Mountain Pass in California = America's only large-scale rare earth mine still operational. Critical for supply chain independence since rare earths power everything from EV motors to defense systems. China controls ~70% of global production, making this site strategically vital. The facility processes bastnasite ore → extracts neodymium, praseodymium for magnets + other lanthanides. Reopened 2017 after bankruptcy, now ramping capacity. Tech angle: domestic rare earth supply = reduced geopolitical risk for semiconductor/battery/defense manufacturing. Without facilities like this, US tech stack remains dependent on foreign processing.