Osisko Intersects 2.16 g/t Au Over 129.5 Metres at South Barnat

• Press Release
• Source: Osisko Mining Corporation
• On 8:00 am EDT, Wednesday September 23, 2009

MONTREAL, QUEBEC--(Marketwire - 09/23/09) - Osisko Mining Corporation ("Osisko") (TSX:OSK - News)(Frankfurt:EWX - News) is pleased to announce partial drilling results from the Q2-Q3 2009 drill program within the model pit on the South Barnat deposit. Following the release of the South Barnat Measured and Indicated resource estimate (June 2, 2009 press release), the Company proceeded with a phase three definition drill program on deeper portions of known mineralized zones within and below the Whittle-optimized pit shell. This was accompanied by a condemnation drill program designed to test presumed barren, outer portions of the model pit for additional mineralization. Unanticipated gold mineralization was encountered in a number of locations, pointing to the potential for expansion of the in-pit resource at Barnat. All results reported below were not included in the June 2, 2009 resource estimate.

Significant new drill intersections include 2.16 g/t Au over 129.5 metres (BA08-3611), 1.23 g/t Au over 88.0 metres (BA08-3554E) and 1.11 g/t Au over 176.2 metres (BA08-3663). Highlights from new infill holes on known mineralized zones are tabled below:

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  Hole No.       Section     From (m)     To (m)     Length (m)     Au g/t

BA09-3554E        BA550E         8.8       28.0           19.2        0.79
       and                     161.5      249.5           88.0        1.23
       and                     332.0      383.5           51.5        1.64
 including                     368.0      369.5            1.5       13.30

 BA09-3571        BA775E       290.0      320.0           30.0        1.20
       and                     378.5      405.6           27.1        1.18

 BA09-3590        BA500E       254.5      288.0           33.5        0.84

 BA09-3603        BA550E       307.5      354.0           46.5        1.87

 BA09-3607        BA050E        23.0      112.3           89.3        0.90

 BA09-3611        BA600E       272.5      402.0          129.5        2.16
 including                     334.0      340.0            6.0        7.92

 BA09-3625        BA425E         7.1      122.5          115.4        0.88
       and                     149.5      159.9           10.4        16.5

 BA09-3626        BA425E        57.2       99.0           41.8        1.47
       and                     136.9      145.1            8.2        3.52
       and                     167.5      198.3           30.8        2.42
 including                     195.8      196.8            1.0       12.15

 BA09-3636        BA650E       269.0      321.5           52.5        1.19
       and                     390.5      420.5           30.0        1.16

 BA09-3663        BA525E        21.0       37.0           16.0        1.30
       and                     103.0      279.2          176.2        1.11
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Significant drill intersections from new mineralized zones located on the outer margins of the model pit include 2.72 g/t Au over 25.4 metres (BA08-3577), 0.60 g/t Au over 107.5 metres (BA08-3632) and 0.83 g/t Au over 91.5 metres (BA08-3638). Highlights from the intersections in new mineralized zones are tabled below:

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  Hole No.       Section     From (m)     To (m)     Length (m)     Au g/t

 BA09-3561       CM5800E       272.0      284.4           12.4        4.57

 BA09-3565        BA325E        51.0       93.5           42.5        0.77

 BA09-3577        BA550E        70.9       96.3           25.4        2.72
 including                      70.9       72.5            1.6       19.05

 BA09-3600        BA625E        41.1       68.4           27.3        1.38

 BA09-3630        BA625E        55.5      105.0           49.5        0.73

 BA09-3632        BA150E       112.5      220.0          107.5        0.60
       and                     246.0      259.5           13.5        0.71

 BA09-3633        BA775E       244.0      291.5           47.5        1.49
 including                     245.5      247.0            1.5       13.50

 BA09-3637        BA650E        16.0      108.0           92.0        0.75

 BA09-3638        BA650E        22.0      113.5           91.5        0.83

 BA09-3639        BA575E        30.5       52.0           21.5        1.16

 BA09-3641        BA600E        36.0       55.5           19.5        0.99
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The mineralized intersections in drill holes BA09-3561 and BA09-3633 and the second intersection in drill hole BA09-3632 are below current pit model limits.

Results from this drill program on South Barnat are being integrated into a new data base along with new drill results from the Southeastern Extension of the Canadian Malartic deposit. The new data base will be used to calculate an updated global resource, from which a new reserve estimate in a merged engineered pit will be calculated for the combined Canadian Malartic and South Barnat deposits. This new reserve estimate is scheduled to be released by year end.

All NQ or HQ 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 weighted averages were calculated using a minimum of 0.50 g/t Au over successive maximum intervals of 20 metres with no upper cut-off of individual assays. Intersected drifts or lost core within mineralized intersections were incorporated as blank intervals.

Osisko Mining Corporation is currently developing the Canadian Malartic gold deposit and evaluating adjacent areas for a large-scale open pit, bulk-tonnage mining operation. The Canadian Malartic deposit currently represents one the biggest gold reserves in Canada for a single deposit, and is still growing through ongoing drilling on new mineralized zones. Current reserves for the Canadian Malartic property are 6.28 million ounces, plus (including the Barnat deposit) a measured and indicated resource of 3.65 million ounces and an inferred resource of 0.84 million ounces. Mr. Robert Wares, P. Geo. and Executive Vice-President 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 including the sampling, analytical and test data underlying the technical information.

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 the Corporation 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. Although the Corporation 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 put the Canadian Malartic Project into commercial production, 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 and mill production personnel, results of exploration and development activities, the Corporation'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 the Corporation's most recent Annual Information Form filed on SEDAR, which also provides additional general assumptions in connection with these statements. The Corporation cautions that the foregoing list of important factors is not exhaustive. Investors and others who base themselves on the Corporation's forward-looking statements should carefully consider the above factors as well as the uncertainties they represent and the risk they entail. The Corporation 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.

 
Contacts:
Osisko Mining Corporation
John Burzynski
Vice-President Corporate Development
514-735-7131
Osisko Mining Corporation
Sylvie Prud'homme
Investor Relations
514-735-7131
Toll Free: 1-888-674-7563
www.osisko.com