Osisko Intersects High Grade in Three Lynx Zones

TORONTO, Oct. 21, 2019 - Osisko Mining Inc. (OSK:TSX. "Osisko" or the "Corporation") is pleased to provide new drilling results from the ongoing definition and expansion drill program at its 100% owned Windfall gold project located in the Abitibi greenstone belt, Urban Township, Eeyou Istchee James Bay, Québec.

The program is currently focused on infill drilling and expansion drilling at the Lynx deposit, exploration on the main mineralized zones, and deep exploration in the central areas of the mineralized intrusive system. Sixteen drills are active at Lynx and Triple Lynx, with another seven drills conducting infill and exploration drilling on other areas of the deposit.

Expansion drilling in Lynx Extension intersected 14.3 g/t Au over 5.9 metres in hole OSK-W-19-1992-W1, 200 meters down plunge from the nearest intersection, 33.4 g/t Au over 3.7 metres (see Osisko news release dated June 3, 2019) and 550 metres from the nearest resource wireframe.

Osisko President and Chief Executive Officer John Burzynski commented: “The Lynx zones have delivered outstanding results for us, especially the expansion step-outs which continue to significantly grow our zones and demonstrate good continuity. With all three zones remaining open down-plunge, we will continue both infill and expansion drilling to add ounces in all categories for the resource update.”

Significant new analytical results from 73 intercepts in 15 drill holes and 28 wedges from surface focused on Lynx infill and expansion drilling are presented below. Additionally, 20 intercepts in 14 underground drill holes focused infill drilling, including the Lynx bulk sample area, are included in the table below.

Highlights from new drilling results include: 284 g/t Au over 3.2 metres in OSK-W-18-1550; 453 g/t Au over 2.0 metres in WST-19-0202; 288 g/t Au over 2.0 metres in OSK-W-19-1949-W2; 30.8 g/t Au over 11.9 metres in OSK-W-19-1857-W6; 61.6 g/t Au over 4.1 metres in OSK-W-19-1681; 95.5 g/t Au over 2.2 metres in WST-19-0154; 49.4 g/t Au over 4.2 metres in OSK-W-19-1963-W4; 27.5 g/t Au over 7.1 metres in OSK-W-19-1963-W3; and 37.2 g/t Au over 4.7 metres in WST-19-0124. Maps showing hole locations and full analytical results are available at www.osiskomining.com.

Notes: True widths are estimated at 55 – 80% of the reported core length interval. See "Quality Control and Reporting Protocols" below. Ext = Extension and HW = Hanging wall.

OSK-W-19-923-W4 intersected three intervals in Lynx: 3.63 g/t Au over 2.0 metres, 20.3 g/t Au over 2.1 metres and 23.7 g/t Au over 2.1 metres. The first interval consists of 10% pyrite stringers, 5% pyrite clusters, 2% pyrite quartz-tourmaline veins, 1% pyrite in quartz-carbonate veins and 1% disseminated pyrite hosted in a strong sericite altered rhyolite. The second interval consists of 8% pyrite and 1% chalcopyrite in ptygmatic quartz-tourmaline veins and 1% pyrite with quartz-carbonate veins hosted at the contact between a fuchsite altered gabbro and a moderate sericite altered porphyritic felsic dike. The third interval consists of local visible gold, 30% pyrite in ptygmatic quartz-tourmaline veins, 7% pyrite clusters and 2% disseminated pyrite hosted in a moderate sericite and silica altered fragmental rhyolite.

OSK-W-19-961-W1 intersected 6.54 g/t Au over 2.0 metres in Lynx. Mineralization consists of 1% pyrite clusters and stringers in a weak sericite altered rhyolite.

OSK-W-19-991-W3 intersected 5.34 g/t Au over 2.0 metres and 9.00 g/t Au over 2.6 metres in Lynx Extension. The first interval consists of 5% pyrite stringers in a strongly sericitized, weakly silicified porphyritic felsic dike. The second interval consists of 6% disseminated and stringer pyrite in a weakly bleached and carbonate altered rhyolite at the contact with a bleached gabbro.

