alt Hacker NewsNice. Here's MP Minerals' plant for doing that, in Alliance, TX.[1] It's a modest sized plant in an industrial park. It's fed by a huge mine in California, which has an onsite beneficiation plant. Beneficiation is the first step of separation - sorting the good stuff out from the unwanted dirt, with rock crushers, screens, and flotation. This being "rare" earth mining, the amount of good stuff is tiny relative to the unwanted dirt. This new technology works on the separated good stuff.
Although these separation plants aren't big compared to mines, US mines had been sending rare earth ores to China for processing. That's gradually moving back to the US as more separating plants are built.