Osisko Drilling Adds More High Grade at Windfall

78.5 g/t Au Over 2.0 Metres in Zone 27


TORONTO, May 18, 2021 (GLOBE NEWSWIRE) -- Osisko Mining Inc. (OSK:TSX. "Osisko" or the "Corporation") is pleased to provide new analytical results from the ongoing drill program at its 100% owned Windfall gold project located in the Abitibi greenstone belt, Urban Township, Eeyou Istchee James Bay, Québec.

Significant new analytical results presented below include 61 intercepts in 20 drill holes (15 from surface, 5 from underground) and 9 wedges. The infill intercepts are located inside defined February 2021 mineral resource estimate (“MRE”) blocks (see Osisko news release dated February 17, 2021). The expansion intercepts are located outside the February 2021 MRE blocks and either expand resource wireframes or are located in a defined zone or corridor but do not yet correlate to a specific wireframe.

Osisko Chief Executive Officer John Burzynski commented: “Today’s drilling results in the Main Zone areas of Windfall, including Underdog, mirror the results reported over the past weeks in Lynx: infill drilling continues to define grade continuity inside our MRE blocks and expansion drilling is adding ounces in the immediate surrounding areas. All infill and expansion drilling at Windfall is in support of our upcoming feasibility study.”

Selected high-grade intercepts include: 78.5 g/t Au over 2.0 metres, 58.3 g/t Au over 2.0 metres and 40.0 g/t Au over 2.0 metres in OSK-W-21-2479, 43.5 g/t Au over 2.7 metres and 38.5 g/t Au over 2.7 metres in OSK-W-21-2442-W1, 18.3 g/t Au over 6.1 metres in OSK-W-21-2496, 40.3 g/t Au over 2.4 metres in OSK-W-21-2455-W1, 44.4 g/t Au over 2.0 metres in OSK-W-21-2463, 42.8 g/t Au over 2.0 metres in WST-21-0643, and 40.2 g/t Au over 2.0 metres in OSK-W-20-2439. Maps showing hole locations and full analytical results are available at www.osiskomining.com

Infill Drilling

Hole NumberFrom
(m)
To
(m)
Interval
(m)
Au (g/t)
uncut
Au (g/t)
cut to
100 g/t
ZoneCorridor
OSK-W-17-777839.0841.02.03.52 Underdog_4101Underdog
 849.0851.02.05.41 Underdog_4101
Underdog
including850.6851.00.420.0 
 856.9858.92.05.63 Underdog_4101
Underdog
including857.5857.80.327.0 
OSK-W-20-913-W2801.0803.02.05.04 Caribou_2220Caribou
OSK-W-21-1827-W2504.0506.02.015.3 Caribou_2231
Caribou
including504.9505.50.642.7 
 511.3513.92.65.11 Caribou_2231
Caribou
including511.3512.10.811.5 
OSK-W-21-2442-W1447.0449.02.05.81 Z27_1203
Zone 27
including448.3449.00.716.3 
 637.3640.02.743.531.5Underdog_4101
Underdog
including637.3637.60.374.5 
and639.6640.00.4181100
 960.1962.82.738.534.7Underdog_4910
Underdog
including962.5962.80.3134100
OSK-W-21-2455-W1588.6590.72.14.72 Caribou_2232Caribou
 661.6663.62.05.50 Caribou_2208
Caribou
including663.0663.60.617.0 
 666.5668.82.34.86 Caribou_2208Caribou
 770.6773.02.440.337.6Caribou
Caribou
including772.1773.00.9107100
OSK-W-21-2463843.0845.02.044.422.6Underdog_4111
Underdog
including843.3843.70.4209100
OSK-W-21-2463-W2840.6843.02.43.75 Underdog_4110
Underdog
including840.6840.90.315.9 
 927.0929.02.017.3 Underdog_4101
Underdog
including927.4928.10.741.2 
 959.0961.02.04.27 Underdog_4100
Underdog
including960.0960.50.514.3 
 972.0974.02.04.77 Underdog_4102
Underdog
including972.0972.50.518.1 
 1082.01084.02.05.38 Underdog_4511
Underdog
including1082.61083.00.426.5 
OSK-W-21-2479638.0640.02.040.037.2Underdog_4100
Underdog
including639.0639.70.7108100
 642.6649.56.98.06 Underdog_4100
Underdog
including645.3646.10.822.0 
and649.0649.50.522.8 
OSK-W-21-2486533.0535.32.34.89 Caribou_2232
Caribou
including534.6535.30.710.2 
OSK-W-21-2496208.0214.16.118.3 F51_6008
F-51
including209.0210.01.045.3 
OSK-W-21-2504163.0165.42.45.69 F51_6008
F-51
including163.5164.51.013.3 
OSK-W-21-777-W1610.7612.92.217.1 Caribou_2233Caribou
OSK-W-21-777-W2568.0570.02.035.2 Caribou_2211Caribou
 572.0574.42.44.90 Caribou_2211Caribou
 611.0613.02.09.76 Caribou_2233Caribou

Notes: True widths are estimated at 55 – 80% of the reported core length interval. See "Quality Control and Reporting Protocols" below.

