Osisko Step-out Drilling Expands High Grade at Windfall

Including 391 g/t Au Over 2.4 Metres in Triple Lynx

TORONTO, Oct. 07, 2020 (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.

Drilling is currently focused on the Lynx deposit. Osisko Chief Executive Officer John Burzynski commented: “Windfall continues to grow in scale with impressive results flowing in from the Lynx deposit. Today’s new intersections are all from outside the published resource area and include 15 intercepts with uncut average grades of over one oz/t. The ongoing expansion drilling continues to show the incredible upside growth potential of our deposit.”

The table below shows intercepts located outside the February 2020 mineral resource estimate wireframes (see Osisko news release dated February 19, 2020). These intercepts either expand the resource wireframes or are located in a defined zone/corridor but not yet correlated to a specific wireframe. Significant new analytical results are presented below and include 110 intercepts in 43 drill holes and 24 wedges.

Selected high-grade intercepts from the new results include: 391 g/t Au over 2.4 metres, 70 metres toward surface from wireframe Lynx_361, in OSK-W-20-2133-W2; 142 g/t Au over 2.3 metres in OSK-W-20-2307; 86.0 g/t Au over 2.1 metres in WST-20-0341A; 73.8 g/t Au over 2.0 metres in WST-20-0470; 54.4 g/t Au over 4.8 metres in OSK-W-20-2252-W2; and 49.8 g/t Au over 2.2 metres in OSK-W-20-2292. Maps showing hole locations and full analytical results are available at www.osiskomining.com