OSK-W-19-991-W5 intersected four intervals in Lynx Extension: 8.82 g/t Au over 2.0 metres, 5.77 g/t Au over 2.1 metres, 3.42 g/t Au over 3.0 metres and 16.8 g/t Au over 4.7 metres. The first interval consists of local visible gold in a quartz-carbonate-tourmaline vein and 1% pyrite in a weak chlorite altered gabbro. The second interval consists of trace pyrite-tourmaline stringers in a moderate sericite and weak silica altered rhyolite. Both the third and fourth intervals consist of 7% pyrite with pervasive silica flooding, 3% pyrite clusters and stringers, and trace disseminated pyrite hosted in a moderately bleached and locally fuchsite altered gabbro or a moderate silica and weak sericite rhyolite.

OSK-W-18-1550 intersected 284 g/t Au over 3.2 metres in Lynx. Mineralization consists of disseminated, fracture filled, and clustered local visible gold, 1% disseminated pyrite and trace sphalerite in quartz veins hosted in a moderate sericite and weak fuchsite altered rhyolite.

OSK-W-18-1582 intersected 6.64 g/t Au over 2.0 metres in Lynx. Mineralization consists of local native silver, 3% pyrite, 2% sphalerite and 1% chalcopyrite with smoky quartz veins hosted in a moderate sericite altered rhyolite.

OSK-W-18-1628 intersected 9.92 g/t Au over 4.3 metres and 21.0 g/t Au over 3.4 metres in Lynx. The first interval consists of up to 2% pyrite stringers and clusters in a moderate sericite and weak silica altered porphyritic felsic dike. The second interval consists of local visible gold, 5% pyrite stringers, and smoky quartz veins in a weak silica altered rhyolite in contact with a weak chlorite and fuchsite altered gabbro.

OSK-W-18-1681 intersected 61.6 g/t Au over 4.1 metres in Lynx. Mineralization consists of up to 25% pyrite with pervasive silica flooding, quartz-tourmaline veins, quartz-carbonate veins, 2% pyrite stringers and trace sphalerite and chalcopyrite hosted in a moderate chlorite altered gabbro.

OSK-W-19-1169-W3 intersected four intervals in Lynx: 9.47 g/t Au over 2.2 metres, 7.62 g/t Au over 2.0 metres, 22.3 g/t Au over 7.2 metres and 9.02 g/t Au over 4.9 metres. The first interval consists of local visible gold with quartz-carbonate veins, 10% disseminated and stringer pyrite hosted in a moderate chlorite altered gabbro. The second interval consists of 6% disseminated pyrite and 1% pyrite clusters in a quartz-carbonate vein in a gabbro with local chlorite and fuchsite alteration. The third and fourth intervals contain 4% disseminated pyrite and trace sphalerite in a strongly bleached rhyolite with tourmaline-quartz veins.

OSK-W-19-1272 intersected three intervals in Triple Lynx: 3.80 g/t Au over 2.0 metres, 3.44 g/t Au over 3.2 metres and 6.84 g/t Au over 2.7 metres. The first interval consists of pyrite clusters in a moderate silica and weak sericite altered porphyritic felsic dike. The second interval consists of disseminated pyrite, quartz-tourmaline veins and trace chalcopyrite hosted in a moderate silica and weak sericite altered rhyolite. The last interval contains 7% pyrite stringers and 2% chalcopyrite clusters hosted in a felsic intrusion.

OSK-W-19-1272-W1 intersected 9.71 g/t Au over 2.3 metres in Triple Lynx. Mineralization consists of 3% disseminated pyrite, 2% pyrite stringers and 1% ptygmatic tourmaline veins in a strong sericite and moderate altered rhyolite.

