Selkirk Copper Announces Positive PEA for the Minto Project, Delivering After-Tax NPV of C$494M with 48% IRR Strong Platform to Realize Concentrate Production by 2028 2026 Minto Project Preliminary Economic Assessment Highlights
- Target Mine Life, Mill Throughput, and Robust Economics Across Commodity Price Scenarios 13 year mine life at 4,100 tonnes per day (“tpd”) mining-milling rate that produces peak 27,200 t o copper-equivalent 1 contained in concentrate or 48,700 t of high-grade copper-gold-silver concentrate at peak production NPV7% of C$494M, 47.8% internal rate of return (“IRR”), and 1.9 year after-tax payback from o first production at US$5.00/lb copper, US$3,600/oz gold and US$50/oz silver (“Planning Prices”) NPV7% of C$1,023M, 78.2% IRR, and 1.3 year after-tax payback from first production at o US$6.50/lb copper, US$4,300/oz gold and US$65/oz silver (“Spot Prices”)
NPV7% of C$1,385M, 96.3% IRR, and 1.0 year after-tax payback from first production at o US$7.50/lb copper, US$5,400/oz gold and US$75/oz silver (“Upside Prices”)
- Capital Efficient Leveraging Existing Infrastructure The Project demonstrates a strong Capital Efficiency Ratio2 with an after-tax NPV to initial o capital ratio of 2.7:1 at Planning Prices, increasing to 5.5:1 at Spot Prices highlighting leverage to higher copper, gold and silver prices. The high capital efficiency ratio is a result of road, barge facilities, power transmission line, substation, fuel farm, services, camp, warehouse, workshops, grinding and milling infrastructure, water treatment plant, existing underground development, and general on-site services that are in good working order requiring negligible capital investment to make operational Mine Life-to-Payback2, a ratio which describes the potential for the asset to return capital and o provide exposure to positive copper supply-demand fundamentals through the planned mine, is 6.8:1 at Planning Prices
- Exploration Growth Potential Beyond Current Study Phase 1 52,288 metre drill program completed in April 2026 increased Measured & Indicated o Resources in the 2026 Mineral Resource Estimate (“MRE”) by 280% and increased contained copper, gold, and silver by 182%, 184% and 188% respectively above the 2025 Mineral Resource Estimate Phase 2 50,000 metre drill program initiated in May 2026 is now 98% complete, the results of o which are not included in the 2026 MRE or 2026 PEA mine plan but which continue to extend and expand zones of known mineralization reinforcing significant upside mine life and production potential
- Water Management and Permitting In designing the Minto Project restart, significant attention was placed on ensuring all of the o planned development work and planned operations, including water management, would be within the boundary of the existing Quartz Mining License and would minimize impact on the environment. The Minto Project restart design has also benefitted from input from the Selkirk First Nation. In addition, the upcoming amended permit applications, to be submitted in Q4 2026, do not expect to request or make notable changes to the discharge criteria and requirements currently set for the site The Company believes that by confining development and operating plans to the Quartz Mining o License area, by making no significant changes to water discharge criteria, and by working closely with the Selkirk First Nation, the assessment of the amended permit applications can proceed in a
timely manner
- Potential for First Concentrate Production in 2028 Preliminary execution planning, including permitting, underground mine development, and site o preparations, supports the potential to deliver first concentrate production in H2 2028 with fullramp up in mining, milling, and concentrate production by H1 2029 The Company recognizes that it is pursuing a restart plan that requires timely delivery of several o scopes of work, including the timely review and elaboration of permit amendment applications, however each scope of work has been assessed in the PEA and the Company has been wellsupported by the Selkirk First Nation, suppliers and service providers, specialist contractors, and by the Yukon Government which we expect to continue during the next phase of work
September 22, 2026 - Vancouver, BC and Pelly Crossing, YT – Selkirk Copper Mines Inc. (TSX- V:SCMI | FRA:IO20 | OTCQX:SKRKF) (“Selkirk Copper” or the “Company”) is pleased to announce positive economic results of a Preliminary Economic Assessment (the “PEA” or the “Study”) for its coppergold-silver Minto Project (the “Project”) located in Yukon, Canada. The PEA provides an in-depth technical and economic assessment of the restart of open pit and underground mining operations, crushing, grinding and flotation operations, and concentrate production activities and outlines a potential pathway to development of a longer-life operation with additional copper-gold-silver concentrate production dependant on further exploration success.