Expansion Drilling

Hole NumberFrom
(m)
To
(m)
Interval
(m)
Au (g/t)
uncut
Au (g/t)
cut to
100 g/t
ZoneCorridor
OSK-W-20-2399-W1451.0453.62.64.00 CaribouCaribou
OSK-W-20-2406404.0406.02.04.76 CaribouCaribou
 506.0508.02.011.5 Caribou
Caribou
including506.4507.00.628.2 
OSK-W-20-2432405.0407.02.03.65 CaribouCaribou
 763.0767.04.011.7 Caribou
Caribou
including763.0764.01.040.7 
OSK-W-20-243935.037.02.040.2 F11
F11
including35.036.01.077.0 
OSK-W-20-2440314.0316.92.93.67 CaribouCaribou
OSK-W-20-2441181.5184.42.95.07 CaribouCaribou
OSK-W-21-1882-W1744.0746.02.05.16 UnderdogUnderdog
OSK-W-21-2442-W1945.0947.12.18.49 UnderdogUnderdog
 948.0950.02.03.52 UnderdogUnderdog
OSK-W-21-2451436.0438.02.04.32 Caribou
Caribou
including436.4437.00.614.0 
OSK-W-21-2455440.0442.02.03.66 CaribouCaribou
OSK-W-21-2463323.0325.02.03.55 Caribou
Caribou
including324.0324.40.410.2 
 962.0964.12.15.85 Underdog
Underdog
including963.1964.11.012.2 
 1126.91129.02.17.07 Underdog
Underdog
including1126.91127.30.428.1 
OSK-W-21-2463-W2940.0942.02.04.23 UnderdogUnderdog
 1051.01053.02.04.17 UnderdogUnderdog
OSK-W-21-2479482.0484.02.078.516.8Z27
Zone 27
including482.3482.60.3511100
 485.4489.03.610.4 Z27Zone 27
 616.0618.32.311.3 Underdog
Underdog
including617.0617.30.384.3 
 625.1627.12.027.8 Underdog
Underdog
including626.3627.10.869.0 
 630.0632.02.04.97 Underdog
Underdog
including630.6631.00.422.6 
 899.9901.92.058.337.3Underdog
Underdog
including900.2900.90.7160100
 913.7916.83.125.017.7Underdog
Underdog
including916.5916.80.3176100
OSK-W-21-2483282.2284.52.37.55 CaribouCaribou
OSK-W-21-2490436.9439.02.15.06 Caribou
Caribou
including437.9438.20.335.0 
 560.1562.12.04.32 Caribou
Caribou
including561.3561.60.310.7 
WST-21-059717.719.92.26.48 BobcatBobcat
WST-21-0642150.0152.02.04.13 Bobcat
Bobcat
including150.6151.00.416.8 
WST-21-0643163.0165.02.042.8 Bobcat
Bobcat
including163.0164.01.085.4 
WST-21-064486.489.63.26.69 Bobcat
Bobcat
including86.487.20.817.2 
WST-21-065188.090.22.23.83 Bobcat
Bobcat
including88.389.00.78.60 

Notes: True widths are estimated at 55 – 80% of the reported core length interval. See "Quality Control and Reporting Protocols" below.

Drill hole location

Hole NumberAzimuth
(°)
Dip
(°)
Length
(m)
UTM EUTM NElevationSection
OSK-W-17-777330-59122145267854345004032675
OSK-W-20-2399-W1333-5487645287554345533982875
OSK-W-20-2406333-5669345263354342814002525
OSK-W-20-2432333-5786445280954344154042750
OSK-W-20-2439147-5036045251554360294063275
OSK-W-20-2440330-5280745273854344754012725
OSK-W-20-2441338-5940545271554346063972775
OSK-W-20-913-W2334-5291345287854344194012825
OSK-W-21-1827-W2331-5869045250654343904032475
OSK-W-21-1882-W1328-57119745246954344054002450
OSK-W-21-2442-W1347-53101145231554344193992325
OSK-W-21-2451330-5880345280954344154042750
OSK-W-21-2455328-5378045273854344764012725
OSK-W-21-2455-W1328-5379845273854344764012725
OSK-W-21-2463339-65133545261654344494032600
OSK-W-21-2463-W2339-65132545261654344494032600
OSK-W-21-2479344-5599345231554344193992325
OSK-W-21-2486334-57116745259654343924012550
OSK-W-21-2483328-5875645273154346343972800
OSK-W-21-2490338-6178645275654344664002725
OSK-W-21-2496158-5027945348454359674034100
OSK-W-21-2504161-4718645353354359474034125
OSK-W-21-777-W1330-5996945267854345004032675
OSK-W-21-777-W2330-59117045267854345004032675
WST-21-0597151-213245281754349432753025
WST-21-0642149-3817245295554350032533175
WST-21-0643129-4122045295554350032533175
WST-21-0644130-412045295554350032543175
WST-21-0651153-5240045295454350032533175

