Rare earths are among the most critical raw materials on the planet, deeply embedded in the technologies that underpin modern life. Yet few people had even heard of them until the eruption of the US-China trade war thrust them into the limelight.

Donald Trump said on Thursday the US and China had signed a trade deal, two weeks after saying they had reached an understanding in London about how to implement a truce in the countries’ dispute. “We just signed with China yesterday,” the US president said at the White House on Thursday, without providing any details.

The U.S. and China have agreed on the framework for a trade deal, both nations say. It appears that rare earth minerals are one key part of it.