Osisko Mining Inc. (TSX:OSK) is pleased to provide new results from the ongoing exploration program at its 100% owned Windfall Lake gold project located in the Abitibi greenstone belt, Urban Township, Eeyou Istchee James Bay, Québec.

Exploration drilling has discovered a strongly mineralized extension of the Lynx deposit at approximately 1000 metres vertical depth.  DDH OSK-W-19-1857 has extended Lynx 100 metres down plunge in an area outside the prior Windfall mineral resource estimate area (see Osisko news release dated November 27^th, 2018).  The new exploration hole intersected a wide zone of strong silica and sericite alteration (39 metres width), containing sulfides with local gold mineralization from 1278 metres to 1317 metres downhole.  The alteration zone includes three significant gold bearing intervals outlined below.  The new gold intervals are between 70 metres to 270 metres distal from the previous deepest gold bearing intersects in Lynx (OSK-W-17-950, OSK-W-17-991 and OSK-W-18-1367-W2), and confirm that high grade gold mineralization remains open at depth.  Further step out drilling is in progress to pursue this depth extension which has seen no previous drilling.

Osisko President and CEO John Burzynski commented: “Today’s very good results are a further confirmation that there are significant discoveries remaining to be made at Windfall.  This high-grade depth extension of Lynx will be included in the mineral resource update planned for this fall.  Lynx was an exciting discovery made by Osisko in early 2017, and as we have advanced work, it has increasingly become the most significant part of the Windfall deposit.  We are confident that as we further explore Lynx, we will have continued discovery success.”

Sericitic alteration begins at the contact between gabbro and rhyolite units at approximately 1264 metres, increasing in intensity to a strong silica and fuchsite altered zone between 1274 metres to 1283 metres. Sericite alteration decreases at 1320 metres.  Mineralization consists of disseminated pyrite, stringers, with local visible gold and native silver. Lynx is sub-vertical with a dip of 80 degrees, oriented to the NNE at 060 degrees.

Today’s results include the currently available significant analytical results from OSK-19-1857.  Maps and sections showing the location of the new analytical results are available at www.osiskomining.com.

True width determination is estimated at 65-80% of the reported core length interval for the zone.

OSK-W-19-1857 intersected three intervals: 322 g/t Au over 4.3 metres, 136 g/t Au over 2.8 metres and 16.0 g/t Au over 2.4 metres. The first and second intervals contain local visible gold and native silver, up to 10% disseminated pyrite stringers within a strong pervasive silica altered, strong sericite and fuchsite altered rhyolite. The third interval contains up to 3% pyrite stringer and quartz-tourmaline veins within a pervasive within a strong silica altered rhyolite.

Qualified Person

The scientific and technical content of this news release has been reviewed, prepared and approved by Mr. Louis Grenier, M.Sc.A., P.Geo. (OGQ 800), Project Manager of the Windfall Lake gold project, who is a “qualified person” as defined by National Instrument 43-101 – Standards of Disclosure for Mineral Projects.

Quality Control and Reporting Protocols

True width determination is estimated at 65-80% of the reported core length interval for the zone. Assays are uncut except where indicated. Intercepts occur within geological confines of major zones but have not been correlated to individual vein domains at this time. Reported intervals include minimum weighted averages of 3.0 g/t Au diluted over core lengths of at least 2.0 metres. All NQ core assays reported were obtained by either 1-kilogram screen fire assay or standard 50-gram fire-assaying-AA finish or gravimetric finish at (i) ALS Laboratories in Val d’Or, Québec, Thunder Bay, Ontario, Sudbury, Ontario or Vancouver, British Colombia, or (ii) Bureau Veritas in Timmins, Ontario. The 1-kilogram screen assay method is selected by the geologist when samples contain coarse gold or present a higher percentage of pyrite than surrounding intervals. Selected samples are also analyzed for multi-elements, including silver, using an Aqua Regia-ICP-AES method at ALS Laboratories. Drill program design, Quality Assurance/Quality Control (“QA/QC”) and interpretation of results is performed by qualified persons employing a QA/QC program consistent with NI 43-101 and industry best practices. Standards and blanks are included with every 20 samples for QA/QC purposes by the Corporation as well as the lab. Approximately 5% of sample pulps are sent to secondary laboratories for check assay.

About the Windfall Lake Gold Deposit

The Windfall gold deposit is located between Val-d’Or and Chibougamau in the Abitibi region of Québec, Canada. The mineral resource defined by Osisko, as disclosed in the Windfall Lake Technical Report (as defined below) and November 27, 2018 Lynx resource update, comprises 2,874,000 tonnes at 8.17 g/t Au (754,000 ounces) in the indicated mineral resource category and 10,352,000 tonnes at 7.11 g/t Au (2,366,000 ounces) in the inferred mineral resource category. For details regarding the key assumptions, parameters and methods used to estimate the mineral resources presented in respect of the Windfall Lake gold project, please see the technical report entitled “Technical Report and Mineral Resource Estimate for the Windfall Lake Project, Windfall Lake and Urban-Barry Properties” and dated June 12, 2018 (effective date of May 14, 2018), which has been prepared by InnovExplo Inc. from Val-d’Or, Québec (the “Windfall Lake Technical Report”) and the press release “Osisko Releases Mineral Resource Update for Lynx” dated November 27, 2018, which has been prepared by Osisko and reviewed and approved by Micon International, Ltd. from Toronto, Ontario. The Windfall Lake Technical Report and press release are available on Osisko’s website at www.osiskomining.com and on SEDAR under Osisko’s issuer profile at www.sedar.com. The Windfall Lake gold deposit is currently one of the highest grade resource-stage gold projects in Canada. Mineralization occurs in four principal zones: Lynx, Zone 27, Caribou and Underdog. All zones comprise sub-vertical lenses following intrusive porphyry contacts plunging to the northeast. The deposit is well defined from surface to a depth of 900 metres and remains open along strike and at depth. Mineralization has been identified 30 metres from surface in some areas and as deep as 2,000 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 precious metal resource properties in Canada. Osisko holds a 100% interest in the high-grade Windfall gold deposit located between Val-d’Or and Chibougamau in Québec and holds a 100% undivided interest in a large area of claims in the surrounding the Urban Barry area and nearby Quevillon area (over 3,500 square kilometres).