Capstone strike ends allowing Mantoverde at full rate

Capstone Copper (TSX: CS; ASX: CSC) is preparing to restore full output at its Mantoverde copper-gold mine in Chile after workers in the operation’s biggest union ratified a new three-year contract.

The agreement, announced in a regulatory filing late on Thursday, ends a strike that began Jan. 2 and left Mantoverde running at about 55% of normal production, the Vancouver-based miner said. Capstone added that it now has three-year collective bargaining agreements in place with all four unions at the site.

Capstone said it plans to focus on a safe, efficient ramp-up as crews return to regular operations.

Labour stability matters at Mantoverde because it’s Capstone’s largest producing mine. The asset delivered 95,000 tonnes of copper in 2025 and accounted for 44% of the company’s production, according to a company documents.

Mitsubishi partner

Capstone owns 70% of Mantoverde and Japan’s Mitsubishi Materials holds the remaining 30%. The open-pit operation includes a 32,000-tonne-per-day sulphide concentrator and an underutilized 60,000-tonne-per-year solvent-extraction and electrowinning facility.

Capstone is also pushing ahead with a Mantoverde debottlenecking plan intended to lift mill capacity to 45,000 tonnes per day. The company estimates the cost at $176 million (C$240 million) and says it could add about 20,000 tonnes a year of additional copper output.

Capstone did not disclose financial terms of the new labour deal or provide a detailed timetable for the return to full rates.

Beyond Mantoverde, Capstone’s operating portfolio includes Pinto Valley in Arizona, Cozamin in Mexico and Mantos Blancos in Chile. Its main development option is the fully permitted Santo Domingo copper-iron-gold project, about 35 km northeast of Mantoverde.