Osisko Intersects 49.1 g/t Au Over 6.6 Metres at Lynx

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TORONTO, Oct. 02, 2018 - Osisko Mining Inc. (OSK:TSX. "Osisko" or the "Corporation") 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 currently focussed on infill drilling within the main Windfall gold deposit and the adjacent Lynx deposit (located immediately NE of Windfall), exploration and expansion drilling on the main mineralized zones, and deep hole exploration in the central areas of the intrusive system.

Significant new analytical results from 63 intercepts in 39 drill holes and one wedge focused on infill drilling are presented below.

Highlights from the new results include: 49.1 g/t Au over 6.6 metres in OSK-W-18-1551; 79.9 g/t Au over 2.0 metres in OSK-W-18-1672; 57.6 g/t Au over 2.7 metres in OSK-W-18-1698; 45.5 g/t Au over 3.3 metres in OSK-W-18-1638 and 57.7 g/t Au over 2.1 metres in OSK-W-18-1536-W1. Maps showing hole locations and full analytical results are available at www.osiskomining.com.

Note: True widths are estimated at 65 – 80% of the reported core length interval. See "Quality Control and Reporting Protocols" below.

OSK-W-17-852 intersected 10.0 g/t Au over 2.0 metres in Caribou. Mineralization consists of local visible gold, traces pyrite and quartz-carbonate veins hosted in a sericite altered andesite in contact with a felsic porphyritic dike.

OSK-W-18-1454 intersected 45.5 g/t Au over 3.3 metres in Lynx. Mineralization consists of up to 8% pyrite-silica flooding, quartz-tourmaline veins and local visible gold within a sericite, fuchsite and silica altered rhyolite.

OSK-W-18-1522 intersected 11.5 g/t Au over 4.6 metres in Lynx. Mineralization consists of 2% pyrite stringers, trace pyrite clusters and local visible gold within weak pervasive silica flooding hosted in a sericite, silica and fuchsite altered rhyolite.

OSK-W-18-1536-W1 intersected 57.7 g/t Au over 2.1 metres in Lynx. Mineralization consists of 3% pyrite at the contact of quartz-carbonate vein hosted in a chloritized gabbro.

OSK-W-18-1543 intersected 3.41 g/t Au over 2.1 metres in Zone 27. Mineralization consists of local visible gold in a quartz-carbonate vein cross-cutting a large pyrite stringer, 5-7% pyrite stringers hosted in a strongly bleached andesite.

OSK-W-18-1551 intersected 49.1 g/t Au over 6.6 metres in Lynx. Mineralization consists of up to 5% pyrite stringers, 5% disseminated pyrite, pyrite-silica flooding and local visible gold at the contact between a strong silica and moderate fuchsite altered rhyolite and a fragmental felsic dike.

OSK-W-18-1587 intersected 21.3 g/t Au over 2.0 metres in Lynx. Mineralization consists of 10% pyrite-silica flooding, 3% pyrite clusters and quartz-tourmaline veins within strong sericite altered gabbro.

OSK-W-18-1627 intersected 15.2 g/t Au over 2.4 metres in Lynx. Mineralization consists of 1% pyrite stringers, trace disseminated pyrite and quartz-carbonate veins hosted in strong carbonate, weak chlorite altered gabbro.

OSK-W-18-1630 intersected 3.59 g/t Au over 2.1 metres in Caribou. Mineralization consists of 10% semi massive pyrite over 50 centimetres, 3% pyrite stringers, 1% disseminated pyrite hosted in a sericite and silica altered rhyolite.

OSK-W-18-1632 intersected 5.51 g/t Au over 2.8 metres in Caribou. Mineralization consists of 10% pyrite stringer within silica patches and 5% pyrite clusters hosted in a sericite altered felsic porphyritic intrusion.

OSK-W-18-1655 intersected 21.5 g/t Au over 2.0 metres in Caribou. Mineralization consists of 10% disseminated pyrite hosted in a moderate sericite and carbonate altered felsic porphyritic dike.

