1, 1.18,
1.20, 1.21, 1.22, 2.1, 2.2, 2.3, 2.4.1, 2.5, 2.6, 2.7, 2.8, 9.2.1, 9.3.1, 10, 13.3, 14, 15.1, 15.2, 15.7.3, 15.8, 15.9, 15.10, 16, 18.1.1, 18.1.2, 18.1.3, 18.1.4, 18.1.5, 18.1.6, 18.1.7, 18.1.9, 18.1.10.2, 18.1.11, 18.1.12, 18.1.13, 18.2.1, 18.2.3,
18.2.4, 19, 22.1, 22.6, 22.11, 22.12.1, 22.12.2, 22.12.6, 22.13, 22.15, 22.16, 22.17, 22.18.1.2, 22.18.1.5, 22.18.1.9, 22.18.1.10, 22.18.2.2, 23.1, 23.2, 23.7, 24 and 25.
Dated at Vancouver, Canada this 14th day of July, 2026
/s/ Tommaso Roberto Raponi
Ausenco Engineering Canada ULC
EX-23.2
EX-23.2
Filename: d112598dex232.htm · Sequence: 3
EX-23.2
Exhibit 23.2
RESPEC Company, LLC,
3824 Jet Drive
Rapid City, SD 57703
Consent of RESPEC
Company, LLC (RESPEC)
RESPEC Company, LLC (RESPEC) had appropriate individual Qualified Persons prepare the content in the Sections they were
responsible for, identified below, in the technical report summary titled “Technical Report Summary on the Grassy Mountain Project, Oregon, U.S.A.” (the “TRS”) current as of May 27, 2026 for Paramount Gold Nevada Corp.,
portions of which are summarized on this Current Report on Form 8-K (the “Form 8-K”).
Furthermore, we state that:
i.
The TRS was prepared in accordance with Subpart 229.1300 of Regulations
S-K promulgated by the U.S. Securities and Exchange Commission and supports the Company’s Form 8-K;
ii.
We consent to the incorporation by reference of the TRS in the Registration Statements on Form S-3 (333-275376) and Form S-8 (No. 333-205024,
No. 333-262857 and No. 333-291058) (the “Registration Statements”);
iii.
We consent to the use of and references to our name in connection with the TRS, Form 8-K and the Registration Statements; and
iv.
the information derived, summarized, quoted or referenced from the TRS, or portions thereof, that was prepared
by us, that we supervised the preparation of, and/or that was reviewed and approved by us, that is included or incorporated by reference in the Form 8-K and the Registration Statements.
RESPEC is responsible for authoring, and this consent pertains to, the following sections of the TRS: Geology and Resources: 1.5, 1.6, 1.7, 1.8, 1.9, 1.11,
1.12, 2.4.3, 5, 6, 7, 8, 9.1, 9.2.2, 9.3.2, 11, 22.3, 22.4, 22.5, 22.7, 22.18.1.1, 22.18.1.3, 22.18.2.1, 23.3, 24, 25.2, 25.3 and 25.5 Mine Engineering: 1.13, 1.14, 1.15, 2.4.3, 12, 13.1, 13.7, 13.8, 13.9, 13.10, 13.11.1, 13.11.2, 13.11.3, 13.11.4,
13.11.5, 13.11.7, 13.11.8, 13.12, 13.13, 13.14, 18.1.8, 18.2.2, 22.8, 22.9, 22.18.1.4, 22.18.1.7, 22.18.1.8, 22.18.2.3, 22.18.2.4, 22.18.2.6, 22.18.2.7, 23.4, 24, 25.2, 25.3 and 25.5
Dated at Vancouver, Canada this 14th day of July, 2026
“signed”
/s/ Michael S. Lindholm
Michael S. Lindholm
Principal Geologist
RESPEC Company, LLC
EX-23.3
EX-23.3
Filename: d112598dex233.htm · Sequence: 4
EX-23.3
Exhibit 23.3
Christopher Jason MacMahon, PE
WSP USA Inc.
10615 Professional Circle, Suite 204
Reno, Nevada
89521
Consent of Qualified Person
I, Christopher Jason MacMahon, state that I am responsible for preparing or supervising the preparation of part(s) of the technical report summary titled
“Technical Report Summary on the Grassy Mountain Project, Oregon, U.S.A.”, with an effective date of May 27, 2026, as signed and certified by me (the “Technical Report Summary”) for Paramount Gold Nevada Corp. (the
“Company”).
Furthermore, I state that:
i.
The Technical Report Summary was prepared in accordance with Subpart 229.1300 of Regulations S-K promulgated by the U.S. Securities and Exchange Commission;
ii.
I consent to the Company’s public filing of the Technical Report Summary as an exhibit to and as
referenced in the Company’s Current Report on Form 8-K (“Form 8-K”), and to the incorporation by reference of the Technical Report Summary in the
Registration Statements on Form S-3 (333-275376) and Form S-8 (No. 333-205024, No. 333-262857 and No. 333-291058) (the “Registration Statements”) (collectively, the “Documents”);
iii.
I consent to the use of my name, or any quotation from or summarization in the Documents of the parts of the
Technical Report Summary for which I am responsible (as listed below);
iv.
I confirm that I have read the Documents, and that the Documents fairly and accurately reflect, in the form and
context in which it appears, the information in the parts of the Technical Report Summary for which I am responsible, as follows: 1.17.2 thru 1.17.5, 2.4.5, 15.3 thru 15.7.2, 18.1.10.1, 22.12.3 thru 22.12.5, 24 and 25.2 and 25.3.
Dated at Reno, Nevada this 14th day of July, 2026
“signed”
/s/ Christopher Macmahon
Christopher J, Macmahon, PE (OR)
EX-23.4
EX-23.4
Filename: d112598dex234.htm · Sequence: 5
EX-23.4
Exhibit 23.4
Geotechnical Mine Solutions Inc.,
2957 San
Sebastián Street,
Las Condes, Santiago de Chile
Consent of Geotechnical Mine Solutions Inc. (GMS)
We had appropriate individual Qualified Persons prepare the content in the Sections they were responsible for, identified below, in the technical report
summary titled “Technical Report Summary on the Grassy Mountain Project, Oregon, U.S.A.” (the “TRS”) current as of May 27, 2026 for Paramount Gold Nevada Corp., portions of which are summarized on this Current Report on Form 8-K (the “Form 8-K”).
Furthermore, we state that:
i.
The TRS was prepared in accordance with Subpart 229.1300 of Regulations
S-K promulgated by the U.S. Securities and Exchange Commission and supports the Company’s Form 8-K;
ii.
We consent to the incorporation by reference of the TRS in the Registration Statements on Form S-3 (333-275376) and Form S-8 (No. 333-205024,
No. 333-262857 and No. 333-291058) (the “Registration Statements”);
iii.
We consent to the use of and references to our name in connection with the TRS, Form 8-K and the Registration Statements; and
iv.
the information derived, summarized, quoted or referenced from the TRS, or portions thereof, that was prepared
by us, that we supervised the preparation of, and/or that was reviewed and approved by us, that is included or incorporated by reference in the Form 8-K and the Registration Statements.
GMS is responsible for authoring, and this consent pertains to, the following sections of the TRS: 2.4.2, 13.2, 13.4, 13.5, 13.6, 13.11.6, 22.10, 23.5
and 24.
Dated at Las Condes, Santiago de Chile this 14th day of July, 2026
“signed”
/s/ Andrés Torres L.
Andrés Torres L.
Geotechnical Mine Solutions Inc.
EX-23.5
EX-23.5
Filename: d112598dex235.htm · Sequence: 6
EX-23.5
Exhibit 23.5
SLR International Corporation,
1658 Cole Blvd, Suite
100
Lakewood, Colorado 80401
Consent of SLR International Corporation (SLR)
We had appropriate individual Qualified Persons prepare the content in the Sections they were responsible for, identified below, in the technical report
summary titled “Technical Report Summary on the Grassy Mountain Project, Oregon, U.S.A.” (the “TRS”) current as of May 27, 2026 for Paramount Gold Nevada Corp., portions of which are summarized on this Current Report on Form 8-K (the “Form 8-K”).
Furthermore, we state that:
i.
The TRS was prepared in accordance with Subpart 229.1300 of Regulations
S-K promulgated by the U.S. Securities and Exchange Commission and supports the Company’s Form 8-K;
ii.
We consent to the incorporation by reference of the TRS in the Registration Statements on Form S-3 (333-275376) and Form S-8 (No. 333-205024,
No. 333-262857 and No. 333-291058) (the “Registration Statements”);
iii.
We consent to the use of and references to our name in connection with the TRS, Form 8-K and the Registration Statements; and
iv.
the information derived, summarized, quoted or referenced from the TRS, or portions thereof, that was prepared
by us, that we supervised the preparation of, and/or that was reviewed and approved by us, that is included or incorporated by reference in the Form 8-K and the Registration Statements.
SLR is responsible for authoring, and this consent pertains to, the following sections of the TRS: 1.19, 2.4.4, 3.5, 9.2.3, 9.3.3, 17, 18.1.14, 22.14,
22.18.1.6, 22.18.2.5, 23.6, 23.8, 24, 25.2 and 25.3.
Dated at Colorado, USA this 14th day of July,
2026
“signed”
/s/ Jeremy Scott Collyard
Jeremy Scott Collyard, PMP, MMSA, QP
SLR
International Corporation
EX-99.1
EX-99.1
Filename: d112598dex991.htm · Sequence: 7
EX-99.1
Exhibit 99.1
Date and Signature Page
This technical report summary (the TRS), entitled “Grassy Mountain Project: S-K 1300 Technical Report Summary, Oregon, United States of
America” is current as of May 27, 2026 and has been prepared by:
Qualified Person or Firm
Responsible for the following sections
Signature
Date
Ausenco Engineering Canada ULC
1.1, 1.10, 1.16, 1.17.1, 1.18, 1.20, 1.21, 1.22, 2.1, 2.2, 2.3, 2.4.1, 2.5, 2.6, 2.7, 2.8, 9.2.1, 9.3.1, 10, 13.3, 14, 15.1, 15.2, 15.7.3, 15.8, 15.9, 15.10, 16, 18.1.1, 18.1.2, 18.1.3, 18.1.4, 18.1.5, 18.1.6, 18.1.7, 18.1.9,
18.1.10.2, 18.1.11, 18.1.12, 18.1.13, 18.2.1, 18.2.3, 18.2.4, 19, 22.1, 22.6, 22.11, 22.12.1, 22.12.2, 22.12.6, 22.13, 22.15, 22.16, 22.17, 22.18.1.2, 22.18.1.5, 22.18.1.9, 22.18.1.10, 22.18.2.2, 23.1, 23.2, 23.7, 24, 25
“signed”
July 14, 2026
Geotechnical Mine Solutions Inc.
2.4.2, 13.2, 13.4, 13.5, 13.6, 13.11.6, 22.10, 23.5, 24
“signed”
July 14, 2026
RESPEC Company LLC (Geology and Resources)
1.5, 1.6, 1.7, 1.8, 1.9, 1.11, 1.12, 2.4.3, 5, 6, 7, 8, 9.1, 9.2.2, 9.3.2, 11, 22.3, 22.4, 22.5, 22.7, 22.18.1.1, 22.18.1.3, 22.18.2.1, 23.3, 24, 25.2, 25.3, 25.5
“signed”
July 14, 2026
RESPEC Company LLC (Mine Engineering)
1.13, 1.14, 1.15, 2.4.3, 12, 13.1, 13.7, 13.8, 13.9, 13.10, 13.11.1, 13.11.2, 13.11.3, 13.11.4, 13.11.5, 13.11.7, 13.11.8, 13.12, 13.13, 13.14, 18.1.8, 18.2.2, 22.8, 22.9, 22.18.1.4, 22.18.1.7, 22.18.1.8, 22.18.2.3, 22.18.2.4,
22.18.2.6, 22.18.2.7, 23.4, 24, 25.2, 25.3, 25.5
“signed”
July 14, 2026
SLR International Corporation
1.19, 2.4.4, 3.5, 9.2.3, 9.3.3, 17, 18.1.14, 22.14, 22.18.1.6, 22.18.2.5, 23.6, 23.8, 24, 25.2, 25.3
“signed”
July 14, 2026
WSP USA Inc.
1.17.2, 1.17.3, 1.17.4, 1.17.5, 2.4.5, 15.3, 15.4, 15.5, 15.6, 15.7.1, 15.7.2, 18.1.10.1, 22.12.3, 22.12.4, 22.12.5, 24, 25.2, 25.3
“signed”
July 14, 2026
Paramount Gold Nevada Corp.
1.2, 1.3, 1.4, 3.1, 3.2, 3.3, 3.4, 3.6, 3.7, 3.8, 4, 20, 21, 22.2
“signed”
July 14, 2026
Table of Contents
1 Executive Summary
1
1.1 Introduction
1
1.1.1 Terms of Reference
1
1.1.2 Effective Dates
1
1.2 Property Description
2
1.3 Mineral Tenure, Surface Rights, Water Rights, Royalties and Agreements
2
1.4 Accessibility, Climate, Local Resources, Infrastructure and Physiography
3
1.5 History
3
1.6 Geological Setting, Mineralization and Deposit
4
1.7 Exploration
4
1.8 Sample Preparation, Analyses and Security
5
1.9 Data Verification
6
1.10 Mineral Processing and Metallurgical Testwork
7
1.11 Mineral Resource Estimate
8
1.12 Mineral Resource Statement
10
1.13 Mineral Reserve Estimate
10
1.14 Mineral Reserve Statement
12
1.15 Mining Methods
12
1.15.1 Overview
12
1.15.2 Mine Design
13
1.15.3 Mine Production Plan
14
1.16 Processing and Recovery Methods
15
1.17 Infrastructure
18
1.17.1 Overview
18
1.17.2 Temporary Waste Rock Storage Facilities (TWRSF) and Borrow Pits
18
1.17.3 Tailings Storage Facility
18
1.17.4 Water Management
19
1.17.5 Water Balance
19
1.18 Market Studies and Contracts
19
1.19 Environmental, Permitting and Social Considerations
20
1.19.1 Environmental Considerations
20
1.19.2 Permitting Considerations
20
Grassy Mountain Project
S - K 1300 Technical Summary and Feasibility Report
Page i
May 27, 2026
1.19.3 Social Considerations
20
1.19.4 Closure and Reclamation Considerations
20
1.20 Capital and Operating Cost
20
1.20.1 Capital Cost Estimate
20
1.20.2 Operating Cost Estimate
21
1.21 Economic Analysis
22
1.21.1 Economic Summary
22
1.21.2 Sensitivity Analysis
23
1.22 Conclusions
23
2 Introduction
24
2.1 Introduction
24
2.2 Terms of Reference
24
2.3 Qualified Persons (QP)
24
2.4 Site Visits and Scope of Personal Inspection
25
2.4.1 Site Inspection by the Qualified Person of Ausenco
25
2.4.2 Site Inspection by the Qualified Person of GMS
25
2.4.3 Site Inspection by the Qualified Persons of RESPEC
26
2.4.4 Site Inspection by the Qualified Person of SLR
26
2.4.5 Site Inspection by the Qualified Person of WSP
26
2.5 Effective Dates
26
2.6 Information Sources and References
27
2.7 Previous Technical Reports
27
2.8 Currency, Units, Abbreviations and Definitions
28
3 Property Description
34
3.1 Introduction
34
3.2 Mineral Tenure
35
3.2.1 Mineral Concession Payment Terms
35
3.2.2 Land Access and Ownership Agreements
35
3.2.3 Seabridge Gold Corporation
35
3.2.4 Sherry and Yates, Inc.
36
3.2.5 Cryla LLC
36
3.3 Royalties and Additional Encumbrances
37
3.3.1 Seabridge Gold
37
3.3.2 Sherry and Yates
37
3.3.3 Cryla
38
3.3.4 Other Encumbrances
38
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3.4 Environmental Liabilities
38
3.5 Environmental Permitting
38
3.6 Surface Rights
39
3.7 Water Rights
39
3.8 Summary Statement
39
4 Accessibility, Climate, Local Resources, Infrastructure and Physiography
40
4.1 Access
40
4.2 Physiography
41
4.3 Climate
42
4.4 Water Supply
42
4.5 Power
42
4.6 Infrastructure
42
4.7 Community Services
42
5 History
44
5.1 Introduction
44
5.2 1986-1996 Exploration
44
5.2.1 Atlas 1986-1992
44
5.2.2 Newmont 1992-1996
45
5.2.3 1996 Exploration at Outlying Targets within the Grassy Mountain Claims
Group
45
5.3 1998-2016 Exploration
48
5.3.1 Tombstone 1998
48
5.3.2 Seabridge 2000-2010
48
5.3.3 Calico 2011-2016
49
5.4 Production
50
6 Geological Setting, Mineralization and Deposit
51
6.1 Introduction
51
6.2 Regional Geologic Setting
51
6.3 Local and Project Geology
51
6.4 Grassy Mountain Deposit
54
6.4.1 Geology
54
6.4.2 Structure
56
6.4.3 Alteration and Mineralization
56
6.5 Deposit Types
58
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7 Exploration
60
7.1 Exploration
60
7.2 Drilling
62
7.2.1 Historical Drilling, 1987-2012
66
7.2.2 Paramount 2016–2019
68
7.3 Drill-Hole Collar and Down-Hole Surveys
71
7.4 Sample Quality
72
7.4.1 Core Samples
72
7.4.2 RC Samples
74
7.5 Summary Statement
75
8 Sample Preparation, Analyses, and Security
76
8.1 Introduction
76
8.2 Sample Preparation, Analysis and Security
76
8.2.1 Atlas 1987-1992
76
8.2.2 Newmont 1992-1996
76
8.2.3 Tombstone 1998
77
8.2.4 Calico 2011-2012
77
8.2.5 Paramount 2016-2019
79
8.3 Quality Assurance/Quality Control Procedures
79
8.3.1 Atlas QA/QC, 1987–1992
79
8.3.2 Newmont QA/QC, 1992–1996
80
8.3.3 Tombstone QA/QC, 1998
80
8.3.4 Calico QA/QC, 2011–2012
81
8.3.5 Paramount QA/QC, 2016–2019
81
8.4 Quality Assurance/Quality Control Results
82
8.4.1 Atlas, 1987–1992
82
8.4.2 Newmont, 1992–1996
87
8.4.3 Tombstone 1998
89
8.4.4 Calico, 2011–2012
90
8.4.5 Paramount 2016–2017
93
8.4.6 Paramount 2018–2019
100
8.4.7 Discussion of QA/QC Results
100
8.5 Summary Statement
100
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9 Data Verification
101
9.1 Drill-Hole Data
101
9.1.1 Collar Data
101
9.1.2 Down-Hole Survey Data
102
9.1.3 Assay Data
102
9.1.4 Additional Data Verification
103
9.2 Site and Field Office Inspections
103
9.2.1 Ausenco
103
9.2.2 RESPEC
103
9.2.3 SLR
104
9.3 Summary Statement
104
9.3.1 Ausenco
104
9.3.2 RESPEC
104
9.3.3 SLR
105
10 Mineral Processing and Metallurgical Testing
106
10.1 Introduction
106
10.2 Historical Testwork Programs
107
10.2.1 Historical Studies 1989 to 2012
107
10.2.2 Historical Testwork from 2018 PFS
107
10.3 2020 FS Testwork
108
10.3.1 Objectives
108
10.3.2 SGS Testwork Program 15944-002 Scope of Work
108
10.3.3 McClelland Testwork Program MLI 4551 Scope of Work
108
10.3.4 Sample Selection for SGS Program 15944-02
108
10.3.5 Sample Selection for McClelland Program MLI 4551
109
10.4 Presentation and Discussion of Results
110
10.4.1 Ore Characterization and Deleterious Elements
110
10.4.2 Comminution Test Results
111
10.4.3 Mineralogical Analysis
112
10.4.4 Leach Tests
113
10.4.5 Cyanide Destruction
118
10.5 Metallurgical Variability
119
10.5.2 Sample Selection for SGS Program 15944-02
120
10.5.3 Sample Selection for McClelland Program MLI 4551
120
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10.6 Recovery Estimation
120
10.6.1 Leach Recovery, SGS Program 15944-001, SGS Program 15944-002 and McClelland Program
MLI 4551
120
10.7 Summary
126
10.8 Qualified Person’s Opinion on Data Adequacy
127
11 Mineral Resource Estimates
128
11.1 Introduction
128
11.2 Grassy Mountain project Data
128
11.2.1 Drill-Hole Database
128
11.2.2 Topography
128
11.3 Deposit Geology Relevant to Resource Modelling
128
11.4 Geologic Modeling
130
11.5 Water Table and Oxidation Modeling
130
11.6 Density Modeling
130
11.7 Gold and Silver Modeling
131
11.7.1 Mineral Domains
131
11.7.2 Assay Coding, Capping, and Compositing
137
11.7.3 Block Model Coding
139
11.7.4 Grade Interpolation
139
11.7.5 Model Checks
141
11.8 Grassy Mountain Mineral Resources
141
11.8.1 Pit Optimizations, Cutoff Grades and Reporting Prices
141
11.8.2 Mineral Resources
143
11.8.3 Classification
150
11.9 Additional Comments on the Modeling of the Mineral Resources
152
12 Mineral Reserve Estimates
153
12.1 Introduction
153
12.1.1 Estimation Procedure
153
12.2 Mineral Reserve Statement
154
12.3 Economic Cut-off Grade Calculation
154
12.3.1 Gold Price
154
12.3.2 Silver Price
156
12.4 Stope Design
156
12.5 Dilution and Recovery
158
12.5.1 External Dilution
158
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12.5.2 Internal Dilution
159
12.5.3 Mining Recovery
159
12.6 Discussion of Mineral Reserves
159
12.7 Classification
159
13 Mining Methods
161
13.1 Mining Method Selection
161
13.1.1 Underhand Mechanized Cut-and-Fill Mining
161
13.1.2 Mining Method Sequence
165
13.2 Geotechnical Analysis
167
13.2.1 Overview
167
13.2.2 Geotechnical Characterization
168
13.2.3 Golder Geotechnical Appraisal
169
13.2.4 Ausenco Geotechnical Work
171
13.2.5 Feasibility Study Geotechnical Analysis
173
13.2.6 Geotechnical Model
176
13.2.7 Summary of Geotechnical Analysis and Evaluation for Underground Mining
178
13.3 Hydrogeological modelling
178
13.4 Excavation Design
178
13.4.1 Mining Method Selection
178
13.4.2 Drift Sizes and Stability Assessments
179
13.5 Numerical Modelling
182
13.5.1 Ground Support
189
13.5.2 Ground Monitoring Program
190
13.5.3 Global Extraction Sequence
190
13.6 Portal Design
191
13.7 Grade Control
192
13.8 Personnel
192
13.9 Development Design
192
13.9.1 Mine Design Parameters
192
13.9.2 Level Access
193
13.9.3 Station Design
194
13.10 Equipment Selection
195
13.11 Production and Development Productivity Assumptions
195
13.11.1 Drilling and Bolting
195
13.11.2 Shotcrete
197
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13.11.3 Blasting
200
13.11.4 Mucking
200
13.11.5 Hauling
201
13.11.6 Backfilling
203
13.11.7 Backfill Plant
206
13.11.8 Production Scheduling
208
13.12 Underground Infrastructure and Services
209
13.12.1 Ventilation
209
13.12.2 Underground Dewatering
211
13.12.3 Underground Power
212
13.12.4 Underground Communications
213
13.12.5 Underground Refuge and Escape Ways
213
13.13 Mining Costs
214
13.14 Life-of-Mine Production
214
14 Processing and Recovery Methods
220
14.1 Introduction
220
14.2 Process Design Criteria
220
14.3 Process Flowsheet Development
222
14.4 Overall Process Description
225
14.4.1 Crushing Circuit
225
14.4.2 Grinding Circuit
226
14.4.3 Leach/CIL
226
14.4.4 Carbon Management
227
14.4.5 Gold Room
228
14.4.6 Cyanide Detoxification and Tailings Deposition
229
14.4.7 Reagent Handling and Storage
229
14.4.8 Air Supply and Distribution
231
14.4.9 Water Supply and Distribution
231
14.5 Personnel
232
14.6 Sampling and Metallurgical Laboratory
232
14.7 Projected Energy Requirements
232
14.8 Project Water Requirements
232
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15 Infrastructure
234
15.1 Introduction
234
15.2 Access
236
15.3 Temporary Waste Rock Storage Facility (TWRSF)
236
15.4 Basalt Borrow Quarry
236
15.5 Tailings Storage Facility
237
15.5.1 Topography, Drainage, and Vegetation
239
15.5.2 Past Studies, Subsurface Investigations, and Civil Design
239
15.5.3 Design Objectives
240
15.5.4 TSF Design
241
15.5.5 Monitoring
243
15.5.6 Closure
244
15.6 Closure Cover Borrow Areas
245
15.7 Water Management
245
15.7.1 Non-Contact Water Management
245
15.7.2 Contact Water Management
247
15.7.3 Site-wide Water Balance
249
15.8 Built Infrastructure
250
15.9 Camps and Accommodation
251
15.10 Power and Electrical
251
16 Market Studies
252
16.1 Introduction
252
16.2 Market Studies
252
16.3 Metal Pricing and Projections
252
16.3.1 Economic Analysis
252
16.3.2 Metal Pricing Forecasts
253
16.4 Contracts
254
16.5 QP Comment
254
17 Environmental Studies, Permitting, Plans, Negotiations or Agreements with Local
Individuals or Groups
255
17.1 Introduction
255
17.2 Permit History
257
17.3 Project Permits
257
17.4 State of Oregon Permit Processing
257
17.4.1 Federal Plan of Operations Processing
260
17.4.2 Malheur County Permit Processing
261
17.5 Environmental Study Results and Known Issues
261
17.5.1 Baseline Studies
261
17.5.2 Geochemical Characterization and Groundwater Studies
263
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17.6 Waste Disposal, Monitoring, Water Management
264
17.7 Social and Community Issues
265
17.8 Closure
265
17.9 Environmental and Permitting Risks and Opportunities
266
17.10 Qualified Person’s Opinion
267
18 Capital and Operating Costs
268
18.1 Capital Cost Estimate
268
18.1.1 Introduction
268
18.1.2 Cost Estimate Summary – Initial Capital
269
18.1.3 Cost Estimate Summary – Sustaining Capital
271
18.1.4 Definition of Costs
271
18.1.5 Methodology
272
18.1.6 Exchange Rates
272
18.1.7 Market Availability
271
18.1.8 Mining Capital Cost Estimate
271
18.1.9 Processing and Overall Site Infrastructure Capital Cost Estimate
276
18.1.10 Tailings Storage and Temporary Waste Rock Storage Facilities Capital Cost
Estimate
281
18.1.11 Indirect Capital Cost Estimate
282
18.1.12 Owner’s Costs
284
18.1.13 Contingency
285
18.1.14 Reclamation and Closure Capital Cost Estimate
285
18.2 Operating Cost Estimate
285
18.2.1 Summary and Basis of Operating Cost Estimate
285
18.2.2 Mining Operating Cost Estimate
286
18.2.3 Process Operating Cost Estimate
288
18.2.4 General and Administrative Operating Cost Estimate
291
19 Economic Analysis
292
19.1 Forward-Looking Information
292
19.2 Methodology Used
293
19.3 Financial Model Parameters
294
19.4 Taxes
294
19.5 Royalty
294
19.6 Economic Analysis
295
19.7 Sensitivity Analysis
299
19.8 Conclusion – Economic Analysis
302
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20 Adjacent Properties
303
21 Other Relevant Data and Information
304
22 Interpretation and Conclusions
305
22.1 Introduction
305
22.2 Mineral Tenure, Surface Rights, Water Rights, Royalties and Agreements
305
22.3 Geology and Mineralization
305
22.4 Exploration
306
22.5 Analytical Data Collection in Support of Mineral Resource Estimation
306
22.6 Metallurgical Testwork
306
22.7 Mineral Resource Estimation
307
22.8 Mineral Reserve Estimates
308
22.9 Mining Method
308
22.10 Geotechnical Considerations
309
22.11 Processing and Recovery Methods
310
22.12 Infrastructure
310
22.12.1 Key Infrastructure
310
22.12.2 Roads and Power
310
22.12.3 Waste Rock Storage and Borrow Pits
310
22.12.4 Tailings Storage Facility
310
22.12.5 Water Management
311
22.12.6 Water Supply
311
22.13 Markets and Contracts
311
22.14 Environmental, Permitting and Social Considerations
312
22.15 Capital Cost Estimate
312
22.16 Operating Cost Estimate
313
22.17 Economic Analysis
313
22.18 Risks and Opportunities
314
22.18.1 Risks
314
22.18.2 Opportunities
317
23 Recommendations
319
23.1 Introduction
319
23.2 Metallurgical Testing
319
23.3 Mineral Resource Estimate
319
23.4 Mining Methods
320
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23.5 Geotechnical
321
23.6 Hydrology
323
23.7 Infrastructure
323
23.8 Environmental Studies, Permitting and agreements with local individuals or
groups
324
24 References
325
25 Reliance on Information Provided by the Registrar
331
25.1 Introduction
331
25.2 Property Agreements, Mineral Tenure, Surface Rights and Royalties
331
25.3 Environmental, Permitting, Closure, and Social and Community Impact
331
25.4 Taxation
332
25.5 Markets
332
Appendix A – Claims List
333
List of Tables
Table 1-1:
Grassy Mountain Mineral Resource Estimate Inclusive of Mineral Reserves – Effective date: February 28, 2026
10
Table 1-2:
Cut-off Grade Input Parameters for Gold Metal
11
Table 1-3:
Gold and Silver Mineral Reserve Estimates
12
Table 1-4:
Initial Capital Cost Estimate Summary (direct and indirect)
21
Table 1-5:
Summary of forecast project economics
22
Table 2-1:
Abbreviations and Acronyms
28
Table 2-2:
Units of Measurement
31
Table 7-1:
Grassy Mountain Claim Block Drilling Summary
62
Table 7-2:
Paramount 2016–2019 RC Pre-Collar vs. Core Lengths
70
Table 8-1:
Grassy Mountain Certified Reference Materials for 2011–2012
81
Table 8-2:
Grassy Mountain Certified Reference Materials Employed by Paramount, 2016–2019
82
Table 10-1:
Metallurgical Testwork Summary
106
Table 10-2:
2018 PFS Testwork Scope
109
Table 10-3:
Metallurgical Test Matrix for SGS Program 15944-002
109
Table 10-4:
FS Production Composites Sample Composition
110
Table 10-5:
Head Assays
110
Table 10-6:
Hazen 1990 Comminution Results
111
Table 10-7:
Summary of JK DWT Results
111
Table 10-8:
Bond Rod Mill Grindability Test Results
112
Table 10-9:
Ball Mill Work Indices
112
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May 27, 2026
Table 10-10:
Average Cyanide and Lime Consumption
117
Table 10-11:
Cyanide Destruction Test Results from Historical Work
118
Table 10-12:
Cyanide Destruction Test Results – Continuous Test
118
Table 10-13:
Leach Test Data Used for Recovery Estimation
121
Table 10-14:
Estimated Additional Plant Losses for Gold
125
Table 10-15:
Estimated Additional Plant Losses for Silver
126
Table 11-1:
Hazen Research, Inc. tonnage Factors
130
Table 11-2:
Combined Atlas and Paramount tonnage Factors
131
Table 11-3:
Approximate Grade Ranges of Gold and Silver Domains
132
Table 11-4:
Grassy Mountain Gold and Silver Assay Caps by Domain
137
Table 11-5:
Descriptive Statistics of Grassy Mountain Coded Gold Assays
137
Table 11-6:
Descriptive Statistics of Grassy Mountain Coded Silver Assays
138
Table 11-7:
Descriptive Statistics of Grassy Mountain Gold Composites
138
Table 11-8:
Descriptive Statistics of Grassy Mountain Silver Composites
138
Table 11-9:
Estimation Parameters
140
Table 11-10:
Pit Optimization Parameters
142
Table 11-11:
Parameters Used to Determine Cut-Off Grade for Mineral Resources Potentially Amenable to Underground Mining Methods
143
Table 11-12:
Grassy Mountain Gold and Silver Resources – Exclusive of Mineral Reserves
144
Table 11-13:
Grassy Mountain Gold and Silver Resources – Inclusive of Mineral Reserves
145
Table 11-14:
Resource Classification Parameters
151
Table 12-1:
Mineral Reserves Statement
154
Table 12-2:
Cut-off Grade Input Parameters for Gold Metal
155
Table 12-3:
Total Mineral Reserves Multiplied by the Metal Price
156
Table 12-4:
Stope Optimization Parameters
157
Table 12-5:
Reserve Classification Parameters
160
Table 13-1:
Rock Quality Categories
170
Table 13-2:
Rock Quality Categories
172
Table 13-3:
Summary of RMR (Bieniawski, 1976) Values by Area
173
Table 13-4:
Intact Rock Strength for Geotechnical Units Calculated from PLTs
175
Table 13-5:
Summary of RQD, RMR76, and GSI 2013 Values by Geotechnical Unit
177
Table 13-6:
Strength Parameters for Geotechnical Units
177
Table 13-7:
Iso-Probability Contours for Stable Cases Results
180
Table 13-8:
Iso-Probability Contours for Failure Cases Results
181
Table 13-9:
Reinforcement and Support Design for Mine Development Under Rock Mass Environment
189
Table 13-10:
Reinforcement and Support Design for Mine Development Under Backfill Environment
189
Table 13-11:
Mine Design Parameters
192
Table 13-12:
Mining Mobile Equipment List
195
Table 13-13:
Drilling First Principles Assumptions
196
Table 13-14:
Bolting First Principles Assumptions
197
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May 27, 2026
Table 13-15:
Shotcrete First Principals Assumptions
198
Table 13-16:
Blasting First Principles Assumptions
200
Table 13-17:
Haulage First Principles Assumptions
202
Table 13-18:
CRF Mix Recipe for UCS Testing
204
Table 13-19:
Calendars by Crew
208
Table 13-20:
Production Rates
208
Table 13-21:
Production Limits on Production Fields
208
Table 13-22:
Estimated Underground LOM Water Requirement
212
Table 13-23:
Mine Production Summary
217
Table 13-24:
Material to the Mill
218
Table 13-25:
Development Schedule
220
Table 14-1:
Process Design Criteria
241
Table 15-1:
Stage Capacity Relationship
249
Table 15-2:
Annual Average Water Balance
250
Table 15-3:
Built Infrastructure Requirements
252
Table 16-1:
Estimated Payability and Refining Costs
253
Table 16-2:
Gold Price Average (LBMA PM), $/oz
253
Table 16-3:
Silver Price Average (LBMA PM), $/oz
253
Table 16-4:
Mid-term gold price estimate by year from various organizations
255
Table 17-1:
Surface Disturbance for the Proposed Project
256
Table 17-2:
Permitting
268
Table 18-1:
Capital Cost Estimate Input Areas
270
Table 18-2:
Initial Capital Cost Estimate Summary (direct and indirect)
270
Table 18-3:
Initial Capital Cost Estimate by Major Discipline
271
Table 18-4:
Sustaining Capital Cost Estimate Summary (direct and indirect)
273
Table 18-5:
Exchange Rates used in the FS
273
Table 18-6:
Underground Capital Costs
275
Table 18-7:
Underground Leasing Costs
275
Table 18-8:
Initial Mining Capital Cost Estimate Summary
280
Table 18-9:
Initial Capital Cost Estimate Summary for Process and Site Infrastructure Areas
272
Table 18-10:
Initial TSF Capital Cost Estimate Summary
284
Table 18-11:
Initial Capital Cost Estimate Summary for Indirects
284
Table 18-12:
Initial Owner’s Cost Estimate Summary
284
Table 18-13:
Summary of operating costs over LOM
286
Table 18-14:
Summary of Underground Mining Costs per ton
286
Table 18-15:
Underground Labor Summary
287
Table 18-16:
Average Annual Process Operating Cost
289
Table 18-17:
Process Plant Labor
290
Table 18-18:
Annual Average G&A Operating Cost Summary
291
Table 19-1:
Summary of Forecast Project Economics
296
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May 27, 2026
Table 19-2:
Project Cashflow on an Annualized Basis
296
Table 19-3:
Summary Pre-Tax Sensitivity Analysis
299
Table 19-4:
Summary Post-Tax Sensitivity Analysis
300
Table 23-1:
Phase 1 Recommended Work Program
318
Table 23-2:
Recommended Work Program for Mineral Resource Estimate
319
Table 23-3:
Recommended Work Program for Mining Methods
320
Table 23-4:
Recommended Geotechnical Program
322
List of Figures
Figure 1-1:
Proposed Mine Production Schedule (tons by period)
14
Figure 1-2:
Simplified Overall Flowsheet
16
Figure 1-3:
Proposed Plant Site Layout
17
Figure 2-1:
Project Location Plan
25
Figure 3-1:
Location of the Grassy Mountain Project
34
Figure 3-2:
Grassy Mountain Claim Group
36
Figure 3-3:
Sherry and Yates Area of Interest
37
Figure 4-1:
Access to Grassy Mountain Claims Group
40
Figure 4-2:
Photograph of Grassy Mountain Area Looking
41
Figure 4-3:
Proposed Power Source for the Planned Operation
43
Figure 5-1:
Outlying Target Area Map
46
Figure 5-2:
Map of 2012 CSMAT Lines
49
Figure 5-3:
CSAMT Inversion: Resistivity at 328 to 656 Feet Below Surface
50
Figure 6-1:
Grassy Mountain Regional Geology
52
Figure 6-2:
Stratigraphic Column for the Grassy Mountain Area
53
Figure 6-3:
Grassy Mountain Deposit Area Geologic Map
55
Figure 6-4:
Conceptual Hot-Springs Epithermal Deposit Model
59
Figure 7-1:
2018 Aerial Magnetic Survey of Grassy Mountain Area
61
Figure 7-2:
Locations of Drill Holes Within the Grassy Mountain Claims Group
63
Figure 7-3:
Locations of Holes Drilled in the Grassy Mountain Deposit Area
65
Figure 7-4:
Gold Grade vs. RQD
73
Figure 7-5:
Gold Grade vs. Core Recovery
74
Figure 8-1:
Cone Analyses of Preparation Duplicates Relative to Original Chemex Gold Assays
83
Figure 8-2:
Hunter Analyses of Preparation Duplicates Relative to Original Chemex Gold Assays
84
Figure 8-3:
Chemex Analyses of RC Field Duplicates Relative to Original Chemex Gold Assays
85
Figure 8-4:
Shasta Check Analyses Relative to Original Chemex Gold Assays
86
Figure 8-5:
RMGC Check Analyses Relative to Original RMGC Gold Assays
87
Figure 8-6:
RMGC Core Duplicate “B” Relative to RMGC “A” Gold Assays
88
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Figure 8-7:
AAL Preparation Duplicate Analyses Relative to AAL Original Gold Assays
89
Figure 8-8:
Chart of ALS Analyses of CRM CDN-GS-3J
91
Figure 8-9:
Chart of ALS Analyses of Coarse Blanks – Calico
92
Figure 8-10:
AAL Pulp Checks of ALS Original Gold Analyses
94
Figure 8-11:
Chart of ALS Analyses of Coarse Blanks – Paramount
95
Figure 8-12:
ALS Gold Analyses Preparation Duplicates – Paramount
96
Figure 8-13:
Core Duplicates Relative to Original Gold Assays – Paramount
97
Figure 8-14:
Second Set of Paramount Core Duplicates Relative to Original Gold Assays
98
Figure 8-15:
Paramount RC Duplicates Relative to Original Gold Analyses
99
Figure 10-1:
Gold Leach Extraction Rate
114
Figure 10-2:
Gold Leach Extraction Rate for Grade Variability Samples
115
Figure 10-3:
Silver Leach Extraction Rate for Grade Variability Samples
116
Figure 10-4:
Drill Hole and Interval Locations for Samples in the SGS 2018 and 2020 and McClelland Programs
119
Figure 10-5:
Relationship Between Leach Feed and Residue Grades for Gold
123
Figure 10-6:
Relationship Between Leach Feed and Residue Grades for Silver
123
Figure 10-7:
Predicted versus Measured Recovery for Gold
124
Figure 10-8:
Predicted versus Measured Recovery for Silver
125
Figure 11-1:
Cross-section 3050 Showing Geology and Gold Domains
133
Figure 11-2:
Cross-section 3050 Showing Geology and Silver Domains
134
Figure 11-3:
Cross-section 3250 Showing Geology and Gold Domains
135
Figure 11-4:
Cross-section 3250 Showing Geology and Silver Domains
136
Figure 11-5:
Cross-section 3050 Showing Block-Model Gold Grades
146
Figure 11-6:
Cross-section 3050 Showing Block-Model Silver Grades
147
Figure 11-7:
Cross-section 3250 Showing Block-Model Gold Grades
148
Figure 11-8:
Cross-section 3250 Showing Block-Model Silver Grades
149
Figure 12-1:
Monthly Average Gold Price, $/oz
155
Figure 12-2:
Mine Production Design of Level 3210, Plan View
158
Figure 12-3:
Ore and Waste Designation
160
Figure 13-1:
Grassy Mountain Mine Cross-section Looking North
161
Figure 13-2:
Proposed Grassy Mountain Mine Plan (plan view)
162
Figure 13-3:
Drift Profiles
163
Figure 13-4:
Production Drift Layout (Section Looking East)
164
Figure 13-5:
Detailed level Sequence for a Typical Level
165
Figure 13-6:
Mining Lifts
166
Figure 13-7:
Golder Rock Mass Rating (all 2016–2017 core)
170
Figure 13-8:
RMR 76 Histogram from 27 Drill Holes
171
Figure 13-9:
Examples of Three Geotechnical Rock Classes
173
Figure 13-10:
GM19-37 Core Trays (89.5 to 105.5 ft.) – High Variability in Geotechnical Conditions
174
Figure 13-11:
Iso-Probability Contours for Stable Cases
180
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Figure 13-12:
Iso-probability contours for failure cases (Mawdesley, 2001)
181
Figure 13-13:
Modeling Results for Decline Ramp; a) Major Principal Stress, S1; b) Minor Principal Stress, S3; c) Strength Factor, SF; d) Displacements
183
Figure 13-14:
Modeling Results for Topcut A; a) Major Principal Stress, S1; b) Minor Principal Stress, S3; c) Strength Factor, SF; d) Displacements
184
Figure 13-15:
Modeling Results for Undercut B; a) Major Principal Stress, S1; b) Minor Principal Stress, S3; c) Strength Factor, SF; d) Displacements
185
Figure 13-16:
Modeling Results for Undercut C; a) Major Principal Stress, S1; b) Minor Principal Stress, S3; c) Strength Factor, SF; d) Displacements
186
Figure 13-17:
Three-Dimensional Model of Finite Difference
187
Figure 13-18:
Level Access Layout (Looking North)
193
Figure 13-19:
Station Design
194
Figure 13-20:
Sandvik DD422i
196
Figure 13-21:
GetMan Proshot Concrete Sprayer
197
Figure 13-22:
GetMan ProMix 6
198
Figure 13-23:
3360 Shotcrete Thickness (units in inches)
199
Figure 13-24:
Sandvik LH307 Underground Loader
201
Figure 13-25:
Sandvik TH320 trucks
201
Figure 13-26:
Waste Haulage by Year
203
Figure 13-27:
Mixing, Casting and Curing Process
205
Figure 13-28:
UCS Results vs Curing Time
206
Figure 13-29:
Simem WB100 Backfill Plant
207
Figure 13-30:
Ventilation Network (isometric view looking west)
209
Figure 13-31:
Ventilation Network (Section View Looking Northwest)
210
Figure 13-32:
Surface Ventilation Fan (Section View)
210
Figure 13-33:
Design of Vent Raises
211
Figure 13-34:
Mine Load Center (1000 kVA)
213
Figure 13-35:
Mobile Refuge Station
214
Figure 13-36:
Proposed Mine Production Schedule (tons by period)
218
Figure 13-37:
Mine Production Schedule (ounces by period)
218
Figure 14-1:
Simplified Overall Flowsheet
222
Figure 14-2:
Proposed Plant Site Layout
223
Figure 14-3:
Projected Daily Plant Water Balance, at average LOM throughput
232
Figure 15-1:
Proposed Infrastructure Layout Plan
234
Figure 15-2:
Overall TSF Layout
237
Figure 15-3:
TSF Main (North) Embankment Cross-section
241
Figure 15-4:
Site-wide Hydrologic Catchment Areas
245
Figure 15-5:
Process Plant Stormwater Contact and Non-contact Catchment Areas
247
Figure 18-1:
Proposed Mine Organizational Chart
287
Figure 19-1:
Forecast Project Post-Tax Unlevered, Undiscounted Free Cash Flow ($ M)
294
Figure 19-2:
Pre-Tax NPV & IRR Sensitivity Results
299
Figure 19-3:
Post-Tax NPV & IRR Sensitivity Results
299
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1
EXECUTIVE SUMMARY
1.1
Introduction
Ausenco Engineering Canada ULC (Ausenco), Geotechnical Mine Solutions Inc. (GMS), RESPEC Company LLC (RESPEC), SLR International Corporation (SLR) and WSP USA
Inc. (WSP) compiled an updated technical report summary (the Report) on a feasibility study (the FS) completed on the Grassy Mountain Project (the Project) for Paramount Gold Nevada Corp. (Paramount), located in Oregon, USA.
This Report updates the previously filed technical report summary entitled, “Grassy Mountain Project: S-K 1300 Technical Report Summary on
Feasibility Study, Oregon, United States” with an effective date of June 30, 2022. Updates include the mineral resource estimate, mineral reserve estimate, capital costs, operating costs and the economic analysis.
Paramount holds its Project interest through an indirectly wholly owned subsidiary, Calico Resources USA Corp. (Calico).
1.1.1
Terms of Reference
Measurement units used in this Report are generally U.S. customary; however, certain data, such as analytical and metallurgical testwork units may be presented
in metric units. Unless otherwise stated, all monetary amounts are in United States dollars (USD).
Mineral resources and mineral reserves are reported
using the definitions in subpart 229.1300 – Disclosure by Registrants Engaged in Mining Operations in Regulations (S-K 1300).
1.1.2
Effective Dates
The Report has a number of effective dates as follows:
•
Mineral Resource estimates: February 28, 2026
•
Mineral Reserve estimate: May 15, 2026
•
Date of financial analysis that supports the Mineral Reserves: May 27, 2026.
The overall effective date of this Report is the effective date of the financial analysis, which is May 27, 2026.
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1.2
Property Description
The Grassy Mountain deposit is situated near the western edge of the Snake River Plain in eastern Oregon, 20 miles (mi) south of the town of Vale, Oregon and
about 70 miles west of the city of Boise, Idaho. Support services for mining and other resource sector industries in the region would primarily be provided by these communities. The closest major airport is at Boise, which is a commercial airport
served by all major U.S. airlines.
Access to the main Grassy Mountain deposit within the Grassy Mountain claims group is provided by Twin Springs Road, a
seasonally maintained unpaved road that originates at Russell Road, a paved two-lane county road that joins with U.S. Highway 20 approximately four miles west of Vale.
1.3
Mineral Tenure, Surface Rights, Water Rights, Royalties and Agreements
The Grassy Mountain Project is located within Malheur County and is comprised of the Grassy Mountain claims group, which covers 9,300 acres. The mineral tenure
holdings comprise 436 unpatented lode and mill site claims, three patented claims, and a land lease for 28 unpatented lode mining claims. Claims are held in the name of Paramount’s U.S. subsidiary, Calico.
Patented claims were individually surveyed at the time of location. Unpatented claim and fee land boundaries were established initially by handheld global
positioning system (GPS) units and were formally surveyed in 2011.
Calico acquired all right, title and interest in the Project, including all existing
exploration and water rights pertaining to the Grassy Mountain Project, pursuant to a “Deed and Assignment of Mining Properties” between Seabridge Gold Inc. (Seabridge Gold), Seabridge Gold Corporation (collectively Seabridge) and Calico
dated February 5, 2013. Paramount acquired Calico in July 2016 and amalgamated the two companies.
Paramount’s 100% ownership of the Grassy
Mountain project is subject to underlying agreements and royalties.
Seabridge Gold is entitled to a 10% net profits interest (NPI) royalty. Pursuant to
the Deed of Royalties, within 30 days following the day that Calico made a production decision and construction financing was secured, Seabridge may elect to cause Calico to purchase the 10% NPI for 10 million CAD. Otherwise Seabridge will
retain the 10% NPI. Seabridge, at the Report effective date, is the second largest Paramount shareholder and has indicated that it will convert its NPI into equity in Paramount, thus the Seabridge NPI has not been included in the FS.
Sherry and Yates, Inc. (Sherry and Yates) are entitled to a 1.5% royalty of the gross proceeds on any production from three patented and 37 unpatented mining
claims, and a surrounding 1⁄2 mile area of interest. The royalty is not subject to any advance-royalty payments. The royalty covers the area of the Grassy Mountain
deposit.
Cryla LLC (Cryla) leased 28 unpatented lode mining claims located west of Grassy Mountain to Calico in 2018. Calico is required to make an
annual lease payment of $60,000 for the ongoing 25-year lease agreement. Calico is eligible to acquire the Property for $560,000 plus $3/oz of gold reserves, as defined by a pre-feasibility or higher confidence-level study. Cryla is entitled to a 2%
net smelter return (NSR) if the gold price is ≤$1,500/oz and a 4% NSR if the gold price >$1,500/oz. Calico is entitled to reduce the NSR to 1% by paying Cryla $800,000 under any circumstances. No Mineral Resources or Mineral Reserves are
estimated on the Cryla claims.
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Paramount holds three patented claims over the Grassy Mountain deposit, which provides surface rights for
that area. The surrounding surface rights associated with the proposed locations of the Project surface facilities belong to the Federal government and are managed by the Vale District Bureau of Land Management (BLM) office.
Paramount holds a water right granted by the Oregon Water Resources Department to Calico. The water right was issued on April 5, 1990, through State of
Oregon Water Rights Application G-11847 and Permit G-10994. Use is limited to not more than 2.0 ft3/s (897.6 gpm) measured at the well. On October 16, 2019, the State of Oregon issued a new
Permit to Appropriate the Public Waters (G-18337) that replaces the previous permit and includes the requested modifications. This permit does not change the 2.0 ft3/s of water use allowed.
1.4
Accessibility, Climate, Local Resources, Infrastructure and Physiography
The climate is semi-arid and continental-interior in type. Average annual precipitation is approximately about nine inches, roughly half of which falls as snow
between November and March. Mining activities are expected to be conducted year-round.
The Project area is in the semi-arid high desert plateau region of
eastern Oregon. Elevations range from 3,330 to 4,300 ft above mean sea level at the main Grassy Mountain claims group area. The terrain is mainly open steppe with mesas, broad valleys, and gently rolling hills to steeper uplands.
Vegetation across the entire area consists of sagebrush, weeds, and desert grasses tolerant of semi-arid conditions.
As of the effective date of this Report, groundwater monitoring wells and unpaved access and drilling roads are the only existing infrastructure within the
Grassy Mountain Project area. The infrastructure required for the proposed operation is detailed in Section 15.
The nearest community to the Project
is Vale, which has a population of approximately 1,700. Vale provides fuel, restaurants, lodging, groceries, hardware supplies, and equipment-repair shops are available in Vale. Other logistical support is available in the nearby communities of
Nyssa and Ontario, both of which are located within 30 mi of the Project. The metropolitan area of Boise, Idaho, is approximately a 90-minute drive from the Project site. Mining personnel, equipment suppliers, engineering expertise, and
telecommunications services are all expected to be readily available within the region.
1.5
History
Companies and individuals involved in exploration prior to Paramount’s Project interest include prospectors Richard “Dick” Sherry and Eugene
“Skip” Yates (Sherry and Yates), Atlas Precious Metals (Atlas), Golden Predator Mines U.S. Inc., Newmont Exploration Ltd (Newmont), Tombstone Exploration Company Ltd. (Tombstone), Seabridge Gold, and Calico BC. Work completed included
reconnaissance, geological mapping, geochemical sampling (soil, float, rock chip), geophysical surveys [airborne magnetic and radiometric, ground-based gravity, gradient array (IP/resistivity) controlled-source audio-frequency magnetotelluric
(CSAMT)], core and reverse circulation (RC) drilling, and Mineral Resource estimation. This work defined the Grassy Mountain deposit, on which a feasibility study was completed in 1990 by Atlas assuming a combined heap leach/milling operation and
open pit mining methods.
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1.6
Geological Setting, Mineralization and Deposit
The geological setting, hydrothermal alteration, styles of gold-silver mineralization, and close spatial and timing association with silica sinter deposition,
indicate that Grassy Mountain is an example of the hot-springs subtype of low-sulfidation, epithermal precious-metals deposits.
The Miocene-age Lake
Owyhee volcanic field is the regional host to a number of recognized epithermal hot-spring precious-metal deposits, of which the Grassy Mountain deposit is the largest. Initial large-volume peralkaline and subalkaline caldera volcanism was followed
by subsidence, forming extensive grabens. These were filled by small-volume metaluminous high-silica rhyolite domes and flows, small-volume basalt flows and mafic vent complexes, and co-eval lacustrine and fluvial sediments.
The Grassy Mountain deposit extends for about 1,900 ft along a N60°E to N70°E axis, as much as 2,700 ft in a northwest–southeast direction, and
as much as 1,240 ft vertically.
The deposit is hosted in units of the Miocene Grassy Mountain Formation, consisting of interbedded conglomerate,
sandstone, siltstone, tuffaceous siltstone, mudstone, and several silica sinter deposits. It is situated within a zone of complex extensional block faulting and rotation, dominated by N30°W to N10°E striking normal faults (graben faults). A
set of orthogonal, N70°E-striking high-angle faults of minor displacement are inferred to link the graben faults.
Silicification (silica sinter,
pervasive silica flooding, and as cross-cutting chalcedonic veins, veinlets, and stockworks) is the principal hydrothermal alteration type associated with gold–silver mineralization. In some parts of the deposit, particularly within arkose and
sandy conglomerate units, silicification can be accompanied by potassic alteration in the form of adularia flooding.
Mineralization is developed largely
within the silicic and potassic alteration zones. Three distinct and overlapping types of gold–silver mineralization are recognized within the central core of the deposit. These are gold-bearing chalcedonic quartz ± adularia veins,
disseminated mineralization in silicified siltstone and arkose, and gold and silver in bodies of clay matrix breccia. Gold mostly occurs as electrum along the vein margins or within microscopic voids Lower-grade mineralization envelopes the
higher-grade core and, further from the core, extends outwards as stratiform, mineralized lenses parallel to bedding.
1.7
Exploration
Since acquiring its Project interest in 2016, Paramount has conducted an exploration review of the available Project data, helicopter-borne aeromagnetic and
radiometric and CSAMT ground geophysical surveys, drilling, Mineral Resource and Mineral Reserve estimation, baseline environmental studies, and mining studies. A feasibility study was completed in 2020, with further update completed in 2022 and in
2026 (the work covered in this report).
A number of prospects were located during the exploration programs. Of these, the Crabgrass, Bluegrass, North
Bluegrass, Ryegrass and Dennis’ Folly areas in the Grassy Mountain claims block were recommended for surface work with the goal of defining further exploration drill targets.
No production is known from the Project area.
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1.8
Sample Preparation, Analyses and Security
The database includes a total of 264,112 ft drilled by four historical operators (Atlas, Tombstone, Newmont, Calico BC), from 1987 through 2012, in 442 drill
holes. Paramount drilled 34 holes for a total of 25,511 ft in 2016–2019 to bring the Project total to 476 holes and 289,623 ft drilled. Approximately 77% of the footage drilled was at, and adjacent to, the Grassy Mountain deposit area,
although nearly 43% of the holes were drilled at outlying prospects, as well as for water wells.
The bulk of the drill holes in the Grassy Mountain
deposit area was drilled using RC, accounting for 77% of the footage drilled. Holes drilled using core methods account for about 12% of the footage drilled in the deposit area, and holes drilled with RC pre-collars and core tails account for about
11%. A total of 256 of the drill holes in the Grassy Mountain deposit area support Mineral Resource estimation, including 34 Paramount drill holes and 252 historical drill holes.
During the Calico BC and Paramount drill programs, logging recorded lithological, alteration, mineralization, and structural information, including the angle
of intersection of faults with the core, fault lineations, fractures, veins, and bedding. Up until Calico BC’s involvement in the Project in 2011, the Project coordinates were based on a local grid established by Atlas. All Calico and
subsequent drill-hole collar surveys were collected directly in UTM coordinates. Where information is recorded, drill collars were located using total station, Trimble, survey-grade GPS, and Topcon Hiper V GPS Receivers instrumentation. Down hole
surveys were performed, where recorded, using Eastman, REFLEX EZ-Track, gyroscopic, Goodrich-Humphrey surface-recording gyroscopic and Goodrich surface-recording gyroscopic instruments.
Wet RC cuttings were split using a variable or rotary wet-cone splitter positioned below the cyclone on the RC rigs. Dry cuttings were split under the cyclone
with a Jones splitter. During the Calico BC and Paramount drill programs, core sample lengths generally did not exceed 5 ft and, where possible, correlated to the 5 ft drilling runs. Competent core was cut using either a hydraulic splitter or a
diamond blade core saw. During the Newmont program material too fine to be sawed was carefully swept out of the core boxes for each sample interval, split into halves using a Jones splitter, and recombined with the half-core to be sent for assaying.
During the Calico BC and Paramount drill programs, core that was intensely broken or very soft was split in half using a small scoop or putty knife.
Laboratories used for sample preparation and analysis include Chemex Analytical Laboratories (Chemex; Boise and Vancouver), Rocky Mountain Geochemical
Corporation (RMCG; Salt Lake City); American Assay Laboratory (AAL; Reno); and ALS Minerals (ALS; Reno). All laboratories were independent. Accreditations for Chemex, RMCG and AAL at the time used are not known. ALS holds ISO 9001:2008 accreditation
for quality management and ISO/IEC17025:2005 accreditation for selected analytical techniques.
Laboratories used for check analysis included Chemex, AAL,
Cone Geochemical Laboratories (Cone; Denver), and Hunter Mining Laboratories (Hunter; Reno). Accreditations at the time are not known. The laboratories were independent.
Sample preparation and analytical methods included:
•
Chemex: dried, crushed to minus 1/8 inch, pulverized to 95% at minus 100 mesh. Gold and silver assays using 30 g
aliquots and fire assay fusion, primarily with an atomic absorption (AA) finish.
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•
RMCG: dried, crushed to minus 10 mesh, pulverized to minus 48 mesh and repulverized to nominal, minus
150 mesh. Fire assayed for gold with a gravimetric and AA finishes. Screen-fire assays completed where gold values were >0.20 oz Au/ton.
•
AAL: dried, crushed to 8–10 mesh, pulverized to 90% -150 mesh. Gold assays via fire assaying with an AA
finish. Silver via method D210, which included aqua-regia digestion.
•
ALS: dried, crushed to 75% at <6 mm, pulverized to 85% at <200 mesh (75 µm). Gold assays via fire
assaying with an AA finish. A separate five-gram aliquot was used for inductively coupled plasma atomic-emission spectrometric (ICP-AES) determination of silver and 32 major, minor, and trace elements following a four-acid digestion. Gold overlimits
re-assayed using fire assay with gravimetric finish. Silver overlimits re-assayed using 10-g aliquot with a four-acid digestion for silver and an AA finish or 30-g fire assay with a gravimetric finish.
The available Atlas quality assurance and quality control (QA/QC) data of consequence (the preparation and field duplicates) suggest that the original gold
assay results may be overstated to some extent. However, the average grade of the duplicate dataset is much higher than the average grade of the Grassy Mountain deposit and repeat analyses of only the higher-grade portion of a deposit with free gold
can yield lower results than original assays. Without further data, it is impossible to know whether there is a high bias in the Atlas results, although a comparison of resources with and without Paramount drill data suggests there are no material
issues with the Atlas data. The Newmont QA/QC data do not identify any issues, while it is possible that the Tombstone gold values are slightly understated. No issues were revealed by the Paramount certified reference material (CRM), blank, and
preparation-duplicate data. The core-duplicate data suggest that the Paramount gold assays of core, particularly at higher grades, may be understated to some degree. These data also serve to emphasize the importance of careful sampling and splitting
of core-box fines. The variability evidenced by the duplicate data from all operators at Grassy Mountain does not exceed normal bounds, especially considering the presence of visible gold.
1.9
Data Verification
The Project drill-hole database was subjected to data verification and corrections prior to the initiation of the 2016–2017 drilling program. This
verified database was periodically updated by RESPEC with information acquired during Paramount’s various drilling programs.
As part of the
2016–2017 drilling program, all prior drill-hole collars that could be identified in the field were re-surveyed. The collar locations of 82 Atlas drill holes, six Newmont drill holes, four Tombstone drill holes, and nine Calico drill holes
were surveyed. RESPEC was provided the original digital file produced by the survey contractor, and RESPEC used this file to compare the new survey locations with those in the existing database. The scale of the discrepancies in the drill hole
locations is not considered to be material due to the nature of the Grassy Mountain mineralization and the 10 x 10 x 10-ft block size used in modelling.
RESPEC compared the total depths of 47 historical drill holes against historical records and found no material errors.
Down-hole survey records from selected drill holes from the historical drilling were examined. No material errors were noted; errors that were identified were
corrected in the database. The drill-collar azimuths and dips for 40 drill holes were checked against historical records and no discrepancies were found.
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The database assay values for selected intervals from historical drill holes were checked against historical
documents. No material discrepancies were found; errors that were identified were corrected in the database.
RESPEC personnel conducted a number of site
visits that included inspection of outcrop, visiting core and RC drill sites with ongoing sampling and logging, review of numerous mineralized intervals in drill core, review of all Project procedures related to logging, sampling, and data capture,
and on-site evaluation of several target areas throughout the Project area.
The RESPEC QPs verified that the Grassy Mountain Project data are acceptable
as used in this Report, most significantly to support the estimation and classification of the Mineral Resources and Reserves.
1.10
Mineral Processing and Metallurgical Testwork
In support of the FS, historical work conducted by Hazen Research Inc., Golden Sunlight, Newmont and Resource Development Inc. (RDI) was reviewed. The degree
to which historical metallurgical samples are representative of the Grassy Mountain deposit is not known with certainty, but there is no evidence that the historical samples were not representative. Early historical work listed above is viewed as
indicative or informative only since the qualified person (QP) was not able to reconcile the test results to drill hole locations and depth to confirm that these drill holes represent the ore in the current mine plan.
In the 2018 PFS metallurgical testing program, Paramount completed head grade analyses, comminution tests (JK drop-weight tests), gravity and leach tests, and
rheology and solid/liquid separation tests on CIL tailings samples. This was supplemented in 2019 and 2020 FS metallurgical testing programs with chemical and mineralogical analysis, Bond ball and rod mill work index tests, and testwork on leaching,
oxygen demand, and cyanide destruction testing.
Tests were performed on mineralization that is considered to be representative of the material that will
be sent to the plant. Composite samples representing major lithologies, Year 1 and Year 2 production composites and a range of head grades aligned with the minimum and maximum values expected in the plant feed in the initial two years of production
were tested in the 2019 and 2020 FS metallurgical testing programs.
The grade variability composite samples calculated gold and silver grades ranged from
0.104–0.383 oz/ton Au (3.57–13.13 g/t Au) and 0.149–0.628 oz/ton Ag (5.1–21.5 g/t Ag).
Comminution testing showed that all the
samples tested are considered hard to very hard, with Bond ball mill work indices ranging from 20.8 to 32.0 kWh/ton.
Bottle roll and agitated batch leach
tests showed that the samples were highly responsive to recovery by cyanidation at a grind size of 80% passing 150 mesh (106 µm) or finer, with leach recoveries ranging from 82.1–97.5% for gold and 59.0–84.6%for silver,
dependent on leach feed grade.
Overall plant recoveries for gold are predicted to range from 89.5–94.9% for head grades of 0.096–0.58 oz/ton
Au (3.3–17.4 g/t Au) over the life of mine (LOM). Overall plant recoveries for silver are predicted to range from 62.7–80.4% for head grades of 0.161–0.523 oz/ton Ag (5.5–17.9 g/t Ag) over the LOM.
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Cyanide destruction tests achieved <0.2 mg/L
CNWAD, which is well within the maximum legislated value in Oregon of 30 mg/L.
Mercury
grades were in the range of 0.054–0.077 oz/ton (1.86–2.64 g/t) in the leach feed, and the concentration of mercury in solution after leaching ranged from 0.08–0.26 mg/L. A retort and gas collection and scrubbing system was
incorporated into the plant design to manage and control mercury in the process. Arsenic is present in the feed at concentrations ranging between 3.47–5.34 oz/ton (119–183 g/t) and is not expected to be problematic in
processing. No other elements that may cause issues in the process plant or concerns with product marketability were noted.
1.11
Mineral Resource Estimate
Paramount supplied RESPEC with a set of detailed cross-sectional lithological and structural interpretations that covers most of the extent of the Grassy
Mountain deposit. These cross-sections served as the base for RESPEC’s modeling of the gold and silver mineralization. During that process, RESPEC added some additional structures and made other minor modifications to Paramount’s
structural interpretations.
The density values RESPEC used in the estimation were based on water-displacement method measurements performed by Atlas and
Paramount. The density associated with the Grassy Mountain mineralization is consistent, and unmineralized rocks are distinctly less dense – likely a reflection of the strong silicification associated with all grades of mineralization compared
to weak or absent silicification in unmineralized rocks. RESPEC used tonnage factors of 13.5 ft3/ton for mineralized material and
14.8 ft3/ton for non-mineralized material.
The Grassy Mountain gold-silver deposit is hosted by
arkoses, siltstones, mudstones, and sinters of the Grassy Mountain Formation. From the assay data, RESPEC identified three gold-grade populations and three silver grade populations. The high-grade domains are comprised of a central core zone
characterized by gold grades greater than 0.03 oz/ton Au and silver grades over 0.15 oz/ton Ag. Sub-vertical structures and sub-horizontal stratigraphy control the high-grade central core mineralization and domains within a broad envelope of
primarily stratigraphically controlled low-grade mineralization. The highest-grade gold (>~0.25 oz Au/ton) and silver (>~0.4 oz/ton Ag) population strongly correlates with the presence of thin, often
banded, quartz–chalcedony veins and veinlets and/or breccias. However, the highest-grade mineralization does not have sufficient continuity for confident domain modeling. Therefore, RESPEC did not explicitly model it.
RESPEC determined assay caps by inspecting distribution plots of the coded assays by domain and identifying high-grade outliers appropriate for capping, then
capped gold at values ranging from 0.09–10 oz/ton Au and silver at values ranging from 0.12–7 oz/ton Ag.
RESPEC used level-plan gold and
silver mineral-domain polygons to code volume partial percentages into a three-dimensional block model with a model bearing of 340° that consisted of 5-ft x 10-ft x 10-ft blocks (model x, y, z). RESPEC also coded the block model using a digital
topographic surface.
RESPEC coded two estimation areas into the block model. In one, the stratigraphically-controlled mineralization dips shallowly at
about -15° and encompasses most of the in the Grassy Mountain deposit. The second estimation area is located in the west–southwestern portion of the deposit where the dips of the stratigraphic units steepen to approximately -20°.
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Using length-weighted composites, RESPEC completed the grade interpolation in three passes in two estimation
areas. In the outer estimation area, low-grade gold and silver domains, as well as areas outside modeled domains, were entirely estimated using search ellipses that reflect stratigraphic orientations. The high-grade gold and silver domains in
estimation area two exhibit both sub-horizontal (stratigraphic) and high-angle (structural) controls. The first pass in the high-grade domain reflects high-angle structural controls. The second estimation pass applied a search ellipse reflective of
stratigraphic control but did not overwrite grades estimated during pass 1. The third and final estimation pass was an isotropic pass that RESPEC used to estimate grades into blocks that had not been estimated by the first two passes.
The gold and silver high-grade domains captured multiple populations, which mandated restrictions on the search distances. The multiple populations lack
sufficient continuity to be explicitly modeled as separate domains. RESPEC also used search restrictions because initial estimation runs without the restrictions resulted in unrealistic volumes and distribution of estimated high grades in the block
model.
RESPEC interpolated gold and silver grades using inverse-distance to the third power (ID3), ordinary-kriging (OK), and nearest-neighbor (NN)
methods and chose to report the estimate of mineral resources using the ID3 interpolations because the ID3 results more closely represented the geology and distribution of drill-hole assay data than those obtained by OK. RESPEC performed estimation
passes independently for each mineral domain and coupled the estimated grades with the partial percentages of the mineral domains and the outside-domain volumes to enable the calculation of weight-averaged gold and silver grades for each block.
Therefore, this methodology fully block-dilutes the final resource grades and their associated resource tonnages.
The Grassy Mountain deposit has the
potential to be mined by open-pit methods. While Grassy Mountain’s mineral reserves are estimated on the basis of a proposed underground-mining scenario, the mineral reserves represent only a small subset of the entire gold-silver deposit. The
deposit’s mineral resources are reported to reflect potential open-pit extraction and milling as the primary scenario, with a secondary scenario of potential underground mining of a very small quantity of material lying outside of the lower
portions of the open pit.
RESPEC used a conceptual pit shell to constrain the Grassy Mountain deposit’s mineral resources, with the added
constraint of a gold equivalent (AuEq) cut-off grade of 0.008 oz/ton AuEq applied to all model blocks lying within the optimized pit and calculated the oz/ton AuEq grade of each model block as follows:
oz/ton AuEq = oz/ton Au + (oz/ton Ag ÷ 129).
The factor of 129 reflects metal prices of $3,100/oz gold and $34/oz silver, as well as recoveries of 80% for gold and 60% for silver.
RESEPC estimated mineral resources potentially amenable to underground mining methods by applying a cut-off of 0.070 oz/ton AuEq to blocks lying immediately
outside the optimized pit.
Both resource estimates are based on a 5,000 tons/day processing rate, with processing assumed to consist of crushing and
milling followed by carbon-in-leach recovery.
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1.12
Mineral Resource Statement
Mineral resources are reported to be inclusive of the mineral resources that have been converted to mineral reserves, using the mineral resource definitions
set out in S-K 1300. Mineral resources that are not mineral reserves do not have demonstrated economic viability. RESPEC is the qualified person firm responsible for the mineral resource estimate. The mineral resource estimates are presented in
Table 1-1.
Table 1-1: Grassy Mountain Mineral Resource Estimate
Inclusive of Mineral Reserves – Effective date: February 28, 2026
Amount
(tons)
Grade/qualities
(oz/ton Au)
Grade/qualities
(oz/ton Ag)
Cut-off grades (oz/
ton Au)
Metallurgical
Recovery
Measured Mineral Resource
33,999,000
0.016
0.063
Inside pit: 0.008
Au – 80%
Indicated Mineral Resource
23,795,000
0.034
0.098
Outside pit: 0.070
Ag—60%
Measured + Indicated Mineral Resource
57,794,000
0.023
0.077
Inside pit: 0.008
Au – 80%
Inferred Mineral Resource
3,779,000
0.019
0.056
Outside pit: 0.070
Au – 80%
Ag—60%
Notes:
•
RESEPEC is the qualified person firm responsible for the mineral resources estimate.
•
Mineral resources are comprised of all model blocks at a 0.008 oz/ton AuEq cut-off that lie within an optimized
pit plus blocks at a 0.070 oz/ton AuEq cut-off that lie outside the optimized pit.
•
oz/ton AuEq (gold equivalent grade) = oz/ton Au + (oz/ton Ag ÷ 129).
•
Mineral resources summarized in the table immediately above are reported inclusive of the mineral resources
converted to mineral reserves. Mineral resources that are not mineral reserves do not have demonstrated economic viability.
•
Mineral resources potentially amenable to open pit mining methods are reported using a gold price of $3,100/oz, a
silver price of $34/oz, a throughput rate of 5,000 tons/day, assumed metallurgical recoveries of 80% for Au and 60% for Ag, mining costs of $3.14/ton mined, processing costs of $16.33/ton processed, general and administrative costs of $2.79/ton
processed, and refining costs of $5.00/oz Au and $0.50/oz Ag produced. Mineral resources potentially amenable to underground mining methods are reported using a gold price of $3,100/oz, a silver price of $34/oz, a throughput rate of 5,000 tons/day,
assumed metallurgical recoveries of 92.8% gold equivalent, mining costs of $141.77/ton mined, processing costs of $39.09/ton processed, general and administrative costs of $20.15/ton processed, and refining costs of $5.00/oz gold equivalent
produced.
•
The effective date of the mineral resources estimate is February 28, 2026, and the effective date of the
database on which the Mineral Resources estimate is based is May 1, 2018.
•
Rounding may result in apparent discrepancies between tons, grade, and contained metal content.
Inclusive of mineral reserves, the mineral resources contain 540,000 oz of gold and 2,142,000 oz of silver classified as measured,
817,000 oz of gold and 2,325,000 oz of silver classified as indicated, and 73,000 oz of gold and 210,000 oz of silver classified as inferred. Mineral resources that are not mineral reserves do not have demonstrated economic viability.
1.13
Mineral Reserve Estimate
An underground mining scenario is assumed using mechanized cut-and-fill methods, which, following ramp-up, will produce 1,200–1,400 tons/day, four days a
week. This mining rate will provide sufficient material for the 750 ton/day mill and processing plant to operate at full capacity for seven days a week.
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The Proven and Probable reserves for Grassy Mountain have been estimated by first calculating an economic NSR
cut-off for mining underground stopes, then using the NSR cut-off to design stope shapes centered on Measured and Indicated Mineral Resource blocks with the mining revenue greater than or equal to the NSR cut-off. All Inferred material was
considered to be waste with no value or metal content. Internal and external dilution and mining recoveries (ore loss) were estimated and applied as modifying factors based on the total tonnage of material inside of the final designs.
The economic cut-off grade used for stope design is based on initial economic parameters shown in table below.
Table 1-2: Cut-off Grade Input Parameters for Gold Metal
Name
Quantity
Unit
UG Mining costs
141.18
$/ton processed
Surface Rehandle
0.22
$/ton processed
Process Costs
39.09
$/ton processed
General and administrative (G&A) Costs
20.15
$/ton processed
Total Operating Costs
200.64
$/ton processed
Refining Cost
6.00
$/oz processed
NSR Royalty
1.5%
percent
Gold Metal Recovery
92.8%
percent
Gold Selling Price
2,750
$/oz Au
Calculated Cutoff Grade
0.080
oz Au/ton
Mineral Reserve Cutoff Grade Used
0.080
oz Au/ton
NSR Economic Cutoff
201.00
$/ton processed
The calculated gold cut-off grade is 0.08 oz/ton Au. The economic stope NSR cutoff was used in the stope optimization to
identify the Measured and Indicated blocks available for consideration to be converted to Mineral Reserves. Measured and Indicated resource blocks with NSR value less than the economic stope NSR cut-off, as well as all Inferred resource blocks
irrespective of grade, were considered as waste and applied to internal dilution.
Each stope block was queried against the resource block model to
determine the tonnages and grades within the stope shapes. Stopes with an average measured or indicated gold grade equal to and above the economic NSR cut-off were selected to be included in the mine plan and Mineral Reserves estimate. Some isolated
stopes above the cut-off grade threshold were eliminated from consideration because the development to extract them would cost more than the economic return. Dilution and recovery were not considered during the stope optimization. The dilution and
recovery were applied as modifying factors later in the process.
A modifying factor of 8% was used for calculating external dilution tons. All Inferred
resource blocks or partial blocks within the stopes and all unclassified material within the stopes is considered internal dilution. The tons were accounted for with zero grade.
Mining recovery is estimated to be 97% based on an assumed ore loss of 3%. This is considered appropriate for the highly selective mechanized cut-and-fill
mining method selected for the Grassy Mountain deposit and it is based on similar operations in disseminated ore bodies.
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1.14
Mineral Reserve Statement
The reference point for the estimated Mineral Reserves is the crusher. The Mineral Reserves estimated for the Grassy Mountain Project are provided in Table 1-3 and have an effective date of May 15, 2026. The Qualified Person firm for the Mineral Reserve estimate is RESPEC.
Table 1-3: Gold and Silver Mineral Reserve Estimates
(US Imperial units)
tons
(‘000s)
Grade
(oz/ton Au)
Gold
(‘000 oz)
Grade
(oz/ton Ag)
Silver
(‘000 oz)
Proven mineral reserves
299
0.167
50
0.256
77
Probable mineral reserves
1,908
0.186
355
0.287
548
Total Proven and Probable reserves
2,207
0.184
405
0.283
625
Notes:
•
Mineral reserves have an effective date of May 15, 2026.
•
Mineral Reserves are reported inside stope designs assuming drift-and-fill mining methods, and an economic net
smelter return cutoff grade of $200.64 per ore ton processed. The economic cut-off grade estimate uses a gold price of $2,750/oz, mining costs of $141.18/ton processed, surface re-handle costs of $0.22/ton processed, process costs of $39.09/ton
processed, general and administrative costs of $20.15/ton processed, and refining costs of $6/oz Au recovered.
•
Metallurgical recovery utilizes the leach recovery schedule discussed in section 10 of the Technical Report
Summary
•
Mineralization that was either not classified or was assigned to Inferred Mineral Resources was set to waste.
•
A 1.5% NSR royalty is payable.
•
Rounding may result in apparent discrepancies between tons, grade and contained metal content.
1.15
Mining Methods
1.15.1
Overview
The Grassy Mountain mine will be an underground operation accessed via one decline and a system of internal ramps. One set of stacked ventilation raises is
included in the design to be used for ventilation and secondary egress. The underhand mechanized cut-and fill mining method was selected. Cemented rock fill (CRF) will be used for backfill. The underhand mechanized cut-and-fill method is highly
flexible and can achieve high recovery rates in deposits with complex geometries, as is the case at the Grassy Mountain deposit. The estimated mine life is 9.3 years.
The mining sequence contains a detailed level sequence and an underhand sequence. The level access is mined first. The mains are mined second. Typically, two
mains are mined at the same time providing multiple mining locations on a level. After the mains are mined, then the production drifts can begin mining. The production drifts are sequenced with primaries and secondaries. The primaries are mined and
backfilled first. This continues until the entire level is complete. After the entire level is complete the level access is backfilled. The underhand sequence is grouped into lifts. One level in each lift can be mining at any given time during the
life-of-mine. The underhand sequence starts at the top and works down in elevation. Constraints are applied to ensure that the bottom level of a lift does not influence the top level of the lift below.
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1.15.2
Mine Design
The portal is designed to allow access to the underground mine facilities while providing adequate space for equipment and vehicles. It will be located uphill
and south of the primary crusher. Weak rock mass ground conditions at the portal require that a shallow box-cut excavation be established to form a suitable face where tunneling can occur.
The Grassy Mountain orebody will be accessed using a 15ft x 15 ft main decline, developed from a portal on surface. The decline will provide a connection to
all services. The design intent is to have the decline located as close as possible to the mineralization to reduce transportation costs but sufficiently removed from mining activities to ensure that the decline is geotechnically stable for the
planned LOM.
Level stations will have a standoff distance from the orebody of approximately 300 ft. This distance is determined by the maximum gradient
of the level access of 12.5%, the geometry of accessing five levels for every one level station, and the geometry of the orebody. There are five stations planned for the mine, accessed off the decline, and each station will access up to five
production levels. Each station will have a truck loading bay (used to load trucks with load–haul–dump (LHD) vehicles), power bay (used to store the mobile load center), ventilation access (will connect on each station via vent raises),
stockpile (used to store material until it can be loaded into trucks), sump (used to collect mine water, and level access (provide access to the production stopes).
When a production stope gets within two rounds of the design, the stope will go on grade control. When a stope is on grade control, every round must be
sampled before the next round can be drilled. The stope may end prematurely or extend past the design if the assayed grade is below or above the cut-off grade.
The ventilation network was designed to comply with U.S. ventilation standards for underground mines. The planned ventilation will use a push/pull system and
will require a exhaust fan on the surface. A raise bore will be used to construct ventilation raises between level stations and connecting to the surface fan. Each vent raise will have a diameter of 12 ft. Each raise will be steel lined and
have an escape ladder. Auxiliary fans will take air from the main circuit and push the air to the working face on the level using vent ducting and vent bag. Each level will have an auxiliary fan at the level station.
Mine operations will be based on the usage of mobile mining equipment suitable for underground mines. The estimate of the fleet size was based on first
principles and equipment running-time requirements to achieve the mine production plan. Equipment is conventional for mechanized cut-and-fill mining operations.
Water will be needed for underground production drilling, bolting, shotcrete, and diamond drilling. The required LOM water supply has been estimated based on
the mine-equipment requirements.
Underground power will be provided by two transformers. The transformers will be moved, as required, depending on the
location of the mining activities. A main power line will be installed along the rib of the decline. Line power will also be extended to the locations of the ventilation raise to supply power to the ventilation fans.
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Two mobile emergency refuge stations will be provided in case of fire or rockfalls that would block access
and prevent full evacuation of personnel.
1.15.3
Mine Production Plan
The proposed production plan is shown in Figure 1-1.
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1.16
Processing and Recovery Methods
The process plant will be designed with conventional processing unit operations frequently used within the gold processing industry. The process plant will
treat 750 tons per day and will operate with two 12-h shifts per day, 365 days per year, producing gold doré bars. The major equipment within the process plant is specified in accordance with the climate, site conditions, ore grades and
metallurgical performance outlined in this report. Any deleterious metals present in the ore such as mercury will be abated by specialized equipment installed in the process plant and are not expected to impact payability terms. The plant will have
average head grades of 0.177 oz/ton Au and 0.277 oz/ton Ag.
