Osisko Mining Inc. (TSX:OSK) is pleased to provide new infill drilling results from the ongoing drill definition and expansion program at its 100% owned Windfall Lake gold project located in the Abitibi greenstone belt, Urban Township, Eeyou Istchee James Bay, Québec. The 800,000 metre drill program commenced in late 2015. The program is now focussed on infill drilling within the main Windfall gold deposit and the adjacent Lynx deposit (located immediately NE of Windfall), and exploration and expansion drilling on main mineralized zones with several deep holes in progress to investigate the down-plunge areas in and around the Underdog and Lynx zones.

Significant new analytical results from 80 intercepts in 53 drill holes and one wedge focused on infill of the Main Windfall Lake and Lynx deposits and on deep-exploration targets are presented below.

Highlights from the new results include: 510 g/t Au over 5.2 metres in OSK-W-18-1639; 742 g/t Au over 2.2 metres in OSK-W-18-1589; 21.6 g/t Au over 19.4 metres in OSK-W-18-1655; 198 g/t Au over 2.0 metres in OSK-W-18-1638; 25.7 g/t Au over 8.9 metres in OSK-W-17-1313. Maps showing hole locations and full analytical results are available at www.osiskomining.com.

OSK-W-17-907 intersected 7.56 g/t Au over 4.9 metres related to a crustiform vein in Lynx.  Mineralization consists of local visible gold, up to 5% pyrite, and 1% molybdenite and sphalerite in quartz-carbonate crustiform veins injected in a gabbro.

OSK-W-17-936-W2 intersected 16.7 g/t Au over 2.4 metres in Caribou. Mineralization consists of 5% clustered pyrite and trace pyrite-tourmaline stringers in pervasive silica flooding within a strongly silicified porphyritic felsic dike.

OSK-W-17-958 intersected 36.5 g/t Au over 2.1 metres in Lynx. Mineralization consists of up to 5% pyrite-tourmaline stringers and disseminated pyrite in a gabbro with silica and fuchsite alteration.

OSK-W-18-1070 intersected 8.12 g/t Au over 2.8 metres in Zone 27. Mineralization consists of trace disseminated pyrite and a centimetre-scale quartz-carbonate vein in a sericitized rhyolite.

OSK-W-17-1119 intersected 5.63 g/t Au over 2.9 metres in Caribou.  Interval contains up to 10% pyrite stringers in a strongly chloritized gabbro with weak sericitization and silicification.

OSK-W-17-1143 intersected 20.4 g/t Au over 2.0 metres in Lynx. Mineralization contains local visible gold and 5% pyrite with pervasive silica flooding zone in a sericitized fragmental felsic unit.

OSK-W-17-1158 intersected 71.4 g/t Au over 2.0 metres in Bobcat. Mineralization consists of trace disseminated pyrite, trace quartz-carbonate veins in a chloritized and sericitized fragmental dike.

OSK-W-17-1186 intersected 18.0 g/t Au over 2.0 metres in Underdog. Mineralization consists of 25% pyrite with intense pervasive silica flooding hosted in a porphyritic felsic dike with moderate sericite alteration.

OSK-W-17-1313 intersected 25.7 g/t Au over 8.9 metres in Zone 27. Mineralization consists of up to 25% pyrite with intense silica flooding and trace sphalerite clusters at the silicified and sericitized contact between a porphyritic felsic dike and an andesite.

OSK-W-18-1440 intersected 6.61 g/t Au over 2.4 metres in Caribou. Mineralization contains 7% disseminated pyrite and trace pyrite stringers in an andesite with moderate chlorite and carbonate alteration and weak silica and sericite alteration.

OSK-W-18-1518 intersected 3.74 g/t Au over 3.0 metres in Caribou. Mineralization consists of 5% pyrite with pervasive silica flooding in a sericitized rhyolite.

OSK-W-18-1530 intersected 11.4 g/t Au over 2.0 metres in Lynx. Mineralization contains trace fragmental pyrite and trace pyrite stringers in a sericite, chlorite and silica altered fragmental felsic dike.