OSK-W-18-1661 intersected 6.23 g/t Au over 2.2 metres in Caribou. Mineralization consists of up to 20% pyrite stringers, 10% ptygmatic tourmaline veins, and trace sphalerite within a moderate sericite, chlorite and carbonate altered felsic dike.

OSK-W-18-1662 intersected 3.55 g/t Au over 2.0 metres in Zone 27. Mineralization consists of 10% pyrite-tourmaline stringers within a sericite and silica altered rhyolite.

OSK-W-18-1665 intersected 3.60 g/t Au over 2.6 metres in Caribou. Mineralization consists of up to 15% pyrite stringers, 1% pyrite-silica flooding, trace sphalerite and crustiform quartz veins hosted in moderate sericite and chlorite altered rhyolite.

OSK-W-18-1667 intersected 21.7 g/t Au over 2.2 metres in Lynx. Mineralization consists of local visible gold, up to 5% disseminated pyrite stringer with pervasive silica flooding and a crustiform vein hosted in a strong silica and moderate fuchsite altered gabbro.

OSK-W-18-1669 intersected 4.15 g/t Au over 2.1 metres in Caribou. Mineralization consists of 3% pyrite stringers and trace sphalerite within a moderate sericite and silica altered porphyritic felsic dike.

OSK-W-18-1672 intersected 4.31 g/t Au over 2.2 metres in Caribou and 79.9 g/t Au over 2.0 metres in Zone 27. The first interval is composed of trace disseminated pyrite clusters, a 60 centimetre quartz vein hosted in a sericitized porphyritic felsic dike. The second interval is composed of local visible gold with massive pyrite, intense silica flooding, 3% pyrite clusters and 3% pyrite in quartz-tourmaline veins. Mineralization is hosted in a bleached, silicified and strongly sericitized fragmental intrusion.

OSK-W-18-1673 intersected 20.4 g/t Au over 2.0 metres, 7.23 g/t Au over 3.0 metres, 7.34 g/t Au over 2.5 metres and 25.2 g/t Au over 2.4 metres in Lynx. The first interval contains 10% pyrite stringers and 5% pyrite clusters hosted in a strong sericite altered rhyolite. The second interval is composed of 2% pyrite stringers with local pervasive silica flooding at the contact between a gabbro and a rhyolite. The third interval is composed of 4% disseminated pyrite with pervasive silica flooding within a sericite and silica altered rhyolite. The last interval contains 3% disseminated pyrite in pervasive silica flooding, 2% pyrite clusters, 1% pyrite stringers and trace pyrite in a crustiform quartz vein. Mineralization is hosted in a strong silica and weak fuchsite altered gabbro.

OSK-W-18-1674 intersected 3.53 g/t Au over 2.6 metres in Zone 27. Mineralization consists of up to 25% pyrite with tourmaline stringers hosted in a strongly sericitized and bleached andesite.

OSK-W-18-1675 intersected 3.63 g/t Au over 2.0 metres in Lynx. The interval contains up to 10% disseminated pyrite, stringers and clusters with pervasive silica flooding in a strong silica and moderate sericite altered fragmental felsic intrusion.

OSK-W-18-1680 intersected five intervals: 10.9 g/t Au over 3.0 metres, 5.13 g/t Au over 2.8 metres and 3.84 g/t Au over 2.0 metres in Caribou; 14.4 g/t Au over 2.0 metres and 3.21 g/t Au over 7.5 metres in Zone 27. The first interval is composed of 5% pyrite in fracture filling, 1% pyrite and trace sphalerite with quartz-carbonate veins and traces disseminated pyrite hosted in a faulted, moderate fuchsite and patchy silica altered rhyolite. The second interval contains 25% pyrite in a semi-massive band, 2% pyrite with pervasive silica flooding in a silicified rhyolite. The third interval is composed of 1% pyrite-tourmaline stringers, trace pyrite with quartz clusters hosted in a sericite altered porphyritic felsic dike. The fourth interval is composed of 2% disseminated pyrite and tourmaline within a moderate to strong sericite altered rhyolite. The last interval contains 8% pyrite disseminated and clusters, 3% pyrite stringers and trace chalcopyrite within quartz-carbonate veins hosted in strong sericite altered rhyolite and felsic porphyritic dike.

