Osisko Windfall Updated Mineral Resource Estimate

Indicated Resource: 1.21M oz Au averaging 9.1 g/t Au
Inferred Resource: 3.94M oz Au averaging 8.4 g/t Au

TORONTO, Feb. 19, 2020 (GLOBE NEWSWIRE) — Osisko Mining Inc. (OSK:TSX, “Osisko” or the “Corporation”) is pleased to provide an updated mineral resource estimate for its 100% owned Windfall gold deposit, located in the Abitibi greenstone belt, Urban Township, Eeyou Istchee James Bay, Québec.

Highlights

Windfall mineral resource estimate expanded to world-class scale

Mineral resource estimate entirely above 1200 metres vertical depth

2019 drilling increased indicated mineral resource estimate by 60% (added 452,000 ounces) and increased inferred mineral resource estimate by 66% (added 1,572,000 ounces)

Osisko’s Lynx discovery hosts average grade of >10 g/t Au and the majority of indicated and inferred mineral resource estimate; significant high-grade zones (Lynx 4, Triple Lynx) remain open down plunge, 19 drills continue with infill and expansion drilling in 2020

John Burzynski, President and Chief Executive Officer of Osisko, commented: “We have been confident since Osisko discovered Lynx in 2016 that we had another world-class gold deposit developing at Windfall. The number of ounces and average grade at Lynx has continued to increase as we advance the resource infill drilling. Recent Lynx bulk sample results (see Osisko news release of December 11, 2019) also showed reconciliation significantly exceeding predicted block model grades and returned higher than anticipated gold recovery. Strong potential for expansion remains in the known Lynx zones, the majority of which are open along strike to the northeast and down plunge below 1,200 metres. The Triple 8 discovery, at approximately 1,500 metres vertical depth, was not included in the current mineral resource estimate but hosts excellent potential to add significant ounces with additional drilling.”

Located in Québec, one of the best mining jurisdictions in the world, this mineral resource estimate moves Windfall to world-class status in terms of scale and grade. Osisko has recently completed 1 million metres of drilling at Windfall, including the longest diamond drill hole in Canada which has shown strong indications that the Windfall gold system extends to depths beyond 2.5 kilometres.

Mr. Burzynski continued: “We have advanced the Windfall Project rapidly over the course of the past four years. It’s worth noting that members of our management, board and technical team have collectively worked on three world class gold deposits discovered in Québec over the past fifteen years – Canadian Malartic, Éléonore, and now Windfall. I am exceedingly proud of our exploration and engineering teams, technical and non-technical employees and contractors, and wish to thank them for their dedicated work on the Windfall Project. We are grateful to our Cree First Nation partners for their warm welcome and assistance in our work on their traditional territory and look forward to advancing the Windfall Project with them. I also wish to thank all of our stakeholders and shareholders for their ongoing strong support.”

This mineral resource estimate is the result of 2,941 drill holes (1,101,008 metres) in the resource area, including 2,280 drill holes (918,273 metres) completed by Osisko from October 2015 to January 3, 2020. The Windfall mineral resource estimate (with an effective date of January 3, 2020) was prepared by Osisko and reviewed and audited by Micon International Limited, Toronto, Ontario. The full technical report, which is being prepared in accordance with National Instrument 43-101 – Standards of Disclosure for Mineral Projects (“NI43-101”), will be available on SEDAR (www.sedar.com) under the Corporation’s issuer profile within 45 days.

Drilling continues at Windfall with 19 rigs focusing on measured and indicated mineral resource conversion for the planned feasibility study. Additional drills are dedicated to exploring down plunge extensions of Lynx, exploring the nearby Fox deposit, and regional target evaluation. The exploration ramp is advancing to provide additional access for underground infill drilling, and pending permit approvals, the collection of a third bulk sample deeper in the Lynx area.

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 zone are associated with pyritic stringers occurring near contacts between volcanic rocks and younger intrusive rocks. The Lynx mineralization zones form an extensive anastomosed network of quartz-rich and pyrite-rich veins hosted within strongly silicified volcanic rocks. This system is located on the southern limb of an open fold plunging at 40 degrees towards ENE along the Bank fault-shear zone. The resource estimation includes a total of 292 mineralization zones defined by individual wireframes with a minimum true thickness of 2.0 metres. The resource reports grade blocks inside volumes potentially mineable by underground methods at a cut-off grade of 3.5 g/t Au.