Osisko Reports Results From Ore Sorting Testing Program Conducted On Bulk Tonnage Sample Of Mineralized Material Extracted From Cariboo Gold Project In Central British Columbia

HIGHLIGHTS

• X-ray transmission (XRT) ore sorter testwork of a ~80 tonne sample taken from the Cariboo underground achieved positive results consistent with 2025 FS parameters
• 42-55% waste rejection with 84-89% gold recovery achieved by sorting mid-size and oversize sample material including 10–30 mm and 30–70 mm size fractions, respectively
  • Encouraging results from testing the previously unassessed 6–10 mm size fraction, made possible by recent advancements in AI, demonstrated 59% waste rejection and 95% gold recovery, highlighting a potential opportunity for future optimization
• 2.0-2.1 upgrade ratio consistent with 2025 FS assumption of 1.95
• New testwork represents a significantly larger data set, with previous sorting totalling ~5 tonnes and completed largely on material sourced from drill core
• 76% of the contained gold in the test sample estimated to report to the fines fraction (<10 mm)
• Flowsheet optimization work, including a variability study to refine assumptions across the deposit, is contemplated to be completed as part of detailed engineering

MONTREAL, July 07, 2025 (GLOBE NEWSWIRE) -- Osisko Development Corp. (NYSE:ODV, TSXV:ODV) ("Osisko Development" or the "Company") is pleased to announce positive results from an ore sorting testing program conducted on a bulk tonnage sample of mineralized material extracted from its permitted, 100%-owned Cariboo Gold Project ("Cariboo" or the "Project"), located in central British Columbia ("B.C."), Canada. The testwork results demonstrate gold recoveries, mass pull, and upgrade ratios consistent with the assumptions outlined in the 2025 FS (as defined herein), and were conducted on a significantly larger scale than previous programs. Importantly, positive results on a previously untested smaller 6–10 mm size fraction may represent a meaningful opportunity for flowsheet optimization.