Published: April 30, 2025 |

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Osisko Development has released the results of a positive optimized feasibility study for its permitted, 100 percent owned Cariboo Gold Project located in central British Columbia Canada. The 2025 FS was completed by BBA Engineering as lead independent consultant, and supported by other independent engineering firms.

The 2025 FS confirms strong economics for a low-impact underground operation using mechanized bulk mining methods, with attractive operating costs, manageable capital requirements, and well-positioned to benefit from favorable macroeconomic and gold price trends. The process facilities have been designed to accommodate potential future throughput expansions.

“The completion of this optimized feasibility study represents a critical milestone for the Cariboo Gold Project, one of the few undeveloped, permitted gold projects in a tier-1 jurisdiction. The results reaffirm our view that Cariboo is a high-quality asset with robust returns and significant upside potential within the existing mine plan,” said Sean Roosen, founder, chairman, and CEO.

“Our immediate focus remains on advancing project financing and further de-risking the project toward FID, but, we believe additional work could support potential future production increases within the planned mine footprint. Additionally, our extensive land position around the project area offers numerous opportunities for new discoveries in this prolific gold belt. With today’s favorable gold price backdrop and positive outlook, we believe this project is well-positioned to deliver substantial value to all stakeholders,” added Roosen.

A formal positive final investment decision, along with securing of a project financing package in the coming months would enable certain construction activities to commence in the second half of 2025, with project completion targeted for the end of 2027.

The Cariboo Gold Project is envisioned as a traditional underground operation, employing mechanized long-hole open stoping to extract ore from gold-bearing vein corridors — an intricate network of mineralized quartz veins predominantly hosted within unmineralized sandstone.

MINING AND MINE DESIGN

Underground mining will target five mineralized zones along 4,400 m of strike, accessed via two ramps: the currently operational Cow portal and a new Valley portal. Each zone includes several vein systems extending to a vertical depth of approximately 650 m. Following a 24-month development period, underground mining will ramp up to a design rate of 4,900 tpd over 10 months. The bulk-tonnage long-hole mining method was chosen for its cost-effectiveness, flexibility, and suitability for the sub-vertical vein geometry. To reduce the impacts of dilution, ore sorting technology will be used to separate gold-bearing sulphide ore (pyrite) from the lower-density unmineralized sandstone rock prior to milling and beneficiation.

The stope design parameters include a minimum width of 3.7 meters, stope heights of approximately 30 meters, and strike lengths ranging from 15 to 25 meters, depending on the zone.

Mined ore will be extracted using a fleet of 10 tonne load haul dump and 50 tonne haul trucks to be transported to an underground crushing facility where it will be sized and transported to surface by an inclined conveyor for pre-concentration ore sorting and subsequent flotation concentration and gravity separation.

Underground development will rely on a combination of traditional jumbos and roadheaders. The company has previously successfully deployed a roadheader in excavating the Cow portal, ramp, and one drift in Bonanza Ledge, demonstrating that the underground rock conditions are amenable to the use of roadheaders under certain conditions.

PROCESSING AND RECOVERY

The processing flowsheet is designed for a single processing facility outside of Wells at the Mine Site Complex utilizing a combination of gravity and flotation processing circuits to produce two gold concentrates.

Crushing would occur underground in the Cariboo South region of the ore body. Material would be conveyed from the secondary crusher to the surface ore sorter. The crushed material is then screened, with fines bypassing the tertiary crusher and reporting directly to the mill feed bin while coarser material would be screened into two suitable feed streams for sorting. The sorted product will be tertiary crushed and returned to the mill feed bin.

ADDITIONAL METALLURGICAL WORK

The following metallurgical work is in progress to support refined basic and detailed engineering:
• Pilot sorter testwork
• Grinding variability testwork
• Flotation variability testwork
• Confirmatory dewatering testwork

WASTE DISPOSAL

Ore sorter waste is to be disposed in the same manner as mined waste rock — in the surface waste rock storage facility. This removes material from the mill circuit and allows a lower cost disposal method for barren rock than is utilized for mill tails streams. Whole flotation tails will be used as paste backfill underground.

PERMITTING, ENVIRONMENTAL, AND CLOSURE

Following the positive decision by the environmental assessment office to grant the project an environmental assessment certificate, the project underwent a robust and rigorous review by a dedicated mine review committee, set up by the Major Mines Office, and subsequently received the following permits for the Cariboo Gold Project:

• Mines Act permit for the Mine Site Complex and Bonanza Ledge
• Mines Act permit for the QR Mill
• Environmental Management Act Permit for the Mine Site Complex
• Environmental Management Act Permit for Bonanza Ledge
• Environmental Management Act Permit for QR Mill

The Mines Act (British Columbia) permits received on November 20, 2024, grant the company the ability to proceed with the construction, operation, and reclamation activities on each of the sites outlined within the scope of the project.

The Environmental Management Act (British Columbia) permits pertain to any project-related discharges to the environment, including water and air, and the framework and limitations within the areas outside of the immediate mine site boundaries. These approvals mark the successful completion of the permitting process for key approvals, solidifying the project’s shovel-ready status.

Work is ongoing with the Ministry of Water, Land, and Resource Stewardship and the Ministry of Forests on obtaining all necessary approvals for the construction of the transmission line, expected for H2 2025.

STAKEHOLDER, COMMUNITY, AND PARTNER ENGAGEMENT

The company is committed to advancing collaborative partnerships with Indigenous nations related to the project as evidenced by many years of extensive consultation and the signing and ongoing implementation of the participation agreements with each of the Lhtako Dené Nation (in 2020) and the Williams Lake First Nation (in 2022).

The company is working towards an agreement with the Xatśūll First Nation. While an agreement has not yet been reached, the company remains committed to ongoing engagement and consultation. This includes good faith and reasonable offers for financial and other benefits along substantially similar frameworks as those agreed to by Lhtako Dené Nation and Williams Lake First Nation.

The company continues to engage the District of Wells and signed an agreement to fund a liaison position which will be executed once a suitable candidate is found. The liaison position is a requirement of the EAC and will work with the local community to ensure communication between the District of Wells and the company reflect the views of all community members. Further discussions on a community agreement will commence in Q2 2025.

The company is dedicated to developing a modern, safe and sustainable operation at the Cariboo Gold Project, and remains committed to engaging in constructive dialogue to ensure all Indigenous nations and stakeholders benefit from the development of the project, while ensuring it remains viable.

Osisko Development is a North American gold development company focused on past-producing mining camps located in mining friendly jurisdictions with district scale potential. The company’s objective is to become an intermediate gold producer by advancing its 100 percent owned Cariboo Gold Project, located in central B.C., Canada, the Tintic Project in the historic East Tintic mining district in Utah, U.S.A., and the San Antonio Gold Project in Sonora, Mexico. In addition to considerable brownfield exploration potential of these properties, that benefit from significant historical mining data, existing infrastructure and access to skilled labor, the company’s project pipeline is complemented by other prospective exploration properties. The company’s strategy is to develop attractive, long-life, socially, and environmentally sustainable mining assets, while minimizing exposure to development risk and growing mineral resources.

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