Caribou Zone
Mineralization most commonly occurs in gold-bearing pyrite stockworks as well as semi-massive pyrite replacement zones associated with phyllic alteration (sericite-pyrite ± silica) with sulphides, pyrite dominated with minor chalcopyrite and sphalerite ranging from trace to up to 20%, and local visible gold. Mineralization is hosted in rhyolites or mafic-intermediate volcanics frequently at or near faults or the contact with felsic porphyritic intrusions.

Zone 27
Mineralization most commonly occurs as replacement-type characterized by 5% to 50% disseminated, stringer, semi-massive or stockwork pyrite, ptygmatic tourmaline veins, quartz-tourmaline crustiform veins, local quartz-carbonate veins, and local visible gold. Mineralization is associated with moderate to strong sericite, weak to strong silica, weak chlorite and carbonate and locally weak fuchsite and is hosted in strongly altered andesites, in or at the contact of the rhyolite, or along the contacts with felsic porphyritic intrusions.

F-Zones
Mineralization is hosted in sheared andesites with carbonate replacement or quartz veining and occurs as quartz ± ankerite veinlets or as replacement type in shear zones and is characterised by trace to 10% pyrite with local visible gold. Alteration is dominated by sericite-fuchsite-tourmaline-pyrite.

Bobcat
Mineralization most commonly occurs in gold-bearing quartz-pyrite veins controlled by northeast trending faults and shears and to a lesser extent in minor crustiform quartz-tourmaline-ankerite-pyrite veins and pyrite replacement zones and stockwork. Mineralization is hosted in sheared mafic volcanics, rhyolites near faults, or at the contact with felsic porphyritic intrusions.

Underdog
Mineralization most commonly occurs in gold-bearing quartz-pyrite (± tourmaline) veins and as disseminated, stringer, semi-massive to massive pyrite with minor sphalerite, chalcopyrite and molybdenite associated with strong sericite and silica alteration. Mineralization is hosted along the intrusive contacts of a three-phase composite felsic porphyritic unit which cross-cuts felsic and mafic volcanic sequences.

Qualified Person
The scientific and technical content of this news release has been reviewed, prepared and approved by Mr. Louis Grenier, M.Sc.A., P.Geo. (OGQ 800), Director of Exploration for Osisko's Windfall gold project, who is a "qualified person" as defined by National Instrument 43-101 – Standards of Disclosure for Mineral Projects ("NI 43-101").

Quality Control and Reporting Protocols
True width determination is estimated at 55-80% of the reported core length interval for the zone. Assays are uncut except where indicated. Intercepts occur within geological confines of major zones but have not been correlated to individual vein domains at this time. Reported intervals include minimum weighted averages of 3.0 g/t Au diluted over core lengths of at least 2.0 metres. NQ core assays were obtained by either 1-kilogram screen fire assay or standard 50-gram fire-assaying-AA finish or gravimetric finish at (i) ALS Laboratories in Val d'Or, Québec, Vancouver, British Colombia, Lima, Peru or Vientiane, Laos (ii) Bureau Veritas in Timmins, Ontario. The 1-kilogram screen assay method is selected by the geologist when samples contain coarse gold or present a higher percentage of pyrite than surrounding intervals. Selected samples are also analyzed for multi-elements, including silver, using a Four Acid Digestion-ICP-MS method at ALS Laboratories. Drill program design, Quality Assurance/Quality Control ("QA/QC") and interpretation of results is performed by qualified persons employing a QA/QC program consistent with NI 43-101 and industry best practices. Standards and blanks are included with every 20 samples for QA/QC purposes by the Corporation as well as the lab. Approximately 5% of sample pulps are sent to secondary laboratories for check assay.