OSK-W-19-1386-W7 intersected 19.3 g/t Au over 2.5 metres and 26.9 g/t Au over 3.1 metres in Lynx. The first interval consists of 8% disseminated, clustered, and stringer pyrite in a strongly chloritized and fuchsite altered gabbro. The second interval consists of local visible gold in pervasive silica flooding, 6% disseminated, clustered, and stringer pyrite and trace chalcopyrite hosted in a strongly sericitized and silicified fragmental felsic dike.

OSK-W-19-1386-W8 intersected 25.6 g/t Au over 2.0 metres in Lynx. Mineralization consists of up to 10% disseminated, clustered, and stringer pyrite in a strong sericite altered fragmental felsic intrusion.

OSK-W-19-1386-W9 intersected 35.5 g/t Au over 2.3 metres in Lynx. Mineralization consists of local visible gold and 2% disseminated chalcopyrite in a quartz-tourmaline vein, and 5% pyrite clusters hosted in a strong sericite and silica altered, weak fuchsite altered gabbro in contact with a porphyritic felsic dike.

OSK-W-19-1414-W7 intersected 13.6 g/t Au over 7.1 metres in Lynx. Mineralization consists of 5% pyrite stringers locally associated with quartz-tourmaline veins in a weak silica altered and bleached rhyolite at the contact with a moderate carbonate-chlorite and weak fuchsite altered gabbro.

OSK-W-19-1419-W1 intersected 8.63 g/t Au over 6.0 metres in Lynx. Mineralization consists of 2% pyrite clusters in a moderate silica-sericite-fuchsite altered gabbro.

OSK-W-19-1453-W2 intersected 12.2 g/t Au over 2.2 metres in Lynx. Mineralization consists of 8% disseminated pyrite, 5% quartz-carbonate stockwork veins and 3% ptygmatic tourmaline veins hosted in a weak silica, fuchsite and strong sericite altered gabbro.

OSK-W-19-1539-W1 intersected 16.4 g/t Au over 2.0 metres in Lynx. Mineralization consists of trace disseminated pyrite in a weak sericite and silica altered rhyolite.

OSK-W-19-1711-W3 intersected 28.3 g/t Au over 2.0 metres and 5.71 g/t Au over 2.0 metres in Lynx. The first interval consists of local visible gold in quartz-tourmaline veins and 5% disseminated pyrite hosted in a strong chlorite altered gabbro. The second interval consists of 3% disseminated and stringer pyrite with smoky quartz veins, hosted in a strong chlorite, fuchsite and weak silica altered gabbro.

OSK-W-19-1857-W4 intersected 6.33 g/t Au over 3.6 metres in Lynx Extension. Mineralization consists of 2% stringer, disseminated and clustered pyrite hosted in a moderate sericite and carbonate altered gabbro.

OSK-W-19-1857-W6 intersected 30.8 g/t Au over 11.9 metres in Lynx Extension. Mineralization consists of local visible gold in silica and fuchsite patches, up to 10% stringer, disseminated and clustered pyrite, 2% chalcopyrite clusters and 3% sphalerite stringers. Tourmaline ptygmatic veins are associated with the mineralization. Mineralization is hosted in a strong fuchsite and moderate silica altered gabbro in contact with a string silica altered rhyolite.

OSK-W-19-1921-W1 intersected 5.78 g/t Au over 2.6 metres in Lynx. Mineralization consists of 1% disseminated and clustered pyrite in a weak sericite and silica altered porphyritic felsic dike.

OSK-W-19-1921-W2 intersected three intervals in Lynx: 3.67 g/t Au over 2.6 metres, 5.52 g/t Au over 3.0 metres and 5.67 g/t Au over 3.6 metres. The first interval consists of 2% disseminated and clustered pyrite and 1% pyrite-tourmaline stringers hosted in a moderate sericite and fuchsite altered gabbro at the contact with a sericitized rhyolite. The second interval consists of 1% interstitial and clustered pyrite with 25% quartz-carbonate veins in a moderate sericite, chlorite and strong silica altered gabbro. The third interval consists of trace pyrite stringers in a weak silica altered rhyolite.

