Comex copper for July delivery jumped 66.05 cents per pound, or 13%, to close at $5.645. That's a record high and the biggest single-day gain ever for copper, according to Dow Jones Market Data. The metal is up 41.6% year to date and up 23.3% over the past 52 weeks. In after-hours trading, the metal traded at $5.48 per pound, according to FactSet.

Donald Trump's mooted 50% tariff on copper imports into America has sharply exacerbated what was already a dislocation between New York and London prices for the metal. The chart shows that since Trump's inauguration traders have been placing a greater premium on the COMEX contract,