About the Windfall Gold Deposit
The Windfall gold deposit is located between Val-d'Or and Chibougamau in the Abitibi region of Québec, Canada. The Mineral Resource Estimate (MRE) defined by Osisko, as disclosed in the news release dated February 17, 2021 is supported by the technical report entitled “Preliminary Economic Assessment Update for the Windfall Project” dated April 26, 2021 (that includes Windfall Mineral Resource Estimate with an effective date  of November 30, 2020), and assuming a cut-off grade of 3.50 g/t Au, comprises 521,000 tonnes at 11.3 g/t Au (189,000 ounces) in the measured mineral resource category, 5,502,000 tonnes at 9.4 g/t Au (1,668,000 ounces) in the indicated mineral resource category and 16,401,000 tonnes at 8.0 g/t Au (4,244,000 ounces) in the inferred mineral resource category. The key assumptions, parameters and methods used to estimate the mineral resource estimate disclosed in the February 17, 2021 news release are further described in the full technical report prepared by BBA Inc. in accordance with NI 43-101 and is available on SEDAR (www.sedar.com) under the Corporation's issuer profile. The Windfall gold deposit is currently one of the highest-grade resource-stage gold projects in Canada and has world-class scale. Mineralization occurs in three principal zones: Lynx, Main Zone, and Underdog. Mineralization is generally comprised of sub-vertical zones following intrusive porphyry contacts plunging to the northeast. The resources are defined from surface to a depth of 1,600 metres as it now includes the Triple 8 (T8) zone. The resources excluding T8 are defined from surface to a depth of 1,200 metres. The deposit remains open along strike and at depth. Mineralization has been identified at surface in some areas and as deep as 2,625 metres in others with significant potential to extend mineralization down-plunge and at depth.

About Osisko Mining Inc.
Osisko is a mineral exploration company focused on the acquisition, exploration, and development of gold resource properties in Canada. Osisko holds a 100% interest in the high-grade Windfall gold deposit located between Val-d'Or and Chibougamau in Québec and holds a 100% undivided interest in a large area of claims in the surrounding Urban Barry area and nearby Quévillon area (over 2,700 square kilometres).

Cautionary Note Regarding Forward-Looking Information
This news release contains "forward-looking information" within the meaning of the applicable Canadian securities legislation that is based on expectations, estimates, projections and interpretations as at the date of this news release. Any statement that involves predictions, expectations, interpretations, beliefs, plans, projections, objectives, assumptions, future events or performance (often, but not always, using phrases such as "expects", or "does not expect", "is expected", "interpreted", "management's view", "anticipates" or "does not anticipate", "plans", "budget", "scheduled", "forecasts", "estimates", "potential", "feasibility", "believes" or "intends" or variations of such words and phrases or stating that certain actions, events or results "may" or "could", "would", "might" or "will" be taken to occur or be achieved) are not statements of historical fact and may be forward-looking information and are intended to identify forward-looking information. This news release contains the forward-looking information pertaining to, among other things: the Windfall gold deposit being one of the highest-grade resource-stage gold projects in Canada and having world-class scale; the key assumptions, parameters and methods used to estimate the mineral resource estimate disclosed in this news release; the prospects, if any, of the Windfall gold deposit; timing and ability of Osisko to file a technical report for the mineral resource estimate disclosed in this news release; the timing and ability of Osisko, if at all, to publish a feasibility study for the Windfall gold deposit; the amount and type of drilling to be completed and the timing to complete such drilling; the focus of the remaining infill drilling; the trend of grade increase; the Lynx zone remaining open to expansion down plunge; upgrading a inferred mineral resource to a measured mineral resource or indicated mineral resource category; future drilling at the Windfall gold deposit; the significance of historic exploration activities and results. Such factors include, among others, risks relating to the ability of exploration activities (including drill results) to accurately predict mineralization; errors in management's geological modelling; the ability of Osisko to complete further exploration activities, including (infill) drilling; property and royalty interests in the Windfall gold deposit; the ability of the Corporation to obtain required approvals; the results of exploration activities; risks relating to mining activities; the global economic climate; metal prices; dilution; environmental risks; and community and non-governmental actions. Although the forward-looking information contained in this news release is based upon what management believes, or believed at the time, to be reasonable assumptions, Osisko cannot assure shareholders and prospective purchasers of securities of the Corporation that actual results will be consistent with such forward-looking information, as there may be other factors that cause results not to be as anticipated, estimated or intended, and neither Osisko nor any other person assumes responsibility for the accuracy and completeness of any such forward-looking information. Osisko does not undertake, and assumes no obligation, to update or revise any such forward-looking statements or forward-looking information contained herein to reflect new events or circumstances, except as may be required by law.

CONTACT INFORMATION:
John Burzynski
Chief Executive Officer
Telephone (416) 363-8653