OSK-W-18-1681 intersected 11.9 g/t Au over 2.0 metres and 8.06 g/t Au over 2.5 metres in Lynx. The first interval contains up to 5% disseminated pyrite in quartz-tourmaline veins and ptygmatic tourmaline veinlets hosted in a silicified gabbro. The second interval contains up to 3% pyrite-silica flooding within strong silica and moderate fuchsite altered gabbro.

OSK-W-18-1684 intersected 3.73 g/t Au over 2.1 metres in Lynx. Mineralization consists of 5% disseminated pyrite with 10% quartz clusters hosted in a moderate chlorite and carbonate altered gabbro.

OSK-W-18-1685 intersected three intervals in Zone 27: 7.01 g/t Au over 4.1 metres, 7.56 g/t Au over 3.1 metres and 32.3 g/t Au over 2.5 metres. The first interval consists of 7% disseminated pyrite and trace pyrite stringer in a strongly bleached and sericitized andesite. The second interval is composed of 7% disseminated pyrite and trace pyrite stringers hosted in a moderate sericite altered felsic porphyritic intrusion. The last interval contains 10% pyrite clusters, 1% pyrite stingers and trace pyrite-tourmaline stringers hosted in a moderate chlorite and sericite altered andesite.

OSK-W-18-1686 intersected 9.95 g/t Au over 2.4 metres in Zone 27. Mineralization consists of 50% semi-massive pyrite and 5% disseminated sphalerite with fragmental quartz-carbonate veinlets hosted in a sericitized and silicified fragmental felsic dike and rhyolite.

OSK-W-18-1687 intersected 3.49 g/t Au over 3.2 metres in Lynx. Mineralization consists of up to 5% pyrite hosted in two crustiform veins of 10 and 20 centimetres wide within a moderate sericite and moderate fuchsite altered gabbro.

OSK-W-18-1689 intersected 6.78 g/t Au over 3.3 metres and 3.62 g/t Au over 2.0 metres in Zone 27. Both intervals contain up to 30% pyrite and pyrite-tourmaline stringers hosted in silica and sericite altered felsic porphyritic intrusion in contact with a rhyolite.

OSK-W-18-1690 intersected 6.51 g/t Au over 2.5 metres in Zone 27. Mineralization consists of up to 15% pyrite stringers with disseminated tourmaline hosted in silicified rhyolite.

OSK-W-18-1691 intersected 3.30 g/t Au over 2.1 metres in Caribou. Mineralization is composed of 1% pyrite stringers and traces disseminated pyrite in a bleached and sericitized andesite.

OSK-W-18-1692 intersected 18.5 g/t Au over 2.0 metres and 4.30 g/t Au 2.5 metres in Caribou. The first interval contains 7% pyrite and trace sphalerite infilling fractures within a fault zone hosted in a felsic porphyritic intrusion. The second interval contains up to 5% pyrite stringers, 1% pyrite associated with pervasive silica flooding, 1% pyrite in fractures filling within faulted, moderate sericite altered rhyolite.

OSK-W-18-1695 intersected three intervals: 3.01 g/t Au over 2.6 metres, 5.39 g/t Au over 2.3 metres in Caribou and 4.57 g/t Au over 2.1 metres in Zone 27. The first interval contains 5% pyrite stringers and 30% massive pyrite in a decimetre-scale band hosted in a silica and sericite altered rhyolite in contact with a bleached andesite. The second interval is composed of 10% pyrite stringers hosted in moderate bleach, weak chlorite and silica altered andesite. The last interval contains 10% pyrite with pervasive silica flooding, pyrite stockwork with disseminated tourmaline and 15% massive pyrite over 25 centimetres hosted in strongly silicified and bleached andesite.

OSK-W-18-1696 intersected 3.48 g/t Au over 4.4 metres and 4.77 g/t Au over 2.1 metres in Lynx. The first interval contains up to 7% pyrite with quartz carbonate veins, up to 5% pyrite stringers, 3% disseminated pyrite and 3% pyrite fragments hosted in a bleached, sericitized and fuchsite altered gabbro. The second interval contains up to 15% fine-grained pyrite stringers, trace pyrite-tourmaline stringers, 2% pyrite clusters with local quartz-carbonate veinlets hosted in a moderate chlorite, sericite and fuchsite altered gabbro.

