Osisko Discovers Two New Gold-Copper Zones at Upper Beaver

MONTREAL, QUEBEC--(Marketwire - March 21, 2013) - Osisko Mining Corporation (TSX:OSK)(FRANKFURT:EWX) ("Osisko") is pleased to announce that new drilling at the Upper Beaver gold project located in Kirkland Lake, Ontario has led to the discovery of two new gold-copper zones.

The following intersections highlight high-grade results from the two new discoveries:

• East Basalt Zone Discovery: 9.3 g/t Au with 1.7% Cu over 18.1 metres (hole UB13-284) and 2.2 g/t Au with 0.5% Cu over 17.8 metres (hole UB13-287);

• North Q Zone Discovery: 11.0 g/t Au with 1.6% Cu over 2.0 metres (hole UB13-282);

Additional new results from infill drilling on previously known mineralized zones include the following highlights: 3.2 g/t Au with 0.8% Cu over 30.0 metres (UB13-278), 16.1 g/t Au with 8.8% Cu over 3.0 metres and 11.4 g/t Au with 3.3% Cu over 3.0 metres (hole UB13-280) from the North Basalt Zone and 5.4 g/t Au with 0.5% Cu over 59.0 metres (hole UB13-262W4) from the Porphyry West Zone.

The table below outlines the results of 10 new holes completed in 2013 as part of the ongoing exploration and in-fill resource definition drill program at Upper Beaver:

Hole #	From (m)	To (m)		Interval (m)	Cu (%)		Au (g/t)	Zone
New zones
UB13-279	92.0	93.0		1.0	0.22		0.81	East Basalt
UB13-281	120.0	123.0		3.0	0.18		3.16	East Basalt
UB13-284	147.0	165.1		18.1	1.70		9.30	East Basalt
including	154.0	165.1		11.1	2.75		13.05	East Basalt
UB13-287	170.0	187.8		17.8	0.50		2.20	East Basalt
UB13-282	174.0	177.0		3.0	0.89		2.34	North Q
and	185.0	192.0		7.0	trace		1.28	North Q
and	264.0	272.0		8.0	0.56		3.20	North Q
including	269.0	271.0		2.0	1.57		11.00	North Q
and	311.0	322.0		11.0	0.59		0.91	North Q
UB13-288	177.0	182.0		5.0	0.12		1.46	North Q
and	196.0	199.0		3.0	1.53		2.56	North Q
and	277.0	291.0		14.0	0.30		1.84	North Q
including	280.0	284.0		4.0	0.75		4.40	North Q
Infill holes
UB13-262W4	812.0	871.0		59.0	0.53		5.43	Infill - Porphyry West
including	829.0	844.0		15.0	1.03		14.60	Infill - Porphyry West
UB13-276	333.0	334.0		1.0	1.32		4.83	North Basalt
and	423.0	427.0		4.0	trace		1.48	North Basalt
UB13-278	360.0	390.0		30.0	0.80		3.20	North Basalt
including	364.0	368.0		4.0	1.70		9.70	North Basalt
and	370.0	380.0		10.0	0.90		2.80	North Basalt
and	385.0	390.0		5.0	1.00		3.80	North Basalt
UB13-280	447.0	450.0		3.0	8.81		16.10	North Basalt
and	479.0	482.0		3.0	3.23		11.40	North Basalt

New Discoveries: East Basalt Zone and the North Q Zone

Step-out exploration drilling in the first quarter of 2013 has intersected two new gold-copper discoveries: the East Basalt Zone and the North Q Zone, both occurring in mafic volcanic rocks adjacent to the Upper Beaver Igneous Complex.

Four holes (UB13-279, -281, -284 and -287) drilled approximately 700 metres north-east of the Upper Beaver deposit have intersected new copper-gold mineralization in the East Basalt Zone. All four holes drilled on the same section intersected the mineralization starting at 75 m below surface. The most significant result was intersected in hole UB13-284 where a 18.1 metre thick continuous zone of gold and copper mineralization assayed 9.3 g/t Au with 1.7% Cu, included is an interval assaying 13.1 g/t Au with 2.8% Cu over 11.1 metres. Hole UB13-287 drilled below UB13-284 intersected 2.2 g/t Au with 0.5% Cu over 17.8 metres. The chalcopyrite-magnetite stringer mineralization at the East Basalt Zone dips steeply to the north and resembles the mineralization previously mined near the south-west margin of the igneous complex.

