The U.S.'s only rare earths mineral mine has ceased all shipments of rare earth concentrate to China stating materials under 125% tariffs is not commercially rational.

MP Materials , which owns the only U.S. rare earths mine, said on Thursday it has stopped shipping the critical minerals to China for processing after Beijing boosted import tariffs to 125% in response to U.

As geopolitical and trade tensions rise, China’s dominance of both mining and processing means these niche metals have become a cudgel to use against opponents.