Osisko Reports 124 Metres Averaging 0.73 g/t Au in Southeast Extension at Hammond Reef

MONTREAL, QUEBEC--(Marketwire - Feb. 24, 2011) - Osisko Mining Corporation ("Osisko"), (TSX:OSK)(FRANKFURT:EWX) is pleased to announce initial results from the fall 2010 drilling program at the Hammond Reef gold project, located near Atikokan in western Ontario. The Hammond Reef project is 100 percent owned by Osisko Hammond Reef Gold Ltd., a wholly-owned subsidiary of Osisko. The fall 2010 program included 324 holes for approximately 119,000 metres.

Results from a total of forty-one new holes are presented below. These holes were all drilled to test the southeast (down-dip) extension of the deposit in the area of the Mitta Zone as well as the western portion of the 41 Zone (between sections 2145 E and 3045 E), over an area measuring 825 by 500 metres. All but four holes intersected significant mineralization. Highlights include 124 metres averaging 0.73 g/t Au (BR-410A), 45 metres at 1.86 g/t Au (BR-6057) and 49.5 metres averaging 1.83 g/t Au (BR-6042). Assay results are summarized in the tables below:

Hole No.	Section	From (m)	To (m)	Length (m)	Au g/t
BR-0410A	2720 E	216.0	340.0	124.0	0.73
including		258.0	259.5	1.5	7.14
BR-0411	2520 E	302.9	346.5	43.6	0.92
And		400.5	431.0	30.5	0.60
BR-0416	2420 E	319.8	348.5	28.7	0.75
And		395.1	468.5	73.4	0.65
BR-0419	2620 E	254.8	270.2	15.4	1.86
And		334.5	360.0	25.5	0.77
BR-0425	2620 E	321.5	347.0	25.5	0.46
And		527.0	528.5	1.5	14.75
BR-0426	2620 E	305.0	368.0	63.0	0.93
BR-0429	2945 E	166.5	192.0	25.5	0.52
And		222.0	244.5	22.5	1.62
BR-1028	2220 E	292.5	340.5	48.0	0.46
BR-4013	2820 E	117.5	134.0	16.5	0.64
And		168.5	195.5	27.0	0.49
And		321.5	344.0	22.5	0.41
BR-4017	2845 E	87.0	99.5	12.5	0.44
And		240.5	255.0	14.5	0.74
And		276.5	343.8	67.3	0.59
And		376.4	407.4	31.0	1.65
BR-4022A	2745 E	207.7	317.0	109.3	0.61
And		342.5	371.9	29.4	0.70
BR-4028	2670 E	191.0	236.0	45.0	0.68
And		296.0	318.5	22.5	0.59
And		349.6	382.6	33.0	0.70
including		349.6	350.8	1.2	10.80
BR-4037	2620 E	243.0	244.3	1.3	10.45
And		307.5	358.5	51.0	0.71
And		379.5	399.0	19.5	0.63
BR-4046	2770 E	196.4	252.5	56.1	1.12
And		294.5	341.0	46.5	0.64
including		340.0	341.0	1.0	9.52
BR-6000	2520 E	407.0	419.0	12.0	1.02
And		473.0	539.0	66.0	0.60
BR-6001A	2720 E	338.0	393.5	55.5	0.52
And		426.8	449.0	22.2	0.78
BR-6002	2420 E	311.0	359.0	48.0	0.68
And		420.5	461.0	40.5	0.77
BR-6004	2220 0	233.5	357.0	123.5	0.63
And		423.0	447.0	24.0	0.71