M. Colin Joudrie, President & CEO, commented: “Over the past 12 months the team has delivered exceptional results across all aspects of our restart plan from resource discovery, expansion and definition, resource modeling, integrated mine planning, project definition, engineering and design, capital and operating cost estimation, permitting, and Selkirk First Nation engagement. The positive economics described in the PEA create the platform for the Company to pursue a restart decision at the completion of a Feasibility Study and permit amendment receipt in H2-2027 with targeted first concentrate production by H2-2028. The level of detail developed in the PEA study, including integrated mine plans, equipment definition, and detailed capital, operating and sustaining cost estimations, has increased our confidence in our ability to deliver on our focused restart timeline.
We look forward to initiating Feasibility Study work and submission of our permit amendment application in late 2026 followed by another MRE Update expected in Q1 2027 which will include results from our Phase 2 50,000 m drill program which is nearing completion.
Our entire team recognizes the importance of timely completion of several scopes of work to achieve our restart plan however we are buoyed by the positive outcome of the Phase 1 and Phase 2 drill program, positive restart economics reflected in the PEA, and the opportunity to breathe new life into an asset that has much more to give.”
Preliminary Economic Assessment Overview
The Preliminary Economic Assessment was prepared by a team of independent industry experts, led by Hatch Ltd. (“Hatch”) and supported by SRK Consulting (Canada) Inc. (“SRK”), Fuse Advisors (Part of SLR) (“Fuse”), Moose Mountain Technical Services (“MMTS”), and Ensero Solutions (“Ensero”). Scott Fulton, P.Eng., VP Engineering for the Company and a non-independent Qualified Person as defined by National Instrument 43-101, has supervised the preparation of this news release and approved the scientific and technical information herein. References to dollars represent Canadian Dollars ($) unless otherwise specified. Abbreviations for thousands (“k”) and millions (“M”) are used for brevity. The Company intends to file the complete PEA Technical Report on its website (www.selkirkcopper.com) and SEDAR+ (www.sedarplus.ca) within 45 days of this press release.
Measured & Indicated Resources and Inferred Resources described in the 2026 Mineral Resource Estimate (effective date June 10, 2026) are 47.8 million tonnes at 0.89% copper, 0.34 g/t gold, and 3.2 g/t silver totaling 940 million pounds copper, 530,000 ounces gold, and 4.97 million ounces silver and 16.9 million tonnes at 0.76% copper, 0.26 g/t gold, and 2.7 g/t silver totalling 281 million pounds copper, 142,000 ounces gold, and 1.5 million ounces silver respectively. Applying the proposed development plan described in the PEA results in a mineable inventory of ~18.4 Mt being generated, from both open pit and underground sources, which results in a planned initial mine life of 13 years. The PEA is preliminary in nature and includes Inferred Mineral Resources that are considered too speculative geologically to have economic considerations applied that would enable these resources to be categorized as Mineral Reserves. There is no certainty that the projections in the PEA will be realized. Mineral Resources which are not Mineral Reserves do not have demonstrated economic viability.
The PEA has been designed to constrain surface and underground development work and above ground installations and infrastructure to that which can be located within the boundary of the existing Quartz Mining License (“QML”) over the entire planned initial 13 year mine life.
The Project is based on a 4,100 tpd mining and processing plant operating rate which includes extraction of mineralized material from two (2) primary underground mining areas, two (2) open pits, feeding blended mine material into a new crushing circuit, which then feeds into an existing semi-autogenous and ball mill grinding circuit. Copper-gold-silver bearing minerals are recovered through a new gravity circuit and an existing flotation circuit designed to produce a single copper-gold-silver concentrate product.
The PEA considers production of conventional slurry tailings initially placed into previously mined-out pits with a newly designed and engineered retaining dam to be constructed along a portion of the pit edge, then transitioning to a new dry-stack tailings process part way through the mine life. The new PEA dry-stack tailings storage is located at the western margin of the QML. The planned transition to dry-stack tailings is being pursued to reduce impact to the environment.
The initial capital costs (“Capex”) of the Project, including working capital requirements, owner’s costs, and contingency commensurate for the level of study, is estimated to be C$186 million. Sustaining capital costs (“Susex”) over the life of mine is estimated to be C$409 million, including a scoping-level estimate of closure and rehabilitation.
