MP Materials’ Mountain Pass mine and processing facility in California was for years the only U.S. rare earth elements mine. Tmy350/Wikimedia Commons, CC BY-SA The United States is spending billions of dollars to secure access to critical minerals – minerals and metals that are essential to modern technology, from electric vehicles to smartphones and military systems. But amid the push to dig more, one question gets far too little attention: Who will actually process what comes out of the grou