Osisko Announces Hydroelectric Power Allocation for Windfall

Hook-up Expected Early 2024

TORONTO, Oct. 12, 2023 (GLOBE NEWSWIRE) -- Osisko Mining Inc. (OSK:TSX. "Osisko" or the "Corporation") is pleased to announce that "Windfall Mining Group" (its 50% jointly owned partnership with a Gold Fields Limited subsidiary), has concluded the hydro-electricity power allocation agreement with Hydro-Québec, a wholly-owned Crown corporation of the Québec Government.

The forecasted power demand and allocation for the electrical Installation is 27,400 kW for Windfall. Power will be delivered at the MICO substation located in nearby Waswanipi, Quebec, then be transported using a dedicated power line (currently under construction) from the MICO substation to Windfall by Miyuukaa Corporation (please see news release of Osisko dated March 16, 2023 entitled "Osisko Announces Definitive Agreement with Miyuukaa to transport Hydroelectric Power to Windfall Project").

John Burzynski, Chairman and Chief executive officer commented: "Receipt of the Windfall power allocation is a major milestone, as it will significantly reduce greenhouse gas emissions and project power costs. It is well aligned with our joint-venture ESG goals."

Power line construction work is progressing on schedule with the hook-up date anticipated in early 2024.

About the Windfall Gold Deposit
The Windfall gold deposit is located between Val-d’Or and Chibougamau in the Abitibi region of Québec, Canada. The mineral resource estimate on Windfall (with an effective date of June 7, 2022 ) (the "Windfall Resource Estimate") and the mineral reserve estimate on Windfall (with an effective date of November 25, 2022) (the "Windfall Reserve Estimate") are described in the technical report entitled "Feasibility Study for the Windfall Project, Eeyou Istchee James Bay, Québec, Canada" (the "FS Technical Report”) and dated January 10, 2023 (with an effective date of November 25, 2022). The Windfall Resource Estimate, assuming a cut-off grade of 3.50 g/t Au, comprises 811,000 tonnes at 11.4 g/t Au (297,000 ounces) in the measured mineral resource category, 10,250,000 tonnes at 11.4 g/t Au (3,754,000 ounces) in the indicated mineral resource category and 12,287,000 tonnes at 8.4 g/t Au (3,337,000 ounces) in the inferred mineral resource category. The Windfall Mineral Reserve, assuming 3.5 g/t operating, 2.5 g/t incremental, and 1.7 g/t development cut-off grade, comprises 12,183,000 tonnes at 8.06 g/t Au (3,159,000 ounces) in the probable mineral reserves category. The key assumptions, parameters, limitations and methods used in the feasibility study for Windfall, including the related Windfall Resource Estimate and Windfall Reserve Estimate, are described in the FS Technical Report, which was prepared in accordance with National Instrument 43-101 – Standards of Disclosure for Mineral Projects ("NI 43-101"). The FS Technical Report is available on SEDAR+ (www.sedarplus.com) under Osisko’s issuer profile. The Windfall gold deposit is currently one of the highest-grade resource-stage gold projects in Canada and has world-class scale. Mineralization occurs in three principal areas: Lynx, Main, and Underdog. Mineralization is generally comprised of sub-vertical lenses following intrusive porphyry contacts plunging to the northeast. The resources are defined from surface to a depth of 1,600 metres, including the Triple 8 (TP8) zone. The reserves are defined from surface to a depth of 1,100 metres. The deposit remains open along strike and at depth. Mineralization has been identified at surface in some areas and as deep as 2,625 metres in others with significant potential to extend mineralization down-plunge and at depth.