The Centinela copper mine strike in Chile could cut the mine’s November output by half, unions say, though owner Antofagasta insists its production outlook has not changed.
About 709 workers from two unions, Minera Esperanza and Distrito Centinela, walked out at 8 a.m. Wednesday after government mediated talks failed to settle a wage dispute. They make up about 22% of the mine’s direct workforce.
How the Centinela copper mine strike could hit output
The unions say the processing plants can initially keep receiving ore, but mining, haulage and mine development have been disrupted. They expect the effect to emerge after about two weeks and become clear in November, when output could fall by as much as half.
Antofagasta disputes the picture. The company says it remains willing to negotiate and that projected production is unchanged. Its 2026 group guidance stands at 625,000 to 655,000 tonnes of copper.
The mine produced 240,400 tonnes of copper last year and 97,100 tonnes in the first half of 2026, about a third of the group’s output. A second concentrator due to start ramping up at the end of 2027 is expected to add 170,000 tonnes of copper equivalent.
What the unions want
At the heart of the dispute is pay and benefits that differ between unions for workers doing similar jobs. The unions want equal benefits regardless of which union a worker belongs to. In 2017, Antofagasta negotiated with its three unions in parallel and reached largely equivalent terms.
Distrito Centinela union leader Hector Aguilera said earlier that workers were “convinced that now is the moment” to end the gap in benefits. The unions also said the company had refused to discuss equalizing them.
The company has offered a 2% real increase in base pay plus a bonus of 22.5 million Chilean pesos, about $22,900, per worker. The unions rejected the proposal. A vote to strike passed with 98.7% support on Sept. 28.
It is the first strike at Centinela and only the second in Antofagasta’s history.
Copper market on edge
London Metal Exchange copper rose about 1% to $14,614.50 a tonne on Thursday, as the strike added to worries over supply from Chile, which produces about 23% of the world’s mined copper.
Supply was already tight. Chile’s August copper output fell 12.8% from a year earlier to 369,500 tonnes, its lowest monthly level since February 2011, as operational problems, lower ore grades and bad weather weighed on output.
Antofagasta also cut its 2026 group guidance in August, after a weather related shutdown at its Los Pelambres mine. Meanwhile, supervisors at BHP’s Escondida, the world’s largest copper mine, are in government mediated talks to avoid a strike of their own.
A strike by two unions does not necessarily stop the whole mine, and neither side has said how much of Centinela’s output the 709 workers control. That gap is why the unions’ half estimate matters.
A quick deal would blunt the impact. A long strike would test both Antofagasta’s forecast and a copper market already short of new supply.