Operating costs (“Opex”) over the life of mine are estimated at C$1,764 million, encompassing mining, processing, tailings, water treatment, site general and administrative costs, and logistics required to support planned production throughout the operation’s life. Operating costs are estimated to average C$95.77 per tonne milled over the life of mine, with underground mining representing the largest component of unit costs.
Sustaining capital costs over the life of mine are estimated at C$409 million, encompassing underground mine development, mobile equipment replacement, infrastructure renewal, and other capital investments required to maintain the planned production profile and operational performance designed for in the PEA. Sustaining costs are inclusive of the scoping-level estimate of closure and rehabilitation costs expected to be incurred after production operations have ceased.
Scoping-level closure and rehabilitation plans, which follow the completion of mining and processing operations, include recontouring, covering, and revegetating necessary areas, deconstruction of structures, rehabilitation of disturbed surface areas, environmental closure, long-term stabilization activities, water and condition monitoring, and necessary logistics to execute these activities.
Net Smelter Return (“NSR”) estimates were developed and used for open pit optimizations, underground stope development, and classification of mineralized material to be fed to the process plant. NSR estimates used the same assumed metal prices (“Design Prices”) as those used to calculate the 2026 MRE, which are US$4.60/lb copper, US$3,300/oz gold, and US$40/oz silver. The NSR values represent the estimated recovered and payable metal value after deductions for treatment and refining charges, transportation and royalties. Prices, recoveries, payabilities and cost deductions were applied consistently across all material types included in the development of open pit and underground mine plans and mineral processing plans. Payabilities, charges, and deduction schedules follow industry‑typical concentrate contract structures for copper‑gold-silver concentrates. A 1.5% NSR royalty payable to the Selkirk First Nation was applied to all payable metals.
The PEA considers submission and elaboration of a permit amendment application to the Yukon Environmental Socio-economic Assessment Board (“YESAB”) as well as various other permit applications and amendments in support of exploration, development, and site-specific activities necessary to support planned construction activities and restart of mining, milling and concentrate producing operations. The product of mining and mineral processing activities is a high-grade copper-gold-silver concentrate with a target average grade of 38.0% copper, 12-18 g/t gold, and 100-150 g/t silver with negligible deleterious elements, representing a premium-quality concentrate that compares favourably to the highest-quality copper concentrates produced in the world today. Peak copper-equivalent1 contained in concentrate over the planned initial life of mine is 27,200 tonnes per annum (“tpa”), resulting in 48,700 tpa of high-grade (38% Cu) copper concentrate. Metal contained in mill feed material over the planned initial life of mine is approximately 434 Mlbs of copper, 271 koz of gold, and 2.36 Moz of silver or 653 Mlbs copperequivalent1. Payable metal contained in concentrate over the planned initial life of mine is approximately 377 Mlbs of copper, 225 koz of gold, and 1.39 Moz of silver, or 552 Mlbs copper-equivalent1.
The Project study work, underpinned by a successful 52,288 metre Phase 1 exploration, resource expansion, and resource definition drill program and updated MRE, has resulted in a 13 year mine life. The results from an ongoing Phase 2 50,000 m program, that is nearing completion, have not been incorporated into the PEA but will be incorporated into a Feasibility Study expected to start in Q4 2026.
Economic analysis for the PEA was completed using Planning Prices of US$5.00/lb copper, US$3,600/oz gold, and US$50/oz silver, whereas Design Prices which informed the MRE and mineable inventory estimates were US$4.60/lb copper, US$3,300/oz gold, and US$40/oz silver.
Economics for the Minto Project, applying Planning Prices and a 7% discount rate result in an after-tax NPV7% of C$494M and after-tax internal rate of return of 47.8%. Due to the relatively low initial capital cost of C$186M estimated to re-establish production, the after-tax payback period from first production is approximately 1.9 years.
At Spot Prices of US$6.50/lb copper, US$4,300/oz gold and US$65/oz silver, which represent a rounded average of the quarter-to-date daily cash metal prices quoted on the London Metal Exchange, the after-tax NPV7% increases to C$1,023M, the internal rate of return increases to 78.2%, and the after-tax payback period from first production reduces to 1.3 years.
At Upside Prices, which are reflective of potential future commodity prices as a results of a number of fundamental supply-demand factors in copper and increasing interest by global financial institutions and governments in gold and silver as financial instruments, of US$7.50/lb copper, US$5,400/oz gold and US$75/oz silver, the after-tax NPV7% further increases to C$1,385M, the internal rate of return increases to 96.3%, and the after-tax payback period from first production decreases to 1.0 years.