The plant feed will be trucked from the underground mine to a modular crushing facility that
will include a jaw crusher as the primary stage and a cone crusher for secondary size reduction. The crushed ore will be ground by a ball mill in closed circuit with a hydrocyclone cluster. The hydrocyclone overflow with P80 of 150 mesh (106
µm) will flow to a hybrid leach/carbon-in-leach (CIL) recovery circuit via a pre-aeration tank. Gold and silver leached in the CIL circuit will be recovered onto activated carbon and eluted in a pressurized Zadra-style elution circuit and then
recovered by electrowinning in the gold room. The gold–silver sludge will be dried in a mercury retort oven and then mixed with fluxes and smelted in a furnace to pour doré bars. Mercury is condensed in the retort and collected for
off-site disposal. Carbon will be re-activated in a carbon regeneration kiln before being returned to the CIL circuit. CIL tailings will be treated for cyanide destruction prior to pumping to the tailings storage facility (TSF) for disposal.
The installed power for the process plant will be 4,445 hp and the power consumption is estimated to be 72 kWh/ton processed. Raw water will be pumped from
borehole wells to a raw-water storage tank. Potable water will be sourced from the raw water tank and treated by a potable water treatment plant. Gland water will be supplied from the raw-water tank. Process water will primarily consist of TSF
reclaim water. Reagents will include lime, sodium cyanide, sodium hydroxide, copper sulfate, hydrochloric acid and sodium metabisulfite.
The simplified
overall flowsheet is shown in Figure 1-2 The plant site layout is shown in Figure 1-3.
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Figure 1-2: Simplified Overall Flowsheet
Source: Ausenco, 2020
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Figure 1-3: Proposed Plant Site Layout
Source: Ausenco, 2020
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1.17
Infrastructure
1.17.1
Overview
The Project infrastructure includes a mining portal and decline, supported by an extensive network of access and haul roads connecting key facilities such as
the TSF, temporary waste rock storage facility (TWRFS) and other site areas. Surface infrastructure comprises site access controls, administrative and operational buildings, and specialized processing and support facilities including a gold room,
assay laboratory, reagent storage, workshops, warehouses and truck maintenance areas. Utilities and services include fuel storage and dispensing, water supply and treatment systems, water wells, a raw water tank and a 14.4 kV power line. Additional
components include waste and tailings management facilities and an explosives magazine to support the underground mining operations.
1.17.2
Temporary Waste Rock Storage Facilities (TWRSF) and Borrow Pits
During operation, a lined stockpile for waste rock will be temporarily managed on the surface to be used as CRF as needed. The containment and drainage
collection systems installed below the TWRSF will be the same systems used for the TSF impoundment basin.
A basalt borrow quarry will be located on the
east side of the mine area where there are basalts that are believed to be suitable for construction, mine-backfill and reclamation materials. A small borrow pit north of the processing area is planned for additional construction material. Borrow
material will be generated using contract mining.
Closure Cover Borrow Areas located immediately west of the basalt borrow quarry and south of the TSF
will be developed as additional vegetative closure cover material for final reclamation of the surface facilities.
1.17.3
Tailings Storage Facility
The proposed TSF will cover approximately 108 acres and will be located in a broad valley immediately west of the Grassy Mountain mine portal and process
facilities. The TSF will fill the valley and require embankments on the north and west sides to impound the tailings. The main embankment will cross the natural drainage on the north side of the TSF, and a secondary embankment will be constructed
along the western ridge. The TSF design envisages three overall stages, Stage 1 will be split into two intermediate phases.
Based on the TSF design, the
Stage 3 TSF will provide a total storage capacity of 3.64 Mtons. However, for the purposes of this Study, only approximately 2.4 Mtons are planned to be delivered to the TSF. Therefore, only Stages 1, 2, and a portion of Stage 3 are required for
this Study.
The TSF is designed as a “zero discharge” facility, capable of storing runoff from tributary areas and direct precipitation on
the facility resulting from the 500-year, 24-hour storm event, as well as an allowance for wave run-up due to wind action. It will be a 100% geomembrane-lined facility with a continuous, engineered lining system extending across the impoundment
basin and the upstream slope of the embankments.
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A lined reclaim pond, to be located downstream (north) of the TSF, will capture all tailings draindown
collected in the underdrain collection system from the tailings and TWRSF draindown. A supernatant pool will be maintained away from the embankments on the eastern side of the TSF by controlled deposition of tailings from spigots installed around
the perimeter of the facility.
1.17.4
Water Management
Contact and non-contact surface water will be routed around the plant site:
•
Non-contact water runoff is designed to flow into natural drainages downstream of the site to unnamed tributaries
of Negro Rock Canyon which in turn discharges to the lower Malheur River.
•
Meteoric water contacting the process plant site and associated infrastructure will be diverted through contact
water diversion ditches and channels to a geomembrane-lined contact water pond to be located east of the process plant.
Permanent
channels are designed to convey the 100-year, 24-hour storm event with nine inches of freeboard, or 500-year, 24-hour storm event without overtopping. Temporary channels were designed to convey the 25-year, 24-hour storm event with nine inches of
freeboard, or 100-year, 24-hour storm event without overtopping.
1.17.5
Water Balance
Water supply from the raw water production wells and mine dewatering is projected to be sufficient to support the mine plan requirements and during seasonal
fluctuations. Water demands are expected to increase and decrease seasonally and during periods of extended dry and wet climactic years, respectively. During periods of extended dry conditions, additional make-up water from the production wells may
be required.
1.18
Market Studies and Contracts
The proposed Grassy Mountain operation will produce doré bars on site, which will then be shipped to an out of State refinery. There is currently no
contract in place with any refinery or buyer for the doré.
No market studies have been completed. Gold and silver are freely-traded commodities.
The doré that will be produced by the mine is considered to be readily marketable with no deleterious/penalty elements. Although mercury is present in the ore, a retort and recovery system has been included to maintain doré quality.
Metal pricing used in the economic analysis is based on long-term flat metal prices of $3,600/oz Au, and $48.00/oz Ag, which are based on consensus
forecasts from various financial institutions.
Paramount has no current contracts for property development, mining, concentrating, smelting, refining,
transportation, handling, sales and hedging, forward sales contracts or arrangements.
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1.19
Environmental, Permitting and Social Considerations
The final Environmental Impact Statement (EIS) and record of decision were issued by BLM on January 29, 2026.
Draft state permits were issued for public comment on December 8, 2025. The public comment period has concluded and final state permits are anticipated
to be issued in the third quarter of 2026.
1.19.1
Environmental Considerations
Paramount is also currently working with BLM and local ranchers to develop and plan rangeland improvements in the vicinity of the mine site.
1.19.2
Permitting Considerations
Paramount is currently working with multiple tribal entities, BLM and the State Historical Preservation Office (SHPO) to finalize mine construction and
operation planning to minimize impacts to identified cultural resources. Following concurrence from SHPO, the final state permits are anticipated to be issued allowing for bonding and the progression of construction.
1.19.3
Social Considerations
Paramount continues to work with local, state, federal and tribal entities as the state permitting process is completed.
1.19.4
Closure and Reclamation Considerations
The closure plan and associated Reclamation Cost Estimate (RCE) were updated in February 2026 to account for updated unit rates and direction received from BLM
and Department of Geology and Mineral Industries (DOGAMI) during the permitting process. Both BLM and DOGAMI have accepted the closure plan and RCE.
1.20
Capital and Operating Cost
1.20.1
Capital Cost Estimate
The capital cost estimate is reported in Q2 2026 USD. The capital costs are at a minimum feasibility level of confidence of ±15% as is defined in S-K
1300, and are prepared using the AACE Class 3 estimate standards, with a contingency of 10%.
The estimate includes the cost to complete the design,
procurement, construction and commissioning of all the identified facilities. The estimate was based on the traditional engineering, procurement and construction management (EPCM) approach where the EPCM contractor oversees the delivery of the
completed project from detailed engineering and procurement to handover of a working facility. For equipment sourced in Canadian dollars (CAD), an exchange rate of 0.733 USD:CAD was assumed.
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The estimate was derived from budgetary pricing for major items in the mechanical equipment list, electrical
equipment list and contractor work packages (e.g. concrete, structural steel, platework, etc.), benchmarked against similar projects and scaled/escalated accordingly. The estimates were based on a number of fundamental assumptions as indicated in
process flow diagrams, general arrangements, material take offs (MTOs), cable schedules, scope definition and a work breakdown structure. The estimate included all associated infrastructure as defined by the scope of work developed in 2020 FS and
carried in the 2022 FS update.
The initial capital cost estimate of $189.8 million is summarized in Table 1-4.
Table 1-4: Initial Capital Cost Estimate Summary (direct and indirect)
WBS
Description
$ M
% of Total Costs
1000
Mining
26.2
14
2000
Site development
7.2
4
3000
Mineral processing
43.4
23
4000
Tailings management & waste rock facility
13.3
7
5000
On-site infrastructure
17.3
9
6000
Off-site infrastructure
16.8
9
Direct Subtotal
124.6
66
7000
Project indirect costs
28.0
15
9000
Owner’s costs
15.6
8
Indirect Subtotal
43.6
23
8000
Provisions (Contingency)
19.8
10
N/A
Capitalized Operating cost
1.7
1
Project Total – Initial Capital
189.8
100
1.20.2
Operating Cost Estimate
The operating cost estimate has an accuracy of ±15% reported in Q2 2026 USD. The operating costs are at a minimum feasibility level of confidence of
±15% as is defined in S-K 1300.
The LOM underground mining costs are estimated at $332.9 million over the LOM, and average $141.18/ton
processed over the LOM. Excluding mining costs from the pre-production period (accounted for in the initial capital cost) results in an average mining cost of $140.60/ton processed over the LOM.
The LOM process operating cost is estimated at $89.3 million over the LOM, and averages $37.72/ton processed over the LOM.
The LOM general and administrative (G&A) costs are estimated at $5.4M/a or $48.7M over the LOM, and average $20.65/ton processed over the LOM.
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1.21
Economic Analysis
1.21.1
Economic Summary
The economic analysis is based on proven and probable reserves. The capital and operating cost estimates were developed in Q2 2026 to target a level of
accuracy of ±15% which aligns with an AACE International Class 3 level estimate. The capital cost estimate includes a 10% contingency on the initial capital costs.
The Project has been evaluated using a discounted cashflow (DCF) analysis. Cash inflow consists of annual revenue projections for the Project. Cash outflows
such as capital costs, operating costs, taxes, and royalties are subtracted from the inflows to arrive at the annual cashflow projections.
The post-tax
net present value (NPV) at a 5% discount rate (NPV5%), is $374.7 million NPV5% with a post-tax internal rate of return (IRR) of 38.9%,
and an initial payback of 2.1 years. These economic results utilize base-case prices of $3,600/oz gold and $48.00/oz silver.
Table 1-5 below provides a summary of the forecast project economics.
Table 1-5:
Summary of forecast project economics
Area
Item
Units
LOM Total/Avg.
General
Gold price
$/oz
3,600
Silver price
$/oz
48.00
Mine life
years
9.3
Total mill feed tons
tons x 1,000
2,358
Production (gold)
Mill head grade Au
oz/ton
0.18
Mill recovery rate Au
%
92.6
Total mill ounces recovered Au
oz x 1,000
385.8
Total average annual production Au
oz x 1,000
41.4
Production (silver)
Mill head grade Ag
oz/ton
0.28
Mill recovery rate Ag
%
73.5
Total mill ounces recovered Ag
oz x 1,000
480.1
Total average annual production Ag
oz x 1,000
51.5
Operating Costs
Mining cost
$/ton processed
140.60
Processing cost
$/ton processed
37.72
G&A cost
$/ton processed
20.65
Total operating costs
$/ton processed
198.96
Refining cost Au
$/oz
5.00
Refining cost Ag
$/oz
0.50
*Cash costs net of by-products
$/oz Au
1,217.95
**AISC net of by-products
$/oz Au
1,441.57
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Area
Item
Units
LOM Total/Avg.
Capital Costs
Initial capital
$M
189.8
Sustaining capital
$M
65.1
Closure costs
$M
21.1
Financials (pre-tax)
Gross Revenue
$M
1,410.6
Pre-tax unlevered free cash flow
$M
658.0
Pre-tax NPV, 5%
$M
458.9
Pre-tax IRR
%
42.8
Pre-tax Payback
years
2.1
Financials (post-tax)
Post-tax unlevered free cash flow
$M
540.7
Post-tax NPV, 5%
$M
374.7
Post-tax IRR
%
38.9
Post-tax Payback
years
2.2
Notes:
*
Cash costs consist of mining costs, processing costs, G&A and refining charges and royalties.
**
All-in sustaining costs (AISC) include cash costs plus sustaining capital and closure costs. AISC is at the
project level and does not include an estimate of corporate G&A.
1.21.2
Sensitivity Analysis
A sensitivity analysis was conducted on the base-case pre-tax and post-tax NPV5% and IRR of the Project
using the following variables: metal prices, discount rate, total operating costs, initial capital costs, recovery, and head grade. The analysis showed that the Project is most sensitive to metal price, head grade, metallurgical recovery rates, and
initial capital cost, and less sensitive to operating cost.
1.22
Conclusions
Based on the assumptions and parameters presented in the Report, the Grassy Mountain Project has a mine plan that is technically feasible and economically
viable. The positive financials of the Project ($374.7 million post-tax NPV5% and 38.9% post-tax IRR) support the mineral reserve. A single-phase work program at $4.0 million is recommended to
further derisk the project in advance of the next phase of the project.
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2
INTRODUCTION
2.1
Introduction
Ausenco Engineering Canada ULC (Ausenco), Geotechnical Mine Solutions Inc. (GMS), RESPEC Company LLC (RESPEC), SLR International Corporation (SLR) and WSP USA
Inc. (WSP) compiled a technical report summary (the Report) on a feasibility study (the FS) completed on the Grassy Mountain Project (the Project) for Paramount Gold Nevada Corp. (Paramount), located in Oregon, USA (Figure 2-1).
This Report updates the previously filed technical report summary entitled, “Grassy Mountain Project:
S-K 1300 Technical Report Summary on Feasibility Study, Oregon, United States” with an effective date of June 30, 2022. Updates include the mineral resource estimate, mineral reserve estimate, capital costs, operating costs and the
economic analysis.
Paramount owns the Grassy Mountain Project through its wholly owned subsidiary, Calico Resources USA Corp. (Calico).
2.2
Terms of Reference
Measurement units used in this Report are generally U.S. customary; however, some units, such as analytical and metallurgical testwork units may be in metric
units. Unless otherwise stated, all monetary amounts are in United States dollars (USD).
Mineral Resources and Mineral Reserves are reported in
accordance with subpart 229.1300 of the S-K 1300 reporting requirements.
2.3
Qualified Persons (QP)
The following third-party QP firms contributed to the preparation of this Technical Report Summary:
•
Ausenco
•
GMS
•
RESPEC
•
SLR
•
WSP
Paramount contributed to Sections 1.2, 1.3, 1.4, 3.1, 3.2, 3.3, 3.4, 3.6, 3.7, 3.8, 4, 20, 21 and 22.2 of this Technical Report Summary.
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Figure 2-1: Project Location Plan
Source: Gustin et al., 2018
2.4
Site Visits and Scope of Personal Inspection
2.4.1
Site Inspection by the Qualified Person of Ausenco
Ausenco’s QP, Robert Raponi, conducted a site visit on August 15, 2019, and inspected the area planned for the portal and the general site layout.
2.4.2
Site Inspection by the Qualified Person of GMS
GMS’ QP, Andres Torres, did not conduct a site visit, and relied upon information from other QPs’ site visits.
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2.4.3
Site Inspection by the Qualified Persons of RESPEC
RESPEC’s QPs have visited the project site and/or Paramount’s field office and core logging facility in Vale, Oregon numerous times as the project
advanced. The most recent was by Mike Lindholm (geology and resources) and Sterling (Keith) Watson (mine engineering) for one day on January 30, 2026. Paramount provided RESPEC with an overview of the geology and other project information at
their core processing facility in Vale. RESPEC observed historical and Paramount paper files, QA/QC samples, core, RC samples, coarse rejects and pulps stored within the building. Although no drilling was being conducted at that time, Paramount
provided an overview of the core and RC logging, sample handling, storage and QA/QC procedures. RESPEC then reviewed the geology and observed planned locations for mine facilities at the Grassy Mountain site.
2.4.4
Site Inspection by the Qualified Person of SLR
SLR’s QP, Jeremy Scott Collyard, visited the project site on November 16, 2021 and met with senior technical staff from Paramount. The site visit
included an on-site tour with Paramount senior staff, local, State, and Federal permitting agencies to discuss the proposed TSF and TWRSF site.
2.4.5
Site Inspection by the Qualified Person of WSP
WSP’s QP, Christopher MacMahon, conducted a visit to the Project site on August 18, 2016; November 16, 2021, and January 29, 2026.
During these visits, Mr. MacMahon met with senior technical staff from Paramount. The August 18, 2016 site visit provided a general overview of the Grassy Mountain deposit area, including access to the Project, potential surface
infrastructure locations, and the site of the proposed portal for the underground mine access. The site visit included additional time at Paramount’s core storage and field office facilities in Vale, Oregon, which was used to further review
technical aspects of the Project. The November 16, 2021, site visit included an on-site tour with Paramount senior staff, local, State, and Federal permitting agencies to discuss the proposed TSF and TWRSF site. This site visit also included a
meet at the Vale field office. The January 29, 2026 site visit included a general overview of the proposed surface facility locations including the TSF, plant, and portal sites. The site visit included additional time at Paramount’s field
office facilities in Vale, Oregon, which was used to further review and discuss the Project.
2.5
Effective Dates
The Report has a number of effective dates as follows:
•
Mineral Resource estimates: February 28, 2026
•
Mineral Reserve estimate: May 15, 2026
•
Date of financial analysis that supports the Mineral Reserves: May 27, 2026.
The overall effective date of this Report is the effective date of the financial analysis, which is May 27, 2026.
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2.6
Information Sources and References
This Report updates the previously filed technical report summary entitled, “Grassy Mountain Project: S-K 1300 Technical Report Summary on Feasibility
Study, Oregon, United States” completed in 2022. Updates include the mineral resource estimate, mineral reserve estimate, capital costs, operating costs and the economic analysis. This Report is also based in part on internal company
reports, maps, published government reports, and public information, as listed in Section 25. Additionally, Ausenco relied on recent updated budgetary quotations from vendors to develop the cost estimates for this report.
Additional information was sought from Paramount employees in their areas of expertise as required.
2.7
Previous Technical Reports
Paramount has previously filed the following technical reports on the Project in Canada which are publicly available on SEDAR+:
•
Raponi T. R., Seamons J., Collyard, J. S., MacMahon, C., Dyer, T., and Torres, A. (2022): Grassy Mountain
Project: S-K 1300 Technical Report Summary on Feasibility Study, Oregon, United States. Report prepared by Ausenco Engineering Canada Inc., Arrowhead, SLR, RESPEC, GMS, and WSP for Paramount Gold Nevada Corp., effective date June 30, 2022.
•
Raponi T. R., Gustin M. M., Seamons J., DeLong R., MacMahon C., Palma L., 2020: Feasibility Study and Technical
Report for the Grassy Mountain Project, Oregon, USA: report prepared by Mine Development Associates, Golder Associates, EM Strategies, Geotechnical Mine Solutions and Ausenco Canada Inc. for Paramount Gold Nevada Corp., effective date
September 15, 2020.
•
Gustin, M.M., Dyer, T.L., MacMahon, C., Caro, B., Raponi, T.R., and Baldwin, D., 2018: Preliminary Feasibility
Study and Technical Report for the Grassy Mountain Gold and Silver Project, Malheur County, Oregon, USA: report prepared by Mine Development Associates, Golder Associates and Ausenco Canada Inc. for Paramount Gold Nevada Corp., effective date
May 21, 2018.
Prior to Paramount’s Project interest, the following technical reports were filed on the Project:
•
Wilson, S.E., Pennstrom, W.J. Jr., Batman, S.B., and Black, Z.J., 2015: Amended Preliminary Economic Assessment,
Calico Resources Corp., Grassy Mountain Project, Malheur County, Oregon, USA: report prepared by Metal Mining Consultants Inc. for Calico Resources Corp., effective date January 13, 2015, amended July 9, 2015.
•
Brown, J.J., Malhotra, D., and Black, Z., 2012: NI 43-101 Technical Report on Resources, Grassy Mountain Gold
Project, Malheur County, Oregon: report prepared by Gustavson Associates for Calico Resources Corp., effective date September 26, 2012.
•
Hulse, D.E., Brown, J.J., and Malhotra, D., 2012: NI 43-101 Technical Report on Resources, Grassy Mountain Gold
Project, Malheur County, Oregon: report prepared by Gustavson Associates for Calico Resources Corp., effective date March 1, 2012.
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•
Lechner, M.J., 2011: Grassy Mountain NI 43-101 Technical Report, Malheur County, Oregon: report prepared for
Calico Resources Corp., effective date June 6, 2011.
•
Lechner, M.J., 2007: Grassy Mountain Technical Report, Malheur County, Oregon: NI 43-101 Technical Report: report
prepared for Seabridge Gold Inc., effective date April 27, 2007.
2.8
Currency, Units, Abbreviations and Definitions
All units of measurement in this report are metric, and all currencies are expressed in US dollars (USD) unless otherwise stated. Contained gold metal is
expressed as troy ounces (oz), where 1 oz = 31.1035 g. All material tonnages are expressed as short tons (tons) unless stated otherwise. A list of abbreviations and acronyms is provided in Table 2-2, and
units of measurement are listed in Table 2-3.
Table
2-1: Abbreviations and Acronyms
Abbreviation
Description
AA
atomic absorption
ABA
acid-base accounting
AACE
Association for the Advancement of Cost Engineering
AAL
American Assay Laboratory
ABA
acid-base accounting
Ag
silver
AgEq
silver equivalent
As
arsenic
ASTM
American Society for Testing and Materials
Atlas
Atlas Precious Metals
Au
gold
AuEq
gold equivalent
Ausenco
Ausenco Engineering Canada ULC
AVRD
absolute value of relative differences
BLM
Bureau of Land Management
Calico
Calico Resources USA Corp./Calico BC
Chemex
Chemex Analytical Laboratories
CIL
carbon-in-leach
CIP
Carbon-in-pulp
CIM
Canadian Institute of Mining, Metallurgy, and Petroleum
CNWAD
Weak acid dissociable cyanide
COMEX
Commodity Exchange
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Abbreviation
Description
Cone
Cone Geochemical Laboratories
CPA
Consolidated Permit Application
CRF
cemented rock fill
CRM
certified reference material
Cryla
Cryla LLC
CSAMT
controlled-source audio-frequency magnetotelluric
CT
carbon total
Cu
copper
CUP
Conditional use permit
DO
dissolved oxygen
DOGAMI
Department of Geology and Mineral Industries
EE
Environmental Evaluation
EIS
Environmental Impact Statement
EM Strategies
EM Strategies Inc.
EPCM
Engineering, Procurement, and Construction Management
Fe
iron
FS
Feasibility Study
G&A
General and Administrative
GCL
Geosynthetic clay liner
GMS
Geotechnical Mine Solutions
Golder
Golder Associates Inc.
GPS
global positioning system
Hazen
Hazen Research Inc.
HDPE
high-density polyethylene
Hg
mercury
Hunter
Hunter Mining Laboratories
ICP-AES
inductively coupled plasma atomic-emission spectrometry
ID3
inverse-distance to the third power
IDS
International Directional System
IEC
International Electrotechnical Commission
IP
Intellectual property
IRR
internal rate of return
ISO
International Organization for Standardization
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Abbreviation
Description
JK
Julius Kruttschnitt
LHD
Load-haul-dump
LOM
Life of Mine
LTF
licencing timeframe
LUCS
Land Use Compatibility Statement
Major Drilling
Major Drilling America Inc.
MCC
Motor control centers
MDA
Mine Development Associates, Inc.
ML
metal leaching
MNP LLP
Meyers Norris Penny
MOP
Mean of pairs
MOU
Memorandum of Understanding
MSHA
Mine Safety and Health Administration
MTO(s)
Material Take-off(s)
NaCN
sodium cyanide
NAG
net-acid generating
NEPA
National Environmental Policy Act
Nevada Select
Nevada Select Royalty Inc.
Newmont
Newmont Exploration Ltd.
NGO
Non-governmental agency
NN
nearest neighbor
NNP
net-neutralizing potential
NOI
Notice of Intent
NPI
net profits interest
NPV
net present value
NSR
net sales revenue
OAR
Oregon Administrative Rule
ODEQ
Oregon Department of Environmental Quality
OK
ordinary-kriging
OWRD
Oregon Water Resources Department
Paramount
Paramount Gold Nevada Corp.
PCC
Project Coordinating Committee
PoO
Plan of Operation
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Abbreviation
Description
Project
Grassy Mountain Project
QA
Quality assurance
QC
Quality control
QP
Qualified Person
RC
reverse circulation
RCE
Reclamation Cost Estimate
RD
relative difference
RDI
Resource Development Inc.
RESPEC
RESPEC Company LLC
RMCG
Rocky Mountain Geochemical Corporation
S2-S
sulfide sulfur
Sherry and Yates
Sherry and Yates, Inc.
SHPO
State Historical Preservation Office
SLR
SLR International Corporation
SO4-S
sulfate- sulfur
SRK
SRK Consulting U.S., Inc.
ST
sulfur total
TIMA
Tescan Integrated Mineral Analyzer
TOC
total organic carbon
Tombstone
Tombstone Exploration Company Ltd
TRT
Technical Review Team
TSF
Tailings Storage Facility
TWRSF
Temporary Waste Rock Storage Facility
UG
underground
U.S.
United States
UTM
Universal Transverse Mercator
WMC
Western Mining Corp
WSP
WSP USA Inc.
Table
2-2: Units of Measurement
Abbreviation
Description
%
percent
% solids
percent solids by weight
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Abbreviation
Description
±
Plus or minus
°
angular degree
°C
degree Celsius
°F
degree Fahrenheit
µm
micron (micrometer)
$/ton
dollars per short ton
a
year (annum)
CAD
Canadian dollar
cm
centimeter
cm3
cubic centimeter
d
day
E
east
EGL
effective grinding length
ft
foot (12 inches)
ft3
cubic feet
g
gram
g/cm3
gram per cubic centimeter
g/L
gram per liter
g/t
gram per metric ton (tonne)
gal
US gallon
gpm
US gallons per minute
h
hour (60 minutes)
ha
hectare
hp
horsepower
in
inch
kg
kilogram
kg/t
kilogram per tonne
km, km2
kilometer, square kilometer
kPa
kilopascal
kV
kilovolt
kW
kilowatt
kWh/t
kilowatt-hour per tonne
L
liter
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Abbreviation
Description
lb
pound
m, m2, m3
meter, square meter, cubic meter
M
million
Ma
million years (annum)
masl
meters above mean sea level
mg
milligram
mi
mile
mm
millimeter
Moz
million (troy) ounces
MPa
megapascal
Mt
million metric tonne
Mton
million short ton
MW
megawatt
N
north
oz
troy ounce
oz/ton
ounce (troy) per short ton (2,000 lbs)
ppb
parts per billion
ppm
parts per million
psi
pounds per square inch
Q
quarter
S
south
s
second
t, tonne
metric tonne (1,000 kg)
ton
short ton (2,000 lbs)
t/d
metric tonnes per day
USD
US dollars
W
west
yr
year
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3
PROPERTY DESCRIPTION
3.1
Introduction
Paramount owns and controls 100% of the mineral tenure, through its wholly-owned subsidiary, Calico which owns and controls 100% of the mineral tenure of the
unpatented mining claims, patented mining claims, and mining leases that comprise the Grassy Mountain Project. The Grassy Mountain Project consists of two claims groups that are situated near the western edge of the Snake River Plain in eastern
Oregon, 20 miles (mi) south of the town of Vale, Oregon and about 70 miles west of Boise, Idaho (refer to Figure 2-1 and Figure 3-1).
Figure
3-1: Location of the Grassy Mountain Project
Source: Paramount, 2022
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The Grassy Mountain claims group encompasses approximately 9,300 acres located within surveyed townships in
Malheur County.
The geographic center of the Grassy Mountain claims group is located at 43.674° N latitude and 117.362° W longitude, and the
principal zone of mineralization, the Grassy Mountain deposit, is located at approximately 43.670° N latitude and 117.359° W longitude.
3.2
Mineral Tenure
The Grassy Mountain Project consists of 436 unpatented lode and mill site claims, three patented claims, and a land lease for 28 unpatented lode mining claims
Figure 3-2 and Figure 3-3. Patented claims were individually surveyed at the time of location. Unpatented claim boundaries were established initially by handheld GPS
units, and in 2011 by onsite survey work. Claim information is provided in Appendix A.
Unpatented claims are subject to annual U.S. Bureau of Land
Management (BLM) fees of $200 per claim. The unpatented annual claim fees have been paid and are not due until September 1, each year. Patented claims are subject to annual property taxes of $122 per year. Taxes for the 2024–2025 tax year
have been paid; taxes for the coming year are due December 2026.
Calico, a wholly-owned subsidiary of Paramount, owns and controls 100% of the mineral
tenure of the unpatented mining claims, patented mining claims, and mining leases that comprise the Grassy Mountain Project. Calico acquired all right, title, and interest in the Project pursuant to a “Deed and Assignment of Mining
Properties” between Seabridge Gold Inc., Seabridge Gold Corporation (collectively Seabridge Gold), and Calico dated February 05, 2013.
3.2.1
Mineral Concession Payment Terms
Annual property holding costs, including those to the Bureau of Land Management and to Cryla LLC (Cryla), total $98,142.
3.2.2
Land Access and Ownership Agreements
Paramount’s 100% ownership of the Grassy Mountain Project is subject to the underlying agreements summarized in the following subsections.
3.2.3
Seabridge Gold Corporation
All claims and property were transferred to Calico by Seabridge Gold. Seabridge Gold Corporation (Seabridge Gold) is entitled to a 10% net profits interest
(NPI) royalty. Pursuant to the Deed of Royalties, dated February 5, 2013 and modified in 2015 (see Section 3.3.1), within 30 days following the day that Calico made a production decision and construction financing was secured, Seabridge
may elect to cause Calico to purchase the 10% NPI for C$10 million (M). Otherwise Seabridge will retain the 10% NPI. Seabridge, at the Report effective date, is the second largest Paramount shareholder and has indicated that it will convert its NPI
into equity in Paramount, thus the Seabridge NPI has not been included in the FS.
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3.2.4
Sherry and Yates, Inc.
On February 14, 2018, Calico exercised an Option to Purchase whereby Sherry and Yates agreed to sell to Calico all right, title, and interest in three
patented and 37 unpatented mining claims. The 2004 Lease and Agreement with Sherry and Yates was then terminated, although Sherry and Yates retained a 1.5% NSR royalty over the claims (see Section 3.3.2).
3.2.5
Cryla LLC
In 2018, Calico signed a 25-year lease agreement with Cryla that applies to 28 unpatented lode mining claims located to the west of the Grassy Mountain deposit
(Figure 3-2). Calico is required to make an annual lease payment of $60,000 for the duration of the lease agreement. Calico is eligible to acquire the property for $560,000 plus $3/oz of gold reserves, as
defined by a pre-feasibility or higher confidence-level study. Additionally, Cryla retains a NSR royalty based on gold price for mineral produced from their claims (see Section 3.3.3).
Figure
3-2: Grassy Mountain Claim Group
Source: Paramount, 2020
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3.3
Royalties and Additional Encumbrances
3.3.1
Seabridge Gold
Pursuant to the Deed of Royalties, within 30 days following the day that Calico makes a production decision and construction financing is secured, Seabridge
Gold may elect to cause Calico to purchase the 10% NPI for 10 million CAD. Otherwise, Seabridge Gold will retain the 10% NPI. Seabridge Gold, as of the effective date of this Report, is the second largest Paramount shareholder.
3.3.2
Sherry and Yates
Sherry and Yates closed the purchase and sale of the three patented and 37 unpatented mining claims under terms of the 2004 Lease and Option Agreement. Sherry
and Yates retain a 1.5% royalty of the gross proceeds for the production of minerals from the patented and unpatented claims and a surrounding 1⁄2 mile area of
interest (Figure 3-3).
Figure
3-3: Sherry and Yates Area of Interest
Source: Paramount, 2020
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3.3.3
Cryla
Pursuant to the Deed of Royalties, Cryla is entitled to a NSR royalty on mineral or products produced from their claims group. Cryla is entitled to a 2% NSR if
the gold price is below or equal to $1,500/oz and a 4% NSR if the gold price is above $1,500/oz. Calico is entitled to reduce the NSR to 1% by paying Cryla $800,000 under any circumstances. The Mineral Resources and Mineral Reserves discussed
in this Report are outside the area of the Cryla claims group.
3.3.4
Other Encumbrances
There are no other encumbrances, liens, mortgages or legal actions against the properties.
3.4
Environmental Liabilities
Except for the exploration surface disturbance, primarily related to drilling, and the network of groundwater monitoring wells that will need to be reclaimed,
there are no known environmental liabilities associated with the Grassy Mountain Project.
All exploration drill holes that are not part of the current
approved monitor-well program have been plugged according to Oregon regulations. Surface disturbance that has not been reclaimed will potentially be used for future development activities and access. The groundwater monitoring wells remain in use
for ongoing exploration activities and ongoing data-acquisition activities. The disturbance is bonded as described in Section 3.6.
The company has
not violated any regulatory requirements, and no fines have been imposed to date.
3.5
Environmental Permitting
There is a valid exploration permit with the DOGAMI and the U.S. Bureau of Land Management (BLM). A bond in the amount of $146,200 is associated with this
exploration permit. An existing Notice (OR-068894) with the BLM for four acres of surface disturbance and a monitor well has an associated bond in the amount of $28,211.
A Conditional Use Permit (“CUP”) from Malheur County was approved by the Malheur County Planning Commission in May 2019. The CUP was extended in
2021 and also in July 2025 for an additional two years.
The TSF dam was approved by the Oregon Water Resources Department in July 2020. The approval is
valid for five years, and an extension can be requested. However, as the company filed a new Consolidated permit application in December 2021, a new approval is expected. No changes were made to the dam design.
The National Environmental Policy Act (NEPA) permitting process concluded in the final EIS and record of decision being issued by BLM on January 29,
2026. Draft state permits were issued for public comment and review in December 2025 and state agencies are currently in the process of finalizing permits. State permits will be issued at one time and are anticipated to be issued in the second half
of 2026.
Permits not obtained but needed for the type and scope of potential mining at Grassy Mountain as outlined in this Report will involve a number
of State and local regulatory authorities. The Project will require the environmental permits covering the construction, operation, and closure of the envisioned mine as discussed in Section 17. State permits are anticipated to be received
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Further information on environmental studies, permitting, and social and community impacts is discussed in
Section 17.
3.6
Surface Rights
Paramount owns the surface rights in the Grassy Mountain deposit area. The deposit is located within three patented mining claims. The surrounding surface
rights associated with the locations of the planned Project surface facilities belong to the Federal government and are managed by the Vale District office of the BLM.
3.7
Water Rights
Paramount holds a water right granted by the Oregon Water Resources Department to Calico. The water right was issued on April 5, 1990, through State of
Oregon Water Rights Application G-11847 and Permit G-10994. Use is limited to not more than 2.0 ft3/s (897.6 gpm) measured at the well.
On December 26, 2012, the Oregon Water Resources Department, Water Rights Services Division, granted Final Order Extension of Time for Permit Number
G-10994. This extension extended the date for Calico to fully develop and apply water to beneficial use to October 1, 2028. In 2019, Calico submitted an application to OWRD (T-13157) to modify the points of appropriation and place of use, and
to clarify language in the permit. On October 16, 2019, the State of Oregon issued a new Permit to Appropriate the Public Waters (G-18337) that replaces the previous permit and includes the requested modifications. This permit does not change
the 2.0 ft3/s of water use allowed.
3.8
Summary Statement
The QP is not aware of any significant factors and risks not discussed in this Report that may affect access, title, or the right or ability to perform work on
the Project, although the QP is not an expert with respect to such matters.
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4
ACCESSIBILITY, CLIMATE, LOCAL RESOURCES, INFRASTRUCTURE AND PHYSIOGRAPHY
4.1
Access
Access to the main Grassy Mountain deposit is provided by Twin Springs Road, a seasonally maintained unpaved road that originates at Russell Road, a paved
two-lane county road that joins with U.S. Highway 20 approximately four miles (mi) west of Vale, Oregon. The center of the Project area may be reached from the Twin Springs Road via 2.5 mi of secondary unpaved roads. Winter and wet weather
conditions occasionally limit access to the property, although on-site travel is generally possible year-round. Figure 4-1 shows the road access from Vale to the Grassy Mountain claims group.
Figure
4-1: Access to Grassy Mountain Claims Group
Source: Paramount, 2020
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4.2
Physiography
The Project area is in the semi-arid high-desert plateau region of eastern Oregon. The terrain is mainly open steppe with mesas, broad valleys, and gently
rolling hills to steeper uplands (Figure 4-2).
Figure
4-2: Photograph of Grassy Mountain Area Looking
Source: photography by Paramount and modified by MDA, 2018
Elevations range from 3,330 to 4,300 ft above mean sea level (amsl) at the main Grassy Mountain area, while elevations at the Frost Area claims group range
from 4,400 to 5,000 ft (amsl). Vegetation across the entire area consists of sagebrush, weeds, and desert grasses tolerant of semi-arid conditions.
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4.3
Climate
The climate is of the semi-arid, continental-interior type, with average annual precipitation of about 9.25 inches (in), roughly half of which falls as snow
between November and March. Local weather data indicate a mean annual temperature of 52° F, with daily temperatures ranging from an extreme low of -20°F in the winter to extreme highs of 100°F and higher in the summer.
It is expected that mining activities will be conducted year-round. Seasonal road maintenance is anticipated to be sufficient to provide initial access to the
site for all personnel and any deliveries related to the mine site and construction. The road will be upgraded for year-round activities during mine construction.
4.4
Water Supply
Water to support current exploration activity is available from on-site wells. Long-term water needs for mining and processing will require additional wells to
ensure availability. Existing capacity is as much as 200 gpm from multiple water wells situated near the proposed mill and mine sites.
A new Permit to
Appropriate the Public Waters was issued in 2019 (T-18337); refer to Section 3.7. The water extraction rate is sufficient to support the requirements of the proposed mine and processing facility. Project water requirements and sources are
described in more detail in Section 15.
4.5
Power
A regional, 500-kV electrical transmission line runs through the southern part of the Project area, about 2.5 mi south of the proposed mine site. However, the
high voltage of this interstate transmission line makes it unsuitable as a source of power for the site. Studies and designs have been completed based on a power source from the Hope Substation owned by Idaho Power Company, located along U.S.
Highway 20 (Figure 4-3; see also discussion in Section 15).
4.6
Infrastructure
As of the effective date of this Report, groundwater monitoring wells and unpaved access and drilling roads are the only existing infrastructure within the
Grassy Mountain Project area. The infrastructure required for the proposed operation is detailed in Section 15.
4.7
Community Services
The community nearest the Project is Vale, Oregon, with a population of approximately 1,700. Vale is the seat of Malheur County and the home of all related
government offices. The regional BLM office is also located in Vale.
Fuel, restaurants, lodging, groceries, hardware supplies, and equipment-repair shops
are available in Vale. Other logistical support is available in Nyssa and Ontario, Oregon, both of which are located within 30 mi of the Project. Boise, Idaho, a major metropolitan city, is within a 90-minute drive of the Project area. Mining
personnel, equipment suppliers, engineering expertise, and telecommunications services are all expected to be available within the area.
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Figure
4-3: Proposed Power Source for the Planned Operation
Source: Paramount, 2018
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5
HISTORY
5.1
Introduction
The information summarized in this section of the report has been extracted and modified from Wilson et al. (2015a), which was drawn from Hulse et al. (2012),
with additional information derived from multiple other sources, as cited. A concise early history of the discovery of the Grassy Mountain deposit and other events through to September 1988 was reported by Kelly (1988). RESPEC reviewed this
information and believes this summary accurately depicts the history of the Grassy Mountain Project.
Portions of the present Grassy Mountain Project were
first staked by two independent geologists, Richard “Dick” Sherry and Eugene “Skip” Yates, in 1984. Atlas Precious Metals (Atlas) acquired the Sherry and Yates interests in the Grassy Mountain area in 1986. Between 1986 and
1991, Atlas conducted extensive exploration of the property that culminated in the discovery and delineation of the Grassy Mountain deposit, as well as the identification of a number of other peripheral exploration targets. Atlas collected extensive
geological, mine engineering, civil engineering, metallurgical and environmental baseline data related to the Grassy Mountain deposit that were used to support a 1990 historical feasibility study for an envisioned open-pit heap-leach and milling
operation. Atlas then began to consider underground-mining scenarios, but declining gold prices and the perception of an unfavorable permitting environment discouraged Atlas from developing the Project, and the claims group was optioned to Newmont
Exploration Ltd (Newmont) in 1992 and Tombstone Exploration Company Ltd (Tombstone) in 1998. In February 2000, Seabridge entered an option agreement with Atlas to acquire a 100% interest in the Grassy Mountain claims group and completed the
acquisition in April 2003.
Seabridge did not carry out exploration at the Grassy Mountain Project. In April 2011, Seabridge signed an option agreement
granting Calico the sole and exclusive right and option to earn a 100% interest in the claims group. The acquisition of the Grassy Mountain claims group by Calico was completed in 2012. In 2011 and 2012, Calico carried out geologic mapping and
sampling and drilled a total of 13,634 feet in 17 holes. Calico also commissioned a geophysical survey to assist in their exploration efforts.
Paramount
acquired Calico in 2016.
5.2
1986-1996 Exploration
Historical exploration conducted by previous operators includes exploration programs carried out by Atlas, Newmont, Tombstone, Western Mining Corp. (WMC), and
Calico.
5.2.1
Atlas 1986-1992
Atlas carried out geologic mapping and recognized soil geochemistry as an important exploration tool at Grassy Mountain. Most Atlas exploration targets were
initially identified by claim-corner soil sampling on 600-ft by 1,500-ft spacings. Atlas conducted additional soil and float sampling on several anomalies and identified a genetic link between
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gold mineralization and silicification. Of the 400 drill holes completed by Atlas, 196 were reverse circulation (RC) holes drilled on 75- to 100-ft centers within what became the Grassy Mountain
deposit area. The remaining holes were drilled at other targets within the Grassy Mountain claims group. Atlas also drilled 87 RC holes at the Crabgrass deposit and defined three separate near-surface zones of gold and silver mineralization.
Details and results of the drilling are provided in Section 7.2.1.1.
5.2.2
Newmont 1992-1996
Newmont carried out extensive and locally detailed geologic mapping and conducted both soil and rock-chip sampling. In 1993, Newmont geologists mapped 40
square miles at a scale of 1:6,000 and collected approximately 2,600 soil samples on a 400-ft by 200-ft grid in hopes of identifying anomalies missed by prior Atlas sampling. During 1993 and 1994, Newmont collected more than 400 rock-chip samples
and conducted several geophysical surveys, including a ground-based gravity survey along existing roads, airborne magnetic and radiometric surveys over the entire property, and ground-based gradient-array (IP/resistivity) surveys over the Grassy
Mountain deposit and several of the satellite prospects. Ground magnetic surveys were conducted at specific areas. Newmont geologists re-logged the remaining Atlas drill core during this period, and eventually the Atlas RC drill chips as well.
In 1994, Newmont drilled 11 inclined core holes designed to intersect and define the geometry of potential high-grade gold zones within the Grassy Mountain
deposit. These were followed with one core hole wedged off of the initial core hole, two holes pre-collared by RC and completed with core, and one additional core hole.
Newmont’s 15 holes were all angled and totaled 15,009.5 ft. This drilling defined what Newmont thought could be several gold zones in excess of 0.1
oz/ton Au within an area of the Grassy Mountain deposit measuring approximately 600-ft long by 350-ft wide by 250-ft thick. Mineralization was constrained to the northeast by a single drill hole that failed to encounter high-grade gold. Newmont
considered the western extent of the main high-grade zone effectively closed off after encountering only low-grade mineralization (0.012–0.019 oz/ton Au) and local barren quartz–chalcedony veins. Based on the core drilling and mapping
and sampling of surface exposures, Newmont geologists concluded that high gold grades at the Grassy Mountain deposit were controlled by narrow, steeply south-dipping quartz-chalcedony veins and clay matrix breccias that would need to be properly
represented by grade modeling and resource estimation.
Details and results from the drilling are provided in Section 7.2.1.2.
During 1995 and 1996, Newmont’s activities focused on estimating Mineral Resources at the main Grassy Mountain deposit. No new exploration work was done
during this period.
5.2.3
1996 Exploration at Outlying Targets within the Grassy Mountain Claims Group
By 1996, Atlas and Newmont identified and named a number of mineralized and potentially mineralized target areas peripheral to the main Grassy Mountain gold
deposit based primarily on rock-chip, float, and soil-sample data. These outlying targets, several of which were drilled to varying extents, are shown in Figure 5-1.
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Figure
5-1: Outlying Target Area Map
Note: Blue lines demark the outer limits of Paramount’s claims group; UTM NAD83 US Feet, Zone 11 projection; contour
interval is 10 ft. 5,000-ft grid lines for scale. Dots are drill hole collars through 2012 colored by gold values. Source: Paramount, 2016
5.2.3.1
Wheatgrass
This target area is approximately 1,500 ft southwest of the Grassy Mountain deposit area (Figure 5-1) and was the site
of the first drilling on the claims. Wheatgrass may be a lateral continuation of mineralization extending from the main Grassy Mountain deposit that is displaced by down-to-the-west faults. A number of RC drill holes tested this area with some
narrow, low-grade intersections being encountered. Most of these historical holes were drilled vertically and are widely spaced.
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5.2.3.2
North Spur
North Spur is 2,000 ft to the north–northeast of the main Grassy Mountain deposit (Figure 5-1). Resistant ledges
of silicified sandstone indicate hydrothermal fluids flowed through the North Spur area. Three widely spaced vertical RC holes south of the silicified ledges intercepted elevated gold grades. About 500 ft to the north, a fence of three vertical RC
holes is located approximately at the northern margin of the most strongly silicified outcrops. These holes penetrated intervals with generally low gold grades, but they are sporadically mineralized. Review of RC chips and logs from these holes
indicates that gold grades decrease down hole as the sandstone intervals transition to more clay-rich units with depth. All of these holes were drilled vertically and did not adequately test for steeply dipping mineralized structures.
5.2.3.3
Crabgrass
The three mineralized areas that comprise the Crabgrass prospect (Figure 5-1) appear to be stratiform and are contained
within the flat-lying to gently east-dipping sandstones above clay-rich units, but confidence in these observations is limited by the fact that all the historical holes are vertical and drilled by RC methods. Significant low-grade gold
mineralization was encountered in numerous holes, which formed the basis for a historical resource estimate.
5.2.3.4
Bluegrass and North Bluegrass
These targets are located 1.2 miles and 1.6 miles northeast of the Grassy Mountain deposit, respectively (Figure 5-1).
Sixteen RC holes were drilled in the area to follow up on rock-chip and float-chip samples with elevated gold contents. Further work is needed to warrant additional drilling.
5.2.3.5
Snake Flats
This area is 2.25 miles to the northeast of the Grassy Mountain deposit (Figure 5-1). The target was identified by
mapping float of silicified arkose and sinter boulders. A large mercury, arsenic, and antimony soil anomaly extends down-slope for approximately 3,500 ft to the northeast. This is the most aerially extensive surface geochemical anomaly at the
Project other than at Wheatgrass. Some of the samples from the altered boulders yielded elevated gold values; the source area for these boulders appears to be somewhere beneath post-mineral basalt that occurs in the area. Three RC holes were drilled
through about 100 ft of the post-mineral basalt before intersecting unaltered sandstone and siltstone. Additional work is necessary to better define drill targets.
5.2.3.6
Wood
The Wood target is 1.2 miles northwest of the main Grassy Mountain deposit area (Figure 5-1). Wood was identified by
surface rock and soil sampling, followed by surface trenching. Rock-chip samples that were taken from a small outcrop of weakly silicified volcanic rocks returned elevated gold values. Fifteen shallow RC drill holes were completed in the area, some
of which returned encouraging results.
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5.2.3.7
Wally
The Wally, or Big Wally, target is 1.5 miles north–northwest of the Grassy Mountain deposit (Figure 5-1). Soil
samples in the Wally area defined overlapping arsenic, mercury, antimony, and gold anomalies that straddle a north-northwest-trending fault shown on the district geology map. Drilling returned some favorable results.
5.2.3.8
Ryegrass
The Ryegrass, or Dennis’ Folly, target is located 1.2 miles north of the Grassy Mountain deposit (Figure 5-1).
This area was identified by mapping silicified zones that returned low-level gold values and anomalous mercury in rock-chip samples.
5.2.3.9
Clover
This target is one mile west of the Grassy Mountain deposit (Figure 5-1) and is identified as an area of weakly
silicified arkose adjacent to a northeast-trending fault. Rock-chip sampling identified an outcrop containing 25 ppb gold.
5.2.3.10
Bunchgrass
Bunchgrass is an area of modestly elevated mercury, arsenic, and antimony in soil samples located 0.5 miles south of Crabgrass (Figure 5-1). Wilson et al. (2015a) reported that the target area is approximately 750 ft wide.
5.2.3.11
Sweetgrass
Sweetgrass is located approximately 1.75 miles southwest of the Grassy Mountain deposit (Figure 5-1). Sampling of a
large float boulder of siliceous sinter returned elevated gold values. Although additional sampling in the area did not return any significant values, more work is warranted to determine the source of this siliceous sinter boulder.
5.3
1998-2016 Exploration
5.3.1
Tombstone 1998
Prior to finalizing their agreement with Atlas, Tombstone reviewed data from previous work and commissioned an economic study of alternative development
scenarios. Tombstone subsequently drilled 10 RC holes, six of which were completed with core tails, for a total of 8,071 ft. Tombstone relied heavily on Newmont’s gradient-array IP/resistivity geophysical surveys to define their drilling
targets. Details and results of the Tombstone drilling are provided in Section 7.2.1.3.
5.3.2
Seabridge 2000-2010
Seabridge acquired the Grassy Mountains claims group in 2000 and then optioned the property to Calico in early 2011. Seabridge did not conduct any exploration.
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5.3.3
Calico 2011-2016
Prior to the acquisition of Calico by Paramount, Calico geologists conducted geologic mapping and compiled the Atlas and Newmont geology and surface sample
data using a geographic information system (GIS) software. During 2011 and 2012, a total of 13,634 ft was drilled in 14 RC and three core holes. Thirteen of these holes were drilled at the Grassy Mountain deposit area and four were drilled to test
outlying targets. Details and results of the Calico drilling are provided in Section 7.2.1.4.
In 2012, Calico commissioned a 25.1 line-mile
controlled-source audio-frequency magnetotelluric (CSAMT) survey conducted by Zonge Geosciences Inc. (Zonge). The survey lines were oriented N20°W (Figure 5-2) and arranged to cross the trend of known
mineralization.
Figure
5-2: Map of 2012 CSMAT Lines
Note: Red lines show CSAMT lines. Blue lines demark the outer limits of Paramount’s claims group; UTM NAD83 US Feet,
Zone 11 projection; contour interval is 10 ft. 5,000-ft grid lines for scale. Dots are drill hole collars through 2012 by maximum gold assays. Source: Wright, 2012
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The CSAMT survey was done under the supervision of consulting geophysicist J.L. Wright of Wright Geophysics,
Spring Creek, Nevada. Mr. Wright documented the survey methods and parameters, analyzed the processed data provided by Zonge, and made geologic and exploration interpretations in a 2012 report to Calico that included 18 inverted resistivity
sections and interpretive overlays in PDF format, as well as ArcGIS and MapInfo electronic data files (Wright, 2012).
The CSAMT survey identified a zone
of high resistivity that encompassed the main Grassy Mountain gold deposit (Figure 5-3), which is attributed to the zone of extensively silicified rocks in the deposit area. The high-resistivity response
was visible in sectional and plan views of the resistivity inversion; an example is shown in Figure 5-3.
Figure
5-3: CSAMT Inversion: Resistivity at 328 to 656 Feet Below Surface
Note: Blue lines demark the outer limits of Paramount’s claims group; UTM NAD83 US Feet, Zone 11 projection; contour
interval is 10 ft. 5,000-ft grid lines for scale. Grey dots are drill hole collars through 2012. Source: Wright, 2012
5.4
Production
There has been no production at the Grassy Mountain Project.
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6
GEOLOGICAL SETTING, MINERALIZATION AND DEPOSIT
6.1
Introduction
The information presented in this section of the report is derived from multiple sources, as cited. RESPEC reviewed this information and believes this summary
accurately represents the Grassy Mountain project geology and mineralization, as it is presently understood.
6.2
Regional Geologic Setting
The Grassy Mountain gold–silver deposit is the largest currently recognized epithermal hot-spring precious-metal deposit of the Lake Owyhee volcanic
field. The Lake Owyhee volcanic field is located at the intersection of three tectonic provinces: the buried North American cratonic margin, the northern Basin and Range, and the Snake River Plain. During mid-Miocene time, large-volume peralkaline
and subalkaline caldera volcanism occurred throughout the region in response to large silicic magma chambers emplaced in the shallow crust (Rytuba and McKee, 1984). The Lake Owyhee volcanic field includes several ash-flow sheets and rhyolite tuff
cones that erupted between 15.5 to 15Ma (Rytuba and Vander Meulen, 1991). The district geology surrounding the Grassy Mountain gold deposit is shown in Figure 6-1.
At about 15Ma, subsidence of the Lake Owyhee volcanic field triggered a change in volcanic eruption styles, which resulted in basaltic and rhyolite deposits
of limited extents. Volcanism during the middle to late Miocene was characterized by the eruption of small-volume metaluminous high-silica rhyolite domes and flows, small-volume basalt flows, and mafic vent complexes in north- and northwest-trending
Basin and Range-type fracture zones and ring structures related to resurgent calderas. Regional subsidence involved the development of extensive grabens and facilitated the formation of fluvial systems and large lacustrine basins. Large volumes of
fluvial sediments, sourced in part from the exhumed Idaho Batholith to the east and southeast, were deposited contemporaneously with volcanism and hot-spring activity during the waning stages of volcanic field development (Cummings, 1991). The
resulting regional stratigraphic section is a thick sequence of mid-Miocene volcanic rocks and coeval to Pliocene-age lacustrine, volcaniclastic, and fluvial sedimentary rocks. The oldest units encountered are the flow-on-flow Blackjack and Owyhee
Basalts (14.3 to 13.6Ma). These basalts are overlain by arkosic sandstone, tuffaceous sandstone, and conglomerates of the Deer Butte Formation.
6.3
Local and Project Geology
Bedrock outcrops in the vicinity of the Grassy Mountain project are typically composed of olivine basalt flows and siltstones, sandstones, and conglomerates of
the Miocene Grassy Mountain Formation. These rocks are locally covered with relatively thin, unconsolidated alluvial and colluvial deposits. Erosion-resistant basalt flows cap local topographic highs, including Grassy Mountain proper, which is a
prominent northeast-elongate ridge that forms a topographic crest about one mile southeast of the Grassy Mountain gold–silver deposit (Figure 6-1). Arkosic sandstones are encountered at the surface and
at depth, but individual beds or sequences have not been correlated across the project area, in part due to lateral sedimentary facies changes and structural offsets. Surface exposures and drill-defined stratigraphy at the Grassy Mountain deposit
area reveal complex facies produced during the waning stages of volcanism of the Lake Owyhee volcanic field and development of the coeval Ore-Ida graben (Lechner, 2011).
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Figure
6-1: Grassy Mountain Regional Geology
Source: RESPEC, 2026
Figure
6-2 shows the local stratigraphic column in the vicinity of the Grassy Mountain project. The lowermost unit intersected by drilling at the Grassy Mountain deposit is the Kern Basin Tuff, a sequence of
pumiceous crystal tuff that in part displays cross beds and local surge structures and non-welded to densely welded rhyolite ash-flow tuff. Clast
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size, thickness of individual ash units, and bedding structures suggest a source in the Grassy Mountain project area (Cummings, 1991). The Kern Basin Tuff ranges in thickness from 300 ft on the
south bluffs of Grassy Mountain proper to at least 1,500 ft in a drill hole beneath the Grassy Mountain gold–silver deposit.
Figure
6-2: Stratigraphic Column for the Grassy Mountain Area
Source: Paramount, 2020
A
small local flow-dome of approximately 12.5 Ma and known as the Butterfly Hill Rhyodacite overlies the Kern Basin Tuff (Figure 6-2). However, in most of the project area the Kern Basin Tuff is overlain by a
series of fluvial, lacustrine, and tuffaceous sediments that are assigned to the Grassy Mountain Formation (Cummings, 1991). These sedimentary
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units include granitic-clast conglomerate, arkosic sandstone, fine-grained sandstone, siltstone, tuffaceous siltstone, and mudstone (Figure 6-2). The
sedimentary units of the Grassy Mountain Formation, which host the entirety of the current Grassy Mountain Resources, range from 300 ft to over 1,000 ft in thickness. Several siliceous “terraces” and siliceous-sinter deposits are
interbedded with silicified units of the Grassy Mountain Formation. Terrace construction was apparently episodic and intermittently inundated by fluvial and lacustrine sediments and ash, resulting in an interbedded sequence of siltstone, tuffaceous
siltstone, sandstone, conglomerate, and sinter-terrace deposits. Load casts, flame textures, convolute laminations, and other soft-sediment deformation textures are common in both the sinter beds and other sedimentary units (Siems, 1990). The amount
and size of the sinter clasts in the sedimentary rocks reflect relative proximity to a terrace. Proximal deposits are angular, heterogeneous, clast-supported breccias of sandstone, siltstone, and sinter with indistinct clast boundaries in a sulfidic
mud-textured matrix.
According to Lechner (2007), the sedimentary units of the Grassy Mountain Formation are unconformably overlain by 50 to 100 ft of
black-chert pebble conglomerate interbedded with unconsolidated siltstone. This unit is recessive, and it is overlain by flows of olivine basalt assigned to the Grassy Mountain Basalt, and, in the northwestern part of the project area, by the basalt
of Negro Rock (Figure 6-2). These mafic lavas are overlain by lacustrine and fluvial siltstone, sandstone, and conglomerate, which are successively overlain by the Rock Springs lacustrine deposits and basalt
lavas that together make up the late-Miocene Idaho Group.
6.4
Grassy Mountain Deposit
6.4.1
Geology
The geology of the Grassy Mountain deposit area is shown in Figure 6-3. The deposit is centered beneath a prominent,
150-ft-high, silicified and iron-stained hilltop that consists of hydrothermally altered arkose and interbedded conglomerate of the Grassy Mountain Formation. Bedding is horizontal at the hilltop and dips 10 to 25° to the north–northeast
on the northern and eastern flanks. The bedding steepens to 30 to 40° on the west side of the hill due to drag folding in the footwall of the N20°W-striking Antelope fault. The southwest slope is covered by landslide debris of silicified
arkose.
Several horizons of laminated silica, from a few inches to several feet in thickness, crop out southwest and north of the deposit area and are
interbedded within the arkose, siltstone, and conglomerate of the Grassy Mountain Formation. Geologists interpret these horizons as beds of silica sinter (Figure 6-2), due in part to the presence of fossil
reeds, petrified wood, and other fossilized plant debris. Drilling within the Grassy Mountain deposit penetrated through more numerous and much thicker sinter horizons, indicating the sinter was deposited from hydrothermal fluids venting at the
paleo-surface within the accumulating fluvial sedimentary sequence.
Drilling has also shown that in the subsurface of the deposit area the arkosic
sandstones and conglomerates are interbedded with numerous intervals of siltstone and mudstone, much of which is thinly laminated. Beds with clay-altered ash to lapilli-sized tephra are common, and there are abundant layers rich in organic carbon
± carbonized plant debris. The laminated siltstone and mudstone intervals reflect a predominantly lacustrine setting that was the site of frequent episodic influxes of fluvial sand- to cobble-sized material.
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Figure
6-3: Grassy Mountain Deposit Area Geologic Map
Source: RESPEC, 2026
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6.4.2
Structure
The Grassy Mountain gold–silver deposit is situated within a zone of complex extensional block faulting and rotation. Faults at Grassy Mountain are
dominated by N30°W- to N10°E-striking normal faults developed during Basin and Range extension and are inferred to have post-mineral displacement. On the east side of the deposit, these faults are inferred to have down-to-the east movement
based on interpreted offsets of a prominent white sinter bed in drill holes, as well as drilled intersections of fault gouge. A set of orthogonal, N70°E-striking high-angle faults of minor displacement are inferred to link the graben faults. One
of these, the Grassy fault, has a vertical offset of only 10 to 40 ft or less, although it coincides with the axis of the high-grade core of the deposit.
6.4.3
Alteration and Mineralization
Hydrothermal activity and gold mineralization occurred during the accumulation of the Grassy Mountain Formation, coeval with active sedimentation. Therefore,
the water-saturated, unconsolidated sediments required silicic ± potassic alteration to develop sufficient competency to allow for the creation of fractures and structurally induced open space.
Silicification is the principal hydrothermal alteration type associated with gold–silver mineralization at the Grassy Mountain deposit. It takes the
form of silica sinter, pervasive silica flooding, and cross-cutting chalcedonic veins, veinlets, and stockworks. Silicification is inferred to be largely controlled by hot-spring vents active during accumulation of the Grassy Mountain Formation. The
300-ft deep main sinter is underlain by a zone of strong silicification with silica flooding and chalcedonic quartz veins.
Small amounts of fine-grained
pyrite are present in silicified rocks that have not undergone later oxidation. In some parts of the deposit, particularly within arkose and sandy conglomerate units, silicification is accompanied by potassic alteration in the form of adularia
flooding. Orthoclase, present primarily in sand-sized grains and in granitic clasts, is unaffected by potassic alteration, while plagioclase is replaced by adularia. Adularia is extremely fine-grained and is identified microscopically or by
cobaltinitrite staining. Silicic and potassic alteration zones are surrounded by barren, unaltered, clay-rich (20–40% montmorillonite), tuffaceous siltstone and arkose with minor diagenetic pyrite.
The Grassy Mountain gold–silver deposit is located largely within the zones of silicic and potassic alteration beginning approximately 200 ft below the
surface. The deposit has extents of 1,900 ft along a N60°E to N70°E axis, as much as 2,700 ft in a northwest-southeast direction, and as much as 1,240 ft vertically. The surface expression of mineralization is indicated by weak to moderately
strong silicification and iron-staining, accompanied by scattered, 1/8- to 1.0-inch-wide creamy to light-gray chalcedonic veins that fill joints.
The
deposit consists of a central, higher-grade core with gold grades of >~0.03 oz/ton Au that is surrounded by a broad envelope of lower-grade mineralization. The central, higher-grade core is almost 1,000 ft long on the N60°E to N70°E axis,
450 ft in width, and 450 ft in vertical extent, and it lies above the Kern Basin Tuff and below a distinctive sinter unit. Representative cross-sections through the deposit are provided in Section 11.7.1 (see Figure 11-1 to Figure 11-4).
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6.4.3.1
Central Higher-Grade Core Zone
Three distinct and overlapping types of gold–silver mineralization are recognized within the central core of the Grassy Mountain deposit: gold-bearing
chalcedonic quartz ± adularia veins, disseminated mineralization in silicified siltstone and arkose, and gold and silver in bodies of clay matrix breccia.
Zones of high-grade mineralization are defined by the presence of chalcedonic quartz ± adularia veins. Mineralized quartz ± adularia vein types
include single, banded, colloform, brecciated, and calcite-pseudomorphed veins. Colloform veins tend to carry the highest grades (>0.5 oz/ton Au), with visible gold up to as much as 0.02 inches in the longest dimension associated with argentite.
Veins with relict bladed calcite texture also contain higher gold grades than the banded and single vein types. Gold mostly occurs as electrum along the vein margins or within microscopic voids. Some veins carry very little grade or are barren. At
least some of the higher-grade zones of veins are thought to strike approximately N70°E.
Vein widths range from 1/16 to ~2.0 inches. Individually,
such narrow veins are unlikely to have lateral or vertical extents of significance, but vein frequency can average one vein per foot in places. Zones of veining have strike lengths of 400 to 700 ft and vertical extents of 100 to 250 ft at elevations
of 3,150 to 3,400 ft. Individual veins are too narrow to trace or correlate from hole to hole. However, the zones of veining have continuity.
A
steep southerly dip of the veins (70–85°) is inferred from vein intersection angles with drill core axes and bedding. Veins are mostly perpendicular to bedding, which generally dips 10–25° NNE within the deposit. Vein
intersection angles of 10–25° to the core axis were mostly recorded in core holes GMC-001 to GMC-008 angled at -50° at S20°E, compared with 25° to 50° intersection angles in holes GMC-009 to GMC-011 angled -50° at
N20°W. The N70°E strike of the vein zones is supported by: 1) surface mapping, 2) vein orientation perpendicular to bedding, 3) grade-thickness contouring, and 4) the overall trend in mineralization with grades in excess of ~0.03 oz/ton Au.
The veins crosscut the silicified sediments and have extremely sharp grade boundaries with the sediments. Vein frequency diminishes abruptly below an
elevation of ~3,000 ft at the west–southwest limit of the higher-grade core to ~3,100 ft at the east-northeastern limit. Very few high-grade veins are encountered above the higher-grade core of the deposit.
Within the higher-grade core, high gold grades are also present in silicified siltstone and arkose with no visible veins. In these cases, gold and silver are
inferred to be very finely disseminated in a stratiform manner in the silicified rock. Fine-grained pyrite is commonly disseminated in the silicified siltstone and sandstone where oxidation has not occurred. Contacts between siltstone and arkose
beds seem to be more favorable and carry higher gold grades. In places, beds of tuff and tuffaceous siltstone appear to be particularly favorable hosts for higher-grade mineralization that lacks associated veins.
Newmont and other later operators referred to the third style of gold–silver mineralization as “clay matrix breccia,” bodies of which may be
more prevalent in the lower portion of the higher-grade core of the deposit. These bodies are interpreted to extend at near-vertical angles up and down into the surrounding, low-grade gold-silver envelope. Clay matrix breccias are mainly of
clast-supported types and contain sub-rounded to sub-angular, sand- to boulder-sized clasts of silicified and/or veined arkose and siltstone with minor amounts of clay and iron-oxide minerals between the clasts. In drill core, clay matrix breccia
intervals are intersected over lengths of as much as several tens of feet, but their
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true thickness and exact orientations are poorly understood, in part because their margins are commonly irregular-to-gradational and not planar, except where structural fabrics related to fault
movement are evident. In some cases, it is difficult to discern where clay matrix breccias end and similar fault-related breccias begin. In some places the two are possibly genetically related.
Clay matrix breccias cut—and are therefore paragenetically later than—the silicification and veins. One interpretation is the clay matrix breccias
formed by explosive releases of over-pressured water vapor through faults and fractures during boiling in the waning stages of the hydrothermal activity.
6.4.3.2
Lower Grade Envelope
Lower-grade mineralization, generally less than 0.03 oz/ton Au, envelopes the higher-grade core and extends outwards as stratiform mineralized lenses (see
Figure 11-1 through Figure 11-4). There are very few visible chalcedonic veins. The gold and silver are inferred to be disseminated within the silicified arkose and
siltstone units. Contacts between arkose, siltstone, and sinter appear to have been preferentially mineralized, and beds of tuff and tuffaceous siltstone also were favorable sites for mineralization. Low-grade mineralization is also present in
numerous intervals of silica sinter. However, not all sinter intervals are mineralized. Sinter-hosted mineralization may be disseminated or within fractures where the sinter has been structurally disrupted.
6.5
Deposit Types
The geological setting, hydrothermal alteration, styles of gold-silver mineralization, and close spatial and timing associations of the mineralization with
siliceous-sinter deposition indicate that Grassy Mountain is an example of the hot-springs subtype of low-sulfidation, epithermal, precious-metals deposits. The Grassy Mountain deposit is characterized by stacked sinter terraces that demonstrate
hydrothermal fluids vented at the paleosurface concurrent with lacustrine and intermittent fluvial sedimentation. At a depth of 300 ft, the main sinter at Grassy Mountain is underlain by a zone of intense silicification, within which is located the
core of the deposit that is the focus of this report.
Figure 6-4 shows a conceptual, schematic section of a
low-sulfidation epithermal system and its variable form with increasing depth, and the typical alteration zonation, which include the distribution of sinter, a blanket of steam-heated advanced argillic alteration, and water-table silicification
(Buchanan, 1981; Sillitoe, 1993).
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Figure
6-4: Conceptual Hot-Springs Epithermal Deposit Model
Source: Buchanan, 1981
In
the case of Grassy Mountain, the broader lower-grade mineralization extends up to and overlaps multiple, stacked deposits of sinter, reflecting near-surface epithermal mineralization as the sedimentary sequence accumulated.
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7
EXPLORATION
7.1
Exploration
In early 2017, Paramount commissioned an exploration review of the Grassy Mountain project data to evaluate and define exploration drilling opportunities for
potential expansion of the known mineralization. This study focused on the area within the Grassy Mountain claims group controlled by Paramount and was carried out and reported by RESPEC (Weiss, 2017).
RESPEC first compiled and evaluated geological and geophysical maps, soil and rock-chip assay data, and aerial images from files supplied by Paramount. During
March 2017, RESPEC reviewed RC drill cuttings and core, drill logs, paper maps, cross-sections, and other files at Paramount’s office in Vale. As part of this review, field traverses were made throughout the Grassy Mountain claim group to
better understand the geology, rock geophysical response, and effects of hydrothermal alteration.
Based on the field traverses, RESPEC noted the
high-potassium zones shown by the Newmont airborne radiometric data are likely controlled by abundant potassium-bearing clasts within exposed stratigraphic units of the Grassy Formation and concluded that they are not the result of extensive
potassic alteration. District patterns of low total magnetic intensity visible in the Newmont airborne magnetic maps also appear closely related to stratigraphy and regional faults of the Oregon-Idaho graben rather than major zones of hydrothermal
alteration.
Zones of high resistivity defined by the 2012 CSAMT survey correlate in part with the thick volume of silicified rocks that host the Grassy
Mountain gold deposit (refer to Section 5). Drill data, including RC chips, show the resistivity high that extends southwest from the deposit toward the Crabgrass deposit and the outlying resistivity high at the Wood area are not the result of
extensive silicification (Weiss, 2017). In these areas, the CSAMT high resistivity response may be from the underlying Kern Basin Tuff (Tkt) and rhyodacite of Butterfly Hill (Trd) units.
Weiss (2017) identified four drill targets within the immediate area of the Grassy Mountain deposit and recommended them for limited expansion drilling.
Drilling conducted to test these targets is summarized in Section 7.2.2. These near-mine targets have significant uncertainties in their locations due to a lack of confidence in the precise locations, dips, amount of displacement, and timing of
the Apache–Coyote and Gopher faults and the northeast-trending fault in the North Spur, all of which are potentially mineralized structures. Nevertheless, Weiss (2017) justified these targets based on their proximity to the proposed
underground mine and the opportunity they presented to expand known mineralization, even if only incrementally. Two holes drilled in 2018 as a preliminary test of the North Spur target returned anomalous values.
Weiss (2017) also recognized two separate targets in the outlying Wood prospect as having the potential to host structurally controlled vein or stockwork
mineralization.
In addition, Weiss (2017) recommended additional surface work to further define exploration drill targets. This included expansion
of the 2012 CSAMT coverage to better understand the subsurface at the Crabgrass, Bluegrass, North Bluegrass, Ryegrass, and Dennis’ Folly areas and infill soil sampling and trenching at the large geochemical anomaly north of Snake Flats.
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In October 2018, Paramount contracted Precision GeoSurveys of Langley, BC, Canada to fly helicopter-borne
aeromagnetic and radiometric geophysical surveys over the Grassy Mountain claim group. Precision GeoSurveys flew 734 line-miles with an Airbus AS350 helicopter at 50-meter spacings and a heading of 090°/270°; tie lines were flown at
500-meter spacings at a heading of 000°/180°. The results of this survey show the Grassy Mountain deposit lies within a large magnetic low (Figure 7-1). Magnetic highs outline the extents of intrusive
rocks and basaltic units.
Figure
7-1: 2018 Aerial Magnetic Survey of Grassy Mountain Area
Source: Paramount, 2018 and modified by RESPEC, 2026
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7.2
Drilling
Drilling at the Grassy Mountain claim block is summarized in Table 7-1 and shown in Figure 7-2.
Table
7-1: Grassy Mountain Claim Block Drilling Summary
Year
Company
# Holes
Hole Type
Length (ft)
Area
1987–1991
Atlas
193
RC
154,963
Grassy Mtn
1989–1991
Atlas
5
Core
4,153
Grassy Mtn
1989–1991
Atlas
5
RC & Core
3,502
Grassy Mtn
1987–1991
Atlas
187
RC
62,895
Outlying
Prospects
1987–1991
Atlas
10
RC
1,884
Water wells
1992–1996
Newmont
13
Core
13,101
Grassy Mtn
1992–1996
Newmont
2
RC & Core
1,909
Grassy Mtn
1998
Tombstone
4
RC
3,145
Grassy Mtn
1998
Tombstone
6
RC & Core
4,926
Grassy Mtn
2011
Calico
3
Core
2,531
Grassy Mtn
2011–2012
Calico
10
RC
8,518
Grassy Mtn
2012
Calico
4
RC
2,585
Outlying
prospects
Historical Total
442
264,112
2016–2017
Paramount
3
RC
1,140
Grassy Mtn
2016–2017
Paramount
3
Core
1,933
Grassy Mtn
2016–2017
Paramount
24
RC & Core
19,907
Grassy Mtn
2018
Paramount
2
RC
1,600
North Spur Target
2019
Paramount
2
Core
931
Geotechnical
Paramount Total
34
25,511
All Drilling Total
476
289,623
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Figure
7-2: Locations of Drill Holes Within the Grassy Mountain Claims
Group
5.2.3.6
Wood
Source: RESPEC, 2026
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The project database includes a total of 264,112 ft drilled by four historical operators from 1987 through
2012 in 442 drill holes. From 2016–2019, Paramount drilled 34 holes for a total of 25,511 ft to bring the total drilled within the claims group to 476 holes and 289,623 ft. Approximately 77% of the footage drilled was at and adjacent to the
Grassy Mountain deposit area. Most of the holes at the Grassy Mountain deposit area were drilled entirely by RC (77% of the total footage). Holes drilled using core methods account for about 12% of the footage drilled in the deposit area, and holes
drilled with RC pre-collars and core tails account for about 11% of the total. Figure 7-3 shows the locations of the holes drilled in and near the Grassy Mountain deposit area. Figure 7-2 includes the collar locations of holes drilled to test outlying prospects within the Grassy Mountain claim block. The results of drilling at the outlying prospects are summarized in Section 5.2 and
Section 5.3.
Within the Grassy Mountain deposit area, approximately 80% of the holes were drilled vertically or within 3.0° of vertical.
Approximately 69% of the core and core-tail holes were inclined at angles less than -80°. Overall results of drilling within the Grassy Mountain deposit are summarized with representative cross-sections presented in Section 11.7.1. The
locations of these cross-sections are shown in Figure 7-3. At the outlying prospects—where all the drilling was done with RC methods—approximately 98% of the holes were vertical. Outside the Grassy
Mountain deposit area, the median hole depth was 300 ft.
In addition to the holes discussed above, three short, vertical core holes, for a total of 438
ft, were drilled in 2018 to the east of the Grassy Mountain deposit. These holes obtained samples of unaltered and unmineralized basalt that is a potential source of aggregate and mine-backfill material. These samples were used in various
geotechnical and geochemical evaluations. Four groundwater-monitoring wells (GM18-31 through GM18-34) drilled by Paramount in 2018 are not included in the drilling summarized in Table 7-1 or on Figure 7-2 and Figure 7-3.
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Figure
7-3: Locations of Holes Drilled in the Grassy Mountain Deposit Area
Source: RESPEC, 2026
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7.2.1
Historical Drilling, 1987-2012
7.2.1.1
Atlas, 1987–1992
In early 1987, Atlas mobilized a small track-mounted rig to drill six holes in two target areas. Drill hole 026-004 intercepted 80 ft of mineralization
averaging 0.021 oz/ton Au. Atlas completed a follow up five-hole drill program in the spring of 1988. Drill hole 026-009 is considered the Grassy Mountain deposit discovery hole—it intersected 145 ft of mineralization that averaged 0.075
oz/ton Au. By the end of 1991, Atlas had drilled 227,397 ft in 400 holes. Of the total, Atlas drilled 13 holes as water wells and 187 holes at outlying prospects.
Eklund Drilling Company of Elko, Nevada drilled Atlas’s RC holes using Ingersoll Rand TH-60 and RD-10 truck-mounted drills with a nominal hole diameter
of 51⁄4 inches (Lechner, 2007). Atlas sampled the RC cuttings at 5-ft intervals. Twenty-three of the RC exploration holes were drilled to at least 1,000 ft in
depth. (All of the 1,000+-foot holes are in the Grassy Mountain deposit area.) Atlas’s RC drilling was “almost invariably” done dry, because groundwater wasn’t encountered above 750-ft depths except for some locally perched
water intersected along the northern portions of the deposit. Because the deposit is strongly silicified, drilling penetration rates were slow and caused excessive bit wear. Drilling in certain areas was difficult because of tight hole conditions
and caving of rubble zones. In many cases, historical documentation is not sufficient to determine whether a particular hole was drilled dry or wet.
Atlas drilled 10 core holes at Grassy Mountain to confirm the high-grade mineralization identified by RC drilling, obtain samples for metallurgical testwork,
and collect geotechnical data. Longyear, Incorporated (Longyear) drilled two confirmation core holes as NQ (1.875 inch) angle holes. Boyles Brothers drilled five core holes as vertical PQ (3.345 inch) diameter holes specifically to obtain
sample material for metallurgical testing (these holes were pre-collared with RC). Boyles Brothers also drilled three geotechnical holes. Assay records indicate that Atlas sampled the confirmation holes on intervals ranging from 0.5 to 7.5 ft in
length, with an average sample length of 4.5 ft. RESPEC is uncertain whether the core was mechanically split in half or sawed in half for sampling. Atlas shipped the whole core from the metallurgical holes to Hazen Research Inc. for metallurgical
testwork and logged the geotechnical holes for various geotechnical parameters such as rock quality designation (RQD), fracture frequency, etc.
The Atlas
geologist assigned to each drill rig was responsible for the placement of the rig, drilling and sampling methods, hole depths, and lithologic logging.
The Atlas drilling discovered and completed the initial delineation of the Grassy Mountain deposit. Atlas also discovered and completed all drilling of the
Crabgrass deposit.
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7.2.1.2
Newmont, 1994
In 1994, Newmont drilled 15 angled core holes (including a wedge drilled off the first hole), and pre-collared two of the last three core holes with RC.
Longyear of Spokane, Washington conducted this drilling, which totaled 15,010 ft. All these holes were drilled with HQ (2.5 inch) diameter core except for six drill holes in which poor ground conditions forced the HQ core to be reduced to NQ-size.
The RC pre-collars were sampled over intervals of 5.0 ft. Newmont sawed approximately 90% of the core in half for sampling and mechanically split the other 10% in half.
Newmont determined that steep, southeast-dipping quartz–chalcedony–adularia veins hosted the high-grade gold. They inferred the steep southeast
dip by comparing vein/core intersection angles from southeast-directed holes to those in northwest directed holes and also inferred that the high-grade gold mineralization had a relatively sharp base at an elevation of 3,000 to 3,100 ft.
7.2.1.3
Tombstone 1998
In 1998, Tombstone drilled six core holes with RC pre-collars and four complete RC holes that totaled 8,071 ft of drilling at the Grassy Mountain deposit.
Dateline Drilling Incorporated (Dateline) from Missoula, Montana performed all of Tombstone’s RC drilling. Tombstone collected RC samples over 2.5 and 5.0-ft intervals, with both interval lengths sometimes used in the same drill hole. They
conducted the RC drilling wet, as water and mud was used for hole conditioning. Ray Hyne Drilling of Winnemucca, Nevada, performed the core drilling. Tombstone sawed approximately 80% of the core in half for sampling and mechanically split the
remainder in half.
Tombstone concentrated their drilling in the higher-grade core of the deposit, aiming to better define the higher-grade
mineralization. However, the Tombstone results did not include the very high-grade component of the Grassy Mountain mineralization (>2 oz/ton Au) encountered in previous Atlas RC and Newmont core holes (French, 1998). French (1998) theorized
that the lack of very high-grade intersections might have been due to the program’s drilling and related sampling problems. French (1998) recommended using a more powerful RC rig that could better handle poor ground conditions and would
require less hole reaming and conditioning, which would allow uninterrupted drilling and sample collection.
7.2.1.4
Calico 2011-2012
Calico commenced drilling at the Grassy Mountain deposit in August 2011 and drilled three core holes using a modified track-mounted LF-90 core drill operated
by Marcus and Marcus Drilling Company, of Post Falls, Idaho (Marcus and Marcus). Marcus and Marcus drilled HQ diameter core using a triple-tube core recovery barrel. Operating 24 hours per day, Marcus and Marcus drilled an average of 39 ft per day
and completed 2,530.5 ft of drilling.
In October 2011, a truck-mounted Ingersoll-Rand TH-75 drill operated by Boart Longyear, of South Jordan, Utah,
began RC drilling at the Grassy Mountain property. The TH-75 drill utilized a cyclone wet splitter for sample collection, with an approximate 40% split retained in the sample bag. Drill cuttings passed through a cyclone and the splitter then divided
them into three streams: one for sampling, one for logging and retention for reference, and the third was discarded to the sump. The Calico geologist site placed a portion of the sample collected for logging into a plastic chip tray labeled with the
hole number and the depth from which the sample was taken. The drill helper collected one
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sample for each 5-ft interval in bags pre-labeled with the sample number under supervision by Calico’s site geologist. The drill helper sealed each sample bag at the drill site. The sample
bags remained unopened until they reached the analytical laboratory. After each 20 ft length of drill rod was added to the drill string, Boart Longyear cleaned the hole of material which may have descended while they installed the new section
of pipe. The RC drill operated on a single 12-hour daily shift. A Calico on-site geologist monitored the drilling and sample collection, logged the drill cuttings, and collected and stored a portion of the drill cuttings for future reference. The RC
drill rig completed nine holes at the Grassy Mountain deposit area totaling 7,668 ft.