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-17-1258	971.7	973.7	2.0	3.33		Lynx 4	Lynx
including	971.7	972.7	1.0	6.56
OSK-W-18-1727	782.9	784.9	2.0	12.7		Lynx	Lynx
OSK-W-19-1857-W11	1301.8	1304.6	2.8	7.39		Lynx 4	Lynx
OSK-W-19-2100-W4	1212.5	1214.7	2.2	5.22		Triple Lynx	Triple Lynx
	1242.0	1244.0	2.0	6.47		Triple Lynx	Triple Lynx
OSK-W-19-2101	664.4	667.0	2.6	5.48		Triple Lynx	Triple Lynx
OSK-W-20-2133-W2	783.6	786.0	2.4	391	31.1	Lynx_361	Triple Lynx
including	784.2	784.6	0.4	2260	100
OSK-W-20-2139-W7	1081.0	1083.5	2.5	9.53		Triple Lynx	Triple Lynx
including	1081.0	1081.9	0.9	26.1
OSK-W-20-2139-W8	543.0	545.0	2.0	6.68		Triple Lynx	Triple Lynx
including	543.5	544.4	0.9	14.5
OSK-W-20-2139-W10	1196.0	1198.0	2.0	11.7		Triple Lynx	Triple Lynx
including	1196.0	1197.1	1.1	21.3
OSK-W-19-2169	893.9	895.9	2.0	5.59		Lynx 4	Lynx
including	894.7	895.3	0.6	18.2
	1256.3	1258.4	2.1	15.8		Lynx 4	Lynx
including	1257.5	1258.4	0.9	36.2
OSK-W-20-2170-W6	1384.0	1386.4	2.4	6.70		Lynx 4	Lynx
OSK-W-19-2173	29.0	31.0	2.0	3.07		F11	F11
OSK-W-19-2177	200.0	202.0	2.0	3.10		F11	F11
OSK-W-20-2197-W2	768.7	771.4	2.7	10.3		Lynx_361	Triple Lynx
including	769.7	770.7	1.0	26.0
	1045.0	1047.0	2.0	5.66		Lynx 4	Lynx
OSK-W-20-2217-W2	860.0	862.0	2.0	14.0		Triple Lynx	Triple Lynx
including	860.0	860.5	0.5	55.6
OSK-W-20-2217-W3	830.0	832.3	2.3	7.53		Lynx_363	Triple Lynx
including	831.0	831.4	0.4	26.8
	1111.7	1114.0	2.3	16.4		Triple Lynx	Triple Lynx
including	1113.5	1114.0	0.5	66.3
OSK-W-20-2249	730.0	732.0	2.0	5.66		Lynx SW	Lynx
including	730.5	730.9	0.4	22.8
OSK-W-20-2250	1002.2	1005.0	2.8	18.1	15.6	Triple Lynx	Triple Lynx
including	1002.2	1002.5	0.3	123	100
OSK-W-20-2250-W1	1009.0	1011.1	2.1	5.08		Triple Lynx	Triple Lynx
OSK-W-20-2250-W2	1024.7	1028.0	3.3	28.8		Triple Lynx	Triple Lynx
including	1026.4	1027.0	0.6	63.0
OSK-W-20-2250-W3	714.0	716.5	2.5	14.7		Triple Lynx	Triple Lynx
OSK-W-20-2250-W4	727.7	734.5	6.8	4.58		Triple Lynx	Triple Lynx
including	727.7	728.4	0.7	10.3
and	730.5	731.0	0.5	12.0
	855.4	858.0	2.6	6.29		Triple Lynx	Triple Lynx
including	857.2	858.0	0.8	18.6
OSK-W-20-2252-W2	812.0	814.0	2.0	7.64		Triple Lynx	Triple Lynx
	817.2	822.0	4.8	54.4	10.4	Triple Lynx	Triple Lynx
including	817.2	817.5	0.3	804	100
OSK-W-20-2252-W3	824.3	829.7	5.4	3.58		Triple Lynx	Triple Lynx
	845.1	847.1	2.0	4.01		Triple Lynx	Triple Lynx
OSK-W-20-2253	387.5	389.5	2.0	4.30		Caribou Corridor	Caribou
OSK-W-20-2256	870.0	872.8	2.8	9.81		Triple Lynx	Triple Lynx
OSK-W-20-2256-W2	815.0	817.0	2.0	3.17		Triple Lynx	Triple Lynx
OSK-W-20-2260-W2	1091.0	1093.0	2.0	6.47		Triple Lynx	Triple Lynx
including	1091.4	1092.1	0.7	18.1
	1174.4	1176.5	2.1	9.43		Triple Lynx	Triple Lynx
including	1176.0	1176.5	0.5	28.0
OSK-W-20-2263	94.0	96.0	2.0	8.58		Bobcat	Bobcat
