Osisko Drilling at Windfall Returns Near Surface High-Grade

877 g/t Au Over 2.2 Metres, 85.0 g/t Au Over 2.0 Metres in Bobcat

TORONTO, April 13, 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 43 intercepts in 18 drill holes (13 from surface, 5 from underground) and 6 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 mineral resource estimate (“MRE”) 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: “All zones at Windfall continue to expand and infill nicely with respect to the February 2021 MRE blocks, and continue to highlight the potential to increase the strong base case economics from the Windfall PEA, released last week.”

Selected high-grade intercepts include:

877 g/t Au over 2.2 metres

and

85.0 g/t Au over 2.0 metres

in WST-21-0668;

72.2


g/t


Au over 2.0 metres

in OSK-W-21-2442;

53.3 g/t Au over 2.3 metres

in WST-21-0600; and

50.5 g/t Au over 2.4 metres

in OSK-W-21-2442-W1. Maps showing hole locations and full analytical results are available at


www.osiskomining.com



Infill Drilling


Hole No.

From (m)

To (m)

Interval (m)

Au (g/t) uncut

Au (g/t)


cut to 100 g/t

Zone

Corridor

OSK-W-20-2423

938.0

940.0

2.0

4.71


Underdog_4102


Underdog


including
939.5 940.0 0.5 16.6

OSK-W-21-2442

627.0

629.0

2.0

17.4


Underdog_4100


Underdog


including
628.0 629.0 1.0 34.5

632.0

634.0

2.0

14.3


Underdog_4100


Underdog


including
632.4 633.0 0.6 36.7

642.0

644.0

2.0

24.7


Underdog_4100


Underdog


including
643.0 644.0 1.0 48.3

659.0

661.0

2.0

5.31


Underdog_4102


Underdog


including
659.0 659.5 0.5 12.9

667.0

669.0

2.0

72.2

57.5

Underdog_4102


Underdog


including
667.0 668.0 1.0 130 100

686.0

688.0

2.0

17.6


Underdog_4104


Underdog


including
686.0 687.0 1.0 34.3

826.0

828.0

2.0

35.9

30.0

Underdog_4905


Underdog


including
826.8 827.4 0.6 120 100

OSK-W-21-2442-W1

696.0

698.0

2.0

3.48


Underdog_4104


Underdog


including
696.7 697.1 0.4 11.2

747.6

750.0

2.4

50.5

41.7

Underdog_4106


Underdog


including
749.0 750.0 1.0 121 100

762.6

764.8

2.2

5.02


Underdog_4107


Underdog


including
762.6 762.9 0.3 34.8

854.6

857.0

2.4

5.10


Underdog_4905

Underdog

OSK-W-21-2455

697.0

699.0

2.0

20.4


Caribou_2220


Caribou


including
698.0 699.0 1.0 40.5

OSK-W-21-2463

629.0

631.0

2.0

7.21


Caribou_2206

Caribou

OSK-W-21-2483

521.0

526.5

5.5

3.94


Caribou_2210


Caribou


including
521.0 522.0 1.0 11.2

547.0

549.3

2.3

11.2


Caribou_2215


Caribou


including
548.4 549.0 0.6 29.4

WST-21-0600

160.0

162.3

2.3

53.3


Bobcat_2350


Bobcat


including
160.0 161.0 1.0 86.3

WST-21-0668

36.5

38.7

2.2

877

19.1

Bobcat_2350


Bobcat


including
36.5 36.9 0.4 4820 100

WST-21-0669

74.0

76.0

2.0

11.5


Bobcat_2354

Bobcat

Notes: True widths are estimated at 55 – 80% of the reported core length interval. See

“Quality Control and Reporting Protocols”

below.



Expansion Drilling


Hole No.