Calico allowed their 2011 RC samples to drain at the drill site
prior to shipment for assay. Samples received at the assay laboratory had an average weight of 20 lb.
During June 2012, Calico drilled a total of 3,435
ft in five RC holes—one in the Grassy Mountain deposit area, one in the Wheatgrass area, one at the Wood area, and two at the Wally area. Drill contractor Leach Drilling of Dayton, Nevada, performed the work using an Ingersoll-Rand DM25/RC
track-mounted rig. Leach Drilling used a cyclone wet splitter for sample collection and retained approximately 40% of each sample in a sample bag for analysis. Calico’s June 2012 sampling procedures were the same as those used in 2011. The
drill operated on a single 12-hour daily shift. An on-site Calico geologist monitored the drilling and sample collection, logged the drill cuttings, and collected a portion of the drill cuttings for future reference. Calico completed the 2012 drill
program on June 28.
Calico’s 13 holes drilled at the Grassy Mountain deposit area increased the drill density within the higher-grade core of
the deposit. Calico’s three core holes provided additional information regarding higher-grade mineralization. The hole drilled at Wheatgrass returned results consistent with existing holes in the target area. The hole drilled at the Wood
target was drilled almost 450 ft from the nearest drill hole and returned only very low-grade intersections. The first hole drilled in the Wally area unsuccessfully tested the western extension of previously defined mineralization. The second Wally
drill hole returned similar results to the existing Wally drill holes and therefore confirmed the extension of this low-grade mineralization about 200 ft to the north.
7.2.2
Paramount 2016–2019
From 2016–2019, Paramount conducted infill, geotechnical, hydrological, and metallurgical drilling at Grassy Mountain. Paramount’s drilling focused
on the central higher-grade core of the deposit and significantly improved Paramount’s knowledge of the continuity and styles of mineralization within the core zone. It also provided samples for geotechnical and metallurgical testing.
Paramount’s drill results made an important contribution to the estimation and confidence in the modeling of the Grassy Mountain gold and silver resources presented in Section 11 of this technical report summary.
In 2016 and 2017, Paramount drilled 22,980 ft in a total of 30 holes within the higher-grade core of the Grassy Mountain deposit. The goals of this drilling
program included: (i) verifying the historical drill data, particularly the historical RC holes; (ii) increasing the quantity of drill core derived from the higher-grade portion of the deposit; (iii) obtaining better definition of the
controls and extents of the higher-grade mineralization; and (iv) obtaining drill core for detailed geotechnical logging and metallurgical testing. In 2018, Paramount drilled two RC holes at the North Spur target, located a short distance to
the north of the Grassy Mountain deposit. In 2019, Paramount drilled two geotechnical core holes within the lower-grade peripheries of the Grassy Mountain deposit. The 2019 drilling included a short, 100-ft vertical hole near the planned mine portal
and a deeper 831-ft hole drilled at -70° to penetrate an area of the planned underground access ramp. Representative cross-sections of the drilling are in Section 11.7.1. The cross-section locations are shown on Figure 7-3.
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Historical core drilling programs often experienced significant problems due to poor ground conditions,
particularly from the uppermost portion of the deposit through to the bottom of the upper sinter package. Therefore, Paramount began to pre-collar the core holes with RC to depths of approximately 400–500 ft, then core drill through the
higher-grade core of the deposit.
Paramount contracted Major Drilling America Inc., of Salt Lake City, Utah (Major Drilling or Major) for both the RC and
core drilling. Major drilled RC pre-collars with a Schramm T450GT track-mounted drill operated on a single 12-hour daily shift. Major used a 61⁄2 inch diameter RC
bit to the planned pre-collar depth and then set 41⁄2 inch steel casing for the entire length of the hole. The RC drill rig moved to the next RC pre-collar location
and a core rig drilled the remainder of the hole (as discussed below).
During the RC drilling, Major Drilling injected small amounts of water down the
hole to control dust emissions. Major Drilling’s sampling assistant collected RC samples at nominal 5-ft intervals via a cyclone rotary splitter and center discharge tube into 20-inch by 24-inch sample bags that were pre-numbered by Paramount
geologists or geotechnicians. Typical samples weighed approximately 15–20 lb for each sample interval. The Major Drilling sampling assistant monitored the drilling, performed the sample collection, and collected and stored a portion of the
drill cuttings in plastic chip trays for future reference and logging. Paramount’s onsite geologist trained the sampling assistant on the first seven RC pre-collars.
Paramount and/or Major Drilling’s sampling assistant collected duplicate RC samples at the rate of approximately one per 40 regular sample intervals.
For duplicate samples, they collected the primary sample from the center discharge tube of the rotary splitter and collected the duplicate sample from the side discharge tube of the rotary splitter. (At no time did they use a “Y-type”
splitter to collect duplicate samples.)
Major Drilling completed the core drilling with two track-mounted drills: a Boart Longyear LF-90 drill and a
Boart Longyear LF-230 drill. Both rigs drilled HQ diameter core using a triple-tube type core barrel. Two-man crews operated the core drills 24 hours per day on two 12-hour shifts with a drill foreman also on site. A single water truck and driver
hauling water from a well approximately one mile north of the drilling area supplied adequate water for the two drills.
Major began drilling the first RC
pre-collar in November 2016 and completed seven RC pre-collars totaling 2,695 ft during the year. In 2016, core totaling 3,078 ft was drilled in six holes. Paramount suspended drilling from mid-December 2016 through early March 2017. During March,
April, and May of 2017, Major Drilling drilled 20 RC pre-collars totaling 8,556 ft. From March through June of 2017, Major drilled 8,651 ft of core in 21 holes. Table 7-2 shows the footages drilled by
pre-collar RC and core methods.
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Table 7-2: Paramount 2016–2019 RC Pre-Collar vs. Core
Lengths
Drill Hole
Pre-Collar
RC From (ft)
Pre-Collar RC To
(ft)
Core From (ft)
Core To (ft)
Total RC
Drill
Hole
Pre-Collar RC
From (ft)
GM16-01
0
380
—
—
380
0
Stuck hammer
GM16-02
0
400
400
742
400
342
GM16-03
0
380
380
785
380
405
GM16-04
—
—
0
744.5
0
744.5
Geotechnical hole
GM16-05
0
360
360
618
360
258
GM16-06
0
400
400
731
400
331
GM17-07
0
391
391
850.5
391
459.5
GM16-08
0
375
—
—
375
0
Twisted off rods
GM16-09
0
400
400
795
400
395
GM17-10
0
400
400
822
400
422
GM17-11
0
385
—
—
385
0
Stuck hammer
GM17-12
0
395
395
689
395
294
Re-drill of
GM16-08
GM16-13
—
—
0
438.5
0
438.5
Twisted off rods
GM16-14
—
—
0
750
0
750
Geotechnical hole
GM17-15
0
320
320
780
320
460
GM17-16
0
480
480
923
480
443
GM17-17
0
480
480
929.5
480
449.5
GM17-18
0
450
450
884.5
450
434.5
GM17-19
0
450
450
857.5
450
407.5
GM17-20
0
380
380
856
380
476
GM17-21
0
460
460
832
460
372
GM17-22
0
500
500
953.5
500
453.5
GM17-23
0
400
400
956
400
556
GM17-24
0
450
450
896
450
446
GM17-25
0
400
400
887
400
487
GM17-26
0
520
520
875
520
355
GM17-27
0
440
440
772
440
332
GM17-28
0
420
420
862
420
442
GM17-29
0
440
440
800
440
360
GM17-30
0
400
400
810
400
410
GM18-35
0
800
—
—
800
0
North Spur
GM18-36
0
800
—
—
800
0
North Spur
GM19-37
—
—
0
831
0
831
Geotechnical hole
GM19-38
—
—
0
100
0
100
Geotechnical hole
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Major Drilling averaged 142 ft of RC drilling per 12-hour shift and 31.1 ft per drill, per 12-hour shift, for
core drilling. Three of the RC pre-collars encountered extremely bad ground conditions that led to premature terminations of the holes and precluded the drilling of core tails.
The drilling program achieved all the goals summarized above. Beyond obtaining core for detailed geotechnical logging and metallurgical testing, the drill
core aided in furthering the understanding of the deposit’s geology and confirmed many of Newmont’s conclusions. This understanding formed the base from which the resource model was constructed. Finally, the results of the Paramount
drilling program have aided in the verification of the historical data (see the discussion of estimating with and without Paramount drill data in Section 9.1.4).
The results and interpretations of the geotechnical and hydrological data derived from the Grassy Mountain deposit area drilling programs are discussed in
Section 13.2 and Section 13.3.
7.3
Drill-Hole Collar and Down-Hole Surveys
For the Atlas drilling, Apex Surveying from Riverton, Wyoming, surveyed the collar locations using a total station. Most holes were not surveyed for down-hole
direction and deviation, except four RC holes and all the core holes, which were surveyed using an Eastman down-hole camera (Lechner, 2007).
RESPEC does
not know whether Newmont surveyed their collar locations. Newmont had Scientific Drilling from Elko, Nevada, perform down-hole deviation surveys of their holes. Newmont’s handwritten “Drill Hole Summary” sheets indicate that
Scientific Drilling surveyed their holes using a “gyro” instrument.
There are no written records regarding the procedures for surveying the
Tombstone collar locations (Lechner, 2007). Silver State Surveys of Elko, Nevada, reportedly performed down-hole deviation surveys using a gyroscopic survey tool, but Paramount’s archives contain no written records. No down-hole survey data
are available for three of the Tombstone drill holes.
Until Calico’s involvement in the project in 2011, project coordinates were based on a local
grid established by Atlas. All Calico and subsequent drill-hole collar surveys were collected directly in UTM coordinates. Section 9.1includes a discussion on the transformation of historical mine-grid collar locations into UTM coordinates.
During 2011 and 2012, Calico personnel surveyed drill collar locations using hand-held Garmin GPS units with a horizontal accuracy on the order of
±10 ft. Later, the collar locations were surveyed with a Trimble, survey-grade GPS to ±0.1 ft. Drill holes were marked in the field with a lath and/or stake.
Marcus and Marcus surveyed the 2011 core holes for down-hole directional deviation using a REFLEX EZ-Track survey instrument to obtain multi-shot readings.
International Directional Services (IDS) surveyed the 2011 RC holes for down-hole deviation using a Goodrich-Humphrey surface-recording gyroscopic system. Deviations from planned orientations were generally on the order of 3° for core and RC
holes, although some of the RC holes deviated by up to 6° in azimuth and 8° in dip.
Down-hole surveys were not performed in the first four 2012
RC holes. IDS surveyed the final 2012 hole, CAL12R17, using a Goodrich-Humphrey surface recording gyroscopic system.
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During Paramount’s 2016–2017 drilling program, Atlas Land Surveying of Fruitland, Idaho, surveyed
the Paramount drill-collar locations and many of the historical drill collars (see Section 9.1.1). The coordinates for the 2018 and 2019 holes were determined by handheld GPS. The owner of Atlas Land Surveying, Dean J. Coon, is a Registered
Professional Land Surveyor (Oregon 65687LS) and was responsible for the field work, data processing, and reporting. Atlas Land Surveying completed all 2018–2019 survey work using real-time kinematic (RTK) surveying techniques with Topcon Hiper
V GPS Receivers. In RTK mode, the stated accuracy of the measurements is within 10 mm ±1 mm for horizontal data and 15 mm ±1 mm for vertical data. Atlas Land Surveying collected static data in the field and then submitted it to the
National Geodetic Service Online Positioning User Service to derive accurate geodetic coordinates tied to the National Spatial Reference System. Using these coordinates, a survey measurement adjustment program, “StarNET”, processed the
RTK data to determine the final coordinates for the located points, then projected to the Universal Transverse Mercator grid using the NAD83 datum in units of U.S. Survey feet.
Down-hole deviation surveys were obtained from 25 of the 2016 and 2017 Paramount drill holes, the two holes drilled in 2018, and the deeper of the two
geotechnical holes drilled in 2019. IDS of Elko, Nevada, performed these surveys using a Goodrich surface-recording gyroscopic system (SRG). The SRG is capable of mapping the direction of boreholes and is unaffected by steel pipe or local
magnetic-field anomalies. Five of the 2016–2017 drill holes had blockages, such as lost or stuck pipe, casing, or core barrel, that prevented down-hole surveys.
7.4
Sample Quality
7.4.1
Core Samples
Due to the presence of visible gold in the drill core, Newmont decided to evaluate the potential for unrepresentative loss of gold in the splitting of drill
core for sampling. During the sampling of their first hole (GMC-001), Newmont collected the minus 10 mesh fines produced during the sawing of drill core into halves for each sample and weighed and assayed them separately (Jory, 1993). Jory
(1993) reported that the mean of the gold assays of the 171 samples of saw fines collected was 86% higher (0.044 versus 0.024 oz/ton Au) than the associated half-core samples sent to the laboratory. Jory (1993) noted that since the saw
fines accounted for less than 0.5% of the total sample weight, sampling of the saw fines was discontinued. However, Newmont did take 38 additional saw-fines samples for hole GMC-001-9, a core wedge from GMC-001, for which the assay certificate is
available. The average of the saw-fines assays is 0.438 oz/ton Au and the mean of the half-core assays is 0.143 oz/ton Au. Newmont did not obtain silver assays for any of their drill samples. The high bias in the saw fines relative to the
half-core samples is present at all gold grades, but it increases as the grade increases.
While the unrepresentative loss of gold to the saw fines is not
material due to the small amount of these fines relative to half-core samples, these data suggest the potential unrepresentative loss of gold to fines generated by other means. One such possibility is in fines that collect in core boxes from broken
intervals, which clearly warrant careful collection and splitting along with the sawing of competent pieces of core. Newmont brushed fines out of the core boxes for each sample interval and split the fines into halves, with one half added to the
sample bags of sawed core sent to the assay laboratory and the other half bagged and returned to the core boxes.
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Fines can also be lost below the surface during core drilling. To evaluate this possibility, RESPEC conducted
a sample integrity study to evaluate the relationship between geotechnical data (core recovery and RQD) collected during the logging of the core and gold grades. Figure 7-4 summarizes the relationship between
gold grade and RQD for all Grassy Mountain core holes for which RQD data are available.
Figure
7-4: Gold Grade vs. RQD
Source: RESPEC, 2018
Each
blue bar in the graph includes data within a 20% RQD bin, as indicated on the x-axis (RQDs of 100% and greater report to the “100” bin). The heights of the bars are indicative of the average grade of all intervals within each recovery
bin, as shown on the y-axis of the left-hand side of the graph. The total number of RQD intervals in each recovery bin is displayed by the orange line, with the scale provided by the y-axis on the right-hand side of the graph.
Except for the lowest RQD bin, there is a consistent correlation between RQD and gold grade: gold grades increase as RQD decreases. This negative correlation
is at least in part due to the relationship of higher-grade mineralization with highly fractured zones that yield low RQD values. In some deposits, unrepresentative loss of soft, clay-rich, and relatively unmineralized material from the recovered
drill core occurs in low RQD zones, which would lead to increased grades in the recovered samples of core. However, the Grassy Mountain mineralization of all grade ranges is associated with uniformly strong silicification, so this mechanism of
apparent grade increases is unlikely. The negative correlation between RQD and gold grade does not provide evidence for the possibility of losing gold related to fines during drilling. However, the potential for losses cannot be definitively ruled
out.
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RESPEC extensively reviewed RQD measurements used in the sample integrity analysis and modified the data,
e.g. adjusted RQD values over 100%, to assure their validity. RESPEC did not validate the bulk of the core recovery data, so these data may contain many inconsistencies that should be resolved. The relationship between recovery and gold grade for
two Paramount holes is summarized in Figure 7-5. No clear trend is evident at core recoveries of 60% and greater. Gold grades decrease with decreasing recoveries for core recoveries lower than 60%. However,
the number of recovery intervals in each bin is relatively low and likely insufficient to support definitive conclusions.
Figure
7-5: Gold Grade vs. Core Recovery
Source: RESPEC, 2018.
7.4.2
RC Samples
Due to the nature of RC drilling, contamination of drill cuttings from intervals above the drill bit is a concern, especially when groundwater is encountered
or fluids are added during drilling. The Atlas reportedly drilled RC holes dry unless groundwater was intersected, while Tombstone, Calico, and Paramount drilled their RC holes entirely wet. Comments on geologic logs and other historical
documentation suggest that the water table at Grassy Mountain lies near the base of the higher-grade core of the deposit, with “perched” groundwater noted in a few holes at much higher elevations.
Careful inspection of the geological context of RC drill results can sometimes detect down-hole contamination (e.g., anomalous to significant assays returned
from samples from post-mineral units), by comparing RC results to adjacent core holes, and by examining down-hole grade patterns.
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Cyclic down-hole grade patterns are evident in some of the RC holes at Grassy Mountain. These cycles consist
of elevated gold grades (relative to adjacent samples) in every fourth 5-ft sample, which corresponds with the first sample collected after a 20-ft drill rod change. In a classic case, the first sample yields the highest grade for a given drill rod,
while the following three samples gradually decrease in grade. This “decay” pattern in grade is caused by the accumulation of mineralized material (derived from some level in the hole above the drill bit) at the bottom of the hole as the
drilling pauses to add a new drill rod to the drill string. When drilling resumes, the first sample has the greatest amount of contamination, and the successive samples are gradually “cleaner” as the accumulated contamination decreases.
This cyclical pattern is detectable only in barren or very weakly mineralized rock. Even in cases where low-grade cyclic gold contamination would have a minimal impact on resource estimation, its presence suggests that similar, and possibly more
serious, unrecognizable contamination may have occurred higher in the hole within a mineralized zone.
Atlas did not believe down-hole contamination in
Grassy Mountain drilling was a “significant or consistent problem,” but did recognize that the bottom of hole 026-034 was potentially contaminated over a 200-ft interval. During the resource modeling and related detailed review of the
project data, RESPEC identified 21 drill holes suspected of having down-hole contamination of precious metal values, primarily based on the cyclic pattern described above. These suspect intervals are all at the lowermost portions of holes. They were
either excluded from mineral domain modeling or were used to model but explicitly excluded from use in the resource estimation.
7.5
Summary Statement
RESPEC believes that the drilling and sampling procedures provided representative samples of sufficient quality for use in the resource estimations discussed
in Section 11. RESPEC is unaware of any sampling or recovery factors that have not been addressed that would materially impact the estimate of mineral resources discussed in Section 11.
Down-hole drilled lengths of the higher-grade gold and silver portions of the deposit, some of which are oriented at high angles, could significantly
exaggerate true mineralized thicknesses in cases where steeply dipping holes intersect steeply dipping mineralization. A very high percentage of the Atlas holes were drilled vertically. RESPEC carefully evaluated the possible effects of exaggerated
down-hole lengths on the estimation of current resources and believes the model appropriately represents the higher-grade volumes.
The average down-hole
length of the sample intervals used directly in the estimation of the resource’s gold and silver grades is 4.76 ft, with a minimum length of 0.3 ft and a maximum of 12 ft. RESPEC considers these sample lengths appropriate for the Grassy
Mountain deposit.
Only four of the 177 Atlas RC holes that directly contribute assay data to the resource estimation were surveyed for down-hole
deviation. The four Atlas RC holes that were surveyed deviated from 14 to 35 ft horizontally from the drill collar positions to the distinct lower contact of the higher-grade zone (see Section 11), which lies approximately 800 ft below the
surface. The average horizontal deviation is 22 ft. In consideration of the block size of the resource model (5 x 10 x 10 ft; model x, y, z) and other factors related to the resource estimation, RESPEC does not consider the
demonstrated magnitude of deviation to be a significant issue.
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8
SAMPLE PREPARATION, ANALYSES, AND SECURITY
8.1
Introduction
This section summarizes all information RESPEC knows relating to sample preparation, analysis, and security, and quality assurance and quality control (QA/QC)
procedures employed to amass the Grassy Mountain drilling data. RESPEC either supervised the compilation of information from historical records as cited, or received it from Mr. Michael McGinnis, Paramount’s Project Manager.
8.2
Sample Preparation, Analysis and Security
8.2.1
Atlas 1987-1992
Atlas split the RC samples at the drill site to weigh between 8–15 lb (Atlas’s RC samples averaged approximately 12 lb) Atlas collected their RC
samples in 10-inch by 17-inch olefin sample bags. At all times, an Atlas geologist was stationed at the drill rig with the drill samples. Atlas split wet RC cuttings using a variable wet-cone splitter positioned below the cyclone and split dry
cuttings under the cyclone with a Jones splitter. Project geologists delivered the samples to a secure storage facility in Vale at the end of each shift. Chemex Analytical Laboratories (Chemex) personnel routinely picked up the samples from the Vale
storage facility and delivered them to their preparation facility in Boise, Idaho, where Chemex dried the samples at 100°C and then cone-crushed them to minus 1/8 inch. Chemex took 300-g subsamples using a Jones riffle splitter, then reduced
these subsamples to 95% passing 100 mesh using a ring and puck pulverizer. They stored coarse-reject materials in storage at the Boise facility for possible future use. Chemex shipped the 300-g pulps to their assay facility in North Vancouver,
Canada, where they assayed for gold and silver using 30-g aliquots analyzed by fire assay fusion, primarily with an atomic absorption (AA) finish.
RESPEC
does not know what type of certification Chemex had in 1987–1990, if any, but Chemex was a well-known commercial assayer that was independent of Atlas.
8.2.2
Newmont 1992-1996
Jory (1993) reported that Newmont cut their core into halves at the Vale field office with vein apices oriented perpendicular to the saw blade. For
material too fine to be swanned, Newmont geologists carefully swept out the core boxes for each sample interval, split the material in half using a Jones splitter, and recombined one half with the half-core sent for assaying. Newmont core boxes in
Paramount’s possession include core fines inside zip-lock plastic sandwich bags—presumably representing the remaining half-split of fine material from each sample interval.
According to Jory (1993), Rocky Mountain Geochemical Corporation (RMGC) picked up the core samples from the Atlas storage facility in Vale and delivered them
to the RMGC facility in Salt Lake City, Utah, where RMGC prepared and analyzed the samples. A copy of a Newmont report that lacks a title page, states that, “Coarse gold (up to 500 microns) problems necessitated careful sample prep
procedures for Grassy Mountain core.” RMGC dried the samples at 100°C, crushed them to minus 10 mesh, split them in half with a Jones riffle splitter, and coarse pulverized them to minus 48 mesh. RMGC ring-pulverized a 200-g split
of the minus 48 mesh material to a nominal, minus 150 mesh particle size, and fire assayed a 30-g aliquot with gravimetric and AA finishes.
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Newmont requested screen-fire assays from RGMC on 20 samples from drill holes GMC-001 and -002, for which
original gold assays exceeded 0.20 oz/ton Au.
RESPEC has no documentation regarding the sample security methods Newmont employed during their drilling
campaigns.
RESPEC does not know what type of certification RMGC had in 1992–1996, if any. However, RMGC was a well-known, independent commercial
assayer of that era, and RMGC was independent of Newmont. Newmont completed their check analyses at their in-house laboratory. Those checks were not independent of Newmont, exist only in paper form, and should be added to the project database.
8.2.3
Tombstone 1998
Tombstone passed their RC cuttings through a rotary wet splitter below the cyclone to produce samples weighing 10–15 lb. Tombstone washed the splitter
before each new sample was taken and placed a five-gallon bucket under the splitter to collect the wet samples. They then partially decanted the water from the bucket and emptied the RC cuttings and the remaining fluid into the sample bags and
rinsed out the bucket to wash any remaining fines into the sample bag. Tombstone closed the sample bags with one-way plastic ties and transported them to the Vale field office, where American Assay Laboratory (AAL) took possession and transported to
their laboratory in Sparks, Nevada.
AAL prepared and analyzed Tombstone’s RC and half-core samples. Laboratory personnel dried the samples at
100°C, crushed them to 8 to 10 mesh, and passed the crushed material through a Jones riffle splitter to produce a four-pound subsample, then pulverized these subsamples to 90% -150 mesh, blended them, and took a 350-g split. AAL analyzed for
gold by fire assaying a 30-g aliquot of the 350-g split with an AA finish (AAL method FA30), and analyzed for silver with method D210, which included aqua-regia digestion. AAL was independent of Tombstone and remains a well-known commercial
laboratory. RESPEC does not know what certification AAL held in 1998, if any.
8.2.4
Calico 2011-2012
Calico personnel transported their 2011 and 2012 drilling samples from the drill sites to the Calico sample handling and core logging facility in Vale. Before
moving the core, Calico staff recorded the date, box number, number of boxes transported, and beginning and ending footages of the transported core on a core handling form.
At the logging facility, Calico personnel measured and recorded core recovery and RQD data. A Calico geologist then logged the core, recording lithological,
alteration, mineralization, and structural information that included the angle of intersection of faults with the core, fault lineations, fractures, veins, and bedding. Calico then prepared the entire length of core for sampling. Calico geologists
based the sample intervals on the geological logs in order to separate different lithologies and styles of mineralization and alteration. Calico’s sample lengths generally did not exceed 5 ft and, where possible, correlated to the 5-ft
drilling runs. After completing logging, Calico geologists marked the sample intervals and assigned each one a unique sample identification (sample tag), with the sample tag stapled inside of the
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box at the end of each sample interval. They placed a duplicate sample tag for each interval inside the sample bag and recorded the sample number in the sample tag booklet. If they suspected or
observed contamination or down-hole caving, they flagged the interval and didn’t sample it. If any significant veins, veinlets, healed breccias, or other potentially mineralized planar features were present, Calico geologists marked a line
down the length of the core to indicate the line along which the core should be sawn or split to ensure the sampler took a representative sample.
Once
Calico geologists had completed the core logging and marked all the sample intervals, the core was sprayed with water and photographed. They then moved the core boxes to the sampling station, and a technician either split the core with a hydraulic
splitter or cut the core in half with a diamond-blade core saw. The technician placed one half of the split core into a cloth sample bag labeled with the sample number, returning the other half to the core box for future reference. The Calico
technician split intensely broken or very soft core in half using a small scoop or putty knife and placed one of the halves in the numbered sample bag. The sample number, the starting and ending footage of the sample interval, the date, and the
technician’s initials were recorded on a core cutting/splitting form. The technician then tied the sample bags shut and stored them in the secure core facility until a complete sample batch was ready for shipment.
Typically, Calico allowed the RC samples to drain at the drill site for two to three days before transporting them to their storage and core logging facility
in Vale, where they recorded the date and the number of samples transported on a sample handling form. A geologist or technician arranged the samples in a manner that accounted for all samples, blanks, and standards and photographed them prior to
shipment to the analytical lab. Calico then air-dried and stored the RC samples until a commercial freight service transported them to the ALS Minerals (ALS) laboratory in Reno, Nevada.
Calico filled out and maintained a complete sample inventory as an Excel spreadsheet to verify that all samples were accounted for and that bags were not
damaged prior to shipment. Calico personnel packed drill-core sample bags into rice bags and sealed each rice bag with a numbered security seal. They placed RC samples into super sacks and sealed each super sack with a numbered security seal. Each
shipment only included samples from a single drill hole. Calico prepared a sample submittal form with the shipment number, security seal numbers, the sample numbers, the type of analyses requested, and a list of samples to be duplicated. They
included a hard copy of the submittal form with the sample shipment and emailed an electronic copy to the laboratory. The personnel who prepared the shipment filled out a chain of custody form that included the sample shipment number, the location
the samples were shipped from, the total number of containers in the shipment, the security seal numbers, the name of the person who prepared the shipment, the name of the person who transported the shipment, and the name of the person who received
the shipment at the laboratory. The receiving individual at the laboratory completed the form and noted any damage or discrepancies and returned the form to Calico. The driver of each truck was also required to sign off on the chain of custody form.
A commercial freight service transported Calico’s 2011 and 2012 drilling samples to ALS. ALS was independent of Calico and maintained an ISO
9001:2008 accreditation for quality management and ISO/IEC17025:2005 accreditation for gold assay methods.
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ALS crushed the samples to 75% passing <6 mm and then split off a 250-g subsample for pulverization to 85%
passing <75 µm (200 mesh). Laboratory personnel processed clean sand through the crusher every five samples, when a technician noted any color change in the sample, and between every sample in the pulverizing step. ALS split pulps to
separate a 30-g aliquot for determining gold by fire assay with AA finish (ALS code Au-AA23) and used a separate 5-g aliquot for inductively coupled plasma atomic-emission spectrometric (ICP-AES) determination of silver and 32 major, minor, and
trace elements following a 4-acid digestion (ALS code ME-ICP61). If the original gold assay exceeded the 10 g/t Au (0.29 oz/ton Au) upper limit of the analyses, ALS took additional aliquots from the same pulp for fire assay with gravimetric
finish (ALS code Au-GRA21). Samples that yielded silver assays greater than 100 g/t Au (2.92 oz/ton Au) were reanalyzed using a 10-g aliquot with a four-acid digestion for silver and an AA finish (ALS code AG-OG62). Samples that assayed greater than
1,500 g/t Ag (44 oz/ton) were reanalyzed using a 30-g fire assay with a gravimetric finish (ALS code Ag-GRA21).
8.2.5
Paramount 2016-2019
Paramount personnel transported samples from Paramount’s drilling programs in 2016 through 2019 from the drill sites to Paramount’s storage and
logging facility in Vale. For sample handling, drying, logging, sample marking, core cutting, and packaging, Paramount applied the procedures Calico used for core and RC samples in 2011 and 2012 (Section 8.2.4), with the exception of the two
geotechnical core holes drilled in 2019 that remain unsampled as of the effective date. Paramount personnel cut competent core lengthwise into halves with a saw and split highly broken core by hand directly from the box using a brush and spoon in an
effort to take a representative half-core sample. (Approximately 10% of the core samples were split by hand.) After logging and sampling by Paramount geologists and technicians, ALS personnel transported core samples from the project office in Vale
to ALS sample preparation facilities in either Reno or Elko, Nevada. Paramount and ALS completed chain of custody paperwork and maintained sample security at all times. ALS is a commercial assayer independent from Paramount that maintains an ISO
9001:2008 accreditation for quality management and ISO/IEC17025:2005 accreditation for gold assay methods.
ALS crushed the samples to 75% passing a
6-millimeter mesh and then split off 250-g subsamples for pulverization to 85% passing -<75 µm (200 mesh). ALS technicians processed clean sand through the crusher every five samples, any time they noticed a color change in the sample, and
processed clean sand through the pulverizer between every sample in the pulverizing step. Laboratory personnel split the pulps to separate a 30-g aliquot for determining gold by fire assay with AA finish (ALS code Au-AA23), and used a separate 5-g
aliquot for ICP-AES determination of silver and 32 major, minor, and trace elements following a four-acid digestion (ALS code ME-ICP61). If the original gold assay exceeded the 10.0 g/t Au upper limit of detection, ALS split further aliquots from
the same pulp for fire assay with gravimetric finish (ALS code Au-GRA21). Samples that assayed greater than 100 g/t Ag were reanalyzed using a 10-g aliquot with a four-acid digestion for silver and an AA finish (ALS code AG-OG62) and samples that
assayed greater than 1,500 g/t Ag were reanalyzed using a 30-g fire assay with a gravimetric finish (ALS code Ag-GRA21).
8.3
Quality Assurance/Quality Control Procedures
8.3.1
Atlas QA/QC, 1987–1992
Atlas employed two primary QA/QC procedures:
•
Random re-sampling of coarse-reject material for samples where the initial assay was greater than approximately
0.020 oz/ton Au
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•
Analyses of RC rig duplicates of original 5-ft samples collected at even 100-ft intervals
Periodically, Atlas geologists prepared a list of the initial Chemex assays greater than approximately 0.020 oz/ton Au, and for every 10th sample on the list, collected the coarse rejects and split them into two one-pound subsamples. Atlas sent these coarse-reject subsamples to Cone Geochemical Laboratories (Cone) in Denver, Colorado,
and Hunter Mining Laboratories (Hunter) in Reno, Nevada. Cone and Hunter were independent of Atlas, but RESPEC does not know if these laboratories held certifications at that time. The check samples sent to both laboratories were prepared using the
same procedures. Laboratory personnel dried the samples, cone-crushed them to minus 1/8 inch, and split them into 125-g subsamples that were then ring pulverized to minus 150 mesh. From these pulps, the labs analyzed 30-g aliquots by fire assay.
Atlas sent the duplicate samples collected at 100-ft down-hole intervals and the original samples to the Chemex preparation facility in Boise, and then to the Chemex assay laboratory in North Vancouver for analysis. Hunter assay certificates
indicate that they performed fire-assays with a gravimetrical finish. The available certificate documentation does not indicate what finish the Cone assays used.
Atlas sent the rig duplicates to Chemex along with the original drill samples.
8.3.2
Newmont QA/QC, 1992–1996
Newmont sent 163 check samples to their in-house Newmont Metallurgical Services laboratory in Salt Lake City, Utah for fire assays with AA finishes. The nature
of these samples (e.g., pulps, preparation duplicates, or field duplicates) is not known. RMGC assayed the original samples.
Text from an original
Newmont report or memorandum that lacks the header page describes the testing of drill core from hole GMC-001-9, which was a wedge off hole GMC-001. Testing three splits entirely consumed the core—both halves of the sawn core and samples of
the fines derived from the sawing of the core.
Newmont asked RMGC to reanalyze 98 samples originally analyzed by RMGC. RESPEC does not know the nature of
these check samples. Some evidence suggests they were preparation duplicates.
8.3.3
Tombstone QA/QC, 1998
Tombstone sent the following samples to Chemex for check analyses: 14 AAL pulps for pulp-check analyses, 15 two-pound splits of AAL coarse rejects as
preparation duplicates, 14 core duplicates, and 15 RC rig duplicates. (The RC rig duplicates were originally collected at approximately even 100-ft intervals.)
Chemex checked the mesh sizes of the 14 AAL pulps prior to analyses. The RC and core duplicates were dried at 100°C and crushed to 65% less than 10 mesh.
Laboratory personnel split these coarse-crush samples, along with the preparation duplicates, into 200–300-g subsamples using a Jones riffle splitter, and then ring-pulverized these subsamples to 95% passing 150 mesh. Chemex fire assayed 30-g
aliquots for gold and silver using gravimetric finishes.
In addition to the QA/QC testing described above, Tombstone selected 60 AAL coarse rejects from
storage and instructed AAL to coarse pulverize the entire sample to minus 60 mesh. AAL split the samples into halves with a rotary splitter, sent one set of the halved samples to Chemex for pulverization to 95% passing 150 mesh and 30-g fire assay
analysis with an AA finish. The lab prepared and analyzed the second set of halved samples using the same methods.
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Tombstone referred to these samples as “Assay Prep Checks” and called the more standard preparation duplicates described in the previous paragraph “Reject Checks.”
AAL also routinely completed replicate analyses of AAL original pulps.
8.3.4
Calico QA/QC, 2011–2012
Calico inserted QA/QC samples every 10th sample in sequence using pre-labeled bags in the same manner as
the primary core and RC-chip samples, and grouped drill samples in batches of 36 samples. Each batch contained a field duplicate, a commercially prepared certified reference material (CRM), and a blank. The blanks included commercial blank pulps and
coarse basalt rock barren of gold (coarse blanks). Calico inserted all four types of control samples with core samples, but only inserted CRMs and blank pulps with the RC samples.
Calico used the basalt rock coarse blank to monitor contamination potentially introduced during the coarse crushing and pulverization of core samples. The
blank pulps monitored for contamination introduced after pulverization.
Three commercial CRMs obtained from CDN Resource Laboratories Ltd. (CDN) were
inserted to assess the precision and accuracy of the analyses. These are listed in Table 8-1.
Table 8-1: Grassy Mountain Certified Reference Materials for 2011–2012
CRMID
Certified Value
(g/t Au)
2 Std. Dev.
(g/t Au)
Submitted
No.
CDNGS-P3A
0.338
0.022
55
CD-GS-3J
2.71
0.26
36
CD-GS-8A
8.25
0.60
21
To assess the homogeneity of the sample material and the overall sample variance, Calico had the analytical lab create a
preparation-duplicate approximately every 20 samples. During the 2011 drilling program, Calico retrieved 59 sample pulps representing about 5% of the samples from the higher-grade portion of the deposit and shipped them to ALS as check samples.
8.3.5
Paramount QA/QC, 2016–2019
Paramount compiled an electronic database containing all historical and 2016–2019 drilling information. This database was maintained using SQL software
and housed in an off-site remote server that is controlled by a third-party database expert. All database inquiries and data requests were routed through this third-party expert. To prevent any unauthorized changes to the Paramount database, their
designated data manager and the third-party expert controlled all data. Paramount established QA/QC protocols for data management, verification, validation, and data screening, which consisted of primary and secondary checks on electronic entry of
field data, drill-hole data, sample information, assays, and geochemistry. To ensure accuracy, Paramount and the third-party database expert verified and cross-checked all information.
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During the 2016–2019 drilling programs, Paramount inserted nine different commercially prepared CRMs
obtained from CDN into the sample sequence for QA/QC purposes (Table 8-2).
Table 8-2: Grassy Mountain Certified Reference Materials Employed by Paramount, 2016–2019
CRMID
Certified Value
(g/t Au)
2 Std. Dev.
(g/t Au)
Certified Value
(g/t Ag)
2 Std. Dev.
(g/t Ag)
Submitted
No.
CDN-GS-P3A
0.338
0.022
31
30
CDN-GS-P3C
0.263
0.02
26
CDN-GS-P4F
0.498
0.028
22
CDN-GS-P7E
0.766
0.086
28
CDN-GS-1Q
1.24
0.08
40.7
2.2
32
CDN-GS-3J
2.71
0.26
57
CDN-GS-8A
8.25
0.60
27
CDN-GS-10D
9.50
0.56
12
CDN-ME-1414
0.284
0.026
18.2
1.2
36
Paramount’s QA/QC protocols required that standards assayed within the three-standard deviation threshold of the
certified target gold value furnished by CDN. One of the CRMs had certified silver target values. If any assays of the CRMs returned values outside the three standard-deviation limits, Paramount evaluated the assays previous to and immediately after
the failed sample for accuracy and for cohesiveness with the geology and mineralization. If Paramount suspected that any of the assay results were problematic, the laboratory reanalyzed the samples.
For both core and RC samples, Paramount inserted a white marble chip blank sample. If any blank samples assayed above a 0.10 g/t Au limit, they examined the
preceding sample and the sample after the failed sample for contamination or a possible source of contamination. The laboratory reassayed any surrounding, potentially problematic sample assays.
RC rig-duplicate samples were collected at the drill rig.
8.4
Quality Assurance/Quality Control Results
8.4.1
Atlas, 1987–1992
To help verify their drill-hole gold results, Atlas made extensive use of preparation duplicates and field duplicates. Chemex, the primary assay laboratory
used by Atlas, analyzed the field duplicates. Atlas sent the preparation duplicates to Cone and Hunter.
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8.4.1.1
Preparation Duplicates
Preparation duplicates are analyses of pulps derived from secondary splits of the coarsely ground material (coarse rejects) that remain after the primary split
is taken for the original assay. Preparation duplicates evaluate the variability introduced by subsampling of the coarsely crushed material. Ideally, preparation duplicates should be analyzed by the primary analytical laboratory to eliminate any
variability introduced by different techniques employed at a second laboratory. However, Atlas sent their preparation duplicates to two secondary laboratories.
RESPEC compiled the data for Atlas’s 458 preparation duplicates derived from coarse rejects of samples from 89 Atlas drill holes analyzed by Cone. The
relative-difference (RD) graph in Figure 8-1 shows the percentage difference (plotted on the y-axis) of each Cone preparation-duplicate assay relative to its paired primary-sample analysis by Chemex. This RD
is calculated as follows:
The x-axis of the graph plots the means of the gold values of the paired data (the mean of pairs or MOP) in a sequential
but non-linear fashion. The red line shows the moving average of the RDs of the pairs, thereby providing a visual guide to trends in the data that aids in the identification of potential bias. Positive RD values indicate that the duplicate-sample
analysis is greater than the primary-sample assay. A total of 17 pairs characterized by unrepresentatively high RDs are excluded from Figure 8-1.
Figure 8-1: Cone Analyses of Preparation Duplicates Relative to Original Chemex Gold Assays
Source: RESPEC, 2018
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The graph suggests a low bias in the Cone gold results relative to the original Chemex assays over
significant portions of the grade range of the data. The mean of Cone analyses (0.226 oz/ton Au) is lower than the mean of the original results (0.237 oz/ton Au), and the average RD of the pairs is -7%. (The average RD can be an approximate measure
of the degree of bias, although one must be aware of the statistical effects of pairs with anomalously high RDs.) The mean of the absolute value of the RDs (AVRD) is 29%, which is a measure of the average variability exhibited by the paired data.
Hunter analyzed 428 preparation duplicates from the same original sample set as analyzed by Cone (Figure 8-2).
Figure 8-2: Hunter Analyses of Preparation Duplicates Relative to Original Chemex Gold Assays
Source: RESPEC, 2018
In
this case, 25 extreme outlier pairs are removed for the purposes of this discussion. The mean of the Hunter analyses is lower than the mean of the original Chemex assays (0.208 vs. 0.221 oz/ton Au), and the average of the RDs is -9%. The AVRD is
34%.
The Hunter and Cone preparation-duplicate data are generally consistent, showing a low bias in the gold results relative to the original Chemex
analyses and average variability of approximately 30%. One difference in the duplicate versus original analyses is that the Chemex pulps were prepared to meet a 95% minus 100-mesh particle size, and the Hunter and Cone pulps were pulverized to minus
150 mesh.
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8.4.1.2
RC Field Duplicates
Field duplicates are secondary splits of drill samples that are mainly used to assess the natural grade variability of the deposit and to evaluate the total
subsampling variances attributable to splitting both in the field and in all subsequent subsampling steps in the laboratory. Atlas collected field duplicates at the RC drill sites at the same time as the original samples and sent the field
duplicates to Chemex together with the original samples. RESPEC compiled the results of 1,252 RC duplicates from 165 holes drilled by Atlas (Figure 8-3; thirty-eight pairs in which both the original and
field-duplicate analyses are less than the detection limit are removed, as are 14 extreme outlier pairs).
Figure
8-3: Chemex Analyses of RC Field Duplicates Relative to Original Chemex Gold Assays
Source: RESPEC, 2018
The
field duplicates compare well with the original results, and the means of the datasets are identical (0.016 oz/ton Au). The average of the RD is +4%, while the mean of the AVRD is 35%.
8.4.1.3
Miscellaneous QA/QC Samples
In addition to the preparation and field duplicates, in 1990, Atlas sent 32 samples of unknown type (e.g., sample pulps, coarse rejects, or field duplicates)
from drill hole 026-034 to Shasta Analytical Geochemistry Laboratory of Redding, California (Shasta) for 30-g fire assays. RESPEC does not know if Shasta had formal accreditation at the time of the Atlas assays. A handwritten note on the paper assay
certificate states that these samples consist of a “set of 4th check assays from [this] hole.” Figure 8-4 compares the Shasta check assays to
the original Chemex results. One outlier pair and two pairs in which Chemex overlimit assays were not performed are removed from the graph.
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Figure 8-4: Shasta Check Analyses Relative to Original Chemex Gold
Assays
Source: RESPEC, 2018
The
paired data compare reasonably well up to a MOP grade of ~0.2 oz/ton Au. At higher grades, the Shasta check assays tend to be lower grade than the Chemex original analyses, although there are too few pairs to make definitive conclusions. The mean of
the Shasta analyses (0.462 oz/ton Au) is significantly lower than the mean of the original Chemex assays (0.533 oz/ton Au), but this difference is largely due to the two highest-grade pairs.
In May 1988, Tombstone sent 12 high-grade Chemex pulps from eight Atlas drill holes to AAL for check assaying. One of the pulps did not have the 30 g needed
for the one-assay-ton (30 g) gravimetric fire assays. The mean of the 11 check assays (3.835 oz/ton Au) agrees well with the mean of the original Chemex results (3.866 oz/ton Au).
In late 1990, Phelps Dodge Mining Company had four pulps and 27 coarse-reject samples from nine Atlas holes sent to Chemex for assaying. Backup information is
not adequate to determine which of the check assays are from pulps versus the coarse rejects. The paired data compare well up to a MOP of approximately 0.14 oz/ton Au. The check assays in the seven pairs at higher grades are on average lower grade
than the original results, but again the quantity of data is insufficient to derive statistically valid conclusions.
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8.4.2
Newmont, 1992–1996
8.4.2.1
Preparation Duplicates
In 1993, Newmont had RMGC reanalyze 98 samples originally analyzed by RMGC. Five of the samples did not have sufficient material to assay. The nature of these
check samples is uncertain, but the assay certificate includes a column with the heading, “REMARKS”, that state, “To report Original Pulp and New Pulp values for Gold fire and Cyanide.” This suggests the samples were
preparation duplicates. Figure 8-5 compares the check results to the originals. Six outlier pairs are excluded.
Figure 8-5: RMGC Check Analyses Relative to Original RMGC Gold Assays
Source: RESPEC, 2018
The
duplicates and originals compare reasonably well, and the mean of the checks (0.903 oz/ton Au) is close to the original (0.923 oz/ton Au). The mean of the RD is +2%, while the mean of the AVRD is 15%.
8.4.2.2
Core Field Duplicates
Newmont wedged drill hole GMC-001-9 off drill hole GMC-001. Newmont submitted both halves of the sawed core from the wedge hole for analyses by RMGC.
Newmont’s split “A” is presumed to be the original sample in the following analysis and split “B” is considered a core-duplicate sample. In July 1993, Newmont sent the two sets of 73 core samples to RMGC for sample
preparation and fire assaying. Figure 8-6 is a RD plot of the data, excluding two pairs that did not have sufficient material to analyze and five outlier pairs.
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Figure 8-6: RMGC Core Duplicate “B” Relative to RMGC
“A” Gold Assays
Source: RESPEC, 2018
The
core-duplicate values are higher than the originals up to a MOP grade of approximately 0.020 oz/ton Au, then lower than the original at MOP grades of about 0.040 oz/ton Au and higher. The mean of the core duplicates is 0.085 and the mean of the
originals is 0.108 oz/ton Au, but if the highest-grade pair is removed, the duplicate mean becomes higher than the original (0.052 and 0.049 oz/ton Au, respectively). The mean of the RD is +2%, while the mean of the AVRD is 30%.
The preparation-duplicate data and core-duplicate data do not identify any significant issues. Taken together, the two datasets suggest the variability
attributable to the splitting of core into halves is approximately 15% (core-duplicate AVRD of 30% minus preparation-duplicate AVRD of 15%).
8.4.2.3
Miscellaneous QA/QC Samples
In December 1993, Newmont had RMGC reanalyze the “A” and “B” pulps. These pulp-check analyses for both datasets yielded results
extremely close to the original November 1993 assays, with means of RDs of 0% and 1% for the A and B pulp sets, respectively, and AVRDs of 2% in both cases.
As a check on the RMGC results, Newmont completed gold fire assays on 163 samples at their in-house metallurgical assay facility in Salt Lake City, Utah
(Jory, 1993). RESPEC does not know the nature of the check samples (pulps, coarse rejects, or field duplicates). The mean (0.970 oz/ton Au) and median (0.080 oz/ton Au) of the Newmont checks reported by Jory (1993) are both slightly higher than
the original RMGC mean (0.942 oz/ton Au) and median (0.078 oz/ton Au).
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In addition to Newmont’s sampling and analytical verification programs discussed above, in April 1998,
Tombstone sent nine high-grade samples of Newmont “drill cuttings” from seven drill holes to AAL for preparation and 30-g gravimetric fire assays. The AAL analyses had a mean of 11.209 oz/ton Au, which compared well to the mean of
11.25 oz/ton Au from RMGC’s original assays.
8.4.3
Tombstone 1998
8.4.3.1
Replicate Analyses
AAL, Tombstone’s primary assay laboratory, routinely completed replicate analyses of some of the original assays. Replicate analyses use a second aliquot
taken from the primary sample pulp and are typically reported on the same certificate as the original assays. For the 10 holes drilled by Tombstone, AAL reported a total of 113 of these analyses on the same certificates that reported the original
assays. The replicate analyses show excellent reproducibility of the original assays, with a mean that is almost identical to the original and an average RD of +1%. The mean of the AVRD is 6%, which is somewhat high for replicate analyses.
8.4.3.2
Preparation Duplicates
Tombstone had AAL crush a total of 60 AAL coarse rejects from two drill holes to minus 60 mesh and split into halves. AAL pulverized and analyzed one set of
the halves. Tombstone had Chemex do the same to the second set. The results of this modified version of preparation duplicates completed by AAL are shown in Figure 8-7.
Figure 8-7: AAL Preparation Duplicate Analyses Relative to AAL Original Gold Assays
Source: RESPEC, 2018
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The RD graph shows high biases at low and high grades, while a low bias is evident at MOP grades between
approximately 0.025 and 0.06 oz/ton Au. The duplicate mean is higher than that of the original samples (0.175 vs. 0.157 oz/ton Au), and the mean of the RDs is +11%.
A RD graph of the Chemex analyses versus the original AAL results shows a roughly similar form as seen in Figure 8-7,
although no bias is present. In this case the duplicate mean (0.159 oz/ton Au) matches the original mean well, and the mean of the RDs is +1%. The means of the AVRD is 20%.
The differences between the AAL and Chemex results are likely more a reflection of insufficient data to adequately evaluate the Tombstone preparation
duplicates than some internal differences between the two laboratories.
8.4.3.3
Miscellaneous QA/QC Samples
Tombstone sent Chemex a set of original AAL pulps for pulp-check analyses, splits of AAL coarse rejects as preparation duplicates, and some core and RC field
duplicates. The mean of 14 pulp-check analyses from three drill holes (0.523 oz/ton Au) is about 5% higher than that of the original AAL analyses (0.499 oz/ton Au). The mean of 15 Chemex preparation duplicates from six drill holes is also
higher than the AAL mean (0.447 vs. 0.412 oz/ton Au, respectively). A total of 13 core duplicates from four drill holes yielded a mean (0.119 oz/ton Au) much higher than the original analyses (mean of 0.085 oz/ton Au), but the elimination of one
extreme pair (0.414 oz/ton Au for the duplicate vs. 0.080 oz/ton Au for the original) brings the duplicate mean (0.094 oz/ton Au) much closer to the mean of the original samples (0.086 oz/ton Au). The mean of 15 RC duplicates from six drill
holes is again higher than the mean of the original samples (0.055 vs. 0.048 oz/ton Au, respectively).
While none of the miscellaneous testwork involves
sufficient samples to derive statistically significant conclusions, the check analyses of the various sample sets are consistently higher than the original AAL results.
8.4.4
Calico, 2011–2012
8.4.4.1
Certified Reference Materials
Calico used three sets of CRMs to evaluate the analytical accuracy and precision of ALS’s original analyses of the Calico drill samples. Calico inserted
the CRMs into the original sample stream and analyzed them with the drill samples. In the case of normally distributed data, 95% of the CRM analyses are expected to lie within the two standard-deviation limits of the certified value, while only 0.3%
of the analyses are expected to lie outside of the three standard-deviation limits. However, most assay datasets from metal deposits are positively skewed.
Figure 8-8 shows a plot of the ALS analyses of CRM CDN-GS-3J, which has a certified value of 2.71 g/t Au (0.079
oz/ton Au). The x-axis plots the certificate numbers by increasing dates.
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Figure 8-8: Chart of ALS Analyses of CRM CDN-GS-3J
Source: RESPEC, 2018
Samples exceeding the three standard-deviation limits are typically considered failures. As it is statistically unlikely that two consecutive analyses of
standards would lie between the two and three standard-deviation limits, such samples are also considered failures unless further investigations suggest otherwise. All potential failures should trigger investigation, possible laboratory
notification, and possible reassay of all samples included with the failed standard result.
Using the above criteria, two of ALS’s analyses of this
CRM are three standard-deviation failures. However, the CRM analyses are biased slightly low from the certified value. If this is taken into account, the low-side failure would not be a failure.
A similar analysis of the CRM CDN-GS-8, which has a certified value of 8.25 g/t Au (0.241 oz/ton Au) shows no bias and no failures, while CDN-GS-P3A has 12
failures out of the 56 ALS analyses. Although nine of the CDN-GS-P3A failures are on the high side (ALS value > certified value), no bias is evident in the data taken as a whole. CDN-GS-8A has a certified value of 0.338 g/t Au (0.010 oz/ton Au).
RESPEC does not know what actions, if any, Calico took in response to the CRM failures.
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8.4.4.2
Coarse Blanks
Calico also inserted coarse blanks into their sample stream. Coarse blanks are samples of barren material that are used to detect possible contamination in the
laboratory, which is most commonly introduced during sample preparation stages. For analyses of blanks to be meaningful, the blanks must be sufficiently coarse to require the same crushing and pulverizing stages as the drill samples. A significant
number of the blanks also need to be placed in the sample stream within—or immediately following—a set of mineralized samples, which would be the source of most contamination issues. In practice, this is much easier to accomplish with
core samples than RC. Blank results that are greater than five times the lower detection limit of the relevant analyses are typically considered failures that require further investigation and possible re-assaying of associated drill samples. The
detection limit of the ALS analyses was 0.005 g/t Au, so blank samples assaying over 0.025 g/t Au (0.0007 oz/ton Au) are considered failures.
ALS
analyzed a total of 18 Calico coarse blanks in 2011–2012 (Figure 8-9).
Figure 8-9: Chart of ALS Analyses of Coarse Blanks – Calico
Source: RESPEC, 2018
Three
of the coarse blank analyses exceeded the failure threshold, and the highest analysis of a blank was 0.100 g/t Au (0.003 oz/ton Au). All three of the failures are associated with previous samples that are significantly mineralized. Although the
blank data provide evidence of cross contamination during ALS sample preparation, the magnitude of this contamination is insignificant.
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8.4.4.3
Analytical Blanks
Analytical blanks are used to monitor possible contamination or calibration problems during the determination of gold concentrations. Calico used a blank
commercial pulp supplied by CDN Laboratories (CDN-BL-7) in their QA/QC program. ALS analyzed the analytical blank 62 times. Five of those analyses exceeded the 0.025 g/t Au (0.0007 oz/ton Au) threshold. The failures were 0.001, 0.001, 0.003, 0.004,
and 0.009 oz/ton Au. Analytical blanks do not commonly generate failures, and the latter three failures are levels that would warrant investigation and potentially corrective action. RESPEC does not know if Calico took any action in response.
8.4.4.4
Field Duplicates
Calico collected 40 RC duplicates and 10 core duplicates that were analyzed by ALS, the primary laboratory. The mean of the RC duplicates (0.030 oz/ton Au) is
close to the mean of the original assays (0.032 oz/ton Au). Although the average of the RDs is -9%, the removal of two of the higher-grade pairs with anomalously high RDs changes this average to 4%. The mean of the AVRD of the entire dataset is 21%.
The means of the duplicates and original samples are reasonably close (0.043 and 0.040 oz/ton Au, respectively) considering the lack of pairs. However,
the core-duplicate dataset is too small to derive meaningful conclusions.
8.4.4.5
Pulp-Checks
Pulp checks are reanalyzes of the remaining pulps from the original assays. These reanalyzes are typically completed by a second laboratory. Calico sent 59 of
ALS original sample pulps to AAL for check assays. Excluding one extreme outlier pair, the mean of the AAL checks compared well with the mean of the original samples (0.206 versus 0.208 oz/ton Au, respectively), and the average of the RDs is
-2%. However, the mean of the AVRD is 12%, which is relatively high for pulp-check analyses.
8.4.5
Paramount 2016–2017
8.4.5.1
Certified Reference Materials
Paramount inserted the nine certified CRMs listed in Table 8-2 into the RC and core sample stream.
Of the 270 ALS gold assays of the CRMs, nine analyses exceeded the three standard-deviation limits. Four of these are due to slight high biases in the ALS
analyses of GS-P3A and GS-P3C. Of the remaining five cases, three are from analyses of GS-P4F and each high result is only slightly above the high-side failure limits.
8.4.5.2
Pulp Checks
Paramount sent 569 ALS pulps from the 2016–2017 drilling program to AAL for pulp-check analyses (Figure 8-10;
eleven outlier pairs are excluded).
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Figure 8-10: AAL Pulp Checks of ALS Original Gold Analyses
Source: RESPEC, 2018
While
the means of the duplicate and original analyses are identical (0.066 oz/ton Au), the graph provides evidence of a slight high bias in the AAL check assays. The mean of the RDs is +3%. The mean of the AVRD is 8%.
The silver results also show a high bias in the AAL results compared to the original ALS assays. The mean of the AAL silver analyses is 4% higher than the ALS
mean, the average of the RDs is +6%, and the mean of the AVRD is 10%.
8.4.5.3
Coarse Blanks
ALS analyzed a total of 151 of Paramount’s coarse blanks (Figure 8-11), eight of which exceeded the failure
threshold.
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Figure 8-11: Chart of ALS Analyses of Coarse Blanks –
Paramount
Source: RESPEC, 2018
The
failures range from 0.029 to 0.221 g/t Au (0.001 to 0.007 oz/ton Au). Three of the blank analyses exceeded 0.1 g/t Au (0.003 oz Au/t). The failures do not correlate well with mineralization in previous samples, but the data suggests some cross
contamination during ALS sample preparation. The magnitude of this potential contamination in the three highest-grade blank analyses warrants investigation and, if appropriate, the re-assaying of the samples that accompany the failures.
8.4.5.4
Preparation Duplicates
ALS prepared and analyzed a total of 153 of Paramount’s preparation duplicates that were analyzed along with the original samples in 29 of the 30 holes
drilled by Paramount (Figure 8-12; three outlier pairs were removed).
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Figure 8-12: ALS Gold Analyses Preparation Duplicates –
Paramount
Source: RESPEC, 2018
The
mean of the gold analyses of the preparation duplicates is very close to the mean of the original assays (0.040 versus 0.039 oz/ton Au), and the average of the RDs is -1%. The mean of the AVRD is 9%. The silver results are very similar to those of
gold, with means of the duplicate and original samples of 0.172 and 0.174 oz/ton Ag, respectively. The mean of the RDs is -1% and the average of the AVRD of 9%.
8.4.5.5
Core Field Duplicates
Paramount regularly included RC and core field duplicates with their original samples submitted to ALS. The core duplicates consisted of half splits of the 1⁄2-core remaining, creating 1⁄4-core samples, from all 27 holes drilled at least in
part with core. Fines, consisting of pieces of core too small for sawing, were sampled using a scoop and putty knife to obtain an “eyeball”1⁄2-split, a
procedure identical to the procedure used for the primary 1⁄2-core samples. ALS analyzed a total of 136 core duplicates and 52 RC duplicates on behalf of Paramount.
The two datasets require separate evaluation because the splitting methodologies were completely different.
The
1⁄4-core duplicates are compared to the original results in Figure 8-13. Five outlier pairs were removed.
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Figure 8-13: Core Duplicates Relative to Original Gold Assays
– Paramount
Source: RESPEC, 2018
At
mean of pairs (MOP) of up to ~0.02 oz/ton Au, the means of the duplicate and original analyses are identical, although a slight low bias in the duplicate results is evident over much of this grade range. This bias is largely driven by spikes on the
graph that are predominantly pairs where the duplicates are lower than the originals. At MOP higher than 0.02 oz/ton Au, variability increases dramatically (AVRD = 40% versus 18% over the lower-grade range) and the duplicate data display both high-
and low-bias trends. On average, the duplicate data are lower grade than the original samples—means of duplicates and originals are 0.078 and 0.093 oz/ton Au, respectively, and the mean of the RDs is -16%.
Excluding seven outlier pairs, the silver results for the core duplicates compare well with the original results, with near identical means and an average RD
of -1%. The mean of the silver AVRD is 17%.
The core-duplicate gold results led to the submission of 59 additional core duplicates from 10 of the
Paramount drill holes that include core. In this case, 1⁄2-core samples were submitted, and, with the first set of core duplicates and Newmont results regarding
fines in mind (see Section 7.4.1), special care was taken to brush out all fines in the core boxes related to each sample interval and include them in the duplicate samples. The gold analyses of this second batch of core duplicates, excluding
two outlier pairs, show excellent correspondence with the original 1⁄2-core results up to a MOP grade of ~0.02 oz/ton Au (Figure
8-14).
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Figure 8-14: Second Set of Paramount Core Duplicates Relative to
Original Gold Assays
Source: RESPEC, 2018
At
higher grades, the core duplicates are systematically higher grade (duplicate mean is 8% higher than the original mean, and average of the RDs is +18%), and as was the case for the first set of core duplicates, variability increases substantially
(mean of the AVRD is 33%).
The silver values of the second set of duplicate core samples compare reasonably well with originals. The mean of the
duplicates (0.167 oz/ton Ag) is close to the original mean (0.163 oz/ton Ag) considering the relatively small dataset, and the mean of the RDs is +3%. The average of the AVRD is 18%.
It is reasonable to postulate from the core-duplicate data that sampling of the core-box fines derived from higher-grade gold samples may have played a
significant role in the core-duplicate gold and silver results. Specifically, native gold particles collecting at the bottoms of the boxes in high-grade samples may have been unrepresentatively lost to both the original half-core samples and the
first set of 1⁄4-core duplicates. This loss of native gold particles can be attributed to the manual, unsystematic splitting of the core-box fines (fines were
sampled with a scoop and putty knife). In contrast, the second set of half-core duplicates likely oversampled gold in the higher-grade samples, as these samples would have incorporated the gold lost from the primary samples (all fines left in the
core boxes were brushed into the duplicate sample bags). The possibility of free gold preferentially collecting in fines is supported by the results of Newmont analyses of saw fines (Section 7.4.1). In contrast to gold, silver analyses of both sets
of core duplicates compare reasonably well with the original assays.
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8.4.5.6
RC Field Duplicates
A total of 52 RC duplicate samples were collected for assay for 27 of the Paramount drill holes. Most of these drill holes were completed with core. Figure 8-15 compares the duplicate RC assays to the original results.
Figure 8-15:
Paramount RC Duplicates Relative to Original Gold Analyses
Source: RESPEC, 2018
The
means of the RC duplicates and originals compare well (0.018 versus 0.019 oz/ton Au, respectively), and the mean of the RDs is -1%. There is a suggestion of a low bias in the graph, although this is not well supported due to the low number of pairs.
The average of the AVRD is 23%, which is somewhat lower than expected, but could be due to the lack of higher-grade pairs.
The silver analyses of the RC
duplicates are systematically lower than the originals. The mean of the duplicates is 0.092 oz/ton Ag while that of the originals is 0.099 oz/ton Ag, and the average of the RDs is -13%. The cause of this systematic low bias in the silver results is
difficult to explain, but perhaps the bias would lessen with more data. The mean of the AVRD is 23%. Considering the presence of native gold, one would expect the gold variability to be higher than that of silver, which supports the conclusion above
of the surprisingly low variability in the RC duplicate gold results.
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8.4.6
Paramount 2018–2019
RESPEC did not review in detail the QA/QC results associated with the two 2018 RC holes drilled at the North Spur target, which lies outside of the limits of
the current mineral resources. Nor did RESPEC evaluate the QA/QC results associated with the two 2019 geotechnical core—the results of the geotechnical holes were not available to RESPEC until the 2022 resource estimation had been completed.
The data for these four holes have not been compiled and evaluated for this report update.
8.4.7
Discussion of QA/QC Results
The available Atlas QA/QC data of consequence (the preparation and field duplicates) suggest that the original gold assay results may be overstated to some
extent. However, the average grade of the duplicate dataset is much higher than the average grade of the Grassy Mountain deposit and repeat analyses of only the higher-grade portion of a deposit with free gold can yield results that on average are
lower than original assays. Without additional data, it is impossible to know whether there is a positive bias in the Atlas results, although a comparison of resources with and without Paramount drill data suggests there are no material issues with
the Atlas data (see Section 8.2.1).
The Newmont QA/QC data do not identify any issues, while it is possible that the Tombstone gold values are
slightly understated.
Paramount’s CRM, blank, and preparation-duplicate data revealed no issues. The core-duplicate data suggest that the Paramount
gold assays of core, particularly at higher grades, may be understated. These data also serve to emphasize the importance of careful sampling and splitting of core-box fines.
The variability evidenced by the duplicate data from all operators at Grassy Mountain does not exceed normal bounds, especially considering the presence of
visible gold.
8.5
Summary Statement
RESPEC is satisfied that the procedures and methods used for the sample preparation, analyses, and security of the historical and Paramount samples are
adequate for generating reliable data that is acceptable as used in this report.
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9
DATA VERIFICATION
9.1
Drill-Hole Data
The current Grassy Mountain drill-hole database, which forms the basis for the resource estimates in Section 11, consists of information derived from 472
drill holes. A total of 286 of these holes were drilled in the general area of the Grassy Mountain resource estimates. They include 34 Paramount holes and 252 historical holes.
Prior to the 2016–2017 drilling program, Paramount provided RESPEC with the project drill-hole database. RESPEC then subjected this database to the data
verification procedures discussed below and corrections were made as appropriate. After the creation of this verified database, RESPEC updated this database with the information acquired during Paramount’s subsequent drilling programs.
9.1.1
Collar Data
Atlas established a local grid coordinate system following the discovery of the Grassy Mountain deposit in 1988. This local coordinate system remained in use
until Calico acquired the project in 2011. Calico transformed all relevant project location data, including the drill-hole coordinates, into UTM coordinates. Calico made the transformation by plotting all drill holes on digital topography of the
project area in the local coordinate system, projecting these data onto a USGS topographic base map in UTM zone 11 NAD27 coordinates, and rotating and scaling the local-grid data until the contours generated from the Atlas grid matched those from
the USGS topographic map contours as closely as possible. Calico then determined the UTM coordinates of each drill hole. All subsequent drilling programs surveyed holes in these UTM coordinates.
As part of the 2016–2017 drilling program, Paramount re-surveyed all historical drill-hole collars that could be identified in the field—82 Atlas
drill holes, six Newmont drill holes, four Tombstone drill holes, and nine Calico drill holes. The survey contractor provided RESPEC with the original digital file, who used this file to compare the new survey locations with those in the existing
database. Excluding one drill hole for which the location was known to be incorrect in the original project database, the northings from the new survey differed from the database locations by more than 3 ft in four drill holes, with a maximum change
of 7 ft. The eastings differed by more than 3 ft in four drill holes, with a maximum change of 8 ft, and elevations of four drill holes differed by more than 3 ft, with a maximum change of 5 ft. These discrepancies were found in eight of the 101
re-surveyed historical drill holes. Due to the nature of the Grassy Mountain mineralization and the 5 x 10 x 10-ft block size used in modelling, RESPEC does not consider the scale of the discrepancies in the drill-hole locations material to the
estimate of mineral resources presented in this report.
The contractor also surveyed the locations of all hole collars in Paramount’s
2016–2017 drill programs. RESPEC used the original digital survey data for the historical and Paramount drill holes to update the drill-hole locations in the project database.
In addition to the drill-hole locations, RESPEC checked the total depths of 47 of the historical drill holes against historical records. The depth of one
drill hole was found to be off by one foot.
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9.1.2
Down-Hole Survey Data
Down-hole survey data exists for 43 historical holes drilled in the Grassy Mountain resource area. RESPEC chose to verify 14 of them. Excluding the three
Newmont drill holes discussed below, a total of 168 survey intervals from six Atlas drill holes, two Tombstone drill holes, and three Calico drill holes were checked against historical records. RESPEC found two azimuth measurements in the database
that were off by <1°, and three inclination errors of <1.5°. One of the azimuth errors and two of the dip discrepancies occurred in a single drill hole (Atlas hole 079-001). RESPEC corrected the project database to match the historical
records. RESPEC also added two survey intervals to the project database as a result of the audit.
RESPEC checked the down-hole survey data for three
Newmont drill holes. Supporting documentation consisted of Newmont handwritten “Drill Hole Summary” sheets. The project database includes more than twice the number of survey intervals than are listed on the summary sheets, and the
database azimuths and inclinations have higher precision than those on the summary sheets. The database values are very close to those in the summary sheets, although the values only match exactly when the precision of the two datasets is identical.
The summary sheets appear to be exactly as named—they summarize the down-hole survey data.
There are 209 historical drill holes within in the
Grassy Mountain resource area that lack down-hole survey data in the project database. RESPEC checked the drill-collar azimuths and dips for 40 of these holes against historical records and found no discrepancies.
RESPEC used digital data derived directly from the down-hole survey instrument to add the deviation data from Paramount’s drilling programs to the
project database. Paramount completed down-hole surveys on 28 of their holes. Down-hole caving precluded surveys for five drill holes, and Paramount collected no deviation data from a short (100-ft depth) geotechnical hole.
9.1.3
Assay Data
The original database provided to RESPEC included a total of 39,124 assay sample intervals from historical holes drilled in the Grassy Mountain resource area.
Of these sample intervals, RESPEC checked the database assay values for 6,942 of the intervals from 38 Atlas drill holes, two Calico drill holes, seven Newmont drill holes, and four holes drilled by Tombstone against historical documentation. The
audit revealed a total of only five errors in the database gold values, including:
•
two intervals with assay values from the assay certificates (0.002 and 0.004 oz/ton Au) that had no values in the
database;
•
two transcription errors whereby certificate values of 0.001 and 0.002 oz/ton Au were entered into the database
as 0.010 and 0.020 oz/ton Au; and
•
a value of zero in the database which should have been 0.054 oz/ton Au according to the assay certificate (the
zero value was likely mistakenly transcribed from an adjacent column on the assay certificate).
RESPEC found one silver error whereby a
0.28 oz/ton Ag value on the certificate was entered in the database as 0.2 oz/ton Ag.
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In addition to the errors described above, there were 28 sample intervals with database gold and silver assay
values of “0” that had no corresponding assays on the certificates—these intervals presumably had no sample recovery.
RESPEC corrected
all identified errors and added silver values found for one Atlas drill hole and three Tombstone drill holes that were not in the database.
For
Paramount’s 2016–2017 drilling program, RESPEC updated the resource database with digital assay certificates received directly from ALS.
9.1.4
Additional Data Verification
In addition to the verification procedures discussed above, RESPEC conducted extensive verification of the project data throughout the process of resource
modeling. As described in Section 11.7.1, RESPEC’s detailed, explicit modeling of the gold and silver mineral domains within the context of the project geology resulted in iterative modifications to the critical mineral-controlling
structural model that had been initially interpreted by Paramount. Paramount recognized the importance of lithologic mineralizing controls, which RESPEC confirmed. RESPEC verified Paramount’s lithologic model and used it to guide modeling of
the Grassy Mountain deposit’s mineral-domains.
The Paramount drilling also helped verify the historical data. As mineral-domain modeling proceeded,
RESPEC continually evaluated the grade and geological consistency between the historical data and the assays of Paramount’s drill holes. This work led to the recognition of potentially contaminated RC sample intervals, which were then excluded
from use in the mineral resource estimation.
As a further verification of the historical drilling data, RESPEC completed a test resource estimate that
excluded all Paramount drill data. RESPEC then compared the results to the current resource model which included the Paramount data. RESPEC ran the check estimation using the same estimation parameters as those used to estimate the current
resources. On a global basis (no cut-off), exclusion of the Paramount drill data resulted in 0.4% fewer gold ounces compared to the current resource estimation. At various cut-offs from 0.005 to 0.090 oz/ton Au, the highest-magnitude change was a
0.9% decrease in gold ounces. The constancy in the ounces estimated using composited assays that included or excluded Paramount data supports the use of historical drilling data in resource estimation.
9.2
Site and Field Office Inspections
9.2.1
Ausenco
Ausenco’s QP visited the Grassy Mountain project on 15 August 2019 and inspected the area planned for the portal and the general site layout.
9.2.2
RESPEC
RESPEC QPs have visited the project site and/or Paramount’s field office and core logging facility in Vale, Oregon numerous times as the project
advanced. The most recent was for one day on January 30, 2026. Paramount provided RESPEC with an overview of the geology and other project information at their core processing facility in Vale. RESPEC
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observed historical and Paramount paper files, QA/QC samples, core, RC samples, coarse rejects and pulps stored within the building. Although no drilling was being conducted at that time,
Paramount provided an overview of the core and RC logging, sample handling, storage and QA/QC procedures. RESPEC then reviewed the geology and observed planned locations for mine facilities at the Grassy Mountain site.
Prior visits by RESPEC QPs included one day in each of August and November 2016, three days in December 2016, a total of 30 days in January, February, and
March 2017, and one day in June 2018. During the past visits, RESPEC reviewed altered and sometimes mineralized outcrops in the Grassy Mountain deposit area at many of the exploration target areas discussed in various sections of this report. The
QPs also inspected active core and RC drill sites with ongoing sampling and logging. In addition, RESPEC reviewed drill core from several holes in detail, reviewed all project procedures related to logging, sampling, and data capture and made
recommendations where appropriate.
RESPEC assisted Paramount’s geological team with the cross-sectional geological modeling that served as the
basis for the resource modeling. These activities involved detailed checking, validation, and in some cases modifications of the Paramount and historical geological data, interpretations, and geological modeling of the Grassy Mountain deposit.
The site and field-office visits materially contributed to RESPEC’s understanding of the project and confidence in the project data.
9.2.3
SLR
SLR’s QP visited the project site on November 16, 2021 and met with senior technical staff from Paramount. The site visit included an on-site tour
with Paramount senior staff, local, State, and Federal permitting agencies to discuss the proposed TSF and TWRSF site.
9.3
Summary Statement
9.3.1
Ausenco
In Ausenco’s opinion, the data used for the development of the sections for which Ausenco is responsible are sufficient to support a feasibility study:
metallurgical testing and data was completed at certified laboratories and capital and operating costs were developed following AACE guidelines and included development of detailed mechanical and electrical equipment lists, electrical load lists,
reagent and consumable consumption calculations, vendor and supplier quotes, and material take-off and benchmarking from the Ausenco database.
9.3.2
RESPEC
RESPEC experienced no limitations in their data verification activities for the Grassy Mountain project. In consideration of the information summarized in
Sections 5 through 9 and 11 and 12 of the report, RESPEC consider the Grassy Mountain project data acceptable for use in this report, most importantly to support the estimation and classification of mineral resources and mineral reserves.
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9.3.3
SLR
SLR developed the closure plan and RCE. SLR is responsible for the data verification related to closure. Source data for the development of the closure plan
and RCE were provided to SLR by others as it pertains to individual facilities design responsibilities in the feasibility study. SLR has confidence in the validity of the data and the providers of the data considering these data were provided from
the PFS, design reports, etc. and utilized for the development and permitting of this project.
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10
MINERAL PROCESSING AND METALLURGICAL TESTING
10.1
Introduction
The Grassy Mountain deposit has been the subject of several historical metallurgical testwork programs between 1991 and 2020. The most recent test programs,
completed in 2018 and 2020 in support of this Feasibility Study Update, were carried out at SGS Canada Inc. (“SGS”) in Burnaby, BC and McClelland Laboratories Inc (“McClelland”) in Sparks, NV. A full breakdown of the results
for each metallurgical test program can be found in Table 10-1.
Table
10-1: Metallurgical Testwork Summary
Year
Laboratory/Location
Laboratory Certification
Relationship
to the
Registrant
Testwork Performed
1990, 1991
Hazen Research Inc.
https://www.hazenresearch.com/about/quality-safety
Independent
Comminution tests, gravity concentration tests, flotation tests, leach tests, column leach tests, cyanide detox tests, solids liquids separation tests
1991
Golden Sunlight Mines Inc.
N/A
Independent
Comminution tests, leach tests
1993
Newmont Exploration Inc.
None listed on website
Independent
Column leach tests
2015
RDI Inc.
N/A
Independent
Mineralogy, comminution tests, gravity concentration tests, flotation tests, leach tests, column leach tests, cyanide detox tests
2018, 2020
SGS Canada Inc.
Conforms to the requirements of the ISO/IEC 17025 standard for specific registered tests.
Independent
Mineralogy, comminution tests, gravity concentration tests, leach tests, oxygen uptake tests, solids liquids separation tests, cyanide detox tests
2020
McClelland Laboratories Inc.
ISO/IEC Standard 17025:2017
Independent
Leach tests
During the 2018 PFS, the testwork program was focused on a gravity, leach and adsorption flowsheet comprising:
•
Primary grind (80% passing or P80 of 100 mesh or 150
µm)
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•
Gravity gold recovery
•
Cyanide leaching
•
Adsorption in a carbon-in-leach (CIL) circuit
•
Cyanide destruction.
During the 2020 FS, the leach flowsheet design was modified to a simpler, lower capital cost alternative comprising:
•
Primary grind (P80 of 150 mesh or 106 µm)
•
Hybrid leach–CIL circuit
•
Mercury removal circuit
•
Cyanide destruction.
10.2
Historical Testwork Programs
10.2.1
Historical Studies 1989 to 2012
In support of the FS, historical work conducted by Hazen, Golden Sunlight, Newmont, and Resource Development Inc. (RDI) was reviewed. The degree to which
historical metallurgical samples are representative of the Grassy Mountain deposit is not known with certainty, but there is no evidence that the historical samples were not representative. Early historical work listed above is viewed as indicative
or informative only since the QP was not able to reconcile the test results to drill hole locations and depth to confirm that these drill holes represent the ore in the current mine plan.
Historical results are presented in Section 10.4, where relevant to the current flowsheet.
10.2.2
Historical Testwork from 2018 PFS
In 2017, Ausenco oversaw metallurgical testing to develop data for the 2018 PFS for the Grassy Mountain Project.
10.2.2.1
2018 PFS Sample Selection
Nine samples were submitted for metallurgical testing. Lithologies were identified by Ausenco, under the guidance of the Paramount technical team. Samples were
described as Arkose, Mixed Lithology Drop Weight Test (MLDWT), Mixed Lithology Low Grade (ML-LG), Mixed Lithology Average Grade (ML-1), Mixed Lithology Average Grade (ML-2), Mixed Lithology High Grade (HG), Silt Stone (SLST), Mudstone and Clay Mixed
Breccia (CMB).
10.2.2.2
2018 PFS Testwork Scope
PFS testwork was completed but SGS Canada Inc. (SGS) in Burnaby, Canada conducted the metallurgical testing and associated assays shown in Table 10-2 under program 15944-001. SGS conforms to the requirements of ISO/IEC 17025 for specific tests as listed on their scope of accreditation which can be found at www.scc.ca/en/search/palcan/sga.
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10.3
2020 FS Testwork
10.3.1
Objectives
Metallurgical testwork in support of the FS was defined based on review of historical work and consideration of the mine plan prepared during the 2018 PFS.
Consideration was also given to potential for optimization, and flowsheet simplification.
The program was designed with the intent to confirm the
parameters for the process design criteria for comminution, leaching, carbon adsorption and cyanide destruction in the process plant and to assess recovery as a function of head grade. The metallurgical program was conducted at SGS.
Supplementary work to support recovery estimation was conducted at McClelland Laboratories, Inc (Sparks, Nevada); (McClelland).
10.3.2
SGS Testwork Program 15944-002 Scope of Work
Six samples were sent to SGS for metallurgical testing.
The
range of tests and samples used for each test is summarized in Table 10-3.
10.3.3
McClelland Testwork Program MLI 4551 Scope of Work
Twelve samples were sent to McClelland for metallurgical testing.
The testwork program scope included determination of head assays and leach tests.
10.3.4
Sample Selection for SGS Program 15944-02
The composite samples were selected by Paramount with input from Ausenco to represent the production composites for the proposed Year 1 and Year 2 of
operations, and the major lithologies, Arkose, Siltstone and Sinter (Table 10-3).
The metallurgical program was
performed on the following composites: Year 1, Year 2, Arkose, Siltstone, Sinter and un-used ML-LG sample from the 2017/2018 testwork program.
Since
there was insufficient sample available of the Year 1 composite for comminution testing, it was decided to test the comminution properties for each of the major lithologies for Year 1 as an alternative. A low-grade sinter sample was provided for
comminution testing.
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10.3.5
Sample Selection for McClelland Program MLI 4551
Samples tested at McClelland were made up from drill core as composites to represent the ore that will be mined during the first two years of production.
Twelve grade variability composite samples (4551-001 to 012) and one master composite sample (4551-013) were tested. Variability composite samples calculated gold and silver grades ranged from 3.57–13.13 g/t Au and 5.1–21.5 g/t
Ag.
Table 10-2: 2018 PFS Testwork Scope
Sample ID
Head Assay
JK drop-
weight
tests (DWT)
E-GRG
Gravity
Separation
Bulk
Leach on
Gravity
Tailing
Cyanide
Destruction
Carbon
Modelling
Rheology
Solid/
Liquid
Separation
Arkose
x
x
—
x
x
x
—
x
x
MLDWT
x
x
—
x
x
x
x
x
x
ML-LG
x
—
x
x
x
—
—
—
—
ML-1
x
—
x
x
x
—
—
—
—
ML-2
x
—
—
x
x
x
—
—
—
HG
x
—
x
x
x
—
—
—
—
SLST
x
—
—
x
x
x
—
x
x
Mudstone
x
—
—
x
x
—
—
—
—
CMB
x
—
—
x
x
x
—
—
—
Note: “x” = test performed; “—” = not performed or not applicable
Table 10-3: Metallurgical Test Matrix for SGS Program 15944-002
Sample ID
Head Assay
Mineralogy
Analysis
Comminution
BRWi & BBWi
Bottle Roll Leach
Oxygen
Uptake
Bulk
Leach
Cyanide
Destruction
Year 1
x
x
—
x
x
—
—
Year 2
x
—
x
x
x
—
—
Arkose
x
—
x
x
—
—
—
Siltstone
x
—
x
x
—
—
—
Sinter
—
—
x
—
—
—
—
ML-LG
x
—
—
—
—
x
x
Note: “x” = test performed; “—” = not performed or not applicable
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Table 10-4: FS Production Composites Sample Composition
Sample
% Arkose
% Siltstone
% Sinter
Year 1
39.4
44.5
16.0
Year 2
49.4
44.3
6.3
Composites 4551-001 through 4551-006 were designated as Year 1 composites and composites 4551-007 through 4551-012 were
designated as Year 2 composites. Year 1 composites were prepared to represent a lithology make-up of 16% sinter, 44.5% siltstone and 39.4% arkose by mass. Year 2 composites were prepared to represent a lithology make-up of 6.3% sinter, 44.3%
siltstone and 49.4% arkose by mass as shown in Table 10-4.
