Reuters/Santiago

Workers began a surprise strike at the world’s largest copper mine, Chile’s Escondida, yesterday morning to demand improved working conditions and pay.
The work stoppage at Escondida, controlled by global miner BHP Billiton , was initially planned to last 24 hours, but the timeframe will be evaluated in the coming hours, union representative Marcelo Tapia said.
“(All operations) have been halted,” said Tapia, adding the union’s 2,500 workers had dropped their tools. “It’s due to a variety of issues that the company has not been responding to.”
He added that workers at BHP’s Spence and Cerro Colorado mines also joined the labour action, which kicked off at 8am local time (1200GMT).
BHP and Rio Tinto, which own 30% of Escondida, declined to comment.
Escondida produced 1.1mn tonnes of copper last year, about 20% of the output from No. 1 copper producer Chile.
The mine’s union stunned the copper market in 2011 by staging a two-week work stoppage, sending the mine’s output tumbling.
Workers clinched a new contract agreement in January, at the time easing fears of labour unrest at the mine. Labour action has been galvanised in mining powerhouse Chile as unions seek to get their issues heard ahead of the November presidential election.
Meanwhile presidential front-runner Michelle Bachelet, who is campaigning on a promise to reduce income equality in Chile, said she is studying changes in mining policy for the world’s top copper-producing country. Bachelet, a former president who is widely expected to win the November 17 election or a possible runoff, did not provide concrete details, but she said her team is reviewing mine royalties and ways to finance state-owned mining company Codelco.
Chile raised royalties on mining companies to help fund reconstruction efforts following a devastating 8.8-magnitude earthquake in 2010 that cost the country $30bn.