Copper futures prices eased on Friday after striking copper miners in Mexico went back to work, dousing supply concerns that had driven the market higher this week.
Three-month London Metal Exchange-traded copper dropped as much as $35 before recovering to trade $5 lower at $4,965/$4,975 a tonne following news that strikes at Grupo Mexico's big Cananea and La Caridad copper mines had ended after two days.
"That news took the steam out of copper," a trader said.
Traders said they had been looking for further upside moves in copper after the benchmark futures contract put in a strong showing in the last London outcry session, where it ended $115 higher at $4,970 a tonne on concerns that a lengthy strike would pinch supplies and drive prices even higher.
Investment interest in copper, which climbed to its highest price ever - $5,100 a tonne - on February 7, had since waned until the strikes across Mexico that also idled refineries and steel mills.
"The market was looking for a reason to buy copper again and the strikes were a perfect excuse," said Bache Financial minerals strategist Angus MacMillan.
A nation-wide wildcat strike at Mexican mines, refineries and steel mills collapsed on Thursday with union members returning to work at all of the country's biggest operations.
The strikes began on Tuesday in support of the beleaguered boss of Mexico's mine union, Napoleon Gomez, who faces a leadership challenge and government accusations of corruption.
After shutting down the entire mining industry for two days, most of the union's quarter of a million members went back to work at Mexico's main plants and mines on Thursday afternoon, the companies and the union said.
Swelling LME-held copper stocks also took some of the sting out of supply woes, with the tonnage rising a further 2.7 percent on Thursday to 118,375 tonnes.
Volume was light across the LME complex, though activity was expected to pick up if a plan by the LME to extend electronic trading hours in Asia is implemented.
Britain's Office of Fair Trading this week barred the LME from extending the electronic trading hours, which had been due to start on Wednesday in response to a request by rival electronic trader Spectron. Spectron has since withdrawn the request.