Osisko and Clifton Star release resource estimate for Beattie deposit, Quebec

Osisko Mining Corporation (“Osisko”, OSK – TSX; EWX – Deutsche Boerse) and Clifton Star Resources Inc (“Clifton”, CFO – TSXV; C3T – Deutsche Boerse) 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:

SGS 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:

The 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.

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