Osisko Reports Record Quarterly Production from Canadian Malartic

MONTREAL, QUÉBEC--(Marketwire - Oct. 10, 2012) - Osisko Mining Corporation (the "Company" or "Osisko") (TSX:OSK)(FRANKFURT:EWX) is pleased to report record third quarter goldproduction of 103,753 ounces from its flagship Canadian Malartic Mine. Year to date, Canadian Malartic has produced a total of 286,934 ounces of gold. Since commencement of operations in April, 2011, Canadian Malartic has produced a total of 487,072 ounces of gold.

Third Quarter Operating Highlights

• Record quarterly gold production of 103,753 ounces
• Record monthly mill throughput of 43,073 tonnes per calendar day in August
• Record one-day mill throughput of 53,302 tonnes achieved on September 20^th
• Grade milled in third quarter averaged 0.97 g/t Au
• Recoveries continue to be higher than feasibility modeling at 88.7 percent

New mill throughput records

The mill processed at an average rate of 40,834 tonnes per calendar day during the period, a 14.8% increase over the average mill throughput in the second quarter. The mill processed a record 53,302 tonnes on September 20, 2012.

September Throughput

Throughput in the month of September averaged 37,384 tonnes per calendar day. This figure includes approximately 5 days of complete shut-down for a scheduled seven-day maintenance period, during which liners in the secondary crushers, SAG and ball mills and other wear parts were replaced for the first time subsequent to the May fire. Throughput in the month of September on an operating day basis (exclusive of the shut-down period) averaged 44,861 tonnes per day. Throughput in the last two weeks of September (subsequent to the completion of the scheduled maintenance and full re-start) averaged 48,155 tonnes per day, and included six days where production exceeded 50,000 tonnes per day.

October Throughput Preview

Crushing and milling throughputs have continued to improve and move towards design rates in the early part of October. Mill throughput in the first eight days of October averaged 50,670 tonnes per day. Another new record one-day processing rate of 53,374 was achieved on October 3^rd.

Gold Sales

During the third quarter, the Company sold 95,424 ounces at an average price of US $1,659 (CAD $1,646), compared to an average market price of US $1,652 (CAD $1,644). During the first three quarters, the Company sold 283,499 ounces at an average realized price of US $1,654 (CAD $1,657), compared to an average market price of US $1,652 (CAD $1,655).

Sean Roosen, President and Chief Executive Officer, commenting on the third quarter operating preview: "We have had a very solid third quarter at Canadian Malartic, achieving a new quarterly production record of 103,753 ounces of gold. We have remained focused on increasing the average daily, monthly and quarterly throughput rates in the crushing and milling circuit, and the hard work our team has been doing is starting to show good results. We can proudly report improvements in operational throughput rates, and in the last three weeks we have been starting to see the circuit stabilize at rates of over 48,000 tonnes per day, and over 50,000 tonnes per day in the first eight days of October. Recoveries remain above our feasibility numbers averaging 88.7% for the quarter. The third quarter average grade of 0.97 g/t Au is slightly lower than we'd hoped for. We are currently in discussions with the MDDEFP (Ministère du Développement durable, de l'Environnement, de la Faune et des Parcs) regarding a highly technical blast in one of the higher-grade portions of the main deposit. This work affects approximately one million tonnes of rock and involves knocking in three crown pillars at once, over the old open stopes from the historic Canadian Malartic underground mine. The blast has been designed to maximize worker safety, but currently the MDDEFP has requested a review of the design. The discussions have slowed us down in accessing some of the higher grades zones, and it's required us to concentrate mining in areas of average to lower grade material. In the meantime, the second pebble crusher is in preparation for installation at the end of October, with commissioning set for November. At that point we hope to see throughputs move towards the design rate of 55,000 tonnes per day."

Conference Call

The Company expects to release its third quarter financial results after the close of business on November 13th, 2012. Osisko will host a conference call on Wednesday, November 14th at 8:00am ET, where senior management will discuss the financial results and provide an update of the Company's activities. Those interested in participating in the conference call should dial in at 416-981-9012 (Toronto local and international), or 1-800-909-4792 (North American toll free). An operator will direct participants to the call.

About Osisko Mining Corporation

Osisko Mining Corporation operates the Canadian Malartic Gold Mine in Malartic, Quebec and is pursuing exploration on a number of properties, including the Hammond Reef Gold Project in Northern Ontario.

Mr. Luc Lessard, Eng., Senior Vice-President and COO of Osisko, is the Qualified Person who has reviewed this news release and is responsible for the technical information reported herein, including verification of the data disclosed.

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, continuous production improvement, timely preparation installation of the second pebble crusher upon receipt of the installation permit, gaining access to some of the higher grades zones following the execution of a highly technical blast being discussed with the MDDEFP. Although Osisko believes the expectations expressed in such forward-looking statements are based on reasonable assumptions, including, without limitation, that the diligent ongoing optimizing of its operations at its Canadian Malartic mine and mill will be achieved in a timely manner and will, accordingly, improve its operating performance to design rate, 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.