OSK-W-18-1697 intersected 4.24 g/t Au over 2.2 metres in Lynx. Mineralization consists of up to 5% disseminated pyrite in strong pervasive silica alteration and within 20 centimetre wide crustiform vein hosted in a porphyritic felsic dike.

OSK-W-18-1698 intersected two intervals in Caribou: 5.75 g/t Au over 2.0 metres and 57.6 g/t Au over 2.7 metres. The first interval contains up to 5% pyrite stringers with pervasive silica flooding and 1% disseminated pyrite within strong silica and sericite altered rhyolite in contact with a felsic dike. The second interval contains up to 5% interstitial pyrite with pervasive silica flooding hosted in a moderate sericite altered porphyritic felsic dike.

OSK-W-18-1699 intersected four intervals: 5.05 g/t Au over 2.0 metres and 7.26 g/t Au over 3.5 metres in Lynx; 7.25 g/t Au over 5.6 metres and 18.4 g/t au over 2.0 metres in Bobcat. The first interval is composed of up to 5% disseminated pyrite and clusters with moderate pervasive silica alteration in 2 metre wide crustiform vein at the contact with a felsic dike. The second interval contains up to 10% pyrite-silica flooding, and quartz crustiform veins within a strong silica altered felsic dike. The third interval contains up to 10% disseminated pyrite in a strong silica alteration overprinted by quartz crustiform vein in a gabbro. The last interval contains trace disseminated pyrite and quartz-carbonate vein in a strongly chloritized gabbro.

OSK-W-18-1701 intersected 29.0 g/t Au over 2.0 metres in Bobcat. Mineralization consists of up to 5% pyrite-silica flooding within a strong silica altered felsic porphyritic intrusion.

OSK-W-18-1702 intersected four intervals: 30.3 g/t Au over 2.0 metres, 3.21 g/t Au over 2.3 metres and 7.51 g/t Au over 2.0 metres in Caribou; and 5.58 g/t au over 4.8 metres in Zone 27. The first interval is composed of traces pyrite stringer and pyrite-tourmaline stringer in a moderate sericite altered rhyolite. The second interval contains 8% disseminated pyrite within a moderate chlorite altered rhyolite. The third interval contains 1% disseminated pyrite within weak sericite altered andesite. The last interval contains up to 10% pyrite stringers, 2% ptygmatic tourmaline veins and local visible gold hosted at the contact between a moderate bleach, sericite and silica altered andesite and a felsic dike.

OSK-W-18-1704 intersected 14.2 g/t Au over 2.0 metres in Lynx. Mineralization consists of up to 10% disseminated pyrite and 2% pyrite stringers within moderate chlorite, weak silica and sericite altered gabbro.

OSK-W-18-1707 intersected 3.02 g/t Au over 2.4 metres in Caribou. Mineralization consists of up to 10% pyrite with quartz veins hosted in a moderate chlorite altered gabbro.

OSK-W-18-1709 intersected 17.4 g/t Au over 2.0 metres in Zone 27. Mineralization consists of 10% pyrite clusters and 3% pyrite stringers within a moderate sericite and weak silica altered felsic porphyritic intrusion.

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 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 ("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), 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 30 metres from surface in some areas and as deep as 2000 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% 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.

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 Windfall Lake gold deposit being a world-class gold system; the significance of new results from the ongoing deep-hole drill/exploration program at the Windfall Lake gold project; the significance of assay results presented in this news release; potential depth extensions of the Lynx and Underdog mineralized zones; the potential, if any of the Deep Underdog and Deep Lynx zones; the type and extend of drilling on the Deep Underdog and Deep Lynx zones, including planned wedge holes; the success of Osisko's deep-hole drill/exploration program at the Windfall Lake gold project, if any; the down-plunge projection of the gold mineralized structures; the current 800,000 metre 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