Osisko Intersects 36 g/t Au Over 6.9 Metres at Lynx

TORONTO, ONTARIO--(Marketwired - Sep 18, 2017) - Osisko Mining Inc. (TSX:OSK) ("Osisko" or the "Corporation") is pleased to provide new results from the ongoing drill program at its 100% owned Windfall Lake gold project located in Urban Township, Abitibi, Québec. The recently expanded 800,000 metre drill program combines definition, expansion and exploration drilling in and around the main Windfall gold deposit and in the adjacent Lynx deposit (located immediately NE of Windfall). Significant new analytical results from 29 intercepts in 21 drill holes focused on infill and expansion drilling in the Lynx deposit are presented below.

Highlights from the new results include: 36.0 g/t Au over 6.9 metres (29.9 g/t Au over 6.9 metres cut) in OSK-W-17-1006; 116 g/t Au over 2.3 metres (31.8 g/t Au over 2.3 metres cut) in OSK-W-17-873; 25.5 g/t Au over 4.0 metres in OSK-W-17-924; (27.1 g/t Au over 3.5 metres (20.5 g/t Au over 3.5 metres cut) OSK-W-17-922; 24.3 g/t Au over 3.5 metres in OSK-W-1010; and 21.3 g/t Au over 3.0 metres in OSK-W-17-1048. Maps showing hole locations and full analytical results are available at www.osiskomining.com.

Notes:

1. True widths are estimated at 65 - 80% of the reported core length interval. See "Quality Control" below.
2. Definitions: HG = Hanging wall; FT = Foot Wall; VNCR = crustiform vein and TBD = To be determined.

OSK-W-17-848 intersected two intervals: 7.95 g/t Au over 2.5 metres (including 19.9 g/t Au over 1.0 metre) and 15.1 g/t Au over 2.1 metres (including 26.2 g/t Au over 1.0 metre). In the first interval, the mineralization is composed of local tourmaline-pyrite stringers, tourmaline stringers and disseminated pyrite within a fragmental intrusion with sericite and silica alteration. The intersection correlates to Lynx 1, 40 metres above OSK-W-17-912 (19.8 g/t Au over 2.0 metres and 6.65 g/t Au over 2.8 metres previously reported August 24, 2017). In the second interval, the mineralization is composed of up 2% disseminated pyrite, 2% pyrite stringers and tourmaline veins. The interval correlates to Lynx HW, 120 metres south-west of OSK-W-17-836 (3.30 g/t Au over 2.3 metres).

OSK-W-17-861 intersected two intervals: 9.41 g/t Au over 2.0 metres (including 18.7 g/t Au over 1.0 metre), related to the Lynx 2, and 4.06 g/t Au over 2.3 metres (including 12.6 g/t Au over 0.4 metres), related to Lynx HW. The mineralization consists of 5% pyrite-tourmaline stringers within a silica altered rhyolite. The first intersection is 40 metres east-north-east of OSK W-17-912 (14.6 g/t Au over 2.2 meters previously reported August 24, 2017) and the second intersection is 40 metres down plunge of OSK-W-17-818.

OSK-W-17-868 intersected 8.22 g/t Au over 2.0 metres (including 18.0 g/t Au over 0.8 metres). The mineralization is composed of up to 10% pyrite stringers, up to 7% disseminated pyrite and local gold hosted in a strongly silicified and sericitized rhyolite.

OSK-W-17-873 intersected two intervals in the Lynx 2 Zone: 9.30 g/t Au over 2.0 metres (including 59.9 g/t Au over 0.3 metres) and 116 g/t Au over 2.3 metres (including 375 g/t Au over 0.7 metres) (31.8 g/t Au over 2.3 metres cut). A third interval with a crustiform quartz vein averaged 10.7 g/t Au over 2.4 metres (including 28.7 g/t Au over 0.8 metres). In Lynx 2, the mineralization is composed of quartz-carbonate veins with up to 5% disseminated pyrite and up to 2% pyrite stringer cross cutting sericitized rhyolite and strongly silica altered gabbro, with local visible gold. The crustiform vein contains up to 3% disseminated pyrite.

OSK-W-17-882 intersected 3.39 g/t Au over 3.0 metres (including 18.8 g/t Au over 0.5 metres) in Lynx 2, contained in a weakly silicified gabbro with small crustiform veins and trace disseminated pyrite.

OSK-W-17-883 intersected 3.89 g/t Au over 2.0 metres in the Lynx 2 Zone. The mineralization consists of up to 2% pyrite stringers and ptygmatic tourmaline veins in a silica altered rhyolite. The interval is 30 metres east of OSK-W-17-873 (116 g/t Au over 2.3 metres, this press release).