including	94.0	95.0	1.0	16.9
	106.7	108.8	2.1	6.12		Bobcat	Bobcat
including	108.0	108.8	0.8	14.1
	710.0	712.0	2.0	42.6	21.4	Lynx SW	Lynx
including	711.2	711.6	0.4	206	100
OSK-W-20-2266	1027.4	1029.5	2.1	5.58		Triple Lynx	Triple Lynx
including	1028.7	1029.0	0.3	33.1
OSK-W-20-2266-W1	776.8	779.2	2.4	5.73		Triple Lynx	Triple Lynx
including	778.0	779.2	1.2	11.1
	797.3	799.3	2.0	3.08		Lynx_364	Triple Lynx
OSK-W-20-2266-W2	717.4	719.4	2.0	19.9		Lynx_363	Triple Lynx
OSK-W-20-2267	50.4	52.8	2.4	15.4		Bobcat	Bobcat
including	51.0	51.5	0.5	46.4
OSK-W-20-2268-W1	737.1	739.3	2.2	7.46		Triple Lynx	Triple Lynx
including	738.3	739.0	0.7	19.0
	819.0	821.3	2.3	27.4		Triple Lynx	Triple Lynx
including	819.0	820.0	1.0	45.7
	1027.0	1029.0	2.0	6.70		Triple Lynx	Triple Lynx
including	1027.4	1028.2	0.8	16.5
OSK-W-20-2268-W2	999.0	1001.0	2.0	5.08		Triple Lynx	Triple Lynx
OSK-W-20-2269	97.3	99.5	2.2	8.21		Bobcat	Bobcat
including	98.0	98.4	0.4	30.8
	518.2	520.6	2.4	3.37		Lynx SW	Lynx
	886.0	888.0	2.0	14.0		Lynx SW	Lynx
including	886.5	886.8	0.3	92.5
OSK-W-20-2271	809.6	815.2	5.6	6.69		Lynx	Lynx
including	814.2	815.2	1.0	17.4
	841.1	843.1	2.0	18.2		Lynx	Lynx
including	842.1	843.1	1.0	35.0
	877.0	879.0	2.0	5.36		Lynx	Lynx
including	877.9	878.2	0.3	27.8
OSK-W-20-2272	683.0	685.1	2.1	13.0		Triple Lynx	Triple Lynx
including	683.0	683.9	0.9	29.7
OSK-W-20-2273	706.7	708.7	2.0	8.32		Lynx_363	Triple Lynx
including	706.7	707.2	0.5	22.4
	1013.8	1017.3	3.5	4.78		Triple Lynx	Triple Lynx
including	1015.1	1015.5	0.4	16.1
OSK-W-20-2280	1013.2	1016.7	3.5	5.23		Triple Lynx	Triple Lynx
including	1013.8	1014.2	0.4	26.7
and	1016.4	1016.7	0.3	11.3
	1084.7	1087.0	2.3	4.27		Triple Lynx	Triple Lynx
OSK-W-20-2280-W1	1090.0	1092.0	2.0	11.8		Triple Lynx	Triple Lynx
OSK-W-20-2282	308.4	310.8	2.4	6.13		Bobcat	Bobcat
including	309.0	309.5	0.5	16.6
OSK-W-20-2283	808.0	813.4	5.4	33.5	29.0	Triple Lynx	Triple Lynx
including	810.8	811.3	0.5	73.1
and	811.7	812.0	0.3	182	100
	819.0	821.0	2.0	7.27		Triple Lynx	Triple Lynx
including	819.6	820.0	0.4	24.1
	823.2	825.5	2.3	4.30		Triple Lynx	Triple Lynx
including	823.6	824.4	0.8	10.6
	1001.0	1003.2	2.2	44.8	23.6	Triple Lynx	Triple Lynx
including	1002.7	1003.2	0.5	194	100
	1018.0	1020.0	2.0	19.3		Triple Lynx	Triple Lynx
including	1018.9	1019.5	0.6	54.4
OSK-W-20-2288	467.0	469.8	2.8	8.13		Lynx SW	Lynx
including	467.0	467.4	0.4	38.9
OSK-W-20-2292	390.0	392.0	2.0	7.18		Lynx	Lynx
including	391.7	392.0	0.3	19.3
	835.4	837.8	2.4	4.47		Triple Lynx	Triple Lynx
	845.0	847.0	2.0	11.8		Lynx_361	Triple Lynx
including	845.8	846.3	0.5	41.0
	882.0	884.0	2.0	8.01		Lynx_364	Triple Lynx
including	883.0	884.0	1.0	15.7
	1007.2	1009.2	2.0	49.8	21	Lynx_372	Triple Lynx
including	1008.8	1009.2	0.4	244	100
OSK-W-20-2295	651.2	658.0	6.8	12.4		Triple Lynx	Triple Lynx
