The red metal was under pressure as this year's 30% price increase has prompted Glencore to restart its idled Mutanda copper and cobalt mine in the Democratic Republic of Congo next year, Marex Spectron's Anna Stablum said.

Other base metals also closed lower, with zinc and nickel falling by similar amounts.

The recent volatility in cryptocurrencies was contrasted by strength in the gold price, which rose to $1,890 an ounce on the spot market.

However it had softened back to about $1,868/oz at the time of writing, after the US Federal Reserve released the minutes of its April meeting.

"A number of participants suggested that if the economy continued to make rapid progress toward the committee's goals, it might be appropriate at some point in upcoming meetings to begin discussing a plan for adjusting the pace of asset purchases," it said.

Mining majors closed lower, with copper producer Freeport-McMoRan tumbling 6.6% in New York.

In London, Anglo American led the losses with a drop of 4.71%.

Antofagasta, Rio Tinto and Glencore all closed down more than 3.3%.

Barrick Gold lost 1.55% in Toronto.