Work on Osisko’s Garrison Project leads to positive decision on drilling

Encouraging diamond drill results has Osisko Mining Inc. going ahead with an investigation of extensions of the mineralized zones within the Garrison Gold Project in Northeastern Ontario. The ongoing drill program at its 100% owned Garrison located in Garrison Township. At 35,000 metre drill program was designed to further test the known Garrcon, Jonpol and 903 Zones, with six drill rigs.

A total of four new holes were reported in February.

Significant new results included: 16.7 g/t Au over 16.4 metres (8.52 g/t Au over 16.4 metres cut) and 7.62 g/t Au over 2.6 metres in OSK-G17-326.

The company said the “new results demonstrate the potential to expand the extent of known mineralization in the 903 Zone. The ongoing 2017 drill program will continue to investigate extensions of the mineralized zones within the Garrcon, Jonpol and 903 Zones.

OSK-G16-312 targeted deep mineralization within the Jonpol Zone by drilling through the Garrcon mineralized horizon.

It successfully identified a new zone of mineralization within the western portion of the Garrcon Zone. The new mineralization is hosted within metasedimentary rocks along the south contact of an iron formation and averaged 3.63 g/t Au over 5.2 metres. 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 (82,400 hectares), 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 Garrcon and Jonpol zones on the Garrison property, the Buffontapast producing mine and the Gold

Pike mine property.

The Corporation also holds interests and options in a number of additional properties in Northern Ontario.

Osisko continues to be well financed and has approximately $90 million in cash and cash equivalents as well as equity investments of approximately $50 million.

In Timmins, Osisko owns the former Desantis Mine in Ogden Township. The mine operated from 1939 to 1942, producing 179,000 tonnes at a grade of 6.51 g/t gold.

The company also owns the Cote Project located 15km south of Kirkland Lake that comprises over 4,000 Ha in prospective ground.

The focus will be to explore for alkaline intrusives aligned along the Catherine fault and to look for Archean high grade vein hosted gold along the Pacaud and Catharine structures. The 100 per cent owned Windfall Lake Property is Osisko’s key asset in Quebec:

* 12,400 ha comprising 285 mineral claims in the Abitibi mineralized belt;

* Located within the region covered by Québec’s Plan Nord;

* A Preliminary Economic Assessment study was recently completed with the following parameters (1):

– 1,200 tpd underground mine producing 106koz/year average gold production through an existing ramp;

– 7.8 year mine life;

– 8.26 g/t head grade;

– Preliminary metallurgical tests of 95.7% gold; recovery using flotation and leaching;

– LOM total gold production of 828 koz Au;

– C$558/oz total life-of-mine average cash costs;

* Average mining cost of $76/t;

– C$240.6MM development capital;

– C$241.4 MM NPV (5%) on a pretax basis;

– C$135.2MM NPV (5%) on a posttax basis;

– 3.4 years pay back on a pre-tax basis.

* Engineering studies commencing.

Osisko has an ongoing drill program at its Windfall Lake gold project located in Urban Township.

The current 400,000 metre drill program combines definition drilling above the Red Dog intrusion, expansion drilling above and below Red Dog, expansion drilling to the NE of the main deposit, and exploration drilling on the greater deposit and Urban- Barry Project area.

New analytical results from one drill hole focused on expansion and infill drilling in the Lynx Corridor.

Significant new results include: 64.3 g/t Au over 2.3 metres and 19.4 g/t Au over 2.0 metres in OSK-W-16-761.