Osisko Infill Drilling Returns High Grade at Lynx

106 g/t Au Over 2.4 Metres

TORONTO, April 20, 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 41 intercepts in 17 drill holes (4 from surface, 13 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).

Osisko Chief Executive Officer John Burzynski commented: “Infill drilling in Lynx and Triple Lynx continues to nicely intersect the inferred blocks from the February 2021 MRE, as expected, and increase our confidence in converting those blocks into the indicated or measured categories. We are currently drilling over 5,000 metres a week at Windfall, on target to complete the infill program by this fall.”

Selected high-grade intercepts include: 106 g/t Au over 2.4 metres in WST-21-0746; 90.4 g/t Au over 2.1 metres in OSK-W-21-2416-W3; 28.3 g/t Au over 4.9 metres in WST-21-0690, 60.9 g/t Au over 2.2 metres in OSK-W-21-2452, and 63.5 g/t Au over 2.0 metres in OSK-W-21-2416-W1. Maps showing hole locations and full analytical results are available at www.osiskomining.com.

Infill Drilling

Hole Number	From (m)	To (m)	Interval (m)	Au (g/t) uncut	Au (g/t) cut to 100 g/t	Zone	Corridor
OSK-W-20-2363-W3	659.2	662.0	2.8	3.76		TLX_3178	Triple Lynx
OSK-W-21-2252-W12	916.0	918.0	2.0	15.4		TLX_3161	Triple Lynx
	921.0	923.4	2.4	7.13		TLX_3161	Triple Lynx
including	921.0	921.4	0.4	27.6
	932.4	937.0	4.6	6.60		TLX_3161	Triple Lynx
including	932.4	932.8	0.4	17.3
and	936.0	937.0	1.0	15.9
	971.0	974.0	3.0	12.2		TLX_3163	Triple Lynx
including	973.3	974.0	0.7	39.0
	998.0	1000.0	2.0	3.91		TLX_3163	Triple Lynx
	1024.9	1027.2	2.3	29.2	13.4	TLX_3164	Triple Lynx
including	1024.9	1025.2	0.3	221	100
OSK-W-21-2394-W4	874.8	877.0	2.2	14.3		TLX_3130	Triple Lynx
including	874.8	875.1	0.3	30.0
OSK-W-21-2416-W1	910.0	912.0	2.0	5.18		TLX_3161	Triple Lynx
	969.1	971.1	2.0	6.02		TLX_3164	Triple Lynx
including	970.7	971.1	0.4	28.9
	974.0	976.0	2.0	63.5	25.5	TLX_3164	Triple Lynx
including	975.5	976.0	0.5	252	100
OSK-W-21-2416-W2	965.4	967.4	2.0	8.32		TLX_3163	Triple Lynx
including	965.4	966.5	1.1	14.7
	976.0	978.0	2.0	6.19		TLX_3163	Triple Lynx
	982.8	985.0	2.2	10.3		TLX_3164	Triple Lynx
	1006.1	1009.2	3.1	10.4		TLX_3164	Triple Lynx
including	1008.7	1009.2	0.5	46.9
	1050.0	1053.0	3.0	9.79		TLX_3170	Triple Lynx
including	1052.0	1053.0	1.0	17.0
OSK-W-21-2416-W3	924.5	926.6	2.1	7.06		TLX_3161	Triple Lynx
	934.5	938.4	3.9	8.78		TLX_3161	Triple Lynx
	1024.0	1029.0	5.0	11.2		TLX_3162	Triple Lynx
including	1024.0	1024.3	0.3	57.9
and	1026.0	1027.0	1.0	28.0
	1047.8	1049.9	2.1	90.4	36.3	TLX_3170	Triple Lynx
including	1047.8	1048.2	0.4	384	100
	1069.0	1071.5	2.5	4.82		TLX_3172	Triple Lynx
including	1070.8	1071.5	0.7	11.2
	1080.0	1082.0	2.0	36.4		TLX_3172	Triple Lynx
OSK-W-21-2452	829.7	831.9	2.2	60.9	30.6	TLX_3195	Triple Lynx
including	831.0	831.6	0.6	211	100
OSK-W-21-2459	883.4	885.6	2.2	5.68		TLX_3184	Triple Lynx
including	883.4	884.1	0.7	13.8
OSK-W-21-2493	559.2	561.5	2.3	19.8		TLX_3184	Triple Lynx
including	560.8	561.1	0.3	72.6
OSK-W-21-2495	633.3	635.8	2.5	3.99		LXM_3304	Lynx
including	633.3	633.8	0.5	18.2
WST-20-0481	111.5	113.5	2.0	12.3		LXM_3304	Lynx
including	113.0	113.5	0.5	45.1
	115.0	117.0	2.0	5.29		LXM_3304	Lynx
including	116.6	117.0	0.4	10.8
WST-20-0605A	265.0	267.3	2.3	28.6		LXSW_3500	Lynx SW
including	266.4	267.0	0.6	86.9
WST-21-0619A	214.0	216.0	2.0	20.0		TLX_3161	Triple Lynx
including	214.0	214.4	0.4	96.4
WST-21-0674	168.7	171.1	2.4	26.9		LXM_3304	Lynx
including	169.1	169.6	0.5	94.1
WST-21-0689A	316.7	318.7	2.0	31.2	29.3	TLX_3169	Triple Lynx
including	317.6	317.9	0.3	89.0
and	318.4	318.7	0.3	113	100
WST-21-0690	231.0	235.9	4.9	28.3		TLX_3161	Triple Lynx
including	231.6	232.2	0.6	86.7
and	234.4	235.0	0.6	72.1
WST-21-0691	218.4	222.0	3.6	20.4		TLX_3161	Triple Lynx
including	219.4	220.0	0.6	65.4
WST-21-0696	448.8	451.0	2.2	5.06		LX4_3450	Lynx 4
WST-21-0701	126.0	128.0	2.0	27.9		LXM_3304	Lynx
including	126.5	127.3	0.8	69.8
	142.5	144.8	2.3	17.3		LXM_3359	Lynx
including	143.5	144.5	1.0	39.5
WST-21-0702	121.9	124.2	2.3	24.7		LXM_3304	Lynx
WST-21-0740	122.0	124.8	2.8	3.58		LXM_3304	Lynx
including	123.0	123.4	0.4	18.7
WST-21-0745	184.5	187.0	2.5	31.1		LXM_3304	Lynx
including	185.7	186.1	0.4	85.6
WST-21-0746	190.5	192.9	2.4	106	66.8	LXM_3304	Lynx
including	190.5	191.0	0.5	109	100
and	191.0	191.5	0.5	152	100
and	191.5	192.1	0.6	207	100

