Porcupine operations

Technical Report On Preliminary Economic Assessment

The Porcupine Complex includes operating mines at Borden, Hoyle Pond, and Pamour. The Hollinger open pit is suspended, and is considered to be mined out for the purposes of this Report. All mineralization from the operating mines is treated at the Dome process plant, including mineralization from Borden, which is trucked 190 km to the Dome plant.

Highlights from the PEA (January 13, 2025) include:

• Mineral resource estimate: Measured and Indicated Mineral Resources totalling 69.7 Mt grading 1.76 g/t Au (approximately 3,932 koz); Inferred Mineral Resources totalling 254 Mt grading 1.53 g/t Au (approximately 12,500 koz; estimated for Borden, Dome, Hoyle Pond and Pamour);

• The 2024 PEA mine plan: based on a sub-set of the Mineral Resources estimates for Borden, Hoyle Pond, and Pamour, and assumes a 22-year mine life, with 10 years of production (2025–2035) from Hoyle Pond, eight years of production (2025–2033) from Borden, and 21 years of production (2025–2046) from open pit operations at Pamour; stockpiled material generated during mining of Pamour will be reclaimed for an additional year of milling at the Dome process plant (2047);

• Capital cost estimate: mining costs over the proposed life-of-mine (LOM) total US$868 M, comprising US$147 M for Borden, US$175 M for Hoyle Pond, and US$546 M for Pamour. Process capital costs total US$642 M and site general sustaining capital are US$61 M over the LOM. The exploration capital costs are US$93 M. Closure costs are estimated at US$722 M. The LOM capital costs, inclusive of closure and reclamation, total US$2,385 M;

• Operating cost estimate: mine operating cost estimates include an average of US$126/t processed at Borden, US$291/t processed for Hoyle Pond and US$18.90/t processed for Pamour. Process costs include an allocation of US$8.93/t processed across all operations (fixed costs) in addition to a variable process cost of US$7.33/t processed for Borden, US$7.33/t processed for Hoyle Pond, and US$6.79/t processed for Pamour. All operating costs related to infrastructure are allocated to either the process plant or each mining operation. Total general and administrative costs are estimated at US$770 M. The G&A unit cost averages approximately US$8.09/t processed. Overall, LOM mining costs total US$2,915 M, LOM process costs total US$1,507 M, and LOM general and administrative costs US$771 M, for a total LOM estimate of US$5,192 M;

• Economic analysis: reported on a 100% project ownership basis. Project acquisition costs are considered to be corporate Discovery Silver costs and are not included in the financial evaluation. A royalty anticipated as part of financing of acquisition is included in the Project economics. The Project valuation date basis was January 1, 2025. A discount rate of 5% was used. A reverting price curve was used for the gold price, based on Canadian Imperial Bank of Commerce (CIBC) consensus forecasts, resulting in a long-term gold price assumption for 2028 and beyond of US$2,150/oz Au. The economic analysis includes provision for the Canadian corporate income tax (Federal and Ontario Income Tax), which consists of a combined 25% income tax, and the Ontario Mining Tax, applied at 10% on production earnings before interest, taxes, and corporate overhead costs. Forecast tax payments over the 2024 PEA LOM are estimated at US$947 M. The after-tax Project NPV is US$1,239 M. The economic analysis does not entail initial capital investment prior to the start of production and of cashflow and so there is no internal rate of return or project payback period relevant to the economic analysis presented;

• The sensitivity of the Project NPV to changes in head grades, gold price, metallurgical recoveries, capital costs and operating cost assumptions was tested using a range of up to 23% above and below the base case values. The Project is most sensitive to changes in metal price, closely followed by head grade. Changes in metal prices approximately mirror changes in the gold grade and metallurgical recovery. The Project is less sensitive to variations in operating costs, and least sensitive to capital cost changes;

• The 2024 PEA is preliminary in nature and includes Inferred Mineral Resources that are too speculative geologically to have economic considerations applied to them that would enable them to be categorized as Mineral Reserves, and there is no certainty that the preliminary economic assessment will be realized.