Two holes (UB13-282 and -288) drilled approximately 400 metres north-west of the Upper Beaver deposit intersected the new North Q Zone. The holes intersected multiple stringers of gold and copper mineralization approximately 200 metres below surface with significant intervals assaying 3.2 g/t Au with 0.6% Cu over 8.0 metres including 11.0 g/t Au with 1.6% Cu over 2.0 metres (hole UB13-182) and 1.84 g/t Au with 0.3% Cu over 14.0 metres including 4.4 g/t Au with 0.75% Cu over 4.0 metres (UB13-288).

North Basalt Zone

The North Basalt Zone is located approximately 800 metres north of the Upper Beaver deposit and was initially discovered by Queenston in 2005 in drill hole UB05-13 assaying 0.5 g/t Au over 8.0 metres. In 2006 drilling continued to target the zone including hole UB06-51 intersecting two intervals assaying 6.2 g/t Au with 1.3% Cu over 9.9 metres and 8.0 g/t Au with 1.0% Cu over 9.1 metres. Later in 2006 drilling at the North Basalt Zone was postponed as emphasis was focussed to the south to extend the primary Upper Beaver deposit.

Three new holes targeted the North Basalt Zone located west of the north-south trending diabase dyke. Hole UB13-278 intersected a 30.0 metre wide zone of mineralization assaying 3.2 g/t Au with 0.8% Cu including 9.7 g/t Au with 1.7% Cu over 4.0 metres at approximately 300 m below surface. Fifty metres below this interval hole UB13-280 intersected high grade mineralization assaying 16.1 g/t Au with 8.8% Cu over 3.0 metres and 11.4 g/t Au with 3.3% Cu over 3.0 metres.

In-fill Resource Definition

Drilling continues to confirm the continuity of the mineralization in the western portion of the main Upper Beaver deposit. At approximately 700 metres below surface hole UB13-262W4 intersected a thick zone of mineralization assaying 5.4 g/t Au with 0.5% Cu over 59.0 metres including 8.0 g/t Au with 0.7% Cu over 32.0 m. This interval is approximately 30 m above previous hole UB12-262W3 that cut a similar wide interval assaying 5.5 g/t Au with 0.6% Cu over 54.0 metres. (See News Release dated January 30, 2013).

About Upper Beaver

The Upper Beaver project is 100% owned by Osisko Mining Ltd., a wholly-owned subsidiary of Osisko. The Upper Beaver mine produced approximately 140,000 oz of gold and 12 million pounds of copper intermittently from 1912 to 1971, from 526,678 tonnes averaging 8.31 g/t Au and 1.03% Cu. Queenston commenced exploration on the property in 2005 and defined the first new mineral resource in 2009. Since 2005 three-hundred and eighty new diamond drill holes (including wedges) have been completed on the property, representing 236,874 metres of drilling.

A Preliminary Economic Assessment ("PEA") was completed on Upper Beaver in early 2012 (Queenston press release, February 16, 2012). The PEA studied the economics of building a 2,000 tonne per day mine/mill complex at Upper Beaver that would produce on average 120,000 oz of gold and 5.3 million pounds of copper annually with first production targeted in 2016. The permit to sink a new 1,300 m deep shaft was received in September 2012 and detailed engineering, procurement and shaft collar excavation have commenced. The PEA incorporated the May 2011 mineral resource for Upper Beaver, containing 3,074,000 t averaging 7.0 g/t Au (690,000 oz) with 0.5% Cu (36.6 M lbs) (Indicated) and 3,093,000 t averaging 6.2 g/t Au (616,000 oz) with 0.4% Cu (28.0 M lbs) (Inferred) (Queenston press release, May 4, 2011).

An updated mineral resource was announced on September 2012, increasing the indicated resource by 112% to 6,870,000 t averaging 6.6 g/t Au (1,461,000 oz) and 0.37% Cu (56 M lbs), and increasing the inferred resource by 16% to 4,570,000 t averaging 4.9 g/t Au (712,000 oz) and 0.32% Cu (32 M lbs) (Queenston press release, September 26, 2012).