A 15 kg master composite sample was generated, designated as 4551-013. This composite was
composed of select interval samples used in the variability composites. The lithology make-up of this composite was 6% sinter, 43% siltstone, and 51% arkose by mass.
10.4
Presentation and Discussion of Results
10.4.1
Ore Characterization and Deleterious Elements
Ore composition was investigated in SGS Program 15944-002. Selected head assays are presented in Table 10-5.
Table 10-5: Head Assays
Sample ID
Au
(g/t)
Au
(oz/ton)
Ag
(g/t)
Ag
(oz/ton)
Hg
(g/t)
ST
(%)
S2-S
(%)
SO4-S
(%)
CT
(%)
TOC
(%)
Cu
(g/t)
Fe
(%)
As
(g/t)
Year 1
9.56
0.306
12.9
0.413
2.054
0.22
0.08
0.14
0.09
0.09
13.7
0.69
167
Year 2
7.84
0.251
12.5
0.400
2.639
0.44
0.27
0.15
0.12
0.12
15.6
0.92
181
Arkose
9.66
0.309
11.7
0.374
2.066
0.18
0.08
0.1
0.06
0.06
11.6
0.58
119
Siltstone
24.71
0.791
34.2
1.094
2.156
0.42
0.26
0.14
0.35
0.35
15.7
0.93
183
ML-LG
1.69
0.054
8.48
0.271
1.858
0.43
0.25
0.15
0.04
<0.05
36.6
0.84
156
The conclusion of these results is that mercury is present in high enough concentrations to warrant removal and management,
and this has been incorporated into the flowsheet. Arsenic is present in the feed at concentrations ranging between 3.47–5.34 oz/ton (119–183 g/t) and is not expected to be problematic in processing. No other elements that may
cause issues in the process plant or concerns with product marketability were noted.
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10.4.2
Comminution Test Results
10.4.2.1 Hazen
1990
The historical comminution testwork conducted by Hazen in 1990 and as reported by RDI in 2012 is summarized in Table
10-6.
Table 10-6: Hazen 1990 Comminution Results
Description
Units
Sample Description
Zone 1
Zone 2
Zone 3
Composite
High Grade
Product Size,80% passing
µm
—
551
483
541
—
Bond rod mill work index, RWI
kWh/ton
—
18.0
17.2
17.6
18.2
Bond ball mill work index, BWI
kWh/ton
—
21.3
17.7
20.2
—
Bond abrasion index, Ai
0.711
0.783
0.529
0.714
—
10.4.2.2 SGS
Program 15944-001
JK drop-weight tests (DWT) were conducted on the Arkose Arkose Updated and MLDWT samples. The data were interpreted by JK Tech Pty Ltd (JK Tech) and a summary
of results is presented in Table 10-7.
Table 10-7: Summary of JK DWT
Results
Sample ID
SG
ta
A
b
Axb
Arkose
2.56
0.13
100
0.32
32.0
MLDWT
2.51
0.15
99.8
0.30
29.9
Note: The JKTech Drop-Weight test provides ore-specific parameters for use in the JKSimMet Mineral Processing Simulator
Software.
The ta parameter indicates resistance to abrasion. The Axb parameter indicates
resistance to Impact breakage.
The impact breakage data of these samples showed they can be classified as hard when compared to other samples in the
JKTech database. The JK DWT results were used by Ausenco to estimate the crusher work index at 20.9 kWh/ton.
10.4.2.3 SGS
Program 15944-002
Bond rod mill work indices are presented in Table 10-8.
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Table 10-8: Bond Rod Mill Grindability Test Results
Sample ID
Mesh of Grind
Work Index (kWh/ton)
Hardness Percentile
Category
Year 2
14
22.2
96
very hard
Arkose
14
19.2
82
hard
Siltstone
14
22.4
97
very hard
Sinter
14
22.5
97
very hard
Bond ball mill work indices are presented in Table 10-8.
Table 10-9: Ball Mill Work Indices
Sample ID
Mesh of Grind
Work Index (kWh/ton)
Hardness
Percentile
Category
Year 2
100
26.6
99
very hard
Arkose
100
20.8
88
hard
Siltstone
100
27.3
99
very hard
Sinter
100
32.0
100
very hard
Bond ball mill work indices were performed at a closing screen size of 100 mesh, or 150 µm.
The samples tested were categorized as hard to very hard; this finding aligns with previous findings from historical testwork.
10.4.3
Mineralogical Analysis
10.4.3.1
Hazen 1990
Mineralogical examinations of ore from Zones 1, 2 and 3 showed that they were similar and composed mainly of quartz and orthoclase feldspar. Minor amounts of
pyrite were noted, mostly less than 5 µm but ranging up to 20 µm, along with native gold ranging from 50–250 µm in Zones 1 and 3 and up to 600 µm in Zone 2.
10.4.3.2
SGS Program 15944-002
The mineralogical investigation was performed on the Year 1 sample which was stage crushed to a P80
size of 100 mesh (150 µm). A 100 g sample was extracted by riffle splitting for quantitative evaluation of materials by scanning electron microscopy (QEMSCAN) testing and 900 g was submitted for a gold deportment study. The gold
deportment subsample was concentrated using gravity methods and examined using the Tescan Integrated Mineral Analyzer (TIMA).
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Findings included:
•
Electrum accounts for 77.4% of the total gold grade; the remainder is present as native gold.
•
Gold association: The liberation of gold is high at 77.5%. Most of the remainder is associated with light
silicates.
•
Gold exposure: The exposure of gold (>20% exposure) is good at 89.1%. Gold which is well exposed (>20%
exposure) should be readily amenable to leaching.
•
Gold association by size and gold mineral sizes: the majority (81%) of gold mineral grains are
<30 µm in size, the non-liberated grains typically occur in association with light silicates, complex particles and rarely with oxides, pyrite and silver minerals. Gold grains coarser than 30 µm are liberated. Most gold
grains would be leachable.
•
Mineral composition is predominantly quartz (63.6%) and K-feldspar (30,7%), with trace amounts (<2%) of
clays, sericite/muscovite, plagioclase and other minerals. Pyrite is detected in trace amounts (0.30%). Chalcopyrite and other copper sulfides are present in trace amounts (0.03%).
10.4.4
Leach Tests
10.4.4.1
Evaluation of Grind Size, SGS Program 15944-002
The Year 2 sample was crushed in three stages to -2 mm. A single point grind calibration was conducted on a 1 kg charge in a laboratory rod mill to
determine the grind time required to achieve the fineness of grind. A series of standard bottle roll tests were conducted on the Year 2 sample at three grind sizes (P80 of 100 µm, 75
µm and 53 µm ) and two cyanide concentrations (0.5 and 1.0 g/L).
Leaching conditions were a pulp density of 45% solids, pH of
10.5–11 with lime addition and leach time of 24, 48 and 72 hours.
Residue grades decreased with finer grind, for all leach times evaluated.
A P80 grind size of 150 mesh (106 µm) was used in the FS; however, provision to grind finer
to 200 mesh (75 µm) was considered in sizing the ball mill.
10.4.4.2
Evaluation of Leach Time, SGS Program 15944-001
A 20 kg sample of each lithology (all nine samples) was ground and passed by a Knelson MD-3 concentrator. The concentrate obtained was further upgraded with a
Mozley C800 laboratory separator. The tailings from the Knelson concentrator and Mozley separator were combined and ground to a target P80 size of 150 mesh (106 µm) and submitted for bulk
leach testing by CIP or CIL.
For the bulk agitated leach tests, approximately 10 kg of gravity tailings was pulped to 45% solids by weight, pH was
adjusted to 10.5–11 with lime, dissolved oxygen (DO) was maintained at >6 ppm, 0.5 g/L of NaCN was added and 0.25 g/L NaCN was maintained throughout the leaching process. Carbon concentrations of 12 g/L and 15 g/L were
added for CIL and CIP respectively. The residence times were 48 hours and 72 hours for the CIL and CIP tests respectively. Carbon was added to the pulp at 48 hours for the CIP test. Pre-aeration of three hours was included for both tests.
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Relevant results from SGS Program 15944-001 that align with the selected flowsheet and include samples
representative of ore that is included in the 2018 PFS mine plan are shown in Figure 10-1. These results show that gold leaching is fast and complete within 24 hours.
Figure 10-1: Gold Leach Extraction Rate
Source: Ausenco, 2020
10.4.4.3
Evaluation of Leach Time, SGS Program 15944-002
A series of standard bottle roll tests were conducted on the Year 1, Year 2 and Arkose and Siltstone samples at two grind sizes (P80 of 100 µm and 75 µm) and two cyanide concentrations (0.5 and 1.0 g/L).
For each
test a 1.0 kg charge was ground to the target grind size and pulped to 45% solids by weight. The pH was adjusted to 10.5–11 using lime and DO was maintained at > 6 mg/L. Three hours of pre-aeration using air were applied to all
samples.
A lower level of confidence was placed in these results as the solution assay results were erratic; however, the same trends were seen as in
more reliable testwork, i.e. a fast initial leach rate and completion of the gold leach reaction within 24 hours.
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10.4.4.4 Evaluation
of Leach Time, McClelland Program MLI 4551
Twelve grade variability composite samples of 1 kg each were prepared for mechanical agitation leach testing. The samples were stage ground to 80% passing
106 µm in a laboratory steel ball mill. Samples were prepared in order of estimated increasing gold grade. Following each composite, the mill was cleaned by grinding barren silica sand.
After grinding, samples were slurried to 45% solids by weight and pH was adjusted to 10.8–11.2 by adding hydrated lime. Slurries were sparged with air
for three hours prior to leaching at 0.5 g/L sodium cyanide. Leaching was conducted by mechanically agitating the slurries in baffled, air sparged leaching vessels for 48 hours.
Results are presented in Figure 10-2 and Figure 10-3 and show the gold leach
rate flattening by 24 hours, supporting the selection of the leach time at 24 hours.
Figure 10-2: Gold Leach
Extraction Rate for Grade Variability Samples
Source: Ausenco, 2020
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Figure 10-3: Silver Leach Extraction Rate for Grade Variability
Samples
Source: Ausenco, 2020
McClelland commented that similar dips in the solution grades over time were observed as seen in the SGS program 15944-02 data, and that this is thought to be
indicative of the possible presence of preg- Updatedrobbing clays.
10.4.4.5
Effect of Pre-aeration, SGS Program 15944-002
A round of tests were carried out which included a three-hour pre-aeration step ahead of the leach. Tests were conducted at a P80 grind size of 100 µm, 45% solids, pH 10.5–11, and dissolved oxygen maintained at > Retained for consistency with the rest of Section 10 (and others in the report), where the
same notation is used7 mg/L for CN3 and >9 Added mg/L for CN9 and CN10 tests.
For tests conducted at 0.5 g/L cyanide addition with and
without pre-aeration, cyanide consumption reduced from 0.23 to 0.12 g/t with pre-aeration for the Year 1 sample and from 0.14 to 0.11 g/t for the Year 2 sample. From this investigation it can be concluded that pre-aeration is beneficial to
leach kinetics in all cases and to overall recovery, particularly for the Year 2 sample. A three-hour pre-aeration step was incorporated into the plant design.
10.4.4.6
Leach Reagent Consumption, SGS Program 15944-001, SGS Program 15944-002 and McClelland Program MLI
4551
Cyanide and lime consumption rates from all leach tests that included the three-hour pre-aeration step and conducted on
relevant lithologies are shown in Table 10-10.
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Table 10-10: Average Cyanide and Lime Consumption
Test Description
Cyanide addition (g/L)
Cyanide Consumption
Lime Consumption
(kg/t)
(lb/ton)
(kg/t)
(lb/ton)
Bottle roll, PFS
0.5
0.34
0.68
0.84
1.68
Bottle roll, FS
0.5
0.17
0.34
1.27
2.54
Bottle roll, FS
1.0
0.27
0.54
1.27
2.54
Agitated leach, FS
0.5
0.90
1.80
2.74
5.48
A cyanide consumption of 0.34 kg/t and lime consumption of 1.05 kg/t respectively were selected for use in
estimating plant operating costs. These values align with the bottle roll test results as these are believed to be a closer representation of plant consumption than the agitated leach tests.
10.4.4.7
Oxygen Uptake Test, SGS Program 15944-02
Two oxygen uptake tests were conducted on each of the Year 1 and Year 2 samples. Samples were ground to a
P80 size of 102 µm and pulped to 45% solids with water in a stirred glass reflux reactor at ambient temperature. The sample was agitated with an impeller using a Caframo mixer at 300 rpm
throughout the test (~150 rpm for readings). The pulp pH was adjusted to 10.5–11.0 and cyanide was added. Air was sparged into the pulp sample to maintain the dissolved oxygen at a target range of 10–13 mg/L for the first test and
6-8mg/L for the second test. The DO content of the slurry was measured for a total time of 15 minutes, at one-minute intervals. During these readings, the air sparge was removed from the pulp, remaining in the headspace of the vessel. DO readings
were taken at 0, 2, 4, 8, 12, 24, 30, and 36 hours.
The test results show that the oxygen uptake rate was very low, showing that the Year 1 and Year 2
samples were low oxygen consumers. Air was selected as the source of oxygen for the plant design.
10.4.4.8
Mercury Dissolution Test, SGS Program 15944-002
Mercury concentrations in the final (48 hour) solutions were 0.25 mg/L and 0.26 mg/L for arkose and siltstone samples, respectively. Mercury
analysis in the final (30 hour) solution samples for Year 1 pregnant solutions were 0.16 and 0.25 mg/L for tests with 0.5 and 1.0 g/L of cyanide addition respectively. For Year 2 pregnant solutions, the results were 0.08 and
0.18 mg/L for tests with 0.5 and 1.0 g/L of cyanide addition respectively.
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10.4.5
Cyanide Destruction
10.4.5.1
Historical Results
Cyanide destruction was investigated by SGS (Table 10-11) and acceptable results were achieved relative to the Project
design value of <15 mg/L weakly acid dissociable cyanide (CNWAD).
Table 10-11: Cyanide Destruction Test Results from Historical Work
Test Program
Sample Description
Test
Feed
Concentration
(CNWAD mg/L)
Product
Concentration
(CNWAD mg/L)
SGS Program 15944-001
Three lithology samples, continuous tests
(MLDWT-CIP, Arkose-CIP, SLST-CIP)
SO2/air
110–149
0.04– 0.10
10.4.5.2
SGS Program 15944-002 Results
A 10 kg bulk cyanide CIP leach test was performed on the ML-LG sample to produce cyanide-leached pulp for cyanide destruction testwork. This sample was
selected as it contained sulfide sulfur and iron concentrations representing the upper limits in the Year 1 and 2 samples. The test was conducted in a 20 L pail with an overhead mixer with three hours of pre-aeration. The test conditions were a
sample mass of 10 kg, grind size (P80) of 106 µm, pulp density 45% solids, NaCN concentration of 0.5 g/L, pH of 10.5–11 with lime addition, Carbon addition of 15 g/L after
10-hour leach, and a leach time of 48 hours.
Test results are shown in Table 10-12. The test achieved very low
levels of CNWAD (0.13 mg/L) under continuous operation. Reagent addition rates (SO2, copper sulfate and lime) were typical for this
process.
Table 10-12: Cyanide Destruction Test Results – Continuous Test
Test
ID
Conditions
Total Continuous Test
Feed
Pulp
Volume
(L)
Pulp
Solids
(%w/w)
Feed
CNWAD
(mg/L)
Test
pH
Test
DO
(mg/L)
Discharge
Pulp
Volume
(L)
Total
Run
Time
(min)
Retention
Time
(min)
Discharge
CNWAD
(mg/L)
Discharge
CNTotal
(mg/L)
Discharge
SCN
(mg/L)
Discharge
CNO
(mg/L)
Ratio
of
SO2-
CNWAD
(g/g)
SO2
Addition
(g/L
pulp)
Ratio
of Cu-
CNWAD
(g/g)
Ratio
of
Lime-
CNWAD
(g/g)
ML-
LG
16.9
40
200
8.6
5.2
14.5
140
51
0.13
0.34
6.9
330
4.23
0.71
0.06
2.1
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10.5
Metallurgical Variability
Metallurgical samples were selected in collaboration with Paramount to represent deposit variability with consideration of:
•
spatial variability of the mineralization, shown in Figure 10-4 below;
•
composites to investigate effect of feed grade variability over the grade range that occurs within the Mineral
Resource; and
•
composites to investigate variability due to lithology or rock group.
Figure
10-4: Drill Hole and Interval Locations for Samples in the SGS 2018
and 2020 and McClelland Programs
Source: RESPEC, 2026
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10.5.1.1
2018 PFS Sample Selection
Nine samples were submitted for metallurgical testing. Lithologies were identified by Ausenco, under the guidance of the Paramount technical team. Samples were
described as Arkose, MLDWT, Mixed Lithology Low Grade (ML-LG), Mixed Lithology Average Grade (ML-1), Mixed Lithology Average Grade (ML-2), Mixed Lithology High Grade (HG), Silt Stone (SLST), Mudstone and Clay Mixed Breccia (CMB).
Comminution SMC testing (Axb) was carried out on Arkose and Mixed Lithology samples, leach tests were carried out on all samples and continuous cyanide
destruction tests were carried out on Arkose, Mixed lithology and Silt Stone samples.
10.5.2
Sample Selection for SGS Program 15944-02
Six composite samples were selected by Paramount with input from Ausenco to represent the production composites for the proposed Year 1 and Year 2 of
operations, and the major lithologies, Arkose, Siltstone and Sinter (Table 10-3).
The metallurgical program was
performed on composites: Year 1, Year 2, Arkose, Siltstone, Sinter and un-used ML-LG sample from the 2017/2018 testwork program.
Since there was
insufficient sample available of the Year 1 composite for comminution testing, it was decided to test the comminution properties for each of the major lithologies for Year 1 as an alternative. A low-grade sinter sample was provided for comminution
testing. Comminution testing was performed on Year 2, Arkose, Siltstone and Sinter samples.
Leach testing was performed on Year 1, Year 2, Arkose and
Siltstone samples. Cyanide destruction testing was performed on the Mixed Lithology Low Grade sample which was selected as it contained sulfide sulfur and iron concentrations representing the upper limits in the Year 1 and 2 samples.
10.5.3
Sample Selection for McClelland Program MLI 4551
Samples tested at McClelland were made up from drill core as composites to represent the ore that will be mined during the first two years of production.
Twelve grade variability composite samples (4551-001 to 012) and one master composite sample (4551-013) were tested. Variability composite samples calculated gold and silver grades ranged from 3.57–13.13 g/t Au and 5.1–21.5 g/t
Ag.
Supplementary leach testwork to support recovery estimation was conducted.
10.6
Recovery Estimation
10.6.1
Leach Recovery, SGS Program 15944-001, SGS Program 15944-002 and McClelland Program MLI 4551
The data in Table 10-12 were used as the basis for estimation of recovery for this Report.
While the data includes leach tests that ran for longer than the selected leach time of 24 hours, the leach curves shown in Section 10.4 flatten out after 24 hours, giving the same recovery at longer leach times. These data were considered to
be sufficiently valid to be included in recovery estimation.
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Table 10-13: Leach Test Data Used for Recovery Estimation
Test
Campaign
Test
Number
Target
Grind
Size P80
(µm)
Retention
Time
(hours)
Leach/
CIL
Leach
Feed
Source
Cyanide
Addition
(g/L)
Cyanide
held at
(g/L)
Leach Feed
Grade,
Au
Calculated
(g/t)
Residue
Grade,
Au
(g/t)
Leach Feed
Grade,
Ag
Calculated
(g/t)
Residue
Grade,
Ag
(g/t)
Leach
Recovery,
Au
(%)
Leach
Recovery,
Ag
(%)
SGS
Program 15944-001
ML1-CIL-A
100
48
CIL
Whole ore
0.5
0.25
4.48
0.36
—
—
91.96
—
ML1-CIL-B
103
48
CIL
Whole ore
0.5
0.25
4.47
0.69
—
—
84.56
—
HG-CIL-A
89
48
CIL
Whole ore
0.5
0.25
10.01
0.67
—
—
93.30
—
ML1-CIL
99
48
CIL
Gravity
tailings
0.5
0.25
4.15
0.25
7.67
2.60
93.97
66.11
ML1-CIL2
104
48
Leach
CIP
Gravity
tailings
1.0
0.50
4.38
0.35
9.32
3.15
92.01
66.19
SLST-CIL
114
48
CIL
Gravity
tailings
0.5
0.25
3.96
0.25
10.13
2.75
93.69
72.85
LG-CIL
96
48
CIL
Gravity
tailings
0.5
0.25
1.62
0.29
8.41
2.85
82.07
66.11
HG-CIL
99
48
CIL
Gravity
tailings
0.5
0.25
8.88
0.34
15.60
2.40
96.17
84.62
Arkose-CIL
116
48
CIL
Gravity
tailings
0.5
0.25
2.89
0.39
8.17
3.35
86.51
59.00
MLDWT-CIL
107
48
CIL
Gravity
tailings
0.5
0.25
2.47
0.31
7.65
3.00
87.45
60.76
SGS Program 15944-002
Year 1-CN9
98
30
Leach
Whole ore
0.5
0.5
11.29
0.40
14.01
2.80
96.46
80.01
Year 1-CN10
98
30
Leach
Whole ore
1.0
1.00
11.33
0.37
14.07
2.70
96.73
80.82
Year 2-CN9
101
30
Leach
Whole ore
0.5
0.5
7.12
0.72
12.30
3.60
89.89
70.72
Year 2-CN10
101
30
Leach
Whole ore
1
1
7.15
0.51
12.26
2.70
92.87
77.98
Year 1-CN11
75
30
Leach
Whole ore
0.5
0.5
9.76
0.35
15.00
2.70
96.41
82.00
Year 2-CN11
74
30
Leach
Whole ore
0.5
0.5
7.10
0.39
15.04
3.20
94.51
78.73
Year 2-CN12
101
48
Leach
Whole ore
1
1
6.97
0.50
—
—
92.83
—
Year 2-CN13
74
48
Leach
Whole ore
1
1
6.99
0.42
—
—
93.99
—
Year 2-CN14
51
48
Leach
Whole ore
1
1
6.94
0.35
—
—
94.96
—
Arkose-CN1
99
48
Leach
Whole ore
0.5
0.5
11.80
0.51
13.33
2.60
95.68
80.49
Siltstone-CN1
105
48
Leach
Whole ore
0.5
0.5
17.92
1.18
18.07
2.20
93.42
87.83
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Test
Campaign
Test
Number
Target
Grind
Size P80
(µm)
Retention
Time
(hours)
Leach/
CIL
Leach
Feed
Source
Cyanide
Addition
(g/L)
Cyanide
held at
(g/L)
Leach Feed
Grade,
Au
Calculated
(g/t)
Residue
Grade,
Au
(g/t)
Leach Feed
Grade,
Ag
Calculated
(g/t)
Residue
Grade,
Ag
(g/t)
Leach
Recovery,
Au
(%)
Leach
Recovery,
Ag
(%)
McClelland Program MLI 4551
AL-7 4551-001
106
48
Leach
Whole ore
0.50
0.50
8.85
0.61
14.6
3.5
93.11
76.03
AL-9 4551-002
106
48
Leach
Whole ore
0.50
0.50
10.18
0.59
14.6
3.9
94.20
73.29
AL-5 4551-003
106
48
Leach
Whole ore
0.50
0.50
7.10
0.45
13.5
3.5
93.66
74.07
AL-3 4551-004
106
48
Leach
Whole ore
0.50
0.50
5.20
0.45
11.1
3
91.35
72.97
AL-11 4551-005
106
48
Leach
Whole ore
0.50
0.50
11.17
1.19
21.5
4.8
89.35
77.67
AL-1 4551-006
106
48
Leach
Whole ore
0.50
0.50
3.57
0.37
9.3
2.5
89.64
73.12
AL-6 4551-007
106
48
Leach
Whole ore
0.50
0.50
8.01
0.47
11
2
94.13
81.82
AL-10 4551-008
106
48
Leach
Whole ore
0.50
0.50
13.13
0.42
9
1.5
96.80
83.33
AL-2 4551-009
106
48
Leach
Whole ore
0.50
0.50
4.29
0.23
9.1
2
94.64
78.02
AL-12 4551-010
106
48
Leach
Whole ore
0.50
0.50
11.02
0.48
9.4
1.7
95.64
81.91
AL-8 4551-011
106
48
Leach
Whole ore
0.50
0.50
8.75
0.22
13.9
2.4
97.49
82.73
AL-4 4551-012
106
48
Leach
Whole ore
0.50
0.50
6.21
0.27
5.1
1.1
95.65
78.43
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10.6.1.1
Leach Recovery Estimate
The data in Table 10-12 were used to derive a relationship between leach feed and residue grades for both gold and
silver, as shown in Figure 10-4 and Figure 10-5.
Figure 10-5: Relationship Between Leach Feed and Residue Grades for Gold
Source: Ausenco, 2020
Figure 10-6: Relationship Between Leach Feed and Residue Grades for Silver
Source: Ausenco, 2020
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The following relationships were derived from the data in Figure 10-4
and Figure 10-5 to calculate leach gold recovery:
•
Leach Residue Grade = 0.0336 (Leach Feed Grade) + 0.2173
•
Leach Recovery = (1-leach residue grade/leach feed grade) * 100.
The following relationships were derived from the data in Figure 10-4 and Figure
10-5 to calculate leach silver recovery:
•
Leach Residue Grade = 0.112 (Leach Feed Grade) +1.4188
•
Leach Recovery = (1-leach residue grade/leach feed grade) * 100.
Predicted leach recovery is compared to recovery achieved in testwork for gold and silver in Figure 10-6 and Figure 10-7, respectively.
Figure 10-7: Predicted versus Measured
Recovery for Gold
Source: Ausenco, 2020
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Figure 10-8: Predicted versus Measured Recovery for Silver
Source: Ausenco, 2020
10.6.1.2
Estimation of Plant Losses
Additional plant losses for gold were estimated and are shown in Table 10-14.
Table 10-14: Estimated Additional Plant Losses for Gold
Description
Units
Values
Head Grade
g/t Au
≤6
>6 to ≤ 9
>9
Solution loss
%
0.33
0.35
0.37
Fine carbon loss
%
0.04
0.03
0.03
Other loss plant operation
%
0.10
0.10
0.10
Total additional plant losses
%
0.47
0.49
0.49
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Additional plant losses for silver were estimated and are shown in Table
10-15.
Table 10-15: Estimated Additional Plant Losses for Silver
Description
Units
Value
Solution loss
%
0.33
Fine carbon loss
%
0.06
Other loss plant operation
%
0.10
Total additional plant losses
%
0.49
10.6.1.3
Overall Recovery Estimate
Overall plant recovery for gold and silver is calculated as the leach recovery less the plant losses. Recovery was calculated monthly as a function of head
grades for gold and silver based on the feasibility study mine plan.
Mercury has been identified as the only deleterious element of consequences and
provisions have been added to the process flowsheet to manage the removal of it from the final product and capture and control it safely.
Arsenic is
present in the feed but is not expected to be problematic in processing. No other elements that may cause issues in the process plant or concerns with product marketability were noted.
10.7
Summary
Three recent testwork programs (SGS Program 15944-001, SGS 15944-02 and McClelland MLI 4551) were completed between 2017 and 2020 on samples from the Grassy
Mountain deposit to confirm design information and metallurgical response which would provide a basis for process flowsheet selection and recovery estimation.
Between the various recent testwork programs, composite samples representing major lithologies, Year 1 and Year 2 production composites and a range of head
grades aligned with the minimum and maximum values expected in the plant feed in the initial two years of production were tested.
The grade variability
composite samples calculated gold and silver grades ranged from 0.104–0.383 oz/ton Au (3.57–13.13 g/t Au) and 0.149–0.628 oz/ton Ag (5.1–21.5 g/t Ag).
Comminution testing showed that all the materials tested are considered very hard, with Bond ball mill work indices ranging from 20.8 to 32.0 kWh/ton.
Bottle roll and agitated batch leach tests showed that the samples were highly responsive to recovery by cyanidation at a grind size of 80% passing 150 mesh
(106 µm) or lower, with leach recoveries ranging from 82.1–97.5% for gold and 59.0–84.6% 59.0–84.6% Updatedfor silver, dependent on leach feed grade.
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Overall plant recoveries for gold are predicted to range between 89.5 and 94.9% for head grades of
0.096–0.58 oz/ton Au (3.3–17.4 g/t Au) respectively over the life of mine. Overall plant recoveries for silver are predicted to range between 62.7 and 80.4% for head grades of 0.161–0.523 oz/ton Ag
(5.5–17.9 g/t Ag) respectively over the LOM.
Cyanide destruction tests achieved <0.2 mg/L CNWAD, which is well within the maximum legislated value in Oregon of 30 mg/L.
Mercury grades were
in the range of 0.054–0.077 oz/ton (1.86–2.64 g/t) in the leach feed, and the concentration of mercury in solution after leaching ranged between 0.08 and 0.26 mg/L. A retort and gas collection and scrubbing system was incorporated into
the plant design to manage and control mercury in the process. Arsenic is present in the feed at concentrations ranging between 3.47 and 5.34 oz/ton (119 and 183 g/t) and is not expected to be problematic in processing.
10.8
Qualified Person’s Opinion on Data Adequacy
In the QP’s opinion, based on the testwork summarized in the Report and predictions made from that testwork in terms of mineralogy, plant design
considerations, recovery forecasts, and presence of deleterious elements, the predictions of proposed throughput and metallurgical performance are acceptable.
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11
MINERAL RESOURCE ESTIMATES
11.1
Introduction
The qualified person firm RESPEC completed the estimate of mineral resource presented herein.
11.2
Grassy Mountain project Data
RESPEC performed this estimate of the Grassy Mountain project’s mineral resources using data generated by Paramount and the historical operators
discussed in Section 7. Paramount provided these data to RESPEC.
11.2.1
Drill-Hole Database
The drill-hole data are in UTM Zone 11 NAD83 coordinates in US Feet. The database includes information from a total of 485 drill holes, 282 of which were
drilled in the area of the Grassy Mountain resources. This estimation of the project’s mineral resources directly uses assay data from 256 of these drill holes.
Prior to the 2016–2017 drilling program, Paramount provided RESPEC with a project drill-hole database. As discussed in Section 9.1, RESPEC audited
the historical drill data and made corrections as appropriate. RESPEC periodically updated the database with information acquired during Paramount’s subsequent drilling programs, including gold and silver assay data received directly from the
analytical laboratory.
11.2.2
Topography
As part of their 2016–2017 work program, Paramount conducted a drone aerial survey over the resource area and collected detailed topographic data. RESPEC
used the survey’s raw data to create a three-dimensional digital topographic surface for use in resource modeling.
11.3
Deposit Geology Relevant to Resource Modelling
The Grassy Mountain gold-silver deposit is hosted by arkoses, siltstones, mudstones, and sinters of the Grassy Mountain Formation. As presently drilled, it has
extents of 1,900 ft in the strike direction of the higher-grade mineralization (060° to 070°), approximately 2,700 ft perpendicular to the strike, and 1,240 ft in the vertical direction. The deposit is comprised of a
high-grade central core zone characterized by gold grades in excess of 0.03 oz/ton Au that lies within a broad envelope of low-grade mineralization. The central core includes mineralization, that is the
subject of the economic analysis discussed in the following sections of this feasibility study.
The central core zone extends almost 1,000 ft along
strike, about 450 ft perpendicular to strike, and up to 450 ft in the vertical direction. Sub-horizontal and subvertical extensions of the high-grade central-core mineralization extend outward into the low-grade envelope, likely due to
stratigraphic and structural controls. The base of the central core is very sharp, marked by a distinct drop in precious-metal grades. It is the lower limit of the strong silicification that typifies the entire Grassy Mountain deposit, including the
lower-grade envelope.
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The highest-grade mineralization (>~0.25 oz/ton Au) within the high-grade central core zone and its
stratigraphic and structural extensions is most frequently associated with thin (<2 inches), often banded, typically steeply dipping chalcedonic quartz + adularia veins and veinlets. However, there are examples of highest-grade mineralization
that have no apparent association with veins. Nor does the presence of veins guarantee high grades. The distribution of the highest-grade mineralization is somewhat erratic, although some systematic distribution is evident. For example,
highest-grade mineralization is characteristic of the basal portion of the central core, even as continuity remains limited. In addition, project geologists have hypothesized that the Grassy fault is important in the formation of the deposit. There
is evidence of an association between the Grassy fault (and other high-angle structural zones) and higher vein density and grades.
The stratigraphic
control of mineralization is expressed by lenses of generally concordant mineralization that extend outwards from the margins of the central core of high-grade mineralization and the low-grade envelope. Similar mineralized lenses are associated with
the upper portions of the mineralized structural zones that extend above the central core zone. Mineralization within the central core of the deposit may also have been influenced by the host stratigraphy. Arkose and siltstone are the most common
hosts of stratigraphically controlled mineralization, and both sides of the contacts of the interbedded units appear to be particularly favorable.
RESPEC
believes the Grassy Mountain gold- and silver-bearing hydrothermal fluids were introduced into the Grassy Mountain Formation along a series of 060°- to 070°-striking, steeply dipping (primarily to the southeast) structural zones that occur
over the full extents of the central core of the deposit. Minimal displacement is common across individual structures. The planar base of the deposit and the abrupt change to weakly mineralized and altered rocks below likely reflect the elevation at
which boiling in ascending hydrothermal fluids deposited high-grade mineralization. The unfocussed nature of fluid flow along the complex and heavily fractured structural zones resulted in the generally erratic deposition of high-grade
mineralization throughout the central core zone.
The waning stages of the mineralizing system appear to be manifested by what Newmont termed “clay
matrix breccias.” The breccias are primarily, if not entirely, post-mineral and post-silicification. They are primarily matrix-supported with rotated fragments (some with mineralized quartz veinlets) that range up to boulder-size. Newmont
hypothesized that the breccias formed during, “a period of late-stage boiling along pre-existing conduits as H2S and CO2 were
expelled from the system” (Jory, 1993). Observations of Paramount drill core suggests that the pre-existing conduits are the mineralized structural zones described above. The clay matrix breccias are frequently unconsolidated and have
geotechnical implications.
Post-mineral faulting slightly tilted the Grassy Mountain deposit and its host stratigraphy to the east.
RESPEC performed the gold and silver resource modeling within the geological concepts described above.
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11.4
Geologic Modeling
Paramount supplied RESPEC with a set of detailed cross-sectional lithological and structural interpretations that covers most of the extents of the Grassy
Mountain mineral deposit. RESPEC used the cross-sections to guide their modeling of the gold and silver mineralization.
The structural interpretations
were particularly critical to the modeling of the gold and silver mineral domains discussed in Section 11.7. RESPEC made minor modifications to Paramount’s structural interpretations and modeled additional structures that provide some
control for higher-grade mineralization.
11.5
Water Table and Oxidation Modeling
Because oxidation within the Grassy Mountain deposit is variable, accurate modeling of discrete oxide and/or unoxidized zones proved impracticable. The entire
deposit is characterized as mixed oxidized, partially oxidized, and unoxidized material, although the unoxidized portions typically occurring only locally.
Hydrologic conditions are discussed in Section 13.3. Other than potential impacts of down-hole contamination in RC drill holes (discussed in
Section 7.4.2), the presence or absence of groundwater did not impact the resource modeling.
11.6
Density Modeling
In 1990, Hazen Research, Inc. (Hazen) completed 314 measurements of bulk density. In addition, Atlas collected 61 bulk density measurements. Hazen determined
bulk density using the water-immersion method on samples of drill core. RESPEC does not know if Hazen wax-coated the samples with open spaces. The samples were categorized by gold grade ranges, but the specific drill intervals tested are not known.
Table 11-1 summarizes the Hazen densities (tonnage factors are presented in ft3/ton).
Table 11-1: Hazen Research, Inc. tonnage Factors
Zone
Mean
Median
Min
Max
Count
Grade Range (oz/ton Au)
OZ-1
12.8
12.8
13.7
12.3
63
<0.005
OZ-2
12.8
12.8
14.4
12.3
166
0.003–0.050
OZ-3
13.1
13.0
24.6
11.0
85
0.050–0.750
The Atlas completed their 61 bulk density determinations at their Gold Bar mine in Nevada. Steele (1990) described their
methodologies as “wet tests.” The same memorandum described the Hazen procedures as “wet and dry.” Based on these descriptions, RESPEC believes that Atlas tests were performed using the water-displacement method. However,
RESPEC cannot confirm the exact methods employed. The drill-core samples tested by Atlas are identified by drill interval, and their spatial locations within the deposit are known.
Newmont density tested 10 samples of drill core (Jory, 1993). Although the test results are not available, Jory (1993) stated that the results suggest
“a Grassy Mountain tonnage factor closer to 13.3 ft3/ton.”
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Paramount requested ALS complete bulk-density testing on 266 samples of core from the Atlas, Calico, and
Newmont drilling programs and 374 samples of core from Paramount’s 2016–2017 drill program. ALS made the determinations using the water-immersion method (ALS codes OA-GRA08). Coating with paraffin wax was implemented when necessary
(OA-GRA08A). Two of the sinter density determinations were anomalously high (low tonnage factors), and RESPEC removed them from the dataset.
RESPEC
examined the density data collected by Atlas and Paramount collectively and individually by rock types and gold domains. In general, average tonnage factors from the Atlas data for the lithological and grade subgroups are slightly lower (higher
density) than those determined by Paramount. Table 11-2 summarizes the combined Atlas and Paramount dataset grouped by modeled gold domain. The assay range for the low-grade gold domain (100) is ~0.006 to
~0.030 oz/ton Au, and the high-grade domain consists of assays > ~0.030 oz/ton Au.
Table 11-2: Combined
Atlas and Paramount tonnage Factors
Gold Domain
Mean
Median
Min
Max
Count
Block Model
100
13.3
13.0
21.5
11.6
341
13.5
200
13.0
12.9
14.7
12.4
275
13.5
100+200
13.2
12.9
21.5
11.6
616
n/a
0
14.8
14.5
23.0
11.2
83
14.8
Inclusive of the Hazen tests, the results indicate that the density associated with the Grassy Mountain mineralization is
consistent. Unmineralized rocks are distinctly less dense. This is likely a reflection of the strong silicification associated with all grades of mineralization. Unmineralized rocks have weaker silification or else lack it entirely.
RESPEC used the block model tonnage factors shown in Table 11-2 in the estimation of mineral resources. The tonnage
factors applied to mineralized material in the block model are slightly higher (lower density) than the measured mean values from core to account for voids related to the relatively high degree of fracturing in the Grassy Mountain deposit.
11.7
Gold and Silver Modeling
11.7.1
Mineral Domains
A mineral domain encompasses a volume of rock that ideally is characterized by a single natural grade population of a metal or metals that occurs within a
specific geologic environment. To define the mineral domains at Grassy Mountain, RESPEC identified the natural gold and silver populations by plotting all drill-hole assays on population-distribution graphs. Some distribution plots used only core
sample analyses. The analysis identified three grade populations each for gold and silver. However, the highest-grade populations of gold (>~0.25 oz/ton Au) and silver (>~0.4 oz/ton Ag) do not have sufficient continuity for confident modeling
of the domain. Therefore, RESPEC did not explicitly model these populations. Table 11-3 lists the approximate grade ranges of modeled gold and silver lower-grade (domain 100) and higher-grade (domain 200)
domains.
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Table 11-3: Approximate Grade Ranges of Gold and Silver Domains
Domain
oz/ton Au
oz/ton Ag
100
~0.006 to ~0.03
~0.04 to ~0.15
200
> ~0.03
> ~0.15
To model the gold and silver mineralization, RESPEC first interpreted gold and silver mineral-domain polygons individually on
a set of vertical, 50-ft spaced cross-sections looking northeast to azimuth 070° that span the extent of the deposit, then interpreted the mineral domains using the gold and silver drill-hole assay data, associated alteration and mineralization
codes, and Paramount’s sectional lithological and structural interpretations. During the sectional modeling, RESPEC extensively referred to core photographs, used them to discern the stratigraphic and structural controls of mineralization
discussed in Section 11.3 and modeled the domains accordingly. First, RESPEC modeled gold, then used the sectional gold-domain polygons to guide the silver domain modeling.
Due to the inherent variability of the Grassy Mountain mineralization, some of the high-grade domains (domain 200) included significant quantities of
low-grade mineralization. This variability precluded confident modeling of the highest-grade gold and silver population, and RESPEC did not define the mineralization separately from the high-grade gold and silver domains. From core observations, the
highest-grade gold population (>~0.25 oz/ton Au) strongly correlates with the presence of thin, often banded, quartz–chalcedony veins and veinlets and/or breccias. Visible gold is sometimes present. Most commonly, the high-grade veinlets
are steeply dipping—as assessed from drill-hole orientations and angles to core axes.
Although the grade change across the boundary between the
low– and high-grade domains is usually sharp, it is locally gradational. Commonly, the grade change across the sub-horizontal base of the high-grade domain is very abrupt, particularly in core holes, and is marked by a significant decrease in
the intensity of silicification.
The mineralization in the low-grade domain is much less variable than the higher-grade mineralization. This
mineralization is distal from the zone of boiling and related brecciation, and its distribution exhibits strong stratigraphic controls.
RESPEC pressed
the cross-sectional gold and silver mineral-domain envelopes horizontally to the drill data within each sectional window and sliced them at 10-ft vertical intervals to match the mid-bench elevations of the block model, then used these slices to
create gold and silver mineral-domain polygons on 10-ft spaced level plans at mid-block locations. Slices of triangulated surfaces of the steeply dipping structures that influence the distribution of higher-grade mineralized zones guided the level
plan interpretations.
Figure 11-1 to Source: RESPEC, 2026
Figure 11-4 provide cross-sections showing geology and gold and silver mineral domains in the central portion of the
Grassy Mountain deposit.
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Figure 11-1: Cross-section 3050 Showing Geology and Gold Domains
Source: RESPEC, 2026
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Figure 11-2: Cross-section 3050 Showing Geology and Silver Domains
Source: RESPEC, 2026
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Figure 11-3: Cross-section 3250 Showing Geology and Gold Domains
Source: RESPEC, 2026
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Figure 11-4: Cross-section 3250 Showing Geology and Silver Domains
Source: RESPEC, 2026
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11.7.2
Assay Coding, Capping, and Compositing
To code the drill-hole samples, RESPEC used the cross-sectional gold and silver mineral domain polygons and determined assay caps by inspecting the population
distribution plots of the coded assays, by domain, and identifying high-grade outliers appropriate for capping (Table 11-4). In the definition of the assay caps, RESPEC also considered descriptive statistics
of the coded assays by domain, visually reviewed the spatial relationships of the possible outliers and evaluated their potential impacts during grade interpolation. The number of samples subjected to capping and the chosen capping grades were
minimized because of the application of search restrictions described in Section 11.7.4.
Table 11-4:
Grassy Mountain Gold and Silver Assay Caps by Domain
Domain
oz/ton Au
Number Capped
(% of Samples)
oz/ton Ag
Number Capped
(% of Samples)
0
0.090
8(<1%)
0.120
12(<1%)
100
0.300
3(<1%)
0.600
4(<1%)
200
10.000
4(<1%)
7.000
2(<1%).
In addition to the low- and high-grade domain capping, RESPEC assigned samples outside the modeled domains as Domain 0 and
capped them as shown in Table 11-4. Table 11-5 and Table 11-6 provide descriptive statistics of the capped and uncapped coded
gold and silver assays.
Table 11-5: Descriptive Statistics of Grassy Mountain Coded Gold Assays
Domains
Assays
Count
Mean
(oz/ton Au)
Median
(oz/ton Au)
Std. Dev.
CV
Min
(oz/ton Au)
Max
(oz/ton Au)
0
Au
23,361
0.002
0.001
0.007
3.45
0.000
0.732
Au Cap
23,361
0.002
0.001
0.004
2.15
0.000
0.090
100
Au
24,808
0.013
0.011
0.011
0.82
0.000
0.561
Au Cap
24,808
0.013
0.011
0.010
0.77
0.000
0.300
200
Au
7,523
0.108
0.044
0.441
4.09
0.000
21.698
Au Cap
7,523
0.107
0.044
0.405
3.79
0.000
10.000
100+200
Au
32,331
0.033
0.013
0.209
6.27
0.000
21.698
Au Cap
32,331
0.033
0.013
0.193
5.81
0.000
10.000
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Table 11-6: Descriptive Statistics of Grassy Mountain Coded Silver
Assays
Domains
Assays
Count
Mean
(oz/ton Ag)
Median
(oz/ton Ag)
Std. Dev.
CV
Min
(oz/ton Ag)
Max
(oz/ton Ag)
0
Ag
20,921
0.009
0.005
0.011
1.19
0.000
0.496
Ag Cap
20,921
0.009
0.005
0.010
1.11
0.000
0.120
100
Ag
13,292
0.071
0.064
0.040
0.57
0.003
1.138
Ag Cap
13,292
0.071
0.064
0.039
0.55
0.003
0.600
200
Ag
6,646
0.262
0.200
0.400
1.52
0.005
18.600
Ag Cap
6,646
0.260
0.200
0.310
1.19
0.005
7.000
100+200
Ag
19,938
0.132
0.085
0.246
1.86
0.003
18.600
Ag Cap
19,938
0.131
0.085
0.199
1.51
0.003
7.000
RESPEC composited the capped assays to 5-ft down-hole intervals that respected the mineral domain boundaries. The 5-ft composite length is equal to the sample length of RC drill samples. To retain the inherent variability of the Grassy Mountain mineralization in the resource modeling, RESPEC minimized the compositing and did
not apply a shorter composite length to avoid decomposition the majority of the assay samples. Descriptive statistics of Grassy Mountain composites are shown in Table 11-7 for gold and
Table 11-8 for silver.
Table 11-7: Descriptive Statistics of Grassy Mountain Gold Composites
Domain
Count
Mean
(oz/ton Au)
Median
(oz/ton Au)
Std. Dev.
CV
Min
(oz/ton Au)
Max
(oz/ton Au)
0
23,452
0.00
0.00
0.00
2.15
0.00
0.09
100
24,213
0.01
0.01
0.01
0.74
0.00
0.30
200
6,738
0.11
0.05
0.35
3.30
0.00
9.89
100+200
30,951
0.03
0.01
0.17
5.09
0.00
9.89
Table 11-8: Descriptive Statistics of Grassy Mountain Silver Composites
Domain
Count
Mean
(oz/ton Ag)
Median
(oz/ton
Ag)
Std.
Dev.
CV
Min
(oz/ton Ag)
Max
(oz/ton Ag)
0
20,910
0.009
0.005
0.010
1.100
0.000
0.120
100
12,985
0.071
0.067
0.038
0.530
0.003
0.600
200
6,137
0.260
0.200
0.295
1.140
0.005
7.000
100+200
19,122
0.131
0.085
0.191
1.460
0.003
7.000
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11.7.3
Block Model Coding
RESPEC used level-plan mineral-domain polygons to code a three-dimensional block model comprised of 5 ft x 10 ft x 10 ft blocks (model x, y, z) with a model
bearing of 340°. RESPEC chose the block size most appropriate for the underground mining scenario evaluated in this feasibility study.
Using the
midblock level plan polygons, RESPEC coded the volume percentage of each of the two gold and silver domains into each model block, calculated the partial percentages of the model blocks that are partially or entirely outside the low- and high-grade
domains, and stored the volume percentages of the gold and silver mineral domains within each block. RESPEC also coded the block model using the digital topographic surface described in Section 11.2.2.
Employing the bulk density values discussed in Section 11.6, RESPEC assigned values so that blocks coded with any partial percentage of gold or silver
have a density of 13.5 ft3/ton, and entered a value of 14.8 ft3/ton all other blocks.
11.7.4
Grade Interpolation
Table 11-9 summarizes the parameters applied to the gold-grade estimations at Grassy Mountain. RESPEC completed the
grade interpolation in three passes using length-weighted composites within two estimation areas. Estimation area 10 dips shallowly at about -15° and encompasses most of the stratigraphically controlled mineralization in the Grassy Mountain
deposit. Estimation area 20 is comprised of mineralization in the west–southwestern portion of the deposit where the dips of the stratigraphic units steepen to approximately -20°. As Table 11-9
shows, the low-grade gold and silver domains and the areas outside modeled domains were entirely estimated using search ellipses that reflect these stratigraphic orientations.
The high-grade gold and silver domains exhibit both sub-horizontal (stratigraphic) and high-angle (structural) controls. To prioritize estimation of the
highest-grade mineralization—which is most commonly associated with steeply dipping veinlets—the first estimation pass of the high-grade domain reflects high-angle structural controls (Table 11-9,
estimation area 10, domain 200, pass 1). The second estimation pass of the high-grade domain applied a search ellipse reflective of stratigraphic control using the same search distance as pass 1 (50 ft). The second pass did not overwrite blocks
with grades estimated during pass 1. The third and final estimation pass was an isotropic pass without either a structural or stratigraphic bias. It was used to estimate domain 200 grades into blocks in the outer extents of the domain that were not
estimated by the first two passes.
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Table 11-9: Estimation Parameters
Estimation Pass – Au + Ag Domain
Search Ranges (ft)
Composite Constraints
Major
Semi-Major
Minor
Min
Max
Max/Hole
Pass 1 – Domain 0 + 100
100
100
50
2
15
3
Pass 2 – Domain 0 + 100
200
200
100
2
15
3
Pass 3 – Domain 0 + 100
310
310
310
1
15
3
Pass 1 + 2 – Domain 200
50
50
16.7
2
15
3
Pass 3 – Domain 200
110
110
110
1
15
3
Restrictions on Search
Ranges
Domain
Grade Threshold
Search Restriction Distance
Estimation Pass
Au 200
>0.30 oz/ton Au
35 ft
2
Au 0
>0.01 oz/ton Au
30 ft
1, 2, 3
Ag 0
>0.04 oz/ton Ag
30 ft
1, 2, 3
Search Ellipse Orientations
Estimation Area
Au + Ag Domains and Controls
Major Bearing
Plunge
Tilt
Estimation Pass
10
[Most of the Deposit]
Domain 0 + 100 – Stratigraphic
0°
0°
-15°
1, 2, 3
Domain 200 –Structural
070°
0°
-85°
1
Domain 200 – Stratigraphic
070°
-10°
0°
2
Domain 200 – Stratigraphic
0°
0°
0°
3
20
[WSW End of the Deposit]
Domain 0 + 100 + 200 – Stratigraphic
070°
0°
20°
1, 2, 3
Only a very limited portion of the high-grade gold and silver domains lie in estimation area 20.
Statistical analyses of coded assays and composites, including coefficients of variation and population-distribution plots, indicate that the high-grade gold
and silver domains capture multiple populations. RESPEC restricted the search distances because these multiple populations lack sufficient continuity to be explicitly modeled as separate domains and the initial estimation runs without the
restrictions resulted in unrealistic volumes and unrealistic distribution of high grades in the block model. The search restrictions limit the distance from a given composite above a chosen gold or silver grade that can be used in grade
interpolation. RESPEC finalized the search-restriction grades and distances after running multiple interpolation iterations to test the effects of various search-restriction parameters.
RESPEC interpolated gold and silver grades using inverse-distance to the third power (ID3), ordinary-kriging (OK), and nearest-neighbor (NN) methods and
reported this estimate of mineral resources using the ID3 interpolations because ID3 produced results more representative of the geology and distribution of drill-hole assay data than those obtained by OK. To check the ID3 and OK interpolations,
RESPEC completed the NN estimation.
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RESPEC performed the estimation passes independently for each of the mineral domains only using composites
coded to a particular domain to estimate grade into blocks coded by that domain. To enable the calculation of weight-averaged gold and silver grades for each block, RESPEC coupled the estimated grades with the partial percentages of their respective
mineral domains and the outside-domain volumes. Therefore, the final resource grades, and their associated resource tonnages, are fully block-diluted.
11.7.5
Model Checks
To assure close agreement, RESPEC compared gold and silver domain volumes coded into the block model as partial percentages to the volumes of both the
cross-sectional and level-plan mineral-domain polygons, visually checked all block-model coding, and used a polygonal estimate that used the cross-sectional domain polygons to check the ID3 estimation results and the NN and OK estimates. The checks
identified no unexpected relationships between the check estimates and the inverse-distance estimate. To check both the global and local estimation results, RESPEC evaluated various grade-distribution plots of assays, composites, and NN, OK, and ID3
block grades. Finally, RESPEC visually compared the ID3 grades to the drill-hole assay data in detail to assure that reasonable results were obtained, placing particular emphasis on the evaluation of the distribution and tenor of the high-grade gold
and silver estimates.
11.8
Grassy Mountain Mineral Resources
11.8.1
Pit Optimizations, Cutoff Grades and Reporting Prices
The Grassy Mountain deposit has the potential to be mined by open-pit methods. While the mineral reserves discussed in Section 12 are estimated on the
basis of a proposed underground-mining scenario, these mineral reserves represent only a small subset of the entire Grassy Mountain gold–silver deposit. The reported mineral resources reflect potential open-pit extraction and milling as the
primary scenario (mineral resources potentially amenable to open pit mining methods), with the potential underground mining of a very small quantity of material lying outside of the lower portions of the open pit as a secondary scenario (mineral
resources potentially amenable to underground mining methods). The mineral reserves discussed in Section 12 were converted primarily from the potential open-pit resources, with a small amount converted from the underground resource estimate.
To meet the requirement of reasonable prospects for eventual economic extraction for the portion of the mineral resources potentially amenable to open
pit mining methods, RESPEC ran a pit optimization using the parameters summarized in Table 11-10.
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Table 11-10: Pit Optimization Parameters
Item
Value
Unit
Mining Cost
3.14
$/ton
Processing Cost
16.33
$/ton processed
Process Rate
5,000
tons-per-day processed
General and Administrative (G&A) Cost
2.79
$/ton processed
Au Price
3,100
$/oz
Ag Price
34
$/oz
Au Recovery
80
Percent
Ag Recovery
60
Percent
Royalty
1.5%
NSR
Au Refining Cost
5.00
$/oz produced
Ag Refining Cost
0.50
$/oz produced
RESPEC used the pit shell created by this optimization to constrain the mineral resources potentially amenable to open-pit
mining methods, with the added constraint of a gold-equivalent cut-off grade of 0.008 oz/ton AuEq applied to all model blocks lying within the optimized pit. RESPEC calculated the gold-equivalent cut-off grade using the processing and general and
administrative costs and the gold price, recovery, refining cost, and royalty provided in Table 11-10. The mining cost is not included in the determination of the applied internal cut-off grade because all
material will potentially be removed from the conceptual pit and the cut-off grade is applied only to the decision to send the mined materials for processing or to the waste-rock storage facilities. Therefore, the reference point at which the
mineral resources are defined is at the top of the pit, where material equal to or greater than the cut-off grade would be processed.
The gold equivalent
grade (oz/ton AuEq) of each model block was calculated as follows:
oz/ton AuEq = oz/ton Au + (oz/ton Ag ÷ 129)
The silver-to-gold equivalency factor of 129 was derived from the metal prices and recoveries in Table 11-10.
The metal prices used in the pit optimization and the determination of the gold-equivalent cut-off grade and gold-equivalency factor were $3,100/oz for gold
and $34/oz for silver. RESPEC chose the metal prices based on consensus commodity price forecasts in March 2026 and on prices used to report resources recently filed on SEDAR. When this mineral resource estimate was completed, several recently filed
technical reports provided resources at gold prices between $2,500 and $3,100/oz Au, the spot price for gold was over $4,500/oz Au, and the three-year moving-average price was about $2,835/oz Au and rising. The spot price for silver was over $60/oz
Ag, and the three-year moving-average price was about $36/oz Ag and rising.
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To estimate mineral resources potentially amenable to underground mining methods, RESPEC applied a cut-off of
0.070 oz/ton AuEq to blocks lying immediately outside of the optimized pit that could reasonably be accessed from the resource pit. Table 11-11 lists the parameters used to calculate the underground
cut-off grade. The parameters used to estimate the very limited quantity of resources lying outside of the resource pit potentially amenable to underground extraction (less than 500 oz Au) are derived from, but more optimistic than, those used to
define the mineral reserves discussed in Section 12.
Table
11-11: Parameters Used to Determine Cut-Off Grade for Mineral
Resources Potentially Amenable to Underground Mining Methods
Item
Value
Unit
Mining Cost
141.77
$/ton
Processing Cost
39.09
$0/ton processed
Process Rate
5,000
tons-per-day processed
General and Administrative Cost
20.15
$/ton processed
Au Price
3,100
$/oz
Ag Price
34
$/oz
Royalty
1.5%
NSR
AuEq Recovery
92.8
Percent
Refining Cost
7.22
$/oz produced
RESPEC based both the open-pit and underground resource estimates on a 5,000-tons-per-day processing rate, with processing
assumed to consist of crushing and milling followed by CIL recovery.
11.8.2
Mineral Resources
The Grassy Mountain mineral resources exclusive of the resources that have been converted to mineral reserves are presented in Table 11-12. Mineral resources that are not mineral reserves do not have demonstrated economic viability.
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Table 11-12: Grassy Mountain Gold and Silver Resources –
Exclusive of Mineral Reserves
Resources
Cut-off Grades (oz/
ton Au)
Metallurgical
Recovery
Amount
(tons)
Grades
oz/ton Au
oz/ton Ag
Measured Mineral Resources
33,700,000
0.015
0.061
Inside Pit: 0.008
Outside Pit: 0.07
Au – 80
Ag – 60
%
%
Indicated Mineral Resources
21,887,000
0.021
0.081
Inside Pit: 0.008
Outside Pit: 0.07
Au – 80
Ag – 60
%
%
Measured + Indicated Mineral Resources
55,587,000
0.017
0.069
Inside Pit: 0.008
Outside Pit: 0.07
Au – 80
Ag – 60
%
%
Inferred Mineral Resources
3,779,000
0.019
0.056
Inside Pit: 0.008
Outside Pit: 0.07
Au – 80
Ag – 60
%
%
Notes:
•
RESPEC is the qualified person firm responsible for the mineral resources estimate.
•
Mineral resources are comprised of all model blocks at a 0.008 oz/ton AuEq cut-off that lie within an optimized
pit plus blocks at a 0.070 oz/ton AuEq cut-off that lie outside of the optimized pit.
•
oz/ton AuEq (gold equivalent grade) = oz/ton Au + (oz/ton Ag ÷ 129).
•
Mineral resources summarized in the table immediately above are reported exclusive of the mineral resources
converted to mineral reserves. Mineral resources that are not mineral reserves do not have demonstrated economic viability.
•
Mineral resources potentially amenable to open pit mining methods are reported using a gold price of $3,100/oz, a
silver price of $34/oz, a throughput rate of 5,000 tons/day, assumed metallurgical recoveries of 80% for Au and 60% for Ag, mining costs of $3.14/ton mined, processing costs of $16.33/ton processed, general and administrative costs of $2.79/ton
processed, and refining costs of $5.00/oz Au and $0.50/oz Ag produced. Mineral resources potentially amenable to underground mining methods are reported using a gold price of $3,100/oz, a silver price of $34/oz, a throughput rate of 5,000 tons/day,
assumed metallurgical recoveries of 92.8% gold equivalent, mining costs of $141.77/ton mined, processing costs of $39.09/ton processed, general and administrative costs of $20.15/ton processed, and refining costs of $5.00/oz gold equivalent
produced.
•
The effective date of the mineral resources estimate is February 28, 2026, and the effective date of the
database on which the Mineral Resources estimate is based is May 1, 2018;
•
Rounding may result in apparent discrepancies between tons, grade, and contained metal content.
The mineral resources exclusive of mineral reserves contain 490,000 oz of gold and 2,065,000 oz of silver classified as measured,
462,000 oz of gold and 1,777,000 oz of silver classified as indicated, and 73,000 oz of gold and 210,000 oz of silver classified as inferred.
The Grassy
Mountain project mineral resources inclusive of the resources that have been converted to mineral reserves are summarized in Table 11-13.
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Table 11-13: Grassy Mountain Gold and Silver Resources –
Inclusive of Mineral Reserves
Resources
Cut-off Grades
(oz/ton Au)
Metallurgical
Recovery
Amount
(tons)
Grades
oz/ton Au
oz/ton Ag
Measured Mineral Resources
33,999,000
0.016
0.063
Inside Pit: 0.008
Outside Pit: 0.07
Au – 80
Ag – 60
%
%
Indicated Mineral Resources
23,795,000
0.034
0.098
Inside Pit: 0.008
Outside Pit: 0.07
Au – 80
Ag – 60
%
%
Measured + Indicated Mineral Resources
57,794,000
0.023
0.077
Inside Pit: 0.008
Outside Pit: 0.07
Au – 80
Ag – 60
%
%
Inferred Mineral Resources
3,779,000
0.019
0.056
Inside Pit: 0.008
Outside Pit: 0.07
Au – 80
Ag – 60
%
%
Note: Footnotes to Table 11-12 are also applicable to this table, with the exception
that the mineral resources summarized in the table immediately above are inclusive of the resources that have been converted to mineral reserves. This table is not additive to Table 11-12.
The mineral resources inclusive of mineral reserves contain 540,000 oz of gold and 2,142,000 oz of silver classified as measured, 817,000 oz of gold and
2,325,000 oz of silver classified as indicated, and 73,000 oz of gold and 210,000 oz of silver classified as inferred.
As of the effective date, RESPEC
is not aware of any unusual environmental, permitting, legal, title, taxation, socio-economic, marketing, political, or other relevant factors not discussed in this feasibility study that could materially affect the mineral resource estimates.
Figure 11-5 through Figure 11-8 are cross-sections through the central portion
of the Grassy Mountain deposit that show estimated block-model gold and silver grades. These figures correspond to the mineral-domain cross-sections presented in Figure 11-1 to Figure 11-4.
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Figure 11-5: Cross-section 3050 Showing Block-Model Gold Grades
Source: RESPEC, 2026
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Figure 11-6: Cross-section 3050 Showing Block-Model Silver Grades
Source: RESPEC, 2026
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Figure 11-7: Cross-section 3250 Showing Block-Model Gold Grades
Source: RESPEC, 2026
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Figure 11-8: Cross-section 3250 Showing Block-Model Silver Grades
Source: RESPEC, 2026
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11.8.3
Classification
Uncertainties that impact resource classification at Grassy Mountain include: (i) the preponderance of vertical RC holes drilled by historical operators;
(ii) the potential for poor sample quality in some portions of the RC holes; and (iii) the adequacy of the drill-hole spacing in the higher-grade core of the deposit, where the definition of structural controls on higher-grade
mineralization is critical and variability in the highest-grade gold population is high.
Atlas drilled 180 of the 256 holes that contributed data to the
grade estimation of the current mineral resources. All but four of Atlas’s holes were drilled vertically, and only nine of Atlas’s holes were core. Due to the emerging understanding of the importance of high-angle structural controls to
the higher-grade mineralization, all operators after Atlas, including Paramount, emphasized angled core holes in their drilling programs. A total of 59 core holes, including 27 drilled by Paramount, and 55 angled RC and core holes, including 18
drilled by Paramount, support the current resource estimates, almost all of them drilled within the central, higher-grade core of the deposit. This post-Atlas drilling, and particularly the Paramount program planned in coordination with RESPEC,
significantly enhanced RESPEC’s confidence in the geological understanding of the Grassy Mountain deposit and decreased uncertainties in the resource estimation related to the relative lack of angled core holes in the historical drilling.
There is an inherent risk of down-hole contamination in RC drilling, particularly below the water table. RESPEC identified 21 RC holes with suspected
intervals of down-hole contamination, all within the deepest portion of the central core of the deposit where groundwater was encountered in drilling. The samples from these intervals were excluded from use in the resource estimation.
The central, higher-grade core of the deposit—which is critical to the potential economic viability of any mining operation at Grassy Mountain—has
predominantly been drilled at hole spacings of about 30 to 50 ft. Even at this tight drill spacing, in many cases the highest-grade gold mineralization (>~0.2 oz/ton Au) could not be confidently correlated from drill hole to drill hole. Because
the highest-grade population could not be confidently modeled as its own mineral domain, these high-grade samples were included in domain 200, which encompassed grades greater than approximately 0.03 oz/ton Au. While RESPEC took special care to
properly represent the highest-grade population within this domain during grade estimation, its inclusion within the domain creates increased grade variability and adds uncertainties.
The risk imparted by the variability of the highest-grade gold mineralization influenced the choice of estimation parameters applied to mineral domain 200
(Table 11-9), including: (i) the use of a tight search ellipse (3:1 ratio of major and semi-major axes to the minor axis); (ii) limiting the search distances of estimation pass 1 and pass 2 to a
maximum of 50 ft (which still resulted in only a small proportion of the model blocks in the core zone of the deposit to be estimated in pass 3); and (iii) a further restriction on the search distance in pass 2 that limits the influence of
composites grading in excess of 0.3 oz/ton Au to 35 ft. (Pass 2 estimates grade respecting subhorizontal lithologic controls.)
In consideration of the
uncertainties discussed above and the steps taken to mitigate these uncertainties, the most significant risk that remains in the current Grassy Mountain mineral resource estimation is related to the modeling of the highest-grade gold mineralization
in the central core of the deposit. While visual and statistical evaluations give RESPEC confidence that the volume of the modeled highest-grade population properly respects its proportional representation as defined by the unclustered drill data,
the modeled locations of these grades in the block model likely vary from reality as distances from the drill data increase.
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RESPEC classified the Grassy Mountain mineral resources according to the criteria presented in Table 11-14 and applied the criteria to the estimation of gold grades because gold is much more economically significant than silver.
Table 11-14: Resource Classification Parameters
Class
Criteria
Distance of Block Centroid to Nearest
Composite
Measured
All estimated blocks coded to Au Domain 200 with or without Au Domain 100 coding
< 10 ft
All estimated blocks coded exclusively to Au Domain 100
< 50 ft
Indicated
All estimated blocks coded to Au Domain 200 with or without Au Domain 100 coding not classified as measured
< 50 ft
All estimated blocks coded exclusively to Au Domain 100 not classified as measured
< 100 ft
Inferred
All other estimated blocks
Considering the preceding discussion related to uncertainties in the resource modeling, RESPEC used two sets of criteria in
the definition of measured and indicated classifications of the resource model blocks. RESPEC applied one set of more restrictive parameters to all blocks coded as having any percentage of gold domain 200 (the high-grade domain), and another, less
restrictive set of criteria to all other blocks which are coded entirely to domain 100 (the lower-grade gold domain). Domain 200 includes the central core zone of the deposit and thin, structurally and stratigraphically controlled mineralization
that extends outward from the core zone. Domain 100 is comprised of the much larger, lower-grade halo of mineralization that encompasses domain 200. Domain 100 mineralization has much more extensive grade continuity and is less influenced by
discreet structural controls. Therefore, the distance criteria required in domain 100 for measured and indicated classifications are significantly less restrictive than those applied to blocks coded to domain 200.
Despite the relatively restricted distances of measured and indicated blocks from the drill data used to estimate grades, the tight drill spacing that
characterizes the deposit significantly limits the quantity of inferred material.
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11.9
Additional Comments on the Modeling of the Mineral Resources
RESPEC estimated the current Grassy Mountain mineral resources in consideration of potential mining by open pit methods and a very minor amount of potential
underground-mineable resources that lie immediately outside of the pit walls. However, an alternate scenario is also realistic, whereby only the higher-grade portion of the deposit is mined exclusively by underground methods. This latter scenario
was chosen to define the mineral reserves discussed in Section 12. RESPEC constructed the resource model to accommodate both potential open-pit and underground mining scenarios. The 5 x 5 x 10 ft block size fits seamlessly with the reserve
stope optimization discussed in Section 12, while the blocks could easily be re-blocked to a larger size (e.g., 20 x 20 x 20 ft) to accommodate open-pit engineering requirements. All other modeling steps and inputs RESPEC used to estimate
the Au and Ag resources—including the mineral-domain modeling, grade capping, compositing, grade estimation, density assignment, and classification—were completed independent of potential mining method.
As previously discussed, during resource modeling RESPEC identified structural zones as the principal controls of the high-grade mineralization within the
central core of the Grassy Mountain deposit. This structurally controlled mineralization has significant grade variability, which creates modeling uncertainties with respect to the location of the estimated high grades as distances from drill data
increase. While the risk imparted by the location uncertainty would be low in an open-pit mining scenario, underground mining requires far greater spatial accuracy. The current model is not sufficiently precise for use in underground mining. To
properly inform an underground mining operation’s short- and long-term resource models and refine geotechnical modeling and final stope designs, the central core of the Grassy Mountain deposit would require properly oriented, closely spaced
definition drilling. In the short term, RESPEC strongly recommends drilling from the surface prior to mining to reduce the uncertainties in the high-grade mineralization model. Drilling on tighter spacing for more precise delineation of the
high-grade mineralization and stope design would take place from underground. Additional drilling would also be important from a geotechnical standpoint, again primarily to inform an underground mining operation, because the mineralized structures
are typically characterized by poor to very poor rock quality.
There are 14,947 sample intervals in the drill-hole database that have gold assays but no
silver analyses. In most cases, entire drill holes were not assayed for silver. For example, some of the early Atlas holes and all the Newmont holes were not assayed for silver. A total of 4,720 of the sample intervals lacking silver assays lie
within the domains that form the basis of the gold and silver resource estimates, while 19,938 sample intervals used in the resource estimates do have silver analyses. The effect of the lower quantity of silver analyses on the resource estimate is
mitigated by the fact that relative to gold, silver adds little value to any potential mining operation.
RESPEC believes that any factors that would
likely influence the prospect of economic extraction have either been addressed or could be resolved by further drilling.
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12
MINERAL RESERVE ESTIMATES
12.1
Introduction
Mineral Reserves were estimated by Qualified Persons of RESPEC and classified in order of increasing confidence into Probable and Proven categories to be in
accordance with definitions in Subpart 229.1300 – Disclosure by Registrants Engaged in Mining Operations in Regulation S-K 1300. RESPEC is independent of Paramount and has no affiliations with Paramount except that of an independent
consultant/client relationship.
12.1.1
Estimation Procedure
The Mineral Reserve is composed of material which was classified as an open pit mineral resource. There was a negligible quantity of underground resources
reported outside of resource open pit shell, but these are not part of mineral reserve.
An underground mining scenario is assumed using mechanized
cut-and-fill methods, which, following ramp-up, will produce 1,200–1,400 ton/d, four days a week. This mining rate will provide sufficient material for the 750 ton/day mill and processing plant to operate at full capacity for seven days a
week. The underground cut-and-fill mining method was selected based on minimizing the environmental impacts. The underground cut-and-fill mining method has a significant smaller footprint compared to open pit mining methods. Underground stoping and
other larger underground mining methods were not selected because the size and geometry of the ore body do not support a higher production rate.
The
Proven and Probable reserves for Grassy Mountain have been estimated by first calculating an economic net smelter return (NSR) cut-off for mining underground stopes, then using the NSR cut-off to design stope shapes centered on Measured and
Indicated Mineral Resource blocks with the mining revenue greater than or equal to the NSR cut-off. The QP used the resource block model described in Section 11, in GEOVIA Surpac and Deswik formats. All Inferred material was considered to be
waste with no value or metal content. Internal and external dilution and mining recoveries (ore loss) were estimated and applied as modifying factors based on the total tonnage of material inside of the final designs. The following sections provide
details on the assumptions and design criteria used for estimating the reported Proven and Probable Mineral Reserves.
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12.2
Mineral Reserve Statement
The reference point for the estimated Mineral Reserves is the crusher. Section 11.8 describes the conversion of Mineral Resources to Mineral Reserves.
The Mineral Reserves estimated for the Grassy Mountain Project are provided in Table 12-1 and have an effective
date of May 15, 2026. An underground mining scenario is assumed in this study using mechanized cut-and-fill methods. The Qualified Person responsible firm for the mineral reserves estimate is RESPEC. The reference point at which the Mineral
Reserves are defined is the point where the ore is delivered to the FS mill crusher.
Table 12-1: Mineral
Reserves Statement
ktons
Grade (oz/ton Au)
Grade (oz/ton Ag)
Gold (k oz)
Silver (k oz)
Proven mineral reserves
299
0.167
0.256
50
76
Probable mineral reserves
1,908
0.186
0.287
355
548
Proven + Probable reserves
2,207
0.184
0.283
405
624
Notes:
•
Mineral reserves have an effective date of May 15, 2026.
•
Mineral Reserves are reported inside stope designs assuming drift-and-fill mining methods, and an economic net
smelter return cutoff of $201 per ore ton processed. The economic cut-off grade estimate uses a gold price of $2,750/oz, mining costs of $141/ton processed, surface re-handle costs of $0.22/ton processed, process costs of $39/ton processed, general
and administrative costs of $20/ton processed, and refining costs of $6/oz Au recovered. Cost inputs mentioned here are rounded except the surface re-handle costs.
•
Metallurgical recovery utilizes the recovery schedule discussed in Section 10.5.
•
Mineralization that was either not classified or was assigned to Inferred Mineral Resources was set to waste.
•
A 1.5% NSR royalty is payable.
•
Rounding may result in apparent discrepancies between tons, grade, and contained metal content.
12.3
Economic Cut-off Grade Calculation
12.3.1
Gold Price
The gold price used for the cut-off grade estimation is $2,750/oz Au. The gold daily closing monthly averages in $/oz Au from the World Gold Council is shown
in Figure 12-1 for the three-year period leading up to February 2026. The 24-month average for the period ending in February 2026 is $3,139/oz Au, the 36-month average is $2,752/oz Au, and the 18-month average
is $3,677/oz Au.
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Figure 12-1: Monthly Average Gold Price, $/oz
Source: World Gold Council, 2026
The economic cut-off grade used for stope design is based on initial economic parameters shown in Table 12-2.
Table 12-2: Cut-off Grade Input Parameters for Gold Metal
Name
Quantity
Unit
UG Mining costs
141.18
$/ton processed
Surface Rehandle
0.22
$/ton processed
Process Costs
39.09
$/ton processed
G&A Costs
20.15
$/ton processed
Total Operating Costs
200.64
$/ton processed
Refining Cost
6.00
$/oz processed
NSR Royalty
1.5%
percent
Gold Metal Recovery
92.8%
percent
Gold Selling Price
2,750
$/oz Au
Calculated Cutoff Grade
0.080
oz Au/ton
Mineral Reserve Cutoff Grade Used
0.080
oz Au/ton
NSR Economic Cutoff
201.00
$/ton processed
Note: G&A = general and administrative.
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The calculated gold cut-off grade is 0.08 oz/ton Au. Variable leach recovery depending on the feed grade was
used to assign NSR value in the block model. The NSR economic stope cutoff was used in the stope optimization to identify the Measured and Indicated blocks available for consideration to be converted to Mineral Reserves. Deswik SO 5.13878 version
was used for stope optimization. Measured and Indicated resource blocks with NSR value less than the economic stope NSR cut-off, as well as all Inferred resource blocks irrespective of grade, were considered as waste and applied to internal
dilution.
12.3.2
Silver Price
The silver price used for the economic NSR cut-off evaluation is $31.00/oz Ag. The 24-month average for the period ending in February 2026 is $39.49/oz Ag,
the 36-month average is $34.19/oz Ag, and the 18-month average is $43.18/oz Ag.
The silver metal at Grassy
Mountain has a minimal impact on the economics of the project. Table 12-3 shows the Total Mineral Reserves multiplied by the respective metal prices for gold and silver. The silver metal contributes to less
than 2% of the total revenue.
Table 12-3: Total Mineral Reserves Multiplied by the Metal Price
Metal
Total Mineral Reserves
(‘000 oz)
Metal Price
($/oz)
% Contribution to Revenue
Gold
405
2,750
98%
Silver
624
31
2%
A calculated silver cut-off grade was not used in the mine design due to its relatively small (<2%) contribution to total
economic value as shown in Table 12-3. The economic NSR cut-off grade of $201/ore ton processed was used for determining the stope designs in mineral reserve designs inclusions. Revenue for silver is included
in the financial model, and therefore silver grade and silver contained metal are reported in the estimated Mineral Reserves.
12.4
Stope Design
The Mineral Reserves were constrained by the design of mineable stope shapes centered on Measured and Indicated blocks with grades greater than the economic
stope cut-off. For stope optimization, the Stope Optimizer SO 5.1 3878 module from Deswik™ software was used. The stope optimization parameters are stated in Table 12-4.
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Table 12-4: Stope Optimization Parameters
Attribute
Quantity
Unit
Height
15
ft
Width
15
ft
Round length
10
ft
Minimum optimization length
20
ft
Maximum optimization length
50,000
ft
Minimum stope pillar
5
ft
Slice interval
2
ft
Evaluation method
Exact Geometric
-
Each stope block was queried against the resource block model to determine the tonnages and grades within the stope shapes.
Stopes with an average measured or indicated gold grade equal to and above the economic NSR cut-off were selected to be included in the mine plan and Mineral Reserves estimate. Some isolated stopes above the cut-off grade threshold were eliminated
from consideration because the development to extract them would cost more than the economic return. Dilution and recovery were not considered during the stope optimization. The dilution and recovery were applied as modifying factors later in the
process.
Development designs were generated concurrently for each stope shape with the purpose of minimizing development in waste. Figure 12-3 shows a typical mine production-level design. These designs were done every 15 vertical feet.
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Figure 12-2: Mine Production Design of Level 3210, Plan View
Source: MDA, 2020 (for representation purposes only, MDA is now part of RESPEC).
12.5
Dilution and Recovery
12.5.1
External Dilution
A modifying factor of 8% was used for calculating external dilution tons. Grade was assigned to the external dilution by expanding the stope limits by one foot
on all sides that are not adjacent to other stopes. The resource block model was queried against the expanded volume and 80% of the queried grade was used to determine the appropriate external dilution grades for silver and gold.
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12.5.2
Internal Dilution
All Inferred resource blocks or partial blocks within the stopes and all unclassified material within the stopes is considered internal dilution. The tons were
accounted for with zero grade.
12.5.3
Mining Recovery
Mining recovery is estimated to be 97% based on an assumed ore loss of 3%. This is considered appropriate for the highly selective mechanized cut-and-fill
mining method selected for the Grassy Mountain deposit and it is based on similar operations in disseminated ore bodies.
12.6
Discussion of Mineral Reserves
The QP is not aware of any mining, metallurgical, infrastructure, permitting or other relevant factors not discussed in this Report that could materially
affect the mineral reserve estimate. The economic viability of Grassy Mountain is disclosed in Section 19. Further conclusions are disclosed in Section 22.
12.7
Classification
All design solids were determined to be either ore or waste as shown in Figure 12-4. All mine design solids above the
cut-off-grade were designated as ore. All mine design solids below the cut-off-grade were designated as waste. The block model classified each block as either measured, indicated, or inferred as follows:
•
All tons within the ore mine design solids and classified as measured in the block model were classified as
Proven.
•
All tons within the ore mine design solids and classified as indicated in the block model were classified as
Probable.
•
All tons within the ore mine design solids and classified as inferred in the block model were classified as Ore
Loss.
These parameters are listed in Table 12-5. Please note that a single mine design solid
could contain multiple blocks with different block model classifications. These were segregated according to Table 12-5. Therefore, the classification was done at the block model resolution and not at the mine
design resolution.
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Figure
12-3: Ore and Waste Designation
Source: RESPEC, 2026
Table 12-5: Reserve Classification Parameters
Class
Mine Design Criteria
Classification from the Block
Model
Proven
Ore material above the Cut-Off-Grade
Measured
Probable
Ore material above the Cut-Off-Grade
Indicated
Ore Loss
Ore material above the Cut-Off-Grade
Inferred
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13
MINING METHODS
13.1
Mining Method Selection
The mechanized underhand cut-and-fill mining method was selected using the methodology proposed by Nicholas (1981). Cemented rock fill (CRF) will be used for
backfill. The mechanized cut-and-fill method is highly flexible and can achieve high recovery rates in deposits with complex geometries, as is the case at the Grassy Mountain deposit. The estimated mine life is nine years.
13.1.1
Underhand Mechanized Cut-and-Fill Mining
The Grassy Mountain mine will be an underground operation accessed via one decline and a system of internal ramps. Stacked set of raise is included in the
design to be used for ventilation and secondary egress as shown in Figure 13-1. A plan view of the proposed mine design is shown in Figure 13-2.
Figure
13-1: Grassy Mountain Mine Cross-section Looking North
Source: RESPEC, 2026
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Figure
13-2: Proposed Grassy Mountain Mine Plan (plan view)
Note: The mine design was based on an average production rate of 1,200 -1,400 tons per day using a four-day-on and
three-day-off schedule, with two 12-hour shifts per day, to provide 24-hour coverage during the four operating days at full operation. This will provide sufficient material to feed 750 tons/d to the mill on a seven day per week basis. Source:
RESPEC, 2026
The nominal development size will be 15 ft wide by 15 ft high as shown in Figure 13-3. The nominal
Topcut-A production size is to be 15 ft wide by 15 ft high as shown in Figure 13-3. The Topcut-A will be used when the material above is native rock. The nominal Undercut-B production size is to be 20 ft
wide by 15 ft high as shown in Figure 13-3. The Undercut-B will be used when the material above is cemented backfill from a Topcut-A production drift as shown in Figure
13-4. The nominal Undercut-C production size is to be 30 ft wide by 15 ft high as shown in Figure 13-3. The Undercut-C will be used when the material above is cemented
backfill from an Undercut-B as shown in Figure 13-4. This heading layout will tolerate weak ground conditions while still maximizing production in a cut-and-fill mine.