In descending order, the Minto Project restart economics are most sensitive to: i) copper price; ii) CAD:USD foreign exchange rate; iii) copper recovery; iv) gold price; and v) operating costs. In addition, project returns are sensitive to mine construction execution timelines and overall investment returns are sensitive to permitting timelines.
Reflective of the style and character of the mineralization and the mineralized lenses that comprise the Minto Project, economics of the restart are highly leveraged to copper and gold prices.
Table 1: Minto Project PEA Summary at Planning Prices
| PEA Summary Financial Inputs | Units | Values | |
|---|---|---|---|
| Planning Price Assumptions | |||
| Copper Price | US$/lb | 5.00 | |
| Gold Price | US$/oz | 3,600 | |
| Silver Price | US$/oz | 50.00 | |
| Exchange Rate | CAD:USD | 0.72 | |
| Discount Rate | % | 7 |
| Key Metrics – Life of Mine (LOM) | |||
|---|---|---|---|
| Mine Life | Years | 13.0 | |
| Tonnes Milled | Mt | 18.4 | |
| Open Pit Strip Ratio | W:O | 7.9 | |
| Daily Mill Throughput | tpd | 4,100 | |
| Annual Mill Throughput | Mtpa | 1.5 | |
| Contained Metal in Mill Feed | |||
| Copper | Mlbs | 434 | |
| Gold | koz | 271 | |
| Silver | Moz | 2.4 | |
| Copper-equivalent1 | Mlbs | 653 | |
| Processed Feed Grades | |||
| Copper | % | 1.07 | |
| Gold | g/t | 0.46 | |
| Silver | g/t | 4.00 | |
| Oxide Ratio | % | 7.5 | |
| Copper-equivalent1 | % | 1.61 | |
| Estimated Metal Recoveries: | |||
| Copper | % | 88.7 | |
| Gold | % | 84.6 | |
| Silver | % | 77.3 |
| Operating Costs (LOM Average) | |||
|---|---|---|---|
| Underground Mining | C$/t milled | 34.47 | |
| Open Pit Mining | C$/t milled | 12.20 | |
| Processing | C$/t milled | 15.89 | |
| G&A | C$/t milled | 24.47 | |
| Tailings, Environment, and Water | C$/t milled | 8.74 | |
| Total On-Site Operating Costs | C$/t milled | 95.77 | |
| Concentrate Shipping | C$/t wet concentrate | 342 | |
| Copper C1 Net of By-Product Credits2 | US$/lb | 1.53 | |
| Copper-equivalent1 Cash Operating Costs2 | US$/lb CuEq1 | 2.63 |
| Capital Costs | |||
|---|---|---|---|
| Initial Capital Cost (incl. Contingency) | C$M | 185.9 |
Sustaining Capital Cost (incl. Closure) C$M 409.3
| Project Economics | |||
|---|---|---|---|
| Pre-Tax NPV @ 7% | C$M | 742.6 | |
| After-Tax NPV @ 7% | C$M | 493.9 | |
| Pre-Tax IRR | % | 54.8 | |
| After-Tax IRR | % | 47.8 | |
| After-Tax Payback from First Production | Years | 1.9 | |
| Capital Efficiency Ratio | - | 2.7 |
Table 2: Minto Project PEA Economic Sensitivity
| Downside | Planning | Spot | Upside | ||
|---|---|---|---|---|---|
| Copper Price (US$/lb) | 3.50 | 5.00 | 6.50 | 7.50 | |
| Gold Price (US$/oz) | 2,500 | 3,600 | 4,300 | 5,400 | |
| Silver Price (US$/oz) | 35.00 | 50.00 | 65.00 | 75.00 | |
| Copper TC | RCs (US$/t | US$/lb) | 35 | 0.035 | 35 | 0.035 | (186) | (0.186) | (186) | (0.186) | |
| After Tax NPV 7% (C$M) | 10 | 494 | 1,023 | 1,385 | |
| After Tax IRR (%) | 9 | 48 | 78 | 96 | |
| Payback from First Production (years) | 6.5 | 1.9 | 1.3 | 1.0 |
The PEA is preliminary in nature and includes Inferred Mineral Resources that are considered too speculative geologically to have economic considerations applied that would enable these resources to be categorized as Mineral Reserves. There is no certainty that the projections in the PEA will be realized. Mineral Resources which are not Mineral Reserves do not have demonstrated economic viability.