OSK-W-18-1552 intersected a vein returning 3.70 g/t Au over 2.0 metres in Lynx. Mineralization contains up to 20% pyrite stringers at the sericitized contact between a porphyritic felsic dike and an andesite.

OSK-W-18-1559 intersected 4.47 g/t Au over 2.0 metres in Zone 27. Mineralization consists of trace pyrite stringers and pyrite-quartz clusters in a chloritized andesite. 

OSK-W-18-1561 intersected 7.33 g/t Au over 2.2 metres in Lynx. Mineralization consists of trace disseminated pyrite and 90% quartz clusters over 40 cm in a strongly silicified rhyolite with light sericite and carbonate alteration.

OSK-W-18-1564 intersected 4.49 g/t Au over 2.0 metres and 4.71 g/t Au over 2.0 metres in Caribou. Mineralization consists of 2% disseminated pyrite and stringers hosted in a bleached and sericitized porphyritic dike or a chloritized andesite with carbonate and hematite alteration.

OSK-W-18-1589 intersected 742 g/t Au over 2.2 metres in Zone 27. Mineralization consists of local visible gold clusters within a pyrite-tourmaline stringer hosted in a moderately sericitized rhyolite.

OSK-W-18-1594 intersected 10.4 g/t Au over 2.6 metres in Zone 27. Mineralization consists of 10% to locally 60% pyrite stringers in a silicified and sericitized fragmental rhyolite.

OSK-W-18-1598 intersected 5.47 g/t Au over 2.2 metres in Lynx. Mineralization consists of 2% pyrite with quartz-carbonate ± tourmaline crustiform veins and 1% pyrite stringers in a bleached and fuchsite altered gabbro.

OSK-W-18-1613 intersected 8.12 g/t Au over 2.3 metres in Lynx. Mineralization consists of up to 5% pyrite with pervasive silica flooding in a moderately silica altered porphyritic felsic dike.

OSK-W-18-1618 intersected 3.00 g/t Au over 2.5 metres in Caribou. Mineralization consists of trace pyrite clusters in a moderately sericite altered rhyolite.

OSK-W-18-1622 intersected 16.0 g/t Au over 2.1 metres with in Zone 27. Mineralization consists of up 25% pyrite in stockwork in a chlorite-rich matrix and a local centimetre band of pyrite massive, hosted in a bleached andesite.

OSK-W-18-1623 intersected 6.51 g/t Au over 2.3 metres in Caribou. Mineralization consists of local visible gold and 25% pyrite-tourmaline stringers within a strongly silicified and moderately sericitized rhyolite.

OSK-W-18-1624 intersected 6.01 g/t Au over 2.9 metres and 7.97 g/t Au over 2.4 metres  in Caribou and  4.30 g/t Au over 4.8 metres in Zone 27. The first and second intervals contain 1% pyrite stringers and trace pyrite in quartz or quartz-tourmaline veins and locally 5% pyrite infilling fractures within a moderately sericitized and silicified rhyolite. The third interval contains 5% pyrite stringers, 1% disseminated pyrite and trace chalcopyrite in a strongly bleached andesite.

OSK-W-18-1627 intersected a crustiform vein returning 9.25 g/t Au over 2.4 metres. Mineralization consists of 2% pyrite stringers in a metre-scale crustiform vein composed of quartz-carbonate with 1% ptygmatic tourmaline veinlets hosted in a lightly fuchsite altered gabbro.

OSK-W-18-1628 intersected 57.5 g/t Au over 2.6 metres and 23.0 g/t Au over 2.1 metres in Lynx. Both intervals contain local visible gold and up to 7% disseminated pyrite and stringers in a strongly sericite, locally silica and fuchsite altered gabbro.

OSK-W-18-1631 intersected 4.50 g/t Au over 5.1 metres in Caribou. Mineralization consists of 10% pyrite stringers hosted in a porphyritic felsic dike and gabbroic unit.

OSK-W-18-1632 intersected 3.28 g/t Au over 2.5 metres in Zone 27. Mineralization consists of 10% pyrite stockwork and 3% disseminated pyrite in a sericitized andesite.