including	652.4	652.7	0.3	28.7
and	653.4	654.0	0.6	45.9
and	656.1	656.7	0.6	56.9
	891.7	893.7	2.0	11.6		Lynx SW	Triple Lynx
including	891.7	892.7	1.0	23.0
OSK-W-20-2295-W1	648.6	651.4	2.8	45.1	30.1	Triple Lynx	Triple Lynx
including	650.0	650.7	0.7	160	100
OSK-W-20-2298	169.0	171.7	2.7	7.41		Bobcat	Bobcat
including	169.0	169.7	0.7	20.2
	245.0	247.0	2.0	6.59		Bobcat	Bobcat
including	245.0	245.7	0.7	18.4
	373.0	375.0	2.0	16.7		Lynx SW	Lynx
including	373.8	374.3	0.5	65.2
OSK-W-20-2305	630.8	635.0	4.2	4.47		Triple Lynx	Triple Lynx
including	634.0	635.0	1.0	9.32
	876.0	878.3	2.3	10.7		Triple Lynx	Triple Lynx
including	877.6	878.3	0.7	31.6
	882.2	884.6	2.4	43.0	18.0	Triple Lynx	Triple Lynx
including	883.4	883.8	0.4	250	100
OSK-W-20-2306	137.8	140.0	2.2	4.30		Bobcat	Bobcat
	147.1	149.4	2.3	3.12		Bobcat	Bobcat
	275.0	277.3	2.3	8.58		Bobcat	Bobcat
including	275.8	276.5	0.7	20.7
	386.1	388.3	2.2	3.94		Lynx SW	Lynx
including	386.6	387.0	0.4	11.5
OSK-W-20-2307	689.6	691.9	2.3	142	75.8	Lynx_341	Lynx
including	690.0	690.4	0.4	413	100
OSK-W-20-2310	69.7	72.0	2.3	35.6	13.8	Mallard_5200	Mallard
including	70.8	71.1	0.3	267	100
OSK-W-20-2312	85.0	87.3	2.3	7.19		Mallard	Mallard
including	85.7	86.2	0.5	25.4
OSK-W-20-2324	90.0	92.5	2.5	8.43		Mallard	Mallard
WST-20-0135	293.0	295.1	2.1	35.1	19.2	Lynx SW	Lynx
including	293.7	294.1	0.4	184	100
	351.8	354.7	2.9	3.15		Lynx SW	Lynx
including	351.8	352.3	0.5	8.55
and	354.1	354.7	0.6	7.76
	360.4	362.6	2.2	13.4		Triple Lynx	Triple Lynx
including	360.4	361.4	1.0	28.9
	397.3	399.4	2.1	23.6	14.5	Lynx SW	Lynx
including	397.8	398.1	0.3	164	100
WST-20-0318	377.4	379.6	2.2	8.05		Lynx SW	Lynx
	463.3	466.0	2.7	9.06		Lynx 4	Lynx
WST-20-0339	199.1	202.2	3.1	4.57		Lynx HW	Lynx
WST-20-0341A	306.1	308.2	2.1	86.0	19.9	Lynx SW	Lynx
including	306.1	306.5	0.4	447	100
	346.1	348.1	2.0	10.6		Lynx SW	Lynx
including	347.3	347.7	0.4	50.2
WST-20-0345	361.7	363.9	2.2	3.75		Caribou corridor	Caribou
including	362.3	363.1	0.8	9.43
WST-20-0400	158.0	160.2	2.2	11.2		Lynx_301	Lynx
including	159.0	160.2	1.2	19.7
WST-20-0411	148.2	150.4	2.2	38.1	36.1	Lynx HW	Lynx
including	149.2	149.9	0.7	107	100
WST-20-0412	155.0	157.2	2.2	3.06		Lynx_328	Lynx
including	156.9	157.2	0.3	11.2
WST-20-0417	190.6	192.6	2.0	22.4		Lynx	Lynx
including	190.6	191.2	0.6	41.5
	428.2	430.2	2.0	4.06		Lynx 4	Lynx
WST-20-0423	125.0	127.0	2.0	5.23		Lynx	Lynx
including	125.0	125.7	0.7	14.9
WST-20-0459	204.3	206.4	2.1	20.6		Lynx SW	Lynx
including	205.9	206.4	0.5	76.2
WST-20-0462	171.0	173.0	2.0	40.4		Lynx	Lynx
including	171.5	172.5	1.0	79.1
	454.0	456.0	2.0	3.50		Lynx_336	Lynx
including	454.0	454.8	0.8	8.19
	638.9	643.2	4.3	3.82		Lynx	Lynx
including	638.9	639.6	0.7	12.6
WST-20-0470	86.2	88.2	2.0	73.8	15.0	Lynx	Lynx
including	87.5	87.8	0.3	492	100