The sizes will allow the miners and associated diesel mining equipment access and flexibility to maximize production from the mine as well as minimize waste
haulage from the development headings.
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Figure
13-3: Drift Profiles
Source: MDA, 2020 and used unmodified by RESPEC in 2026
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Figure
13-4: Production Drift Layout (Section Looking East)
Note: The mining cycle involves drilling, blasting, and mucking for the development and production access. The final part
of the mining cycle is to backfill the stopes. Source: MDA, 2020 and used unmodified by RESPEC, 2026
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13.1.2
Mining Method Sequence
The mining sequence contains a mining level sequence and an underhand production stope sequence. The level sequence for a typical level can be seen in Figure 13-5. The level access is mined first. The mains are mined second. Typically, two mains are mined at the same time providing multiple mining locations on a level. After the mains are mined, then the production
drifts can begin mining. The production drifts are sequenced with primaries and secondaries. The primaries are mined and backfilled first allowing for a backfill minimum cure time of 14-days between the primaries and secondaries. This continues as
shown in Figure 13-5 until the entire level is complete. After the entire level is complete the level access is backfilled and a 28-day delay for the cure time is applied. After the cure time is complete the
level below can start.
Figure
13-5: Detailed level Sequence for a Typical Level
Note: The underhand mining sequence is grouped into lifts as shown in Figure 13-6. Source: MDA, 2020 and used unmodified by
RESPEC, 2026
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Figure
13-6: Mining Lifts
Source: MDA, 2020 and used unmodified by RESPEC, 2026.
One level in each lift can be mining at any given time during the life of mine. The underhand sequence starts at the top and works down in elevation.
Constraints are applied to ensure that the bottom level of a lift does not conflict the top level of the lift below.
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13.2
Geotechnical Analysis
13.2.1
Overview
The Grassy Mountain deposit is situated is a horst block which has been raised 50–200 ft in a region of complex block faulting and rotation. Faulting is
dominated by post-mineral N30ºW to N10ºE striking normal faults developed during Basin and Range extension. On the northeast side of the deposit, these faults progressively down-drop mineralization beneath post-mineral cover. These offsets
are suggested by interpreted offsets in drill holes of a prominent white sinter bed, as well as intersections with a fault gouge. The N70ºE striking the Grassy Mountain fault shows a minor vertical offset of 10–40 ft.
The North and Grassy faults are significant fault structures that pose a risk to the stability of an open stoping method; hence, these areas are considered
suitable only for a limited man-entry mining method such as mechanized cut-and-fill, where conditions can be well controlled.
Degradation of the Grassy
Mountain Formation results in difficult mining conditions that can be mitigated through additional ground support, which would involve a higher mining cost with slower advance rates in those areas.
Stress measurements are not currently available. In the absence of this information, a stress regime based on the World Stress Map was used to obtain a range
of estimates. Based on the shallow depth, ground stress is relatively low, and rock damage due to higher mining-induced stress concentrations is only anticipated in high-extraction or sequence closure areas and weaker rock mass areas. However, a
reduction in the mining stresses around excavations is likely to adversely affect the stability of large open-span areas. Tensile failure and gravity-induced unraveling are foreseen as the main failure mechanisms.
The Grassy Mountain deposit is in a structurally complex, clay-altered, epithermal environment. Rock mass conditions in the infrastructure and production
areas vary from Poor to Fair quality (RMR 20–45; RMR mean 40–45) with the poorest conditions within major structures that run longitudinally through and bound the deposit. Outside of these fault areas, rock mass conditions are generally
Fair. However, localized zones of Poor ground potentially associated with secondary structures or locally elevated alteration intensity are present throughout the planned mining area.
Excavation stability assessments were completed using industry-accepted empirical relationships, with reference to analogue mines where possible. The rock
mass conditions (Poor to Fair) are considered suitable only for a selective underground mining methods and limited sizes.
Ground support design considers
industry-standard empirical guidelines and GMS’s experience in variable ground conditions. Compromises have been made in the extraction sequence due to the need to balance grade and production profiles, extraction of wide orebody areas, and
other geotechnical constraints. Ultimately, some aspects of the sequence may not be geotechnically optimal, and additional analysis or design may be required.
The North and Grassy faults are significant fault structures that pose a risk to the stability of an open stoping method; these areas are therefore considered
suitable only for a limited man-entry mining method such mechanized cut and fill, where conditions can be well controlled. Two secondary structural systems have been identified, which cut and cause slight dislocations in the veins and mineralized
bodies: one corresponding to normal-displacement structures with a north–northeast–south–southwest strike and the other with a northwest–southeast strike. Not all fault structures could be modelled, and the influence of
several secondary- and tertiary-level structures in the deposit are not well understood. Several fault structures will need to be further defined and interpreted during the decline ramp excavation program.
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13.2.1.1
Degradation Zones
Time-dependent drill core degradation has previously been identified at Grassy Mountain. In general, degraded zones are contained within siliceous sinter
bodies, conglomerates, and interbedded tuff beds within the Grassy Mountain Formation. Degradation is strongest in intervals that are observed or interpreted as having contained silicic and potassic alteration. Contacts of the Grassy Mountain
Formation were used to extrapolate degradation zones beyond areas of graphically-logged intervals in order to construct moderate- and high-confidence degradation shells. Across the deposit, the North and Grassy faults produce significant degradation
above and below the conglomerates and tuff strata, and the faults to the west appear to displace or bound the degradation zone.
Degradation of Grassy
Mountain Formation lithologic units results in difficult mining conditions that can be mitigated through additional ground support. This would result in a higher mining cost with slower advance rates in those areas.
13.2.1.2
Structural Fabric
The geotechnical holes drilled in the 2016–2017 campaign were drilled with “triple tube” techniques to increase core integrity and
preservation for best geotechnical logging and measurements. Observations of the core suggest that there is little systematic structure, except for the very steep features often sub-parallel to the core axis that are likely oriented similarly to the
interpreted northwest–southeast-striking faults associated with mineralization. The remaining structure is typically very small-scale, irregular, and generally related to micro-defects within the rock mass.
13.2.1.3
In-situ Stress
Stress measurements are not currently available. In the absence of this information, a stress regime based on the World Stress Map was used to obtain a range
of estimates. Uncertainty in the stress magnitude will need to be further assessed and interpreted during the decline ramp excavation program.
Based on
the shallow depth, ground stress is relatively low, and rock damage due to higher mining-induced stress concentrations is only anticipated in high-extraction or sequence closure areas and weaker rock mass areas. However, a reduction in the mining
stresses around excavations is likely to adversely affect the stability of large, open-span areas. Tensile failure and gravity-induced unraveling are foreseen as the main failure mechanisms. The pre-mining stress field should be further evaluated.
13.2.2
Geotechnical Characterization
A geotechnical investigation was carried out by Golder in 2017 and Ausenco in 2018 to characterize rock mass conditions in support of an underground design for
the 2018 PFS. A combined total of 27 core holes were drilled through the deposit and geotechnically logged and sampled for laboratory strength testing as part of the 2016–2017 program. Point load testing was also conducted on cores retrieved
from the geotechnical drill holes. After the 2016–2017 core holes program, GMS geotechnically logged two core holes from the 2019 program.
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The geotechnical database from the 2016–2017 program was checked against the respective core
photographs for internal data consistency and the data are considered to be suitable for a feasibility-level study.
Overall, the following information
was used to base geotechnical assessments:
•
2016–2017 core holes database with RQD and core recovery data
•
Core photographs for 2016–2017 core holes
•
Detailed geotechnical logging for 25 holes by Paramount under Golder training and review (2016–2017)
•
Detailed geotechnical logging for two holes by Golder (2016–2017)
•
Detailed geotechnical logging for two holes by Paramount (2019)
•
Field point load testing of cores from six holes (total of 300 tests) during the 2016–2017 program and from
two holes (total of 166 tests) during the 2019 program
•
Laboratory strength testing for two programs (2016–2017 and 2019) including uniaxial compressive strength
(UCS), Brazilian tensile strength, and elastic properties.
13.2.3
Golder Geotechnical Appraisal
A geotechnical appraisal of the proposed underground mine area was carried out by Golder during 2016–2017 (Golder Associates Inc, 2018). Geotechnical
data were available from three different drilling programs that were completed prior to the 2016–2017 drill program. Calico, Newmont, and Atlas carried out RQD measurements. Additional geotechnical data from Newmont and Calico drilling were
reviewed but not used directly in Golder’s 2016–2017 evaluation, due to uncertain reliability and consistency in the data.
Two holes were
logged in detail for geotechnical characterization by Golder personnel at the drill rig. The other 2016–2017 holes were logged by Paramount personnel according to Golder’s instructions and procedures (25 core holes).
Golder used the geotechnical log data to characterize the orebody and surrounding rock mass, based on an RMR calculation from the logged data. Figure 13-7 presents the RMR76 histogram for all core that was geotechnically logged from the 2016–2017 drill program. The pre-2016–2017 Calico, Newmont, and Atlas historical data were not evaluated with the
2016–2017 program. Golder did not consider the pre- 2016–2017 data usable with the 2016–2017 RMR log data.
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Figure
13-7: Golder Rock Mass Rating (all 2016–2017 core)
Source: Golder, 2018
Golder’s drill core review in 2016–2017 indicated the presence of a significant number of zones of broken rock fragments within what Golder termed
“a matrix of soil” and referred to as “Soil Matrix Breccia”. These zones are more correctly referred to as “Clay Matrix Breccia”. The Clay Matrix Breccia, an important contributor to Type III rock quality (Table 13-1) is readily observed in cores in split tubes immediately after drilling, but it is also clearly identifiable after the core has been boxed and somewhat disturbed.
Table
13-1: Rock Quality Categories
Rock Quality Category
Description
Approximate Expected Percent of
Excavations (a) (%)
Type I
Moderately fractured rock
20
Type II
Poor quality, highly fractured rock
40
Type III
Clay matrix breccia and other very poor-quality rock (clay, broken rock and rubble in core boxes)
40 (15% clay matrix breccia, 25% other poor-quality rock)
Note: Based on percent encountered within 2016–2017 drill holes.
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The geological and geotechnical data did not identify any trends or patterns that would allow the delineation
of rock quality domains for mine design, with the exception of Very Poor-quality rock encountered in and around the interpreted sub-vertical structures. However, Very Poor-quality rock was not limited to the vicinity of the structures; it was also
frequently observed between structures. This degree of variability required a selective mining method that can quickly respond to changing ground conditions.
Golder (2018) concluded that, in the absence of spatial patterns in rock quality, three categories of rock quality should be applied for PFS-level design
and cost estimating purposes (refer to Table 13-1).
13.2.4
Ausenco Geotechnical Work
In 2017, Ausenco’s geotechnical group conducted a review of all the available geotechnical information provided by Paramount, including core logs and
core photographs. The main objectives were to select a mining method and develop recommendations for support in underground openings.
Ausenco’s
geotechnical group reviewed all core photographs from the 2016–2017 core drilling program and estimated additional geotechnical parameters that were incorporated into the geotechnical review.
In order to characterize the rock mass of the deposit, a statistical analysis was performed on the geotechnical data derived from the core logging by
Paramount and Golder. The RMR76 results analyses are shown in Figure 13-8.
Figure
13-8: RMR 76 Histogram from 27 Drill Holes
Source: MDA, 2017
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Per the analysis conducted by Ausenco, the majority of the ground conditions of the Grassy Mountain deposit
are classified as being of Fair to Poor rock quality, and the RMR is typically less than 49.
Based on RMR76 statistics and Ausenco’s interpretation
and correlation with the geological database, it can be concluded that Golder’s previous analysis (unknown at that time), with the same data, had very similar results.
The Grassy Mountain deposit was assigned by Ausenco to three rock classes by geotechnical quality:
•
Class 1: Rocks of Poor geotechnical quality according to RMR76; approximately 40% of the deposit.
•
Class 2: Rocks of Fair geotechnical quality according to RMR76; approximately 50% of the deposit.
•
Class 3: Rocks of Good geotechnical quality according to RMR76; approximately 10% of the deposit.
Table 13-2 shows the cumulative frequency values based on the RMR76 histogram from 27 drill
holes (Figure 13-9) with the rock classes assigned by Ausenco.
Table
13-2: Rock Quality Categories
Rock Quality
(RMR)
Frequency (%)
Rock Class
Deposit (%)
0–20
Very Poor
1.8
—
—
20–40
Poor
38.3
Class 1
40
40–60
Fair
49.4
Class 2
50
60–80
Good
9.3
Class 3
10
80–100
Very Good
1.2
—
—
The Very Poor and Very Good rock qualities, according to the RMR classification, are not representative of the deposit due to
the low frequencies measured, so they were omitted from the three rock classes assigned. However, they do exist and should be considered when mining, in particular the Very Poor quality, which may require additional support.
Examples of the three 2017 RMR classes are shown in Figure 13-9.
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Figure
13-9: Examples of Three Geotechnical Rock Classes
Source: MDA, 2017
13.2.5
Feasibility Study Geotechnical Analysis
The basic geotechnical parameters recorded in the field during the 2016–2017 and 2019 drill holes program were combined to form an RMR system
(Bieniawski, 1976). These data were used to create an RMR profile with depth for each of the geotechnical holes drilled. The RMR76 system consists of a rating scale accounting for intact rock strength (IRS), fracture frequency per meter (ff/m),
joint conditions, and groundwater. RMR values consider a maximum possible value of 100 for each run. Dry conditions were assumed for RMR calculations, as groundwater pressures are accounted for during the stability analysis using effective stress
type analyses. A summary of RMR values per area of the deposit is presented in Table 13-3.
Table
13-3: Summary of RMR (Bieniawski, 1976) Values by Area
Area Data
RMR (B76)
Data (no)
Mean
Standard Deviation
Decline ramp/mine infrastructure
38
18
226
Stopes (drifts)
40
18
1,123
Crown pillar
41
19
242
Centre of deposit (Section)
38
20
149
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Data from the geotechnical core logging and the statistical analysis indicate that the geotechnical units
have similar geotechnical conditions. The data indicate that the deposit presents no substantial differences in geotechnical qualities among the stope areas and mine infrastructure location, including the intersections with faults or veins, which
present Poor to Very Poor qualities. In general, the deposit presents a high variability in geotechnical qualities over short distances, but with a similar behavior for the whole area of the proposed mine. This assumption can be refuted or confirmed
by the rock quality observed in the core trays shown in Figure 13-10.
Figure
13-10: GM19-37 Core Trays (89.5 to 105.5 ft.) – High
Variability in Geotechnical Conditions
Source: GMS, 2020
13.2.5.1
Intact Rock Strength
Physical testing of suitable rock core specimens allows determining the mechanical properties of intact rock required for mine design using rock mass
classification or numerical analysis methods. The IRS is commonly measured in uniaxial compression, point load, indirect tensile, and triaxial compression tests (Brady and Brown, 2004). Usually, a limited (but representative) number of cylindrical
specimens of each rock type should be tested for UCS in a suitable laboratory equipped with a stiff testing machine. A larger number of point load tests can be carried out during the core logging process for orebody delineation. A comprehensive set
of suggested testing methods has been published by the International Society for Rock Mechanics (ISRM) (Brown, 1981; Ulusay and Hudson, 2007).
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Golder selected core samples for laboratory testing from six of the 2016–2017 geotechnical core holes.
Samples from one of the 2019 geotechnical core holes were also selected by GMS for laboratory testing. The samples were submitted to Golder’s laboratory in Burnaby, British Columbia.
Point load tests (PLTs) were conducted by Paramount geologists in the core shed after geotechnical logging, in keeping with the ASTM Standard D 5731-07:
Determination of the Point Load Strength Index of Rocks, and Application to Rock Strength Classifications. PLTs were performed at approximately 10-ft intervals down hole.
Table 13-4 provides a summary of the IRS parameters by geotechnical units considering the median depths where the
deposit is located.
Table 13-4: Intact Rock Strength for Geotechnical Units Calculated from PLTs
Geotechnical Unit
H (ft)
Intact Rock
mi*
CS (Mpa)
Ei** (Gpa)
γ(T/m3)
GTU-2 (sandstone/arkose (D=0.5))
492
12.7
116.70
60.2
2.47
984
GTU-2 (sandstone/arkose (D=0))
492
12.7
116.70
60.2
2.47
984
GTU-3 (siltstone (D=0.5))
492
7.0
101.92
46.9
2.49
984
GTU-3 (siltstone (D=0))
492
7.0
101.92
46.9
2.49
984
GTU-4 (tuff (D=0.5))
492
13.0
158.08
57.1
2.44
984
GTU-4 (tuff (D=0))
492
13.0
158.08
57.1
2.44
984
GTU-5 (sinter (D=0.5))
492
13.1
120.92
69.7
2.45
984
GTU-5 (sinter (D=0))
492
13.1
120.92
69.7
2.45
984
GTU- 6 (conglomerate (D=0.5))
492
21.0
90.41
69.45
2.47
984
GTU-6 (Conglomerate (D=0))
492
21.0
90.41
69.45
2.47
984
*
mi: material constant for the intact rock
**
Ei (Gpa): intact rock modulus
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13.2.6
Geotechnical Model
The geotechnical model for this Report is the final result of the combination of the geological model, the rock mass fabric descriptions, the rock mass
strengths, and the hydrogeological model. This geotechnical model describes the rock mass units from an engineering perspective through geotechnical domains. Geotechnical domains are zones showing similar geotechnical properties, based on rock type,
rock mass strength, and geological characteristics. In particular, in the Grassy Mountain deposit the geotechnical domains are controlled by the lithology present and its alteration grade as geotechnical units. Seven geotechnical units were
identified:
•
Cover soil
•
Sandstone/arkose
•
Siltstone-mudstone
•
Tuff
•
Sinter
•
Conglomerate
•
Clay matrix breccia.
Overall, the first layer corresponds to cover soil with a thickness of less than 9.8 ft. Below that is a jointed rock mass mainly composed of a series of
layers of sandstone/arkose, siltstone, tuff, sinter, and conglomerate. The layers do not follow any sequence between geotechnical units, and clay matrix breccia can be located between every geotechnical unit combination around the deposit and,
especially, close to drifts. In general, all the geotechnical units are highly jointed and have strengths between 95–135 Mt/a.
A statistical
analysis was performed to provide the frequency of geotechnical qualities per each geotechnical unit. The RQD, RMR76, and GSI 2013 values are summarized in Table 13-5.
The rock mass quality of the deposit’s geotechnical units does not improve with depth. Around faults/veins, the geotechnical units are in Very
Poor-quality rock with an RMR of less than 30. However, Very Poor-quality rock is not limited to the vicinity of the faults/veins; it is also frequently observed between faults/veins. There is no clear evidence that these zones correspond to the
veins, but the statistical analysis of RMR76 and PLT values indicates that the geotechnical units have a separate population with low values in the approximate location of the faults/veins.
Based on the RMR76 statistics and the current interpretation and correlation with the previous geotechnical analysis conducted, it can be concluded that the
defined geotechnical units are classified as being of Fair to Poor rock quality, represented by an RMR76 of typically less than 48 and a GSI2013 of less than 45.
Core logging data suggest that the generalized Hoek-Brown failure criteria is a suitable method for calculating the rock mass strength parameters for all of
the units, because the majority of the rock mass is considered jointed hard rock material. When RMR values are less than 23, the Hoek-Brown failure criteria are no longer applicable because strength parameters are not strongly dependent on
confinement.
Table 13-5 provides a summary of rock mass strength parameters by geotechnical units considering the
median depths where the deposit is located.
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Table 13-5: Summary of RQD, RMR76, and GSI 2013 Values by
Geotechnical Unit
Geotechnical
Unit
(GTU)
Description
RQD
RMR76
GSI2013
Weighted
Mean
Weighted
Standard
Deviation
Weighted
Mean
Weighted
Standard
Deviation
Weighted
Mean
Weighted
Standard
Deviation
1
Cover soil
NA
NA
NA
NA
NA
NA
2
Sandstone, arkose
50.3
26.8
48.0
12.7
45.1
21.0
3
Siltstone, mudstone, breccia
41.2
26.8
42.6
12.4
37.4
20.4
4
Tuff
41.7
27.6
41.7
10.2
38.8
22.3
5
Sinter
35.0
30.4
44.7
11.1
37.1
22.0
6
Conglomerate
NA
NA
NA
NA
NA
NA
7
Clay matrix breccia
23.4
28.1
30.1
13.6
18.9
19.3
Note: NA = not applicable.
Table 13-6: Strength Parameters for Geotechnical Units
Geotechnical Unit
H (ft)
Rock Mass
GSI
mb
s
a
s TM
(Mpa)
E H-D2005
(Gpa)
v
C
(kPa)
∅ (°)
GTU-2 (sandstone/arkose (D=0.5))
492
45
0.929
0.0007
0.508
-0.082
6.37
0.26
798
48.0
984
1184
42.8
GTU-2 (sandstone/arkose (D=0))
492
45
1.788
0.0022
0.508
-0.145
13.46
0.26
1075
52.9
984
1542
48.0
GTU-3 (siltstone (D=0.5))
492
37
0.349
0.0002
0.514
-0.066
3.01
0.27
525
38.3
984
777
33.1
GTU-3 (siltstone (D=0))
492
37
0.738
0.0009
0.514
-0.126
6.10
0.27
743
44.5
984
1065
39.3
GTU-4 (tuff (D=0.5))
492
37
0.647
0.0002
0.514
-0.055
3.66
0.27
717
47.2
984
1088
42.0
GTU-4 (tuff (D=0))
492
37
1.370
0.0009
0.514
-0.105
7.42
0.27
987
53.0
984
1453
48.1
GTU-5 (sinter (D=0.5))
492
37
0.652
0.0002
0.514
-0.042
4.47
0.27
646
45.2
984
986
39.9
GTU-5 (sinter (D=0))
492
37
1.381
0.0009
0.514
-0.080
9.06
0.27
875
51.2
984
1308
46.2
GTU- 6 (conglomerate (D=0.5))
492
40
1.206
0.0003
0.511
-0.025
5.34
0.27
706
48.2
984
1099
43.0
GTU-6 (conglomerate (D=0))
492
40
2.464
0.0013
0.511
-0.047
11.09
0.27
916
53.7
984
1410
48.8
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13.2.7
Summary of Geotechnical Analysis and Evaluation for Underground Mining
The QP believes the available geotechnical data are adequate for designing the mine openings associated with the estimation of the Grassy Mountain Mineral
Reserves at the current stage. Risks associated with the current level of geotechnical analysis are discussed in Section 22.18, and recommendations for additional work are presented in Section 23.4.
While the rock quality is variable and the deposit is mineable based on the chosen mining method, care must be taken during the execution of the mine plan.
The selected mining method and underground support recommendations are specified in Sections 13.4 and 13.5 of this Report.
As part of the 2026
Feasibility Study Update, GMS reviewed the updated mine planning information, underground mine layouts, mine sequencing information and production schedule provided by RESPEC. Based on the review completed, no material changes were identified that
would require modification of the geotechnical characterization, geotechnical domains, rock mass classifications or geotechnical design assumptions presented in this chapter.
13.3
Hydrogeological modelling
A hydrogeological assessment of the mine site was completed by Lorax Environmental Services (March 2020) in a report titled “Grassy Mountain Gold and
Silver Project Mine Dewatering Hydrogeologic Assessment”, which included baseline reports for groundwater and dewatering analysis. This report is used as the basis for underground dewatering requirements in Section 15.7.3.
13.4
Excavation Design
13.4.1
Mining Method Selection
The selection method assessment was carried out during the 2018 PFS according to the methodology proposed by Nicholas (1981), where the deposit geometry and
the geotechnical parameters are assessed as main parameters. In particular, the methodology provides a ranking of mining methods in order to incorporate economic parameters for the final selection.
The design factors that influence the choice of mining method include:
•
Orebody geometry (e.g. vein shape, thickness, dip, etc.) and grade distribution within the deposit
•
Rock mechanics characteristic of the veins, hanging wall, and footwall rock mass
•
Mining costs and capitalization requirements
•
Mining rate
•
Type and availability of mining labor
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•
Environmental concerns
•
Other site-specific considerations.
The assessment suggested the mechanized cut-and-fill mining method would be most appropriate for the Grassy Mountain Project.
The mechanized cut-and-fill method is highly flexible and can achieve high recovery rates in deposits with complex and flat-dipping geometries, as is the case
at the Grassy Mountain deposit.
As part of the 2026 Feasibility Study Update, the revised underground mine plan, mine layouts, mine sequencing
information and production schedule prepared by RESPEC were reviewed by GMS from a geotechnical perspective. Based on the information provided, no material changes were identified that would affect the suitability of the selected mining method or
require revision of the geotechnical basis of design supporting the mining method selection.
13.4.2
Drift Sizes and Stability Assessments
Preliminary dimensioning was carried out during the 2018 PFS using the empirical design proposed by Mathews (1980). The analysis provided the hydraulic radius
for the maximum drift dimension under 60% stability conditions.
The stability graph is a function of the stability number, which represents the ability
of the rock mass to remain stable under certain operating stress conditions as a function of the hydraulic radius, which represents the geometry of the stope surface. The main concept associated with the stability graph is that the surface size of
an excavation can be related to the strength properties of the rock mass, so as to have an idea of the associated stability or instability.
The rock mass
conditions in the Poor to Fair rock mass range are considered suitable only for a man-entry method where conditions can be well controlled, such as mechanized cut-and-fill.
The current analysis aims to validate the drifts dimensioning defined for the 2020 FS. For that, the Q’ value was obtained from the geotechnical
characterization using RMR76, particularly considering GTU-2 as the most frequent geotechnical unit in the deposit.
Iso-probability contours, which
relate the stability number and the hydraulic radius, were used to calculate drift dimensions stability for stable cases (Figure 13-11; Table 13-7).
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Figure
13-11: Iso-Probability Contours for Stable Cases
Source: GMS, 2020; after Mawdesley, 2001
Table 13-7: Iso-Probability Contours for Stable Cases Results
Drift
B–E Walls (Roof) Stable
(%)
H–F Walls (Wall) Stable
(%)
Topcut A
>95
>95
Undercut B
≈90
>95
Undercut C
≈80
>95
The results show that, for the current dimensions, the hanging wall and foot wall would present a probability of stability of
more than 95%, and the back and end walls would present a probability of stability of more than 95% for Topcut A, of around 90% for Undercut B, and of around 80% for Undercut C.
The iso-probability contours for failure cases are shown in Figure 13-12 and Table
13-8.
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Figure
13-12: Iso-probability contours for failure cases (Mawdesley, 2001)
Source: GMS, 2020
Table 13-8: Iso-Probability Contours for Failure Cases Results
Drift
B–E Walls (Roof)
Failure
(%)
H–F Walls (Wall)
Failure
(%)
Topcut A
<10
<10
Undercut B
<10
<10
Undercut C
~20
<10
The results show that, for the current dimensions, the Hanging and Foot Walls would present a probability of failure of less
than 10%, and the Back and End Walls would present a probability of failure of less than 10% for Topcut A and Undercut B, and of around 20% for Undercut C.
As part of the 2026 Feasibility Study Update, GMS reviewed the updated underground mine plan, mine layouts, mine sequencing information and production
schedule. Based on the review completed, no material changes were identified that would require revision of the excavation design criteria, excavation geometries or geotechnical design assumptions supporting the excavation designs presented herein.
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13.5
Numerical Modelling
Numerical assessments using RS2 and FLAC3D have been completed to evaluate the extraction sequence, decline ramp and drift stability, stress migration,
potential damage to infrastructure, and subsidence, even though the mine will be at relatively shallow depths (500–900 ft below ground surface).
To
complement empirical methods and validate the support design, a detailed two-dimensional numerical analysis was carried out using the RS2 program (Rocscience, 2020). The purpose of these numerical models is to assess the effect of the in-situ stress
on the excavation and the response of the reinforcement and support elements.
The results for the decline ramp (Figure 13-13) indicate the following:
•
In general, the maximum principal stress (S1) contours show high compressive stresses at the toe of the walls and
above the roof at 1.6 ft, and a relaxation of stresses in the walls and the bottom.
•
The minimum principal stress (S3) contours show a complete relaxation of stresses around the walls, the bottom,
and the roof. Therefore, no tensile stress problems are revealed.
•
The strength factor (SF) is higher than 1.0 around the walls and roof, with only the bottom presenting values
close to 1.0. However, there is a concentration of shear and tension yielding points. Yielding points reach up to 1.3 ft over the roof and 2.6 ft around the walls.
•
Displacement (D) contours show a maximum >1 cm in the walls and bottom.
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Figure
13-13: Modeling Results for Decline Ramp; a) Major Principal Stress,
S1; b) Minor Principal Stress, S3; c) Strength Factor, SF; d) Displacements
Source: GMS, 2020
The
results for Topcut A (Figure 13-4) indicate the following:
•
In general, the maximum principal stress (S1) contours show high compressive stresses on the shoulders and a
relaxation of stresses in the walls, the bottom, and the roof;
•
The minimum principal stress (S3) contours show a zone with tensile stress on the shoulders and relaxation of
stresses around the walls, the bottom, and the roof. Therefore, no major tensile stress problems are revealed;
•
The SF is higher than 1.0 around the walls and roof, with only the bottom presenting values close to 1.0.
However, there is a concentration of shear and tension yielding points. Yielding points reach up to 1.2 ft over the roof and 1.0 ft around the walls;
•
Displacement (D) contours shown a maximum >1 cm in the walls, the bottom, and the roof.
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Figure
13-14: Modeling Results for Topcut A; a) Major Principal Stress, S1;
b) Minor Principal Stress, S3; c) Strength Factor, SF; d) Displacements
Source: GMS, 2020
The
results for Undercut B (Figure 13-15) indicate the following:
•
In general, the maximum principal stress (S1) contours show high compressive stresses on the shoulders and a
relaxation of stresses in the walls, the bottom, and the roof.
•
The minimum principal stress (S3) contours show a zone with tensile stress on the shoulders and a relaxation of
stresses around the walls, the bottom, and the roof. Therefore, no major tensile stress problems are revealed.
•
The SF is higher than 1.0 around the walls and roof, with only the bottom presenting values close to 1.0.
However, there is a concentration of shear and tension yielding points. Yielding points reach up to 2.0 ft over the roof and 1.2 ft around the walls.
•
Displacement (D) contours shown a maximum > 1 cm in the walls, the bottom, and the roof.
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Figure
13-15: Modeling Results for Undercut B; a) Major Principal Stress,
S1; b) Minor Principal Stress, S3; c) Strength Factor, SF; d) Displacements
Source: GMS, 2020
The
results for Undercut C (Figure 13-6) indicate the following:
•
In general, the maximum principal stress (S1) contours show high compressive stresses on the shoulders and a
relaxation of stresses in the walls, the bottom, and the roof.
•
The minimum principal stress (S3) contours show a zone with tensile stress on the shoulders and relaxation of
stresses around the walls, the bottom, and the roof. Therefore, no major tensile stress problems are revealed.
•
The SF is higher than 1.0 around the walls and roof, with only the bottom presenting values close to 1.0.
However, there is a concentration of shear and tension yielding points. Yielding points reach up to 2.5 ft over the roof and the bottom, and 1.2 ft around the walls.
•
Displacement (D) contours shown a maximum >1 cm in walls, the bottom, and the roof.
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Figure
13-16: Modeling Results for Undercut C; a) Major Principal Stress,
S1; b) Minor Principal Stress, S3; c) Strength Factor, SF; d) Displacements
Source: GMS, 2020
To
optimize the mine design and mine plan, a three-dimensional model considering finite difference (Figure 13-17) was developed using the Flac 3D v.5.01 Program (Itasca, 2015).
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Figure
13-17: Three-Dimensional Model of Finite Difference
Source: GMS, 2020
The model
was developed to perform the parametric analysis of the mine design and mine plan according to the excavation and backfill process for the LOM. In addition, potential caving on surface was assessed using the model results.
Excavation of adjacent drifts could not only result in loss of backfill strength, it could also generate high levels of stress, resulting in rock mass damage
and possible poor excavation performance related to low-strength rock mass. Maintaining at least three horizontal drifts of distance between excavations would help to cut off the horizontal stresses acting across the deposit.
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Rock mass damage will be particularly prevalent in the excavation intervals located within the fault zones
adjacent to advancing drifts. These cross-cut intervals will need to be well supported during initial development and may need rehabilitation in the more critical closure areas.
In general, the reduction in the mining stresses around excavations is more likely to adversely affect the stability of the areas immediately above the cut
and fill mining areas. The failure modes in these areas are likely to be tensile failure and gravity-induced unravelling. Preventing these types of failure will require high levels of support.
FLAC3D code was specifically used to review the potential for movement along faults and the potential for surface subsidence. The excavation and backfilling
sequences generate accumulated displacements of around 11–15 inches over the levels facing the north orientation of the mine. These displacements are considered the maximums identified in the global excavation of the model and represent a
contour area of at least five levels higher. In spite of the maximum displacements identified, the displacements are expected to be overestimated because the numerical analysis was modelled considering year-by-year excavation that strongly affects
the rock mass displacement values. Therefore, the monthly excavation may present lower displacement values.
Subsidence caused by extraction could cause
dilation or fracturing above the deposit and an increase in hydraulic conductivities and water inflows to the mine. Some level of dilation of fault and joint systems within the Grassy Mountain Formation can be expected as a result of mining. Under
the current extraction sequence, this is expected to occur during the initial stages of mining. The ground surface presents contour displacements of around 0.4–9.8 inches from year 1 to year 5 (increasing in lineal proportion), but from year 5
to year 8, the contour displacements are projected to stabilize at around 9.8 inches.
GMS noted the following:
•
Based on the prevailing ground conditions in the Poor rock conditions, cut and fill headings are recommended (30
ft wide x 15 ft high maximum dimension stope allowed). These dimensions will ensure that good quality backfill practices can be maintained through tight filling to manage open spans, side wall stability, and ultimately the stability of the mining
area. Smaller spans will require less ground support to ensure that cycle times and productivity are maintained.
•
The stand-off distance for long-term critical excavations, including decline ramp and ventilation shafts, is
recommended to be 200 ft from the drifts. For permanent foot wall drives, a 100 ft stand-off is recommended.
To ensure stability during
the mine sequence, lateral rock pillars should be wider than three drifts wide. These rock pillars known as Rib Pillar, also maintain control of mining and reduce possible high stress concentrations around the drifts in mining and backfilling
process. This is primarily dictated by the potential range of Fair–Poor rock mass conditions (especially near faulted areas).
GMS considers that
the best approach to manage risk in this environment is to plan a more conservative approach to the drift design and extraction sequence. The high-grade nature of the deposit means that ore recovery is critical to maintaining the grade profile, and
the stability and final recovery of drifts in the variable rock mass could be very challenging.
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13.5.1
Ground Support
The ground support design considers industry-standard empirical guidelines and GMS’s experience in variable ground conditions. The ground support
philosophy for underground excavations is sprayed concrete lining (fiber-reinforced shotcrete) with bolts installed through the concrete. Sprayed concrete was selected for overall simplicity and speed of application, longevity of surface support,
and sealing of rock blocks that may potentially fall from the roof and walls.
Enhanced ground support for poor ground areas includes the installation of
initial (pre-support), thicker shotcrete, reduced bolting spacing, and Swellex-type bolting. Cable bolts are considered for over-stressed accesses, cross-cuts in cut and fill areas, and drifts under rock mass environments (particularly the roof).
Table 13-9 and Table 13-10 provide the support designs under rock mass and backfill environments, respectively.
Table
13-9: Reinforcement and Support Design for Mine Development Under
Rock Mass Environment
Excavation
Section
(ft)
Bolts
Length(ft)
Bolts
Pattern (ft)
Cable
Bolts (ft)
Cable
Pattern (ft)
Fiber-Reinforced
Shotcrete (Inches)
Mesh (1)
Decline
15
7.9
4.3 x 4.3
No
8.2 x 8.2
4
Yes
Access (top)
15
7.9
19.7
Access (under)
15
7.3
No
No
Topcut A
15
7.9
19.7
Undercut B
20
8.4(2)
19.7
Undercut C
30
9.3(2)
19.7
Note: (1) Galvanized welded wire mesh. (2) Final length should be defined in-situ by geotechnical engineer on site
according to Boltec equipment to use (at this stage was necessary to use 7.9 ft. length as maximum bolt length).
Table
13-10: Reinforcement and Support Design for Mine Development Under
Backfill Environment
Excavation
Section
(ft)
Bolts Length
(ft)
Bolts Pattern
(ft)
Cable Bolts
(ft)
Cable Pattern
(ft)
Fiber-Reinforced
Shotcrete (inches)
Mesh (1)
Topcut A (3)
15
7.3
4.3 x 4.3
No
No
2
No
Undercut B (3)
20
7.5
Undercut C (3)
30
8.0(2)
Note: (1) Galvanized welded wire mesh. (2) Final length should be defined in-situ by geotechnical engineer on site
according to Boltec equipment to use (at this stage was necessary to use 7.9 ft. length as maximum bolt length). (3) Shotcrete and bolts in rock walls (not at CRF roof and/or walls).
Long-standing temporary development, over-stressed accesses, and cross-cuts in closure areas would require some level of rehabilitation. This has been
estimated as at least 30% of cross-cuts (in Poor and Fair–Poor rock conditions). A rehabilitation requirement for permanent development should also be considered and estimated based on the linear feet of development completed in Poor rock
conditions (mainly close to the North fault and the Grassy fault).
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13.5.2
Ground Monitoring Program
Due to the rock quality and strength issues summarized in Sections 13.2 and 13.2.7, it will be necessary to install rock stability monitoring instrumentation
in the Grassy Mountain underground workings to monitor the geotechnical behavior of pillars in the different mined areas and backfilled areas. The configuration considers that data collection will be manual and continuous, and its ongoing
interpretation will be the responsibility of the mine operation. The instrumentation may be installed as the lower levels are developed and should focus on measuring the deformations and stresses that may develop during mining operations.
The Grassy Mountain instrumentation program will consider, at least, the following:
•
Underground monitoring:
•
Geotechnical inspections and permanent ground control during the operation.
•
Preparation of procedures for systematic convergence and stress changes measurements.
•
Topographic monitoring using total station, where the convergence of the decline ramp and drifts development will
be surveyed through the laser scanner.
•
Deformation monitoring using a tape extensometer, measuring stations every 98 or 164 ft, depending on visual
availability. This monitoring will be correlated with the topographic monitoring.
•
In-situ stress testing using overcoring. This will indicate those sectors subject to significant changes in
compression or relaxation due to stress redistribution during drift mining. This will be done twice a year by an external service to update the in-situ stress condition.
•
Surface monitoring:
•
Visual inspection of settlements and/or cracks on the surface.
•
Cross-crack measurements, either manual or by wireline extensometer.
•
Topographic monitoring using total station, where the surface deformation above the mine operation will be
measured monthly through an on-site prism network.
•
Satellite InSAR monitoring to measure the surface deformation of the general arrangement, especially the possible
subsidence above the underground portion of the mine. This will be an external service performed once a year, and the measures will be correlated with the topographic measuring above the mine.
13.5.3
Global Extraction Sequence
The mine should be programmed with fast drifts advances, keeping the initial support to the excavation face, the reinforcement, and the final support at 40 ft
as the maximum allowed. The backfill should be installed in reverse and according to schedule, to avoid damage from side drifts excavation, that affects its strength and/or its attachment to the bedrock.
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Special care should be taken of stability as excavations advance in areas where the North and Grassy faults
are present and in the area between them, due to the Poor quality of the rock mass conditions. Sub-parallelism between drifts and these faults result in slow excavations under poor geotechnical conditions with a high risk of instability in roofs and
walls during excavation, according to the trace of the fault. In general, the deposit presents this sub-parallelism condition for the mine design, so it is estimated to be a general operational condition for the mine.
If considered, the presence of a water surface in the upper levels of the mine is an additional variable to the probable instability conditions in the drifts,
so it will be necessary to implement and maintain a rigorous operation.
Compromises have been made in the extraction sequence as a result of the need to
balance grade and production profiles, extraction of wide orebody areas, and other geotechnical constraints. Ultimately, some aspects of the sequence may not be geotechnically optimal, and additional analyses or designs may be required.
13.6
Portal Design
The portal excavation and soft ground tunneling design was initially done by Ausenco during the 2018 PFS and its stability checked by GMS during the
Consolidated Permits stage.
The portal is designed to allow access to the underground mine facilities while providing adequate space for equipment and
vehicles. It will be located uphill and approximately 750 ft south of the primary crusher, at an approximate elevation of 3,749 ft. The portal pad was designed with a 1% inclination toward outside, to allow storm water to flow away from the portal
and toward the storm water drainage ditches. The portal pad will have sufficient space to install the required ventilator infrastructure to be used during the excavation of the decline ramp, construction facilities, and to allow the safe transit of
the development equipment. The pad area was expanded from the initial area designed during the Consolidated Permits process to allow more space for facilities. In addition, the general cut design was updated, increasing the total area of the portal
and the excavation volume.
The portal will have a waste rock excavation volume of 1,120 kft3, which
will be transported and disposed of in the waste rock dump facility designed for the mine operations.
Weak rock mass ground conditions at the portal
require that a shallow box-cut excavation be established to form a suitable face where tunneling can occur. Specialized soft ground tunneling techniques with full rock reinforcement and support will then be required to advance the tunnel for an
approximate 33 ft decline distance, to a point where conventional drill and blast tunneling can begin.
The current design is considered suitable for the
feasibility level. Additional work has been proposed to bring the design to construction level, including a numerical modeling of the excavation sequence to be completed prior to the start of pre-construction. Then, during construction perform site
investigations such as bench geotechnical mapping, portal slope re-design (if necessary), and numerical re-modeling of the excavation.
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13.7
Grade Control
The grade control will be done by the geologist daily. The geologist will collect samples from all producing stopes and send them to an assay laboratory. The
assay grades will be compared to the anticipated grades in the resource block model to monitor the accuracy of the model and maintain the desired head-grade.
When a production stope gets within two rounds of the design, the stope will go on grade control. When a stope is on grade control, every round must be
sampled before the next round can be drilled. The stope may end prematurely or extend past the design if the assayed grade is below or above the cut-off grade.
13.8
Personnel
Please refer to Section 18.2.2.1 for underground personnel requirements.
13.9
Development Design
13.9.1
Mine Design Parameters
The Grassy Mountain orebody will be accessed using a 15 x 15 ft main decline, developed from a portal on surface. The decline will provide the connection to
all services. The design intent is to have the decline located as close as possible to the mineralization in order to reduce transportation costs but sufficiently removed from mining activities to ensure that the decline is geotechnically stable for
the planned LOM. A summary of the mine design criteria is shown in Table 13-11.
Table
13-11: Mine Design Parameters
Design Parameters
Width (ft)
Height (ft)
Diameter (ft)
Length (ft)
Maximum
Gradient (%)
Decline
15
15
NA
varies
15
Level access
15
15
NA
varies
12.5
Power station
15
15
NA
50
0
Level station
15
15
NA
105
0
Stockpile
15
15
NA
50
0
Sump
15
15
NA
50
12
Truck loading bay
15
15
NA
50
0
Ventilation bay
15
15
NA
varies
0
Ventilation raise
NA
NA
12
varies
vertical
Topcut A
15
15
NA
varies
0
Undercut B
20
15
NA
varies
0
Undercut C
30
15
NA
varies
0
Decline turning radius
NA
NA
100
NA
NA
Note: NA = not applicable.
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13.9.2
Level Access
The level station will have a standoff distance from the orebody of approximately 300 ft. This distance is determined by the maximum gradient of the level
access of 12.5%, the geometry of accessing five levels for every one level station, and the geometry of the orebody as shown in Figure 13-18. Therefore, the standoff distance of 300 ft varies slightly
depending on these inputs.
Figure
13-18: Level Access Layout (Looking North)
Source: MDA, 2020 and used unmodified by RESPEC, 2026
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13.9.3
Station Design
There are five stations planned for the mine. Each station will access up to five production levels. The stations will be on the following levels: 3420, 3360,
3285, 3210, and 3135. Each station is to be accessed via the decline. Each station will have a truck loading bay, power bay, ventilation access, stockpile, sump, and level access as shown in Figure 13-19.
Figure
13-19: Station Design
Source: MDA, 2020 and used unmodified by RESPEC, 2026.
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The truck loading bay will be used to load trucks with load–haul–dump (LHD) vehicles. The power
bay will be used to store the mobile load center. The ventilation access will connect on each station via the vent raises. The sump is designed at a -12% gradient and will be used to collect mine water. The stockpile will be used to store material
until it can be loaded into trucks. The level access will provide access to the production stopes.
13.10
Equipment Selection
Mine operations will be based on the usage of mobile mining equipment suitable for underground mines. The estimate of the fleet size was based on first
principles and equipment running-time requirements to achieve the mine production plan. The estimate of the running time for the mine equipment was conducted through the usage of mine-operating factors. Maximum permanent equipment quantities are
summarized in Table 13-12.
Table
13-12: Mining Mobile Equipment List
Mining Mobile Equipment
Model
Quantity
Dual (drill + bolter)
Sandvik DD422i
3
LHD
Sandvik LH307
4
Truck with ejector bed
Sandvik TH320
3
Diamond drilling
Hydracore HC200UG
1
Shotcrete sprayer
GetMan Proshot Concrete Sprayer
1
Shotcrete truck
GetMan ProMix 6
1
Lube truck
Getman A64 SE Lube
1
Water truck
Getman A64 SE Water Sprayer
1
Scissor Lift
Getman A64 SE SL
2
Transportation – Tractor
Kubota 5100
4
Front-end loader
CAT 962H
2
Telehandler
CAT TL1255
2
Dozer
CAT D6T
1
Motor grader
CAT 160
1
4WD twin cab truck
Ford F-350
3
Mine rescue truck
Kovatera KT200
1
13.11
Production and Development Productivity Assumptions
13.11.1
Drilling and Bolting
Production and development drilling and bolting will be done using three Sandvik DD422i as shown in Figure 13-20.
This unit can setup in a heading and bolt the back and then drill the face all in one setup. Drilling and bolting productivities were built up from first principles and vary by heading profile. The results from the first principles are summarized in
Table 13-13 and Table 13-14. The bolting requirements were determined from the geotechnical analysis.
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Figure
13-20: Sandvik DD422i
Source: Sandvik website, 2026
Table
13-13: Drilling First Principles Assumptions
Drilling
Units
Development
15 Topcut
20 Undercut
30 Undercut
Penetration rate
ft/min
4.0
4.0
4.0
4.0
Effective time
%
80
%
80
%
80
%
80
%
Penetration rate
ft/min/eff
3.2
3.2
3.2
3.2
Non-drill time
min
90
90
90
90
Hole length
ft
12
12
12
12
Holes per round
holes
53
50
61
85
Length per round
ft
636
600
732
1,020
Time per round
min/rd
289
278
319
409
Time per round
h/rd
4.8
4.6
5.3
6.8
Operating hours per shift
h
10
10
10
10
Rounds per shift
rd/shift
2.1
2.2
1.9
1.5
tons per round
tons/rd
161
179
239
359
tons per hour
tons/hr
33
39
45
53
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Table
13-14: Bolting First Principles Assumptions
Bolting
Units
Development
15 Topcut
20 Undercut
30 Undercut
Bolting rate
bolts/min
0.2
0.2
0.2
0.2
Effective time
%
80
%
80
%
80
%
80
%
Bolting rate
bolts/min
0.16
0.16
0.16
0.16
Non-bolting time
min
45
45
45
45
Bolts per round
bolts/rd
33
37
43
50
Time per round
min/rd
251
276
314
358
Time per round
h/rd
4.2
4.6
5.2
6.0
Operating hours per shift
h
10
10
10
10
Rounds per shift
rd/shift
2.4
2.2
1.9
1.7
tons per round
tons/rd
161
179
239
359
tons per hour
tons/h
38
39
46
60
13.11.2
Shotcrete
Production and development shotcrete will be sprayed using a GetMan Proshot Concrete Sprayeras shown in
Figure 13-21.
Figure
13-21: GetMan Proshot Concrete Sprayer
Source: Getman website, 2026
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The haulage of the shotcrete will be done using a GetMan ProMix 6 as shown in Figure 13-22.
Figure
13-22: GetMan ProMix 6
Source: Getman website, 2026
Shotcrete sprayer productivities were built up from first principles and vary by heading profile. The results from the first principles are summarized in
Table 13-15. The transmixer productivities are based on ton*miles. The distances used for the ton*mile calculation are shown in Figure 13-1.
Table
13-15: Shotcrete First Principals Assumptions
Shotcrete Spray
Units
Development
15 Topcut
20 Undercut
30 Undercut
Shotcrete rate
ft3/min
2.5
2.5
2.5
2.5
Effective time
%
80
%
80
%
80
%
80
%
Shotcrete rate
ft3/min
2
2
2
2
Non-shotcrete time
min
30
30
30
30
Shotcrete per Round
ft3/rd
134
150
167
202
Time per round
min/rd
97
105
114
131
Time per round
h/rd
1.6
1.8
1.9
2.2
Operating hours per shift
H
10
10
10
10
Rounds per shift
rd/shift
6.2
5.7
5.3
4.6
tons per round
tons/rd
161
179
239
359
tons per hour
tons/hr
100
102
126
164
Note: rd = round.
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Figure
13-23: 3360 Shotcrete Thickness (units in inches)
Source: RESPEC, 2026
The
location and thickness of shotcrete was based on geotechnical recommendations:
•
All long-term development will receive 4 inches of shotcrete
•
All access drifts will receive 4 inches of shotcrete
•
All stope accesses not under backfill will receive 4 inches of shotcrete
•
All stope accesses under backfill will receive 2 inches of shotcrete on the ribs.
An example of the shotcrete application is shown in Figure 13-23.
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13.11.3
Blasting
ANFO will be used for most production blasting and development rounds. Boosters, primers, detonators, detonation cord, and other ancillary blasting supplies
will also be required. Explosives will be stored in a secure powder magazine in accordance with current applicable explosives regulations.
Once the
drilling cycle is complete, the blasting agent will be loaded into the holes with the respective nonel blasting cap and booster. The timing of the round with the nonel caps is extremely important as it is critical to pulling the maximum amount of
distance per round.
Blasting will occur on-demand throughout the shift. Before blasting occurs, any affected areas will be cleared of personnel, and the
blasting location will be announced over the mine communication system. After the blast, an appropriate amount of time must pass to provide adequate ventilation to any affected areas before mining can resume. Blasting productivities were built up
from first principles and vary by heading profile. The results from the first principles are summarized inTable 13-16.
Table
13-16: Blasting First Principles Assumptions
Blasting
Units
Development
15 Topcut
20 Undercut
30 Undercut
Loading rate
ft/min
8
8
8
8
Effective time
%
80
%
80
%
80
%
80
%
Loading rate
ft/min
6.4
6.4
6.4
6.4
Non-blasting time
min
30
30
30
30
Hole length
ft
11
11
11
11
Holes per round
Holes
52
49
60
84
Length per round
ft
546
515
630
882
Time per round
min/rd
115
110
128
168
Time per round
h/rd
1.9
1.8
2.1
2.8
Operating hours per shift
h
10
10
10
10
Rounds per shift
rd/shift
5.2
5.4
4.7
3.6
tons per round
tons/rd
161
179
239
359
tons per hour
tons/h
84
97
112
128
13.11.
4 Mucking
The Sandvik LH307 underground loader as shown in Figure 13-25 with a nominal 4.8 cubic yard bucket capacity will be
used for all underground loading activities.
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Figure
13-24: Sandvik LH307 Underground Loader
Source: Sandvik website, 2026
Backfill placement will also be done using the same loader except the bucket will be replaced with a push plate. The blasted material will be transported to
the underground stockpile located on the level station using the loader. The material will then be loaded into haul trucks at the truck loading bay using the same loader. The material will then be transported to surface. The truck loading bay
intersection will be excavated to a height of 16 ft to provide clearance to load the trucks.
13.11.5
Hauling
The haulage fleet will use Sandvik TH320 trucks as shown in Figure 13-26.
Figure
13-25: Sandvik TH320 trucks
Source: Sandvik website, 2026
The Sandvik TH320 AT AD22 truck is a conventional low-profile underground-mining trucks. The haul trucks will be equipped with an ejector bed for the use of
dumping backfill in the headings. Trucks will be loaded at the truck loading bay. The trucks will transport the material to surface. Once unloaded on the surface, the trucks will be loaded at the backfill plant on surface and haul the backfill
underground to a location that is undergoing backfilling.
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Hauling productivities were built up from first principles. The results from the first principles are
summarized in Table 13-19.
Table
13-17: Haulage First Principles Assumptions
Haulage
Unit
Development
15 Topcut
20 Undercut
30 Undercut
Truck Size
tons
30
30
30
30
Average Haul Dist One Way
ft
9,940
9,940
9,940
9,940
Average Haul Dist One Way
miles
1.90
1.90
1.90
1.90
Average Haul Dist Round Trip
miles
3.80
3.80
3.80
3.80
Average Speed
mph
6
6
6
6
Time for 1 trip
h
0.63
0.63
0.63
0.63
Number of Trips Per Round
trips/rd
6.00
6.00
8.00
12.00
Time Per Round
min/rd
228
228
304
456
Time Per Round
h/rd
3.8
3.8
5.1
7.6
Operating Hours Per Shift
H
10
10
10
10
Rounds Per Shift
rd/shift
2.6
2.6
2.0
1.3
tons Per Round
tons/rd
161
179
239
359
tons Per Hour
tons/h
42
47
47
47
tons*Mile Per Hour
tons*miles/h
180
180
180
180
Ore that is hauled to surface will be placed in the ore stockpile. A front-end surface loader will feed the ore from the
stockpile into the primary crusher. Waste rock hauled to surface will be dumped at a waste-rock storage facility. The tonnage of waste hauled to surface over the LOM is summarized in Figure 13-28. This waste
will be fully utilized over the mine life as cemented rock-fill material, reducing the total amount of borrow material required over the mine life.
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Figure
13-26: Waste Haulage by Year
Source: RESPEC, 2026
13.11.6
Backfilling
Stopes are planned to be backfilled with CRF that will provide confinement on the stope walls.
The backfill method was selected based on the geological and geotechnical conditions of the deposit, as well as the selected mechanized cut and fill mining
method. The main objectives of the backfill is to provide stability to the drifts and to control dilution associated with ore extraction.
Rock from a
borrow pit close to the mine will be used as aggregate. An LHD equipped with a jamming boom and push plate will be used to place the CRF into the drifts.
Laboratory tests were conducted to define the CRF strength. For that, a testing plan was prepared for 12 CRF samples. The entire program involved different
phases such as:
•
Sieve analysis of the aggregate
•
Mixing of samples with two different compositions
•
Casting or molds preparation
•
Curing process
•
Mechanical properties measurements: laboratory testing.
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The sieve analysis of the aggregate was conducted by PACS Laboratory. Approximately 1,392 kg of GM-1mix and
1,392 kg of GM-2 mix were sieved separately and entirely. The aggregate was tested in the “as received” moisture content condition with no drying or washing. Testing was conducted in general accordance with ASTM D-422 Particle Size
Analyses of Soils and as specified by the testing plan on the following sieves:
•
3 inch (75 mm)
•
2 inch (50 mm)
•
1 1⁄2 inch (37.5 mm)
•
1 inch (25.0 mm)
•
3⁄8 inch (19.0 mm)
•
3⁄8 inch (9.5 mm)
•
Number 4 (4.75 mm)
•
Number 10 (2.0 mm).
The aggregate used was compared using Talbot grading. The material used was rock Basalt from a borrow pit near the mine. The material was crushed to less than
4” and sent to MetaRock Laboratories in two (2) bag packages. The results show that the distribution is similar to the Talbot grading. Talbot and Richard (1923) proposed a general equation for combined (fine and coarse) regularly
graded aggregate. Swan (1995) suggested that the Talbot grading equation can be used to make an optimal grading of waste rock for CRF design.
In
general, for a CRF application, a particle size >10 mm is classified as a coarse aggregate, while a particle size of <10 mm is defined as a fine aggregate.
The UCS testing program included 12 samples with a diameter of approximately eight inches and an approximate length of 16 inches. The design cement
percentages were 5% and 7%, both proper percentages used for CRF backfill in mining industry. The design curing times were 14 and 28 days, according to the standard curing time for concrete. Table 13-20
summarizes the CRF mix recipe prepared for UCS testing.
Table
13-18: CRF Mix Recipe for UCS Testing
Mix ID
GM-1
GM-2
Aggregate size
<2 mm to 51 mm
<2 mm to 51 mm
Cement % by weight
5
7
Aggregate for 2.79 ft3 CRF (lb) (material
from Sample 2, under 2 inches)
313.80
313.80
Sand for 2.79 ft3 CRF (lb) (fine material
from Sample 2, under 10 mesh)
47.07
43.93
Cement for 2.79 ft3 CRF (lb)
18.04
25.04
Water for 2.79 ft3 CRF (gal) (water/cement =
1.2)
2.59
3.60
Estimate fresh CRF mix density
(g/cm3)
2.30
2.37
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The mixing, casting and curing processes are shown in Figure 13-29.
Figure 13-27: Mixing, Casting and Curing Process
Note: MetaRock Laboratories, 2020 (Rock Mechanics Testing Report for – CRF Testing. Houston, Texas).
The following CRF capacities and strength results were obtained (Figure 13-30):
•
3.9 to 5.3 MPa of CRF strength with 7% of cement content and 14 days of curing
•
5.2 to 6.1 MPa of CRF strength with 7% of cement content and 28 days of curing
•
1.8 to 2.4 MPa of CRF strength with 5% of cement content and 14 days of curing
•
3.0 to 3.2 MPa of CRF strength with 5% of cement content and 28 days of curing.
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Figure
13-28: UCS Results vs Curing Time
Source: MetaRock Laboratories, 2020 (Rock Mechanics Testing Report for – CRF Testing. Houston, Texas).
Samples with low fines content and large particle concentration, which make rock contact possible, produce a weak zone of failure. A large particle size
concentration can sometimes reduce the strength of CRF. A good relationship between sample density and strength was also found; therefore, a denser CRF with a low content of large particle sizes could have higher strengths.
Future work is required to assess the response of samples composed of 3% cement and 2% fly ash, and 4% cement and 3% fly ash, in order to compare these test
results with the results of 5% and 7% cement, respectively.
As part of the 2026 Feasibility Study Update, GMS reviewed the updated mine layouts,
extraction sequencing and production schedule provided by RESPEC. Based on the review completed, no material changes were identified that would require modification of the backfill design criteria, backfill performance assumptions or backfill
sequencing strategy presented in this section.
13.11.7
Backfill Plant
An Simem WB100 backfill plant, as shown in Figure 13-29, will be constructed near the portal.
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Figure
13-29: Simem WB100 Backfill Plant
Source: SIMEM, 2026
The
waste rock from underground operations will be used for CRF. Additional rock will be excavated and crushed from the surface borrow area. Cement and other supplies will be provided by local suppliers. The plant will produce approximately 3.27 cubic
yards per batch and will require 2 minutes per batch or approx. 2,970 tons per day. The maximum amount of backfill required on a single day in the mine plan is 1,200 tons. The plant is oversized to ensure that the backfill plant will not be a bottle
neck in the mining operation. This plant will also meet the requirement of shotcrete for ground support.
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It is assumed that the truck haulage fleet will get loaded with material underground and haul the material to
surface. After the haul truck dumps the material on surface the haul truck will be loaded on surface with backfill. Each truck will require four batches of backfill from the backfill plant to be fully loaded. The haul truck will haul the backfill
underground and place it in a backfilling location. To summarize, the haul trucks will be loaded with underground material on the way out of the mine and be loaded with backfill on the way into the mine. This is referred to as
“round-haul”. The backfilling assumptions are the same as the haulage assumptions in table 13-20.
13.11.8
Production Scheduling
The scheduling approach utilizes following production calendar, rates, and limits. These resources were assigned to each mining tasks and mine schedule was
developed utilizing these parameters. The calendars applied, production rates, and production limits are shown in tables below.
Table
13-19: Calendars by Crew
Crew
Hours Per Day
Days Per Week
Production mining
24
Mon–Thurs (4)
Production backfilling
24
Mon–Thurs (4)
Contractor development
24
Mon–Sun (7)
Contractor raise bore
24
Mon–Sun (7)
Table
13-20: Production Rates
Name
Quantity
Unit
Lateral development rate
18
ft/d
Vertical development rate
2
ft/d
Production rate
30
ft/d
Backfill rate
800
t/d
Limits were placed on production fields. The limits were based on the first-principle productivity rates, and the mill
capacity and the shotcrete plant capacity. The limits are shown in Table 13-21.
Table
13-21: Production Limits on Production Fields
Production Field
Limit
Unit
Economic material
1,600
t/d
Truck haulage
65,500
ton*mile/month
Transmixer haulage
5,500
ton*mile/month
Drill and Bolter equipment hours
72
h/d
Mucking equipment hours
96
h/d
Blasting equipment hours
24
h/d
Shotcrete sprayer equipment hours
24
h/d
Shotcrete volume
1,100
cubic ft/d
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13.12
Underground Infrastructure and Services
13.12.1
Ventilation
The ventilation network was designed to comply with U.S. ventilation standards for underground mines (Code of Federal Regulations/Title 30. Underground metal
and nonmetal mines. Washington, DC: U.S. Government Printing Office, Office of the Federal Register). Regulatory concentrations for gases are specified by the 1973 American Conference of Industrial Hygienists (ACGIH) threshold limit values (TLVs)
[71 Fed. Reg. 3 28924 (2006)]. For diesel particular matter (DPM), a permissible exposure limit (PEL) of 160 µg/m3 total carbon is specified in the U.S. diesel rule for metal/nonmetal mines
(71 Fed. Reg. 28924 (2006)).
The Mine Safety and Health Administration (MSHA) sets an airflow requirement for the dilution of gas emissions, and an
additional airflow requirement for dilution of DPM. These values are published with the list of approved engines on MSHA’s internet website. Airflow of 100,000 cubic feet per minute (cfm) was selected as a minimum reference for the ventilation
design of each level to meet the MSHA ventilation standards. A mine ventilation network design was built using the VentSim software package as shown in Figure 13-31 and Figure
13-32.
As part of the 2026 Feasibility Study Update, RESPEC reviewed the updated mine layouts and production
schedule. Based on the review completed, no material changes were identified that would require modification of the ventilation requirements and system presented in this section.
Figure
13-30: Ventilation Network (isometric view looking west)
Note: No modifications made in 2026 FS update. Source: MDA, 2020
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Figure
13-31: Ventilation Network (Section View Looking Northwest)
Note: No modification made in 2026 FS update. Source: MDA, 2020
Figure
13-32: Surface Ventilation Fan (Section View)
Source: Spendrup, 2026
Required airflows were determined at multiple stages during the mine life, using equipment numbers and utilization rates, specific engine types and exhaust
output, and the number of personnel expected to be working underground. The designed ventilation system includes the following parameters:
•
Main fan total pressure of 12 inches of water gauge
•
Main fan air flow of 467,000 cfm
•
Main fan power of 500 hp
•
Each active level air flow of 100,000 cfm
•
Only three active levels at any given time
•
Air density of 0.0722 lb/ft3.
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The planned ventilation will use a push/pull system and will require one exhaust fan on surface. A raise bore
will be used to construct ventilation raises between level stations and connecting to the surface fans as shown in Figure 13-34.
Figure
13-33: Design of Vent Raises
Source: MDA, 2020 and modified by RESPEC in 2026.
Each vent raise will have a diameter of 12 ft. Each raise will be steel lined and have an escape ladder. Auxiliary fans will take air from the main circuit
and push the air to the working face on the level using vent ducting and vent bag. Each level will have an auxiliary fan at the level station.
13.12.2
Underground Dewatering
Water will be needed for underground production drilling, bolting, shotcrete, and diamond drilling. The required LOM water supply has been estimated based on
the mine-equipment requirements as summarized in Table 13-24.
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Table
13-22: Estimated Underground LOM Water Requirement
Equipment
Quantity
Water Requirements (gpm)
Operational Factors
Water Required (gpm)
Sandvik DD422i Drill
3
49
70%
103
Diamond Drill
1
20
70%
14
GetMan Proshot Concrete Sprayer
1
10
70%
7
Total Required
124
Factor
20%
Total with factor
150
Water at the face will be pumped to the station sump. From the station sump the water will either be used for equipment water
supply or pumped out to the plant for use in the process circuit. When used for equipment water supply, the sediments will be removed at the station sump. Excess water at the station sump will be pumped up to the next station sump. The water will
continue to be pumped up to the next station until it is pumped out of the mine
The connection between sumps will be a steel pipe in the ventilation
raise. The report titled “Grassy Mountain Gold and Silver Project Mine Dewatering Hydrogeologic Assessment” by Lorax Environmental Services (March, 2020) states the following: “The total estimated range of inflow rates is 12 US
gpm to 78 US gpm.” The dewatering system was designed for 250 gpm which will accommodate both the max inflow rates (78 gpm) and the equipment water requirements rates (150 gpm) in the event that water is not recirculated to the
equipment.
13.12.3
Underground Power
An underground 480 V transformer will be placed near the entrance to the portal at the start of mining. This will supply power to electrical equipment used to
develop the main decline and to portable fans. A main power line will be installed along the rib of the decline to carry 1.4 kV when development has advanced far enough that carrying power at 480 V becomes too inefficient. This line will be
connected to a transformer that will be moved underground. Line power will also be extended to the locations of the two ventilation shafts to supply power to the ventilation fans.
Both transformers will be placed underground in power bays. The transformers will be moved to other power bays depending on the location of the mining
activities.
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Figure
13-34: Mine Load Center (1000 kVA)
Source: Intermountain Electronics, Inc., 2026
13.12.4
Underground Communications
Inside the mine, a leaky-feeder very high frequency (VHF) radio system will be used as the primary means of communication. The system will allow for
communications between the underground mine and surface operations.
13.12.5
Underground Refuge and Escape Ways
Two emergency refuge stations will be necessary in case of fire or rockfalls that would block access and prevent full evacuation of personnel. These refuges
will allow the staff to remain safe in the underground mine for 36 hours. The refuge stations are mobile, each can accommodate up to 16 people within the protected chamber. They will be located strategically from where the mine operation personnel
are located. Figure 13-36 shows an example of a refuge station.
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Figure
13-35: Mobile Refuge Station
Note: Sixteen-person units are used for the 2026 update. Source: MDA, 2020, after MineARC, 2020
All vent raises will be steel lined and equipped with an escape way ladder for secondary evacuation. The primary route for evacuation will be the decline. The
secondary route for evacuation will be the vent raises.
13.13
Mining Costs
Mining costs are summarized in Section 18.
13.14
Life-of-Mine Production
The QP used the Proven and Probable Mineral Reserves to create a mining production schedule using Deswik Scheduler, which allows for the scheduling of both
underground development and production. The primary inputs used to develop the schedule include:
•
The resource block model with defined material types
•
Development centerlines drawn in the direction of mining
•
Solids representing the stopes or production areas to be mined
•
Attributes to define activity types, material types, profiles, etc.
•
Mining sequence among developments and production areas
•
Development and production rates by location
•
Definition of the periods to be used.
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The naming convention for material types considered either ore or waste. Ore was assigned to two categories
based on grade: high-grade or low-grade. High-grade is material that is above the economic cut-off grade. Low-grade is material that is below the mining economic cut-off grade, but above the mill cut-off grade. The basic assumption is that a stope
that is economic to be mined will be processed in its entirety. Thus, if internal waste in an economic stope is classified as Measured or Indicated Mineral Resources, these resources will be converted to Proven or Probable Mineral Reserves,
respectively, and will contribute to the revenue stream.
Waste comprises:
•
Material classified as Measured or Indicated Mineral Resources that is below both the mining cut-off grade and
the mill cut-off grade.
•
Material classified as Inferred Mineral Resources.
Waste is considered to be internal dilution within a stope, which would be mined and sent to the process plant. All waste material is considered to have zero
grade and therefore does not contribute to the revenue steam.
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The final production schedule was calculated in Deswik Scheduler and then summarized in Excel. The mine
production summary is presented in Table 13-25. The material to be sent to the mill is summarized in Table 13-26. The development schedule is summarized in Table 13-27.
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Table
13-23: Mine Production Summary
Year
0
1
2
3
4
5
6
7
8
9
10
Total
Mined Measured and Indicated Resource Above Cut-off Gradetons (tons x 1,000)
3
183
240
226
32
225
203
258
199
196
15
1,980
Grade (oz Au/ton)
0.277
0.187
0.217
0.208
0.217
0.217
0.234
0.174
0.158
0.181
0.126
0.199
Ounces (oz Au x 1,000)
1
34
52
47
50
49
48
45
31
36
2
395
Grade (oz Ag/ton)
0.282
0.264
0.292
0.273
0.312
0.294
0.279
0.319
0.308
0.314
0.255
0.295
Ounces (oz Ag x 1000)
1
48
70
62
72
66
57
82
61
62
4
585
Mined Measured and Indicated Resource Subgradetons (tons x 1,000)
2
29
30
29
33
26
20
22
19
15
1
226
Grade (oz Au/ton)
0.033
0.047
0.046
0.045
0.043
0.046
0.048
0.048
0.053
0.047
0.048
0.046
Ounces (oz Au x 1,000)
0
1
1
1
1
1
1
1
1
1
0
11
Grade (oz Ag/ton)
0.212
0.161
0.180
0.153
0.153
0.168
0.173
0.204
0.195
0.196
0.181
0.173
Ounces (oz Ag x 1000)
0
5
5
4
5
4
3
5
4
3
0
39
Total Mined to Stockpiletons (tons x 1,000)
5
212
269
255
265
251
223
280
217
212
17
2,207
Grade (oz Au/ton)
0.172
0.168
0.199
0.189
0.195
0.199
0.218
0.164
0.149
0.171
0.119
0.184
Ounces (oz Au x 1,000)
1
36
53
48
52
50
49
46
32
36
2
405
Grade (oz Ag/ton)
0.252
0.250
0.280
0.259
0.292
0.281
0.269
0.310
0.299
0.305
0.249
0.283
Ounces (oz Ag x 1000)
1
53
75
66
77
71
60
87
65
65
4
624
Total with Ore Loss & Dilutiontons (tons x 1,000)
5
226
287
272
284
265
240
298
234
227
19
2,358
Grade (oz Au/ton)
0.167
0.163
0.191
0.182
0.187
0.193
0.207
0.159
0.144
0.165
0.111
0.177
Ounces (oz Au x 1,000)
1
37
55
50
53
51
50
47
34
37
2
417
Grade (oz Ag/ton)
0.254
0.246
0.274
0.254
0.283
0.278
0.261
0.305
0.291
0.299
0.235
0.277
Ounces (oz Ag x 1000)
1
56
79
69
80
74
63
91
68
68
4
653
Waste
Waste tons (t x 1,000)
64
76
14
3
25
16
22
12
6
4
—
242
Backfill
Cemented Rockfill tons (tons x 1,000)
1
124
196
215
149
209
185
226
174
146
19
1,645
Footage
Lateral Footage (ft)
4,367
17,814
17,178
14,873
15,949
14,146
12,960
17,107
12,436
11,636
1,010
139,477
Vertical Footage (ft)
260
402
—
—
—
—
—
—
—
—
—
662
Total Footage (ft)
4,627
18,216
17,178
14,873
15,949
14,146
12,960
17,107
12,436
11,636
1,010
140,139
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Table
13-24: Material to the Mill
Year
0
1
2
3
4
5
6
7
8
9
10
Total
Low-Grade Material
tons (tons x 1,000)
2
31
31
31
35
28
21
23
20
17
2
242
Grade (oz Au/ton)
0.035
0.047
0.047
0.047
0.044
0.048
0.048
0.050
0.053
0.047
0.049
0.047
Ounces (oz Au x 1,000)
0
1
1
1
2
1
1
1
1
1
0
11
Grade (oz Ag/ton)
0.216
0.156
0.178
0.155
0.150
0.171
0.170
0.206
0.186
0.190
0.179
0.171
Ounces (oz Ag x 1000)
0
5
6
5
5
5
4
5
4
3
0
41
High-Grade Material
tons (tons x 1,000)
3
195
256
241
249
237
219
275
213
210
17
2,116
Grade (oz Au/ton)
0.267
0.181
0.209
0.200
0.207
0.211
0.222
0.168
0.152
0.174
0.117
0.191
Ounces (oz Au x 1,000)
1
35
53
48
52
50
49
46
32
37
2
405
Grade (oz Ag/ton)
0.283
0.260
0.286
0.267
0.302
0.291
0.270
0.313
0.301
0.308
0.240
0.289
Ounces (oz Ag x 1000)
1
51
73
64
75
69
59
86
64
65
4
612
Total to Plant
tons (tons x 1,000)
5
226
287
272
284
265
240
298
234
227
19
2,358
Grade (oz Au/ton)
0.167
0.163
0.191
0.182
0.187
0.193
0.207
0.159
0.144
0.165
0.111
0.177
Ounces (oz Au x 1,000)
1
37
55
50
53
51
50
47
34
37
2
417
Grade (oz Ag/ton)
0.254
0.246
0.274
0.254
0.283
0.278
0.261
0.305
0.291
0.299
0.235
0.277
Ounces (oz Ag x 1000)
1
56
79
69
80
74
63
91
68
68
4
653
Table
13-25: Development Schedule
Year
-
1
2
3
4
5
6
7
8
9
10
Total
Development Type
Main Decline (ft)
3,084
2,057
—
—
—
—
—
—
—
—
—
5,141
Level Station (ft)
368
909
—
—
—
—
—
—
—
—
—
1,277
Level Development Waste (ft)
244
1,341
849
181
1,511
917
1,340
733
362
235
—
7,715
Level Development Ore (ft)
298
13,081
16,329
14,692
14,438
13,229
11,620
16,373
12,074
11,401
1,010
124,546
Vent Drift (ft)
374
424
—
—
—
—
—
—
—
—
—
798
Vent Raise (ft)
260
402
—
—
—
—
—
—
—
—
—
662
Total Development (ft)
4,627
18,216
17,178
14,873
15,949
14,146
12,960
17,107
12,436
11,636
1,010
140,139
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Figure 13-36 and Figure 13-37
show the proposed yearly production schedule in terms of tons and gold and silver ounces for the LOM.
Figure
13-36: Proposed Mine Production Schedule (tons by period)
Source: RESPEC, 2026
Figure
13-37: Mine Production Schedule (ounces by period)
Source: RESPEC, 2026
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14
PROCESSING AND RECOVERY METHODS
14.1
Introduction
Based on the information and metallurgical test results summarized in Section 10, the Grassy Mountain gold–silver mineralization is considered
amenable to cyanide leaching as a recovery method. The process plant will consist of a 750 tons/day, two-stage crushing, ball mill, carbon-in-leach (CIL), elution, and electrowinning circuit, all of which are well-known, conventional, processing
unit operations.
14.2
Process Design Criteria
The process plant is designed for treatment of 750 tons/day or 34 tons/hour based on an availability of 7,998 hours per annum or 91.3%. The crushing section
design is set at 70% availability, and the gold room availability is set at 52 weeks per year including two operating days and one smelting day per week. The plant is designed to operate with two 12-h shifts per day, 365 days per year, and
will produce doré bars.
Key design parameters derived from metallurgical testwork, as well as the resulting sizing parameters of major equipment,
are shown in Table 14-1.
Table
14-1: Process Design Criteria
Description
Units
Value
Plant throughput
tons/year
273,750
Mine life
years
7.8
LOM average grade, Au
oz/ton
0.177
LOM average grade, Ag
oz/ton
0.277
Design grade, Au
oz/ton
0.178
Design grade, Ag (corresponding to design grade for Au)
oz/ton
0.275
Operating Schedule and Stockpile
Crusher availability
%
70
Plant availability (milling and leach)
%
91.3
Crusher operating time
hours/year
6,132
Plant operating time
hours/year
7,998
Gold room operating days
days/year
104
Gold room smelting days
days/year
52
Stockpile type
—
Conical
Stockpile repose angle
°
37
Stockpile retention time
hours
24
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Description
Units
Value
Ore Properties
Specific gravity (average)
—
2.6
JK Axb (25th percentile)
—
30.4
Bond rod work index (BRWi) (75th
percentile)
kWh/ton
22.3
Bond ball work index (BBWi) (75th
percentile)
kWh/ton
26.9
Bond abrasion index (Ai) (average)
g
0.641
Primary Crushing
Throughput, nominal
tons/hour
45
Primary crusher type
Jaw
Primary crusher model
Metso C80 or
equivalent
Closed size setting
inches
2.0
Feed size, F80
inches
8.3
Crushing product, P80
inches
1.9
Secondary Crushing
Circulating load, nominal
%
263
Secondary crusher type
Cone
Secondary crusher model
Metso HP200
or equivalent
Closed size setting
inches
0.6
Feed size, F80
inches
1.6
Milling and Classification
Throughput, nominal
tons/hour
34.2
Ball mill dimensions (diameter x effective grinding length)
Ø x EGL
(ft)
12 x 16
Ball mill required power
horsepower
1,021
Ball mill installed power
horsepower
1,341
Ball mill product P80
mesh (µm)
150(106)
Circulating load, max for design
%
350
Cyclone overflow solids
%
45
Carbon-In-Leach
Total leach time required
hours
24
Total leach time available
hours
27
Number of tanks
number
1 pre-aeration
+ 2
leaching + 7
adsorption
Cyanide addition
lb/ton
0.68
Lime addition
lb/ton
2.1
Carbon concentration
lb/gallon
0.21
Carbon loading (Au + Ag)
oz/ton
214
Carbon consumption
lb/ton
0.06
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Description
Units
Value
Desorption/Electrowinning/Refining
Elution method
—
Pressure Zadra
Carbon batch size
ton
2.2
Elution cycles per week
number
7
Furnace capacity, Au + Ag
lb/smelt
57.5
Cyanide Destruction
Cyanide reduction system
—
SO2 /air
Residence time, max for design
minutes
90
CNWAD in feed, maximum for design
ppm
200
CNWAD discharge, not to exceed
ppm
30
CNWAD discharge target for design
ppm
15
SO2 addition
lb/lb CNWAD
6.4
Hydrated lime addition
lb/lb CNWAD
10.8
Cu addition
lb/lb CNWAD
0.11
14.3
Process Flowsheet Development
The process flowsheet was developed based on information from the metallurgical testwork as outlined in Section 10. The crushing and grinding circuit
sizing were determined using Bruno and Ausgrind (Ausenco’s in-house power-based comminution model) simulations, respectively. The flowsheet developed previously was modified to a simpler, lower capital cost alternative comprising:
•
two-stage crushing circuit
•
grinding circuit
•
hybrid leach-CIL circuit with pre-aeration
•
mercury removal circuit
•
cyanide destruction.
The simplified overall flowsheet is shown in Figure 14-1. The plant site layout is shown in Figure 14-2.
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Figure
14-1: Simplified Overall Flowsheet
Source: Ausenco, 2020.
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Figure
14-2: Proposed Plant Site Layout
Source: Ausenco, 2020.
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14.4
Overall Process Description
The plant feed will be hauled from the underground mine to a mobile crushing facility that will include a jaw crusher as the primary stage and a cone crusher
for secondary size reduction. The crushed ore will be ground by a ball mill in closed circuit with a hydrocyclone cluster. The hydrocyclone overflow with P80 of 150 mesh (106 µm) will
flow to a leach-CIL recovery circuit via a pre-aeration tank.
Gold and silver leached in the CIL circuit will be recovered onto activated carbon and
eluted in a pressure Zadra-style elution circuit and then precipitated by electrowinning in the gold room. The gold-silver precipitate will be dried in a mercury retort and then mixed with fluxes and smelted in a furnace to pour doré bars.
Carbon will be re-activated in a carbon regeneration kiln before being returned to the CIL circuit. Mercury is collected and shipped off site for third party storage.
CIL tailings will be treated for cyanide destruction prior to pumping to the TSF for disposal.
14.4.1
Crushing Circuit
The crushing facility will be a two-stage crushing circuit that will process the run-of-mine (ROM) ore at an average rate of 45 tons/hour. The major
equipment and facilities at the ROM receiving and crushing areas will include:
•
ore stockpile
•
ROM hopper
•
vibrating pan feeder
•
primary jaw crusher
•
coarse ore screen
•
secondary crusher surge bin
•
secondary crusher vibrating feeder
•
secondary cone crusher
•
fine ore bin
•
feed and product conveyors.
Ore will be trucked from underground and dumped directly into the ROM hopper or onto the outdoor stockpile during crushing circuit downtime. A front-end
loader will reclaim ore from the stockpile and move it to the ROM hopper as necessary.
The ROM hopper will continuously feed a vibrating pan feeder which
will discharge into the primary jaw crusher. After primary crushing, the ore conveyor will bring the ore to a coarse ore screen. A belt magnet at the end of the ore conveyor will be present to prevent pieces of metal from continuing onto the coarse
ore screen.
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Oversize from this screen will be transferred by the secondary crusher feed conveyor to the secondary crusher
surge bin. This conveyor will be fitted with a metal detector for the secondary crushing circuit to be temporarily shut down for tramp metal removal. Ore from the secondary crusher surge bin will pass over the second crusher vibrating feeder and
into the secondary crusher. After secondary crushing, the ore will recirculate to the coarse ore screen in combination with ore from the primary jaw crusher via the ore conveyor.
Undersize from the coarse ore screen will be taken by the product conveyor to the fine ore bin. The product conveyor will have a weightometer to monitor the
crushing circuit throughput.
The fine ore bin discharge feeder will feed ore from the fine ore bin onto the ball mill feed conveyor and over to the
grinding circuit and will be fitted with a weightometer to provide data for feed-rate control to the grinding circuit.