OSK-W-18-1634 intersected 6.29 g/t Au over 3.9 metres in Caribou. Mineralization consists of up to 25% pyrite clusters with local patches of silica flooding, quartz-carbonate veins and ptygmatic tourmaline veinlets in a moderately sericitized rhyolite.

OSK-W-18-1638 intersected  198 g/t Au over 2.0 metres and 14.6 g/t Au over 2.0 metres in Lynx. The first interval is composed of 6% pyrite stringers and clusters, 1% pyrite in two 30-centimetre scale quartz-carbonate crustiform veins, 1% pyrite in ptygmatic tourmaline veinlets hosted in bleached and fuchsite altered gabbro. The second interval contains local visible gold with 3% pyrite stringers and trace pyrite in ptygmatic tourmaline veins hosted in a silicified and fuchsite altered gabbro.

OSK-W-18-1639 intersected three intervals: 3.27 g/t Au over 3.5 metres, 510 g/t Au over 5.2 metres and 4.87 g/t Au over 2.0 metres in Lynx. The first interval contains 1% pyrite stringers with 70% quartz clusters in a chlorite and carbonate altered gabbro. The second interval contains local visible gold in veinlets and as disseminated grains and 5% pyrite stringers in a crustiform vein hosted in a sericite and fuchsite altered gabbro. The third interval contains local visible gold and 3% pyrite stringers in a sericitized and weakly fuchsite altered gabbro.

OSK-W-18-1640 intersected two intervals: 6.27 g/t Au over 2.3 metres and 50.0 g/t Au over 3.0 metres in Caribou. The first interval contains 8% pyrite stockwork with pervasive silica flooding, 1% sphalerite and trace chalcopyrite hosted in a moderately bleached and sericitized felsic porphyritic dike. The second interval contains 35% semi-massive pyrite within a bleached, moderately to strongly sericite and silica-altered andesite and felsic porphyritic dike.

OSK-W-18-1642 intersected 12.8 g/t Au over 3.8 metres in Caribou and 5.95 g/t Au over 2.3 metres in Zone 27. The first interval contains 20% (to locally 60%) pyrite ± tourmaline stringers with trace sphalerite hosted in a strongly silicified and sericitized rhyolite and strongly sericitized andesite injected locally by quartz-carbonate-tourmaline veins. The second interval contains up to 15% disseminated pyrite, stringers or clusters with quartz-carbonate veins and quartz tourmaline breccia in a bleached and sericitized and chloritized gabbro.

OSK-W-18-1643 intersected 5.99 g/t Au over 2.7 metres in Bobcat. Mineralization consists of 3% pyrite-tourmaline stringers at the margins of quartz-carbonate veins hosted in a weakly sericitized rhyolite.

OSK-W-18-1644 intersected two intervals: 3.32 g/t Au over 2.6 metres in Caribou and 41.1 g/t Au over 3.3 metres in Zone 27. The first interval contains 5% pyrite with quartz-carbonate veins, 8% pyrite stockwork with pervasive silica flooding, 1% sphalerite and trace chalcopyrite hosted in a moderately bleached and sericitized felsic porphyritic intrusion. The second interval contains local visible gold, up to 30% disseminated, stringer, or cluster pyrite with trace chalcopyrite with silica patches and trace ptygmatic tourmaline veinlets hosted in a bleached and moderately to strongly sericite altered andesite.

OSK-W-18-1645 intersected 5.39 g/t Au over 2.0 metres in Lynx. Mineralization consists of 5% pyrite and 1% sphalerite with pervasive silica flooding in a gabbro.

OSK-W-18-1646 intersected two intervals: 7.51 g/t Au over 2.4 metres in Caribou and 6.28 g/t Au over 2.7 metres in Zone 27. The first interval contains 5% pyrite in ptygmatic tourmaline veins in a moderately sericite, chlorite and fuchsite altered porphyritic felsic dike. The second interval contains 3% disseminated and cluster pyrite in chloritized and silicified andesite alternating with sericitized porphyritic felsic dike.

OSK-W-18-1647 intersected 17.4 g/t Au over 2.0 metres in Lynx. Mineralization consists of trace pyrite in ptygmatic tourmaline veinlets in a crustiform carbonate vein overprinted by silica and fuchsite alteration hosted in a gabbro.

