Osisko Intersects 27 g/t Au Over 2.7 Metres at Lynx

TORONTO, ONTARIO--(Marketwired - Oct 3, 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 800,000 metre drill program combines definition, expansion and exploration drilling in and around the main Windfall gold deposit and the adjacent Lynx deposit (located immediately NE of Windfall). Significant new analytical results from 23 intercepts in 17 drill holes focused on infill and expansion drilling in the Lynx deposit are presented below.

Highlights from the new results include: 27.0 g/t Au over 2.7 metres in OSK-W-17-906; 11.6 g/t Au over 4.4 metres in OSK-W-17-1039; 13.0 g/t Au over 3.6 metres in OSK-W-17-1102; 23.4 g/t Au over 2.0 metres in OSK-W-17-918; and 22.0 g/t Au over 2.0 metres in OSK-W-17-958. 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; FW = Foot Wall; VNCR = crustiform vein; TBD = to be determined.

OSK-W-17-899 intersected Lynx 2 returning 4.46 g/t Au over 2.0 metres. Mineralization includes up to 6% pyrite as disseminations and clusters and pyrite stringers hosted within weak to moderate chloritized rhyolite, and 1-3% pyrite within weakly developed crustiform veins occurring near the contact between the rhyolite and gabbro. This interval expands the Lynx 2 corridor 35 metres north-east of OSK-W-17-805 (12.4 g/t Au over 5.0 metres previously reported June 16, 2017).

OSK-W-17-906 intersected three intervals: 27.0 g/t Au over 2.7 metres, 4.25 g/t Au over 2.5 metres, both related to Lynx HW and finally 5.05 g/t Au over 4.0 metres related to Lynx 2 FW. Mineralization is hosted in a felsic volcanic cut by quartz veins (pervasive silica flooding) with 30% disseminated pyrite and local visible gold. The second interval is in a porphyritic felsic intrusion cut by small quartz veins with 5-7% disseminated pyrite. Mineralization for the third interval consists of up to 2% disseminated pyrite hosted in a weak sericitized and strong silicified felsic volcanic. This intersection extends Lynx 2 corridor 35 metres north-east of OSK-W-17-803 (5.23 g/t Au over 2.3 metres previously reported April 11, 2017).

OSK-W-17-909 intersected 4.33 g/t Au over 3.7 metres related to crustiform veins containing 3% disseminated pyrite. The crustiform veins do not correlate to a known zone within the Lynx corridor.

OSK-W-17-918 intersected 23.4 g/t Au over 2.0 metres in Lynx 2. The interval includes 10-15% pervasive silica flooding, 3-5% pyrite tourmaline stringers within a sericitized fragmental felsic intrusion. It is located 10 metres below OSK-W-17-825 (4.06 g/t Au over 2.0 metres previously reported May 10, 2017).

OSK-W-17-929 intersected 18.9 g/t Au over 2.0 metres in Lynx 1, containing locally 8% disseminated pyrite within a moderately to strongly silicified gabbro. It is 210 metres down plunge and north-east of OSK-W-17-909 (11.8 g/t Au over 2.0 metres previously reported September 18, 2017).

OSK-W-17-939 intersected two intervals: 12.1 g/t Au over 2.0 metres in Lynx 1 and 4.71 g/t over 2.0 metres in Lynx 2. The first interval includes trace pyrite and 5% pyrite tourmaline stringers within a weakly sericitized felsic intrusion. The second interval is similar but hosted at the contact between a felsic dike and a volcanic. This interval is 35 metres up plunge and north-east of OSK-W-17-788 (17.0 g/t Au over 17.3 metres, previously reported April 5, 2017).

OSK-W-17-958 intersected three intervals: 22.0 g/t Au over 2.0 metres in Lynx 1, 5.74 g/t Au over 5 metres in Lynx 4 and 5.36 g/t Au over 2.0 metres. The first interval, weakly bleached by sericite and moderate patchy silica alteration, contains 5-7% pyrite stringers, traces of chalcopyrite and quartz-tourmaline veining. It correlates 25 metres east to OSK-W-17-887 (24.3 g/t Au over 2.6 metres previously reported July 25, 2017). The second interval is strongly altered by fuchsite and locally strongly altered by pervasive silica flooding with up to 10-15% disseminated pyrite and traces of chalcopyrite. This interval contains 20% crustiform veins. The second interval corresponds to a new extension of the Lynx 4 HW and correlates 170 metres north-east of OSK-W-17-817 (13.3 g/t Au over 2 metres previously reported July 12, 2017). The third interval contains trace pyrite in a quartz vein hosted by a weak silicified and sericitized and strong chloritized gabbro. This interval is within the Lynx corridor, zone to be determined.