14.4.2
Grinding Circuit
The grinding circuit will have an average feed rate of 34.2 tons/hour and will consist of a ball mill and a cyclone cluster in a closed circuit. The
recirculating load will have a maximum of 350%. The grinding circuit will be designed for a product size P80 of 150 mesh (106 µm). The major equipment in the primary grinding circuit will
include:
•
one 12-ft diameter (inside shell) by 16-ft effective grinding length (EGL) single-pinion ball mill driven by a
single 1,341 hp fixed-speed drive motor; and
•
one cyclone cluster.
As required, steel balls will be added into the ball mill using a ball bucket and ball charging chute to maintain grinding efficiency.
Crushed ore will travel along the ball mill feed conveyor and discharge directly into the ball mill via the mill feed chute. Process water will be added to
reach a pulp density of 72% solids (by weight) through the ball mill, which will then discharge to the cyclone feed pump box. Trash or broken mill balls will be discharged to a scats bunker and removed by a front-end loader. Additional process water
will be added to the cyclone feed pump box to achieve a density of 63.5% w/w solids, which will then be pumped to the cyclone cluster. The cyclone underflow will recirculate to the mill feed chute. The cyclone overflow will discharge at
45% w/w solids and report to a trash screen. Trash screen oversize will be sent to a trash bin. The slurry will then flow by gravity to the pre-aeration tank.
Maintenance activities in the grinding and classification area will be serviced by a mill area crane, and a grinding area hoist, which will be used for ball
mill charging duties and minor lifts. Spillages in the grinding and classification area will be pumped by the grinding area sump pump into the cyclone feed pump box.
14.4.3
Leach/CIL
A pre-aeration tank is included ahead of the leach circuit, as testwork showed this reduced consumption of cyanide and improved recovery. Testwork determined
that the optimal leach residence time for gold is 24 hours.
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The adsorption circuit configuration selected was a hybrid leach–CIL circuit (two leach, seven CIL
tanks). This circuit configuration is beneficial as it achieves higher loadings of gold on carbon (gold is fast-leaching and approximately 85% of gold is expected to be dissolved before adsorption, resulting in higher loaded carbon grades in the
first adsorption tank). This translates into lower soluble losses and a smaller elution circuit size. Selection of identical tank sizes for leach and CIL simplifies tank access and reduces maintenance spares holding. Each tank has a capacity of
42,250 gallons.
The pre-aeration tank will mix the cyclone overflow with low-pressure air. Slurry will overflow the pre-aeration tank to the first
leach tank, where lime will be added at a rate of 2.1 lb/ton of feed. Cyanide will be added into both leach tanks at a rate of 0.68 lb/ton of feed, together with low-pressure air.
The slurry will then overflow into seven CIL tanks. The first four CIL tanks will also be fed low-pressure air. Barren carbon will be added to the last CIL
tank and will travel up through the circuit in the opposite direction from the slurry flow (counter-current flow). Carbon will advance once per day with carbon transfer pumps, which pump carbon-laden slurry to the next tank in the train. Carbon will
be retained in the tanks after the transfer with inter-stage screens, which will have mesh baskets sized to allow slurry to pass through but not the loaded carbon.
Leached tailings will overflow the last tank to the detox tank which in turn will overflow to the carbon safety screen. This screen will collect carbon that
would otherwise be lost to the tailings in the event of a hole in one of the inter-stage screens. Loaded carbon will be pumped from the first CIL tank to the elution circuit via a loaded-carbon screen, which will separate the carbon from slurry and
send the slurry back to the leach circuit.
14.4.4
Carbon Management
14.4.4.1
Acid Wash
Loaded carbon from the leach circuit will be loaded into an acid-wash column, where it will be submerged in a 3% w/w hydrochloric acid solution in order
to dissolve lime scale that would otherwise interfere with the elution and adsorption process. After soaking for 30 minutes, the acid will be drained, and two bed volumes of raw water will be circulated through the column to rinse and neutralize the
acid from the carbon. After rinsing, the carbon will be pumped to the elution column via carbon-transfer water.
14.4.4.2
Carbon Elution
A pressure Zadra circuit was selected for elution of gold and silver from carbon due to the small carbon processing requirements of the CIL circuit and unknown
water quality from the raw water wells. A pressure Zadra circuit is less complicated than comparable alternatives, and is less sensitive to poor water quality, which makes it a better choice in this instance.
Strip solution (eluate) will be made up in the strip-solution tank using raw water dosed with 2% w/w sodium hydroxide and 0.2% w/w cyanide to form an
electrolyte for the electrowinning process. This solution will be circulated through the elution column via an eluate heater, which heats the solution, the carbon, and the column to 275°F. The elution system will be pressurized at a maximum
pressure of 65 psi (450 kPa) to keep the solution from flashing to steam in the heater or elution column.
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A recovery heat exchanger will transfer heat from the hot pregnant solution exiting the column to the
incoming solution before passing through the solution heater. This will reduce the energy required to maintain the solution temperature and cool the pregnant solution before it enters the electrowinning cell. Once the required system temperature is
reached, the hot pregnant eluate solution will be directed to the electrowinning cell, where the metals will be plated onto cathodes. Solution continues to circulate through the elution column and electrowinning cell. The process will continue to
deposit metals into the electrowinning cell for a maximum of 16 hours.
14.4.4.3
Carbon Regeneration
At the end of the elution cycle, the barren carbon will be transferred to the regeneration kiln feed hopper where it will be fed into the regeneration kiln.
The kiln will regenerate the carbon by burning off any organic material fouling the carbon that would hinder its ability to absorb metals in the CIL circuit. The kiln’s operating temperature will be 1,382°F. The kiln will be fitted with
mercury abatement equipment to capture residual mercury on barren carbon.
Regenerated carbon will exit the kiln and report to the water-filled quench
tank. The quench tank will serve as a holding place for the carbon while it is waiting to be returned to the circuit. Regenerated carbon will be pumped from the quench tank through a barren carbon screen to remove fines as well as dewater the
carbon. Oversize from the screen will then re-enter the CIL circuit via the CIL tank at the end of the bank.
14.4.4.4
Carbon Transport Water
All carbon movements in the elution and regeneration circuits will be accomplished using carbon transport water. A transport-water tank and pump will supply
transport water to carbon movement demands as needed. The acid wash and elution columns will be fitted with internal strainers to allow the transport water to drain out while the column retains the carbon.
Transport water will pick up fines when moving carbon due to the attrition associated with carbon movement. The transport water tank will be periodically
drained to tailings.
14.4.5
Gold Room
The gold room will house the electrowinning cell, smelting furnace, and associated support equipment within a secured area.
One day per week, the electrowinning cell will be opened so that sludge can be cleaned out manually with a high-pressure water hose. Sludge from the clean-up
will flow by gravity to the sludge settling tank and into the gold room sludge filter press to be dewatered. Dewatered sludge will then be transported manually using a tray to the mercury retort oven for mercury removal as well as simultaneous
drying. Mercury collected will be sent off site for third-party processing.
Dried sludge will be removed from the oven the following day and combined
with fluxes in a flux mixer before reporting to the smelt furnace. Once all the mixture has been added to the furnace and enough time has elapsed for the material to fully melt, the slag will be poured into a conical slag pot. The liquid metal will
then be poured into molds on a mound tray. Cooled doré will then be cleaned, weighed, and stamped. The bars will be placed in a vault to await shipment to a refinery.
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Dust collection will be provided in the gold room for smelting. Extraction fans are planned for the kiln,
electrowinning cell, retort/drying oven, and smelting-furnace off gasses. All extraction fans will lead to a gas scrubbing system.
14.4.6
Cyanide Detoxification and Tailings Deposition
A cyanide-destruction circuit will be included in the design to comply with tailings-discharge permit requirements. Testwork shows that SO2/air process was an effective detoxification method at reducing weak-acid dissociable (WAD) cyanide levels to 15 mg/L (30 mg/L maximum).
The CIL tailings will be pumped to the cyanide detoxification tank, where lime will be added to buffer pH, copper sulfate will be added as a reaction
catalyst, and sodium metabisulfite (SMBS) will be added as an SO2 source. The tank is sized to provide 90 minutes of residence time for the reaction to reach completion.
Detoxified slurry will overflow to the tailings pump box where it will be pumped to the TSF by the final tailings pumps. At the TSF, the tailings will be
deposited using spigot manifolds positioned along the rim of the impoundment to create low-angle deposition beaches. The position of the spigot manifolds will be moved periodically to produce an even beach head and push decant water towards the
decant water pool. A pontoon-mounted decant-return water pump will be provided to pump decant water back to the process water tank for re-use in the plant.
14.4.7
Reagent Handling and Storage
Reagents will be prepared and stored in separate self-contained areas within the process plant and delivered by individual metering pumps or centrifugal pumps
to the required addition points. Acidic and basic reagents will be stored and mixed in physically separated areas to ensure no exposure of cyanide to acidic chemicals, which would generate hydrogen-cyanide gas.
Estimated reagent consumptions are as follows:
•
Lime: 6.3 lb/ton of ore processed
•
Sodium cyanide: 0.91 lb/ton of ore processed
•
Sodium metabisulfite: 3.6 lb/ton of cyanide processed.
14.4.7.1
Hydrated Lime
Preparation of hydrated lime slurry will require:
•
a bulk storage silo
•
a mixing tank
•
dosing pumps feeding a ring main
•
automatically controlled dosing point from the ring main.
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Hydrated lime will be used in leaching and detoxification for pH control. Hydrated lime powder will be
delivered to site by bulk tankers and blown into the lime bulk storage silo. When the mixing-tank is low, hydrated lime will be added to the tank via a rotary valve and screw feeder. Process water will be added at the same time to maintain the
mixture strength of 20% w/w, forming a suspended lime slurry.
The suspended lime slurry will be distributed to the various dosage points via a ring main
that provides constant flow to various destinations. Dosing will be accomplished with drop lines off the ring main with automated on-off valves that open when pH is low and close when the target pH is reached.
14.4.7.2
Sodium Cyanide
Storage and distribution of sodium cyanide (NaCN) will require:
•
a bulk storage tank
•
a ring main
•
dosing pumps.
NaCN will be used in the leach circuit as a lixiviant and in elution as a carbon-stripping aid. Aqueous sodium cyanide will be delivered to site by bulk
tanker at 30% purity and emptied into the sodium cyanide storage tank. NaCN solution will be distributed to the various dosage points via a ring main that provides constant flow to various destinations.
14.4.7.3
Sodium Hydroxide
Preparation of sodium hydroxide (NaOH) will require dosing pumps. NaOH will be delivered to site in 264.2-gal totes at a solution strength of around 50% w/w.
New totes will be lifted onto a mount using a forklift. Dosing will be done at full strength using dedicated positive-displacement metering pumps. NaOH will be used as an electrolyte in carbon elution/electrowinning.
14.4.7.4
Sodium Metabisulfite
Preparation of SMBS will require:
•
a bulk handling system
•
mixing and holding tanks
•
dosing pumps.
SMBS will be a source of SO2 for cyanide destruction with the SO2/air process. It will be delivered to site in 1.1-ton bulk bags.
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SMBS will be held in the SMBS storage tank after it is mixed. When the storage-tank is low, a SMBS mixture
will be started by dropping a bulk bag of SMBS onto a bag breaker, which discharges SMBS into the mix tank. The mix tank will have been previously filled with the required amount of process water to produce a mixture strength of 20% w/w. Once
mixing is complete, the SMBS will be dosed from the storage tank to the cyanide detoxification circuit. There will be two positive displacement metering pumps dedicated to this process, one of which will be in place as a spare.
14.4.7.5
Copper Sulfate
Distribution of copper sulfate (CuSO4) will require dosing pumps. CuSO4 will be delivered to site in 53-gal drums at a solution strength of 15% w/w. New drums will be listed onto a mount using a forklift. Dosing to the detoxification circuit will be done using
dedicated positive-displacement metering pumps.
14.4.7.6
Hydrochloric Acid
Distribution of hydrochloric acid (HCl) will require a dosing pump. HCl will be used to remove lime scale from loaded carbon in the acid-wash column of the
elution circuit. HCl will be delivered in 264.2-gallon totes at 32% w/w solution strength and will be housed in the reagent handling area.
Raw water will
be added to the HCl to a strength of 3% w/w by inline mixing ahead of the acid-wash column.
14.4.8
Air Supply and Distribution
14.4.8.1
Low-Pressure Air
Two low-pressure air blowers will supply air to the pre-aeration, leach, and detoxification circuits. The installed blowers will be multiple-stage,
centrifugal-type blowers and will be used with a “blow-off” arrangement to adapt to fluctuations in air demand.
14.4.8.2
Plant and Instrument Air
Two plant-air compressors (duty/standby) will provide high-pressure compressed air, to meet the demand for plant and instrument-air requirements. Wet plant air
will be stored in the plant-air receivers to account for variation in demand prior to being distributed through the plant. Wet air will report to cyanide offloading. Instrument air will be filtered then dried in the instrument-air dryer before
reporting to the gold room or general plant distribution.
14.4.9
Water Supply and Distribution
14.4.9.1
Raw Water
Raw water will be pumped from borehole wells via a well water pump to the raw-water storage tank. Raw water in the raw-water storage tank will be used to
supply the process water tank, gland water, reagent mixing, and fire-protection requirements. The raw water tank is sized to include a fire water reserve.
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14.4.9.2
Potable Water
Potable water will be sourced from the raw water tank and treated in the potable water treatment plant. Treated water will then be stored in the potable-water
storage tank for distribution by two potable-water pumps in a duty/standby configuration.
14.4.9.3
Gland Water
Gland water will be supplied from the raw-water tank and distributed to the plant by two gland-seal water pumps in a duty/standby configuration.
14.4.9.4
Process Water
Process water primarily consist of TSF reclaim water. Process water will be stored in the process water storage tank and distributed by two process water
pumps, in a duty/standby configuration.
14.5
Personnel
The number of process operations and maintenance personnel is provided in Section 18.2.3.5.
14.6
Sampling and Metallurgical Laboratory
The process plant will be equipped with automatic samplers to collect shift and routine samples for aqua-regia digestion, AA analysis, and fire assays. Samples
to be taken will include head, intermediate products, tailings, and doré. The data obtained will be used for product quality control, metal accounting and process optimization.
The metallurgical laboratory will perform metallurgical tests for quality control and optimization of the process flowsheet. The laboratory will include
equipment such as laboratory crushers, ball mill, sieve screens, bottle rollers, leach reactors, balances, DO meters, and pH meters.
14.7
Projected Energy Requirements
The installed power for the process plant will be 4,445 hp and the power consumption is estimated to be 72 kWh/ton processed.
14.8
Project Water Requirements
The overall projected plant water balance is shown in Figure 14-3. Raw water demand is projected to be 47,023 gallons
per day (178 m3/day).
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Figure
14-3: Projected Daily Plant Water Balance , at average LOM
throughput
Source: Ausenco, 2026.
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15
INFRASTRUCTURE
15.1
Introduction
Infrastructure contemplated in the FS includes:
•
Underground mine, including portal and decline
•
Roads: main access road, site access road, borrow pit haul road, tailings storage facility haul road, temporary
waste rock storage facility haul road, explosives light vehicle access road and ventilation raise and laydown light vehicle access road
•
Site main gate and guard house
•
Administration building, training, first aid, change house and car park
•
Control room
•
Reagent storage area
•
Gold room
•
Assay laboratory and sample preparation area
•
Plant workshop and warehouse
•
Truck shop, warehouse, wash pad
•
Fuel facility, fuel storage and dispensing
•
Water wells
•
14.4 kV overland power line
•
Fresh water supply and treatment
•
Raw water tank
•
TSF
•
Temporary Waste Rock Storage Facility (TWRSF)
•
Explosives magazine.
A layout of the proposed major infrastructure is included in Figure 15-1.
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Figure
15-1: Proposed Infrastructure Layout Plan
Source: Ausenco, 2020
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15.2
Access
Access to the Project area is described in Section 4. The FS envisages that the main access road to Grassy Mountain will use an existing BLM road to the
site. This road is approximately 17 miles long and will be upgraded to include some straightening and widening in portions.
15.3
Temporary Waste Rock Storage Facility (TWRSF)
The following summarizes the results and interpretations for the TWRSF based on data collected and engineering means and methods presented in the 2021 Detailed
Design Report (Golder, 2021d).
Waste rock materials generated during mining will be stockpiled in a TWRSF near the TSF for use as either cement rock
backfill to support the underground mining operation or as an operational layer above the tailings surface for closure as discussed in Section 15.5.6. As required by the Oregon Administrative Rule, the potential sulfides in the waste rock
material requires the TWRSF to be a geomembrane-lined facility. The containment and drainage collection systems installed below the TWRSF will be the same systems used for the TSF impoundment basin described in Section 15.5.
Above the geomembrane liner, a collection system consisting of perforated piping will be installed within the drainage layer to collect water coming in
contact with the waste rock. Captured precipitation infiltrating through the waste rock will be conveyed to the TSF reclaim pond for monitoring and management. The TWRSF collection pipe will remain isolated from the TSF underdrain collection system
so the water can be handled separately, if necessary.
The location of the TWRSF, adjacent to the TSF, will allow the lining system to tie into the TSF
lining system to provide continuous containment (see Figure 15-2). The TWRSF collection pipe will gravity drain through the TSF impoundment where it will be installed within the TSF drainage layer and
ultimately outlet at the TSF Reclaim Pond for independent monitoring and management.
During reclamation, remaining waste rock (if any) stockpiled on the
TWRSF will be removed and placed as an operation layer above the tailings surface as part of the TSF reclamation strategy. The TWRSF lining system will either be removed or buried upon completion of mining operations. Further discussion of the TWRSF
closure strategy is discussed in Section 17.8.
15.4
Basalt Borrow Quarry
The Basalt Borrow Quarry will be located on the east side of the mine area (refer to Figure 15-2) where there are
basalts that are believed to be suitable for construction, mine-backfill and reclamation materials:
•
Construction.
•
Run-of-mine (ROM) material for fill and TSF-embankment construction, as required.
•
Screened and processed materials for drainage and filter materials in the TSF and TWRSF, as required; Backfill:
backfill and CRF material for backfilling of underground stopes; crushed to -6 inches.
•
Reclamation: screened and processed materials for drainage and filter materials, as required.
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Borrow material from the Basalt Borrow Quarry will be mined using contract mining. During initial
construction, where more material is needed, the borrow mining will use larger equipment, while smaller equipment will be used during production when the amount of material required is reduced. A small contractor laydown-yard is planned near the
main borrow source area.
15.5
Tailings Storage Facility
The following summarizes the results and interpretations for the tailings storage facility based on data collected and engineering means and methods presented
in the 2021 Tailings Storage Facility and Temporary Waste Rock Storage Facility detailed design report (Golder, 2021d).
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The TSF will be constructed in three primary stages to store a total of 3.64 Mt of tailings and
industry-accepted design criteria for geotechnical stability and flood events during operations and long-term closure (passive care). The combined tailings dam embankment and impoundment basin will occupy an ultimate footprint of approximately 108
acres (4.705 million sqft), as shown on Figure 15-2. The TSF centroid is located is located in mine grid at 15,865,300 N and 1,543,500 E approximately 0.3 mi west and 0.1 mi north of the overall mine site
centroid.
Figure 15-2: Overall TSF Layout
Source: Golder, 2021d.
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Conventional tailings are transported to the TSF via a tailings delivery pipeline from the mill. Tailings are
then deposited into the TSF impoundment from the staged perimeter road via sub-aerial deposition. As tailings are deposited, free water separates from the slurry mix to form the supernatant pool. Through consolidation and seepage, additional water
reports to the impoundment underdrain system where it drains via gravity into the reclaim pond system. Water recovery from the TSF will include independent pumping and piping systems from the supernatant pool to and reclaim pond which will combine
into a single return water system for reuse at the mill.
Non-contact stormwater is managed through a series of permanent and temporary stormwater
diversion channels constructed upgradient of the TSF. Precipitation falling on the TSF and areas downgradient of the stormwater channels ultimately reports to the supernatant pool where it is incorporated into the process circuit.
Additional details regarding design criteria, methodology, and engineering evaluations of the TSF are presented in the following sections.
15.5.1
Topography, Drainage, and Vegetation
In general, the mine site and surrounding area has rolling topography with bedrock exposed at or near the ground surface in upland and hill areas, including
Grassy Mountain proper. Within the TSF area, as topographic elevation drops, the surrounding hills transition into broad valleys with shallow alluvial soils overlying deeper lacustrine clays.
The TSF area generally slopes from south to north at about two percent along the valley floor. Valley wall slopes to the east and west ranging from about 10%
to 15%, and about 5% in the south along the higher valley slopes in the southern portion of the TSF basin.
Vegetation across the site generally consisted
of moderately dense native shrubs and grasses. No surface water, perennial streams, or springs were observed within the TSF footprint or TWRSF areas at the time of the geotechnical field investigations.
15.5.2
Past Studies, Subsurface Investigations, and Civil Design
Several previous studies and investigations have been completed to support various scoping studies and designs of the TSF. Golder Associates USA Inc. (Golder)
utilized information obtained from the following prior studies for this TSF design in conjunction with the FS Project design criteria defined by Paramount and Ausenco:
•
Siting Study Letter Report titled Grassy Mountain Project – Tailings Storage Facility Siting and
Trade-off Study. December 2016 (Golder 2016b). Updated for Consolidated Permit Application in September 2019 (Golder 2019b).
•
Design Report titled Pre-feasibility Design, Tailings Storage Facility for Calico included a geotechnical
subsurface investigation at the proposed TSF site in December 2017 consisting of 15 geotechnical borings and excavating 44 test pits in the project area (Golder 2018b).
•
Design Report titled Detailed Design, Tailings Storage Facility and Waste Rock Dump for Calico (Golder 2019c)
included:
•
March 2019 – six geotechnical boreholes within the TSF area and laboratory testing;
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•
April 2019 – geotechnical tailings testing program; and
•
July 2019 – 11 cone penetration test soundings within TSF area.
•
Design Report titled Detailed Design, Tailings Storage Facility and Temporary Waste Rock Storage Facility
for Calico (Golder 2021d) included a geotechnical subsurface investigation included 16 test pits at the proposed closure cover borrow areas and 2 test pits within the TWRSF footprint.
15.5.3
Design Objectives
The TSF design was developed by Golder using designs and methods that protect against impacts to groundwater in accordance with State and Federal environmental
and dam safety guidelines and regulations. The dam design as presented exceeds the dam safety requirements of OAR 625 Division 20 – Dam Safety for a Low Hazard dam.
In July 2020, the Oregon Water Resources Department (OWRD) issued approval for the TSF based on the November 2019 Revision 0 design confirming the Low Hazard
designation (OWRD 2020). In July 2025, WSP submitted a permit extension request to the OWRD provide approval continuation to the dam safety permit for an additional five years (WSP 2025). OWRD provided email approval extension in July 2025
(OWRD 2025).
15.5.3.1
Basis of Design
The TSF consists of an earth- and rock-fill dam spanning a shallow valley at the north limits of the TSF site to impound tailings to the south. A saddle dam
constructed along the western ridge will be required beginning in Stage 2. The dam will be developed using concepts that will provide a safe and stable dam during all stages of construction, operation, and closure. The impoundment basin will be
lined with multi-layered composite containment system consisting of an enhanced geosynthetic clay liner (GCL), leak detection, and high-density polyethylene (HDPE) geomembrane liner to contain the tailings
solids and fluids. The lining system will extend to the upstream crest of the embankment. Tailings will be transferred to the TSF with an average solids concentration of 42.4%, by weight through a slurry pipeline from the mill.
15.5.3.2
Mill Throughput
Upon completion of plant commissioning, tailings are anticipated to be delivered to the TSF via a slurry pipeline. Total mill throughput for LOM is
approximately 2.4 Mtons.
15.5.3.3
Tailings Density and Storage Capacity
Geotechnical testing and consolidation modelling performed by Golder estimates a tailings settled dry density of 80 lb/ft3. Based on the TSF design, the Stage 3 TSF will provide a total storage capacity of 3.64 Mtons. However, for the LOM, only 2.4 Mtons are planned to be delivered to the TSF, and, therefore, only Stages
1A, 1B, 2, and a portion of Stage 3 will be required for this Study’s LOM plan. The design capacity considerations for each stage are outlined in Table 15-1.
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Table 15-1: Stage Capacity Relationship
Stage
Elevation (ft)
Maximum Tailings
Surface Area
(acres)
Storage Capacity (M tons)
Main Embankment Crest
Maximum Tailings
Surface
Stage
Cumulative
1A
Varies (Min. 3583)
3581
42.0
0.40
0.40
1B
Varies (Min. 3595)
3593
44.7
0.58
0.98
2
Varies (Min. 3609)
3607
59.5
1.06
2.04
3
Varies (Min. 3622)
3620
83.0
1.60
3.64*
*
Additional storage capacity is available with the Stage 3 expansion. During operation, construction of Stage 3
may be optimized for the LOM requirement, resulting in a lower Stage 3 capital construction cost.
15.5.4
TSF Design
15.5.4.1
Embankment Construction
The embankments will be constructed in three primary stages. Stage 1 will be separated into two intermediate stages (Stage 1A and 1B). Stage 2 and Stage 3 will
be constructed as downstream raises along the north and west embankments. The embankments will be constructed of soil and/or rock materials using downstream construction methods. Suitable embankment materials will be generated from the on-site
basalt borrow area and during impoundment grading operations.
The embankments will have a maximum overall upstream slope of 3H:1V, with a downstream
slope of 2.5H:1V. The overall embankment slopes are suitable for long-term geotechnical stability, closure, and meeting Oregon Administrative Rules requirements. The north and west embankments will have a maximum height of 84 feet and 30 feet,
respectively. The crest width of the north embankment will be 50 ft, and the smaller west embankment will have a 30-ft wide crest. The TSF is designed as a “zero discharge” facility to meet OAR requirements. To achieve this, the facility
will be a 100% geomembrane-lined facility with a continuous, engineered lining system extending across the impoundment basin and the upstream slope of the embankments.
Downstream construction will be accomplished by extending new embankment against the existing downstream slope of the previous stage and then raising the
embankment up to the new crest elevation for each stage as shown in Figure 15-3.
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Figure 15-3: TSF Main (North) Embankment Cross-section
Source: Golder, 2021d.
15.5.4.2
Containment and Underdrain System
To achieve “zero discharge” and provide environmental containment as required by OAR, the composite lining system within the impoundment basin will
consist of (from bottom to top) a six-inch to 12-inch thick prepared subgrade, a 300-mil thick enhanced geosynthetic clay liner, 80-mil HDPE geomembrane liner, an 18-inch thick drainage layer, and a six-inch thick filter layer. An underdrain collection system consisting of perforated piping will be located within the drainage layer to promote drainage of the tailings. The upstream slope of the embankments will
use the same composite lining system, but without the overlying piping, drainage and filter layers.
15.5.4.3
Tailings Deposition Management and Return Water
A reclaim pond, located downstream (north) of the TSF, will capture all tailings draindown collected in the underdrain collection system from the tailings. To
achieve “zero discharge” and provide environmental containment as required by the Oregon Administrative Rules, the lining system for the reclaim pond will consist of (from bottom to top): a prepared-in-place subgrade, 60-mil HDPE
secondary geomembrane liner, HDPE geonet, and 80-mil HDPE geomembrane primary liner. The geonet located between the two geomembranes will serve as the leakage collection and recovery system.
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The supernatant pool will be maintained away from the embankments on the eastern side of the facility by
controlled deposition of tailings from spigots installed around the perimeter of the facility. Water separating from the tailings solids after deposition will be managed with two independent return-water systems. One will manage flows collected in
the reclaim pond from the underdrain collection systems and the other will manage water collected in the supernatant pool. The supernatant pool will be managed with a pump installed either on the eastern edge of the facility or on a floating barge
within the pool. Water from both systems will be returned to the mill for use in the process circuit. At all times, process fluid pipelines will be located above secondary containment that consists of either geomembrane liners or reinforced concrete
containment structures.
Precipitation falling on area downgradient of the diversion channels and above geomembrane-lined areas will is captured and
incorporated into the process circuit. Seasonal fluctuations in precipitation and evaporation are accounted for in the process fluid water balance prepared by Golder.
15.5.4.4
Surface Water Management
The TSF will be capable of storing runoff from tributary areas and direct precipitation on the facility resulting from a 500-year, 24-hour storm event, as well
as an allowance for wave run-up due to wind action. Permanent and temporary stormwater diversions will collect and divert a majority of the stormwater runoff around the facility to a natural drainage on the north side of the TSF.
15.5.4.5
Geotechnical Stability
The embankments are designed by Golder to be geotechnically stable during normal operation, and during the design seismic event. For this design, Golder
performed a site-specific seismic and faulting hazard assessment to estimate peak ground motions resulting from various seismic events. The maximum credible earthquake (MCE) was selected as the design seismic event for long-term closure. This
selected design seismic event is suitable for any hazard classification determined by regulatory agencies.
15.5.5
Monitoring
The TSF design was advanced to construction-level to support on-going State and Federal permitting. To support construction-level design and permitting, Golder
prepared a detailed geotechnical monitoring plan that defines the roles and responsibilities of key stakeholders (Owner, operator, engineer) for safe and stable TSF construction and operation. Monitoring will be accomplished through both
measurements of the monitoring points and visual observations of surface conditions.
The geotechnical monitoring plan (Golder 2021d) provides definition
on normal and abnormal operating conditions. A network of monitoring instruments will be installed during each stage of construction to monitor critical geotechnical conditions as they relate to dam stability and environmental containment. Trigger
actions response plans have also been developed by Golder to guide key stakeholders in their response to specific conditions.
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15.5.6
Closure
When mining operations are complete, active tailings deposition from the mill into the TSF will cease. Water collected in the reclaim pond will be recirculated
to the supernatant pool for active water management. Over time, the supernatant pool will evaporate and the underdrain flows reporting from the TSF will reduce as the tailings consolidate and drain.
Under the conceptual closure plan, once the tailings surface no longer has a free water surface and the tailings continue to desiccate and densify, a closure
cover will be constructed over the tailings surface and TSF embankments. The conceptual closure plan recommends that installation of the closure cover is at a point in time where majority of the tailings consolidation has occurred and is not
expected to negatively impact drainage of the closure cover.
The closure cover above the tailings surface will be constructed with the following (bottom
to top):
•
Operational layer of waste rock (if available) or other materials to provide vehicle access (as needed).
•
4 to 12 inches of Liner bedding (if required).
•
60-mil double sided textured linear low-density polyethylene (LLDPE) geomembrane liner.
•
12 inches of non-acid generating granular drainage layer.
•
12 ounce per square yard (oz/sy) non-woven geotextile.
•
12 inches of growth medium, scarified and revegetated.
The TSF embankment closure cover will consist of 12 inches of growth medium placed on the crest and downstream slopes of the TSF embankments. After placement,
the growth medium will be scarified and revegetated.
Closure cover material will be sourced from the Closure Cover Borrow Areas located northwest of the
basalt quarry and southwest of the TSF.
The remaining waste rock (if any) stockpiled on the TWRSF will be removed and placed as an operation layer above
the tailings surface when it is safe to do so. The TWRSF lining system will either be removed or buried upon completion of mining operations. Stormwater falling on the TSF and upgradient catchment areas, below the permanent diversion channels, will
be routed over the covered impoundment surface to a closure drop chute channel located at the eastern abutment of the north embankment. The closure drop chute and impoundment surface swale are designed to safely convey stormwater flows resulting
from a 500-year, 24-hour storm event.
Once tailings draindown flow rates reduce to levels suitable for passive water management (depending on the
long-term passive management system), the reclaim pond will be retrofitted to a geomembrane-lined evaporation pond. With installation of the closure cover and gravity drainage from the underdrain collection system, it is expected that draindown from
the TSF will cease. Once drainage from the TSF has ceased, the evaporation pond will be removed.
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15.6
Closure Cover Borrow Areas
To support final reclamation, closure cover will be sourced from growth media stockpiles generated during construction as well as designated closure cover
borrow areas as presented on Figure 15-2. During initial mine development, and staged construction of the TSF, growth media and topsoil will be stripped and stockpiled in designated locations north of the TSF
and immediately west of the Basalt Borrow Quarry. During reclamation, the growth media stockpiles will be excavated and placed as vegetative closure cover. Once depleted, the Closure Cover Borrow Areas located immediately west of the Basalt Borrow
Quarry and south of the TSF will be developed as additional vegetative closure cover material.
Growth media stockpiles will be constructed with maximum
2.5H:1V side slopes and re-vegetated. The Closure Cover Borrow Areas will be excavated as needed with maximum 2.5H:1V side slopes and the floor of the quarry will be graded to drain to natural drainages. Upon completion of reclamation activities,
the final Closure Cover Borrow Area quarries will be re-vegetated.
15.7
Water Management
15.7.1
Non-Contact Water Management
The following summarizes the results and interpretations for the stormwater diversion channels based on data collected and engineering means and methods
presented in the 2019 Hydrology Analysis and Stormwater Diversion Recommendations for the Process and Portal Pads (Golder, 2019a), 2021 Tailings Storage Facility and Temporary Waste Rock Storage Facility detailed design report (Golder, 2021d) and
2021 stormwater pollution control plan (Golder, 2021a).
The Project site is located approximately 6.5 miles northwest of Lake Owyhee in the semi-arid
plateau of eastern Oregon and local landscape is typical of high mountain desert environment and rangeland. The terrain is gentle to moderate with relatively low relief. Elevation ranges from approximately 4,050 feet above mean sea level at the
southeastern corner of the proposed borrow pit area to 3,330 feet above mean sea level north of the TSF reclaim pond. Drainage at the site is generally to the north in ephemeral natural drainages. No perennial streams or wetlands exist at the
site.
The Project site is divided into three main hydrologic catchment areas. Each catchment area was used to size temporary and permanent diversion
channels that route water around the zero-discharge process areas. The catchment areas are shown on Table 15-3 and defined as:
•
TSF area: All western hydrologic catchment areas draining to the TSF area; 688 acres.
•
Process pad and portal pad area: All interior hydrologic catchment areas draining to the processing area and
portal; 12.4 acres.
•
Site wide area: All eastern hydrologic catchment areas draining to the planned borrow pit area and the catchment
for the existing natural drainage immediately west of the borrow pit; 664 acres.
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The overall Project site catchment area has a total tributary area covering approximately 1,350 acres.
Hydrologic catchments areas were developed based on existing topographic features and identifying areas where calculated peak flows will be required for hydraulic design of drainage improvements.
Figure 15-4: Site-wide Hydrologic Catchment Areas
Source: Golder, 2021a.
Hydrologic and hydraulic analyses were completed with weighted average soil characteristic curve numbers and time of concentrations. This model developed
flows from each sub-basin for the 25- year, 24-hour; 100-year, 24-hour; and the 500-year, 24-hour storm events. The flows were used to design the surface water diversion and contact water collection channels, culverts, and outlet aprons.
The following design storm events and freeboard capacity were applied:
•
Permanent channels: 100-year, 24-hour storm event with freeboard (9 inches), or 500-year, 24-hour storm event
without overtopping.
•
Temporary channels: 25-year, 24-hour storm event with freeboard (9 inches), or 100-year, 24-hour storm event
without overtopping.
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All culverts were designed to only be in place during operation and were therefore designed to convey the
25-year, 24-hour storm event. Channel velocities were reviewed by Golder during hydraulic design of the stormwater diversion channels to determine appropriate channel lining systems for erosion protection. In most areas, unless in permanent
diversion channels, the channels will be either unlined or riprap-lined with variable stone sizes.
In areas where channel velocities exceeded the
reliability limits of a natural soil lining, riprap lining systems will be used. Dissipation aprons will be located at permanent channel discharge points around the TSF where run-off will be discharged into existing natural drainages to encourage a
smooth transition into the existing drainage and minimize erosion to the natural slopes.
Non-contact water runoff is designed to flow into natural
drainages downstream of the site to unnamed tributaries of Negro Rock Canyon that in turn discharges to the lower Malheur River.
15.7.2
Contact Water Management
Meteoric water contacting impacted materials at the TSF and TWRSF will be managed within the TSF process fluid water balance a discussed in
Section 15.5.4.1. Meteoric water contacting process plant and associated infrastructure will be diverted through a network of contact water diversion ditches and channels to a geomembrane-lined contact water pond to be located east of the
process plant.
The process plant contact water pond will be a geomembrane-lined containment pond using a dual containment and leakage collection system.
Figure 15-4 shows the proposed locations of the structures to control contact and non-contact surface water
routing around the process plant site. The process plant contact water pond, designed by Ausenco, will be a geomembrane-lined containment pond using a dual containment and leakage collection system. The containment system consists of (from bottom to
top):
•
prepared subgrade
•
12 inches of soil liner bedding
•
60-mil HDPE geomembrane liner
•
Geonet
•
80-mil HDPE geomembrane liner.
Water entering the process plant containment pond will be used in the process circuit or evaporated.
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Figure 15-5: Process Plant Stormwater Contact and Non-contact
Catchment Areas
Source: Golder, 2019a.
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15.7.3
Site-wide Water Balance
A high-level site-wide water balance was developed based on the following assumptions:
•
Annual average water demands from the process plant mass balance (estimated by Ausenco).
•
Usage of water extracted from dewatering operations in the process circuit and to supply the underground mining
equipment (estimated by Lorax):
•
Low dewatering estimate = 12 gpm
•
Mid-range dewatering estimate = 23 gpm
•
High dewatering estimate = 78 gpm.
•
Water for underground equipment, of about 76 gpm (estimated by MDA) will be sourced from underground dewatering
and raw water production and recirculated as needed.
•
Tailings slurry concentration of 42.4% solids, by weight, during deposition (estimated by Ausenco).
•
Climate conditions based on TSF water balance (estimated by Golder, 2021d).
•
Water collected in the process plant contact water pond will be used in the process circuit or evaporated.
•
Additional raw water will be supplied by the proposed production wells as make-up water.
Water demands will vary seasonally (Table 15-2).
Table 15-2: Annual Average Water Balance
Item
M gallons/year
Demand
Total water for tailings discharge
92.8
Demand total
92.8
Source/supply
Raw water for elution circuit
17.2
Ore feed
3.6
Underground dewatering
12.1
TSF return water
47.5
Plant contact water pond
0.4
Source/supply total
80.7
Make-up water
12.1
Note: Table based on average annual climate and mid-range dewatering estimate.
Water supply from the raw water production wells and mine dewatering is projected to be sufficient to support the FS mine plan requirements and during
seasonal fluctuations. Water demands are expected to increase and decrease seasonally and during periods of extended dry and wet climactic years, respectively. During periods of extended dry conditions, additional make-up water from the production
wells may be required. During extended periods of wet conditions, raw water from the production wells will be reduced as needed. Additionally, if operated within the design parameters, the TSF supernatant pool may be used to provide seasonal buffer
for water demands. On an as needed basis, enhanced evaporation through the use of spray evaporators over the tailings surface during the dry season can be implemented.
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15.8
Built Infrastructure
The built infrastructure requirements are summarized in Table 15-3.
Table 15-3: Built Infrastructure Requirements
Item
Comment
Process plant
Steel-frame and metal clad building with an area of 7,000 ft2. Will include a bridge crane that comes with an electric chain hoist and trolley and control pendant
Process plant control room
Single-level modular steel container, modular building, preassembled. Will include insulated steel doors, windows, operator’s desk, soundproof and dustproof with an area of 135
ft2.
Gold room
Pre-cast masonry building of approximately 1,000 ft2. Will include an electric chain hoist and trolley
Assay laboratory
Single-level steel containers of approximately 2,715 ft2 to be situated adjacent to the process building. Will include sample receiving and preparation, fire assay, weighing room,
wet analytical laboratory, dry instrument room, and utilities and storage modules. Will house the laboratory equipment for assaying, metallurgical, and environmental requirements. Dust-collection equipment will be located external to the laboratory
building. The building will be serviced with power, water, air conditioning and heating, communications, air and mercury scrubbers, and fume hoods.
Process plant workshop and warehouse
Pre-engineered steel-frame and metal clad building of approximately 2,540 ft2. Will be used to perform maintenance for process equipment, as well as for the storage of equipment
spare parts
Administration building
Single level modular wood frame, 80 x 110 ft for a total footprint of approximately 8,800 ft2. Will house the site management team, including general management, commercial and
administration management, engineering, mine operations, senior processing, and maintenance personnel. Will be serviced with power, water, air conditioning and heating, communications.
Contractor office and laydown
Modular trailer with an area of 160 ft2
Truck workshop and warehouse
Pre-engineered steel-frame and metal-clad building with an area of 6,250 ft2. Will be positioned adjacent to the mine-office building. Will be divided into two sections, one for
warehousing spare parts and tool storage and the other for a maintenance workshop. A bridge crane will be included
Vehicle wash-bay
Open-air, 50 x 50-ft concrete slab with a fluid-collection sump and oil-water separator that will be located adjacent to the truck workshop and warehouse. Wash water will be collected in the sump where settling will occur prior to
the water being recirculated back to the wash system. The oil-water separation system will recover hydrocarbons prior to re-use of the wash water. The recovered hydrocarbons will be collected and shipped offsite for disposal in accordance with
applicable environmental regulations.
Security gate house
Pre-assembled wood-frame modular building with an area of 325 ft2. The building will include lift gates and one turnstile. 22,350 ft of security fencing will be installed around
the entire mine site, including the borrow source area. There will be a main gate where the main access road enters the site, and a second gate will be placed at the southern end of the property. The southern access gate is anticipated to remain
locked with access only allowed as needed.
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Item
Comment
Explosives-storage facilities
Will be constructed at the southwest side of the mine area. This location uses a hill as a natural barrier between the explosives-storage facility and other infrastructure. Will consist of a powder magazine in accordance with
current applicable explosives regulations. Dirt berms will be placed around the magazines for additional security. Explosives will be delivered to site by vendors using the main access.
Fuel
Two double-walled steel tanks will be used for diesel storage. The total volume between the two tanks is 8,250 gal. Will be used by the underground equipment. A fuel truck will be used to fuel underground equipment as required and
may be used to fuel surface equipment as needed.
Air
High-pressure compressed air will be provided by one duty screw compressor, one standby screw compressor, and a duty-plant air receiver. Two high-pressure air uses: instrument air and plant air. Instrument air will be dried and then
stored in a dedicated air receiver. Plant air will be fed straight from the plant air receiver without a drying step. Low-pressure air for pre-aeration tank air requirements will be provided by two duty and one standby rotary air
compressor.
Communications
On-site communications will comprise inter-connected mobile and fixed systems, including a land-line telephone network, portable two-way radios, and internet. Access for internet and corporate network connection will be made via
satellite connections. Underground communication with the surface will be via a leaky-feeder system
15.9
Camps and Accommodation
No accommodations camps are envisaged. Personnel are expected to reside in nearby communities such as Vale, OR, and Boise, ID.
15.10
Power and Electrical
The power supply will initially be from diesel power generators located on site. The diesel power generators will be used for approximately one year during
initial construction and the initial mining of the decline. During the construction period a new power line would be constructed along the main access road to site. Once construction of the primary power lines is completed, the generators will
remain on site for backup in case of power outages.
The construction of line power will deliver approximately 5.3 MW of power to site and will require a
23-mi distribution circuit, a new 69/34.5 kV to 14 MV transformer, and a new 34.5kV 67-amp regulator. The power line would be constructed from the Hope Substation near Vale to the mine site along the main access road.
The plant power distribution from the powerhouse will be via overhead powerlines. The distribution voltage to the local electrical rooms will be 14.4 kV.
There will be a combination control room and motor-control-center room. This room will be pre-fabricated and loaded with electrical equipment prior to delivery to site. The power distribution from the electrical rooms will be 480 V.
The total connected load for the process plant is expected to be 4.8 MW, with an average power draw of 3.6 MW. Power requirements for the underground mine are
discussed in Section 13.12.3.
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16
MARKET STUDIES
16.1
Introduction
The proposed Grassy Mountain operation will produce doré bars on site, which will then be shipped to an out of state refinery. There is currently no
contract in place with any refinery or buyer for the doré.
16.2
Market Studies
No market studies have been completed. Gold and silver are freely-traded commodities. The doré that will be produced by the mine is considered to be
readily marketable with no deleterious/penalty elements. Although mercury is present in the ore, a retort and recovery system has been included to maintain doré quality.
The doré bars are forecast to have a variable gold and silver content with an expected gold to silver ratio of 44–49% gold to 51–56%
silver.
The economic analysis in Section 19 assumes that Paramount will be paid 99.9% of the gold value and 99.5% of the silver value by a refinery
(Table 16-1). Ausenco conducted a benchmarking analysis that estimated refining charges of $5/oz payable gold and $0.50/oz payable silver, totaling direct refining costs of $2.0 million over the LOM.
Table 16-1: Estimated Payability and Refining Costs
Description
Units
Value
Proportion of Au
Percent by weight content in doré bars
46
Proportion of Ag
Percent by weight content in doré bars
54
Payable gold
%
99.9
Payable silver
%
99.5
Refining and sales charges Au
$/oz
5.00
Refining and sales charges Ag
$/oz
0.50
16.3
Metal Pricing and Projections
16.3.1
Economic Analysis
Project economics were estimated based on long-term flat metal prices of $3,600/oz Au, and $48.00/oz Ag, which are based on consensus forecasts from various
financial institutions.
The QP notes that the pricing used in the cash flow analysis is reasonably aligned with various long-term forward-looking
estimates from major international banks.
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Metal prices are defined daily by several commodity markets via contract trading. Some of these markets are
the London Metal Exchange (LME), the Commodity Exchange (COMEX), the New York Mercantile Exchange (NYMEX), the Chicago Mercantile Exchange (CME), and the London Bullion Market Association (LBMA).
Some exchanges define prices on the spot while others, like the LBMA, set prices based on offer and demand in the morning (AM) and in the afternoon (PM).
Prices are set each day, except weekends and holidays. The gold and silver PM contract values are used to define future and expected gold prices.
Given
the volatility of the metal prices, medium term average gold and silver prices are often used to inform the basis metal prices for economic analysis. The tables below show the average prices calculated for each time frame based on the PM daily gold
prices set at the (LBMA).
Table 16-2: Gold Price Average (LBMA PM), $/oz
Date
High (1-yr)
Low (1-yr)
1-yr Avg
2-Yr Avg
3-yr Avg
May 26 ‘26
5,297.87
3,273.17
4,152.49
3,440.98
2,976.99
Table 16-3: Silver Price Average (LBMA PM), $/oz
Date
High (1-yr)
Low (1-yr)
1-yr Avg
2-Yr Avg
3-yr Avg
May 26 ‘26
118.45
32.90
59.69
45.45
38.37
Based on long-term analysis and industry consensus, median analyst metal prices were selected as representative for the
economic analysis. The gold and silver prices used in the economic analysis are:
•
Gold price: $3,600/oz
•
Silver price: $48.00/oz
Metal prices were kept constant throughout the life of the Project.
16.3.2
Metal Pricing Forecasts
Paramount expects to commence production at Grassy Mountain within four years. Mid-term gold price forecasts by several institutions are listed in Table 16-4, seen to be in a similar range as those applied in the base case scenario in the FS.
Table 16-4: Mid-term gold price estimate by year from various organizations
Year
Units
2026
2027
2028
2029
Long-Term
Max
$
/oz Au
6,000
6,500
6,000
5,500
4,909
Min
$
/oz Au
3,600
3,600
3,600
3,022
2,500
Average
$
/oz Au
4,760
4,799
4,372
4,036
3,603
Median
$
/oz Au
4,713
4,663
4,250
3,825
3,600
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16.4
Contracts
Paramount has no current contracts for property development, mining, concentrating, smelting, refining, transportation, handling, sales and hedging, forward
sales contracts or arrangements.
It is expected that when any such contracts are negotiated, they would be within industry norms for projects in similar
settings in the U.S.
16.5
QP Comment
The doré that will be produced by the planned operation is readily marketable with no deleterious/penalty elements.
Metal pricing used in the economic analysis in Section 19 are based long-term flat prices of $3,600/oz Au, and $48.00/oz Ag, which are based on consensus
forecasts from various financial institutions.
The QP has reviewed commodity pricing assumptions, marketing assumptions, and the potential major
contracts that may be entered into and considers the information acceptable for use in estimating Mineral Resources, Mineral Reserves, and in the economic analysis that supports the FS. The QP notes that the pricing used in the cash flow analysis is
reasonably aligned with various long-term forward-looking estimates from major international banks.
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17
ENVIRONMENTAL STUDIES, PERMITTING, PLANS, NEGOTIATIONS OR AGREEMENTS WITH LOCAL INDIVIDUALS OR GROUPS
17.1
Introduction
Permitting activities began in 2012 with engagement with the state and federal agencies and collection of baseline data. The draft Consolidated Permit
Application (CPA) was submitted to the Oregon Department of Geology and Mineral Industries (DOGAMI) in 2019 for review and comment by state agencies which were received by Calico and integrated into the final CPA. In December 2021, Calico submitted
the final CPA to DOGAMI. Calico and DOGAMI have been working together as the draft permits have been developed and are in the process of being finalized. The package of draft permits was issued for public review on December 8, 2025. Final
permits are anticipated to be issued by all required state agencies in the second half of 2026.
In December 2021, Calico submitted a Plan of Operation
(PoO) to the BLM. The draft Environmental Impact Statement (EIS) was published for public comment on August 8, 2025 and the final EIS and record of decision was published on January 29, 2026. This record of decision provides federal
authorization for the PoO following posting of a reclamation bond.
The mine plan includes a total of approximately 490 acres of proposed surface
disturbance including approximately 470 acres of disturbance occurring on public land (Table 17-1).
Table 17-1: Surface Disturbance for the Proposed Project
Component
Public Acres
Private Acres
Total Acres
Underground Mine
0.5
6.2
6.7
TSF
99.8
0.0
99.8
TWRSF
5.7
0.0
5.7
Process Plant1
2.5
0.0
2.5
Infrastructure & Ancillary
Facilities2
17.8
0.0
17.8
Roads
31.6
3.3
34.9
Yards & Laydown Areas
9.9
0.1
10.0
Growth Media Stockpiles
7.7
0.0
7.7
Water Supply3
7.9
0.0
7.9
Power Supply4
61.1
0.0
61.1
Stormwater Diversion Channels
11.6
0.2
11.8
Quarry
48.2
0.0
48.2
Reclamation Borrow Areas5
55.9
0.0
55.9
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Component
Public Acres
Private Acres
Total Acres
Monitoring
0.0
0.0
0.0
Exploration6
10.0
0.0
10.0
Disturbed Areas7
98.6
9.1
107.8
Total
469.0
18.9
487.9
1.
Includes the mill, refining plant, administrative building, parking lot, security building, mining contractor
yard, reagent storage, assay laboratory, and substation.
2.
Includes the perimeter fence at 22,176 ft with a 20-ft construction disturbance width.
3.
Includes the water supply pipeline at 16,164 ft with a 20-ft construction disturbance width and well
locations each at 0.25 acre.
4.
Includes 20-ft area of disturbance for the 25.2 miles of new powerline.
5.
The area of disturbance for the Reclamation Borrow Area is the maximum area of disturbance.
6.
The actual location of the exploration activities within the Project Area is currently unknown and is assumed
to be equally on public and private lands. Annual exploration work plans will be submitted and reviewed by BLM and DOGAMI as defined at 43 CFR 3809.0-5.
7.
Disturbed Area is a 50-ft buffer on the mining facilities excluding the Reclamation Borrow Areas.
Table 17-2: Permitting
Permit/Approval
Granting Agency
Permit Purpose
Plan of Operations/EIS Record of Decision
BLM
Prevent unnecessary or undue degradation associated with Plan of Operations, EIS to disclose and evaluate environmental impacts and project alternatives. An EIS has been developed to analyze impacts of this Plan.
Oregon Department of Environmental Quality (ODEQ) Water Pollution Control Facility Permit and Water Pollution Control Facility-Individual Onsite system
ODEQ
Prevent degradation of waters of the state from mining, establishes minimum facility design and containment requirements. Regulates onsite septic system.
Standard Air Contaminant Discharge Permit
ODEQ
Regulates project air emissions from stationary and fugitive sources.
General Discharge Permit (Stormwater)
ODEQ
Protect waters of the state.
Oregon Water Resources Department (OWRD) Water Rights Amendment, Permit to Appropriate Water
OWRD
Water appropriation.
Public Drinking Water System (Non-Transient Non-Community Water System)
Oregon Health Authority
Regulates drinking water treatment systems.
OWRD Dam Safety Permit
OWRD
Design and construction of embankments 10 ft or higher and store at least 9.2 acre ft of water.
Malheur County Land Use Compatibility Statement (LUCS)
Malheur County
Permitting or approval activities that affect land use are required by Oregon law to be consistent with local comprehensive plans and have a process for determining consistency.
Explosives Permit
United States Department of the Treasury, Bureau of Alcohol, Tobacco, Firearms, and Explosives
Storage and use of explosives.
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Permit/Approval
Granting Agency
Permit Purpose
Hazardous Waste Identification Number
United States Environmental Protection Agency
Registration as a conditionally exempt small quantity generator of wastes regulated as hazardous.
Aggregate Operating Permit Application
DOGAMI
Operation and closure of the Basalt Quarry.
Chemical Process Mines Permit (Division 37)
DOGAMI
Operation and closure of the Project.
Chemical Mining Permit (Division 43)
ODEQ
Operation and closure of the Project.
2920 Permit – Leases, Permits and Easements*
BLM
Allow for the access road improvements and power line installation on property controlled by others
Note: * 2920 Permit required for a portion of Dripping Springs Road improvement.
17.2
Permit History
Permitting activities for the Grassy Mountain Project have spanned 30 years and includes multiple environmental permits for the purposes of exploration and
investigation to support the development of the CPA and PoO. During the late 1980s Atlas collected geologic, mine engineering, civil engineering, and environmental baseline data to support a feasibility study that was completed in 1990. During 2012
to 2016, Calico began the permitting process for an underground-mining operation at Grassy Mountain. Since the acquisition of Calico by Paramount in 2016, the permitting process has continued with DOGAMI, Malheur County, and the BLM including
submittals of the PoO and CPA in December 2021 and the issuance of a record of decision by the BLM in January 2026.
17.3
Project Permits
There is a valid exploration permit with the DOGAMI and the BLM although exploration activities have concluded.
The Project will require a PoO and numerous state and local permits to construct, operate, and close presented in
Table 17-2.
Since the acquisition of Calico by Paramount in 2016, the permitting process has continued with
DOGAMI, Malheur County, and the BLM including submittals of the PoO and CPA in December 2021. The BLM issued the final EIS and record of decision in January 2026. Malheur County issued a CUP for the Private Land portion of the Grassy Mountain
Project in May of 2019. Draft state permits were issued for public comment and review in December 2025 and state agencies are currently in the process of finalizing permits. State permits will be issued at one time and are anticipated to be issued
in the third quarter of 2026.
17.4
State of Oregon Permit Processing
Calico entered into a Memorandum of Understanding for Cost Recovery (MOU) with the Oregon DOGAMI on November 3, 2014. A new MOU was signed when the
initial CPA CPA was submitted in November 2019. The MOU provides a mechanism whereby Calico, as the Project proponent, agrees to reimburse DOGAMI and other primary State agencies for their involvement in processing the CPA for the Grassy Mountain
Project when those fees exceed their permit fees. In addition, DOGAMI hired consulting firms to provide expertise that is not available from the staff that the various agencies are involved with during the permitting process.
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The key components of the permitting program with the State of Oregon are as follows:
•
Environmental baseline studies for all resource categories described in Chapter 632, Division 37 Chemical Process
Mining Rules.
•
Meeting all requirements of Division 37 Rules which include, but are not limited to:
•
Preparation of a Consolidated Permit Application (CPA)
•
Obtaining all necessary federal, state, and local permits and authorizations
•
Satisfying any potentially applicable environmental evaluation requirements.
•
Implementing a pro-active community involvement and consultation process including:
•
Local hire preference
•
Local contracting and purchase where practicable
•
Mine worker job training to provide an experienced workforce.
A key authorization permit which will be required is the permit for Chemical Processing Mining, as required under Chapter 632, Division 37, 1991 Oregon Laws
(§632-037-0005). The Consolidated Permit also requires approval by ODEQ under Division 43, Chemical Mining Rules (OAR 430-043-000), which address other environmental stipulations. “Chemical Process Mining” means a mining and
processing operation for metal-bearing ores that uses chemicals to dissolve metals from ore. The Calico processing facility will employ cyanide in the metallurgical process. The Division 37 Rules provide a well-defined regulatory pathway with
definitive permitting requirements and timelines.
Calico has filed multiple Notices of Intent (NOIs) under Division 37, which initiate the State
permitting process and begin baseline data collection. The reason for the multiple NOIs is that the scope of the operation, as well as the configuration of the Project area have changed. Each change requires the submittal of a new NOI and a
re-initiation of the permitting process. In addition, the initial NOI filing was done to initiate the agency Division 37 permit process and provide for public notice that the Project is proceeding into the permitting phase. As part of initiating the
public notification, an interagency “Technical Review Team” (TRT) was organized to provide interdisciplinary review of technical permitting issues for the State Consolidated Permitting Process. This TRT has met numerous times and
accepted the NOIs.
In addition, DOGAMI administrators and the TRT have reviewed and approved the “Calico Resources Environmental Baseline Work
Plans Grassy Mountain Mine Project”, which was filed on May 17, 2017. In July 2017 a “Notice of Prospective Applicant’s Readiness to Collect Baseline Data” was issued to Calico by DOGAMI. The environmental baseline data
collection and reporting program is now complete. All Baseline Data Reports (BDRs) submitted by Calico have been accepted by the TRT. The three most current approvals were for the Wildlife Resources BDR accepted in March 2021, the Geochemistry BDR
accepted in June 2022 and the Groundwater BDR accepted in June 2022. The Cultural Resources BDR is confidential and relies on the SHPO to provide a recommendation to the TRT.
Calico prepared and submitted the Division 37 CPA for the Grassy Mountain Gold Mine in November 2019. This single application, as required under Oregon laws,
included the following elements:
•
General information
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•
Existing environment-baseline data
•
Operating plan
•
Reclamation and closure plan
•
Alternatives analysis.
DOGAMI finished their completeness review with input from the TRT. DOGAMI determined that additional information was necessary before further processing of
the application. Comments were received in February 2020. Calico submitted the Revised CPA package to DOGAMI in December 2021. Calico has been working with DOGAMI since the submittal responding to questions and comments. The air application was
submitted separately in August 2022.
A Notice to Proceed with the preparation of draft permits was issued by DOGAMI in November 2023. This notice
included a directive by DOGAMI to use the third-party contractor to prepare an Environmental Evaluation (EE), which was accepted by the TRT in October 2024. This EE is not a Federal NEPA requirement. It is a State of Oregon requirement which
includes:
•
Impact analysis
•
Cumulative impact analysis
•
Alternatives analysis (OAR 632-037-0085).
Concurrent with this assessment, DOGAMI utilized the contractor to prepare a Socioeconomic Analysis. This analysis identified major and reasonably foreseeable
socioeconomic impacts on individuals and communities located in the vicinity of the proposed mine. In particular, the analysis will describe impacts on population, economics, infrastructure, and fiscal structure (OAR 632-037-0090).
This process for permit review and approval involved a consolidated public hearing on all draft permits, and the draft operating permit which was conducted on
January 29, 2026 in Vale, Oregon. Other applicable State of Oregon and Federal permits may include, but are not limited to the following:
•
Permits to appropriate groundwater or surface water, or to store water in an impoundment (ORS 537.130, ORS
537.400, and ORS 540.350)
•
Water Pollution Control Facility (ORS 468B.050)
•
Storm Water Pollution Prevention Plan (EPA)
•
Air Quality Permits (ORS 468A.040)
•
Solid Waste Disposal Permit (ORS 459.205)
•
Permit for Placing Explosives (ORS 509.140)
•
Hazardous Waste Storage Permit (OAR 340-102-0010)
•
Land Use Permit (OAR Chapter 632, Division 001)
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•
Any other State permits, if applicable and required under Division 37.
A Project Coordinating Committee (PCC) was also formed for the purpose of sharing information; further coordinating the Federal, State, and local permitting
requirements; optimizing communication; facilitating the regulatory process; and avoiding duplicative effort. The PCC has met formally and conducted a series of public meetings in Ontario and Bend, Oregon. These meetings were attended by agencies,
public officials, Project supporters, and non-governmental organizations (NGOs).
Division 37 mandates DOGAMI to manage and facilitate the regulatory
permitting process. It requires that a series of public meetings are held, to be coordinated by DOGAMI or its contractor. This committee is charged with gathering comments from the public regarding Project specifics. DOGAMI acts as the facilitating
State agency and State clearinghouse for the mine permitting process. It is the applicant’s responsibility to secure other needed State permits such as air pollution control, storm water pollution prevention plan, and land use permits as may
be required. However, the Division 37 process is designed to promote a consolidated permitting pathway.
DOGAMI coordinates with the other agencies to
avoid duplication on the part of the applicants and related agency requests. The agency is also responsible for reviewing mine operating plans and issuing reclamation permits. It establishes reclamation bond amounts for the Project, working closely
with Calico.
The basic information for a Division 37 application involves:
•
Determining existing environmental baseline conditions
•
Providing an operating plan (mine plan and reclamation/closure plan)
•
Providing an alternatives analysis
•
Providing an environmental evaluation
•
Providing a socio-economic impact analysis
•
Developing a plan to minimize pollution and erosion
•
Protecting fish and wildlife during operations and closure (fish and wildlife standards)
•
Providing a water balance
•
Establishing financial assurance requirements
•
Inclusion of all other State, Federal, and local permit applications required under Division 37.
Draft state permits are anticipated to be issued in the second half of 2026.
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17.4.1
Federal Plan of Operations Processing
A PoO must be submitted to the BLM for any surface disturbance in excess of five acres. A PoO describes the operational procedures for the construction,
operation, and closure of a project. The PoO must also include a waste rock management plan, quality assurance plan, a storm water plan, a spill prevention plan, reclamation plan and cost estimate, a monitoring plan, and an interim management plan.
The content of the PoO is based on the mine plan design and the data gathered as part of the environmental baseline studies. The PoO includes all mine and processing design information and mining methods. The BLM determines the completeness of the
PoO and, when the completeness letter is submitted to the proponent, the NEPA process begins.
The initial submittal of the Grassy Mountain PoO was in
September 2017. A revised PoO was submitted to the BLM in February 2020. The BLM determined the PoO submitted in February 2020 was not complete and requested additional details. Calico submitted a new PoO in December 2021 and that the BLM determined
was incomplete and provided comments to Calico in March 2022. Calico responded to the comments in July 2022 and received further input from the BLM in September 2022. The final PoO will be submitted to the BLM in October 2022 and based on input
received from the BLM, acceptance of the PoO triggering the NEPA process.
17.4.1.1
National Environmental Policy Act
The NEPA process is triggered by a Federal action. In this case, the issuance of a completeness letter for the PoO triggered the Federal action. The BLM
determined that the NEPA review process for this Project was an EIS.
The EIS process was conducted in accordance with NEPA regulations (40 CFR 1500 et.
Seq.), BLM guidelines for implementing the NEPA in BLM Handbook H-1790-1 (updated January 2008), and BLM Washington Office Bulletin 94-310. The intent of the EIS is to assess the direct, indirect, residual, and cumulative effects of a project and to
determine the significance of those effects. Scoping is conducted by the BLM and includes a determination of the environmental resources to be analyzed in the EIS, as well as the degree of analysis for each environmental resource. The scope of the
cumulative analysis is also addressed during the scoping process. Following scoping and baseline information collection, a draft EIS is prepared and submitted to the public for review which occurred on August 8, 2025 followed by a public
meeting held in Vale, Oregon on August 28, 2025. Comments received from the public were incorporated into the final EIS, which is in turn updated by the BLM prior to the issuance of a record of decision. the final EIS and record of decision
were issued on January 29, 2026 completing the federal permitting process.
17.4.2
Malheur County Permit Processing
Malheur County requires the authorization of a CUP for the Private Land part of the Grassy Mountain Project. Calico obtained the CUP in May of 2019.
Additionally, building permits from the Malheur County will also be required to address plumbing, electrical, and structural design.
17.5
Environmental Study Results and Known Issues
17.5.1
Baseline Studies
Paramount has been conducting baseline data collection for over ten years for environmental studies required to support the State and Federal permitting
process. Results indicate limited biological and cultural issues, air quality impacts appear to be within State of Oregon standards, traffic and noise issues are present but at low levels, and socioeconomic impacts are positive. The result of the
geochemical characterization identified that the geochemistry of the ore and waste rock provide for a possible source of future environmental issues as the Grassy Mountain Project is developed.
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Data produced during the baseline and geochemical studies were used in the Project design process, including
the design and operation of the TSF and handling and use of waste rock as cemented backfill material, specifically considering environmental impacts. As outlined in Section 15, the design of the TSF and the waste rock management plan used the
results of this geochemical characterization work.
The following baseline studies have been submitted to the BLM and DOGAMI as part of the permitting
process:
•
Air Quality Resources Baseline Report
•
Aquatic Resources Baseline Report
•
Areas of Critical Environmental Concern Research Natural Areas Baseline Report
•
A Cultural Resource Inventory of 830 Acres for the Grassy Mountain Mine Project (withheld from public review)
•
Environmental Justice Baseline Report
•
Baseline Geochemical Characterization Report
•
Geology and Soils Baseline Report
•
Grazing Management Baseline Report
•
Grassy Mountain Gold Project Baseline Groundwater Reports
•
Land Use Baseline Report
•
Noise Baseline Report
•
Oregon Natural Heritage Resources Baseline Report
•
Outstanding Natural Areas Baseline Report
•
Recreation Baseline Report
•
Socioeconomics Baseline Report
•
Surface Water Baseline Report
•
Terrestrial Vegetation Baseline Report
•
Transportation Baseline Report
•
Transportation Baseline Traffic
•
Transportation Baseline Trip Generation
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•
Visual Resources Baseline Report
•
Wetland Delineation Report
•
Wild, Scenic, or Recreational Rivers Baseline Report
•
Wildlife Resources Baseline Report
All BDR submitted by Calico have been accepted. The Cultural BDR is handled confidentially and separately by the BLM. The SHPO is expected to make a
recommendation to the TRT; the TRT will not review the report itself, nor will it be available for public comment.
17.5.2
Geochemical Characterization and Groundwater Studies
The geochemical characterization and groundwater studies are interrelated studies with both focused on predicting the potential for acid rock drainage on the
surface and in groundwater primarily due to the storage of tailings and the storage and use of waste rock as backfill. Paramount, DOGAMI, and the BLM have worked together to ensure the baseline reports including geochemical and hydrogeological
characterization and modeling is sufficient for the PoO and CPA to be accepted and move forward in the permitting process. The final reports were submitted to DOGAMI and BLM in 2022.
SRK Consulting U.S., Inc. (SRK) completed the baseline geochemical characterization study for the Grassy Mountain Project in 2022. The purpose of the baseline
geochemical characterization program was to provide a prediction of the potential geochemical reactivity and chemical stability of mine waste that will be produced by the Grassy Mountain Project. The results of the geochemical characterization
program assisted in determining the potential for acid rock drainage (ARD) and metal leaching (ML) associated with the Grassy Mountain Project. Data produced during this study were used in the Grassy design process and as an operational tool for
identifying material types that require special handling during operations. As outlined in Section 15 of the Report, the design of the TSF and the waste rock management plan used the results of this geochemical characterization work.
The Grassy Mountain Project waste rock shows variable geochemical behavior and each material type has a wide range of sulfide content and predicted acid
generation from the static test results. Overall, the waste rock has very limited acid neutralizing capacity due to the low inorganic carbon content and as such the predicted acid generating potential is strongly related to sulfide content. The
characterization results for the ore grade material are comparable to the waste rock material.
Based on the acid–base accounting (ABA) and net-acid
generating (NAG) results, six out of the 104 waste rock and ore samples contain greater than 0.5% sulfide sulfur indicating a higher potential for acid generation. The remaining samples have an uncertain potential for acid generation with
net-neutralizing potential (NNP) values between -20 and 20 kg CaCO3 eq/ton. The NAG results are consistent with the ABA data and show samples with sulfide sulfur greater than 0.5 wt% are
predicted to have a higher capacity for acid generation with NAG values greater than 20 kg H2SO4 eq/ton. Samples with
sulfide sulfur content between 0.05 and 0.5 wt% show a low to moderate potential for acid generation with NAG values between 1 and 20 kg
H2SO4 eq/ton.
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Based on a meteoric water mobility procedure test, the majority of the samples have neutral to alkaline paste
pH values (pH 6–8), indicating minimal readily-soluble acid sulfate salts from prior oxidation of the core material. The exceptions are a few samples of mudstone and siltstone with the highest sulfide sulfur content that generated acidic
leachate. Constituents above Oregon groundwater quality guidelines under the low pH conditions include sulfate, arsenic, cadmium, chromium, copper, fluoride, iron, manganese, selenium and zinc. For samples with neutral pH (i.e., pH >7) all
constituents were below the Oregon groundwater quality guidelines.
Eight of the 10 humidity cell tests generated acidic leachate throughout the test and
indicate that samples with an uncertain potential for acid generation from the ABA will generate acid under long term weathering conditions. The only two samples that maintained neutral conditions during the humidity cell test program consisted of
sinter material. All other material types are considered to be acid generating including the sandstone, siltstone and mudstone. A comparison of the HCT leachate chemistry to Oregon groundwater quality guidelines indicates the mudstone (HC-3 and
HC-4) had the greatest number of parameters that exceeded guidelines and the sinter cells (HC-8 and HC-9) had the least. Most cells that developed acidic conditions leached copper, iron, manganese, arsenic and sulfate at concentrations greater than
the guidelines, indicating these elements are mobile under acidic pH conditions. Other constituents that were leached above Oregon groundwater quality guidelines during the first few weeks of the test include cadmium, chromium, copper, fluoride,
lead, selenium, silver and zinc.
17.6
Waste Disposal, Monitoring, Water Management
Waste rock characterization has been conducted and results indicate that the waste rock and ore are generally reactive, acid generating, and have the potential
to leach metals (refer to Section 17.4). As a result, waste rock and tailings management have been and will remain key issues in the permitting of the mining operation. The TSF design, as described in Section 15, was developed to mitigate
the risk of groundwater impacts due to tailings storage and includes drainage layer for solution capture and repurposing, a dual liner, and leak detection. The waste rock generated during the operation will be temporarily stored on a dual lined
facility prior to utilization as cement rock fill (CRF), as described in Section 15.
Paramount has developed and submitted to BLM and DOGAMI for
approval, the following monitoring and management plans associated with waste disposal:
•
Stormwater Management Plan
•
Waste Management Plan
•
Groundwater and Facilities Monitoring Plan
•
Cyanide Management Plan
•
Petroleum-Contaminated Soil Management Plan
•
Tailings Chemical Monitoring Plan
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17.7
Social and Community Issues
Social and community impacts have been considered and evaluated for the PoO in accordance with the NEPA and other Federal laws, and the State of Oregon
Socioeconomic Analysis. Potentially affected Native American tribes, tribal organizations and/or individuals were consulted during the preparation of the PoO and consultation continues to advise on the project that may have an effect on cultural
sites, resources, and traditional activities.
The most recent planning by Malheur County, Oregon, were considered during the preparation of PoO and CPA.
Potential community impacts to existing population and demographics, income, employment, economy, public finance, housing, community facilities and community services will be evaluated for potential impacts as part of the State of Oregon and the
NEPA process.
There are no known social or community issues that would have a material impact on the Project’s ability to extract Mineral Resources
and Mineral Reserves. Identified socioeconomic issues (employment, payroll, services and supply purchases, and State and local tax payments) are anticipated to be positive through the creation of direct, indirect and induced jobs.
Paramount plans to implement a proactive community involvement and consultation process including 1) local-hire preference; 2) local contracting and
purchasing where practicable; and 3) mine-worker job training to provide an experienced work force. Mining and milling jobs are expected to be sourced to local communities where possible, with limited relocation to supply the expertise reinforcing
the local skillsets.
As a commitment to the local community, Paramount has conducted site tours and discussions with the state and local senators,
representatives, regulators and the local school high school regarding the project. Paramount also has plans to further partnerships with local community colleges and vocational schools whereby “mining expertise” can be developed through
partnership curriculums. These partnerships are likely to include Treasure Valley Community College in Ontario, Eastern Oregon University in LaGrande, and College of Western Idaho in Boise. Paramount will coordinate with Eastern Oregon University to
develop and provide the MSHA safety training program.
17.8
Closure
A closure plan and RCE were submitted to the BLM and DOGAMI as part of PoO and CPA, respectively. The proposed reclamation approach for the Project includes
sealing the mine portal, lining, capping, and revegetating the TSF supported by temporary active solution management followed by passive solution management (evaporation) as the TSF drains down, the removal and offsite disposal of the temporary
waste rock storage facility liner, process plant and other infrastructure, the demolition and offsite disposal of the powerline and associated infrastructure, and in general the grading, capping, and revegetation of disturbed areas. This approach
will result in two post-reclamation landforms, the TSF and the quarry, and is anticipated to be completed within five years of ceasing operation. Post-reclamation monitoring, including groundwater and stormwater quality and revegetation success, is
proposed to meet Federal and State requirements and guidance and will be continue for up to 30 years following reclamation.
The RCE was developed using
the Nevada Standardized Reclamation Cost Estimator (SRCE Version 2.0) and includes direct and indirect costs, contingency, and post-reclamation monitoring assuming third-party costs. The RCE was updated in February 2026 to account for current unit
rates and in response to input from DOGAMI and BLM during the permitting process. The reclamation surety associated with the proposed reclamation plan is $21,086,123 including indirect costs such as contingency, contractor management and contractor
profit. The BLM and State of Oregon are in negotiations to establish an MOU allowing the State of Oregon to hold the bond and oversee the reclamation activities.
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17.9
Environmental and Permitting Risks and Opportunities
As with almost all mining projects, there are inherent risks and opportunities related to the final outcome of the Project. Most of these risks related to
environmental and permitting are based on uncertainty of the permitting program, and timing to obtain all necessary permits and authorizations. Other risks can involve new regulations, the modifications of environmental standards like air or water
quality, and legal challenges; however, the Project has limited applicable environmental standards as it relates to water quality (groundwater and surface water).
To facilitate Project permitting and development for the FS and permitting programs, and to design a sustainable project and reduce environmental risks,
Paramount adopted the following environmental principles for the Project:
•
Confirm the presence of potential threatened and endangered or sensitive amphibians, wildlife, or plant species
at the site.
•
Reduce the area of disturbance where possible by utilizing existing infrastructure and re-use of waste rock as
backfill.
•
Reduce environmental impacts such as emissions, noise and vibration, water consumption, etc. through operational
controls such as limiting traffic to and from the site and the re-use of water from the underground and TSF.
•
Protect local surface and ground water quality and quantity by applying best management practices and evaluating
and implementing new practices as they are identified.
•
Effectively manage all related mine waste including lining the TSF and use of waste rock underground as backfill.
•
Reduce the carbon footprint for the Project by processing the gold concentrate on site.
•
Conduct environmental monitoring to ensure compliance with all applicable State, Federal, and local laws,
regulations, and ordinances.
•
Transport all fuel to the mining operation according to accepted transport and spill prevention and response
standard operating procedures developed specifically for the Project.
•
Integrate pro-active wildlife habitat mitigation and enhancement proposals with an environmentally responsible
reclamation plan.
•
Provide adequate financial assurance for implementing an effective reclamation plan to ensure long-term
protection and rehabilitation of the mine site.
•
Implement a responsible community and statewide public affairs program to further open communications, maximize
local job opportunities and involvement, and meet environmental justice requirements for the Grassy Mountain Mine Project.
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Collectively, these objectives or environmental principles will guide Project development. They will also
serve to reduce risk and enhance related Project opportunities.
17.10
Qualified Person’s Opinion
The final EIS and record of decision were issued in January 2026 providing federal authorization for the PoO to progress into construction, operation and
closure. State permits authorizing the mine plan to progress are expected to be provided in the second half of 2026. Paramount’s engagement with the local, state, and federal regulatory agencies as well as the local community and tribal
engagement has been frequent resulting in a supportive local community and strong working relationship with the regulatory agencies.
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18
CAPITAL AND OPERATING COSTS
18.1
Capital Cost Estimate
18.1.1
Introduction
The capital cost estimate was developed with an accuracy of ±15% using the AACE Class 3 estimate standards, and includes the cost to complete the
design, procurement, construction and commissioning of all the identified facilities.
The entities involved in the estimate and their specific areas of
input are summarized in Table 18-1.
Table
18-1: Capital Cost Estimate Input Areas
Company Responsible
Area
Item
Ausenco
Site development & earthworks
•
Internal roads
•
Catchment pond
•
Diversion ditches from process plant to
pond
•
Crusher ROM pad
•
Plant site bulk earthworks
•
On-site infrastructure bulk earthworks
Crushing & material handling
•
Primary crushing
•
Secondary crushing
•
Fine ore bin
Process plant
•
Grinding and classification
•
Carbon-in-leach
•
Cyanide detox
•
Carbon elution and gold room
•
Reagents
•
Process utilities (process plant building, water systems, plant & instrument air, process control system)
Tailings management & waste rock
•
Tailings & reclaim water pipelines
On-site infrastructure & utilities
•
Power distribution (power distribution & supply, electrical rooms, control
rooms)
•
Water supply & distribution
•
Waste management (water treatment plant (grey
water))
•
Ancillary buildings (mine dry & office, mine maintenance/warehouse, underground truck shop, plant maintenance/warehouse, assay
laboratory)
•
Surface mobile equipment (surface mobile equipment &
facilities)
•
Bulk fuel storage &
distribution
•
Information technology and communications
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Company Responsible
Area
Item
RESPEC
Mining pre-stripping
•
Portal construction
•
Portal laydown
Mine development
•
Decline
•
Level station
•
Level access
•
Underground sump
•
Underground stockpiles
•
Underground power stations
•
Underground truck loading bays
•
Ventilation infrastructure (ventilation bays, raises)
Underground mine equipment
•
Surface and Underground mobile equipment
Mine infrastructure & services
•
Main fans and housing
•
Auxiliary fans
Mine dewatering
•
Face pumps
•
Sump pumps
Backfill plant
•
Surface backfill plant infrastructure
Haul roads
•
Portal to WRSF
•
Ventilation laydown
•
Powder magazine
•
Borrow pit road
Golder
Tailings facility & water management
•
Construction material quantity estimate only
Reclamation & closure
•
Inputs to SRCE model
R&O Consulting (R&O)
Site access road
•
Main access roads
SPF Water Engineering (SPF)
Water distribution
•
Water distribution and management
Fire Safety Systems Ltd (FSS)
Fire systems
•
Fire suppression, detection and protection systems
Idaho Power
Powerlines
•
Main substation and power line to site
Paramount Gold
Owner’s costs
•
Owner’s costs and inputs to G&A
18.1.2
Cost Estimate Summary – Initial Capital
The estimate is derived from budgetary pricing for major items in the mechanical equipment list, electrical equipment list and contractor work packages (e.g.
concrete, structural steel, platework, etc.), benchmarked against similar projects and scaled/escalated accordingly. The estimates were based on a number of fundamental assumptions as indicated in process flow diagrams, general arrangements,
material take offs (MTOs), cable schedules, scope definition and a work breakdown structure. The estimate included all associated infrastructure as defined by the scope of work developed in 2020 FS and carried in the 2022 FS update.
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The capital cost estimate is summarized in Table 18-2 and Table 18-3. The estimate has a base date of Q1, 2026 with no provision for forward escalation and noted in US dollars unless stated otherwise.
Table 18-2: Initial Capital Cost Estimate Summary (direct and indirect)
WBS
Description
$ M
% of Total Costs
1000
Mining
26.2
14
2000
Site development
7.2
4
3000
Mineral processing
43.4
23
4000
Tailings management
& waste rock facility
13.3
7
5000
On-site infrastructure
17.3
9
6000
Off-site
infrastructure
16.8
9
Direct Subtotal
124.6
66
7000
Project indirect costs
28.0
15
9000
Owner’s costs
15.6
8
Indirect Subtotal
43.6
23
8000
Provisions
(Contingency)
19.8
10
N/A
Capitalized
Operating cost
1.7
1
Project Total – Initial Capital
189.8
100
Note: totals may not match due to rounding
Table 18-3: Initial Capital Cost Estimate by Major Discipline
Disc.
Major Discipline
$ M
A
Architectural
8.6
B
Earthworks
6.5
C
Concrete
4.1
S
Structural steelwork
2.8
F
Platework
4.9
M
Mechanical
equipment
20.5
P
Piping
3.9
E
Electrical equipment
8.2
L
Electrical bulks
2.3
I
Instrumentation
0.6
N
Mobile equipment
2.1
R-1
Third party estimates
60.0
Direct Subtotal
124.6
O
Owner’s costs &
bonding
15.7
R-2
Third party estimates
2.0
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Disc.
Major Discipline
$ M
T
Project delivery (EPCM)
20.1
U
Field indirects
2.2
V
Spares & first fills
3.7
Indirect Subtotal
43. 6
Y
Provisions (Contingency)
19.8
N/A
Capitalized Operating cost
1.7
Project Total – Initial Capital
189.8
18.1.3
Cost Estimate Summary – Sustaining Capital
The sustaining capital cost estimate is provided in Table 18-4 and includes costs for mining operations (equipment
lease), mineral processing, tailings management and site infrastructure over the LOM.
Table 18-4: Sustaining
Capital Cost Estimate Summary (direct and indirect)
WBS
Description
$ M
1000
Mining
33.4
2000
Site development
—
3000
Mineral processing
3.9
4000
Tailings management & waste rock facility
20.4
5000
On-site infrastructure
—
6000
Off-site infrastructure
—
Direct Subtotal
57.7
7000
Project indirect costs
1.7
9000
Owner’s Costs
2.4
Indirect Subtotal
4.1
8000
Provisions (Contingency)
3.3
Project Total – Sustaining Capital
65.1
Note: totals may not match due to rounding
18.1.4
Definition of Costs
The capital cost estimate was developed for initial and sustaining capital, broken out into direct and indirect costs:
•
Initial capital is the capital expenditure required to start up a business to a standard where it is ready for
initial production.