OSK-W-18-1648 intersected two intervals: 3.74 g/t Au over 2.3 metres in Caribou and 9.19 g/t Au over 4.4 metres in Zone 27. The first interval contains 7% pyrite with quartz-carbonates veins in a weakly sericitized porphyritic felsic dike. The second interval contains 1% pyrite stringers and 2% disseminated pyrite in a moderately sericite and fuchsite altered porphyritic felsic dike at the contact with Red Dog intrusion.

OSK-W-18-1649 intersected three intervals: 4.61 g/t Au over 2.0 metres and 48.4 g/t Au over 2.0 metres in Caribou and 14.9 g/t Au over 2.1 metres in Zone 27. The first interval contains 3% pyrite stringers, 2% sphalerite stringers and 3% disseminated pyrite in a sericite and silica altered porphyritic felsic dike. The second interval contains 3% disseminated pyrite and clusters with 2% ptygmatic tourmaline veins in a chloritized and sericitized porphyritic felsic dike. The third interval contains local visible gold, 7% pyrite with silica flooding, 2% pyrite stringers, 2% pyrite-tourmaline stringers and 3% disseminated pyrite in sericitized and silicified fragmental porphyritic felsic dike.

OSK-W-18-1650 intersected two intervals: 6.11 g/t Au over 4.1 metres and 4.22 g/t Au over 3.2 metres in Zone 27. Mineralization consists of 5% pyrite-tourmaline stringers and 2% pyrite with silica flooding in a moderately sericitized and bleached porphyritic felsic dike.

OSK-W-18-1651 intersected fourth intervals: 4.01 g/t Au over 2.2 metres and 3.68 g/t Au over 2.0 metres in Caribou, and 7.39 g/t Au over 2.0 metres and 3.45 g/t Au over 4.7 metres in Zone 27.  The first and second intervals contain 15% semi-massive pyrite, 3% pyrite stringers and clusters and 3% disseminated pyrite within a sericitized and silicified rhyolite or porphyritic felsic dike. The third interval contains 5% pyrite stringers and 5% disseminated pyrite in a bleached and moderately silicified and sericitized andesite with weak fuchsite alteration. The fourth interval contains up to 40% semi-massive pyrite, 10% pyrite stringers, 10% clustered or disseminated pyrite, 2% pyrite in smoky quartz veins or ptygmatic tourmaline veinlets and trace chalcopyrite hosted in sericitized, silicified and bleached porphyritic dike and sericitized andesite.

OSK-W-18-1653 intersected 4.15 g/t Au over 2.6 metres in Zone 27. Mineralization is composed of 5% pyrite-tourmaline clusters, 1% disseminated pyrite, trace pyrite with quartz-tourmaline veins and up to 10% pyrite with pervasive silica flooding. Host rocks are a sericitized rhyolite and a sericitized porphyritic felsic dike.

OSK-W-18-1654 intersected 9.10 g/t Au over 2.0 metres in Zone 27. Mineralization consists of up to 5% pyrite stringers with local tourmaline, 1% pyrite in quartz-tourmaline veins and trace chalcopyrite in a silicified and sericitized porphyritic felsic dike.

OSK-W-18-1655 intersected three intervals: 4.99 g/t Au over 2.3 metres, 21.6 g/t Au over 19.4 metres and 11.1 g/t Au over 2.3 metres in Zone 27. The first interval contains 5% pyrite with pervasive silica flooding, 2% pyrite stringers and 1% disseminated pyrite in a sericitized and silicified rhyolite at the contact with a porphyric felsic dike. The second interval contains local visible gold, up to 20% pyrite stockwork, 10% disseminated pyrite, up to 5% disseminated sphalerite and 1% disseminated chalcopyrite. Host is a bleached, silica and sericite altered porphyric felsic intrusion. The third interval contains 3% pyrite with quartz-tourmaline veins and 7% disseminated pyrite in a faulted zone at contact between a porphyritic felsic dike and an andesite.