Notes: True widths are estimated at 55 – 80% of the reported core length interval. See "Quality Control and Reporting Protocols" below. LXM = Lynx Main, LX4 = Lynx 4, TLX = Triple Lynx and LXSW = Lynx Southwest.

Drill hole location

Hole Number	Azimuth (°)	Dip (°)	Length (m)	UTM E	UTM N	Elevation	Section
OSK-W-20-2363-W3	139	-52	1185	452930	5435548	419	3425
OSK-W-21-2252-W12	129	-54	1161	453241	5435694	415	3750
OSK-W-21-2394-W4	138	-52	920	452923	5435467	414	3375
OSK-W-21-2416-W1	123	-54	1083	453169	5435624	412	3650
OSK-W-21-2416-W2	123	-54	1266	453169	5435624	412	3650
OSK-W-21-2416-W3	123	-54	1128	453169	5435624	412	3650
OSK-W-21-2445-W3	141	-50	753	452906	5435434	415	3325
OSK-W-21-2452	137	-56	891	453008	5435388	412	3400
OSK-W-21-2459	132	-52	1227	452997	5435607	425	3500
OSK-W-21-2493	134	-54	1080	453008	5435388	412	3400
OSK-W-21-2495	123	-54	1257	453426	5435565	410	3850
WST-20-0481	154	1	179	453450	5435264	116	3725
WST-20-0605A	148	-61	532	453105	5435065	231	3325
WST-21-0619A	174	-61	249	453507	5435327	-7	3800
WST-21-0672	141	-44	327	453508	5435327	-7	3800
WST-21-0674	134	-46	261	453508	5435327	-7	3800
WST-21-0689A	161	-64	397	453356	5435272	16	3650
WST-21-0690	150	-63	307	453356	5435272	16	3650
WST-21-0691	152	-58	385	453356	5435272	16	3650
WST-21-0696	137	-49	492	453229	5435127	134	3475
WST-21-0701	148	-22	172	453356	5435272	17	3650
WST-21-0702	151	-14	166	453356	5435272	17	3650
WST-21-0740	168	-25	150	453507	5435326	-6	3800
WST-21-0745	130	-51	246	453508	5435327	-7	3800
WST-21-0746	117	-44	240	453508	5435327	7	3800

Lynx Zone
Mineralization occurs as grey to translucent quartz-carbonate-pyrite-tourmaline veins and pyrite replacement zones and stockworks. Vein-type mineralization is associated with haloes of pervasive sericite-pyrite ± silica alteration and contain sulphides (predominantly pyrite with minor amounts of chalcopyrite, sphalerite, galena, arsenopyrite, and pyrrhotite) and local visible gold. Replacement mineralization is associated with strong pervasive silica-sericite-ankerite ± tourmaline alteration and contains disseminated pyrite from trace to 80% with local visible gold. Pyrite stockworks can form envelopes that reach several tens of metres thick. Fuchsite alteration is common and is spatially constrained to near the gabbros. Mineralization occurs at or near geological contacts between felsic porphyritic or fragmental intrusions and the host rhyolites or gabbros and locally can be hosted along the gabbro-rhyolite contact.

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 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