One pit, more than a tenth of the world's rare earths

The pit is roughly 2,500 feet east to west and 3,000 feet north to south, and about 600 feet deep at its lowest point. It sits on the south flank of the Clark Mountain Range in California, 15 miles from the Nevada line, and geologists found rare earths there in 1949. Commercial mining began in 1952.

The orebody averages about 6.0 percent total rare earth oxides over life of mine — a grade most rare earth deposits in the world do not approach — and holds roughly 1.9 million metric tons of contained rare earth oxides at a 2.4 percent cutoff. That is decades of production at current rates, and it is why the site supplied most of the non-Chinese world's rare earths for the second half of the twentieth century.

It also went bankrupt. Low-cost Chinese production, and a 1990s release of low-level radioactive water and residue into the Mojave Desert that brought environmental enforcement down on the operation, shuttered the mine in 2002. When the current owners bought it, the property had eight employees and a pit partially underwater. It has more than 700 today and produces more than 10 percent of the world's rare earth supply.

The 2023 milestone was metallurgical, not geological: the company refined neodymium-praseodymium to 99.9 percent purity at the site, which moved Mountain Pass from a concentrate shipper to a separator. Oxide from California now goes to a magnetics facility in Fort Worth, Texas, where it is melted, cooled, compressed and diced into permanent magnets, with General Motors as the first automotive customer.

What the site still lacks is breadth. Heavy rare earth separation — dysprosium, terbium — is being built with federal loan support, and the separation and finishing steps are where most of the value, and almost all of the non-Chinese bottleneck, sits. The mine is the easy half of the problem. The chemistry after the crusher is the hard half.