Selkirk Copper Mines Inc press release

Selkirk Copper Announces Updated Mineral Resource Estimate with 182% Increase in Measured & Indicated Copper and 184% Increase in Measured & Indicated Gold

2026-07-30

TSXV - TSX Venture Exchange · Copper · Silver · Gold · Canada · Resource Estimate

Highlights

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The 2026 Mineral Resource Estimate (2026 MRE) establishes a Measured & Indicated Resource of47.8 million tonnes, representing a 280% increase in tonnagein these categories compared to the 2025 Mineral Resource Estimate (2025 MRE):

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47.8 million tonnes ofMeasured & Indicated Resources 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; 182%, 184% and 188% increases respectively above the 2025 MRE

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Measured & Indicated Resources include 26.0 million tonnes ofunderground resources at 1.14% Cu, 0.49 g/t Au, and 4.4 g/t Ag; and 21.8 million tonnes ofopen pit resources at 0.59% Cu, 0.17 g/t Au, and 1.8 g/t Ag

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An additional 16.9 million tonnes of Inferred Resourcehave also been delineated:

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16.9 million tonnes Inferred Resources 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

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Mineralization remains open laterally and at depth across central mine area, and there are several high potential drill targets for follow-up in future exploration, definition and delineation work

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The ongoing 50,000 metre Phase 2 drill program is 75% complete, the results of which have not been included in this resource update. Initial assay results and visual drill logs continue to show expansion potential across each of the mineralized zones in the central mine area

British Columbia and Pelly Crossing, Yukon--(Newsfile Corp. - July 30, 2026) - Selkirk Copper Mines Inc.(TSXV: SCMI) (FSE: IO20) (OTCQX: SKRKF) ("Selkirk Copper" or the "Company") is pleased to announce the results of an updated Mineral Resource Estimate for the Minto Project in the Yukon, Canada (the "Resource Estimate" or "MRE") which is being used for the development of an updated Preliminary Economic Assessment (the "PEA").

M. Colin Joudrie, President & CEO, commented: "The Phase 1 52,288 metre drill program has delivered one of the primary objectives of this phase of work. Specifically, it has clearly demonstrated the significant potential for discovery of new zones and expansion of the known zones of high-grade copper-gold-silver mineralization on the Minto Mine Property in both underground and open pit mineable configurations. Further, the team, with this focused Phase 1 program, have provided the mine planning and development team with significantly more material in the Measured & Indicated Resource categories on which to build integrated mine plans that will inform our targeted 12-15 year mine life at 4,100 tonnes per day mill feed.

Growing the Measured and Indicated Resource category by 280% in our Phase 1 drill program demonstrates the significant potential to grow mineable resources within the Minto Mine Property in a cost-effective and timely manner. It supports the overall restart program objectives and strongly suggests that we have the opportunity to further upgrade and enhance the quality of the copper-gold-silver mineralized lenses which have the potential to further improve the quality of our mine plans in the upcoming Feasibility Study as well as into the future.

Additionally, from this program, the exploration & geosciences team has developed an enhanced understanding of the geology and structural controls of the sixty-nine mineralized lenses which has created a coherent and actionable drill targeting methodology that has resulted in the discovery of several new lenses of high-grade copper-gold-silver mineralization within the mine footprint. This targeting methodology, which takes into consideration geological, geochemical, geophysical, structural, and topologic information, is being applied within the central mine area to further increase mineable resources, but also, for the first time to Selkirk Copper's 26,850 hectares of mineral claims in the Minto-Carmacks belt.

We look forward to integrating results of our Phase 2 50,000 metre drill program, of which 37,000 metres of drilling has already been completed, into the growing Inferred, Indicated, and Measured Resources on the Minto Project. The Phase 2 program will to continue to upgrade the confidence of mineralization on the property and to support a feasibility study scheduled to start in Q3 2026."