•
Sustaining capital is the capital cost associated with the periodic addition of new plant, equipment or services
that are required to maintain production and operations at their existing levels, or a TSF expansion.
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•
Direct costs are those costs that pertain to the permanent equipment, materials and labor associated with the
physical construction of the process facility, infrastructure, utilities, buildings, etc. Contractor’s indirect costs were contained within each discipline’s all-in rates.
•
Indirect costs include all costs associated with implementation of the plant and incurred by the Owner, engineer
or consultants in the project design, procurement, construction, and commissioning.
18.1.5
Methodology
The estimate was updated in Q2 2026 based on a mix of budgetary quotations for major equipment supply, detailed material take-offs and engineered/factored
quantities and costs, and detailed unit costs supported by contractor bids, consistent with AACE Class 3 estimating guidelines.
The estimate was based on
an engineering, procurement and construction management (EPCM) approach where the EPCM contractor will oversee the delivery of the completed project from detailed engineering and procurement to the transfer of a working facility. The EPCM contractor
shall engage and coordinate several subcontractors to complete all work within the given scopes.
The structure of the estimate was a build-up of the
direct and indirect cost of the current quantities; this included the installation/construction hours, unit labor rates and contractor distributable costs, bulk and miscellaneous material and equipment costs, any subcontractor costs, freight and
growth.
The craft wages carried in the estimate were calculated based on current contractor bids and adjusted to align with current industry rates for
the project area. The labor rates reflect the composition of the project location using local Oregon labor and other surrounding regional workforces from neighboring states.
Percentages were added to the base labor rate for concrete, structural, mechanical, piping, electrical and instrumentation whilst earthworks was based on
sub-contractor rates. Distributable costs were allocated by percentage per discipline based on Ausenco’s historical data confirmed by back calculating contractor indirect costs from the returned bids.
Mechanical and electrical equipment were updated to a Q2 2026 basis with pricing for major equipment based on budget quotations. Other minor equipment costs
were from historical data from recent projects and studies or developed using engineering estimates.
18.1.6
Exchange Rates
The exchange rates used were determined from the XE.com website as of March 1, 2026 and were applied to foreign currency data. The exchange rates in Table
18-5 were used.
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Table 18-5: Exchange Rates used in the FS
Forex Rate
USD
1.000 CAD
0.733
1.000 AUD
0.711
1.000 USD
1.000
Note: CAD = Canadian dollar, AUD = Australian dollar, USD = US dollar
18.1.7
Market Availability
The pricing and delivery information for quoted equipment, material and services was provided by suppliers based on the market conditions and expectations
applicable at the time of estimated development.
Market conditions are susceptible to the impact of demand and availability at the time of purchase and
could result in variations in the supply conditions. The estimate in this report is based on information provided by suppliers and assumes that current challenges faced with the supply and availability of equipment and services are not applicable
during the proposed execution phase.
18.1.8
Mining Capital Cost Estimate
18.1.8.1
Underground Capital Costs
The underground capital costs were estimated using quotes and InfoMine cost estimates. The underground capital costs are listed in Table 18-6.
Table 18-6: Underground Capital Costs
Equipment
Model
Quantity
Quote
or
Estimate
Buy or
Lease
Total Cost
($ M)
Dual boom—development drill rig
Sandvik DD422i
3
Quote
Lease
4.9
Underground loader
Sandvik LH307
4
Quote
Lease
3.9
Truck with ejector bed
Sandvik TH320
3
Quote
Lease
3.2
Front-end loader (share with surface & underground)
CAT 962H
2
Quote
Lease
1.0
Powder loader
CAT 440
1
Quote
Lease
0.2
Telehandler
CAT TL1255
2
Quote
Lease
0.6
Dozer (share with surface & underground)
CAT D6T
2
Quote
Lease
1.2
Motor grader
CAT 160
1
Quote
Lease
0.8
Shotcrete Sprayer
GetMan Proshot Concrete Sprayer
1
Quote
Rent
0.8
Shotcrete Truck
GetMan ProMix 6
1
Quote
Rent
0.6
Lube Truck
Getman A64 SE Lube
1
Quote
Rent
0.6
Water Truck
Getman A64 SE Water Sprayer
1
Quote
Rent
0.5
Scissor deck
Getman A64 SE SL
1
Quote
Rent
1.2
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Equipment
Model
Quantity
Quote or
Estimate
Buy or
Lease
Total Cost
($ M)
Mine Rescue Truck6
Kovatera KT200
1
Quote
Rent
0.3
Diamond Drilling
Hydracore HC200UG
1
Estimate
Buy
0.3
Tractor
Kubota 5100
4
Quote
Buy
0.3
4WD Twin Cab Utility
Light Vehicle 4WD Twin
Cab Utility 1/2 ton
3
Quote
Buy
0.3
Refuge Chambers
MineARC 16 person
2
Quote
Buy
0.2
Bio-Lavatories
MineARC EnviroLAV
4
Quote
Buy
0.1
UG Shop Equipment
Misc.
1
Estimate
Buy
0.7
Mine Remote Stench system
Remote and Manually
2
Quote
Buy
0.03
Main Fan
Spendrup 274-183-900-A-
D
1
Quote
Buy
0.8
Main Fan Installation
Misc.
1
Quote
Buy
0.4
Auxiliary fans
JetAir Axiflow fan Model
O-4150-B
5
Quote
Buy
0.2
Auxiliary pumps
Peak TD350HH
5
Quote
Buy
0.1
Pump Station supplies
Misc.
1
Estimate
Buy
0.2
Face pump
TD250HH 13HP
5
Quote
Buy
0.06
Initial supplies & inventory
Powder, bolts, pipe,
inventory
1
Estimate
Buy
0.2
Mobile load center (electrical)
Intermountain Electrical
Inc
3
Quote
Buy
0.7
Jumbo boxes
Terminator T2 Box
4
Quote
Buy
0.9
Portal preparation
Misc.
1
Quote
Buy
0.7
Capital Development Contractor Mobilization
Misc.
1
Quote
Buy
0.1
Compressed air
Sullair model LS16009 985
ACFM@125 PSIG
4
Quote
Buy
0.4
Spare parts – main fan
Spare main fan + starter
1
Quote
Buy
0.5
Spare parts – fans, MLC, jumbo box, compressor
—
1
Quote
Buy
0.1
Spare parts – pumps
—
1
Quote
Buy
0.04
Backfill plant
Master Plant – Simem
WetBaton 100
1
Quote
Buy
1.8
Backfill Plant Addon for shotcrete
Simem
1
Quote
Buy
0.2
Installation
Misc
1
Estimate
Buy
0.9
Mine Dispatch System
GroundHog Enterprise SIC
Software—Initial Setup
1
Quote
Buy
0.02
Mining Admin Office IT setup
Misc.
1
Estimate
Buy
0.04
Blast Logger iKon Logger
Orica iKon
3
Quote
Buy
0.01
iKon Blaster
Orica iKon Blaster 3000 or
equivalent
2
Quote
Buy
0.02
Leaky Feeder system
Cable, Amplifier, Install
1
Estimate
Buy
0.2
Note: Costs are rounded; therefore, minor variances from actual costs may occur in the table.
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The capital costs are categorized into ‘buy’, ‘lease’, or ‘rent’. Items
categorized as ‘lease’ will be lease-to-own. Items categorized as ‘rent’ will be rented for a period of three years, after which a lumpsum payment will be made to purchase them. A portion of those costs pertain to initial
capital, and the remaining amount has been apportioned to sustaining capital. The summary for leasing costs by year is shown in Table 18-7.
Table 18-7: Underground Leasing Costs
Item
Unit
Year 0
Year 1
Year 2
Year 3
Year 4
Year 5
Year 6
Year 7
Year 8
Total
Down payment
$
M
1.7
1.5
0.0
0.0
0.0
0.0
0.0
0.0
0.0
3.2
Principal payment
$
M
0.4
1.7
2.3
2.5
2.7
2.3
0.7
0.0
0.0
12.8
Net capital
$
M
2.2
3.2
2.3
2.5
2.7
2.3
0.7
0.0
0.0
15.9
Interest payment
$
M
0.2
0.7
0.8
0.6
0.4
0.1
0.2
0.0
0.0
2.8
Total payments
$
M
2.4
3.9
3.1
3.1
3.1
2.4
0.7
0.0
0.0
18.7
Note: totals may not match due to rounding
18.1.8.2
Cost Estimate Summary (Mining)
Initial mining capital costs are summarized in Table 18-8.
Table 18-8: Initial Mining Capital Cost Estimate Summary
WBS
Description
$ M
1100
Mine portal construction
0.8
1200
Mine development/production
14.9
1300
Mine fixed equipment
1.6
1400
Mine infrastructure and services
0.9
1500
Mine fleet
4.0
1600
Mine dewatering
0.1
1700
Mine pre-production costs
0.2
1800
Backfill plant
1.9
2100
Bulk earthworks
0.8
2200
Road
0.3
7000
Other indirects
1.2
9100
Owner’s costs
0.8
8100
Contingency
2.5
Project Total – Initial mining-related capital costs
29.9
Note: Costs are rounded to the nearest million USD for reporting purposes; therefore, minor variances from the actual costs
may occur in the table.
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18.1.9
Processing and Overall Site Infrastructure Capital Cost Estimate
18.1.9.1
Basis of Estimate Methodology
18.1.9.1.1
Direct Costs
Direct costs are quantity-based and include all permanent equipment and materials associated with the physical construction of the facility. Cost estimates
include:
•
Direct labor-hours and labor
•
Contractor distributable
•
Permanent equipment and bulk materials
•
Freight and subcontracts.
18.1.9.1.2
Labor Productivity
Productivity factors were used to capture the productivity loss due to conditions experienced in the Project area.
Site productivity was assessed for each discipline using the scorecard method. Unit-labor hours were multiplied by the productivity factors for total
labor-hours per line item. Total labor-hours were then compared against returned contractor bids to ensure sufficient labor-hours were carried in the estimate.
18.1.9.1.3
Contractor Labor Rates
The contractor labor wages carried in the estimate were calculated from a recently completed project by Ausenco in Washington State. The rates were benchmarked
against historical data for labor in Oregon and Idaho. The labor rates reflect the use of local labor and surrounding regional workforces. The rates are fully burdened.
18.1.9.1.4
Contractor Distributable Costs
Percentages were added to the base labor rate for concrete, structural, mechanical, piping, electrical and instrumentation. Earthworks were based on
sub-contractor rates. Distributable costs were allocated by percentage per discipline based on Ausenco’s in-house database and confirmed by back calculating contractor indirect costs from the returned bids.
18.1.9.1.5
Earthworks & Site Preparation
Items such as engineered fill are to be sourced from borrow pits and stockpiles on site. MTOs were taken from an Autodesk Civil 3D model of the plant layout
and general arrangements.
Sub-contract rates were used in the estimate for bulk earthworks requirements. Prices carried in the estimate were a
combination of rates from local contractors and Ausenco’s in-house database for benchmarking.
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18.1.9.1.6
Concrete Supply & Installation
The scope of the concrete works allows for all concrete work in the process plant and relevant on-site facilities. MTOs were prepared by engineering and are
based on calculations derived from a 3D layout model, general arrangement drawings and sketches.
The basis for the development of installed concrete was
the product of concrete material supply and installation costs. Labor costs included the necessary consumables, reinforcement bar, and formwork. Supply of ready-mix concrete costs were sourced from contractors in the area for current pricing and
benchmarked against other reference projects in a similar geography. The overall unit rates were comparable to those in Ausenco’s in-house database for projects in Oregon and Idaho.
The cost of an on-site batch plant was excluded from the estimate as the mine site is located within driving distance to Vale and Boise. Both cities have
existing ready-mix plants.
18.1.9.1.7
Structural Steel
Structural steel quantities were prepared by engineering based on calculations derived from a 3D layout model, general arrangement drawings and sketches.
The basis for the development of installed structural steel was the product of steel material supply and installation costs. Labor-hours were based on local
contractors for the installation of the necessary structural sections and all associated items such as stair treads, hand railing and grating with adjustments by Ausenco for productivity.
Pricing was sourced from fabricators in Idaho, Montana and Arizona and allowed for the supply, fabrication, shop detailing and painting of bulk steel products
graded as light, medium, heavy and extra heavy structural steel designations, and miscellaneous steel including checker plate, grating and handrail.
The
structural, mechanical and piping (SMP) contractor will be free-issued the steel for assembly on site.
18.1.9.1.8
Architectural
A buildings list was developed from general arrangement drawings and historical data of similar facilities. Concrete and internal support steel for equipment
inside the buildings were accounted for in the engineer’s MTOs.
Pricing for the supply and installation of the building packages was from current
quotations and Ausenco’s in-house database from recent relevant projects. Allowances were carried in the estimate for furniture, fittings and fixtures. Overhead cranes were not included in the building costs as they were accounted for in the
mechanical equipment list.
18.1.9.1.9
Mechanical Equipment
A detailed mechanical equipment list was developed, generally sized by process and mechanical engineering, and emphasized the selection of proven designs.
Quantities were based on process flow diagrams, equipment list, equipment datasheets and general arrangement plans. Mechanical equipment was included in the capital cost estimate in accordance with the latest revision of the equipment list.
Pricing for major process mechanical equipment items was based on budget quotations. Other minor equipment costs were from Ausenco’s in-house database
and recent studies or estimated by engineering.
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18.1.9.1.10
Platework
A platework list was prepared for chute work, launders, hoppers, bins and major field erected tanks and silos, this list makes up part of the mechanical
equipment list. Platework and liners were quantified in short tons or square feet by engineering. Tanks were designed as panel-style bolted and welded construction. Mechanical bulks quantities were prepared by engineering based on design
calculations, previous similar designs, and forced quantity factors. Some minor structures were developed from drawings and sketches.
The basis for the
development of installed platework steel was the product of steel material supply and installation costs. Labor-hours were based on local contractors in the region for the installation of the bulk steel plate and rubber or carbon steel lining
products with adjustments by Ausenco for productivity.
Pricing was sourced from fabricators in Idaho, Montana and Arizona and allows for the supply,
fabrication, shop detailing of platework elements.
Rubber and carbon steel lining products were costed using historical data. Installation hours of
rubber liners have been based on increments of 1/4 inches (6 mm Updated) thickness. Installation hours of carbon steel liners were based on increments of 5/8 inches (16 mm) thickness. Tanks identified and designed as panel-style bolted
tanks were quoted as supply and install.
The SMP contractor will be free-issued the platework bulk steel for assembly on site.
18.1.9.1.11
Process Plant Piping
The process plant piping was factored from the total installed mechanical. The factor allowed for pipe, fittings, supports, valves, paint, special pipe items
and flanges. The piping bulks will be free issued to the SMP contractor for installation.
18.1.9.1.12
Fire Protection and Detection Piping
Fire protection and detection piping was included in the estimate based on a vendor quotation from FSS. The quote allowed for the supply and installation of
fire protection/detection equipment, pipes, fittings, supports, valves, special pipe items, and flanges.
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18.1.9.1.13
Water Supply and Distribution
Potable water, fresh water, raw water pipeline, wells and septic water supply and distribution piping were included in the estimate based on a vendor quotation
from SPF. The estimate included supply rates for pipe and fittings, civil works and mechanical equipment.
18.1.9.1.14
Pipelines
Ausenco’s scope included the installation of the decant line and tailings distribution lines. The supply rates included pipe and fittings with standard
install hours applied to the labor rate. The tailings pipelines will be free issued to the SMP contractor for installation.
18.1.9.1.15
Electrical Equipment
The proposed electrical equipment list aligns with the current mechanical equipment list and load list.
Pricing for major electrical equipment items was developed from a combination of budget quotations for major items and Ausenco’s in-house database.
A 15 kV overhead powerline branching off the main powerline from the mine site was included to feed the process plant, ancillary buildings and tailings
area.
18.1.9.1.16
Electrical Bulks
An electrical cable schedule was developed for the Project covering the major power and control cables between electrical equipment (transformers and
switchgears/motor control centers or MCCs) and between MCCs and motors. Based on the layout and e-room placement, MTOs for high voltage cables were developed via manual take-offs for major lines and an average length per area was established for
medium voltage cables.
Cable trays were estimated via manual take-offs for 6–36-inch trays together with allowances for cable tray covers. While
not all cables would travel the full length of the longest tray run, any over-supply is expected to cover costs for risers, bends, covers, fittings and fixtures.
An allowance for terminations, small lighting, and receptacles was developed by factoring from the mechanical equipment supply costs.
18.1.9.1.17
Instrumentation and Control
Instrumentation was developed by factoring from the mechanical equipment supply costs. The process control system for the process plant was priced separately.
18.1.9.1.18
Mobile Equipment
Equipment prices included price ex-factory, freight and erection at site if required.
The major equipment fleet for support to the completion of the site development and bulk earthworks was built up into the earthworks unit rates. Surface
mobile equipment to support the construction of the process plant and on-site infrastructure was included in the all-in labor rate provided by the contractors.
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18.1.9.1.19
Freight Costs
Freight costs included inland transportation, export packing, all forwarder costs, ocean freight and air freight where required, insurance, receiving port
custom agent fees, and local inland freight to the planned mine site for all bulk materials and process plant equipment.
The estimate freight costs were
determined by applying a percentage to the applicable items direct supply cost and then including this cost as a separate value on each line items build-up. Vendor-supplied freight costs were included for major equipment where available.
Vendor packages, third-party costs and any other subcontract and design and construct items were inclusive of any required freight to site
18.1.9.1.20
Import Duties
Import duties were excluded from the estimate.
18.1.9.2
Capitalized Operating cost
A total of $1.7 million of operating costs were included in the initial capital cost estimate, for costs incurred during the pre-production period.
18.1.9.3
Cost Estimate Summary (Processing and Overall Site Infrastructure)
The initial capital cost estimate for process and site infrastructure areas is provided in Table 18-9.
Table 18-9: Initial Capital Cost Estimate Summary for Process and Site Infrastructure Areas
WBS1
Description
$ M
1400
Mine infrastructure and services
2.0
2100
Bulk earthworks
4.7
2200
Roads
1.1
2300
Surface water management
0.3
3100
Crushing & ore handling
7.2
3200
Grinding & classification
5.4
3300
Gravity separation
0.4
3400
Carbon-in-leach (CIL)
8.0
3500
Carbon elution and goldroom
6.8
3600
Cyanide detox
3.5
3700
Tailings thickening
0.3
3800
Reagents
2.0
3900
Plant building & services
10.0
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WBS1
Description
$ M
4100
Tailings facility & water management
0.2
4200
Tailings & reclaim pipelines
0.5
5100
Power generation & distribution
1.1
5200
Water supply & distribution
6.2
5400
Ancillary buildings
7.2
5500
Surface mobile equipment
2.1
5600
Bulk fuel storage & distribution
0.3
5700
IT and communications
0.3
5800
General
0.3
6100
Main site access road
4.7
6200
Overhead power line
12.2
Direct Subtotal
86.5
7200
Field indirects
2.8
7300
Temporary utilities & services
0.6
7400
Temporary equipment
0.3
7600
Vendors representatives
0.4
7700
Spares & first fills
2.8
7800
Start-up& commissioning
0.6
7900
EPCM and expenses
15.4
Indirect Subtotal
23.0
8100
Provision (contingency)
15.0
N/A
Capitalized Operating cost
1.7
Project Total – Initial Process & On-Site Infrastructure
Capital
126.1
Note: totals may not match due to rounding
18.1.10
Tailings Storage and Temporary Waste Rock Storage Facilities Capital Cost Estimate
18.1.10.1
Material Take-off and Bid Solicitation
As discussed in Section 15.5 and presented in Table 15-1, the TSF is designed to be constructed in a total of
three primary construction stages (Stages 1 through 3). Stage 1 is separated into two intermediate construction phases (Stages 1A and Stage 1B). In this study, Stage 1A is designated as initial capital and Stage 1B and Stage 2 are denoted as
sustaining capital. Stage 3 is currently not required for the FS mine production.
Stage 1A will be the initial stage of construction and provides the
basic infrastructure to be able to operate the TSF and TWRSF, including underdrains, embankments, stormwater diversion channels, and a TSF reclaim pond. Stage 1B and Stage 2 will include construction of embankment raises and TSF basin
expansions to provide additional tailings storage.
The TSF design, as presented in Section 15.5 is of sufficient detail that construction quantity
estimates for major earthwork, geosynthetics, and gravity piping are to an accuracy of 10%. Construction quantities estimates were developed by WSP using Autodesk AutoCAD Civil 3D designs of the TSF and TWRSF facilities and general arrangements and
design details.
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Upon WSP receiving and compiling all quotations, the quotations were provided to Paramount and Ausenco for
inclusion in the overall capital cost estimate and financial model prepared by Ausenco. For this Report, the preferred general contractor provided an updated capital construction cost estimate to account for design revisions of the TSF and TWRSF as
presented in WSP’s 2021 Detailed Design Report, and reflect present unit prices for all construction equipment, labor and materials.
18.1.10.2
Cost Estimate Summary (Tailings Storage and Temporary Waste Rock Storage Facilities)
Ausenco and Paramount incorporated WSP’s preferred contractor’s bid to create a construction cost estimate for
Stage 1A, Stage 1B, and Stage 2 to develop the initial and sustaining cost estimates considering the timing required for construction of the TSF expansions as required by the FS mine life. Table 18-10
presents the initial capital cost applied for Stage 1A of the TSF in the economic analysis in Section 19.
Table
18-10: Initial TSF Capital Cost Estimate Summary
WBS
Description
$ M
4100
Tailings Facility & Water Management
12.7
Direct Subtotal
12.7
7000
Indirects
3.0
Indirect Subtotal
3.0
8100
Provision (Contingency)
2.4
Project Total – Initial Tailings Capital
18.1
Note: totals may not match due to rounding.
18.1.11
Indirect Capital Cost Estimate
18.1.11.1
Project Preliminaries (Field Indirects)
Project preliminaries are items or services which are not directly attributable to the construction of specific physical facilities of plant or associated
infrastructure but required to be provided as support during the construction period.
These costs may include:
•
Temporary construction facilities: site offices, induction center, first aid facilities, admin, portable toilets,
temporary fencing, temporary roads and parking.
•
Temporary utilities: power supply, temporary grounding and generators, construction lighting, and water supply.
•
Construction support: site clean-up and waste disposal, material handling, maintenance of buildings and roads,
testing and training, service labor, site transport, site surveys, QA/QC, and security.
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•
Construction equipment, tools and supplies purchased by the owner or EPCM contractor: heavy equipment and cranes,
large tools, consumables, scaffolding and purchased utilities.
•
Material transportation and storage incurred by the Owner or EPCM contractor: all types of freight, agents,
staging and marshalling.
•
Site office: local services and expenses, communications and office furniture.
Project preliminaries were developed from first principles and summarized in the estimate to cover the construction duration for the process plant and on-site
infrastructure. RESPEC and Golder accounted for field indirect costs in their respective discipline areas to support their scope of work.
18.1.11.2
Operational Spares
Mechanical and electrical spares for operations purposes were provided by vendor quotes for major equipment for the initial first year of operations. The
remaining equipment was factored using Ausenco’s in-house database.
18.1.11.3
Capital (Insurance) and Commissioning Spares
Major mechanical and electrical spares for capital/insurance and commissioning purposes were provided by vendor quotes for major equipment. The remaining
equipment was factored using Ausenco’s in-house database.
18.1.11.4
First Fills
First fills include the costs for the initial construction, first fills for installed equipment and process first fills. First fills were developed by process
engineering and separated in the estimate as either construction or commissioning first-fills.
18.1.11.5
Vendors
Costs for vendor representatives for commissioning were identified from the returned budget quotes as a cost per day or an allowance made by engineering. Costs
were separated in the estimate as either construction or commissioning vendor representatives.
18.1.11.6
Pre-commissioning, Commissioning
Commissioning assistance from mechanical completion to hand over was developed using Ausenco’s EPCM costs. A modification squad was allowed for in the
estimate. The modification squad was carried out to allow the commissioning team to make minor modifications or provide labor assistance for commissioning. The modification squad allowance has been estimated using Ausenco’s in-house database.
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18.1.11.7
Construction Camp and Catering
No onsite camp was allowed for in the estimate. It was assumed that all labor would be sourced from within the region and would reside in either Vale, OR or
Boise, ID.
18.1.11.8
EPCM
EPCM services costs covered such items as engineering and procurement services (home office based), construction management services (site based), project
office facilities, information technology, staff transfer expenses, secondary consultants, field inspection and expediting, corporate overhead and fees.
The overall EPCM budget for Ausenco’s scope of work was developed from first principles and was inclusive of allocations for other direct costs and
general expenses.
18.1.11.9
Cost Estimate Summary (Indirects)
The initial capital cost estimate for indirects provided in Table 18-11.
Table 18-11: Initial Capital Cost Estimate Summary for Indirects
WBS1
Description
$ M
7200
Field indirects
7.9
7300
Temporary utilities & services
0.6
7400
Temporary equipment
0.3
7600
Vendor representatives
0.4
7700
Spares & first fills
2.8
7800
Start-up& commissioning
0.6
7900
EPCM and expenses
15.4
Project Total—Indirects
28.0
Note: totals may not match due to rounding.
18.1.12
Owner’s Costs
The Owner’s initial capital cost estimate is provided in Table 18-12.
Table 18-12: Initial Owner’s Cost Estimate Summary
Description
$ M
Corporate overheads
0.2
Environmental monitoring
0.3
Site office
0.4
Setup & running costs
0.7
Staff & labor
2.6
Bonding
11.5
Project Total – Initial Owner’s Capital
15.7
Note: totals may not match due to rounding.
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18.1.13
Contingency
18.1.13.1
Estimate Contingency
Estimate contingency was included to address anticipated variances between the specific items contained in the estimate and the final actual project cost.
The estimate contingency does not allow for the following:
•
Abnormal weather conditions
•
Changes to market conditions affecting the cost of labor or materials
•
Changes of scope within the general production and operating parameters
•
Effects of industrial disputes.
18.1.13.2
Contingency Analysis
Each of the contributing parties to the estimate provided a contingency value based on their engineering scope and cost development level of definition. These
inputs were applied as percentages to their respective base estimates, resulting in a contingency of $19.8 million, or 10% of the total initial project capital cost.
18.1.13.3
Management Reserve Analysis
No management reserve was allowed for.
18.1.13.4
Escalation
No escalation was proportioned to any part of the estimate.
18.1.14
Reclamation and Closure Capital Cost Estimate
Closure costs were provided in Section 17.7 and total approximately $21.1 million over the LOM.
18.2
Operating Cost Estimate
18.2.1
Summary and Basis of Operating Cost Estimate
A summary of the LOM operating costs is provided in Table 18-13.
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Table 18-13: Summary of operating costs over LOM
Cost Category
Unit Costs LOM Average
($ per ton processed)
Total LOM Costs
($ M)
Mining (excl. pre-production)
140.60
332.9
Process
37.72
89.3
G&A
20.65
48.7
Total
198.96
470.9
*
Note: totals may not match due to rounding
The basis for the operating cost estimates is included in the discussions provided in the following sub-sections by discipline area. The operating cost
estimates have an accuracy range of ±15% per AACE Class 3 estimate guidelines.
18.2.2
Mining Operating Cost Estimate
The mining costs were built up by first principles using the productivity assumptions in Section 13.11 and budgetary quotes. The mining costs were
applied in the model to each profile type and ground support type. The mining costs were summarized by year and totaled for the LOM ($332.9 million over the LOM) to determine the total mining costs.
A summary of the mining cost per ton is shown in Table 18-14.
Table 18-14: Summary of Underground Mining Costs per ton
Mine
Yearly (000’s of $/a)
Percentage of Total Cost (%)
Mill Feed ($/ton)
Drilling
17,093
5
%
7.25
Blasting
15,125
5
%
6.42
Mucking
6,593
2
%
2.80
Bolting
34,974
11
%
14.83
Shotcrete Spray
6,250
2
%
2.65
Shotcrete Transmixer
904
0
%
0.38
Haulage
6,543
2
%
2.78
Backfill
64,550
19
%
27.38
Subtotal mining operating cost
152,034
46
%
64.48
Labor cost operating
129,293
39
%
54.84
Electrical cost operating
10,951
3
%
4.64
Diesel fuel cost operating
7,602
2
%
3.22
General supplies/Indirect operating
2,999
1
%
1.27
Contingency
29,988
9
%
12.72
Subtotal general operating cost
180,832
54
%
76.70
Total (mining + general)
332,865
100
%
141.18
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Excluding mining costs from the pre-production period (accounted for in the initial capital cost) results in
an average mining cost of $140.60/ton processed over the LOM.
18.2.2.1
Underground Labor
Staffing was estimated by benchmarking against similar projects. The labor costs incorporated requirements for underground operations such as operating
underground equipment, technical support, underground electricians, underground mechanics, and underground management. A summary of the underground labor required is included as Table 18-15.
Table 18-15: Underground Labor Summary
Position
Labor Code
No. of Employees
Total Cost per Year ($’000/a)
Technical Service Engineer
Salary
1
226.2
Mine engineer
Salary
1
187.9
Mine surveyor
Salary
2
341.9
Mine geologist
Salary
2
325.1
Mine superintendent
Salary
1
226.2
Mine clerk
Hourly
1
74.3
Mine foreman
Salary
4
916.7
Underground miner
Hourly
33
5,802.1
Underground laborer
Hourly
25
2,483.3
Mine electricians
Hourly
2
401.1
Mine maintenance superintendent
Salary
1
251.1
Heavy equipment elec-mechanic
Hourly
10
2,097.2
Welder
Hourly
2
339.8
Serviceman
Hourly
2
270.8
Maintenance laborer
Hourly
2
270.8
Light vehicle mechanic
Hourly
1
129.0
Total Underground Personnel
83
3,759.9
The quantities shown in Table 18-15 do not include milling process personnel nor site
management/general & administrative staff. The total underground mine personnel required will be 83 workers. The shift system for administrative personnel is planned to be four days on and three days off, at 10 hours per day.
Production-related mining personnel (operators, fitters, electricians, and assistants) will work a shift system of four days on and three days off in two crews. Each crew will provide 12 hour/day coverage so that the mine can operate 24 hours/day,
four days per week. Some personnel may work additional overtime through weekends for backfill, dewatering, and care-and-maintenance requirements, as needed. The operating calendar is based on 360 operating days per year. The planned mine
organization chart is shown in Figure 18-1.
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Figure
18-1: Proposed Mine Organizational Chart
Source: MDA(RESPEC), 2022.
18.2.2.2
Other Underground Costs
Power costs were estimated using consumptions from the equipment manufacturer and the cost of power. A unit power cost of $0.0584 per kWh was used, based on a
December 2025 power rate schedule from Idaho Power.
Diesel costs were estimated using consumptions from InfoMine cost models, equipment specifications,
vendor information, and the cost of local diesel. The unit cost of diesel used for this study is $2.51/gallon.
General supplies were estimated using 1.0%
of the total underground operating costs. The total cost of general supplies is $1.27/ore ton. The general supplies included mining software, engineering supplies, geology supplies, survey supplies, and other general supplies.
18.2.3
Process Operating Cost Estimate
The process operating cost is estimated at $89.3 million over the LOM, or an average of $37.72/ton processed over the LOM. A breakdown of these costs is
presented in Table 18-16.
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Table
18-16: Average Annual Process Operating Cost
Cost Center
Annual Costs* ($’000/a)
Percentage of Total (%)
Unit Costs LOM Average
($ per ton processed)
Reagents & Operating Consumables
3,277
33
12.46
Power
1,292
13
4.91
General Maintenance
791
8
3.01
Mobile Equipment
156
2
0.59
Labor
4,404
44
16.75
Total
9,919
100
37.72
*Note: totals may not match due to rounding
18.2.3.1
Reagents and Operating Consumables
Individual reagent consumption rates were estimated based on the metallurgical testwork results, Ausenco’s in-house database and experience, industry
practice and peer-reviewed literature. Reagent costs were obtained through vendor quotes or benchmarking for similar projects performed by Ausenco.
Other
consumables (e.g., liners for the primary crusher, ball mill and ball media for the mills) were estimated using:
•
Metallurgical testing results (abrasion index)
•
Vendor inputs and recommendations
•
Ausenco’s in-house calculation methods, including simulations
•
Forecast nominal power consumption.
Reagents and consumables represent 33% of the total process operating cost at an average of $12.46/ton of plant feed over the LOM.
18.2.3.2
Fuel and Utilities
A unit power cost of $0.0584/kWh was used, based on a December 2025 power rate schedule from Idaho Power. Carson Fuel provided an all-in contract price for
diesel based on annual forecast usage for the Project at $2.51/gal, which was used for the Study.
The processing power draw was based on the average
power utilization of each motor on the electrical load list for the process plant and services. Power will be supplied by the Idaho Power Company to service the facilities at the site. The total average process plant power cost is $4.91/ton over the
LOM, or 13% of the total process operating cost.
18.2.3.3
Maintenance
General maintenance costs are 8% of the total operating cost at $3.01/ton over the LOM. Annual maintenance consumable costs were calculated based on a total
installed mechanical capital cost by area using a weighted average factor from 1–5%. The factor was applied to the cost of the installed mechanical equipment.
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18.2.3.4
Mobile Equipment
Vehicle costs were based on a scheduled number of light vehicles and mobile equipment, including fuel, maintenance, spares and tires, and annual registration
and insurance fees. This corresponds to an average of $0.59/ton over the LOM.
18.2.3.5
Labor
Staffing numbers and positions were estimated based on other similar projects and Ausenco references. The labor costs incorporate requirements for plant
operation, such as management, metallurgy, operations, maintenance and assay laboratory, and contractor allowance. The total operational labor is 38 employees, averaging 21 employees per shift.
Individual personnel were divided into their respective positions and classified as either 10-hour or 12-hour shift employees. Salaries were determined using
published U.S. labor market data and were also used to develop the total G&A labor cost. The rates were estimated as overall rates, including all burden costs.
Table 18-17: Process Plant Labor
Position
Labor Code
No. of Employees
Processing Superintendent
Salary
1
Gold Room Operator
Hourly
1
Reagents/TMF Operator
Hourly
1
Shift Foreman/Crusher Operator
Hourly
4
Control Room Operator/Mill Operator
Hourly
4
CIL Operator/Elution Operator
Hourly
4
CN Destruction Operator
Hourly
4
Plant Metallurgist
Salary
1
Chief Assayer
Hourly
1
Assayer
Hourly
1
Sample Bucker
Hourly
2
Maintenance Foreman
Salary
1
Mill Wright/Fitter (crew)
Hourly
2
Service Man
Hourly
2
Electrical Foreman
Hourly
1
Contract Electrician
Hourly
1
Trades Assistant
Hourly
4
Electrician
Hourly
1
Mill Wright/Fitter (shift)
Hourly
1
Instrument Tech
Hourly
1
Total
38
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Labor costs represent 44% of the total process operating cost at an average of $16.75/ton of plant feed over
the LOM.
18.2.4
General and Administrative Operating Cost Estimate
A bottoms-up approach was used to develop estimates for G&A costs at $5.4M/a, or $48.7 million over the LOM, representing an average of
$20.65/ton processed over the LOM.
The G&A labor costs were estimated by developing a headcount profile for each department that was then forecast
over the LOM. Labor rates were determined based on published U.S. labor market data and were applied to develop the total G&A labor cost.
Health and
safety equipment, supplies, training, and environmental costs were provided by Paramount Gold, as were the information technology and telecommunications costs for telecommunication, networking, internet, computers, radio system and repairs.
A breakdown summary of forecast LOM G&A costs is shown in Table 18-18.
Table 18-18: Annual Average G&A Operating Cost Summary
Cost Center
Annual Cost*
($000’s/a)
% of total
Unit Cost LOM Average
($/ton processed)
G&A maintenance
100.0
2
0.38
Personnel (incl. bonuses and benefits)
3,093
58
11.90
Human resources and public relations
231.4
4
0.89
Power
15.0
0.3
0.06
Laboratory
86.4
2
0.33
Miscellaneous, supplies & equipment
151.0
3
0.58
Fees and consulting services
946.4
18
3.64
G&A vehicles & transportation
80.1
1
0.31
Environmental
15.3
0.3
0.06
IT & telecommunications
60.0
1
0.23
Contract services
479.9
9
1.85
Mine software
45.4
1
0.17
Mine hardware
61.3
1
0.24
Total
5,365
100
20.65
*
For a typical operating year.
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19
ECONOMIC ANALYSIS
19.1
Forward-Looking Information
Paramount is subject to the reporting requirements of the Exchange Act and this filing and other U.S. reporting requirements are governed by Subpart 1300 of
Regulation S-K promulgated by the Securities and Exchange Commission (SEC). The results of the economic analyses discussed in this section represent forward-looking statements within the meaning of applicable securities laws relating to Paramount
Gold Nevada Corp. These statements by their nature involve substantial risks and uncertainties. Statements involving the foregoing results of economic analysis are forward-looking statements. Without limiting the generality of the foregoing, words
such as “may”, “anticipate”, “intend”, “could”, “estimate”, or “continue” or the negative or other comparable terminology are intended to identify forward-looking statements.
Should one or more of these risks or uncertainties materialize or should the underlying assumptions prove incorrect, actual outcomes and results could differ materially from those indicated in the forward-looking statements.
Information that is forward-looking includes, but is not limited to, the following:
•
Proven and Probable Mineral Reserve estimates which have been modified from Measured and Indicated Mineral
Resource estimates
•
Assumed commodity prices and exchange rates
•
Proposed mine production plan
•
Projected mining and process recovery rates
•
Assumptions as to mining dilution and estimated future production
•
Assumptions as geotechnical support requirements for underground openings
•
Proposed sustaining costs and operating costs
•
Seabridge Gold’s intentions to convert the NPI royalty into Paramount equity upon Paramount securing
sufficient construction financing
•
Assumptions as to closure costs and closure requirements
•
Assumptions as to environmental, permitting, and social risks.
Additional risks to the forward-looking information include:
•
Changes to costs of production from what is assumed
•
Unexpected variations in quantity of mineralized material, grade or recovery rates
Grassy Mountain Project
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May 27, 2026
•
Geotechnical or hydrogeological considerations during mining being different from what was assumed
•
Failure of mining methods to operate as anticipated
•
Failure of plant, equipment or processes to operate as anticipated
•
Changes to assumptions as to the availability of electrical power, and the power rates used in the operating cost
estimates and financial analysis
•
Unrecognized environmental risks
•
Unanticipated reclamation expenses
•
Ability to maintain the social license to operate
•
Accidents, labor disputes and other risks of the mining industry
•
Changes to interest rates
•
Changes to applicable tax rates.
Calendar years used in the financial analysis are provided for conceptual purposes only. Additional permits still must be obtained in support of operations;
and approval to proceed is still required from Paramount’s Board of Directors.
19.2
Methodology Used
The Project has been evaluated using a discounted cashflow (DCF) analysis based on a 5% discount rate. Cash inflows consist of annual revenue projections. Cash
outflows consist of capital expenditures, operating costs, taxes, and royalties. These are subtracted from the inflows to arrive at the annual cash flow projections. Cash flows are taken to occur at the midpoint of each period. Tax calculations
involve complex variables that can only be accurately determined during operations and, as such, the actual post-tax results may differ from those estimated. A sensitivity analysis was performed to assess the impact of variations in metal prices,
discount rate, head grade, recovery, total operating cost, and total capital costs.
An economic model was developed to estimate annual pre-tax and
post-tax cash flows and sensitivities of the Project based on a 5% discount rate. Tax estimates involve complex variables that can only be accurately calculated during operations and, as such, the post-tax results are approximations.
The capital and operating cost estimates developed specifically for this Project are presented in Section 18 using second quarter (Q2) 2026 US dollars.
The economic analysis was run on a constant dollar basis with no inflation.
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19.3
Financial Model Parameters
The economic analysis contemplated in the FS uses metal prices that remain constant over the Project life and are based on the assessment outlined in
Section 16 at $3,600/oz gold and $48.00/oz silver prices. No price inflation or escalation factors were utilized as commodity prices can be volatile, and there is the potential for deviation from the forecast. Exchange rates used in the Report
are detailed in Section 18.1.6.
The economic analysis was performed using the following assumptions:
•
Construction period of 18 months
•
All construction and operating costs prior to achieving commercial operation are capitalized
•
Mine life of 9.3 years
•
Cost estimates in constant Q2 2026 US dollars with no inflation or escalation
•
Capital costs funded with 100% equity (no financing costs assumed)
•
All cash flows discounted at a 5% discount rate to the start of construction
•
Metal is assumed to be sold in the same year it is produced
•
No contractual arrangements for refining or offtake are in place.
19.4
Taxes
The Project was evaluated on a post-tax basis to provide an approximate value of the potential economics. The tax model was prepared by MNP LLP, an independent
tax consultant. The calculations are based on the tax regime as of the date of the FS, and include estimates for Paramount’s expenditures, and related impacts to various tax pool balances, between the FS and the assumed construction start
date.
At the Report effective date, the Project was assumed to be subject to the following tax regime:
•
US Federal corporate income tax system of a 21% tax rate;
•
Oregon tax rate of 7.6% for net proceeds of more than $1 million;
•
Total undiscounted tax payments are estimated to be $117.2 million over the LOM.
19.5
Ro yalty
A 1.5% net smelter revenue (NSR) royalty was assumed, resulting in approximately $21.1 million in undiscounted royalty payments over the LOM. The FS assumes
that Seabridge will convert its 10% NPI royalty into Paramount equity upon Paramount securing sufficient construction financing, and thus the NPI was not included in the financial model.
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19.6
Economic Analysis
The economic analysis was performed assuming a 5% discount rate.
The pre-tax net present value (NPV) discounted at 5% is $458.9 M; the IRR is 42.8%; and payback period is 2.1 years.
On a post-tax basis, the NPV discounted at 5% is $374.7 M; the IRR is 38.9 %; and the payback period is 2.2 years.
A summary of forecast Project economics is shown graphically in Figure 19-1 and listed in Table 19-1.
A cashflow on an annualized basis is provided in Table 19-2.
Figure 19-1: Forecast Project Post-Tax Unlevered, Undiscounted Free Cash Flow ($ M)
Source: Ausenco 2026
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Table
19-1: Summary of Forecast Project Economics
Area
Item
Units
LOM Total/Avg.
General
Gold price
$/oz
3,600
Silver price
$/oz
48.00
Mine life
years
9.3
Total mill feed tons
tons x 1,000
2,358
Production (gold)
Mill head grade Au
oz/ton
0.18
Mill recovery rate Au
%
92.6
Total mill ounces recovered Au
oz x 1,000
385.8
Total average annual production Au
oz x 1,000
41.4
Production (silver)
Mill head grade Ag
oz/ton
0.28
Mill recovery rate Ag
%
73.5
Total mill ounces recovered Ag
oz x 1,000
480.1
Total average annual production Ag
oz x 1,000
51.5
Operating Costs
Mining cost
$/ton processed
140.60
Processing cost
$/ton processed
37.72
G&A cost
$/ton processed
20.65
Total operating costs
$/ton processed
198.96
Refining cost Au
$/oz
5.00
Refining cost Ag
$/oz
0.50
*Cash costs net of by-products
$/oz Au
1,217.95
**AISC net of by-products
$/oz Au
1,441.57
Capital Costs
Initial capital
$M
189.8
Sustaining capital
$M
65.1
Closure costs
$M
21.1
Financials(pre-tax)
Gross Revenue
$M
1,410.6
Pre-tax unlevered free cash flow
$M
658.0
Pre-tax NPV, 5%
$M
458.9
Pre-tax IRR%
%
42.8
Pre-tax Payback
years
2.1
Financials(post-tax)
Post-tax unlevered free cash flow
$M
540.7
Post-tax NPV, 5%
$M
374.7
Post-tax IRR%
38.9
Post-tax Payback
years
2.2
Notes:
*
Cash costs consist of mining costs, processing costs, G&A and refining charges and royalties.
**
All-in sustaining costs (AISC) includes cash costs plus sustaining capital and closure costs. AISC is at the
Project-level and does not include an estimate of corporate G&A.
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Table 19-2: Project Cashflow on an Annualized Basis
Dollar figures in Real 2026 $ M unless otherwise noted
Macro Assumptions
Units
Total/
Avg.
Y -2
Y -1
Y 1
Y 2
Y 3
Y 4
Y 5
Y 6
Y 7
Y 8
Y 9
Y 10
Gold Price
$/oz
3,600
3,600
3,600
3,600
3,600
3,600
3,600
3,600
3,600
3,600
3,600
3,600
3,600
Silver Price
$/oz
48.00
48.00
48.00
48.00
48.00
48.00
48.00
48.00
48.00
48.00
48.00
48.00
48.00
Revenue
$M
1,410.6
–
2.9
124.1
186.3
167.7
179.9
174.0
168.5
160.4
113.2
126.7
6.9
Operating Cost
$M
(469.1)
–
–
(44.8)
(54.3)
(53.4)
(51.9)
(52.9)
(50.7)
(55.9)
(49.7)
(47.8)
(7.7)
Refining Charges
$M
(2.2)
–
(0.0)
(0.2)
(0.3)
(0.3)
(0.3)
(0.3)
(0.3)
(0.3)
(0.2)
(0.2)
(0.0)
Royalties
$M
(21.1)
–
(0.0)
(1.9)
(2.8)
(2.5)
(2.7)
(2.6)
(2.5)
(2.4)
(1.7)
(1.9)
(0.1)
EBITDA
$M
918.2
–
2.9
77.2
129.0
111.6
125.0
118.3
115.0
101.9
61.6
76.7
(0.9)
Initial Capex
$M
(189.8)
(55.4)
(134.4)
–
–
–
–
–
–
–
–
–
–
Sustaining Capex
$M
(65.1)
–
–
(24.4)
(10.7)
(8.3)
(11.9)
(7.2)
(1.2)
(0.4)
(0.4)
(0.4)
–
Closure Capex
$M
(21.1)
–
–
–
–
–
–
–
–
–
–
–
(21.1)
Salvage Value
$M
15.8
–
–
–
–
–
–
–
–
–
–
–
15.8
Pre-Tax Unlevered Free Cash Flow
$M
658.0
(55.4)
(131.6)
52.8
118.2
103.2
113.1
111.0
113.8
101.4
61.1
76.3
(6.2)
Corporate Income Tax
$M
(117.2)
–
–
(2.0)
(4.5)
(3.9)
(18.4)
(20.9)
(22.6)
(19.5)
(10.9)
(14.5)
–
Post-Tax Unlevered Free Cash Flow
$M
540.7
(55.4)
(131.6)
50.8
113.7
99.3
94.8
90.1
91.2
81.9
50.2
61.7
(6.2)
Production Summary
Total Resource Mined
kt
2,357.8
–
5.2
226.3
287.4
272.0
284.1
265.2
240.4
298.0
233.6
226.9
18.8
Mill Head Grade (Au)
oz/t
0.18
–
0.17
0.16
0.19
0.18
0.19
0.19
0.21
0.16
0.14
0.16
0.11
Mill Head Grade (Ag)
oz/t
0.28
–
0.25
0.25
0.27
0.25
0.28
0.28
0.26
0.31
0.29
0.30
0.23
Mill Recovery (Au)
%
92.6
–
92.4
92.3
92.9
92.7
92.8
92.9
93.1
92.2
91.8
92.4
90.5
Mill Recovery (Ag)
%
73.5
–
72.2
71.6
73.4
72.2
73.8
73.6
72.6
74.9
74.2
74.6
70.8
Recovered Gold
koz
385.8
–
0.8
34.0
51.0
46.0
49.2
47.7
46.2
43.7
30.8
34.5
1.9
Recovered Silver
koz
480.1
–
0.9
39.9
57.8
50.0
59.4
54.3
45.6
68.0
50.5
50.5
3.1
Payable Gold
koz
385.5
–
0.8
33.9
51.0
45.9
49.2
47.6
46.2
43.7
30.8
34.5
1.9
Payable Silver
koz
477.7
–
0.9
39.7
57.6
49.7
59.1
54.0
45.4
67.7
50.3
50.3
3.1
Gold Revenue
$M
1,387.6
–
2.9
122.2
183.5
165.3
177.1
171.4
166.3
157.1
110.7
124.2
6.8
Silver Revenue
$M
22.9
–
0.0
1.9
2.8
2.4
2.8
2.6
2.2
3.3
2.4
2.4
0.1
Total Revenue
$M
1,410.6
–
2.9
124.1
186.3
167.7
179.9
174.0
168.5
160.4
113.2
126.7
6.9
Royalties
$M
21.1
–
(0.0)
(1.9)
(2.8)
(2.5)
(2.7)
(2.6)
(2.5)
(2.4)
(1.7)
(1.9)
(0.1)
Total Offsite Charges
$M
(2.2)
–
(0.0)
(0.2)
(0.3)
(0.3)
(0.3)
(0.3)
(0.3)
(0.3)
(0.2)
(0.2)
(0.0)
Total Operating Costs
$M
(469.1)
–
–
(44.8)
(54.3)
(53.4)
(51.9)
(52.9)
(50.7)
(55.9)
(49.7)
(47.8)
(7.7)
Mine Operating Costs
$M
(332.9)
–
(1.4)
(30.2)
(38.6)
(38.0)
(36.3)
(37.6)
(35.8)
(40.1)
(35.0)
(33.2)
(6.6)
Mill Processing
$M
(89.3)
–
(0.3)
(9.2)
(10.3)
(10.0)
(10.2)
(9.9)
(9.5)
(10.5)
(9.4)
(9.2)
(0.7)
G&A Costs
$M
(48.7)
–
–
(5.4)
(5.4)
(5.4)
(5.4)
(5.4)
(5.4)
(5.4)
(5.4)
(5.4)
(0.4)
Capitalized Operating Cost Transfer
$M
1.7
–
1.7
–
–
–
–
–
–
–
–
–
–
Total Initial Capital
$M
(189.8)
(55.4)
(134.4)
–
–
–
–
–
–
–
–
–
–
Capitalized Processing Operating cost
$M
(1.7)
–
(1.7)
–
–
–
–
–
–
–
–
–
–
1000—Mining
$M
(31.9)
(0.7)
(31.2)
–
–
–
–
–
–
–
–
–
–
2000—Site Development
$M
(6.2)
(2.2)
(4.0)
–
–
–
–
–
–
–
–
–
–
3000 – Min. Processing
$M
(43.5)
(15.2)
(28.2)
–
–
–
–
–
–
–
–
–
–
4000 – Tail/Waste Mgmt
$M
(13.4)
(4.7)
(8.7)
–
–
–
–
–
–
–
–
–
–
5000—Onsite Infra.
$M
(17.4)
(6.1)
(11.3)
–
–
–
–
–
–
–
–
–
–
6000—Off-Site Infra.
$M
(16.9)
(5.9)
(11.0)
–
–
–
–
–
–
–
–
–
–
7000—Indirects
$M
(26.0)
(9.1)
(16.9)
–
–
–
–
–
–
–
–
–
–
8000—Provisions
$M
(17.3)
(6.1)
(11.3)
–
–
–
–
–
–
–
–
–
–
9000—Owner Costs
$M
(15.7)
(5.5)
(10.2)
–
–
–
–
–
–
–
–
–
–
Total Sustaining Capital
$M
(65.1)
–
–
(24.4)
(10.7)
(8.3)
(11.9)
(7.2)
(1.2)
(0.4)
(0.4)
(0.4)
–
1000—Mining
$M
(40.8)
–
–
(22.4)
(7.2)
(4.0)
(3.6)
(2.9)
(0.8)
–
–
–
–
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Dollar figures in Real 2026 $ M unless otherwise
noted
Macro Assumptions
Units
Total/Avg.
Y -2
Y -1
Y 1
Y 2
Y 3
Y 4
Y 5
Y 6
Y 7
Y 8
Y 9
Y 10
2000—Site Development
$M
–
–
–
–
–
–
–
–
–
–
–
–
–
3000 – Min. Processing
$M
(3.9)
–
–
(0.4)
(0.4)
(0.4)
(0.4)
(0.4)
(0.4)
(0.4)
(0.4)
(0.4)
–
4000 – Tailings/Waste Mgmt
$M
(20.4)
–
–
(1.6)
(3.1)
(3.9)
(7.9)
(3.9)
–
–
–
–
–
5000—Onsite Infra.
$M
–
–
–
–
–
–
–
–
–
–
–
–
–
6000—Off-Site Infra.
$M
–
–
–
–
–
–
–
–
–
–
–
–
–
7000—Indirects
$M
–
–
–
–
–
–
–
–
–
–
–
–
–
8000—Provisions
$M
–
–
–
–
–
–
–
–
–
–
–
–
–
9000—Owner Costs
$M
–
–
–
–
–
–
–
–
–
–
–
–
–
Total Capital Expenditures Including Salvage Value
$M
(260.2)
(55.4)
(134.4)
(24.4)
(10.7)
(8.3)
(11.9)
(7.2)
(1.2)
(0.4)
(0.4)
(0.4)
(5.3)
Notes:
All dollar figures are
in Real 2026 million USD unless otherwise noted.
†
Yearly cashflow figures for closure costs extend to 20+ years beyond end of mine life and are not shown above;
the total closure cost listed reflects the accurate closure costs over the LOM.
*
Cash costs consist of mining costs, processing costs, mine-level G&A and refining charges and royalties.
**
AISC includes cash costs plus sustaining capital and closure costs.
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19.7
Sensitivity Analysis
A sensitivity analysis was conducted on the base case pre-tax and post-tax NPV and IRR, using the following variables: commodity prices, mill head grades,
initial capital cost, operating cost, metallurgical recovery, and discount rate.
Figure 19-2 shows the summary
pre-tax sensitivity, and Figure 19-3 shows the post-tax sensitivity results, with detailed sensitivity tables presented in Table 19-3 and Table 19-4.
Figure
19-2: Pre-Tax NPV & IRR Sensitivity Results
Source: Ausenco, 2026.
Figure
19-3: Post-Tax NPV & IRR Sensitivity Results
Source: Ausenco, 2026.
The
analysis showed that the Project is most sensitive to metal price, head grade, metallurgical recovery rates, and initial capital cost, and less sensitive to operating cost.
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Table 19-3: Summary Pre-Tax Sensitivity Analysis
Pre-Tax Sensitivity to
Metal Price
Pre-Tax NPV5% (US$M)Sensitivity to Discount Rate
Pre-Tax IRR (%) Sensitivity to Discount Rate
Commodity Price
Commodity Price
Discount Rate
(30
%)
(20
%)
(10
%)
—
10
%
20
%
30
%
Discount Rate
(30
%)
(20
%)
(10
%)
—
10
%
20
%
30
%
1.0
%
218.4
349.5
480.6
611.8
742.9
874.0
1,005
1.0
%
19.2
%
27.8
%
35.5
%
42.8
%
49.6
%
56.1
%
62.3
%
3.0
%
177.9
295.1
412.3
529.5
646.8
764.0
881.2
3.0
%
19.2
%
27.8
%
35.5
%
42.8
%
49.6
%
56.1
%
62.3
%
5.0
%
143.1
248.4
353.7
458.9
564.2
669.4
774.7
5.0
%
19.2
%
27.8
%
35.5
%
42.8
%
49.6
%
56.1
%
62.3
%
8.0
%
99.9
190.2
280.4
370.7
460.9
551.2
641.4
8.0
%
19.2
%
27.8
%
35.5
%
42.8
%
49.6
%
56.1
%
62.3
%
10.0
%
76.0
157.8
239.7
321.5
403.4
485.2
567.1
10.0
%
19.2
%
27.8
%
35.5
%
42.8
%
49.6
%
56.1
%
62.3
%
Pre-Tax NPV5% (US$M) Sensitivity to OPERATING COST
Pre-Tax IRR(%)Sensitivity to OPERATING COST
Commodity Price
Commodity Price
Total OPERATING COST
(30
%)
(20
%)
(10
%)
—
10
%
20
%
30
%
Total OPERATING COST
(30
%)
(20
%)
(10
%)
—
10
%
20
%
30
%
(20
%)
213.4
318.7
423.9
529.2
634.4
739.7
844.9
(20
%)
24.9
%
32.9
%
40.3
%
47.2
%
53.8
%
60.1
%
66.3
%
(10
%)
178.3
283.5
388.8
494.0
599.3
704.6
809.8
(10
%)
22.1
%
30.4
%
37.9
%
45.0
%
51.7
%
58.1
%
64.3
%
—
143.1
248.4
353.7
458.9
564.2
669.4
774.7
—
19.2
%
27.8
%
35.5
%
42.8
%
49.6
%
56.1
%
62.3
%
10
%
108.0
213.3
318.5
423.8
529.0
634.3
739.5
10
%
16.1
%
25.1
%
33.1
%
40.5
%
47.4
%
54.0
%
60.3
%
20
%
72.9
178.1
283.4
388.6
493.9
599.2
704.4
20
%
12.9
%
22.3
%
30.6
%
38.2
%
45.2
%
51.9
%
58.3
%
Pre-Tax NPV5% (US$M) Sensitivity to Initial CAPEX
Pre-Tax IRR(%)Sensitivity to Initial CAPEX
Commodity Price
Commodity Price
Initial CAPEX
(30
%)
(20
%)
(10
%)
—
10
%
20
%
30
%
Initial CAPEX
(30
%)
(20
%)
(10
%)
—
10
%
20
%
30
%
(20
%)
179.7
285.0
390.2
495.5
600.7
706.0
811.3
(20
%)
25.8
%
35.5
%
44.3
%
52.6
%
60.5
%
68.0
%
75.3
%
(10
%)
161.4
266.7
371.9
477.2
582.5
687.7
793.0
(10
%)
22.2
%
31.3
%
39.6
%
47.3
%
54.5
%
61.5
%
68.2
%
—
143.1
248.4
353.7
458.9
564.2
669.4
774.7
—
19.2
%
27.8
%
35.5
%
42.8
%
49.6
%
56.1
%
62.3
%
10
%
124.8
230.1
335.4
440.6
545.9
651.1
756.4
10
%
16.6
%
24.8
%
32.1
%
38.9
%
45.3
%
51.5
%
57.3
%
20
%
106.6
211.8
317.1
422.3
527.6
632.8
738.1
20
%
14.3
%
22.1
%
29.1
%
35.6
%
41.7
%
47.5
%
53.0
%
Pre-Tax NPV5% (US$M) Sensitivity to Mill Recovery
Pre-Tax IRR(%)Sensitivity to Mill Recovery
Commodity Price
Commodity Price
Mill Recovery
(30
%)
(20
%)
(10
%)
—
10
%
20
%
30
%
Mill Recovery
(30
%)
(20
%)
(10
%)
—
10
%
20
%
30
%
(20
%)
(9.9
)
73.5
156.8
240.2
323.5
406.9
490.2
(20
%)
3.8
%
12.8
%
20.4
%
27.2
%
33.4
%
39.3
%
44.8
%
(10
%)
66.6
161.0
255.3
349.6
443.9
538.2
632.5
(10
%)
12.1
%
20.7
%
28.3
%
35.3
%
41.8
%
47.9
%
53.8
%
—
143.1
248.4
353.7
458.9
564.2
669.4
774.7
—
19.2
%
27.8
%
35.5
%
42.8
%
49.6
%
56.1
%
62.3
%
10
%
219.6
335.8
452.0
568.3
684.5
800.7
916.9
10
%
25.5
%
34.3
%
42.3
%
49.8
%
57.0
%
63.8
%
70.5
%
20
%
296.1
423.3
550.5
677.6
804.8
931.9
1,059
20
%
31.4
%
40.4
%
48.7
%
56.6
%
64.1
%
71.3
%
78.3
%
Pre-Tax NPV5% (US$M) Sensitivity to Head Grade
Pre-Tax IRR(%)Sensitivity to Head Grade
Commodity Price
Commodity Price
Head Grade
(30
%)
(20
%)
(10
%)
—
10
%
20
%
30
%
Head Grade
(30
%)
(20
%)
(10
%)
—
10
%
20
%
30
%
(20
%)
(3.9
)
80.3
164.5
248.7
332.9
417.1
501.3
(20
%)
4.5
%
13.5
%
21.0
%
27.8
%
34.1
%
40.0
%
45.5
%
(10
%)
69.6
164.4
259.1
353.8
448.5
543.3
638.0
(10
%)
12.4
%
21.0
%
28.6
%
35.6
%
42.1
%
48.2
%
54.2
%
—
143.1
248.4
353.7
458.9
564.2
669.4
774.7
—
19.2
%
27.8
%
35.5
%
42.8
%
49.6
%
56.1
%
62.3
%
10
%
201.9
315.5
429.2
542.9
656.5
770.2
883.9
10
%
24.1
%
32.8
%
40.7
%
48.2
%
55.3
%
62.0
%
68.6
%
20
%
203.1
316.9
430.7
544.6
658.4
772.2
886.1
20
%
24.2
%
32.9
%
40.8
%
48.3
%
55.4
%
62.1
%
68.7
%
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Table 19-4: Summary Post-Tax Sensitivity Analysis
Post-Tax Sensitivity to Metal Price
Post-Tax NPV5% (US$M)Sensitivity to Discount Rate
Post-Tax IRR (%) Sensitivity to Discount Rate
Commodity Price
Commodity Price
Discount Rate
(30
%)
(20
%)
(10
%)
—
10
%
20
%
30
%
Discount Rate
(30
%)
(20
%)
(10
%)
—
10
%
20
%
30
%
1.0
%
195.8
298.6
400.8
502.3
603.5
704.7
805.9
1.0
%
17.9
%
25.5
%
32.4
%
38.9
%
44.9
%
50.7
%
56.2
%
3.0
%
158.2
250.9
342.6
433.7
524.5
615.1
705.6
3.0
%
17.9
%
25.5
%
32.4
%
38.9
%
44.9
%
50.7
%
56.2
%
5.0
%
125.9
209.8
292.7
374.7
456.5
537.9
619.4
5.0
%
17.9
%
25.5
%
32.4
%
38.9
%
44.9
%
50.7
%
56.2
%
8.0
%
85.7
158.5
230.1
300.9
371.3
441.3
511.3
8.0
%
17.9
%
25.5
%
32.4
%
38.9
%
44.9
%
50.7
%
56.2
%
10.0
%
63.4
129.9
195.2
259.6
323.7
387.3
450.9
10.0
%
17.9
%
25.5
%
32.4
%
38.9
%
44.9
%
50.7
%
56.2
%
Post-Tax NPV5% (US$M) Sensitivity to OPERATING COST
Post-Tax IRR(%)Sensitivity to OPERATING COST
Commodity Price
Commodity Price
Total OPERATING COST
(30
%)
(20
%)
(10
%)
—
10
%
20
%
30
%
Total OPERATING COST
(30
%)
(20
%)
(10
%)
—
10
%
20
%
30
%
(20
%)
180.1
263.0
345.0
426.8
508.3
589.7
671.1
(20
%)
22.8
%
29.9
%
36.5
%
42.7
%
48.5
%
54.1
%
59.5
%
(10
%)
153.1
236.5
318.9
400.8
482.4
563.8
645.2
(10
%)
20.4
%
27.8
%
34.5
%
40.8
%
46.7
%
52.4
%
57.9
%
—
125.9
209.8
292.7
374.7
456.5
537.9
619.4
—
17.9
%
25.5
%
32.4
%
38.9
%
44.9
%
50.7
%
56.2
%
10
%
97.8
183.0
266.2
348.6
430.5
512.0
593.5
10
%
15.2
%
23.2
%
30.3
%
36.9
%
43.1
%
48.9
%
54.5
%
20
%
65.1
155.7
239.5
322.3
404.5
486.1
567.6
20
%
12.1
%
20.8
%
28.1
%
34.9
%
41.2
%
47.1
%
52.8
%
Post-Tax NPV5% (US$M) Sensitivity to Initial CAPEX
Post-Tax IRR(%)Sensitivity to Initial CAPEX
Commodity Price
Commodity Price
Initial CAPEX
(30
%)
(20
%)
(10
%)
—
10
%
20
%
30
%
Initial CAPEX
(30
%)
(20
%)
(10
%)
—
10
%
20
%
30
%
(20
%)
162.5
246.4
329.2
411.3
493.0
574.5
655.9
(20
%)
24.4
%
33.1
%
41.1
%
48.6
%
55.6
%
62.3
%
68.7
%
(10
%)
144.2
228.1
310.9
393.0
474.7
556.2
637.6
(10
%)
20.9
%
29.0
%
36.4
%
43.3
%
49.8
%
56.0
%
61.9
%
—
125.9
209.8
292.7
374.7
456.5
537.9
619.4
—
17.9
%
25.5
%
32.4
%
38.9
%
44.9
%
50.7
%
56.2
%
10
%
107.6
191.5
274.4
356.5
438.2
519.6
601.1
10
%
15.3
%
22.5
%
29.0
%
35.1
%
40.8
%
46.2
%
51.3
%
20
%
89.4
173.2
256.1
338.2
419.9
501.4
582.8
20
%
13.1
%
19.9
%
26.1
%
31.8
%
37.2
%
42.3
%
47.2
%
Post-Tax NPV5% (US$M) Sensitivity to Mill Recovery
Post-Tax IRR(%)Sensitivity to Mill Recovery
Commodity Price
Commodity Price
Mill Recovery
(30
%)
(20
%)
(10
%)
—
10
%
20
%
30
%
Mill Recovery
(30
%)
(20
%)
(10
%)
—
10
%
20
%
30
%
(20
%)
(14.7
)
65.5
136.9
203.3
269.0
334.2
399.1
(20
%)
3.2
%
12.0
%
19.0
%
25.0
%
30.5
%
35.7
%
40.7
%
(10
%)
59.0
140.2
215.2
289.4
363.0
436.3
509.3
(10
%)
11.4
%
19.3
%
26.0
%
32.2
%
38.0
%
43.5
%
48.7
%
—
125.9
209.8
292.7
374.7
456.5
537.9
619.4
—
17.9
%
25.5
%
32.4
%
38.9
%
44.9
%
50.7
%
56.2
%
10
%
187.1
278.7
369.4
459.6
549.6
639.5
729.3
10
%
23.5
%
31.3
%
38.5
%
45.2
%
51.5
%
57.5
%
63.3
%
20
%
247.5
347.0
445.9
544.3
642.7
740.9
839.1
20
%
28.7
%
36.7
%
44.2
%
51.1
%
57.7
%
64.0
%
70.0
%
Post-Tax NPV5% (US$M) Sensitivity to Head Grade
Post-Tax IRR(%)Sensitivity to Head Grade
Commodity Price
Commodity Price
Head Grade
(30
%)
(20
%)
(10
%)
—
10
%
20
%
30
%
Head Grade
(30
%)
(20
%)
(10
%)
—
10
%
20
%
30
%
(20
%)
(8.9
)
72.1
143.1
210.0
276.4
342.2
407.8
(20
%)
3.9
%
12.7
%
19.5
%
25.5
%
31.1
%
36.4
%
41.4
%
(10
%)
61.8
142.9
218.2
292.8
366.7
440.3
513.6
(10
%)
11.7
%
19.5
%
26.2
%
32.4
%
38.3
%
43.8
%
49.0
%
—
125.9
209.8
292.7
374.7
456.5
537.9
619.4
—
17.9
%
25.5
%
32.4
%
38.9
%
44.9
%
50.7
%
56.2
%
10
%
173.0
262.8
351.6
440.0
528.0
615.9
703.8
10
%
22.2
%
30.0
%
37.1
%
43.7
%
49.9
%
55.9
%
61.6
%
20
%
173.9
263.9
352.8
441.3
529.4
617.5
705.5
20
%
22.3
%
30.1
%
37.1
%
43.8
%
50.0
%
56.0
%
61.7
%
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May 27, 2026
19.8
Conclusion – Economic Analysis
Based on the assumptions and parameters presented, the FS shows positive economics supported by a post-tax
NPV5% of $374.7 million and post-tax IRR of 38.9%. The initial Capex is at $189.8 million, with undiscounted LOM revenue of $1,410.6 million, sustaining Capex of $65.1 million, all-in Operating
cost of $469.1 million, and closure costs of $21.1 million.
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20
ADJACENT PROPERTIES
This section is not relevant to the report.
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21
OTHER RELEVANT DATA AND INFORMATION
This section is not relevant to the report.
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22
INTERPRETATION AND CONCLUSIONS
22.1
Introduction
The QPs note the following interpretations and conclusions in their respective areas of expertise, based on the review of data available for this Report.
22.2
Mineral Tenure, Surface Rights, Water Rights, Royalties and Agreements
Information from legal experts support that the tenure held is valid and sufficient to support a declaration of Mineral Resources and Mineral Reserves. Tenure
is in the geographic area referred to as the Grassy Mountains claims group. The Grassy Mountain deposit is within the Grassy Mountains claims group.
Paramount’s 100% ownership of the Grassy Mountain Project is subject to underlying agreements and royalties.
Seabridge Gold is entitled to a 10% net profits interest (NPI) royalty. Seabridge Gold, at the Report effective date, is the second largest Paramount
shareholder and has indicated that it will convert its NPI into equity in Paramount, thus the Seabridge NPI has not been included in the FS.
Sherry and
Yates retain a 1.5% royalty of the gross proceeds for the production of minerals from the patented and unpatented claims and a surrounding 1⁄2 mile area of
interest. This area covers the Grassy Mountain deposit. There are an additional two royalty obligations in the Project area; however, these are not over claims that host Mineral Resources or Mineral Reserves.
Paramount holds three patented claims over the Grassy Mountain deposit, which provides surface rights for that area. The surrounding surface rights associated
with the proposed locations of the Project surface facilities belong to the Federal government and are managed by the Vale District BLM office.
Paramount
holds a water right granted by the Oregon Water Resources Department to Calico.
Except for the exploration surface disturbance, primarily related to
drilling, and the network of water wells that will need to be reclaimed, there are no known environmental liabilities associated with the Grassy Mountain Project.
To the extent known to the QP, there are no other significant factors and risks that may affect access, title, or the right or ability to perform work on the
Project that are not discussed in this Report.
22.3
Geology and Mineralization
The Grassy Mountain deposit is an example of a low-sulfidation epithermal deposit.
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The understanding of the Grassy Mountain deposit settings, lithologies, mineralization, and the geological,
structural, and alteration controls on mineralization is sufficient to support estimation of Mineral Resources and Mineral Reserves.
22.4
Exploration
The exploration programs completed to date are appropriate for epithermal-style mineralization.
22.5
Analytical Data Collection in Support of Mineral Resource Estimation
Sampling methods are acceptable for Mineral Resource estimation.
Sample preparation, analysis and security are generally performed in accordance with exploration best practices and industry standards at the time the
information was collected.
The quantity and quality of the logged geological data, collar, and downhole survey data collected in the exploration and
infill drill programs are sufficient to support Mineral Resource estimation.
No material factors were identified with the data collection from the drill
programs that could significantly affect Mineral Resource estimation.
The sample preparation, analysis, and security practices and are acceptable, meet
industry-standard practices at the time they were undertaken, and are sufficient to support Mineral Resource estimation.
QA/QC submission rates met
industry-accepted standards at the time of the campaign. The QA/QC programs did not detect any material sample biases in the data reviewed that supports Mineral Resource estimation.
The data verification programs concluded that the data collected from the Project adequately support the geological interpretations and constitute a database
of sufficient quality to support the use of the data in Mineral Resource estimation.
22.6
Metallurgical Testwork
Metallurgical testwork and associated analytical procedures were appropriate to the mineralization type, appropriate to establish the optimal processing route,
and were performed using samples that are typical of the mineralization styles found within the Grassy Mountain deposit. Whole ore gold/silver leaching with cyanide and recovery with activated carbon is a well-established and effective method for
extracting and recovering gold and silver from free milling deposits like Grassy Mountain.
Samples selected for testing were representative of the
mineralization. Samples were selected from a range of depths within the deposit. Sufficient samples were taken so that tests were performed on sufficient sample mass.
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Recovery factors estimated are based on appropriate metallurgical testwork and are appropriate to the
mineralization and the selected process route. Overall plant recoveries for gold are predicted to range from 89.5–94.9% for head grades of 0.096–0.508 oz/ton (3.3–17.4 g/t) Au over the LOM. Overall plant recoveries for silver are
predicted to range from 62.7–80.4% for head grades of 0.161–0.523 oz/ton (5.5–17.9 g/t) Ag over the LOM.
Mercury is present in
sufficient concentration in the ore to warrant removal and management, and a mercury retort step has been incorporated into the flowsheet. Arsenic is present in the feed but at low concentrations of 3.47–5.34 oz/ton (119–183 g/t)
that are not expected to be problematic in processing. No other elements that may cause issues in the process plant or concerns with product marketability were noted.
22.7
Mineral Resource Estimation
The Grassy Mountain project’s estimate of mineral resources is reported using the definition in Subpart 229.1300—Disclosure by Registrants Engaged
in Mining Operations in Regulations S-K 1300.
RESPEC estimated the Grassy Mountain project’s mineral resources considering potential mining by open
pit methods, with the addition of a minor amount of underground-mineable resources lying immediately outside the pit walls of the lower portion of the pit. An alternate scenario, comprised exclusively of mining the higher-grade portion of the
deposit by underground methods, is also realistic, and this scenario was chosen to define the project mineral reserves. RESPEC constructed the resource model to accommodate both mining scenarios.
During resource modeling, RESPEC identified structural zones as the principal controls of high-grade mineralization within the central core of the Grassy
Mountain deposit. This high-grade mineralization has significant grade variability, which creates modeling uncertainties with respect to the location of the estimated high grades as distances from drill data increase. While open-pit mining would
minimize the risk imparted by the location uncertainty, underground mining requires far greater spatial accuracy. The current model is not sufficiently accurate for use in mining, particularly from underground. Properly oriented, closely spaced,
definition drilling would therefore be required to update the operation’s short- and long-term resource models and to refine geotechnical modeling and final stope designs. To reduce the uncertainties in the high-grade mineralization model,
RESPEC strongly recommends drilling from the surface prior to mining. Drilling on tighter spacing for more precise delineation of the high-grade mineralization and stope design would take place from underground. Underground drilling would also be
important from a geotechnical standpoint, as the high-grade mineralized structures are typically characterized by poor to very poor rock quality.
A total
of 14,947 sample intervals in the drill-hole database have gold assays but no silver analyses. In most of these cases, entire drill holes were not assayed for silver. For example, some of the early Atlas holes and all the Newmont holes were not
assayed for silver. A total of 4,720 of the sample intervals lacking silver assays lie within the domains that form the basis of the gold and silver resource estimates, while 19,938 sample intervals used in the resource estimates do have silver
analyses. However, the fact that silver adds very little value relative to gold mitigates the risk posed by the lower quantity of silver analyses.
RESPEC
believes that all factors that influence the prospect of economic extraction have either been addressed or could be resolved by further drilling. RESPEC is not aware of any unusual environmental, permitting, legal, title, taxation, socio-economic,
marketing, political, or other relevant factors not discussed in this technical report that could materially affect the mineral resource estimates as of the effective date.
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22.8
Mineral Reserve Estimates
An underground mining scenario is assumed using mechanized cut-and-fill methods.
The Proven and Probable Mineral Reserves for Grassy Mountain were estimated by first calculating an economic cut-off grade for mining underground stopes, then
using the cut-off grade to design stope shapes centered on Measured and Indicated Mineral Resource blocks with gold grades greater than or equal to the cut-off grade.
The calculated gold cut-off grade is 0.08 oz/ton Au. Silver was not included in the cut-off grade calculation due to its relatively small contribution
(2%) to total economic value.
The economic stope cut-off grade was used in the stope optimization to identify the Measured and Indicated blocks
available for consideration to be converted to Mineral Reserves. Measured and Indicated resource blocks with grades less than the economic stope cut-off grade were applied to internal dilution.
A modifying factor of 8% was used for calculating external dilution tons. All Inferred resource blocks or partial blocks within the stopes and all
unclassified material within the stopes is considered internal dilution. The tons were accounted for with zero grade.
Mining recovery is estimated to be
97% based on an assumed ore loss of 3%. This is considered appropriate for the highly selective mechanized cut-and-fill mining method selected for the Grassy Mountain deposit and it is based on similar operations in disseminated ore bodies.
The Mineral Reserve estimation for the Project is reported using the definition in Subpart 229.1300—Disclosure by Registrants Engaged in Mining
Operations in Regulations S-K 1300.
The Mineral Reserve estimation for the Project conforms to industry-accepted practices and is reported using the 2014
CIM Definition Standards.
The QP is not aware of any mining, metallurgical, infrastructure, permitting or other relevant factors not discussed in this
Report that could materially affect the Mineral Reserve Estimate.
22.9
Mining Method
The estimated mine life is 9.3 years.
The Grassy Mountain mine
will be an underground operation accessed via one decline and a system of internal ramps. The decline will be 15ft x 15ft in dimensions, developed from a portal on surface.
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An underground mining scenario is assumed using underhand mechanized cut-and-fill methods, which, following
ramp-up, will produce 1,300–1,400 tons/day, four days a week. This mining rate will provide sufficient material for the 750 tons/day mill and processing plant to operate at full capacity for seven days a week. The mechanized cut-and-fill
method is highly flexible and can achieve high recovery rates in deposits with complex geometries, as is the case at the Grassy Mountain deposit.
Level
stations will have a standoff distance from the orebody of approximately 300 ft. There are five stations planned for the mine, accessed off the decline, and each station will access up to five production levels.
The ventilation network was designed to comply with U.S. ventilation standards for underground mines. The planned ventilation will use a push/pull system and
will require one exhaust fan on surface. One set of stacked ventilation raises is included in the design to be used for ventilation and secondary egress. Cemented rock fill (CRF) will be used for backfill. Mine operations will be based on the usage
of mobile mining equipment suitable for underground mines. Equipment is conventional for mechanized cut-and-fill mining operations.
22.10
Geotechnical Considerations
The Grassy Mountain deposit is in a structurally complex, clay-altered, epithermal environment. Rock mass conditions in the infrastructure and production areas
vary from Poor to Fair quality with the poorest conditions within major structures that run longitudinally through and bound the deposit. Outside of these fault areas, rock mass conditions are generally Fair. However, localized zones of Poor ground
potentially associated with secondary structures or locally elevated alteration intensity are present throughout the planned mining area.
The North and
Grassy faults are significant fault structures that pose a risk to the stability of an open stoping method; hence, these areas are considered suitable only for a limited man-entry mining method such as mechanized cut-and-fill, where conditions can
be well controlled.
Degradation of Grassy Mountain Formation lithologic units results in difficult mining conditions that can be mitigated through
additional ground support. This would result in a higher mining cost with slower advance rates in those areas.
Based on the shallow depth, ground stress
is relatively low, and rock damage due to higher mining-induced stress concentrations is only anticipated in high-extraction or sequence closure areas and weaker rock mass areas. However, a reduction in the mining stresses around excavations is
likely to adversely affect the stability of large open-span areas. Tensile failure and gravity-induced unraveling are foreseen as the main failure mechanisms.
Ground support design considers industry-standard empirical guidelines and GMS’s experience in variable ground conditions. Compromises have been made in
the extraction sequence due to the need to balance grade and production profiles, extraction of wide orebody areas, and other geotechnical constraints. Ultimately, some aspects of the sequence may not be geotechnically optimal, and additional
analysis or design may be required.
Ground support design considers industry-standard empirical guidelines and GMS’s experience in variable ground
conditions. The extraction sequence has been developed to balance geotechnical constraints, ore recovery, production requirements and project economics. Based on the 2026 FS Update review completed by GMS, the updated mine planning information
remains generally consistent with the previously established underground geotechnical design basis. Nevertheless, local refinements to excavation sequencing, support requirements and extraction strategies may be warranted during future detailed
engineering, mine development and operations as additional geotechnical information becomes available.
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22.11
Processing and Recovery Methods
The process plant will be designed with conventional processing unit operations frequently used within the gold processing industry. The process plant will
treat 750 tons/day and will operate with two 12-h shifts per day, 365 days per year, producing gold doré bars. The major equipment within the process plant is specified in accordance with the climate, site conditions, ore grades and
metallurgical performance outlined in this report. Any deleterious metals present in the ore such as mercury will be abated by specialized equipment installed in the process plant and are not expected to impact payability terms.
22.12
Infrastructure
22.12.1
Key Infrastructure
Key Project infrastructure as envisaged in the FS includes: underground mine, including portal and decline; roads; site main gate and guard house;
administration building, training, first aid, change house and car park; process plant e-room; crushing area e-room; control room; reagent storage and building; gold room; assay laboratory and sample preparation area; plant workshop and warehouse;
truck shop, warehouse, wash pad; fuel facility, fuel storage and dispensing; water wells; 14.4 kV overland power line; fresh water supply and treatment; raw water tank; TSF; TWRSF; and explosives magazine.
22.12.2
Roads and Power
The main access road will use an existing BLM road, which will be widened to support operations.
Power will initially be provided by diesel power generators during the construction period (year 1). A power line will be built to site in that first year and
will deliver approximately 5.3 MW. The generators will remain on site as backup.
22.12.3
Waste Rock Storage and Borrow Pits
Waste rock will be temporarily stored on surface in a lined facility and will be returned underground as CRF.
Two borrow pits are planned, using contract mining. Borrow material will be used for construction, backfill, and reclamation.
22.12.4
Tailings Storage Facility
The TSF uses conventional designs and assumes construction in three primary stages and zero discharge. The facility will be constructed in stages (with Stage 1
constructed in two intermediate phases), as only 2.4 million tons are planned to be delivered to the TSF, only Stage 1, 2, and a portion of Stage 3 will be required. The TSF will fill the broad valley
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immediately west of the Grassy Mountain mine portal and process facilities and require embankments on the north and west sides to impound the tailings. The main embankment will cross the natural
drainage on the north side of the TSF, and a secondary embankment will be constructed along the western ridge. The facility will be a 100% geomembrane-lined facility with a continuous, engineered lining system extending across the impoundment basin
and the upstream slope of the embankments. The design is capable of storing runoff from tributary areas and direct precipitation on the facility resulting from the 500-year, 24-hour storm event, as well as an allowance for wave run-up due to wind
action.
