SAN BERNARDINO COUNTY, Calif.—With their four-wheel-drive trucks hugging the mountainside, prospectors Ron Kliewer and Sean Hart dodge tire-puncturing rocks jutting out of the narrow and steep road to their inactive uranium and rare earth mineral mines in the Mojave Desert.
Aside from a large uranium deposit, their square mile of mining claims is rich in 14 other critical minerals, including many rare earth elements. The uranium there was first discovered more than 70 years ago, during the uranium boom after World War II and the dawn of the nuclear age.