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

Drill hole location

Hole Number	Azimuth (°)	Dip (°)	Length (m)	UTM E	UTM N	Elevation	Section
OSK-W-17-1258	126	-51	1128	452972	5435211	416	3275
OSK-W-18-1727	331	-61	810	453461	5435040	396	3625
OSK-W-19-1857-W11	108	-58	1385	453525	5435704	405	4000
OSK-W-19-2100-W4	122	-47	1260	453095	5435726	423	3650
OSK-W-19-2101	18	-68	909	453426	5434779	396	3475
OSK-W-19-2169	130	-50	1268	453215	5435512	410	3650
OSK-W-19-2173	156	-46	234	452182	5435722	407	2850
OSK-W-19-2177	153	-51	396	452454	5435997	406	3225
OSK-W-20-2133-W2	118	-49	1139	453080	5435531	417	3525
OSK-W-20-2139-W7	115	-52	1164	452980	5435549	420	3450
OSK-W-20-2139-W8	115	-52	1125	452980	5435549	420	3450
OSK-W-20-2139-W10	115	-52	1212	452980	5435549	420	3450
OSK-W-20-2170-W6	128	-59	1407	453425	5435657	413	3900
OSK-W-20-2197-W2	121	-48	1064	453087	5435526	417	3550
OSK-W-20-2217-W2	134	-48	893	452944	5435565	418	3425
OSK-W-20-2217-W3	134	-48	1128	452944	5435565	418	3425
OSK-W-20-2249	132	-56	759	452775	5435192	411	3100
OSK-W-20-2250	132	-57	1064	453129	5435505	419	3575
OSK-W-20-2250-W1	132	-57	1060	453129	5435505	419	3575
OSK-W-20-2250-W2	132	-57	1134	453129	5435505	419	3575
OSK-W-20-2250-W3	132	-57	1170	453129	5435505	419	3575
OSK-W-20-2250-W4	132	-57	1005	453129	5435505	419	3575
OSK-W-20-2252-W2	129	-54	1194	453241	5435694	415	3750
OSK-W-20-2252-W3	129	-53	1062	453241	5435694	415	3750
OSK-W-20-2253	128	-54	924	452831	5435326	413	3225
OSK-W-20-2256	125	-51	1179	453160	5435686	414	3675
OSK-W-20-2256-W2	125	-51	957	453160	5435686	414	3675
OSK-W-20-2260-W2	127	-48	1191	453201	5435667	413	3700
OSK-W-20-2263	128	-49	1029	452926	5435187	413	3225
OSK-W-20-2266	128	-55	1050	453067	5435478	418	3500
OSK-W-20-2266-W1	128	-55	1116	453067	5435478	418	3500
OSK-W-20-2266-W2	128	-55	1131	453067	5435478	418	3500
OSK-W-20-2267	135	-52	66	452972	5435210	416	3275
OSK-W-20-2268-W1	127	-55	1073	453148	5435488	418	3575
OSK-W-20-2268-W2	127	-55	1038	453148	5435488	418	3575
OSK-W-20-2269	133	-50	933	452972	5435210	416	3275
OSK-W-20-2271	120	-53	1247	453462	5435683	410	3950
OSK-W-20-2272	149	-45	1004	452967	5435265	412	3300
OSK-W-20-2273	129	-51	1059	453067	5435478	417	3500
OSK-W-20-2280	127	-58	1161	453304	5435639	415	3775
OSK-W-20-2280-W1	127	-58	1170	453304	5435639	415	3775
OSK-W-20-2282	148	-56	588	452875	5435181	409	3175
OSK-W-20-2283	135	-50	1151	452997	5435607	425	3500
OSK-W-20-2288	146	-51	749	452875	5435181	409	3175
OSK-W-20-2292	125	-54	1059	453037	5435563	420	3525
OSK-W-20-2295	132	-51	987	452938	5435472	415	3375
OSK-W-20-2295-W1	132	-51	960	452938	5435472	415	3375
OSK-W-20-2298	137	-50	596	452847	5435059	407	3100
OSK-W-20-2305	124	-55	911	453026	5435408	413	3425
OSK-W-20-2306	152	-55	531	452872	5435155	407	3175
OSK-W-20-2307	124	-54	878	453397	5435557	413	3825
OSK-W-20-2310	333	-51	144	451970	5434835	407	2225
OSK-W-20-2312	334	-51	192	451964	5434816	408	2225
OSK-W-20-2324	334	-51	167	451944	5434811	406	2200
WST-20-0135	187	-58	444	453226	5435125	134	3475
WST-20-0318	148	-52	502	453228	5435127	134	3475
WST-20-0339	146	-18	295	453410	5435229	114	3675
WST-20-0341A	163	-42	493	453228	5435126	134	3475
WST-20-0345	136	-21	401	452282	5434975	263	2575
WST-20-0400	167	16	172	453493	5435287	118	3775
WST-20-0411	156	38	171	453450	5435264	118	3725
WST-20-0412	164	24	165	453450	5435264	117	3725
WST-20-0417	138	-50	759	453228	5435126	134	3475
WST-20-0423	134	-18	142	453359	5435209	154	3625
WST-20-0459	153	-47	579	453227	5435126	135	3475
WST-20-0462	152	-53	680	453227	5435125	134	3475
WST-20-0470	158	9	184	453493	5435287	118	3775

