Osisko Mining Inc. (TSX:OSK) is pleased to provide new results from the ongoing Triple 8 deep-hole exploration program at its 100% owned Windfall Lake gold project located in the Abitibi greenstone belt, Urban Township, Eeyou Istchee James Bay, Québec.

In May 2018 Osisko commenced deep exploration drilling to investigate the potential for depth extensions of the main mineralized zones, as well as to further test the intrusion-related geological model for the Windfall deposit.  In July 2018 Osisko discovered “Triple 8”, a developing new corridor of mineralization at the Windfall deposit, at 1,425 metres vertical depth.

Today’s new drill results confirm and expand on the initial discovery (please see Osisko news releases dated July 11, 2018 and September 13, 2018).  Drill hole OSK-W-18-1783 tested the continuity at the mid-point between OSK-W-18-1603 (Triple 8 discovery hole) and gold mineralization intersected in a similar setting in OSK-W-18-1616-W1 (see Osisko news release dated August 7, 2018).

OSK-W-18-1783 encountered three distinct altered intervals between 1,819 metres and 1,945 metres downhole, each averaging approximately 10 metres width.  Significant results from the three gold bearing intervals include 38.4 g/t Au over 2.0 metres and 16.0 g/t Au over 2.3 metres and.  Geometry is still being interpreted, however mineralization is open in all directions. Sericite and silica alteration are hosted within an andesite and gabbro package, surrounded by peripheral chlorite – biotite +/- garnet alteration (identical to that encountered in the Triple 8 discovery hole 350 metres to the north, and in hole OSK-W-1616-W1, 400 metres to the south). The mineralized intervals contain disseminated and stringer pyrite with local visible gold, and trace pyrrhotite and chalcopyrite.

Osisko President and CEO John Burzynski commented: “We have had excellent high-grade results now from the three deep holes and wedges that have intersected the Triple 8 area, including todays new results.  Triple 8 is shaping up to be a significant addition to Windfall, providing good potential for the future growth of the deposit at depth.  Our wide spaced exploration drilling has so far defined this new corridor over a strike length of 750 metres.  We intend to conduct downhole geophysical surveys and additional drilling in the coming months, to help define the relationships between the mineralized intercepts and further define the full scale of the mineralized corridor.  Overall, our large ongoing drill campaign has so far shown the Windfall mineralized system to have a strike length of 3.5 kilometres and a depth extent of 1.8 kilometres.  The system remains open in all directions, and we are very confident that we can continue to grow the deposit as we advance our drilling along strike and at depth.”

Today’s results include currently available significant analytical results from OSK-18-1783, and new analytical results from OSK-W-1603-W1 and OSK-W-1616-W2.  Maps showing drill hole locations and analytical results are available at www.osiskomining.com.  

OSK-W-18-1783 intersected mineralization in three sericite-silica altered zones hosted within a pervasively chlorite-biotite-garnet altered andesite. The first interval (4.6 g/t Au over 3.3 metres) has moderate sericite alteration and contains up to 10% disseminated pyrite, with local pyrite clusters and stringers. The second interval (38.4 g/t Au over 2.0 metres) has strong sericite and moderate silica alteration, and is interpreted as the strike extension from the Triple 8 discovery hole. This interval contains up to 10% pyrite stringers, 5% disseminated pyrite, local visible gold and trace pyrrhotite. The third interval (16.0 g/t Au over 2.3 metres) has moderate sericite and silica alteration, and contains up to 10% pyrite stringers, 5% disseminated pyrite, local visible gold and trace pyrrhotite and chalcopyrite.

OSK-W-18-1603-W1 intersected 18.0 g/t Au over 2.4 metres within a moderate sericite and silica altered porphyritic dike intruded into the mafic volcanic sequence. Mineralization includes up to 20% pyrite stringers, 3% sphalerite and trace chalcopyrite and local visible gold. The interval is approximatively 115 metres above and to the southwest of the Triple 8 discovery in hole OSK-W-18-1603.

OSK-W-18-1616-W2 intersected 13.4 g/t Au over 2.0 metres within an approximate 35 metre pervasive chlorite and biotite altered interval within the andesite. Mineralization consists of up to 3% disseminated pyrite, local pyrite stringers and trace pyrrhotite in fracture filling or with weak silica altered bands. The interval was intersected approximatively 1,800 metres below surface and it is the deepest significant gold bearing interval in the deposit to date.

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 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) 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 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 Garrison property. The Corporation also holds interests and options in a number of additional properties in northern Québec and Ontario.