BR-6006	2820 E	261.0	279.5	18.5	0.63
And		389.2	407.0	17.8	0.60
BR-6008	2195 E	283.7	295.5	11.8	0.84
And		316.5	351.0	34.5	0.58
BR-6013	2195 E	247.4	357.0	109.6	0.60
BR-6015	2545 E	318.5	353.0	34.5	1.09
And		377.0	392.0	15.0	0.49
And		426.5	440.0	13.5	1.35
BR-6020	2320 E	329.7	342.2	12.5	0.72
And		402.4	438.0	35.6	0.85
BR-6022	2445 E	287.0	312.5	25.5	0.96
BR-6025	2470 E	307.5	363.0	55.5	0.67
And		426.0	441.0	15.0	1.16
And		502.5	515.4	12.9	0.82
BR-6029	2370 E	326.0	358.6	32.6	0.94
including		356.3	357.3	1.0	12.55
And		399.7	418.6	18.9	0.51
BR-6034A	2420 E	331.4	360.3	28.9	1.01
And		378.0	406.2	28.2	0.51
BR-6042	2770 E	280.5	330.0	49.5	1.83
including		283.5	288.0	4.5	14.97
BR-6043	2570 E	289.7	368.8	79.1	0.60
BR-6045A	2370 E	483.0	516.0	33.0	1.17
BR-6052	2520 E	234.0	247.5	13.5	0.60
And		384.0	451.5	67.5	0.43
BR-6054A	2420 E	277.9	285.0	7.1	0.63
And		481.5	501.0	19.5	0.80

DOWN-DIP STEP OUT HOLES

Hole No.	Section	From (m)	To (m)	Length (m)	Au g/t
BR-6056	2770 E	193.8	201.5	7.7	1.63
And		370.5	391.9	21.4	1.33
BR-6057	2145 E	190.5	199.5	9.0	0.51
And		325.5	370.5	45.0	1.86
BR-6065	2470 E	305.8	343.2	37.4	0.48
And		368.5	430.5	62.0	0.65
BR-6066	2670 E	240.0	249.0	9.0	0.56

Drill hole BR-346 on Section 3045E, and four holes (BR-382A, -6038, -6053 and -6066) located at the down-dip (SE) extremity of the deposit (between Sections 2320E and 2720E) did not intersect significant mineralization. The above holes, along with previously announced holes, confirm the down-dip extension of the deposit between sections 1320E and 2845E (approx. 1500 m strike length) over a true down-dip distance of as much as 500 metres.

The current drill program at Hammond Reef comprises mostly definition drilling within the known resource volume as well as exploration/step-out holes in the immediate area of the deposit. It includes definition drilling on 50 by 25 metre grid along the 2.65 kilometre strike length of the known deposit (sections 1070E to 3725E), as well as step-out holes down-dip and up-dip of the know deposit. A 250,000 metre drill program is slated for 2011 with eighteen drills active on the property.

Osisko is presently focused on upgrading and expanding gold resources at Hammond Reef. A Preliminary Assessment Study was completed on the deposit on November 12, 2009 and filed on SEDAR, resulting in an Inferred Mineral Resource of 6.70 million ounces of gold (259.4 million tonnes grading 0.8 grams per tonne (g/t) gold at a cut-off grade of 0.30 g/t, which relates to the economic cut-off in the PA Study). The deposit remains open along strike and down-dip; over 97% of this resource is within 300 metres of surface. For additional details of the resource estimates at Hammond Reef please refer to the November 12, 2009, July 23, 2009 and October 15, 2008 news releases of Brett Resources Inc. The deposit sits along a splay of the fertile Finlayson Fault Zone , of which Osisko covers 27 km of strike length as a result of the 2010 property acquisitions, including the Sparton Resources property.

All NQ core assays reported above were obtained by standard 50 g fire assaying-AA finish or gravimetric finish at ALS Chemex laboratories in Thunder Bay, Ont., and North Vancouver, B.C., ISO/IEC guideline 17025-accredited facilities. Reported drill core weighted averages were calculated using a minimum of 0.35 g/t Au over successive maximum intervals of 20 metres. Lost core within mineralized intersections were incorporated as blank intervals and assigned a 0.001 g/t grade in all length weighted calculations. Osisko follows strict QA-QC protocol measures in keeping with industry standards and regulatory reporting requirements. Mr. Sergio Cattalani, PGeo. and Vice-President Exploration 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 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 Brett (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 Hammond Reef 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 Brett'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.

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