The relevant results and interpretations related to the TSF design are based on the data and other information summarized in this Report.
Golder provided a detailed design for the TSF sufficient to contain the tailings projected from this study’s life of mine production (Golder, 2021d). At
this stage of the Project, there is reasonable certainty that the location and design of the TSF and TWRSF as presented for Study will be used as planned. No significant design changes are likely to be required provided that no material changes in
location or design are needed as a result of the on-going local, State, and Federal permitting process.
Provided that actual construction, operation,
management, and closure of the TSF do not differ materially from the results and design parameters summarized in this Report, there are no significant risks and uncertainties that could reasonably be expected to affect the reliability or confidence
in the TSF design and cost estimates.
If actual activities related to the construction, management, operation, and closure of the TSF do differ
materially from the results summarized in this Report, then the reasonably foreseeable impacts of these risks and uncertainties are most likely to be project delays and additional costs. However, any such delays or additional costs may reasonably be
expected to be managed in the ordinary course and should not impact overall Project viability.
22.12.5
Water Management
Contact and non-contact surface water will be routed around the plant site. Permanent channels were designed on a 100-year, 24-hour storm event with nine
inches of freeboard, or 500-year, 24-hour storm event without overtopping. Temporary channels were designed for a 25-year, 24-hour storm event with nine inches of freeboard, or 100-year, 24-hour storm event without overtopping.
22.12.6
Water Supply
Water supply from the raw water production wells and mine dewatering is projected to be sufficient to support the operational demands. Water demands are
expected to vary seasonally.
22.13
Markets and Contracts
No market studies have been completed. Gold and silver are freely-traded commodities. The doré that will be produced by the mine is considered to be
readily marketable with no deleterious/penalty elements. Although mercury is present in the ore, a retort and recovery system has been included to maintain doré quality.
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Metal pricing used in the economic analysis is based on long-term flat metal prices of $3,600/oz Au, and
$48.00/oz Ag, which are based on consensus forecasts from various financial institutions.
Paramount has no current contracts for property development,
mining, concentrating, smelting, refining, transportation, handling, sales and hedging, forward sales contracts or arrangements.
22.14
Environmental, Permitting and Social Considerations
Permitting activities began in 2012 with engagement with the state and federal agencies and collection of baseline data. The draft CPA was submitted to DOGAMI
in 2019 for review and comment by state agencies which were received by Calico and integrated into the final CPA. In December 2021, Calico submitted the final CPA to DOGAMI. Calico and DOGAMI have been working together as the draft permits have been
developed and are in the process of being finalized. The package of draft permits was issued for public review on December 8, 2025. Final permits are anticipated to be issued by all required state agencies in the second half of 2026.
In December 2021, Calico submitted a Plan of Operation (PoO) to the BLM. The draft EIS was published for public comment on August 8, 2025 and the final
EIS and record of decision was published on January 29, 2026. This record of decision provides federal authorization for the PoO following posting of a reclamation bond.
Paramount has been conducting baseline data collection for over ten years for environmental studies required to support the State and Federal permitting
process. Results indicate limited biological and cultural issues, air quality impacts appear to be within State of Oregon standards, traffic and noise issues are present but at low levels, and socioeconomic impacts are positive. The result of the
geochemical characterization identified that the geochemistry of the ore and waste rock provide for a possible source of future environmental issues as the Grassy Mountain Project is developed.
Data produced during the baseline and geochemical studies were used in the Project design process, including the design and operation of the TSF and handling
and use of waste rock as cemented backfill material, specifically considering environmental impacts. As outlined in Section 15, the design of the TSF and the waste rock management plan used the results of this geochemical characterization work.
A closure plan and RCE were submitted to the BLM and DOGAMI as part of PoO and CPA, respectively. The proposed reclamation approach for the Project
includes sealing the mine portal, lining, capping, and revegetating the TSF supported by temporary active solution management followed by passive solution management (evaporation) as the TSF drains down, the removal and offsite disposal of the
temporary waste rock storage facility liner, process plant and other infrastructure, the demolition and offsite disposal of the powerline and associated infrastructure, and in general the grading, capping, and revegetation of disturbed areas. This
approach will result in two post-reclamation landforms, the TSF and the quarry, and is anticipated to be completed within five years of ceasing operation. Post-reclamation monitoring, including groundwater and stormwater quality and revegetation
success, is proposed to meet Federal and State requirements and guidance and will continue for up to 30 years following reclamation.
The RCE was updated
in February 2026 to account for current unit rates and in response to input from DOGAMI and BLM during the permitting process. The reclamation surety associated with the proposed reclamation plan is $21,086,123 USD including indirect costs such as
contingency, contractor management and contractor profit. The BLM and State of Oregon are in negotiations to establish an MOU allowing the State of Oregon to hold the bond and oversee the reclamation activities.
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Social and community impacts have been considered and evaluated for the PoO in accordance with the NEPA and
other Federal laws, and the State of Oregon Socioeconomic Analysis. Potentially affected Native American tribes, tribal organizations and/or individuals were consulted during the preparation of the PoO and consultation continues to advise on the
project that may have an effect on cultural sites, resources, and traditional activities.
22.15
Capital Cost Estimate
The capital cost estimate is reported in Q2 2026 USD. The capital costs are at a minimum at a feasibility level of confidence of ±15% as is defined in S-K 1300.
Capital costs are estimated at $189.8 million of initial capital. This figure includes
$1.7 million of capitalized operating costs and $19.8 million in contingency (10%). In addition, there is $65.1 million of sustaining capital over the LOM and $21.1M in closure costs.
22.16
Operating Cost Estimate
The operating cost estimates are reported in Q2 2026 USD. The capital costs are at a minimum feasibility level of confidence of ±15% as is defined in
S-K 1300.
The LOM underground mining costs are estimated at $332.9 million over the LOM, and averages $141.18/ton processed over the LOM. Excluding
mining costs from the pre-production period (accounted for in the initial capital cost) results in an average mining cost of $140.60/ton processed over the LOM.
The LOM process operating cost is estimated at $89.3 million over the LOM, and averages $37.72/ton processed over the LOM.
The LOM general and administrative (G&A) costs are estimated at $5.4 million/a, or $48.7 million over the LOM, and average $20.65/ton processed
over the LOM.
22.17
Economic Analysis
An economic model was developed to estimate the project’s annual pre-tax and post-tax cash flows, sensitivities, and NPV results using a 5% discount
rate. Based on the assumptions and parameters, the economic analysis shows positive post-tax economics of $374.7 million NPV5% and 38.9% post-tax IRR. A sensitivity analysis was conducted on
the base-case pre-tax and post-tax NPV and IRR of the project using the following variables: metal prices, discount rate, operating costs, initial capex, metal recovery, and head grade.
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22.18
Risks and Opportunities
22.18.1
Risks
22.18.1.1
Geological Setting, Mineralization, and Deposit
Unlike states such as Nevada and Arizona, Oregon does not have a strong mining background. The Project may encounter a lack of mining skills and expertise at
the local level, which could affect Paramount’s ability to operate using local labor, until Paramount has trained sufficient local staff to suit Project requirements. There may also be effects on the Project caused by a lack of familiarity
with Mine Safety and Health Administration (MSHA) requirements at the local and State levels and at the local staff operator level, which may in turn lead to safety incidents. Such incidents could result in Project delays and affect the permitting
process.
22.18.1.2
Mineral Processing and Metallurgical Testing
If material flowability properties in the mined product are not aligned to the analysis and benchmarking completed in this FS, there is a risk of delayed
production ramp-up as well as remedial corrections required to the crushing circuit design. To mitigate this, additional materials flowability testwork should be completed on the mined product prior to detailed design.
22.18.1.3
Mineral Resource Estimate
During resource modeling, RESPEC identified structural zones as the principal controls of the high-grade mineralization in the central core of the Grassy
Mountain deposit. This mineralization has significant grade variability, which creates modeling uncertainties with respect to the location of the estimated high grades as distances from drill data increase. While an open-pit mining scenario would
minimize the risk imparted by the location uncertainty, underground mining would require far greater spatial accuracy. The current model is not sufficiently accurate for use in mining, particularly from underground. Updating the operation’s
short- and long-term resource models, refining geotechnical modeling, and making final stope designs requires properly oriented, closely spaced, definition drilling. RESPEC strongly recommends drilling from the surface prior to mining to reduce the
uncertainties in the high-grade mineralization model. Drilling on tighter spacing for more precise delineation of the high-grade mineralization and stope design would take place from underground. The underground drilling would also be important from
a geotechnical standpoint because the mineralized structures are typically characterized by poor to very poor rock quality.
22.18.1.4
Mining Methods
There is a risk that the estimated mining costs may not be achievable if additional support over that contemplated in the FS is required due to weak rock mass.
22.18.1.5
Infrastructure
Delays in the power line installation including the substation upgrade may result in delays to the Project schedule. As the Project power requirements are
relatively modest, there is a risk that the selected power provider may delay supply to the Project. However, power for the initial stages of project development can be generated using diesel-powered generators prior to the power supplier completing
the requisite power infrastructure for the Project.
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Water supply is envisaged to be partly from groundwater sources. Additional production wells may be required
to support operations, which will require permitting. In addition, well productivity may not be as envisaged, which may affect both the volume of water available for operations and the number of wells that must be pumped.
If additional borrow areas are required for construction and reclamation of the TSF that are more distant than contemplated in the FS, then reclamation
construction costs of the TSF will increase as compared to the costs estimated in this Report.
As construction work in Oregon is seasonal, poor weather
during the construction season may result in delays to the Project schedule. This is de-risked by scheduling earthworks and building construction in summer, with mill construction during winter months to be completed within a building.
22.18.1.6
Environmental Studies, Permitting and agreements with local individuals or groups
If non-governmental organizations object to the Project as envisaged in the FS, a number of risks may result. These could include additional capital costs or
increases in operating costs, delays in Project permitting, and delays in obtaining the social license to operate.
22.18.1.7
Capital Costs
There is a risk that the estimated mining capital costs may not be achievable due to the following factors:
•
Significant variations in tariffs could result in costs exceeding those assumed in the project estimates.
•
Additional ground support, beyond what is contemplated in the Feasibility Study (FS), may be required if a
greater extent of weak rock mass is encountered.
•
Increased demand for mining equipment may lead to delays in the delivery of planned equipment, potentially
impacting the project schedule. Furthermore, if alternative equipment must be procured, the costs may differ from those assumed in the current estimate.
22.18.1.8
Operating Costs
There is a risk that the estimated mining capital costs may not be achievable due to the following factors:
•
Additional ground support, beyond what is contemplated in the Feasibility Study (FS), may be required if a
greater extent of weak rock mass is encountered.
•
Increases in commodity prices (e.g., diesel, cement, steel) may lead to higher costs for raw materials and
supplies used in mining operations, resulting in increased operating costs.
•
Non-availability of skilled manpower may necessitate offering higher compensation to attract and retain qualified
personnel, potentially increasing operating costs. Additionally, there is a possibility that production mining activities may need to be outsourced, which could further increase operating costs, although it may help reduce capital expenditures.
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22.18.1.9
Economic Analysis
The economic analysis is based on long-term flat metal prices of $3,600/oz Au, and $48.00/oz Ag, which are based on consensus forecasts from various financial
institutions, with no considerations for escalation or inflation over the LOM. Large fluctuations to metals prices or drastic changes to inflation can negatively impact the project returns.
The risks or uncertainties that could reasonably be expected to affect the reliability or confidence in the projected economic outcomes are:
•
Geological and resource uncertainty
•
Metallurgical and processing uncertainty
•
Mining and geotechnical uncertainty
•
Infrastructure assumptions
•
Capital and operating cost uncertainties
•
Commodity price and market risks
•
Environmental, permitting, and regulatory risks
•
Social and community considerations
•
Political and jurisdictional risk
•
Project schedule assumptions
22.18.1.10
Operational Readiness
Mining is cyclical, and during an up-cycle, it can be difficult for any mining operation to attract quality staff. There is a cost risk to Paramount to source
a non-local operations team of sufficient experience and expertise, including additional costs to train and mobilize the team locally, to adequately support the Owner’s team.
Implementation of an effective operations readiness strategy and program is key to address the potential risk that Paramount currently has no active
operations. A lack of familiarity with the operational environment, particularly in Oregon, could otherwise result in unexpected Project delays or cost increases.
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22.18.2
Opportunities
22.18.2.1
Geological Setting, Mineralization, and Deposit
There is remaining exploration potential in the Project area. The Crabgrass, Bluegrass, North Bluegrass, Ryegrass and Dennis’ Folly areas in the Grassy
Mountain claims block were recommended for surface work with the goal of defining further exploration drill targets.
22.18.2.2
Mineral Processing and Metallurgical Testing
There is an opportunity to further optimize the flowsheet with respect to leach feed particle size and retention time that could positively affect the project
economics, further comminution and metallurgical testwork work should be completed to confirm the opportunity.
22.18.2.3
Mining Methods
The mine plan and cut-off grades used for the FS are based on conservative metal prices. There may be upside for the Project in higher metal pricing scenarios.
A higher metal price would potentially result in additional material meeting the cut-off grade criteria and being available to potentially convert to Mineral Reserves, thereby providing additional metal production and potentially, extending the mine
life.
22.18.2.4
Infrastructure
The mine plan requires sources of aggregate and borrow materials in support of road construction and CRF. Private sources for gravel construction along the
access route may be obtainable. There may also be an opportunity to source borrow material from local sources. This could lead to more simplified permitting for the development of these sources, and it could potentially reduce costs of the gravel
for the access road construction and borrow materials for CRF.
22.18.2.5
Environmental Studies, Permitting and agreements with local individuals or groups
The current post-closure land use is to return the site to a land use similar to current land uses (grazing, wildlife, recreation). There is the opportunity to
modify the closure plan to result in a beneficial post-closure land use that may be identified as the project progressed through construction and operation.
22.18.2.6
Capital Costs
The following factors present potential opportunities to optimize project outcomes and enhance value:
•
Tariff variability: potential fluctuations in tariffs provide an opportunity to optimize procurement strategies,
renegotiate contracts, or identify alternative suppliers to achieve cost efficiencies relative to current project estimates.
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•
Ground conditions and support requirements: encountering varying rock mass conditions offers an opportunity to
refine ground support design, improve geotechnical understanding, and implement more efficient or innovative support systems tailored to actual conditions.
•
Mining equipment market dynamics: increased demand for mining equipment creates an opportunity to reassess fleet
strategy, including evaluating newer or more efficient technologies. Exploring alternative equipment sourcing or leasing options may also optimize capital allocation and improve operational flexibility.
22.18.2.7
Operating Costs
The following factors present potential opportunities to optimize project outcomes and enhance value:
•
Ground conditions and support requirements: encountering varying rock mass conditions offers an opportunity to
refine ground support design, improve geotechnical understanding, and implement more efficient or innovative support systems tailored to actual conditions.
•
Commodity price movements: changes in commodity prices (e.g., diesel, cement, steel) present opportunities to
implement cost-control measures, adopt more efficient consumption practices, or explore bulk purchasing and long-term supply agreements to mitigate cost impacts.
•
Workforce availability and strategy: labor market constraints provide an opportunity to strengthen workforce
planning, invest in training and development, or adopt automation and productivity-enhancing technologies. Additionally, selectively contracting production mining could optimize the balance between operating and capital costs while improving
scalability and execution efficiency.
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23
RECOMMENDATIONS
23.1
Introduction
Based on the assumptions and parameters presented in the Report, the Grassy Mountain Project has a mine plan that is technically feasible and economically
viable. The positive financials of the Project ($374.7 million post-tax NPV5% and 38.9% post-tax IRR) support the mineral reserve.
A single work phase is proposed for recommended work to further derisk the project in advance of the next phase of the project (detailed engineering). The
estimated budget to complete the work program is set out by discipline area and summarized in Table 23-1.
Table 23-1: Phase 1 Recommended Work Program
Program Component
Cost ($ M)
Metallurgical testing
0.2
Drilling and Lithologic Modelling
2.5
Mining methods
0.1
Geotechnical
0.5
Hydrology
0.6
Infrastructure
0.1
Environmental Studies, Permitting and agreements with local individuals or groups
—
Total
4.0
Note: totals may not match due to rounding
23.2
Metallurgical Testing
It is recommended that further comminution and metallurgical testwork be completed, particularly on material to be processed in the first three years of
operations in order to investigate the opportunity of optimizing the comminution flowsheet and/or the opportunity to defer some equipment and capital costs into later years. Estimated cost $175,000.
It is recommended that material handling testwork be completed to optimize and de-risk material handling design of conveyors, bins and stockpiles and
potential operating issues associated with solids bridging or rat holes. Estimated cost $75,000.
23.3
Mineral Resource Estimate
The current lithologic model has not been fully rectified three-dimensionally. To support an active mining operation, a fully rectified lithological model is
recommended. This work is estimated to cost about $45,000.
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To mitigate some of the risks associated with significant grade variability observed in the structural zones
that are the principal controls of the high-grade mineralization within the central core of the Grassy Mountain deposit, a surface drilling program is recommended. The current model is not sufficiently accurate for use in mining, particularly from
underground. Properly oriented, closely spaced, definition drilling would be required to update the operation’s short- and long-term resource models, as well as to refine geotechnical modeling and final stope designs.
Before mining commences, drilling from the surface is strongly recommended to improve the understanding of the high-grade mineralization model. The drilling
would consist of 25 RC holes with core tails for a total of 19,250 ft and would target gaps in the high-grade core where the location and orientation of the mineralization is uncertain. The estimated cost for the drilling program is estimated at
$2,525,000, as given in Table 23-2.
Table 23-2: Recommended Work
Program for Mineral Resource Estimate
Program Component
Unit Cost ($)
Quantity
Task Cost ($)
3-D lithologic modeling
N/A
N/A
45,000
Drilling - RC
$66/ft
9,900 ft
654,000
Drilling - core
$131/ft
9,350 ft
1,229,000
Road and pad construction, reclamation
$233/hour
60 hours
14,000
Assays
$70/sample
4000 samples
280,000
Travel, lodging, field supplies, personnel
$1,685/day
180 days
303,000
Total
2,525,000
Drilling on tighter spacing from underground for more precise delineation of the high-grade mineralization and stope design
will be required following the surface drilling program. The drilling would also be important from a geotechnical standpoint as the mineralized structures are typically characterized by poor to very poor rock quality. The drilling would take place
during development of the mine, so no work program or cost estimate are included here. However, more precise definition of the deposit from underground will be critical for effective stope design, mine planning and geotechnical characterization.
23.4
Mining Methods
Additional optimization of mine design and underground production should be undertaken before construction begins. This should include:
•
Determination of an optimal gold price. A higher gold price will lower the cut-off grade and bring in more
economic material into the mine plan. Detailed mine plan will be required to design level access heading meeting design gradients such that it is ready for execution. This is estimated to require a budget of approximately $30,000 to complete.
•
Further analysis of the underground equipment types and sizes to identify possible improvements to the economics
and efficiencies. Support with bidding and bids evaluations will be required. A budget of $15,000 is recommended to complete this step.
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•
Contractor mining bids development and evaluation of bids. A budget of $15,000 is recommended to complete this
step.
•
Further analysis of the underground ventilation system should be completed. This analysis should include a
further detailing of the ventilation model, fan selection, and ventilation raise diameter. This is estimated to require a budget of approximately $15,000 to complete.
The mining recommendations overall have a completion cost estimated at approximately $75,000.
Table 23-3: Recommended Work Program for Mining Methods
Program Component
Unit
Cost ($)
Mine Design Detail
30,000
Equipment Selection and Bids
15,000
Contractor Mining
15,000
Ventilation Model and design
15,000
Total
75,000
23.5
Geotechnical
A geotechnical classification should be used for narrow zones of weakness, both in rock core descriptions and during underground geotechnical mapping, to allow
for the differentiation, characterization, and geotechnical classification of clay matrix breccias, faults, faults/veins or other weakness zones. This was not analyzed in the FS due to lack of structural information.
A study should be completed to geotechnically characterize the vein/faults and document strength properties and mean thicknesses.
The seismic hazard study should be updated to provide additional quantification of the seismic risk for the Project area.
The empirical design using a lower Q’ value standard deviation range should be reviewed to determine the stability condition of all development and
determine what additional stability measures may be required if designs change due to a more conservative assessment of the Q’ values.
A pillar
dimensioning and stability analysis is recommended to be completed to provide recommendations to the mine design and planning department.
Additional
tests should be undertaken to test CRF strength resistance in response to changes in the cement and fly ash percentages to reduce the amount of cement that may be required.
A limit equilibrium analysis should be completed to assess the typical failure modes of caving, flexural, sliding and rotational as proposed by Mitchell and
Roettger (1989).
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Reinforcements should be installed during operations to intersect the vertical joints at an oblique angle to
improve the shear resistance. Otherwise, vertically-installed reinforcements may need to be longer than envisaged in this Report to penetrate beyond the potential height of the stable arch.
Wall response in permanent and temporary excavations must be measured during excavation to develop a better understanding of the interaction between bolts,
cable bolts and the rock mass.
A geotechnical risk model is recommended to economically quantify the risk of instabilities and prepare alternative plans
to ensure on time ore delivery.
An update should be undertaken to the reinforcement and support numerical analysis to support the shotcrete assumptions.
The three-dimensional numerical analysis of the timeframes assumed for excavation and backfill should be conducted on a month-by-month basis. This
monthly examination should evaluate displacement velocity against the stand-up time requirements for the excavations.
Rib pillars that are lower than
three drifts wide in drift excavations under rock mass environments (i.e. that are not under CRF) should be avoided, due to the risk of high stress concentrations in the pillar and therefore local instabilities.
The safety factor should be calculated as part of the numerical model update, to provide information on the response of the rock mass to the induced stress
through the excavation–backfill process.
Paramount should prepare a detailed monitoring plan for underground operations. The plan should include:
•
geotechnical inspections and permanent ground control during operations;
•
installation of vibrating wire extensometers to measure displacements along time in sectors considered critical
as the permanent infrastructure;
•
a measurement program for in-situ stress parameter, to indicate sectors subject to large compression or
relaxation changes due to stress redistribution during drift mining;
•
preparation of procedures for a systematic convergence measurement and stress changes measurement; and
•
surface displacements monitoring based on visual inspection, cross-crack measurements (either manual or by
wireline extensometer), survey monitoring and satellite imaging subsidence monitoring (InSAR).
The application of pre-splitting
blasting process or smooth blasting processes should be investigated to reduce blast damage and achieve blast design.
Blasting should be avoided beside
drifts that have recently been backfilled or where the CRF still undergoing the curing process (28 days) to prevent CRF damage and affect the CRF stability in undercut operations.
A vibrations study is recommended to define the maximum size of blasting to reduce the risk of underground collapses or instabilities.
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The effect of blasting on the weak rock mass should be quantified using techniques proposed by Caceres
(2011) related to peak particle velocity and scaled distance as a function of rock mass quality.
A workshop should be organized to review the mine
plan and geotechnical assumptions to optimize the mine plan so as to ensure stability between drifts and mine levels.
For the portal excavation, a 2D
numerical model should be completed to assess stability and deformation during the excavation process. The model should consider the updated geotechnical characterization and assess these conditions at different excavation stages.
The total geotechnical program is estimated to cost approximately $455,000 to complete, detailed in Table 23-4 below.
Table 23-4: Recommended Geotechnical Program
Program Component
Unit Cost ($)
Vein/faults geotechnical characterization
40,000
Seismic hazard study update
50,000
Design stability update and pillar assessment
10,000
CRF test update
200,000
CRF limit equilibrium assessment
10,000
Geotechnical risk model
15,000
Support numerical analysis update
10,000
3D stability numerical analysis update
35,000
Detailed ground monitoring plan
10,000
Effect blasting assessment
10,000
Numerical model for portal excavation sequence
10,000
Mining and geotechnical workshop
25,000
Other studies
30,000
Total
455,000
23.6
Hydrology
Wellfield construction should be initiated and pumping tests conducted to confirm the water flow available from the water well. This work is estimated at
approximately $600,000.
23.7
Infrastructure
Detailed engineering and design should be carried out on the incoming power line, by the local power provider. The anticipated cost for this study is
approximately $100,000.
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23.8
Environmental Studies, Permitting and agreements with local individuals or groups
Continued engagement with the local community, tribal entities and local, state and federal agencies is recommended as the project nears final state
permitting, construction and operation. Costs associated with this recommendation are a part of ongoing engagement and already included in Owner’s costs.
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24
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Golder, 2019d: Stormwater Pollution Control Plan, Grassy Mountain Mine, Malheur County, Oregon. Prepared for
Calico Resources USA Corp. by Golder Associates inc. November 6, 2019.
Golder, 2020: Rock Mechanics Laboratory Testing Results (Grassy Mountain
Project), Reno, Nevada.
Golder, 2021a: Stormwater Pollution Control Plan, Grassy Mountain Mine, Malheur County, Oregon, Revision 1. Prepared for Calico
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Golder, 2021b: Abbreviated Operating Permit Application – Grassy Mountain
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and Minerals Industries by Golder Associates USA Inc. October 27, 2021.
Golder, 2021d: Detailed Design, Tailings Storage Facility and Temporary
Waste Rock Storage Facility, Grassy Mountain Mine, Malheur County, Oregon, Revision 1. Report prepared for Calico Resources USA Corp. by Golder Associates USA Inc., October 29, 2021.
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Gustin, M.M., Dyer, T.L., MacMahon, C., Caro, B., Raponi, T.R., and Baldwin, D., 2018: Preliminary Feasibility Study and Technical Report for the Grassy
Mountain Gold and Silver Project, Malheur County, Oregon, USA: report prepared by Mine Development Associates, Golder Associates and Ausenco Canada Inc. for Paramount Gold Nevada Corp., effective date 21 May, 2018.
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Jory, J.C., 1993: Grassy Mountain Development Geology 1993 Year-End Report: internal Newmont Exploration
Limited draft memorandum, December 1993, 9 p. plus figures.
Kelly, J.M., 1988: Discovery History of the Grassy Mountain Deposit: unpublished
inter-office correspondence of Atlas Precious Metals Inc., September 1988, 4 p.
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Technical Report: Report prepared for Seabridge Gold Inc., effective date April 27, 2007
MacMahon, C., Browne, R., and Barton, M., 2018: Draft
Report Pre-Feasibility Design Tailings Storage Facility Grassy Mountain Project: Report prepared by Golder Associates Inc., June 2018, 1633241.36. REVA, 30 p. plus appendices.
Mathews, 1981: Stability Graph Method: SME Mining Engineering Handbook, Third Edition, pp. 362–363.
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Palmström, A., 1995: RMi - A Rock Mass Characterization System for Rock Engineering Purposes: PhD
thesis, University of Oslo.
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Nevada Gold Corp., May 19, 2026.
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25
RELIANCE ON INFORMATION PROVIDED BY THE REGISTRAR
25.1
Introduction
The QPs have relied upon the following other expert reports, which provided information regarding mineral rights, surface rights, property agreements, water
rights, royalties, environmental, permitting, social license, closure, taxation and marketing for sections of this Report.
25.2
Property Agreements, Mineral Tenure, Surface Rights and Royalties
The QPs have not independently reviewed ownership of the Project area and any underlying property agreements, mineral tenure, surface rights, or royalties. The
QPs have fully relied upon information derived from Paramount and legal experts retained by Paramount for this information through the following documents:
•
Erwin, T.P., 2017: Mineral Status Report: report prepared by Erwin, Thompson & Faillers LLP for
Paramount Nevada Gold Corp., September 26, 2017, 9 p. plus appendices
The information relied upon falls under the category
“Legal matters” under § 229.1302(f).
This information is used to present the executive summary in Section 1 and the interpretation
and conclusions in Section 22. This information is used in discussing property ownership information in Section 3 of the Report, the tailings facility design in Section 15, the permitting and closure discussions in Section 17,
and in support of the economic analysis in Section 19. It also supports the Mineral Resource estimate in Section 11 and the Mineral Reserve estimate in Section 12.
25.3
Environmental, Permitting, Closure, and Social and Community Impact
The QPs have fully relied upon information supplied by Paramount and experts retained by Paramount for information related to design reports, baseline and
supporting studies for environmental permitting, environmental permitting and monitoring requirements, environmental characterization reports, ability to maintain and renew permits, emissions controls, closure planning, closure and reclamation
bonding and bonding requirements, sustainability accommodations.
The information relied upon falls within the categories “Environmental
matters” and “Accommodations the registrant commits or plans to provide to local individuals or groups in connection with its mine plans” under § 229.1302(f).
This information is used in the executive summary in Section 1 and when discussing the property ownership information in Section 3. It is also used
when discussing the permitting, closure plan and RCE in Section 17, and the economic analysis in Section 19. It supports the Mineral Resource estimate in Section 11 and the Mineral Reserve estimate in Section 12.
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25.4
Taxation
The QPs have fully relied upon information supplied by experts retained by Paramount for information related to taxation as applied to the financial model as
follows:
•
Werkman, D., 2026: Financial Model Rev A MNP Tax Edit: model prepared by MNP for Paramount Nevada Gold Corp.,
May 19, 2026.
The information relied upon falls within the category “Governmental Factors” under § 229.1302(f).
This information is used to present the executive summary in Section 1 and the interpretation and conclusions in Section 22. This information
is used in the economic analysis in Section 19 of the Report.
25.5
Markets
The QPs have not independently reviewed the marketing or contract information. The QPs have fully relied upon information derived from Paramount and experts
retained by Paramount for information relating to market studies/markets for product, market entry strategies, marketing and sales contracts, product valuations, product specifications, refining and treatment charges, agency relationships, material
contracts (e.g. mining, concentrating, smelting, refining, transportation, handling, sales and hedging, forward sales contracts or arrangements) and contract status (in place, renewals).
The information relied upon by the falls within the category of “Marketing Information and Plans” under § 229.1302(f).
This information is used to present the executive summary in Section 1 and the interpretation and conclusions in Section 22. This information is
used when discussing the market, commodity price and contract information in Section 16, and in the economic analysis in Section 19. It supports the Mineral Resource estimate in Section 11 and the Mineral Reserve estimate in
Section 12.
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APPENDIX A – CLAIMS LIST
Serial Number
Claim Name
County Number
Case Type
Location Date
Owner
Claims Group
Patent Number
36-2001-0141
Poison Springs 24
84-121773
Patented
05-04-84
Calico Resources
Grassy
36-2001-0141
36-2001-0141
Poison Springs 25
84-121774
Patented
05-03-84
Calico Resources
Grassy
36-2001-0141
36-2001-0141
Poison Springs 35
84-121775
Patented
04-05-85
Calico Resources
Grassy
36-2001-0141
ORMC106700
Winter Claim 33
88-20087
LODE
08-01-88
Cryla
Grassy
ORMC155919
Winter #1
2001-1031
LODE
02/18/2001
Cryla
Grassy
ORMC155920
Winter #2
2001-1032
LODE
02/18/2001
Cryla
Grassy
ORMC155921
Winter #3
2001-1033
LODE
02/18/2001
Cryla
Grassy
ORMC155922
Winter #4
2001-1034
LODE
02/18/2001
Cryla
Grassy
ORMC155923
Winter #5
2001-1035
LODE
02/18/2001
Cryla
Grassy
ORMC155924
Winter #6
2001-1036
LODE
02/18/2001
Cryla
Grassy
ORMC155925
Winter #7
2001-1037
LODE
02/18/2001
Cryla
Grassy
ORMC155926
Winter #8
2001-1038
LODE
02/18/2001
Cryla
Grassy
ORMC158876
Cryla #1
2004-2068
LODE
03/13/2004
Cryla
Grassy
ORMC158877
Cryla #2
2004-2069
LODE
03/13/2004
Cryla
Grassy
ORMC158878
Cryla #3
2004-2070
LODE
03/13/2004
Cryla
Grassy
ORMC158879
Cryla #4
2004-2071
LODE
03/13/2004
Cryla
Grassy
ORMC158880
Cryla #5
2004-2072
LODE
03/13/2004
Cryla
Grassy
ORMC158881
Cryla #6
2004-2073
LODE
03/13/2004
Cryla
Grassy
ORMC158882
Cryla #7
2004-2074
LODE
03/13/2004
Cryla
Grassy
ORMC158883
Cryla #8
2004-2075
LODE
03/13/2004
Cryla
Grassy
ORMC164789
Lucky Lucy #1
2009-3235
LODE
04-12-09
Cryla
Grassy
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Serial Number
Claim Name
County Number
Case Type
Location Date
Owner
Claims Group
Patent Number
ORMC164790
Lucky Lucy #2
2009-3236
LODE
04-12-09
Cryla
Grassy
ORMC164791
Lucky Lucy #3
2009-3237
LODE
04-12-09
Cryla
Grassy
ORMC164792
Lucky Lucy #4
2009-3238
LODE
04-12-09
Cryla
Grassy
ORMC164793
Lucky Lucy #5
2009-3239
LODE
04-12-09
Cryla
Grassy
ORMC164794
Lucky Lucy #6
2009-3240
LODE
04-12-09
Cryla
Grassy
ORMC164795
Lucky Lucy #7
2009-3241
LODE
04-12-09
Cryla
Grassy
ORMC164796
Lucky Lucy #8
2009-3242
LODE
04-12-09
Cryla
Grassy
ORMC164797
Lucky Lucy #9
2009-3243
LODE
04-12-09
Cryla
Grassy
ORMC164798
Lucky Lucy #10
2009-3244
LODE
04-12-09
Cryla
Grassy
ORMC76751
Winter Claim 32
84-122580
LODE
07-10-84
Cryla
Grassy
ORMC127904
Poison Springs 16A
90-1362
LODE
01/28/1990
Calico Resources
Grassy
ORMC127905
Poison Springs 17A
90-1363
LODE
01/28/1990
Calico Resources
Grassy
ORMC174063
PSR 1
2017-2056
LODE
03/30/2017
Calico Resources
Grassy
ORMC174064
PSR 2
2017-2057
LODE
03/29/2017
Calico Resources
Grassy
ORMC174065
PSR 3
2017-2058
LODE
03/29/2017
Calico Resources
Grassy
ORMC174066
PSR 4
2017-2059
LODE
03/29/2017
Calico Resources
Grassy
ORMC174067
PSR 5
2017-2060
LODE
03/29/2017
Calico Resources
Grassy
ORMC174068
PSR 6
2017-2061
LODE
03/29/2017
Calico Resources
Grassy
ORMC74965
Poison Springs #1
84-121750
LODE
05-01-84
Calico Resources
Grassy
ORMC74966
Poison Springs #2
84-121751
LODE
05-01-84
Calico Resources
Grassy
ORMC74967
Poison Springs #3
84-121752
LODE
05-01-84
Calico Resources
Grassy
ORMC74968
Poison Springs #4
84-121753
LODE
05-01-84
Calico Resources
Grassy
Grassy Mountain Project
S - K 1300 Technical Summary and Feasibility Report
Page 334
May 27, 2026
Serial Number
Claim Name
County Number
Case Type
Location Date
Owner
Claims Group
Patent Number
ORMC74969
Poison Springs #5
84-121754
LODE
05-01-84
Calico Resources
Grassy
ORMC74970
Poison Springs #6
84-121755
LODE
05-01-84
Calico Resources
Grassy
ORMC74971
Poison Springs #7
84-121756
LODE
05-01-84
Calico Resources
Grassy
ORMC74972
Poison Springs #8
84-121757
LODE
05-01-84
Calico Resources
Grassy
ORMC74973
Poison Springs #9
84-121758
LODE
05-01-84
Calico Resources
Grassy
ORMC74974
Poison Springs #10
84-121759
LODE
05-01-84
Calico Resources
Grassy
ORMC74975
Poison Springs #11
84-121760
LODE
05-01-84
Calico Resources
Grassy
ORMC74976
Poison Springs #12
84-121761
LODE
05-01-84
Calico Resources
Grassy
ORMC74977
Poison Springs #13
84-121762
LODE
05-02-84
Calico Resources
Grassy
ORMC74978
Poison Springs #14
84-121763
LODE
05-02-84
Calico Resources
Grassy
ORMC74979
Poison Springs #15
84-121764
LODE
05-02-84
Calico Resources
Grassy
ORMC74980
Poison Springs #16
90-1364
LODE
05-02-84
Calico Resources
Grassy
ORMC74981
Poison Springs #17
90-1365
LODE
05-02-84
Calico Resources
Grassy
ORMC74982
Poison Springs #18
84-121767
LODE
05-03-84
Calico Resources
Grassy
ORMC74983
Poison Springs #19
90-6119
LODE
05-03-84
Calico Resources
Grassy
ORMC74984
Poison Springs #20
90-6120
LODE
05-03-84
Calico Resources
Grassy
Grassy Mountain Project
S - K 1300 Technical Summary and Feasibility Report
Page 335
May 27, 2026
Serial Number
Claim Name
County Number
Case Type
Location Date
Owner
Claims Group
Patent Number
ORMC74985
Poison Springs #21
90-6121
LODE
05-03-84
Calico Resources
Grassy
ORMC74986
Poison Springs #22
84-121771
LODE
05-03-84
Calico Resources
Grassy
ORMC74987
Poison Springs #23
88-22375
LODE
05-03-84
Calico Resources
Grassy
ORMC74990
Poison Springs #26
84-121775
LODE
05/25/1984
Calico Resources
Grassy
ORMC74991
Poison Springs #27
84-121776
LODE
05/24/1984
Calico Resources
Grassy
ORMC74992
Poison Springs #28
84-121777
LODE
05/24/1984
Calico Resources
Grassy
ORMC74996
Poison Springs #32
84-121781
LODE
05/25/1984
Calico Resources
Grassy
ORMC82455
Poison Springs #36
88-22384
LODE
04-05-85
Calico Resources
Grassy
ORMC82456
Poison Springs #37
90-6130
LODE
04-05-85
Calico Resources
Grassy
ORMC104797
Frog #1
88-18804
LODE
05-06-88
Calico Resources
Grassy
ORMC104798
Frog #2
88-18805
LODE
05-06-88
Calico Resources
Grassy
ORMC104801
Frog #5
88-18808
LODE
05-06-88
Calico Resources
Grassy
ORMC104803
Frog #7
88-18809
LODE
05-06-88
Calico Resources
Grassy
ORMC104805
Frog #9
88-18811
LODE
05-06-88
Calico Resources
Grassy
ORMC104807
Frog #11
88-18813
LODE
05-06-88
Calico Resources
Grassy
ORMC104812
Frog #16
88-18819
LODE
05-06-88
Calico Resources
Grassy
ORMC104814
Frog #18
88-18821
LODE
05-06-88
Calico Resources
Grassy
ORMC104815
Frog #19
88-18822
LODE
05-06-88
Calico Resources
Grassy
ORMC104816
Frog #20
88-18823
LODE
05-06-88
Calico Resources
Grassy
ORMC104817
Frog #21
88-18824
LODE
05-06-88
Calico Resources
Grassy
ORMC104818
Frog #22
88-18825
LODE
05-06-88
Calico Resources
Grassy
Grassy Mountain Project
S - K 1300 Technical Summary and Feasibility Report
Page 336
May 27, 2026
Serial Number
Claim Name
County Number
Case Type
Location Date
Owner
Claims Group
Patent Number
ORMC104819
Frog #23
88-18826
LODE
05-06-88
Calico Resources
Grassy
ORMC104820
Frog #24
88-18827
LODE
05-06-88
Calico Resources
Grassy
ORMC104821
Frog #25
88-18828
LODE
05-07-88
Calico Resources
Grassy
ORMC104822
Frog #26
88-18829
LODE
05-07-88
Calico Resources
Grassy
ORMC104823
Frog #27
88-18830
LODE
05-07-88
Calico Resources
Grassy
ORMC104824
Frog #28
88-18831
LODE
05-07-88
Calico Resources
Grassy
ORMC104825
Frog #29
88-18832
LODE
05-07-88
Calico Resources
Grassy
ORMC104826
Frog #30
88-18833
LODE
05-07-88
Calico Resources
Grassy
ORMC104827
Frog #31
88-18834
LODE
05-07-88
Calico Resources
Grassy
ORMC104828
Frog #32
88-18835
LODE
05-07-88
Calico Resources
Grassy
ORMC104829
Frog #33
88-18836
LODE
05-07-88
Calico Resources
Grassy
ORMC104830
Frog #34
88-18837
LODE
05-07-88
Calico Resources
Grassy
ORMC104831
Frog #35
90-3396
LODE
05-07-88
Calico Resources
Grassy
ORMC104832
Frog #36
88-18839
LODE
05-07-88
Calico Resources
Grassy
ORMC104833
Frog #37
88-18840
LODE
05-07-88
Calico Resources
Grassy
ORMC104834
Frog #38
88-18841
LODE
05-07-88
Calico Resources
Grassy
ORMC104835
Frog #39
88-18842
LODE
05-07-88
Calico Resources
Grassy
ORMC104836
Frog #40
88-18843
LODE
05-07-88
Calico Resources
Grassy
ORMC104837
Frog #41
88-18844
LODE
05-07-88
Calico Resources
Grassy
ORMC104838
Frog #42
88-18845
LODE
05-07-88
Calico Resources
Grassy
ORMC104839
Frog #46
88-18846
LODE
05-07-88
Calico Resources
Grassy
ORMC104840
Frog #47
88-18847
LODE
05-07-88
Calico Resources
Grassy
ORMC104841
Frog #48
88-18848
LODE
05-07-88
Calico Resources
Grassy
ORMC104878
Frog #85
90-1366
LODE
05-08-88
Calico Resources
Grassy
ORMC104879
Frog #86
90-1367
LODE
05-08-88
Calico Resources
Grassy
Grassy Mountain Project
S - K 1300 Technical Summary and Feasibility Report
Page 337
May 27, 2026
Serial Number
Claim Name
County Number
Case Type
Location Date
Owner
Claims Group
Patent Number
ORMC104880
Frog #87
90-1368
LODE
05-08-88
Calico Resources
Grassy
ORMC104881
Frog #88
90-1369
LODE
05-08-88
Calico Resources
Grassy
ORMC104882
Frog #89
90-1370
LODE
05-08-88
Calico Resources
Grassy
ORMC104883
Frog #90
90-1371
LODE
05-08-88
Calico Resources
Grassy
ORMC104884
Frog #91
90-1372
LODE
05-08-88
Calico Resources
Grassy
ORMC104885
Frog #92
90-1373
LODE
05-08-88
Calico Resources
Grassy
ORMC104886
Frog #93
88-18893
LODE
05-08-88
Calico Resources
Grassy
ORMC104887
Frog #94
88-18894
LODE
05-08-88
Calico Resources
Grassy
ORMC104889
Frog #96
88-18896
LODE
05/17/1988
Calico Resources
Grassy
ORMC104891
Frog #98
88-18898
LODE
05/17/1988
Calico Resources
Grassy
ORMC104900
Frog #107
88-18907
LODE
05/20/1988
Calico Resources
Grassy
ORMC104901
Frog #108
88-18908
LODE
05/20/1988
Calico Resources
Grassy
ORMC104902
Frog #109
88-18909
LODE
05/20/1988
Calico Resources
Grassy
ORMC104903
Frog #110
88-18910
LODE
05/20/1988
Calico Resources
Grassy
ORMC104904
Frog #111
88-18911
LODE
05/20/1988
Calico Resources
Grassy
ORMC104905
Frog #112
88-18912
LODE
05/19/1988
Calico Resources
Grassy
ORMC104906
Frog #113
88-18913
LODE
05/19/1988
Calico Resources
Grassy
ORMC104926
Frog #133
88-18933
LODE
05/20/1988
Calico Resources
Grassy
ORMC104927
Frog #134
88-18934
LODE
05/20/1988
Calico Resources
Grassy
ORMC104928
Frog #135
88-18935
LODE
05/20/1988
Calico Resources
Grassy
ORMC104929
Frog #136
88-18936
LODE
05/20/1988
Calico Resources
Grassy
ORMC104940
Frog #147
88-18947
LODE
05/22/1988
Calico Resources
Grassy
ORMC104941
Frog #148
88-18948
LODE
05/22/1988
Calico Resources
Grassy
ORMC104942
Frog #149
88-18949
LODE
05/22/1988
Calico Resources
Grassy
ORMC104943
Frog #150
88-18950
LODE
05/22/1988
Calico Resources
Grassy
Grassy Mountain Project
S - K 1300 Technical Summary and Feasibility Report
Page 338
May 27, 2026
Serial Number
Claim Name
County Number
Case Type
Location Date
Owner
Claims Group
Patent Number
ORMC104960
Frog #167
88-18967
LODE
05/19/1988
Calico Resources
Grassy
ORMC104961
Frog #168
88-18968
LODE
05/19/1988
Calico Resources
Grassy
ORMC104962
Frog #169
88-18969
LODE
05/19/1988
Calico Resources
Grassy
ORMC104963
Frog #170
88-18970
LODE
05/19/1988
Calico Resources
Grassy
ORMC104964
Frog #171
88-18971
LODE
05/19/1988
Calico Resources
Grassy
ORMC104965
Frog #172
88-18972
LODE
05/19/1988
Calico Resources
Grassy
ORMC104966
Frog #173
88-18973
LODE
05/19/1988
Calico Resources
Grassy
ORMC104967
Frog #174
88-18974
LODE
05/19/1988
Calico Resources
Grassy
ORMC104968
Frog #175
88-18975
LODE
05/19/1988
Calico Resources
Grassy
ORMC104969
Frog #176
88-18976
LODE
05/19/1988
Calico Resources
Grassy
ORMC104988
Frog #195
88-18995
LODE
05/22/1988
Calico Resources
Grassy
ORMC104989
Frog #196
88-18996
LODE
05/22/1988
Calico Resources
Grassy
ORMC104990
Frog #197
88-18997
LODE
05/22/1988
Calico Resources
Grassy
ORMC104991
Frog #198
88-18998
LODE
05/21/1988
Calico Resources
Grassy
ORMC105000
Frog #207
88-19007
LODE
05/29/1988
Calico Resources
Grassy
ORMC105001
Frog #208
88-19008
LODE
05/29/1988
Calico Resources
Grassy
ORMC105002
Frog #209
88-19009
LODE
05/29/1988
Calico Resources
Grassy
ORMC105003
Frog #210
88-19010
LODE
05/24/1988
Calico Resources
Grassy
ORMC105004
Frog #211
88-19011
LODE
05/27/1988
Calico Resources
Grassy
ORMC105005
Frog #212
88-19012
LODE
05/27/1988
Calico Resources
Grassy
ORMC105006
Frog #213
88-19013
LODE
05/27/1988
Calico Resources
Grassy
ORMC105007
Frog #214
88-19014
LODE
05/27/1988
Calico Resources
Grassy
ORMC105008
Frog #215
88-19015
LODE
05/27/1988
Calico Resources
Grassy
ORMC105009
Frog #216
88-19016
LODE
05/27/1988
Calico Resources
Grassy
ORMC105017
Frog #224
88-19024
LODE
05/26/1988
Calico Resources
Grassy
Grassy Mountain Project
S - K 1300 Technical Summary and Feasibility Report
Page 339
May 27, 2026
Serial Number
Claim Name
County Number
Case Type
Location Date
Owner
Claims Group
Patent Number
ORMC105019
Frog #226
88-19026
LODE
05/26/1988
Calico Resources
Grassy
ORMC105021
Frog #228
88-19028
LODE
05/26/1988
Calico Resources
Grassy
ORMC105023
Frog #230
88-19030
LODE
05/26/1988
Calico Resources
Grassy
ORMC105025
Frog #232
88-19032
LODE
05/26/1988
Calico Resources
Grassy
ORMC105913
Frog #252
88-19861
LODE
07/21/1988
Calico Resources
Grassy
ORMC107597
Frog #649
88-21299
LODE
08/17/1988
Calico Resources
Grassy
ORMC107598
Frog #650
88-21300
LODE
08/17/1988
Calico Resources
Grassy
ORMC107599
Frog #651
88-21301
LODE
08/17/1988
Calico Resources
Grassy
ORMC107600
Frog #652
88-21302
LODE
08/17/1988
Calico Resources
Grassy
ORMC107703
Frog #755
88-21405
LODE
08/23/1988
Calico Resources
Grassy
ORMC107704
Frog #756
88-21406
LODE
08/23/1988
Calico Resources
Grassy
ORMC108077
Don #1
88-22025
MILLSITE
09/28/1988
Calico Resources
Grassy
ORMC108078
Don #2
88-22026
MILLSITE
09/28/1988
Calico Resources
Grassy
ORMC108079
Don #3
88-22027
MILLSITE
09/28/1988
Calico Resources
Grassy
ORMC108080
Don #4
88-22028
MILLSITE
09/28/1988
Calico Resources
Grassy
ORMC108081
Don #5
88-22029
MILLSITE
09/28/1988
Calico Resources
Grassy
ORMC108082
Don #6
88-22030
MILLSITE
09/28/1988
Calico Resources
Grassy
ORMC108083
Don #7
88-22031
MILLSITE
09/28/1988
Calico Resources
Grassy
ORMC108084
Don #8
88-22032
MILLSITE
09/28/1988
Calico Resources
Grassy
ORMC108085
Don #9
88-22033
MILLSITE
09/28/1988
Calico Resources
Grassy
ORMC108086
Frog #10A
88-22228
LODE
09/28/1988
Calico Resources
Grassy
ORMC108087
Frog #25A
88-22229
LODE
09/27/1988
Calico Resources
Grassy
ORMC108088
Frog #26A
88-22230
LODE
09/27/1988
Calico Resources
Grassy
ORMC108089
Frog #35A
88-22231
LODE
09/27/1988
Calico Resources
Grassy
ORMC108090
Frog #46A
88-22232
LODE
09/27/1988
Calico Resources
Grassy
Grassy Mountain Project
S - K 1300 Technical Summary and Feasibility Report
Page 340
May 27, 2026
Serial Number
Claim Name
County Number
Case Type
Location Date
Owner
Claims Group
Patent Number
ORMC108091
Frog #46B
88-22233
LODE
09/27/1988
Calico Resources
Grassy
ORMC125178
Frog #151
89-38517
LODE
10-04-89
Calico Resources
Grassy
ORMC126210
Frog #3
89-39554
LODE
10/29/1989
Calico Resources
Grassy
ORMC126212
Frog #1274
89-39556
LODE
10/27/1989
Calico Resources
Grassy
ORMC126213
Frog #1275
89-39557
LODE
10/27/1989
Calico Resources
Grassy
ORMC126215
Frog #1277
89-39559
LODE
10/27/1989
Calico Resources
Grassy
ORMC146318
Poison Spring 1A
93-6060
LODE
07/19/1993
Calico Resources
Grassy
ORMC146319
Poison Spring 3A
93-6061
LODE
07/19/1993
Calico Resources
Grassy
ORMC146320
Poison Spring 5A
93-6062
LODE
07/20/1993
Calico Resources
Grassy
ORMC146321
Poison Spring 6A
93-6063
LODE
07/20/1993
Calico Resources
Grassy
ORMC146322
Poison Spring 7A
93-6064
LODE
07/18/1993
Calico Resources
Grassy
ORMC146323
Poison Spring 8A
93-6065
LODE
07/18/1993
Calico Resources
Grassy
ORMC146324
Poison Spring 9A
93-6066
LODE
07/19/1993
Calico Resources
Grassy
ORMC146325
Poison Spring 11A
93-6067
LODE
07/19/1993
Calico Resources
Grassy
ORMC146326
Poison Spring 14A
93-6068
LODE
07/18/1993
Calico Resources
Grassy
ORMC146327
Poison Spring 18A
93-6069
LODE
07/18/1993
Calico Resources
Grassy
ORMC146328
Poison Spring 22A
93-6070
LODE
07/18/1993
Calico Resources
Grassy
ORMC146329
Poison Spring 26A
93-6071
LODE
07/18/1993
Calico Resources
Grassy
Grassy Mountain Project
S - K 1300 Technical Summary and Feasibility Report
Page 341
May 27, 2026
Serial Number
Claim Name
County Number
Case Type
Location Date
Owner
Claims Group
Patent Number
ORMC146330
Poison Spring 27A
93-6072
LODE
07/19/1993
Calico Resources
Grassy
ORMC146331
Poison Spring 38A
93-6073
LODE
07/18/1993
Calico Resources
Grassy
ORMC167998
GM 5058
2011-3790
LODE
09/15/2011
Calico Resources
Grassy
ORMC167999
GM 5059
2011-3791
LODE
09/15/2011
Calico Resources
Grassy
ORMC168000
GM 5060
2011-3792
LODE
09/15/2011
Calico Resources
Grassy
ORMC168001
GM 5061
2011-3793
LODE
09/15/2011
Calico Resources
Grassy
ORMC168002
GM 5062
2011-3794
LODE
09/15/2011
Calico Resources
Grassy
ORMC168003
GM 5063
2011-3795
LODE
09/17/2011
Calico Resources
Grassy
ORMC168004
GM 5064
2011-3796
LODE
09/17/2011
Calico Resources
Grassy
ORMC168005
GM 5065
2011-3797
LODE
09/17/2011
Calico Resources
Grassy
ORMC168006
GM 5066
2011-3798
LODE
09/17/2011
Calico Resources
Grassy
ORMC168007
GM 5067
2011-3799
LODE
09/17/2011
Calico Resources
Grassy
ORMC168008
GM 5068
2011-3800
LODE
09/17/2011
Calico Resources
Grassy
ORMC168009
GM 5069
2011-3801
LODE
09/17/2011
Calico Resources
Grassy
ORMC168010
GM 5070
2011-3802
LODE
09/17/2011
Calico Resources
Grassy
ORMC168011
GM 5071
2011-3803
LODE
09/17/2011
Calico Resources
Grassy
ORMC168012
GM 5072
2011-3804
LODE
09/17/2011
Calico Resources
Grassy
ORMC168013
GM 5150
2011-3805
LODE
09/15/2011
Calico Resources
Grassy
ORMC168014
GM 5151
2011-3806
LODE
09/15/2011
Calico Resources
Grassy
ORMC168015
GM 5152
2011-3807
LODE
09/15/2011
Calico Resources
Grassy
ORMC168016
GM 5153
2011-3808
LODE
09/15/2011
Calico Resources
Grassy
ORMC168017
GM 5154
2011-3809
LODE
09/15/2011
Calico Resources
Grassy
ORMC168018
GM 5155
2011-3810
LODE
09/15/2011
Calico Resources
Grassy
ORMC168019
GM 5156
2011-3811
LODE
09/15/2011
Calico Resources
Grassy
Grassy Mountain Project
S - K 1300 Technical Summary and Feasibility Report
Page 342
May 27, 2026
Serial Number
Claim Name
County Number
Case Type
Location Date
Owner
Claims Group
Patent Number
ORMC168020
GM 5157
2011-3812
LODE
09/15/2011
Calico Resources
Grassy
ORMC168021
GM 5158
2011-3813
LODE
09/15/2011
Calico Resources
Grassy
ORMC168022
GM 5159
2011-3814
LODE
09/15/2011
Calico Resources
Grassy
ORMC168023
GM 5160
2011-3815
LODE
09/15/2011
Calico Resources
Grassy
ORMC168024
GM 5161
2011-3816
LODE
09/15/2011
Calico Resources
Grassy
ORMC168025
GM 5162
2011-3817
LODE
09/15/2011
Calico Resources
Grassy
ORMC168026
GM 5163
2011-3818
LODE
09/17/2011
Calico Resources
Grassy
ORMC168027
GM 5164
2011-3819
LODE
09/17/2011
Calico Resources
Grassy
ORMC168028
GM 5165
2011-3820
LODE
09/17/2011
Calico Resources
Grassy
ORMC168029
GM 5166
2011-3821
LODE
09/17/2011
Calico Resources
Grassy
ORMC168030
GM 5167
2011-3822
LODE
09/17/2011
Calico Resources
Grassy
ORMC168031
GM 5168
2011-3823
LODE
09/17/2011
Calico Resources
Grassy
ORMC168032
GM 5169
2011-3824
LODE
09/17/2011
Calico Resources
Grassy
ORMC168033
GM 5170
2011-3825
LODE
09/17/2011
Calico Resources
Grassy
ORMC168034
GM 5171
2011-3826
LODE
09/17/2011
Calico Resources
Grassy
ORMC168035
GM 5172
2011-3827
LODE
09/17/2011
Calico Resources
Grassy
ORMC168036
GM 5250
2011-3828
LODE
09/15/2011
Calico Resources
Grassy
ORMC168037
GM 5251
2011-3829
LODE
09/15/2011
Calico Resources
Grassy
ORMC168038
GM 5252
2011-3830
LODE
09/15/2011
Calico Resources
Grassy
ORMC168039
GM 5253
2011-3831
LODE
09/15/2011
Calico Resources
Grassy
ORMC168040
GM 5254
2011-3832
LODE
09/15/2011
Calico Resources
Grassy
ORMC168041
GM 5255
2011-3833
LODE
09/15/2011
Calico Resources
Grassy
ORMC168042
GM 5256
2011-3834
LODE
09/15/2011
Calico Resources
Grassy
ORMC168043
GM5257
2011-3835
LODE
09/15/2011
Calico Resources
Grassy
ORMC168044
GM 5258
2011-3836
LODE
09/15/2011
Calico Resources
Grassy
Grassy Mountain Project
S - K 1300 Technical Summary and Feasibility Report
Page 343
May 27, 2026
Serial Number
Claim Name
County Number
Case Type
Location Date
Owner
Claims Group
Patent Number
ORMC168045
GM 5259
2011-3837
LODE
09/15/2011
Calico Resources
Grassy
ORMC168046
GM 5260
2011-3838
LODE
09/15/2011
Calico Resources
Grassy
ORMC168047
GM 5261
2011-3839
LODE
09/16/2011
Calico Resources
Grassy
ORMC168048
GM 5262
2011-3840
LODE
09/16/2011
Calico Resources
Grassy
ORMC168049
GM 5263
2011-3841
LODE
09/16/2011
Calico Resources
Grassy
ORMC168050
GM 5264
2011-3842
LODE
09/16/2011
Calico Resources
Grassy
ORMC168051
GM 5265
2011-3843
LODE
09/16/2011
Calico Resources
Grassy
ORMC168052
GM 5266
2011-3844
LODE
09/16/2011
Calico Resources
Grassy
ORMC168053
GM 5267
2011-3845
LODE
09/23/2011
Calico Resources
Grassy
ORMC168054
GM 5268
2011-3846
LODE
09/23/2011
Calico Resources
Grassy
ORMC168055
GM 5269
2011-3847
LODE
09/23/2011
Calico Resources
Grassy
ORMC168056
GM 5270
2011-3848
LODE
09/23/2011
Calico Resources
Grassy
ORMC168057
GM 5271
2011-3849
LODE
09/23/2011
Calico Resources
Grassy
ORMC168058
GM 5272
2011-3850
LODE
09/23/2011
Calico Resources
Grassy
ORMC168059
GM 5273
2011-3851
LODE
09/23/2011
Calico Resources
Grassy
ORMC168060
GM 5274
2011-3852
LODE
09/23/2011
Calico Resources
Grassy
ORMC168061
GM 5275
2011-3853
LODE
09/23/2011
Calico Resources
Grassy
ORMC168062
GM 5276
2011-3854
LODE
09/23/2011
Calico Resources
Grassy
ORMC168063
GM 5352
2011-3855
LODE
09/15/2011
Calico Resources
Grassy
ORMC168064
GM 5353
2011-3856
LODE
09/15/2011
Calico Resources
Grassy
ORMC168065
GM 5354
2011-3857
LODE
09/15/2011
Calico Resources
Grassy
ORMC168066
GM 5355
2011-3858
LODE
09/15/2011
Calico Resources
Grassy
ORMC168067
GM 5356
2011-3859
LODE
09/15/2011
Calico Resources
Grassy
ORMC168068
GM 5357
2011-3860
LODE
09/15/2011
Calico Resources
Grassy
ORMC168069
GM 5358
2011-3861
LODE
09/15/2011
Calico Resources
Grassy
Grassy Mountain Project
S - K 1300 Technical Summary and Feasibility Report
Page 344
May 27, 2026
Serial Number
Claim Name
County Number
Case Type
Location Date
Owner
Claims Group
Patent Number
ORMC168070
GM 5359
2011-3862
LODE
09/15/2011
Calico Resources
Grassy
ORMC168071
GM 5360
2011-3863
LODE
09/15/2011
Calico Resources
Grassy
ORMC168072
GM 5361
2011-3864
LODE
09/16/2011
Calico Resources
Grassy
ORMC168073
GM 5362
2011-3865
LODE
09/16/2011
Calico Resources
Grassy
ORMC168074
GM 5363
2011-3866
LODE
09/16/2011
Calico Resources
Grassy
ORMC168075
GM 5364
2011-3867
LODE
09/16/2011
Calico Resources
Grassy
ORMC168076
GM 5365
2011-3868
LODE
09/16/2011
Calico Resources
Grassy
ORMC168077
GM 5366
2011-3869
LODE
09/16/2011
Calico Resources
Grassy
ORMC168078
GM 5367
2011-3870
LODE
09/23/2011
Calico Resources
Grassy
ORMC168079
GM 5368
2011-3871
LODE
09/23/2011
Calico Resources
Grassy
ORMC168080
GM 5369
2011-3872
LODE
09/23/2011
Calico Resources
Grassy
ORMC168081
GM 5370
2011-3873
LODE
09/23/2011
Calico Resources
Grassy
ORMC168082
GM 5371
2011-3874
LODE
09/23/2011
Calico Resources
Grassy
ORMC168083
GM 5372
2011-3875
LODE
09/23/2011
Calico Resources
Grassy
ORMC168084
GM 5373
2011-3876
LODE
09/23/2011
Calico Resources
Grassy
ORMC168085
GM 5374
2011-3877
LODE
09/23/2011
Calico Resources
Grassy
ORMC168086
GM 5375
2011-3878
LODE
09/23/2011
Calico Resources
Grassy
ORMC168087
GM 5376
2011-3879
LODE
09/23/2011
Calico Resources
Grassy
ORMC168088
GM 5452
2011-3880
LODE
09/19/2011
Calico Resources
Grassy
ORMC168089
GM 5453
2011-3881
LODE
09/19/2011
Calico Resources
Grassy
ORMC168090
GM 5454
2011-3882
LODE
09/19/2011
Calico Resources
Grassy
ORMC168091
GM 5455
2011-3883
LODE
09/19/2011
Calico Resources
Grassy
ORMC168092
GM 5552
2011-3884
LODE
09/19/2011
Calico Resources
Grassy
ORMC168093
GM 5553
2011-3885
LODE
09/19/2011
Calico Resources
Grassy
ORMC168094
GM 5554
2011-3886
LODE
09/19/2011
Calico Resources
Grassy
Grassy Mountain Project
S - K 1300 Technical Summary and Feasibility Report
Page 345
May 27, 2026
Serial Number
Claim Name
County Number
Case Type
Location Date
Owner
Claims Group
Patent Number
ORMC168095
GM 5555
2011-3887
LODE
09/19/2011
Calico Resources
Grassy
ORMC168096
GM 5580
2011-3888
LODE
09/23/2011
Calico Resources
Grassy
ORMC168097
GM 5581
2011-3889
LODE
09/23/2011
Calico Resources
Grassy
ORMC168098
GM 5582
2011-3890
LODE
09/23/2011
Calico Resources
Grassy
ORMC168099
GM 5583
2011-3891
LODE
09/23/2011
Calico Resources
Grassy
ORMC168100
GM 5584
2011-3892
LODE
09/23/2011
Calico Resources
Grassy
ORMC168101
GM 5652
2011-3893
LODE
09/18/2011
Calico Resources
Grassy
ORMC168102
GM 5653
2011-3894
LODE
09/18/2011
Calico Resources
Grassy
ORMC168103
GM 5654
2011-3895
LODE
09/18/2011
Calico Resources
Grassy
ORMC168104
GM 5655
2011-3896
LODE
09/18/2011
Calico Resources
Grassy
ORMC168105
GM 5680
2011-3897
LODE
09/22/2011
Calico Resources
Grassy
ORMC168106
GM 5681
2011-3898
LODE
09/22/2011
Calico Resources
Grassy
ORMC168107
GM 5682
2011-3899
LODE
09/22/2011
Calico Resources
Grassy
ORMC168108
GM 5683
2011-3900
LODE
09/22/2011
Calico Resources
Grassy
ORMC168109
GM 5684
2011-3901
LODE
09/22/2011
Calico Resources
Grassy
ORMC168110
GM 5752
2011-3902
LODE
09/18/2011
Calico Resources
Grassy
ORMC168111
GM 5753
2011-3903
LODE
09/18/2011
Calico Resources
Grassy
ORMC168112
GM 5754
2011-3904
LODE
09/18/2011
Calico Resources
Grassy
ORMC168113
GM 5755
2011-3905
LODE
09/18/2011
Calico Resources
Grassy
ORMC168114
GM 5756
2011-3906
LODE
09/25/2011
Calico Resources
Grassy
ORMC168115
GM 5757
2011-3907
LODE
09/25/2011
Calico Resources
Grassy
ORMC168116
GM 5758
2011-3908
LODE
09/25/2011
Calico Resources
Grassy
ORMC168117
GM 5780
2011-3909
LODE
09/22/2011
Calico Resources
Grassy
ORMC168118
GM 5781
2011-3910
LODE
09/22/2011
Calico Resources
Grassy
ORMC168119
GM 5782
2011-3911
LODE
09/22/2011
Calico Resources
Grassy
Grassy Mountain Project
S - K 1300 Technical Summary and Feasibility Report
Page 346
May 27, 2026
Serial Number
Claim Name
County Number
Case Type
Location Date
Owner
Claims Group
Patent Number
ORMC168120
GM 5783
2011-3912
LODE
09/22/2011
Calico Resources
Grassy
ORMC168121
GM 5784
2011-3913
LODE
09/22/2011
Calico Resources
Grassy
ORMC168122
GM 5785
2011-3914
LODE
09/22/2011
Calico Resources
Grassy
ORMC168123
GM 5786
2011-3915
LODE
09/22/2011
Calico Resources
Grassy
ORMC168124
GM 5787
2011-3916
LODE
09/22/2011
Calico Resources
Grassy
ORMC168125
GM 5852
2011-3917
LODE
09/24/2011
Calico Resources
Grassy
ORMC168126
GM 5853
2011-3918
LODE
09/24/2011
Calico Resources
Grassy
ORMC168127
GM 5854
2011-3919
LODE
09/24/2011
Calico Resources
Grassy
ORMC168128
GM 5855
2011-3920
LODE
09/24/2011
Calico Resources
Grassy
ORMC168129
GM 5856
2011-3921
LODE
09/24/2011
Calico Resources
Grassy
ORMC168130
GM 5857
2011-3922
LODE
09/24/2011
Calico Resources
Grassy
ORMC168131
GM 5858
2011-3923
LODE
09/24/2011
Calico Resources
Grassy
ORMC168132
GM 5859
2011-3924
LODE
09/24/2011
Calico Resources
Grassy
ORMC168133
GM 5860
2011-3925
LODE
09/24/2011
Calico Resources
Grassy
ORMC168134
GM 5861
2011-3926
LODE
09/24/2011
Calico Resources
Grassy
ORMC168135
GM 5862
2011-3927
LODE
09/24/2011
Calico Resources
Grassy
ORMC168136
GM 5863
2011-3928
LODE
09/24/2011
Calico Resources
Grassy
ORMC168137
GM 5864
2011-3929
LODE
09/24/2011
Calico Resources
Grassy
ORMC168138
GM 5885
2011-3930
LODE
09/22/2011
Calico Resources
Grassy
ORMC168139
GM 5886
2011-3931
LODE
09/22/2011
Calico Resources
Grassy
ORMC168140
GM 5887
2011-3932
LODE
09/22/2011
Calico Resources
Grassy
ORMC168141
GM 5956
2011-3933
LODE
09/24/2011
Calico Resources
Grassy
ORMC168142
GM 5957
2011-3934
LODE
09/24/2011
Calico Resources
Grassy
ORMC168143
GM 5958
2011-3935
LODE
09/24/2011
Calico Resources
Grassy
ORMC168144
GM 5959
2011-3936
LODE
09/24/2011
Calico Resources
Grassy
Grassy Mountain Project
S - K 1300 Technical Summary and Feasibility Report
Page 347
May 27, 2026
Serial Number
Claim Name
County Number
Case Type
Location Date
Owner
Claims Group
Patent Number
ORMC168145
GM 5960
2011-3937
LODE
09/24/2011
Calico Resources
Grassy
ORMC168146
GM 5961
2011-3938
LODE
09/24/2011
Calico Resources
Grassy
ORMC168147
GM 5962
2011-3939
LODE
09/24/2011
Calico Resources
Grassy
ORMC168148
GM 5974
2011-3940
LODE
09/21/2011
Calico Resources
Grassy
ORMC168149
GM 5975
2011-3941
LODE
09/21/2011
Calico Resources
Grassy
ORMC168150
GM 5976
2011-3942
LODE
09/21/2011
Calico Resources
Grassy
ORMC168151
GM 5985
2011-3943
LODE
09/22/2011
Calico Resources
Grassy
ORMC168152
GM 5986
2011-3944
LODE
09/22/2011
Calico Resources
Grassy
ORMC168153
GM 5987
2011-3945
LODE
09/22/2011
Calico Resources
Grassy
ORMC168154
GM 6056
2011-3946
LODE
09/24/2011
Calico Resources
Grassy
ORMC168155
GM 6057
2011-3947
LODE
09/24/2011
Calico Resources
Grassy
ORMC168156
GM 6058
2011-3948
LODE
09/24/2011
Calico Resources
Grassy
ORMC168157
GM 6059
2011-3949
LODE
09/24/2011
Calico Resources
Grassy
ORMC168158
GM 6060
2011-3950
LODE
09/24/2011
Calico Resources
Grassy
ORMC168159
GM 6061
2011-3951
LODE
09/24/2011
Calico Resources
Grassy
ORMC168160
GM 6062
2011-3952
LODE
09/24/2011
Calico Resources
Grassy
ORMC168161
GM 6069
2011-3953
LODE
09/21/2011
Calico Resources
Grassy
ORMC168162
GM 6070
2011-3954
LODE
09/21/2011
Calico Resources
Grassy
ORMC168163
GM 6071
2011-3955
LODE
09/21/2011
Calico Resources
Grassy
ORMC168164
GM 6072
2011-3956
LODE
09/21/2011
Calico Resources
Grassy
ORMC168165
GM 6073
2011-3957
LODE
09/21/2011
Calico Resources
Grassy
ORMC168166
GM 6074
2011-3958
LODE
09/21/2011
Calico Resources
Grassy
ORMC168167
GM 6075
2011-3959
LODE
09/21/2011
Calico Resources
Grassy
ORMC168168
GM 6076
2011-3960
LODE
09/21/2011
Calico Resources
Grassy
ORMC168169
GM 6077
2011-3961
LODE
09/21/2011
Calico Resources
Grassy
Grassy Mountain Project
S - K 1300 Technical Summary and Feasibility Report
Page 348
May 27, 2026
Serial Number
Claim Name
County Number
Case Type
Location Date
Owner
Claims Group
Patent Number
ORMC168170
GM 6085
2011-3962
LODE
09/21/2011
Calico Resources
Grassy
ORMC168171
GM 6086
2011-3963
LODE
09/21/2011
Calico Resources
Grassy
ORMC168172
GM 6087
2011-3964
LODE
09/21/2011
Calico Resources
Grassy
ORMC168173
GM 6156
2011-3965
LODE
09/24/2011
Calico Resources
Grassy
ORMC168174
GM 6157
2011-3966
LODE
09/24/2011
Calico Resources
Grassy
ORMC168175
GM 6158
2011-3967
LODE
09/24/2011
Calico Resources
Grassy
ORMC168176
GM 6159
2011-3968
LODE
09/24/2011
Calico Resources
Grassy
ORMC168177
GM 6160
2011-3969
LODE
09/24/2011
Calico Resources
Grassy
ORMC168178
GM 6161
2011-3970
LODE
09/24/2011
Calico Resources
Grassy
ORMC168179
GM 6162
2011-3971
LODE
09/24/2011
Calico Resources
Grassy
ORMC168180
GM 6174
2011-3972
LODE
09/21/2011
Calico Resources
Grassy
ORMC168181
GM 6175
2011-3973
LODE
09/21/2011
Calico Resources
Grassy
ORMC168182
GM 6176
2011-3974
LODE
09/21/2011
Calico Resources
Grassy
ORMC168183
GM 6177
2011-3975
LODE
09/21/2011
Calico Resources
Grassy
ORMC168184
GM 6178
2011-3976
LODE
09/21/2011
Calico Resources
Grassy
ORMC168185
GM 6179
2011-3977
LODE
09/21/2011
Calico Resources
Grassy
ORMC168186
GM 6180
2011-3978
LODE
09/21/2011
Calico Resources
Grassy
ORMC168187
GM 6181
2011-3979
LODE
09/21/2011
Calico Resources
Grassy
ORMC168188
GM 6182
2011-3980
LODE
09/21/2011
Calico Resources
Grassy
ORMC168189
GM 6183
2011-3981
LODE
09/21/2011
Calico Resources
Grassy
ORMC168190
GM 6184
2011-3982
LODE
09/21/2011
Calico Resources
Grassy
ORMC168191
GM 6185
2011-3983
LODE
09/21/2011
Calico Resources
Grassy
ORMC168192
GM 6186
2011-3984
LODE
09/21/2011
Calico Resources
Grassy
ORMC168193
GM 6187
2011-3985
LODE
09/21/2011
Calico Resources
Grassy
ORMC168194
GM 6258
2011-3986
LODE
09/21/2011
Calico Resources
Grassy
Grassy Mountain Project
S - K 1300 Technical Summary and Feasibility Report
Page 349
May 27, 2026
Serial Number
Claim Name
County Number
Case Type
Location Date
Owner
Claims Group
Patent Number
ORMC168195
GM 6259
2011-3987
LODE
09/21/2011
Calico Resources
Grassy
ORMC168196
GM 6260
2011-3988
LODE
09/21/2011
Calico Resources
Grassy
ORMC168197
GM 6261
2011-3989
LODE
09/21/2011
Calico Resources
Grassy
ORMC168198
GM 6262
2011-3990
LODE
09/21/2011
Calico Resources
Grassy
ORMC168199
GM 6263
2011-3991
LODE
09/21/2011
Calico Resources
Grassy
ORMC168200
GM 6264
2011-3992
LODE
09/21/2011
Calico Resources
Grassy
ORMC168201
GM 6265
2011-3993
LODE
09/21/2011
Calico Resources
Grassy
ORMC168202
GM 6266
2011-3994
LODE
09/21/2011
Calico Resources
Grassy
ORMC168203
GM 6267
2011-3995
LODE
09/21/2011
Calico Resources
Grassy
ORMC168204
GM 6268
2011-3996
LODE
09/21/2011
Calico Resources
Grassy
ORMC168205
GM 6271
2011-3997
LODE
09/20/2011
Calico Resources
Grassy
ORMC168206
GM 6272
2011-3998
LODE
09/20/2011
Calico Resources
Grassy
ORMC168207
GM 6273
2011-3999
LODE
09/20/2011
Calico Resources
Grassy
ORMC168208
GM 6274
2011-4000
LODE
09/20/2011
Calico Resources
Grassy
ORMC168209
GM 6275
2011-4001
LODE
09/20/2011
Calico Resources
Grassy
ORMC168210
GM 6276
2011-4002
LODE
09/20/2011
Calico Resources
Grassy
ORMC168211
GM 6277
2011-4003
LODE
09/20/2011
Calico Resources
Grassy
ORMC168212
GM 6278
2011-4004
LODE
09/20/2011
Calico Resources
Grassy
ORMC168213
GM 6279
2011-4005
LODE
09/20/2011
Calico Resources
Grassy
ORMC168214
GM 6280
2011-4006
LODE
09/20/2011
Calico Resources
Grassy
ORMC168215
GM 6281
2011-4007
LODE
09/22/2011
Calico Resources
Grassy
ORMC168216
GM 6282
2011-4008
LODE
09/22/2011
Calico Resources
Grassy
ORMC168217
GM 6283
2011-4009
LODE
09/22/2011
Calico Resources
Grassy
ORMC168218
GM 6284
2011-4010
LODE
09/22/2011
Calico Resources
Grassy
ORMC168219
GM 6285
2011-4011
LODE
09/22/2011
Calico Resources
Grassy
Grassy Mountain Project
S - K 1300 Technical Summary and Feasibility Report
Page 350
May 27, 2026
Serial Number
Claim Name
County Number
Case Type
Location Date
Owner
Claims Group
Patent Number
ORMC168220
GM 6286
2011-4012
LODE
09/22/2011
Calico Resources
Grassy
ORMC168221
GM 6287
2011-4013
LODE
09/22/2011
Calico Resources
Grassy
ORMC168222
GM 6358
2011-4014
LODE
09/21/2011
Calico Resources
Grassy
ORMC168223
GM 6359
2011-4015
LODE
09/21/2011
Calico Resources
Grassy
ORMC168224
GM 6360
2011-4016
LODE
09/21/2011
Calico Resources
Grassy
ORMC168225
GM 6361
2011-4017
LODE
09/21/2011
Calico Resources
Grassy
ORMC168226
GM 6362
2011-4018
LODE
09/21/2011
Calico Resources
Grassy
ORMC168227
GM 6363
2011-4019
LODE
09/21/2011
Calico Resources
Grassy
ORMC168228
GM 6364
2011-4020
LODE
09/21/2011
Calico Resources
Grassy
ORMC168229
GM 6365
2011-4021
LODE
09/21/2011
Calico Resources
Grassy
ORMC168230
GM 6366
2011-4022
LODE
09/21/2011
Calico Resources
Grassy
ORMC168231
GM 6367
2011-4023
LODE
09/21/2011
Calico Resources
Grassy
ORMC168232
GM 6368
2011-4024
LODE
09/21/2011
Calico Resources
Grassy
ORMC168233
GM 6371
2011-4025
LODE
09/20/2011
Calico Resources
Grassy
ORMC168234
GM 6372
2011-4026
LODE
09/20/2011
Calico Resources
Grassy
ORMC168235
GM 6373
2011-4027
LODE
09/20/2011
Calico Resources
Grassy
ORMC168236
GM 6374
2011-4028
LODE
09/20/2011
Calico Resources
Grassy
ORMC168237
GM 6375
2011-4029
LODE
09/20/2011
Calico Resources
Grassy
ORMC168238
GM 6376
2011-4030
LODE
09/20/2011
Calico Resources
Grassy
ORMC168239
GM 6377
2011-4031
LODE
09/20/2011
Calico Resources
Grassy
ORMC168240
GM 6378
2011-4032
LODE
09/20/2011
Calico Resources
Grassy
ORMC168241
GM 6379
2011-4033
LODE
09/20/2011
Calico Resources
Grassy
ORMC168242
GM 6380
2011-4034
LODE
09/20/2011
Calico Resources
Grassy
ORMC168243
GM 6381
2011-4035
LODE
09/22/2011
Calico Resources
Grassy
ORMC168244
GM 6382
2011-4036
LODE
09/22/2011
Calico Resources
Grassy
Grassy Mountain Project
S - K 1300 Technical Summary and Feasibility Report
Page 351
May 27, 2026
Serial Number
Claim Name
County Number
Case Type
Location Date
Owner
Claims Group
Patent Number
ORMC168245
GM 6383
2011-4037
LODE
09/22/2011
Calico Resources
Grassy
ORMC168246
GM 6384
2011-4038
LODE
09/22/2011
Calico Resources
Grassy
ORMC168247
GM 6385
2011-4039
LODE
09/22/2011
Calico Resources
Grassy
ORMC168248
GM 6386
2011-4040
LODE
09/22/2011
Calico Resources
Grassy
ORMC168249
GM 6387
2011-4041
LODE
09/22/2011
Calico Resources
Grassy
ORMC174048
PGM 1
2017-2062
LODE
03/29/2017
Calico Resources
Grassy
ORMC174049
PGM 2
2017-2063
LODE
03/29/2017
Calico Resources
Grassy
ORMC174050
PGM 3
2017-2064
LODE
03/31/2017
Calico Resources
Grassy
ORMC174051
PGM 4
2017-2065
LODE
03/30/2017
Calico Resources
Grassy
ORMC174052
PGM 5
2017-2066
LODE
03/30/2017
Calico Resources
Grassy
ORMC174053
PGM 6
2017-2067
LODE
03/31/2017
Calico Resources
Grassy
ORMC174054
PGM 7
2017-2068
LODE
03/31/2017
Calico Resources
Grassy
ORMC174055
PGM 8
2017-2069
LODE
03/31/2017
Calico Resources
Grassy
ORMC174056
PGM 9
2017-2070
LODE
03/31/2017
Calico Resources
Grassy
ORMC174057
PGM 10
2017-2071
LODE
03/30/2017
Calico Resources
Grassy
ORMC174058
PGM 11
2017-2072
LODE
03/29/2017
Calico Resources
Grassy
ORMC174059
PGM 12
2017-2073
LODE
03/29/2017
Calico Resources
Grassy
ORMC174060
PGM 13
2017-2074
LODE
03/29/2017
Calico Resources
Grassy
ORMC174061
PGM 14
2017-2075
LODE
03/29/2017
Calico Resources
Grassy
ORMC174062
PGM 15
2017-2076
LODE
03/29/2017
Calico Resources
Grassy
Grassy Mountain Project
S - K 1300 Technical Summary and Feasibility Report
Page 352
May 27, 2026
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Boolean flag that is true when the Form 8-K filing is intended to satisfy the filing obligation of the registrant as pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act.
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Boolean flag that is true when the Form 8-K filing is intended to satisfy the filing obligation of the registrant as pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act.
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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Name of the Exchange on which a security is registered.
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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Boolean flag that is true when the Form 8-K filing is intended to satisfy the filing obligation of the registrant as soliciting material pursuant to Rule 14a-12 under the Exchange Act.
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Boolean flag that is true when the Form 8-K filing is intended to satisfy the filing obligation of the registrant as written communications pursuant to Rule 425 under the Securities Act.
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