Infrastructure
One of the features of the Minto Project, as an integrated mining and milling operation that produced high grade copper concentrates as recently as May 2023, is the substantial surface infrastructure that is available and in place to enable a low-cost restart of operations. Selkirk Copper’s engineering and design team and site care and maintenance team, supported by a wide range of third-party experts including those from Hatch, SRK, Fuse, and others, have completed detailed assessments of the usability of site infrastructure and existing equipment. These assessments have determined that the majority of this infrastructure is in good working order requiring only minor attention and refurbishment. Work on repairs and refurbishments has been ongoing since Q3 2025 in an effort to allow activities during the Capex phase to be focused on the critical path items.
Listed below are those installations, equipment, and facilities that are not expected to require significant additional investment.
Existing Installation, Equipment and Facilities Surface (General) Airstrip •
- Existing accommodations • Mobile equipment wash-bay
- Kitchen and dining hall • Gymnasium
- Main power supply line and substation Process Plant
- Maintenance shops (mechanical and • 1 x Semi-Autogenous Grinding Mill electrical)
- 2 x Ball Mills
- Warehouse
- Cyclones
- Concentrate storage shed
- Flotation cells (multi-stages)
- Emergency response and First Aid Building
- Concentrate thickening and filtration
- Mine and site operations offices
- Tailings thickening
- Fuel storage and dispensing facility (diesel
- Reagent storage building
and gasoline)
- Assay laboratory
- Propane storage (multiple locations)
- Concentrate storage facility
- 3 x Diesel generators
- Tailings building
- Explosives magazine facility
Water and Tailings Management
- Potable water treatment plant
- Water treatment plant
- Waste disposal sites
- Changing facilities (the “dry”)
New or significantly rehabilitated or re-established infrastructure, equipment, or facilities necessary for the restart of mining, milling and concentrate production activities are listed below.
New Installations, Equipment and Facilities
Surface (General)
- Sumps
- 3 x new diesel generators • New underground mine at Minto North
- Portal access road and staging area
- Upgraded dining facilities
- 1,500 m of horizontal development
Surface Mining
- 2 x open pit mining areas including pre- o 250 m x 3 m diameter ventilation raise and secondary egress escapeways stripping, access and haul roads, set-back areas, and water diversion structures
- Ventilation and underground utilities
1 x primary waste rock management facility •
- Sumps
for Ridgetop and 118 Open Pits and
Crushing Circuit
underground waste
- Three-stage crushing and screening circuit
Underground Mining
- Mill feed laydown and blending area
- Rehabilitation of the existing
Concentrate, Tailings and Water underground mine Management
- Main fresh air fan (located on surface)
- Concentrate dryer (screw conveyor/dryer)
- Main return air raise
- Tailings cyclones
- Secondary egress escapeways
- Dry-stack tailings filtration building and
- Underground ventilation distribution, related handling facility services and utilities
The PEA modelled Capex period runs from July 1, 2027 until June 30, 2028. Items and costs expected to be incurred before the start of the Capex period (“Pre-Capex”) have been excluded from the scope of the PEA and the resultant economic analysis and deemed to be sunk costs. Costs for significant items expected to be incurred in whole or in part during the Pre-Capex period include: dewatering, physical rehabilitation, and re-servicing of the existing underground; ongoing water treatment; deposits for fixed and mobile equipment; refurbishment of two existing backup diesel generators; and other regular site care & maintenance activities.
Mineral Resource Summary
The Mineral Resources at the Minto Project, described in the updated 2026 Mineral Resource Estimate, are comprised of open pit and underground Measured & Indicated (“M&I”) Mineral Resources of 47.8 million tonnes at 0.89% copper, 0.34 g/t gold, and 3.2 g/t silver totaling 940 million pounds copper, 530,000 ounces gold, and 4.97 million ounces silver which represent a 182%, 184% and 188% increase respectively in contained metals above the previous 2025 MRE. The 2026 Measured & Indicated Resources include 26.0 million tonnes of underground resources at 1.14% copper, 0.49 g/t gold, and 4.4 g/t silver; and 21.8 million tonnes of open pit resources at 0.59% copper, 0.17 g/t gold, and 1.8 g/t silver.
