Osisko Development Corp. announced the remaining drilling and underground chip sampling results from new development areas as part of its 2023 exploration program at its 100%-owned Trixie test mine (?Trixie?), within the Company's wider Tintic Project (?Tintic? or the ?Tintic Project?), located in the historic East Tintic Mining District in central Utah, U.S.A. This news release includes assays from fourteen underground diamond drill (?DD?) holes.

Select assay highlights include: 66.04 grams per tonne (?g/t?) gold (?Au?) and 167.64 g/t silver (?Ag?) over 8.99 meters (?m?) in TRXU-DD-23-072A (1.93 ounce per ton (?oz/t?) Au and 4.89 oz/t Ag over 29.50 feet (?ft?)) including: 610.00 g/t Au and 1,523.00 g/t Ag over 0.46 m (17.79 oz/t Au and 44.42 oz/t Ag over 1.50 ft); 180.00 g/t Au and 691.00 g/t Ag over 0.76 m (5.25 oz/t Au and 20.15 oz/t Ag over 2.50 ft). 23.89 g/t Au and 151.04 g/t Ag over 9.45 m in TRXU-DD-23-068 (0.70 oz/t Au and 4.41 oz/t Ag over 31.00 ft) including: 81.23 g/t Au and 98.14 g/t Ag over 0.76 m (2.37 oz/t Au and 2.86 oz/t Ag over 2.50 ft). 102.67 g/t Au and 740.43 g/t Ag over 1.07 m in TRXU-DD-23-061 (2.99 oz/t Au and 21.60 oz/t Ag over 3.50 ft) including: 281.00 g/t Au and 1,644.00 g/t Ag over 0.30 m (8.20 oz/t Au and 47.95 oz/t Ag over 1.00 ft).

10.84 g/t Au and 35.29 g/t Ag over 4.57 m in TRXU-DD-23-066 (0.32 oz/t Au and 1.03 oz/t Ag over 15.00 ft); 5.79 g/t Au and 101.98 g/t Ag over 13.72 m in TRXU-DD-23-065 (0.17 oz/t Au and 2.97 oz/t Ag over 45.00 ft). Drill results summary: In 2023, the company completed a total of 6,028 m (19,776 ft) of underground drilling in 73 DD holes at Trixie. Assays have now been received for all 2023 holes testing the Trixie high sulphidation epithermal Au-Ag targets.

A new mineral resource estimate (?MRE?) for the Trixie deposit (?Trixie MRE?) is in progress and is expected to be released in March 2024. The Trixie MRE will include all underground drilling and chip sample assays from the 2023 program. One additional hole (TRXU-DD-23-073) was drilled to a depth of 759.6 m (2,492 ft) and targeted a copper-gold porphyry target below Trixie.

Assays for this hole are pending. The focus of these recent holes was to test for mineralization along one of the priority target areas south on strike from the known T2 domain, south towards the Sioux Ajax fault. Results from holes TRXU-DD-23-065 (5.79 g/t Au over 13.72 m), TRXU-DD-23-066 (10.84 g/t over 4.57 m) and TRXU-DD-23-068 (23.89 g/t Au over 9.45 m) indicate that the mineralization appears to be plunging to the south towards the Sioux Ajax Fault.

One diamond drill rig is currently active at surface testing a copper-gold-molybdenum target at Big Hill and is at a current depth of 922 m (3,028 ft). The target depth for this hole is approximately 1,524 m (5,000 ft). Assays are pending for this drillhole.

Underground chip sample assay highlights: Assay highlights include underground chip samples from 55 new development faces at Trixie. Of these, 25 faces had samples with greater than 1.0 g/t Au or greater than 50.0 g/t Ag values. The remaining chip samples returned no significant assays.

Selected assay highlights include: 123.67 g/t Au and 658.46 g/t Ag over 4.27 m in CH01683 (3.61 oz/t Au and 19.21 oz/t Ag over 14.00 ft) including: 717.86 g/t Au and 2,996.98 g/t Ag over 0.61 m (20.94 oz/t Au and 87.41 oz/t Ag over 2.00 ft). 40.84 g/t Au and 67.16 g/t Ag over 3.66 m in CH01694 (1.19 oz/t Au and 1.96 oz/t Ag over 12.00 ft) including: 153.72 g/t Au and 227.32 g/t Ag over 0.91 m (4.48 oz/t Au and 6.63 oz/t Ag over 3.00 ft). 385.26 g/t Au and 1094.04 g/t Ag over 0.30 m in CH01687 (11.24 oz/t Au and 31.91 oz/t Ag over 1.00 ft) 26.89 g/t Au and 186.63 g/t Ag over 3.05 m in CH01682 (0.78 oz/t Au and 5.44 oz/t Ag over 10.00 ft) 28.62 g/t Au and 150.08 g/t Ag over 2.23 m in CH01676 (0.83 oz/t Au and 4.38 oz/t Ag over 7.30 ft) including: 62.60 g/t Au and 247.62 g/t Ag over 0.91 m (1.83 oz/t Au and 7.22 oz/t Ag over 3.00 ft); 7.74 g/t Au and 202.67 g/t Ag over 7.62 m in CH01679 (0.23 oz/t Au and 5.91 oz/t Ag over 25.00 ft); 18.48 g/t Au and 355.54 g/t Ag over 1.52 m in CH01664 (0.54 oz/t Au and 10.37 oz/t Ag over 5.00 ft).

Chip sample summary: Chip samples were collected in new development areas in the face and walls of exploration crosscuts to explore along all domains of the Trixie deposit on the 625 Level, to the north towards the Trixie Fault and to the south towards the Sioux Ajax Fault. The sampling and drilling results indicate that target areas to the north of Trixie and to the south down plunge of the T2 structure are potentially mineralized and warrant further follow-up exploration drilling and sampling to understand the extent of mineralization.