MONTREAL, QUEBEC--(Marketwire - June 14, 2011) - Osisko Mining Corporation ("Osisko") (News - Market indicators)(FRANKFURT:EWX) and Golden Valley Mines Ltd. (TSX VENTURE:GZZ) are pleased to announce final results from the 2010 drill program at the Jeffrey Zone on the Malartic CHL Property, currently under option from Golden Valley Mines Ltd. and located immediately east of Osisko's 100%-owned Canadian Malartic gold mine.

Highlights from 74 new drill holes include: 63.6 metres averaging 1.50 g/t Au (CHL10-2351), 64.8 metres averaging 1.47 g/t Au (CHL10-2347, uncut), and 55.4 metres averaging 1.39 g/t Au (CHL10-2297). Assay results are summarized in the table below:

Drill holes CHL10-2302, CHL10-2308, CHL10-2321, CHL10-2326, CHL10-2329, CHL10-2334, CHL10-2335, CHL10-2339, CHL10-2340, CHL10-2342, CHL10-2346, CHL10-2359, CHL10-2361, CHL10-2364 and CHL10-2369 did not intersect significant mineralization. Definition drilling on the Jeffrey Zone is based on a series of sections spaced at 25 metre intervals over an east-west strike length of 400-metres and north-south distance of 135 metres. The objective of the current program is to gather sufficient drill information along strike and to depth to complete an initial indicated resource calculation by the end of Q3 2011. Additional drilling is also planned in order to investigate the extent of the zone recently discovered immediately south of the Jeffrey zone (see February 28, 2011 press release).

Mineralization at the Jeffrey Zone is located along the southern limit of the Cadillac Break, where it consists of disseminated pyrite-gold in potassic-altered quartz-feldspar porphyry dikes, in contact with a predominately ultramafic flow sequence, and in subordinate diorite-gabbro and sedimentary units. Narrower, higher-grade mineralization is hosted in quartz veined (silicified) porphyry or talcose and chlorite-altered ultramafic schists.

Continuity of steeply-dipping mineralization is now well established along a strike length of 400 metres (sections 7200E to 7600E), with a true width of 30 to 60 metres. Mineralization is more sporadic further east between sections 7600E and 8100E. Mineralization has been traced to a depth of 200 metres on most sections, where it remains open at depth. The western extremity of the Jeffrey zone (section 7200E) lies 800m east of the Canadian Malartic property, where Osisko defined the extension of the Barnat deposit. Based on previous work by East Malartic Mines Ltd and confirmed by 2009 drilling from section 6400E to 6550E (see Golden Valley Mines March 23, 2010 press release), mineralization is known to extend onto the Malartic CHL property (the Mammoth zone). An additional 2,223m of drilling was conducted in this area in late 2010 and early 2011. Assay results from this work are pending.

All NQ core assays reported above were obtained by standard 50 g fire assaying-AA finish or gravimetric finish at ALS Chemex laboratories in Val d'Or, Quebec. Reported drill core weighted averages were calculated using a minimum of 0.40 g/t Au over successive intervals of 20 metres. The lengths of mineralized intervals of less than 20 metres were minimized, and an upper cut-off of 30 g/t Au was applied to individual assays where indicated. Intervals containing individual assays that are greater than six times the average of the interval are included separately. Intersected drifts or lost core within mineralized intersections were incorporated as blank intervals.

Osisko follows strict QA-QC protocol measures in keeping with industry standards and regulatory reporting requirements. Mr. Robert Wares, P. Geo. and Executive Vice-President of Osisko, and Mr. François Bouchard, P. Geo., are the Qualified Persons who has reviewed this news release and are responsible for the technical information reported herein, including verification of the data disclosed including the sampling, analytical and test data underlying the technical information.

Osisko has the right to acquire a 70% interest in the Malartic CHL Property in consideration for $150,000 in cash payments over a four year period (total amount paid) and by completing a minimum $2,000,000 in exploration work over a four year period (funds currently expended). Upon earning its 70% interest, Abitibi Royalties Inc., Golden Valley's wholly owned subsidiary, will maintain a free-carried interest of 30% to production.

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 on the stated resources 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 commencement of commercial production. 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 warrant further development of the project, 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 personnel, results of exploration and development activities, Osisko's limited experience with production and development stage mining operations, uninsured risks, regulatory 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.