In addition, the Minto Project has combined open pit and underground Inferred Mineral Resources of 16.9 million tonnes at 0.76% copper, 0.26 g/t gold, and 2.7 g/t silver containing 281 million pounds copper, 142,000 ounces gold, and 1.5 million ounces silver. Inferred Mineral Resources are considered too speculative geologically to have the economic considerations applied to them that would enable them to be categorized as Mineral Reserves.
Mineralization in several of the zones and lenses across the central mine area remain open laterally and at depth and there are several high potential drill targets for follow-up in future exploration, definition and delineation work.
The ongoing 50,000 metre Phase 2 drill program is 98% complete, the results of which have not been included in the PEA. Initial assay results and visual drill logs continue to show expansion potential across each of the mineralized zones in the central mine area. The results of the Phase 2 drill program will be incorporated into an updated MRE scheduled for completion in Q1 2027, which will form the basis of an updated set of integrated mines plans in a Feasibility Study scheduled to commence in Q4 2026.
Table 3: Current Mineral Resource Estimate
| Type | Cutoff | Class | ROM | In situ Grades | Metal | |||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| (CDN$) | Tonnage | NSR | Cu | Au | Ag | Ox | ASCu | Cu | Au | Ag | ||||||||||||||
| (000) | (CDN$) | (%) | (gpt) | (gpt) | Ratio | (%) | (Mlbs) | (Koz) | (Koz) | |||||||||||||||
| Open Pit | $30 | Indicated | 21,779 | $80.63 | 0.59 | 0.17 | 1.8 | 0.11 | 0.073 | 283 | 122 | 1,294 | ||||||||||||
| Inferred | 7,052 | $74.61 | 0.55 | 0.13 | 1.6 | 0.08 | 0.048 | 85 | 30 | 354 | ||||||||||||||
| UG | $80 | Measured | 348 | $153.47 | 0.92 | 0.39 | 3.3 | 0.05 | 0.041 | 7 | 4 | 36 | ||||||||||||
| Indicated | 25,679 | $189.20 | 1.15 | 0.49 | 4.4 | 0.06 | 0.067 | 650 | 404 | 3,638 | ||||||||||||||
| Meas + Ind | 26,027 | $188.72 | 1.15 | 0.49 | 4.4 | 0.06 | 0.070 | 657 | 408 | 3,674 | ||||||||||||||
| Inferred | 9,812 | $146.57 | 0.91 | 0.36 | 3.5 | 0.05 | 0.044 | 196 | 112 | 1,113 | ||||||||||||||
| Total | Varies as Above | Meas + Ind | 47,806 | $139.48 | 0.89 | 0.34 | 3.2 | 0.08 | 0.070 | 940 | 530 | 4,969 | ||||||||||||
| Inferred | 16,865 | $116.48 | 0.76 | 0.26 | 2.7 | 0.06 | 0.046 | 281 | 142 | 1,467 |
Notes to Table 3:
1. The MRE has been completed by Sue Bird of Moose Mountain Technical Services (MMTS).
2. The effective date of the resource is June 10, 2026
3. Resources are reported using the 2014 CIM Definition Standards and were estimated using the 2019 CIM Best Practices Guidelines.
4. For the Net Smelter Proceeds (NSP) calculations:
- Metal prices are USD$4.60/lb Cu, USD$3,300/oz Au, USD$40/oz Ag;
- A currency exchange rate of 0.72 US$ per CDN$;
- 97.5% payable Cu, 98% payable Au and 92% payable Ag; and the following inputs:
- Concentrate grade of 38% Cu with a moisture content of 8%;
- Unit deductions of 1gpt Au, 30gpt Ag;
- Offsite costs (refining, transport and insurance) of US$200/dmt;
- Treatment for Cu Charges of USD$35, Refining Charges of USD$0.035/lb payable Cu, USD$5.00/oz Au and USD$0.50/oz Ag;
- Royalties of 1.5% NSR.
5. Recoveries are as follows:
- CuRecov – 95.5%+1.07*Cu%-113*(ASCu/TCu), with a maximum of 98%
- AuRecov = 35.63+0.58032*Curecov-1.3341*Cu%^ 0.8932, with a maximum of 85%
- AgRecov = 69.4+1.9*Aggpt, to a maximum of 85%
6. These inputs result in the following NSR and CuEq equations:
- NSR = CDN$CuNSP*CuRecov*Cu%*22.0462 + CDN$AuNSP*AuRecov*Augpt + CD$AgNSP*AgRecov*Aggpt)/31.10348
- CuEq = NSR/(CuNSP*CuRecov*22.0462)
7. The Mineral Resource has been confined by a “reasonable prospects of eventual economic extraction” pit or underground shape using the 130% base case NSR for the Ridgetop and Area 118 open pits and by confining shapes for the underground.