OSK-W-17-907 intersected 30.2 g/t Au over 2.0 metres (including 85.2 g/t Au over 0.7 metres). The mineralization is composed of up to 2% pyrite in a sericitized and silicified rhyolite.

OSK-W-17-909 intersected two intervals: 11.8 g/t Au over 2.0 metres (including 37.0 g/t Au over 0.5 metres) and 4.94 g/t Au over 3.1 metres. This interval consists of intense pervasive silica flooding hosted in a gabbro. Mineralization includes up to 7% pyrite stringers. The intersection correlates to Lynx 1, 400 metres down plunge and north-east of OSK-W-17-836. The intersection is 200 metres vertically below OSK-W-17-908 (10.6 g/t Au over 4.2 metres, 7.34 g/t au over 4.1 metres and 12.6 g/t Au over 2.5 metres, previously reported August 9, 2017).

OSK-W-17-914 intersected 27.2 g/t Au over 2.3 metres, (including 105 g/t Au over 0.3 metres) (26.6 g/t Au over 2.3 metres cut). The intersection consists of pervasive silica flooding containing 10% pyrite stringers, 1% disseminated pyrite and local visible gold. Mineralization is hosted in a sericitized rhyolite with fuchsite. It correlates to the Lynx HW Zone, 50 metres south-east and sub parallel to the Lynx 1 Zone, and 75 metres down plunge of OSK-W-17-803 (5.23 g/t Au over 2.3 metres, previously reported April 11, 2017).

OSK-W-17-921 was previously reported on August 9, 2017, with a cut value of 3.05 g/t Au over 2.0 metres. Additional analysis was done on samples greater than 10 g/t Au and the interval was upgraded to 20.6 g/t Au over 2.0 metres (including 97.8 g/t Au over 0.4 metres). Mineralization consist of 5% pyrite stringers and 2% disseminated pyrite at a contact between gabbro and a large quartz-eye felsic dike. The intersection represents the Lynx 1 Zone, 20 metres south-west of OSK-W-17-839 (6.58 g/t Au over 8.3 metres previously reported July 12, 2017).

OSK-W-17-922 intersected 27.1 g/t Au over 3.5 metres, (including 176 g/t Au over 0.3 metres) (20.5 g/t Au over 3.5 metres cut). The intersection is hosted in a strongly silicified and fuschitized gabbro. The mineralization consists of 30% smoky quartz-carbonate-tourmaline-pyrite veins and up to 4% quartz-tourmaline veins. The high-grade sample intervals contain local visible gold, 10% pyrite-tourmaline stringers and 3-4% disseminated pyrite-tourmaline. The intersection is within the Lynx 2 Zone, 30 metres west of OSK-W-17-898 (23.5 g/t Au over 3.0 metres and 12.2 g/t Au over 2.5 metres respectively reported August 9, 2017 and July 25, 2017).

OSK-W-17-924 intersected 25.5 g/t Au over 4.0 metres in Lynx 2, with local visible gold and 1% disseminated pyrite, and pyrite stringers in a silica altered rhyolite. The interval is 25 metres south-west of OSK-W-17-873 (116 g/t Au over 2.3 metres, this press release).

OSK-W-17-928 intersected 9.1 g/t Au over 2.1 metres (including 20.0 g/t Au over 0.9 metres) in Lynx 2. Mineralization comprises 2% pyrite stringers at the contact between gabbro and a felsic porphyritic dike.

OSK-W-17-945 intersected 5.38 g/t Au over 2.0 metres in Lynx 1. The mineralization is composed of up to 1% disseminated pyrite in a chloritized gabbro. The interval is 45 metres north-east of OSK-W-17-898 (17.3 g/t Au over 2.3 metres previously reported July 25, 2017).

OSK-W-17-949 intersected three intervals: 5.18 g/t Au over 4.0 metres (including 28.3 g/t Au over 0.4 metres) in Lynx HW; 4.5 g/t Au over 2.0 metres in Lynx 1; and 10.4 g/t Au over 2.0 metres (including 49.1 g/t Au over 0.4 metres) in Lynx 2. The first interval is at a contact between the rhyolite and the gabbro; the second and the third intervals are in a strongly silicified rhyolite. Small fragmental felsic dikes crosscut the rhyolite. Mineralization is mainly composed of up to 5% pyrite stringers. The Lynx HW and Lynx 1 intersections are 25 metres north-east of OSK-W-17-870 (25.7 g/t Au over 2.7 metres and 18.9 g/t Au over 2.8 metres previously reported July 12, 2017). The Lynx 2 interval is 45 metres north-east of OSK-W-17-873 (10.0 g/t Au over 2.6 metres previously reported July 12, 2017).

