Osisko Mining Orders Milling Equipment for Windfall

TORONTO, March 09, 2021 - Osisko Mining Inc. (OSK:TSX: "Osisko" or the "Corporation") is pleased to announce that it has placed an order for grinding equipment and ancillaries from FLSmidth, a leading technology and equipment supply company, for its 100% owned Windfall gold project located in the Abitibi greenstone belt, Urban Township, Eeyou Istchee James Bay, Qu?bec.

The order consists of a 7.3 meters (24 foot) diameter x 3.4 meters (11 foot) long gear-driven semi-autogenous grinding (SAG) mill and a 5.2 meters (17 foot) diameter x 9.4 meters (31 foot) long gear-driven ball mill. Current planning foresees installation and operation of the grinding mills in a SABC¹ configuration. The grinding mills have a capacity of processing up to 176.6 dry tonnes per hour, or 3,900 tonnes per day based on 92% availability. The equipment is expected to be delivered to the Windfall project in the second half of 2022. Installation will follow pending successful receipt of all permits and authorizations.

John Burzynski, Chief Executive Officer of Osisko commented: "FLSmidth is a recognized global leader in grinding technologies with a long track record of providing high quality products, and we are looking forward to be working with them on our developing Windfall project. Securing these critical long lead time components of the grinding circuit is an important first step in solidifying detailed engineering for the Windfall plant. We continue to advance all aspects of work on Windfall including our environmental assessment and consultation with our host communities and look forward to additional near-term announcements regarding our infrastructure plans."

About the Windfall Gold Deposit
The Windfall gold deposit is located between Val-d'Or and Chibougamau in the Abitibi region of Qu?bec, Canada. The mineral resource defined by Osisko, as disclosed in the news release dated February 17, 2021 and assuming a cut-off grade of 3.50 g/t Au, comprises 521,000 tonnes at 11.3 g/t Au (189,000 ounces) in the measured mineral resource category, 5,502,000 tonnes at 9.4 g/t Au (1,668,000 ounces) in the indicated mineral resource category and 16,401,000 tonnes at 8.0 g/t Au (4,244,000 ounces) in the inferred mineral resource category. The key assumptions, parameters and methods used to estimate the mineral resource estimate disclosed in the February 17, 2021 news release, certain of which are described in the February 17, 2021 news release, will be further described in the full technical report being prepared for this updated mineral resource estimate in accordance with NI 43-101, and will be available on SEDAR (www.sedar.com) under the Corporation's issuer profile within 45 days from February 17, 2021. 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 zones: Lynx, Main Zone, and Underdog. Mineralization is generally comprised of sub-vertical zones following intrusive porphyry contacts plunging to the northeast. The resources are defined from surface to a depth of 1,600 metres as it now includes the Triple 8 (T8) zone. The resources excluding T8 are defined from surface to a depth of 1,200 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.

About Osisko Mining Inc.
Osisko is a mineral exploration company focused on the acquisition, exploration, and development of gold resource properties in Canada. Osisko holds a 100% interest in the high-grade Windfall gold deposit located between Val-d'Or and Chibougamau in Qu?bec and holds a 100% undivided interest in a large area of claims in the surrounding Urban Barry area and nearby Qu?villon area (over 2,700 square kilometres).

About FLSmidth
FLSmidth is the market-leading supplier of sustainable productivity to the global mining and cement industries. Headquartered in Copenhagen, Denmark, and with offices in more than 50 countries including Canada, FLSmidth delivers engineering, equipment and service solutions to customers worldwide. Productivity, sustainability, and quality are focus areas for the 12,000 employees in FLSmidth.

Cautionary Note Regarding Forward-Looking Information
This news release contains "forward-looking information" within the meaning of the applicable Canadian securities legislation that is based on expectations, estimates, projections and interpretations as at the date of this news release. Any statement that involves predictions, expectations, interpretations, beliefs, plans, projections, objectives, assumptions, future events or performance (often, but not always, using phrases such as "expects", or "does not expect", "is expected", "interpreted", "management's view", "anticipates" or "does not anticipate", "plans", "budget", "scheduled", "forecasts", "estimates", "potential", "feasibility", "believes" or "intends" or variations of such words and phrases or stating that certain actions, events or results "may" or "could", "would", "might" or "will" be taken to occur or be achieved) are not statements of historical fact and may be forward-looking information and are intended to identify forward-looking information. This news release contains the forward-looking information pertaining to, among other things: the Windfall gold deposit being one of the highest-grade resource-stage gold projects in Canada and having world-class scale; the key assumptions, parameters and methods used to estimate the mineral resource estimate disclosed in this news release; the prospects, if any, of the Windfall gold deposit; timing and ability of Osisko to file a technical report for the mineral resource estimate disclosed in this news release; the timing and ability of Osisko, if at all, to publish a feasibility study for the Windfall gold deposit; the amount and type of drilling to be completed and the timing to complete such drilling; the focus of the remaining infill drilling; the trend of grade increase; the Lynx zone remaining open to expansion down plunge; upgrading a inferred mineral resource to a measured mineral resource or indicated mineral resource category; future drilling at the Windfall gold deposit; the significance of historic exploration activities and results. Such factors include, among others, risks relating to the ability of exploration activities (including drill results) to accurately predict mineralization; errors in management's geological modelling; the ability of Osisko to complete further exploration activities, including (infill) drilling; property and royalty interests in the Windfall gold deposit; the ability of the Corporation to obtain required approvals; the results of exploration activities; risks relating to mining activities; the global economic climate; metal prices; dilution; environmental risks; and community and non-governmental actions. Although the forward-looking information contained in this news release is based upon what management believes, or believed at the time, to be reasonable assumptions, Osisko cannot assure shareholders and prospective purchasers of securities of the Corporation that actual results will be consistent with such forward-looking information, as there may be other factors that cause results not to be as anticipated, estimated or intended, and neither Osisko nor any other person assumes responsibility for the accuracy and completeness of any such forward-looking information. Osisko does not undertake, and assumes no obligation, to update or revise any such forward-looking statements or forward-looking information contained herein to reflect new events or circumstances, except as may be required by law.

CONTACT INFORMATION:
John Burzynski
Chief Executive Officer
Telephone (416) 363-8653

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¹ In a SABC configuration, the SAG and ball mill are in closed circuit, with the SAG mill closed with a crusher to control the amount of 'critical size' material in the circuit.