8. Mining costs are CDN$4.58/tonne for open pit, marginal mining costs of CDN$50/tonne for underground, Processing costs are CDN$30/tonne milled, and G&A costs are CDN$20/tonne milled.
9. Pit slope angles are assumed at 45º.
10. The specific gravity of the deposit has been assigned based on domain as between 2.578 and 2.842 based on sg measurements in the Minto deposit.
11. Oxide Ratio = (ASCu)/ (Total Copper)
12. Numbers may not add due to rounding.
13. Mineral Resources which are not Mineral Reserves do not have demonstrated economic viability.
Mining Overview
The PEA considers both open-pit and underground mining designed to extract the copper-gold-silver mineralization defined in the 2026 MRE. The resource comprises multiple shallow-dipping metamorphosed copper-gold-silver mineralized lenses distributed across the Ridgetop and Area 118 open pit domains, and the Minto East, Minto North, Copper Keel and Area 118 underground domains. Historically, underground mining has taken place in Copper Keel and Minto East domains accessed from one primary underground portal and decline located between the planned Ridgetop and Area 118 open pits.
Figure 1: Site Plan Including Existing and Planned New Mining and Development
The PEA adopts a mining approach that combines open pit and underground mining methods to best align with the geometry, metallurgical characteristics, and development sequence of the Minto deposits. Underground mining is planned to provide the entire mill feed in the initial years of operation, with open pit mining introduced later in the mine life as the Ridgetop and then Area 118 open pits are developed. Open pit mining will contribute mill feed from the open pit deposits using contractor‑operated truck‑shovel operations, deploying selective flitch mining to maintain grade control across thin, structurally complex near‑surface lenses.
Underground mining will be carried out in the Minto North, Minto East, Copper Keel, and Area 118 deposits using longhole open stoping in an upper-cut retreat sequence with rib pillars. Following commencement of open pit mining, underground and open pit mining will operate in tandem, with material blended from the different deposits to support metallurgical performance and maintain process plant feed quality. Both the open pit and underground mining method closely align with historical practices at the Minto Project and reflect the integration of updated geotechnical parameters, stope dimensions and pillar criteria developed for the restart.
Table 4: PEA LOM Mineable Inventory Summary
| Mining Area | Tonnes | Copper | Gold | Silver | Oxide Ratio | ||||
|---|---|---|---|---|---|---|---|---|---|
| (%) | (g/t) | (g/t) | (%) | ||||||
| Open Pit Combined | 6,021,881 | 0.83% | 0.25 | 2.64 | 13% | ||||
| Ridgetop | 5,627,794 | 0.82% | 0.26 | 2.69 | 13% | ||||
| Area 118 Open Pit | 394,087 | 0.96% | 0.09 | 1.84 | 13% |
| Underground Combined | 12,352,286 | 1.19% | 0.56 | 4.67 | 5% |
| Copper Keel | 5,662,282 | 1.16% | 0.50 | 4.18 | 5% |
| Minto East | 2,818,372 | 1.24% | 0.62 | 5.15 | 5% |
| Minto North | 2,169,259 | 1.36% | 0.67 | 5.83 | 2% |
| Area 118 Underground | 1,702,374 | 0.98% | 0.52 | 4.03 | 7% |
| Total | 18,374,167 | 1.07% | 0.46 | 4.00 | 7% |
The continued use of longhole open stoping, incorporating rib pillars, was selected as the most practical approach for the PEA based on deposit geometry, geotechnical conditions, historical operating experience at Minto and overall project economics. The method provides an appropriate balance between production objectives, capital efficiency, operational simplicity and execution risk, while leveraging existing infrastructure and minimizing development requirements, power demand and startup capital. The approach is consistent with the study’s geotechnical criteria and supports a phased restart strategy with reduced schedule and operational complexity.