The Updated Mineral Resource Estimate

The updated MRE contains both underground and open pit resources. The underground contains Measured & Indicated Resources of 26.0 million tonnes grading 1.14% Cu, 0.49 g/t Au, and 4.4 g/t Ag, plus an additional Inferred Resource of 9.8 million tonnes grading 0.91% Cu, 0.36 g/t Au, and 3.5 g/t Ag. The open pit contains an additional 21.8 million tonnes of Indicated Resources grading 0.59% Cu, 0.17 g/t Au, and 1.8 g/t Ag, plus Inferred Resources of 7.1 million tonnes grading 0.55% Cu, 0.13 g/t Au, and 1.6 g/t Ag. A small amount of Measured Resources have been established, representing a higher category of confidence for some underground mining areas.

In total, the updated MRE contains 940 million lbs copper, 530 koz gold, and 4.97 million oz silver in the Measured & Indicated categories and an additional 281 million lbs copper, 142 koz gold, and 1.5 million oz silver in the Inferred category.

The resource estimate is summarized in Table 1 below, with sensitivities to various NSR cut-offs detailed in Table 2 and Table 3. The updated MRE was prepared by Sue Bird, P.Eng., of Moose Mountain Technical Services who is independent of Selkirk Copper. A technical report prepared in accordance with National Instrument 43-101 - Standards of Disclosure for Mineral Projects (the "Technical Report") will be filed on the Company's website and SEDAR+ within 45 days of the date of this press release.

Relevant assumptions used in the MRE are detailed below and will be further described in the Technical Report. The $30 (open pit) and $80 (underground) CAD$/tonne NSR cutoffs were selected as they correlate to marginal mining and processing cost assumptions expected in the upcoming PEA design basis. With the release of this updated MRE, Selkirk Copper's previous technical reports, including the 2025 MRE1, are no longer current and should not be relied upon.

Table 1: Updated summary of mineral resources for the Minto Project

| Type | Cutoff (CAD$) | Class | ROM | In situ Grades | Metal | | | | | | | | | Tonnage (000) | NSR (CAD$) | Cu (%) | Au (gpt) | Ag (gpt) | Ox Ratio | ASCu (%) | Cu (Mlbs) | Au (Koz) | Ag (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 1: 1.

The MRE has been completed by Sue Bird of Moose Mountain Technical Services (MMTS).

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The effective date of the resource is June 10, 2026

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Resources are reported using the 2014 CIM Definition Standards and were estimated using the 2019 CIM Best Practices Guidelines.

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For the Net Smelter Proceeds (NSP) calculations:

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Metal prices are USD$4.60lb Cu, USD$3300/oz Au, USD$40/oz Ag;

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A currency exchange rate of 0.72 US$ per CAD$;

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97.5% payable Cu, 98% payable Au and 92% payable Ag; and the following inputs:

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Concentrate grade of 38% Cu with a moisture content of 8%;

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Unit deductions of 1gpt Au, 30gpt Ag;

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Offsite costs (refining, transport and insurance) of US$200/dmt;

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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;

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Royalties of 1.5% NSR.

1. Recoveries are as follows:

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_CuRecov - 95.5%+1.07*Cu%-113*(ASCu/TCu), with a maximum of 98%_

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_AuRecov = 35.63+0.58032*Curecov-1.3341*Cu%^ 0.8932, with a maximum of 85%_

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_AgRecov = 69.4+1.9*Aggpt, to a maximum of 85%_

1.

_These inputs result in the following NSR and CuEq equations: NSR = CAD$CuNSP*CuRecov*Cu%*22.0462 + CAD$AuNSP*AuRecov*Augpt + CAD$AgNSP*AgRecov*Aggpt)/31.10348 CuEq = NSR/(CuNSP*CuRecov*22.0462)_

1.

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.

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Mining costs are CAD$4.58/tonne for open pit, marginal mining costs of CAD$50/tonne for underground, Processing costs are CAD$30/tonne milled, and G&A costs are CAD$20/tonne milled.

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Pit slope angles are assumed at 45º.

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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.

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Oxide Ratio = (ASCu)/ (Total Copper)

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Numbers may not add due to rounding. | | | | | | | | | | | | |

The mineral resource estimate includes Inferred mineral resources that are considered too speculative geologically to have economic considerations applied to them that would enable them to be converted to mineral reserves. Mineral Resources that are not Mineral Reserves do not have demonstrated economic viability. However, a primary objective of Selkirk Copper's ongoing Phase 2 drill program is targeting the Inferred resources, as defined in this MRE update, at a similar drill spacing as the Indicated resources.