OSK-W-18-1656 intersected 8.28 g/t Au over 5.8 metres in Lynx. Mineralization consists of 2% pyrite stringers in quartz-tourmaline-carbonate veins hosted in a chloritized gabbro.

OSK-W-18-1657 intersected 5.00 g/t Au over 2.3 metres and 8.41 g/t Au over 2.1 metres in Lynx. The first interval contains up to 7% disseminated pyrite in a strongly silica altered rhyolite. The second interval contains 10% disseminated pyrite and pyrite-tourmaline stringers in a strongly sericitized, chloritized and bleached gabbro with local silica-fuchsite alteration.

OSK-W-18-1659 intersected 4.09 g/t Au over 6.8 metres and 5.88 g/t Au over 5.2 metres in Zone 27. The first interval contains 7% pyrite stringers and up to 40% semi-massive pyrite (over 1.5 metres) with silica alteration in a sericitized andesite and porphyritic felsic dike. The second interval contains local visible gold with locally 30% massive pyrite and 10% pyrite stringers in a strongly sericitized andesite and porphyritic felsic intrusion.

OSK-W-18-1660 intersected 7.19 g/t Au over 2.2 metres in Caribou. Mineralization consists of up to 6% disseminated and stringer pyrite and 1% sphalerite in quartz veins hosted in a strongly silicified porphyritic felsic dike.

OSK-W-18-1661 intersected 9.28 g/t Au over 2.1 metres in Zone 27. Mineralization consists of up to 20% disseminated pyrite, 10% pyrite stringers, 3% disseminated sphalerite, trace of pyrite-tourmaline stringers and trace disseminated chalcopyrite in a bleached, sericitized and locally silicified porphyritic felsic intrusion.

OSK-W-18-1662 intersected two intervals: 4.08 g/t Au over 3.6 metres and 14.8 g/t Au over 9.0 metres in Zone 27.  The first interval contains 2% pyrite stringers, 3% disseminated pyrite, 2% pyrite in quartz vein in a strongly sericitized porphyritic felsic dike at contact with a sericitized andesite. The second interval contains local visible gold, up to 5% pyrite stringers in a strongly sericitized and weakly silicified porphyritic felsic dike.

OSK-W-18-1665 intersected 4.65 g/t Au over 2.7 metres in Zone 27.  Mineralization is composed of 30% pyrite-tourmaline stringers with local patchy silica alteration hosted in a sericitized porphyritic felsic dike and a sericitized rhyolite.

OSK-W-18-1669 intersected 4.75 g/t Au over 3.4 metres in Zone 27. Mineralization consists of up to 10% pyrite stringers and clusters, 6% disseminated pyrite in a breccia tourmaline quartz zone. Host rocks are a sericitized porphyritic felsic dike and a bleached and sericitized fragmental andesite.

OSK-W-18-1671 intersected four intervals: 12.7 g/t Au over 2.3 metres, 5.64 g/t Au over 3.9 metres, 24.1 g/t Au over 2.5 metres and 3.52 g/t Au over 2.3 metres in Zone 27. The first interval contains 12% pyrite stringers and clusters with local silica flooding in moderately sericitized and bleached andesite. The second, third and fourth intervals contain 30 to 70% pyrite-tourmaline stringers and local quartz veins hosted in a sericitized and bleached andesite and a porphyritic felsic dike with moderate fuchsite, and weak silica-sericite and chlorite alteration.

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.

Quality Control and Reporting Protocols

True width determination is currently unknown but 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 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), comprises 2,382,000 tonnes at 7.85 g/t Au (601,000 ounces) in the indicated mineral resource category and 10,605,000 tonnes at 6.70 g/t Au (2,284,000 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”). The Windfall Lake Technical Report is 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 only 30 metres from surface in some areas and as deep as 1,200 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 Urban Barry area and nearby Quevillon area (over 3,300 square kilometres), a 100% interest in the Marban project located in the heart of Québec’s prolific Abitibi gold mining district, and properties in the Larder Lake Mining Division in northeast Ontario, including the Jonpol and Garrcon deposits on the Garrison property, the Buffonta past producing mine and the Gold Pike mine property. The Corporation also holds interests and options in a number of additional properties in northern Québec and Ontario.