Osisko Mining Inc. provided the updated mineral resource estimate ("MRE") for its 100% owned world-class Windfall gold deposit, located in the Abitibi greenstone belt, Urban Township, Eeyou Istchee James Bay, Québec. This MRE reflects the results of approximately 1.7 million metres of drilling, with 1.5 million metres completed by Osisko since October 2015, and includes all drilling completed as of September 2021 and all analytical results received as of October 20, 2021. An additional 70,000 metres of infill and expansion drilling has been completed since September 2021.

This additional drilling and outstanding analytical results, together with ongoing surface and underground drilling, will be integrated into the database for the pending feasibility study expected to be completed in fourth quarter of 2022. This MRE reflects the results of 4,536 drill holes (1,722,097 metres of core) in the resource area, including 3,882 drill holes (1,539,984 metres of core) completed by Osisko from October 2015 to September 20, 2021 with assays up to October 20, 2021. The MRE (with an effective date of October 20, 2021) was prepared by Osisko, under the supervision of BBA Inc. This mineral resource estimate reflects the current status of the geological interpretation supported by infill drilling, underground mapping and bulk sample results.

Most mineralized envelopes in the Main area are associated with pyritic stringers. Lynx and Underdog mineralized lenses predominantly form an extensive anastomosed network of quartz-rich and pyrite-rich veins. The mineralization system is located near contacts between volcanic and pre-mineral intrusive rocks in Main and Lynx areas, and more specifically, within pre-mineral intrusive units in Underdog.

The MRE is 50% contained within 30 wireframes, and 75% contained within 98 wireframes. The MRE considers a total of 556 mineralized lenses defined by individual wireframes with a minimum true thickness of 2.0 metres. The MRE reports grade blocks inside volumes potentially mineable by underground methods at a cut-off grade of 3.5 g/t Au.

The cut-off calculation below has been rounded up to 3.5 g/t Au to better represent a future mining cut-off.