OSK-W-19-1932-W3 intersected 6.65 g/t Au over 2.1 metres in Lynx. Mineralization consists of 3% disseminated pyrite in a quartz-tourmaline vein and hosted in a moderate sericite altered fragmental felsic dike.

OSK-W-19-1942-W1 intersected 7.16 g/t Au over 3.0 metres and 12.8 g/t Au over 2.0 metres in Lynx. Both intervals consist of disseminated pyrite in a moderate sericite and weak silica altered rhyolite.

OSK-W-19-1948 intersected 7.06 g/t Au over 3.5 metres and 5.98 g/t Au over 2.0 metres in Lynx. The first interval consists of 3% pyrite stringers in a moderate chlorite and weak silica-sericite altered gabbro. The second interval consists of 2% disseminated pyrite in a moderate chlorite, weak silica and sericite altered rhyolite.

OSK-W-19-1949-W2 intersected 288 g/t Au over 2.0 metres in Lynx. Mineralization consists of local visible gold and electrum, 10% pyrite in quartz veinlets, and trace chalcopyrite and arsenopyrite at the contacts between a locally bleached and fuchsite altered gabbro and a moderate silica altered rhyolite.

OSK-W-19-1952 intersected four interval in Lynx: 28.4 g/t Au over 2.9 metres, 4.67 g/t Au over 4.0 metres, 14.2 g/t Au over 5.1 metres and 21.1 g/t Au over 4.7 metres. The first interval consists of local visible gold, 5% pyrite stringers and clusters and 1% disseminated pyrite with silica flooding and quartz-tourmaline veins in a moderate sericite and fuchsite altered gabbro at the contact with a weak sericite and moderate silica altered porphyritic felsic intrusion. The second interval consists of 5% pyrite clusters and stringers, and 1% disseminated pyrite in a weakly sericite and silica altered rhyolite. The third and fourth intervals consist of local visible gold, 7% disseminated, clustered and stringer pyrite, and 1% sphalerite clusters hosted in a moderate silica altered rhyolite.

OSK-W-19-1962 intersected 5.41 g/t Au over 2.0 metres and 5.83 g/t Au over 2.3 metres in Lynx. The first interval consists of up to 7% disseminated pyrite and local visible gold with sericite-quartz-ankerite patches in a strong sericite and silica altered rhyolite in contact with a moderate chlorite-sericite altered gabbro. The second interval consists of 3% disseminated pyrite associated with quartz-tourmaline veins hosted in a moderately to strongly sericitized-chloritized and locally bleached gabbro.

OSK-W-19-1963-W2 intersected 13.8 g/t Au over 5.2 metres and 13.0 g/t Au over 4.0 metres in Lynx Extension. The first interval consists of up to 8% pyrite with pervasive silica flooding and quartz-carbonate veins with 3% pyrite and trace molybdenite hosted in a moderate sericite and silica altered rhyolite. The second interval consists of up to 7% disseminated, stringer, fracture filled, and clustered pyrite hosted in a weakly to moderately silicified rhyolite at the contact with a moderately bleached and weak fuchsite altered gabbro.

OSK-W-19-1963-W3 intersected 27.5 g/t Au over 7.1 metres in Lynx Extension. Mineralization consists of local visible gold, 4% disseminated and stringer pyrite, trace chalcopyrite, and 1% sphalerite clusters with pervasive-silica flooding hosted in a moderately sericitized rhyolite.

OSK-W-19-1963-W4 intersected 49.4 g/t Au over 4.2 metres and 14.4 g/t Au over 4.7 metres in Lynx Extension. The first interval consists of disseminated or fracture filled local visible gold, 3% pyrite clusters, and 1% disseminated pyrite hosted in a moderate fuchsite altered gabbro. The second interval consists of 8% pyrite clusters and stringers, and 2% pyrite stringers associated with ptygmatic tourmaline veinlets hosted in a gabbro and rhyolite with weak fuchsite and silica alteration and weak to strong sericite alteration.