OSK-W-17-986 intersected 5.69 g/t Au over 3.1 metres related to a crustiform vein in the Lynx Corridor. Mineralization consists of crustiform quartz-carbonate veins (20-60 centimetres) with pervasive silica flooding hosted in a bleached gabbro with 15% disseminated pyrite, tourmaline-pyrite stringers and local visible gold. The crustiform veins are located 30 metres below and northeast of another crustiform vein previously reported in OSK-W-17-859 (73.5 g/t Au over 2.2 metres, July 12, 2017).

OSK-W-17-987 intersected 5.77 g/t Au over 2.0 metres. Mineralization contains 2% pyrite stringers associated with quartz carbonate and tourmaline veins hosted in a fuschitized and chloritized gabbro, and correlates to a crustiform vein in the Lynx 2 corridor above another crustiform vein in OSK-W-16-740 (5.69 g/t Au over 4.6 metres previously reported January 11, 2017).

OSK-W-17-1021 intersected 9.72 g/t Au over 2.2 metres. Mineralization consists of two crustiform veins with 1% pyrite silicified bands surrounded by felsic intrusion with 2% disseminated pyrite.

OSK-W-17-1039 intersected 11.6 g/t Au over 4.4 metres. The interval is a strongly silicified fragmental felsic intrusion which contains 5% disseminated pyrite and 5% pyrite in a quartz-tourmaline vein (over 10 centimetres). It is located 30 metres north-east of OSK-W-17-912 (6.65 g/t Au over 2.8 metres previously reported August 24, 2017).

OSK-W-17-1044 intersected 3.03 g/t Au over 2.1 metres in Lynx 1. Mineralization is hosted in a bleached, chloritized and epidotized mafic volcanic containing 2% pyrite clusters and 3% pyrite stringers. The hole is 50 metres north-east of OSK-W-17-790 (11.3 g/t Au over 3.6 metres previously reported March 28, 2017).

OSK-W-17-1068 intersected 4.77 g/t Au over 2.4 metres in the Lynx HW Zone. This interval contains pervasive silica flooding with 20% pyrite clusters and 10% pyrite stringers. Both lower and upper contacts are ptygmatic tourmaline veins, hosted in a sericitized large quartz eye felsic intrusion. The interval is 80 metres south-west of OSK-W-17-848 (15.1 g/t Au overs 2.1 metres previously released September 18).

OSK-W-17-1091 intersected 11.3 g/t Au over 2.3 metres in Lynx 1. The interval is within a strongly sericitized felsic volcanic with trace pyrite clusters and traces of pyrite stringers, located 5 metres up plunge and west of OSK-W-16-755 (11.8 g/t Au over 6.0 metres previously reported January 11, 2017).

OSK-W-17-1102 intersected 13.0 g/t Au over 3.6 metres in Lynx 2. This interval consists of a quartz-tourmaline vein (5 centimetres) with 7% pyrite and a pervasive silica flooding with 15% pyrite and 1% pyrite stringer in a sericitized and silicified rhyolite. The interval is 15 metres down plunge and north-east of OSK-W-17-899 (4.46 g/t Au over 2.0 metres, this press release).

OSK-W-17-1121 intersected two intervals: 4.29 g/t Au over 2.0 metres and 7.78 g/t Au over 4.0 metres, both in Lynx 1. The mineralization is hosted at a rhyolite and felsic intrusion contact and composed of 2-3% of pervasive silica flooding with up to 3% pyrite stringers and disseminated pyrite. The intersection is 15 metres south-west of OSK-W-17-792 (42.1g/t Au over 9.2 metres, previously reported April 5, 2017).

OSK-W-17-1169 intersected 4.23 g/t Au over 3.5 metres in Lynx 2. Mineralization consists of 10% disseminated pyrite in silica altered gabbro. It is 120 metres down plunge and east OSK-W-17-958 (9.18 g/t Au overs 2.2 metres previously reported September 18, 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 $246 million in cash and investments (pro-forma recently announced financing).

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