The Qualified Person(s) are of the opinion that issues relating to all relevant technical and economic factors likely to influence the prospects of eventual economic extraction can be resolved with further work. These factors may include environmental permitting, infrastructure, sociopolitical, marketing, or other relevant factors. Factors that may affect the estimates include: metal price assumptions, changes in interpretations of mineralization geometry or continuity due to future drilling results, changes to interpolation assumptions or methodology, metallurgical recovery assumptions, mining method assumptions, or operating cost assumptions.

Key Results from the Resource Estimate

The 2026 MRE represents a significant increase in tonnage and contained metal compared to the 2025 MRE1, as well as a significant increase in the proportion of Indicated resources.

These increases can be attributed to multiple factors, including the following:

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Discovery of new high-grade lenses and expansion of existing high-grade lenses;

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Increased metal price assumptions, elevating some lower grade material above NSR cut-off;

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Strategic infill drilling to increase confidence in the extents of high-grade mineralization;

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Improved integration of oriented core structural measurements into geological modelling;

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Improved geostatistical analysis of grade variability justifying the use of locally variable search orientations to better align interpolations with structural and grade trends;

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Updated metallurgical recovery models and design basis assumptions reflecting the development of the PEA Study.

The Phase 1 Drill Program was successful in the objective of resource expansion in four key locations:

1.

At Minto North, the 202 Lens expanded significantly with an increase of 238% in Indicated contained copper compared to the 2025 MRE1. Mineralization in this lens is notably higher grade than some other parts of the deposit, with the Indicated resource averaging 1.39% Cu, 0.75 g/t Au, and 6.57 g/t Ag.

2.

At Minto Main, the 117 Lens expanded significantly with the first establishment of Indicated and Measured resources in an area which previously contained sparse historical drill holes. This mineralization remains open for further expansion to the west and northwest.

3.

At Area 118, the 301 and 304 Lenses represent a significant new discovery located beneath previously known resources, and close to existing underground workings. A large Inferred resource has been identified here and is a priority target for infill drilling as part of the Phase 2 drill program.

4.

At Ridgetop, a group of stacked, sub horizontal mineralized lenses have been expanded with an increase of 255% in Indicated contained copper compared to the 2025 MRE1. This mineralization is located near-surface and within the resource open pit.

The results of the Phase 1 Drill Program demonstrate the potential for significant new discoveries and expansion of known resources located close to the previous mining areas. The efficiency of the Phase 1 drill program to deliver these resources is a testament to the team's ability to rapidly develop geological knowledge of the deposit and leverage it to deliver high-quality results.

Additionally, updated metal pricing and design basis assumptions utilized in the 2026 MRE elevated lower grade material above the NSR cut-off. This resulted in an overall increase of tonnage with reasonable prospects of eventual economic extraction, but also resulted in a lower average grade. Detailed evaluation of the 2026 MRE indicates that approximately half of the overall expansion of Indicated resources is due to increased metal prices and changes to design basis assumptions; whereas the other half is due to exploration success through drilling. Development of an updated Mine Plan is underway as part of the upcoming PEA Study, and this mine plan will seek to maximize value from the 2026 MRE towards the targeted 12-15 year mine life.

[](https://images.newsfilecorp.com/files/11605/307256_452b22da1442cad5_001full.jpg)

Figure 1: Plan view map highlighting four key areas of resource expansion and discovery contributing to resource growth in the 2026 mineral resource estimate. Results are described in comparison to 2025 MRE1.

To view an enhanced version of this graphic, please visit: https://images.newsfilecorp.com/files/11605/307256_452b22da1442cad5_001full.jpg

[](https://images.newsfilecorp.com/files/11605/307256_452b22da1442cad5_002full.jpg)

Figure 2:Visualization of resource tonnage in Inferred, Indicated, and Measured categories from the 2026 MRE compared to previous studies including the 2025 MRE1and the 2021 PEA2. The details resource estimation and design basis are different for each study, refer to the documents listed in the References for more details.

