Osisko Mining Corporation
TSX : OSK
FRANKFURT : EWX

Osisko Mining Corporation

November 28, 2007 08:00 ET

Osisko Reports Positive Phase II Metallurgical Test Results

MONTREAL, QUEBEC--(Marketwire - Nov. 28, 2007) - Osisko Exploration Ltd. (TSX:OSK) (FRANKFURT:EWX) is pleased to announce that it has received positive Phase II metallurgical results from its 100% owned Canadian Malartic gold project. The Phase II metallurgical program was designed to test direct whole ore cyanidation and cyanidation of flotation concentrate process to assess the gold recoveries of the Canadian Malartic orebody and to evaluate the optimum grind size for best economic gold recovery. Direct whole ore cyanidation reported recoveries from 80% - 86% on samples with a 1 g/t Au head grade representative of the Canadian Malartic orebody based on 80% -200 mesh grind size. Flotation work indicates +90% recovery of gold to the primary concentrate at a coarser grind size than the direct whole ore cyanidation route. Overall recovery is still pending.

Phase II metallurgical work regarding hardness and work index has confirmed numbers reported earlier in the NI 43-101 report filed in January of 2007. The work index ranges from 12 - 16 kW-h/t. Canadian Malartic ore is considered to be abrasive and falls within the "moderately hard" category.

A Phase III detailed metallurgical test program has now been initiated to optimize and fully evaluate the economic and environmental benefits of a flotation concentrate/cyanidation circuit, compared to a direct whole ore cyanidation circuit. The Phase III test work is specifically designed to evaluate the ability to increase throughput using the same grinding circuit equipment. This would reduce unit operation costs, resulting in lower operating costs and increased annual gold production. As both methods are providing robust recoveries, this more detailed test program will provide the economic basis for the final decision on the best recovery method for the Canadian Malartic process facility. Currently it is believed that both methods represent relatively similar capital costs. However, flotation does have advantages in terms of flexibility in handling more varied head grades and ore types. In addition, the flotation/cyanidation process route has potential to increase the production rate due to the benefit of being able to grind to a coarser size distribution.

The Phase III detailed test work should be completed by the end of Q1 2008.

All test work was carried out on composite samples prepared from fresh NQ core taken throughout the deposit, to provide representative quantities of all ore types and lithologies that would be encountered in potential mining.

Sean Roosen, President of Osisko commented: "We are very encouraged by the positive results of the Phase II work, which confirms the relatively simple metallurgical nature of the Canadian Malartic deposit. The Phase III detailed test work will help us better understand the benefits of a flotation circuit - this is important to our shareholders and has ramifications beyond the Canadian Malartic deposit. It could provide us with added flexibility to deal with other deposits we may discover on the property, without major changes to the mill or additional Capex in the future."

The metallurgical test work for the Osisko Canadian Malartic Project has been supervised and reviewed by David Runnels, P.Eng. of BBA Inc., who is a Qualified Person as defined by National Instrument NI 43-101.

Osisko Exploration Ltd. is currently evaluating the Canadian Malartic gold deposit and adjacent areas for a large-scale open pit, bulk-tonnage mining operation. The Company is well-funded with approximately $200 million on hand and is carrying out an aggressive definition drilling and exploration campaign with 15 drills on the Canadian Malartic deposit and surrounding property. An updated NI 43-101 compliant, inferred gold resource estimate on the main deposit was released on July 5, 2007 and the full report is available on SEDAR.

Contact Information

  • Osisko Exploration Ltd.
    John Burzynski
    Vice-President Corporate Development
    514-735-7131
    www.osisko.com
    or
    Osisko Exploration Ltd.
    Daniel Boase
    Investor Relations
    416-742-5600
    Toll Free: 1-866-580-8891