MP Materials, which runs the sole operating rare earths mine in the United States, is an unusual victim in the year-long tit-for-tat trade war between the two largest economies on the planet, as the conflict looks set to open up a new battlefront over technology. The operator of the Mountain Pass mine in California said it will kick-start its own processing operation by the end of 2020, after China last week more than doubled an import duty on concentrates to 25 per cent effective June 1. MP exports pellets – ground-up ores that contain oxides of rare earth elements –...