To view an enhanced version of this graphic, please visit: https://images.newsfilecorp.com/files/11605/307256_452b22da1442cad5_002full.jpg

MRE Cut-off Sensitivities

Table 2: Summary of the underground resources and their sensitivity to various NSR cut-offs

| Mining Type | Class | Cutoff | ROM | In situ Grades | Metal | | | | | | | | | (CAD$) | Tonnage (000) | NSR (CAD$) | Cu (%) | Au (gpt) | Ag (gpt) | Ox Ratio | ASCu (%) | Cu (Mlbs) | Au (Koz) | Ag (Koz) | | | | Under Ground | Measured | $60 | 380 | $146.60 | 0.882 | 0.377 | 3.14 | 0.05 | 0.041 | 7.4 | 4.6 | 38.3 | | $70 | 368 | $149.25 | 0.897 | 0.383 | 3.2 | 0.05 | 0.041 | 7.3 | 4.5 | 37.7 | | | | $80 | 348 | $153.47 | 0.923 | 0.393 | 3.3 | 0.05 | 0.041 | 7.1 | 4.4 | 36.5 | | | | $90 | 326 | $157.95 | 0.949 | 0.404 | 3.4 | 0.05 | 0.042 | 6.8 | 4.2 | 35.2 | | | | $100 | 290 | $165.80 | 0.993 | 0.425 | 3.5 | 0.05 | 0.042 | 6.4 | 4.0 | 32.8 | | | | $110 | 253 | $174.84 | 1.042 | 0.450 | 3.7 | 0.04 | 0.043 | 5.8 | 3.7 | 30.4 | | | | Indicated | $60 | 29,324 | $174.44 | 1.071 | 0.447 | 4.08 | 0.07 | 0.067 | 692.1 | 421.4 | 3,847.8 | | | $70 | 27,526 | $181.57 | 1.108 | 0.467 | 4.2 | 0.06 | 0.067 | 672.4 | 413.3 | 3,751.2 | | | | $80 | 25,679 | $189.20 | 1.148 | 0.489 | 4.4 | 0.06 | 0.067 | 649.8 | 403.7 | 3,637.8 | | | | $90 | 23,747 | $197.68 | 1.193 | 0.514 | 4.6 | 0.06 | 0.067 | 624.4 | 392.4 | 3,510.1 | | | | $100 | 21,613 | $207.79 | 1.246 | 0.544 | 4.8 | 0.06 | 0.069 | 593.7 | 378.1 | 3,356.1 | | | | $110 | 19,551 | $218.63 | 1.303 | 0.577 | 5.1 | 0.06 | 0.070 | 561.7 | 362.5 | 3,193.7 | | | | M+I | $60 | 29,704 | $174.08 | 1.068 | 0.446 | 4.07 | 0.07 | 0.067 | 699.5 | 426.0 | 3,886.1 | | | $70 | 27,894 | $181.15 | 1.105 | 0.466 | 4.2 | 0.06 | 0.066 | 679.7 | 417.9 | 3,788.9 | | | | $80 | 26,026 | $188.72 | 1.145 | 0.488 | 4.4 | 0.06 | 0.066 | 656.9 | 408.1 | 3,674.3 | | | | $90 | 24,073 | $197.14 | 1.189 | 0.512 | 4.6 | 0.06 | 0.067 | 631.2 | 396.6 | 3,545.2 | | | | $100 | 21,904 | $207.24 | 1.243 | 0.543 | 4.8 | 0.06 | 0.068 | 600.0 | 382.1 | 3,389.0 | | | | $110 | 19,803 | $218.07 | 1.300 | 0.575 | 5.1 | 0.06 | 0.070 | 567.5 | 366.2 | 3,224.1 | | | | Inferred | $60 | 11,810 | $133.59 | 0.836 | 0.323 | 3.3 | 0.06 | 0.045 | 217.6 | 122.5 | 1,238.0 | | | $70 | 10,741 | $140.42 | 0.874 | 0.340 | 3.4 | 0.06 | 0.045 | 206.9 | 117.6 | 1,175.8 | | | | $80 | 9,812 | $146.57 | 0.907 | 0.356 | 3.5 | 0.05 | 0.044 | 196.3 | 112.2 | 1,112.7 | | | | $90 | 8,511 | $155.97 | 0.959 | 0.381 | 3.7 | 0.05 | 0.044 | 179.9 | 104.2 | 1,018.3 | | | | $100 | 7,171 | $167.26 | 1.017 | 0.418 | 4.0 | 0.05 | 0.046 | 160.7 | 96.3 | 919.7 | | | | $110 | 6,139 | $177.77 | 1.070 | 0.450 | 4.2 | 0.05 | 0.047 | 144.9 | 88.9 | 833.3 | | |