OSK-W-17-957 intersected two intervals in Lynx 2 Zone: 6.02 g/t Au over 4.2 metres (including 64.1 g/t Au over 0.3 metres) and 21.5 g/t Au over 2.0 metres (including 70.6 g/t Au over 0.6 metres). Mineralization is composed of up to 3% pyrite fragments, up to 15% disseminated pyrite and local visible gold hosted in a strongly sericitized fragmental felsic intrusion. These intervals are 10 metres west of OSK-W-17-895 (8.98 g/t Au over 6.5 metres previously reported August 9, 2017).

OSK-W-17-958 intersected 9.18 g/t Au over 2.2 metres. Mineralization is composed of up to 3% disseminated pyrite and pyrite stringers in a strongly sericitized fragmental felsic intrusion. The intersection is 70 metres down plunge to the north-east of OSK-W-17-898 (12.2 g/t Au over 2.5 metres previously reported July 25, 2017).

OSK-W-17-974 intersected 24.2 g/t Au over 2.0 metres (including 94.2 g/t Au over 0.5 metres) in Lynx 2. The mineralization is composed of up to 20% disseminated pyrite and a quartz-tourmaline vein. The fragmental felsic dike host is strongly sericitized and silicified. The interval is 30 metres south-west of OSK-W-17-957 (6.02 g/t Au over 4.2 metres reported in this press release).

OSK-W-17-1006 intersected 36.0 g/t Au over 6.9 metres (including 147 g/t Au over 0.9 metres; 62.3 g/t Au over 1.1 metres; and 41.4 g/t Au over 0.9 metres) (29.9 g/t Au over 6.9 metres cut). Mineralization consists of two centimeter-scale smoky quartz veins at low core angles with 10% pyrite and local visible gold within a sericite and silica altered fragmental felsic unit. The intersection is related to the Lynx 2 Zone, 50 metres east of OSK-W-17-812 (26.0 g/t Au over 2.5 metres previously reported May 3, 2017).

OSK-W-17-1010 intersected 24.3 g/t Au over 3.5 metres (including 62.9 g/t Au over 1.0 metre). Mineralization is in a crustiform vein (quartz, carbonate and tourmaline) with local visible gold, 5% pyrite stringers and pyrite clusters hosted in a fragmental felsic volcanic. The vein is 20 metres north-east of OSK-W-17-877 (57.8 g/t Au over 2.3 metres previously reported July 25, 2017).

OSK-W-17-1048 intersected 21.3 g/t Au over 3.0 metres (including 37.4 g/t Au over 1.2 metres) in the Lynx 2 Zone. The mineralization is composed of up to 5% pyrite stringers and 2% quartz-tourmaline veins hosted in a strongly sericitized and silicified rhyolite. The intersection is 30 metres below OSK-W-17-849 (7.10 g/t Au over 2.0 metres previously reported July 12, 2017).

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 ("NI 43-101").

Quality Control and Reporting Protocols

True widths determinations are estimated at 65-80% of the reported core length intervals for most of the zones. 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 ALS Laboratories in Val d'Or, Québec, Thunder Bay and Sudbury, Ontario or Vancouver, British Colombia or 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 the previous operator comprises 2,762,000 tonnes at 8.42 g/t Au (748.000 ounces) in the indicated category and 3,512,000 tonnes at 7.62 g/t Au (860,000 ounces) in the inferred category (sourced from a technical report dated June 10, 2015 entitled "Preliminary Economic Assessment of the Windfall Lake Gold Property, Québec, Canada" with an effective date of April 28, 2015, prepared in accordance with NI 43-101). The Windfall Lake gold deposit is currently one of the highest grade resource-stage gold projects in Canada. The bulk of the mineralization occurs in the Main Zone, a southwest/northeast trending zone of stacked mineralized lenses, measuring approximately 600 metres wide and at least 1.400 metres long. The deposit is well defined from surface to a depth of 500 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 870 metres in others, with significant potential to extend mineralization up and 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 Quebec and Ontario. Osisko continues to be well financed with approximately $190 million in cash and investments.

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 current 800,000 metre drill program; the significance of new results from the ongoing drill program at the Windfall Lake gold project; the significance of assay results presented in this press release; the type of drilling included in the drill program (definition drilling, expansion drilling to the NE of the main deposit and adjacent Lynx deposit, and exploration drilling on the greater deposit and Urban-Barry project area); 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 it was made, 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.

Contact

John Burzynski
President and Chief Executive Officer
(416) 363-8653