OSK-W-19-1963-W5 intersected 19.5 g/t Au over 3.8 metres in Lynx Extension. Mineralization consists of up to 15% disseminated and fracture filled quartz-tourmaline ptygmatic veins hosted in a moderate sericite and strong silica altered gabbro.

OSK-W-19-1992-W1 intersected 14.3 g/t Au over 5.9 metres in Lynx. Mineralization consists of 15% pyrite stringers, 10% pyrite clusters, and 5% disseminated pyrite at the contact between a strongly bleached, moderately sericitized, and weakly silicified gabbro and an andesite.

OSK-W-19-2026 intersected 8.77 g/t Au over 10.1 metres in Triple Lynx. Mineralization consists of disseminated, clustered, and stringer pyrite with trace sphalerite associated with pervasive silica flooding hosted in a moderately sericitized and silicified rhyolite.

OSK-W-19-2026-W1 intersected five intervals in Triple Lynx: 3.43 g/t Au over 2.1 metres, 3.70 g/t Au over 5.7 metres, 9.56 g/t Au over 2.1 metres, 6.89 g/t Au over 2.0 metres and 5.04 g/t Au over 2.2 metres. The first interval consists of up to 10% pyrite-tourmaline with pervasive silica flooding and 5% disseminated pyrite hosted in strong silica altered porphyritic felsic dike. The second interval consists of 3% pyrite-tourmaline stringers in a moderate sericite and silica altered rhyolite. The third interval consists of up to 15% pyrite-tourmaline in fracture filling with pervasive silica flooding veins hosted in strong fuchsite and sericite altered gabbro in contact with a rhyolite. The fourth interval consists of 5% pyrite stringers and 3% disseminated pyrite in a weak sericite and silica altered rhyolite. The last interval consists of 5% stringer, clustered and disseminated pyrite associated with pervasive silica zone hosted in a weak chloritized and sericite altered rhyolite.

OSK-W-19-2035 intersected 14.1 g/t Au over 4.1 metres in Lynx. Mineralization consists of local visible gold and 5% disseminated pyrite associated with silica-chlorite fracture filling and trace chalcopyrite in a quartz-carbonate vein and a quartz-tourmaline vein hosted in strongly silicified and moderately chloritized and sericitized gabbro.

OSK-W-19-2043 intersected 3.48 g/t Au over 2.2 metres in Lynx. Mineralization consists of 10% pyrite clusters in a strongly bleached and sericitized gabbro.

OSK-W-19-2048 intersected 12.2 g/t Au over 2.0 metres in Lynx. Mineralization consists of 5% pyrite stringers, 8% disseminated pyrite and trace chalcopyrite clusters in a moderate sericite and chlorite altered gabbro with local pervasive silica flooding.

OSK-W-19-2064 intersected 4.13 g/t Au over 2.2 metres in Lynx. Mineralization consists of 3% pyrite stringers, 1% pyrite clusters and 1% disseminated pyrite in a moderately silicified and weakly sericitized rhyolite.

OSK-W-19-2068 intersected 56.0 g/t Au over 2.3 metres in Lynx. Mineralization consists of local visible gold, disseminated or fracture filled native silver, 5% pyrite clusters and stringers, 1% disseminated chalcopyrite and trace sphalerite in pervasive silica flooding or crustiform quartz veins with local fuchsite alteration and 3% ptygmatic tourmaline stringers. Mineralization is hosted in a strongly silicified and moderately sericitized rhyolite.

OSK-W-19-2068-W1 intersected 8.85 g/t Au over 8.7 metres and 7.15 g/t Au over 2.3 metres in Lynx. Both intervals consist of up to 15% pyrite stringers locally associated with ptygmatic tourmaline veins and clusters, trace sphalerite and disseminated chalcopyrite hosted in a moderate chlorite, sericite and fuchsite altered basalt.