Lynx Zone
Mineralization occurs as grey to translucent quartz-carbonate-pyrite-tourmaline veins and pyrite replacement zones and stockworks. The vein-type 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.

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.

F-Zone
Mineralization is hosted in sheared andesites with carbonate replacement or quartz veining and occurs as quartz ± ankerite veinlets or in shear zones as replacement, 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.

Mallard
Mineralization is hosted in sheared mafic volcanics with felsic porphyritic intrusions and occurs as veins associated with sericite-pyrite ± silica ± chlorite alteration and contains pyrite ranging from trace to 30% and local visible gold.

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), Project Manager of Osisko's Windfall Lake 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. All NQ core assays reported 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, Thunder Bay, Ontario, Sudbury, Ontario or Vancouver, British Colombia, or (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 an Aqua Regia-ICP-AES 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 Eeyou Istchee James Bay, Québec, Canada. The mineral resource defined by Osisko, as disclosed in the news release dated February 19, 2020 and supported by the technical report entitled “An updated mineral resource estimate for the Windfall Lake Project, Located in the Abitibi Greenstone Belt, Urban Township, Eeyou Istchee James Bay, Québec, Canada” and dated April 3, 2020 (with an effective date of January 3, 2020), and assuming a cut-off grade of 3.5 g/t, comprises 4,127,000 tonnes at 9.1 g/t Au (1,206,000 ounces) in the indicated mineral resource category and 14,532,000 tonnes at 8.40 g/t Au (3,938,000 ounces) in the inferred mineral resource category. The key assumptions, parameters and methods used to estimate the mineral resource estimate disclosed in the February 19,2020 news release are further described in the full technical report prepared by Micon International Limited ("Micon") and BBA Inc ("BBA"), in accordance with NI 43-101 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 deformed sub-vertical zones plunging to the northeast. Vein-type or pyrite replacement-type styles of mineralization crosscut syn-volcanic host rocks and syn-deformation felsic porphyry intrusions and are spatially associated with the contacts of the intrusions. The deposit is well defined from surface to a depth of 1,200 metres and remains open along strike and at depth. Mineralization has been identified 30 metres from surface in some areas and as deep as 2,000 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 precious metal 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; the prospects, if any, of the Windfall gold deposit; the timing and ability of Osisko, if at all, to publish a feasibility study for the Windfall gold deposit; the projected capital expenditures of mining activities at the Windfall gold deposit; upgrading an inferred mineral resource to a measured mineral resource or indicated mineral resource category; future drilling at the Windfall gold deposit; the deposit remaining open along strike to the northeast and at depth; significant high-grade zones (Lynx 4, Triple Lynx) remaining open down plunge; the plunge potential of the Lynx and Underdog zones; 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 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