From (m)

To (m)

Interval (m)

Au (g/t) uncut

Au (g/t)


cut to 100 g/t

Zone

Corridor

OSK-W-20-2374

102.3

104.4

2.1

3.16


Bobcat


Bobcat


including
103.9 104.4 0.5 7.98

OSK-W-20-2388

172.6

174.7

2.1

4.32


Caribou

Caribou

OSK-W-20-2399-W2

405.0

407.1

2.1

6.93


Caribou

Caribou

OSK-W-20-2405-W1

489.3

491.5

2.2

3.45


Caribou


Caribou


including
490.9 491.5 0.6 9.86

OSK-W-20-2410-W2

430.6

433.9

3.3

3.80


Caribou


Caribou


including
433.6 433.9 0.3 14.6

OSK-W-20-2415

467.0

469.0

2.0

4.57


Caribou

Caribou

OSK-W-20-2425

181.2

184.1

2.9

3.65


Caribou

Caribou

190.1

192.2

2.1

6.18


Caribou

Caribou

OSK-W-20-2430

70.8

73.0

2.2

5.59


F11

F11

OSK-W-20-2433

116.0

118.2

2.2

5.85


F11

F11

OSK-W-21-2442

916.3

918.4

2.1

3.51


Underdog


Underdog


including
916.6 917.3 0.7 9.39

934.0

937.3

3.3

7.33


Underdog_4501


Underdog


including
935.0 935.5 0.5 18.3

OSK-W-21-2442-W1

661.2

664.0

2.8

3.57


Underdog

Underdog

666.0

668.0

2.0

3.39


Underdog

Underdog

OSK-W-21-2460-W1

759.0

761.0

2.0

4.39


Z27

Zone 27

OSK-W-21-2462-W1

655.0

657.0

2.0

6.97


Caribou

Caribou

682.0

684.0

2.0

4.37


Caribou

Caribou

OSK-W-21-2476

572.6

574.8

2.2

10.7


Caribou

Caribou

OSK-W-21-2490

712.0

714.0

2.0

4.35


Caribou

Caribou

732.0

734.3

2.3

8.52


Caribou


Caribou


including
732.7 733.5 0.8 18.0

WST-20-0480B

138.1

140.8

2.7

25.3


Z27


Zone 27


including
139.0 140.0 1.0 53.5

WST-20-0559A

118.0

120.3

2.3

3.68


Bobcat

Bobcat

WST-21-0668

95.0

97.0

2.0

85.0

20.0

Bobcat


Bobcat


including
95.8 96.2 0.4 425 100

WST-21-0669

64.9

66.9

2.0

4.36


Bobcat

Bobcat

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 Number

Azimuth (°)

Dip (°)

Length (m)

UTM E

UTM N

Elevation

Section

OSK-W-20-2374
340 -52 138 452720 5434747 397 2850

OSK-W-20-2388
326 -61 699 452715 5434606 397 2775

OSK-W-20-2399-W2
333 -54 876 452875 5434553 398 2875

OSK-W-20-2405-W1
332 -58 716 452694 5434440 401 2675

OSK-W-20-2410-W2
338 -62 774 452727 5434358 402 2650

OSK-W-20-2415
328 -54 755 452739 5434475 401 2725

OSK-W-20-2423
332 -60 1326 452616 5434449 403 2600

OSK-W-20-2425
336 -60 747 452715 5434606 397 2775

OSK-W-20-2430
150 -45 360 452601 5436048 404 3375

OSK-W-20-2433
148 -47 411 452559 5436072 405 3350

OSK-W-21-2442
347 -53 1053 452315 5434419 399 2325

OSK-W-21-2442-W1
347 -53 1011 452315 5434419 399 2325

OSK-W-21-2455
328 -53 780 452738 5434476 401 2725

OSK-W-21-2460-W1
332 -55 795 452732 5434536 399 2750

OSK-W-21-2462-W1
338 -57 855 452875 5434553 398 2875

OSK-W-21-2463
339 -65 1335 452616 5434449 403 2600

OSK-W-21-2476
337 -58 879 452840 5434569 398 2850

OSK-W-21-2483
328 -58 756 452731 5434634 397 2800

OSK-W-21-2490
338 -61 786 452756 5434465 401 2725

WST-20-0480B
143 -51 382 452281 5434975 262 2575

WST-20-0559A
143 3 145 452955 5435003 254 3175

WST-21-0600
97 -20 172 452819 5434944 274 3025

WST-21-0668
142 -20 148 452817 5434943 274 3025

WST-21-0669
140 -4 142 452817 5434944 274 3025


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-Zone


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 defined by Osisko, as disclosed in the news release dated February 17, 2021 and


supported by the technical report entitled “Mineral Resource Estimate Update for the Windfall Project, Eeyou Istchee James Bay, Québec, Canada” dated March 8, 2021 (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 r


esources 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.


T


he 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



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