The focus at Upper Beaver for 2013-2014 will be on the development of the 1,300 metre exploration shaft, including engineering, design and fabrication of the head frame and hoisting facilities budgeted at $70 million. The shaft collar has now been established to a depth of 26 metres and exploration on the deposit continues with six drills. In addition to the development program at Upper Beaver the Company has budgeted an additional $20 million for 2013 exploration in the Kirkland Lake gold camp.

Quality Control

True widths of reported intervals are interpreted based on drill-hole intercepts and interpreted orientations of intersected lithologies and are estimated at 65-80% of the core length interval. Assays are uncut. Intercepts occur within geological confines of major zones but have not been correlated to individual vein domains at this time. All NQ core assays reported were obtained by standard 30 g fire-assaying-AA finish or gravimetric finish at Swastika Laboratories of Swastika, Ontario. 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. The Upper Beaver project is supervised by Mark Masson, P.Geo. Standards and blanks are submitted every 25 samples for QA/QC purposes by the Company as well as the lab. Approximately 5% of sample rejects and/or pulps are sent to secondary laboratories for check assaying.

Mr. William McGuinty, P.Geo. is Project Manager for Osisko Mining Ltd. and is the Qualified Person responsible for the technical information reported herein, including verification of the data disclosed.

About Osisko

Osisko Mining Corporation operates the Canadian Malartic Gold Mine in Malartic, Quebec and is carrying out aggressive exploration and project development elsewhere in Canada and Latin America.

Cautionary Notes Concerning Estimates of Mineral Resources

This news release uses the terms measured, indicated and inferred resources as a relative measure of the level of confidence in the resource estimate. Readers are cautioned that mineral resources are not economic mineral reserves and that the economic viability of resources that are not mineral reserves has not been demonstrated. In addition, inferred resources are considered too geologically speculative to have any economic considerations applied to them. It cannot be assumed that all or any part of an inferred mineral resource will ever be upgraded to a higher category. Under Canadian rules, estimates of inferred mineral resources may not form the basis of feasibility or pre-feasibility studies or economic studies except for Preliminary Assessment as defined under NI 43-101. Readers are cautioned not to assume that that further work will lead to mineral reserves that can be mined economically.

Forward-Looking Statements

Certain statements contained in this press release may be deemed "forward-looking statements". All statements in this release, other than statements of historical fact, that address events or developments that Osisko expects to occur, are forward looking statements. Forward looking statements are statements that are not historical facts and are generally, but not always, identified by the words "expects", "plans", "anticipates", "believes", "intends", "estimates", "projects", "potential", "scheduled" and similar expressions, or that events or conditions "will", "would", "may", "could" or "should" occur including, without limitation, the continued development of the Upper Beaver project and more specifically the development of the exploration shaft. Although Osisko believes the expectations expressed in such forward-looking statements are based on reasonable assumptions, including, without limitation, that all technical, economical and financial conditions will be met in order to achieve such events qualified by the foregoing cautionary note regarding forward looking statements, such statements are not guarantees of future performance and actual results may differ materially from those in forward looking statements. Factors that could cause the actual results to differ materially from those in forward-looking statements include gold prices, access to skilled consultants, mining development and construction personnel, results of exploration and development activities, Osisko's limited experience with production and mining operations, uninsured risks, regulatory framework and changes, defects in title, availability of personnel, materials and equipment, timeliness of government approvals, actual performance of facilities, equipment and processes relative to specifications and expectations, unanticipated environmental impacts on operations market prices, continued availability of capital and financing and general economic, market or business conditions. These factors are discussed in greater detail in Osisko's most recent Annual Information Form and in the most recent Management Discussion and Analysis filed on SEDAR, which also provide additional general assumptions in connection with these statements. Osisko cautions that the foregoing list of important factors is not exhaustive. Investors and others who base themselves on forward-looking statements should carefully consider the above factors as well as the uncertainties they represent and the risk they entail. Osisko believes that the expectations reflected in those forward-looking statements are reasonable, but no assurance can be given that these expectations will prove to be correct and such forward-looking statements included in this press release should not be unduly relied upon. These statements speak only as of the date of this press release.

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