OSK-W-19-2077 intersected 6.10 g/t Au over 3.5 metres and 10.7 g/t Au over 6.0 metres in Triple Lynx. The first interval consists of 1% disseminated pyrite and ptygmatic tourmaline veins hosted in a moderate silica altered rhyolite. The second interval contains 15% disseminated pyrite, 2% pyrite in tourmaline ptygmatic veins, 1% pyrite as clusters and stringers, and trace sphalerite, hosted in a strongly silicified basalt.

WST-19-0121 intersected 9.53 g/t Au over 2.0 metres in Lynx. Mineralization consists of local visible gold and up to 15% pyrite stringers associated with pervasive silica flooding hosted in a strongly silica, weak fuchsite altered rhyolite in contact with a fragmental felsic dike. WST-19-0121 was drilled from underground drill station RE-195-265-O located 195 metres below surface from section 3475E.

WST-19-0124 intersected 37.2 g/t Au over 4.7 metres in Lynx. Mineralization consists of local visible gold and pyrite-tourmaline stringers associated with smoky quartz veins and trace sphalerite hosted in a sericitized and silicified rhyolite. WST-19-0124 was drilled from underground drill station RE-195-265-O located 195 metres below surface from section 3475E.

WST-19-0144 intersected 47.2 g/t Au over 2.4 metres in Lynx. Mineralization consists of local visible gold and 6% disseminated pyrite with strong pervasive silica flooding and quartz-carbonate veins hosted in a moderate silica altered rhyolite. WST-19-0144 was drilled from underground drill station AN-195-265-S located 195 metres below surface from section 3500E.

WST-19-0145 intersected 33.2 g/t Au over 2.6 metres and 12.2 g/t Au over 4.1 metres in Lynx. The first interval consists of 2% pyrite stringers and quartz-tourmaline veins in a moderate chlorite altered andesite. The second interval consists of up to 15% pyrite stringers with pervasive silica flooding hosted in a strong silica altered rhyolite. WST-19-0145 was drilled from underground drill station BM-200-195-S located 200 metres below surface from section 3525E.

WST-19-0154 intersected 95.5 g/t Au over 2.2 metres in Lynx. Mineralization consists of local visible gold and 10% pyrite associated with pervasive silica flooding hosted at the contact between a strongly sericitized and chloritized gabbro and a felsic intrusion. WST-19-0154 was drilled from underground drill station BM-200-195-S located 200 metres below surface from section 3525E.

WST-19-0195 intersected 3.24 g/t Au over 2.1 metres in Lynx. Mineralization consists of up to 12% pyrite associated with quartz-tourmaline veins and 2% clustered and disseminated pyrite hosted in a weakly sericitized rhyolite. WST-19-0195 was drilled from underground drill station AN-225-190-O located 225 metres below surface from section 3425E.

WST-19-0202 intersected 9.84 g/t Au over 2.4 metres and 453 g/t Au over 2.0 metres in Lynx. The first interval consists of up to 5% pyrite and smoky quartz-carbonate veins hosted in a moderately sericitized rhyolite. The second interval consists of local visible gold inside a smoky quartz vein, up to 15% disseminated pyrite and 3% pyrite stringers hosted in a moderately sericitized rhyolite. WST-19-0202 was drilled from underground drill station AN-225-190-O located 225 metres below surface from section 3425E.

WST-19-0203 intersected 6.56 g/t Au over 3.5 metres in Lynx. Mineralization consists of 4% disseminated and clustered pyrite associated with quartz-tourmaline veins hosted in a weakly chloritized rhyolite. WST-19-0203 was drilled from underground drill station AN-225-190-O located 225 metres below surface from section 3425E.

WST-19-0205 intersected three interval in Lynx: 5.84 g/t Au over 2.0 metres, 3.11 g/t Au over 2.0 metres and 71.8 g/t Au over 2.0 metres. The first and second intervals consist of up to 5% disseminated pyrite associated with crustiform quartz-carbonate veinlets and up to 1% sphalerite in pervasive silica flooding hosted in a moderately sericitized rhyolite or a moderate chlorite altered felsic dike. The last interval consists of local visible gold filling a fracture in a crustiform vein, 1% disseminated chalcopyrite and 2% disseminated pyrite hosted in a moderately chloritized gabbro. WST-19-0205 was drilled from underground drill station AN-225-190-O located 225 metres below surface from section 3425E.

