President Donald Trump mentioned Tuesday — almost in passing — that he planned to impose a 50% tariff on copper imports. It still hit like a bombshell, with potential to shake up U.S. efforts to expand,

U.S. President Donald Trump's 50% tariff on copper has placed a record premium on prices of the metal in the United States that is likely to ease over the coming months as a stockpile created by traders anticipating the levy works through the system.