Higher prices in America suit miners with copper assets in the country just fine. The shares of Rio Tinto and Freeport-McMoRan, an American miner which accounts for 60% of domestic copper production, have risen. For the latter, a 50% duty could result in windfall profits of $1.6bn a year, reckons Deutsche Bank, another lender.

The U.S. copper industry is in crisis — and Washington is finally taking notice. With President Donald Trump’s recent announcement of 50% tariffs on copper imports under Section 232 of the Trade Expansion Act,