Future engineering studies may evaluate opportunities to optimize resource recovery; however, any alternative mining approaches would be assessed based on their impact on project economics, capital requirements, operating costs, power availability, execution complexity, and overall project value. As part of the planned Minto Project restart, the existing underground workings will be dewatered, inspected and rehabilitated as required to support safe re-entry to and use of historical haulageways and access the new production areas envisioned for the PEA mine plan. Achieving the planned production profile described in the PEA is dependent on the successful and timely dewatering, inspection and targeted rehabilitation of existing underground workings, development of new underground access infrastructure, establishment of the planned underground mining areas and execution of the planned mine development schedule. The extent and nature of required rehabilitation activities in the existing underground development will be determined following underground inspections completed as dewatering progresses. Due to its location and lack of practical connectivity opportunities to the existing underground workings, the Minto North deposit will be accessed via the development of a new dedicated portal located in close proximity to the existing processing infrastructure. Later in the mine life, a dedicated and additional Copper Keel portal will be established to reduce underground haulage distance from the deposit, enhancing haulage productivity and reducing reliance on the longer route through the existing portal. The integrated open pit and underground mine plans have been designed to consider the oxidation characteristics of the mineralized zones in the Ridgetop and Area 118 open pits as defined in the 2026 MRE. Near‑surface mineralization at Ridgetop in particular displays variable and often elevated oxidation ratios, with recent assessments indicating a mix of oxidation that is typically more pronounced in the shallow zones. Modelled oxidation at the Ridgetop deposit generally decreases with depth, with mineralization transitioning into less oxidized and more sulphide‑dominant material.
This variability introduces additional considerations for blending and mill feed management, as elevated oxide ratios in the mill feed have the potential to reduce copper recovery and increase concentrate moisture, particularly at oxidation ratios exceeding 20% soluble copper to total copper. Maintaining the operational blend within acceptable limits is an important element of the mining and mineral processing strategy developed for the Minto Project.
Metallurgy & Processing Overview
Since the acquisition of the Project by Selkirk Copper, a thorough assessment of the process plant was conducted by the Company, consultants, and vendor representatives. Assessment in the PEA evaluated the potential for targeted circuit upgrades to enable the resumption of operations at a consistent average throughput of 4,100 tpd at 92% process plant availability. The process plant historically employed standard comminution, flotation and dewatering techniques and equipment in the production of a final copper-goldsilver concentrate and no substantive technology or process changes are considered in the restart plan.
Planned upgrades include a new three-stage crushing circuit with screening, two (2) new gravity concentrators to improve gold recovery, a screw dryer to handle concentrate material after filtration to enable the delivery of a consistent concentrate moisture content within control limits, and slurry tailings pumps and cyclones to segregate fine and coarse size fractions for in-pit deposition. The addition of tailings filtration is planned to enable the transition to dry-stack tailings management after Year 3. The designed process flowsheet includes run-of-mine mill feed stockpile, three-stage crushing and screening, crushed feedstock stockpile and drawdown, primary semi-autogenous and ball mill grinding mills, gravity concentration, flotation, concentrate thickening, drying and filtration, and tailings thickening and filtration. The overall process flow diagram depicted in Figure 2 identifies the currently existing process flowsheet in black with new, upgraded, or modified aspects of the flow sheet depicted in blue. Equipment planned to be added part-way through the mine life is shown in gray.
Figure 2: Process Flow Diagram
Run-of-mine (“ROM”) material will be delivered to the crusher area by haulage trucks. This feed will be managed through dedicated ROM stockpiles at the crushing pad to allow blending of material from different mining areas prior to crushing. A new surface crushing and material handling system has been incorporated into the design to support the delivery of ROM material from both underground and open pit sources to the processing plant and provide the ability to control the blending of material of different compositions to control feed grade and oxide ratio.
Crushed material will be conveyed to a stockpile immediately above the hopper feeding the apron feeder with a nominal live capacity of approximately 9,800 tonnes. Crushed material will be reclaimed using an existing apron feeder and transferred by conveyor to the semi-autogenous grinding (“SAG”) mill feed chute. Material in this stockpile which is not automatically fed by gravity will be managed with a front-end loader as needed.
The existing grinding circuit is comprised of a primary SAG mill equipped with a 900 horsepower (“HP”) drive motor, operating in open circuit, followed by two parallel secondary ball mills, each powered by a 900 HP drive motor and configured in parallel closed circuits. The PEA includes provision for upgrades and refurbishment of select grinding circuit components, including the SAG mill drive system. Each ball mill operates in closed circuit with its associated cyclone cluster and with the underflow from the cyclones returning to the corresponding ball mill for further size reduction. Discharge from each ball mill will be directed to the respective of two new Knelson gravity concentrators to improve recoveries of gold and silver prior to reporting to the flotation circuit.