Table 3: Summary of the open pit resources and their sensitivity to various NSR cut-offs

| Mining Type | Class | Cutoff | ROM | In situ Grades | Metal | | | | | | | | | (CAD$) | Tonnage (000) | NSR (CAD$) | Cu (%) | Au (gpt) | Ag (gpt) | Ox Ratio | ASCu (%) | Cu (Mlbs) | Au (Koz) | Ag (Koz) | | | | Open Pit | Indicated | $25 | 23,444 | $76.86 | 0.566 | 0.165 | 1.8 | 0.11 | 0.073 | 292.7 | 124.6 | 1,336.9 | | $30 | 21,779 | $80.63 | 0.589 | 0.174 | 1.8 | 0.11 | 0.073 | 282.8 | 121.7 | 1,294.3 | | | | $40 | 18,455 | $88.86 | 0.638 | 0.193 | 2.0 | 0.10 | 0.073 | 259.5 | 114.6 | 1,194.2 | | | | $50 | 15,070 | $98.72 | 0.697 | 0.218 | 2.2 | 0.09 | 0.076 | 231.7 | 105.8 | 1,069.9 | | | | $60 | 11,961 | $110.12 | 0.767 | 0.249 | 2.4 | 0.09 | 0.080 | 202.1 | 95.9 | 934.2 | | | | Inferred | $25 | 7,673 | $70.80 | 0.521 | 0.125 | 1.5 | 0.08 | 0.047 | 88.1 | 30.9 | 369.9 | | | $30 | 7,052 | $74.61 | 0.546 | 0.133 | 1.6 | 0.08 | 0.048 | 85.0 | 30.1 | 353.8 | | | | $40 | 5,850 | $82.75 | 0.599 | 0.149 | 1.7 | 0.07 | 0.049 | 77.2 | 28.1 | 320.8 | | | | $50 | 4,517 | $93.88 | 0.669 | 0.175 | 1.9 | 0.07 | 0.052 | 66.6 | 25.5 | 272.7 | | | | $60 | 3,209 | $109.82 | 0.767 | 0.217 | 2.1 | 0.07 | 0.058 | 54.3 | 22.4 | 218.0 | | |

Details of the Mineral Resource Estimate

The 2026 MRE is supported by results from Selkirk Copper's Phase 1 Drill Program, comprising 52,288 metres of drilling in 175 holes, as well as historical drilling. Results from Selkirk Copper's ongoing Phase 2 Drill Program have not been included into this resource estimate. In total, the 2026 MRE is supported by 428,388 metres of drilling in 1,956 holes. This drilling database includes geochemical assays, lithological and mineralogical information, structural measurements, and density measurements. A robust program of QAQC and data verification was maintained to ensure the drilling database is appropriate for resource estimation.

The workflows for geological modelling and resource estimation used in the 2026 MRE is similar to the previous 2025 MRE1; however significant improvements have been implemented for both modelling and estimation. The geological modelling has been improved through observations and interpretations made by the Exploration team during the Phase 1 Drill Program, as well as deeper interrogation of historical geological data. The resource estimation has been improved through the implementation of "unfolding" of the lenses during the grade interpolations to more accurately model the grade distribution by using locally variable search orientations and distances.

Geological Context

An improved geological model has been developed based upon a comprehensive review of historical data from the Project and the surrounding Minto-Carmacks district, as well as new data and interpretations arising from the Phase 1 program. This site-specific model assists with cost-effective exploration targeting and delineation drilling, and informs development of the geological model used to support resource estimation. Key elements of this model are described below and summarized in Figure 3 and Figure 4.