WST-19-0206 intersected 44.5 g/t over 2.0 metres and 3.25 g/t Au over 2.0 metres in Lynx. The first interval consists of local visible gold associated with 8% pyrite stringers and 1% disseminated sphalerite inside a smoky quartz vein with pervasive fuchsite crustiform quartz-carbonate veinlets hosted in a moderately sericitized rhyolite. The second interval consists of 1% disseminated pyrite in a moderate chlorite rhyolite. WST-19-0206 was drilled from underground drill station AN-225-190-O located 225 metres below surface from section 3425E.

WST-19-0207 intersected 7.45 g/t Au over 2.4 metres and 3.46 g/t Au over 2.0 metres in Lynx. The first interval consists of up to 8% disseminated pyrite and 4% sphalerite with crustiform quartz veins hosted in a weak sericite altered rhyolite. The second interval consists of 4% disseminated pyrite in a weak sericite altered rhyolite. WST-19-0207 was drilled from underground drill station AN-225-190-O located 225 metres below surface from section 3425E.

WST-19-0208 intersected 11.8 g/t Au over 2.0 metres in Lynx. Mineralization consists of 6% disseminated and clustered pyrite associated with quartz-tourmaline veins hosted in a weakly sericitized rhyolite. WST-19-0208 was drilled from underground drill station AN-225-190-O located 225 metres below surface from section 3425E.

WST-19-0209 intersected 3.65 g/t Au over 2.2 metres in Lynx. Mineralization consists of trace disseminated and clustered pyrite in a weak sericite and silica altered rhyolite. WST-19-0209 was drilled from underground drill station AN-225-190-O located 225 metres below surface from section 3425E.

WST-19-0217 intersected 3.17 g/t Au over 2.5 metres in Lynx. Mineralization consists of 7% disseminated pyrite with smoky quartz veins and 1% disseminated pyrite hosted in a weakly sericitized and silicified rhyolite. WST-19-0217 was drilled from underground drill station AN-225-190-O located 225 metres below surface from section 3425E.

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 Osisko's Windfall Lake gold project, who is a "qualified person" as defined by National Instrument 43-101 – Standards of Disclosure for Mineral Projects ("NI 43-101").

Quality Control and Reporting Protocols
True width determination is estimated at 55-80% 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 Lake 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 Lake 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 Quévillon area (over 2,700 square kilometres).

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. The information in this news release about the Windfall Lake gold deposit being one of the highest grade resource-stage gold projects in Canada; the significance of results from the new infill drilling and ongoing drill definition and expansion program at the Windfall Lake gold project; the significance of assay results presented in this news release; the deposit remaining open along strike and at depth; potential depth extensions of the mineralized zones down-plunge and at depth; the actual mineralization of local visible gold; the current drill program; the type of drilling included in the drill program; potential mineralization; the potential to extend mineralization up and down-plunge and at depth at the Windfall Lake gold deposit; the ability to realize upon any mineralization in a manner that is economic; the ability to complete any proposed exploration activities and the results of such activities, including the continuity or extension of any mineralization; and any other information herein that is not a historical fact may be "forward-looking information". Any statement that involves discussions with respect to 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", "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 forward-looking information is based on reasonable assumptions and estimates of management of the Corporation at the time such assumptions and estimates were made, and involves known and unknown risks, uncertainties and other factors which may cause the actual results, performance or achievements of Osisko to be materially different from any future results, performance or achievements expressed or implied by such forward-looking information. 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 drilling; property interests in the Windfall Lake gold project; the ability of the Corporation to obtain required approvals and complete transactions on terms announced; 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.

For further information please contact: John Burzynski
President and Chief Executive Officer Telephone: (416) 363-8653