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Press release from Marketwire

Osisko and Clifton Star Release Resource Estimate for the Beattie Deposit

Monday, June 13, 2011

Osisko and Clifton Star Release Resource Estimate for the Beattie Deposit10:15 EDT Monday, June 13, 2011MONTREAL, QUEBEC--(Marketwire - June 13, 2011) - Osisko Mining Corporation ("Osisko")(TSX:OSK)(FRANKFURT:EWX) and Clifton Star Resources Inc ("Clifton")(TSX VENTURE:CFO)(FRANKFURT:C3T) are pleased to provide an independent NI 43-101 compliant gold mineral resource estimate for the Beattie deposit at the Duparquet Project, located in the Abitibi region of Quebec. This estimate is restricted to the Beattie deposit, part of the larger Beattie-Donchester mineralized corridor, which was the focus of the 2010 drill program. To be clear, this resource estimate does not include the Donchester, Central Duparquet, Duquesne and Beattie tailings deposits, which are also part of the Duparquet Project.Key points:The in situ inferred resource is 2.77 million ounces gold (56.2 million tonnes grading 1.53 g/t Au) using a cut-off grade of 0.67g/t. The selected base case in-pit inferred resource is 1.72 million ounces (32.0 million tonnes grading 1.67 g/t Au), based on a Whittle-optimized pit shell simulation using estimated operating costs, a gold price of CAN$1100 per ounce and a corresponding lower cut-off grade of 0.67 grams per tonne gold. At a CAN$1500 per ounce gold price, the in-pit inferred resource increases to 2.50 million ounces at an average grade of 1.39 grams per tonne gold, adding 780,000 ounces compared to the CAN$1100 pit shell and a corresponding lower cut-off grade of 0.49 grams per tonne gold. No estimate was provided for the eastern extension of the mineralized corridor (Donchester portion, East of Beattie) as 2010 drilling was insufficient to include this portion in a resource category. The mineralized system is still open at depth. SGS Canada Inc, (SGS Geostat office of Blainville, Québec, "SGS") are the independent resource estimate consultants for the Duparquet project who have authorized the release of the following estimates. The in situ inferred resource is 2.77 million ounces of gold at an average undiluted grade of 1.53 g/t Au, based on a lower cut-off grade of 0.67 g/t Au. The table below summarizes the SGS block model estimates using variable lower cut-off grades:Beattie Deposit In Situ Inferred Resource Estimates Inferred ResourcesGrade (g/t)Tonnes (M)Oz (M)Cut-off (g/t)0.77161.23.980.200.97115.53.620.301.1590.33.340.401.3074.23.110.501.4462.52.900.601.5356.22.770.671.6946.82.550.801.8141.02.390.901.9336. also estimated an in-pit Inferred resource within a Whittle-optimized pit shell using a base case gold price of CAN$1100 per ounce. The in-pit Inferred resource for the Beattie deposit is 1.72 million ounces of gold at an average undiluted grade of 1.67 g/t Au, based on a derived lower cut-off grade of 0.67 g/t Au. The table below summarizes the in-pit resources sensitivity using variable gold price in Whittle optimizations:Beattie Deposit Inferred Resource Estimates within various Whittle Pit ShellsGold Price (CAN$)Grade (g/t)Tonnes (M)Oz (M)Strip Ratio (Waste/Ore)$4003.631.300.156.5$5003.072.650.266.5$6002.685.420.477.5$7002.437.270.577.0$8002.1311.50.787.3$9001.9417.81.118.3$10001.7826.21.509.0$11001.6732.01.728.9$12001.5839.42.019.3$13001.5244.22.169.1$14001.4451.62.399.2$15001.3955.92.509.0The in-pit estimate is based on a mining cost of CAN$1.50 per tonne and a processing cost of CAN$20.00 per tonne (including G&A), assuming oxidation pre-treatment of the mineralized material, giving base cost of CAN$34.85 per tonne. Other assumptions include 85% recovery of gold in oxidized material and pit wall slope angle of 50 degrees. Details on the parameters of the resource estimates are as follows:The database used for Beattie comprised a total of 127,540 metres of drilling obtained from the 2008-2009 Clifton Star programs and from the 2010 Osisko drill program. Most Clifton Star core was re-assayed in order to standardize the data base. All NQ assays reported by Osisko in 2010 were obtained by standard 50 g fire assaying-AA finish or gravimetric finish at ALS Chemex laboratories in Val d'Or, Quebec. The SGS database also comprised a total of 87,744 assays with an average of 1.41 metre per sample for a total of 123,827 assayed metres. The estimates were done using Inverse Distance Square (ID2) as the interpolation method based on 1.5 metre analytical composites. Composites calculations are based on original samples, and no capping was required. All estimates are based on a Parent Cell dimension of 10 metres E, 2 metres N and 5 metres height with search ellipsoid and estimation parameters determined for each of the mineralized zone geometries. The block model extends from UTM 629,650E to 631,650E and 5,373,930N to 5,374,980N from surface (300m) to -240m above sea level. Geological interpretation for the deposit identified five main structurally-controlled mineralized domains and a lower grade envelope hosted by syenite porphyry. The estimation of each mineralized domain was done with composites within the domain. A separate estimation run was done with remaining composites outside the main domains to estimate mineralized material outside the main mineralized domains but within the lower grade envelope. Underground voids were modeled from historical mine plans and adjusted according to positions of drill intersections in stopes and drifts. The blocks in the voids were discarded from the resource estimate. Tonnage estimates are based on rock densities of 2.70 tonnes/cubic metre. The resource estimates using the lower cut-off of 0.67 g/t Au is emphasized for reporting purposes as this is the in-pit cut-off estimated for the CAN$1100 Whittle shell, which represents the reasonable potential of economic extraction in SGS QP's opinion. The CAN$1100 Whittle shell has approximate maximum dimensions of 1,600 metres in length, 850 metres in maximum width and a maximum vertical depth of 400 metres. Mr. Claude Duplessis, Ing. of SGS and Mr. Robert Wares, P. Geo. and Executive Vice-President of Osisko, are the Qualified Persons who have reviewed this news release and are responsible for the technical information reported herein, including verification of the data disclosed.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 and Clifton (collectively the "Parties") expect 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 the Parties believe 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 Duparquet 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, the Parties' 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 Clifton's most recent Management Discussion and Analysis filed on SEDAR, which also provide additional general assumptions in connection with these statements. The Parties caution that the foregoing list of important factors is not exhaustive. Investors and others who base themselves on the Parties' forward-looking statements should carefully consider the above factors as well as the uncertainties they represent and the risk they entail. The Parties believe 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.FOR FURTHER INFORMATION PLEASE CONTACT: John BurzynskiOsisko Mining CorporationVice-President Corporate Development416-363-8653www.osisko.comORHarry MillerClifton Star