From fighter planes to nuclear reactor rods and smartphones, rare earth minerals are vital to a wide array of products. 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.

China is responsible for most of the world’s processing of rare earth metals and minerals, but its new export restrictions have raised the stakes for U.S. efforts to build its own supply chain and processing industry.

As the trade war continues to escalate, China has hit back at Trump by suspending exports of rare earth minerals.