President Donald Trump’s idea to buy Greenland may be fantasy, but the US has staked an interest in the island’s resources — in particular, its rare earth minerals. The US recently signed a memorandum to co-operate with the autonomous territory on rare earth mining in order to promote investment in the sector, amid wider efforts to secure alternative supplies after China hinted that it could constrict exports to the US. China dominates the global production of these rare earths, a group of 17 metals difficult to commercialise but critical to high-tech applications, including electric vehicles, wind turbines and military technology. More than 70 per cent are mined, and an even higher percentage processed, in China.