The Mountain Pass Mine, in the Mohave Desert, was discovered by accident. Two prospectors were looking for uranium when their borrowed Geiger counter reacted at an outcrop. They sent a sample to be assayed by The United States Geological Survey, but it was worthless. Instead of the valuable uranium they had hoped to find, it contained a slightly radioactive mixture of various rare earth minerals.
The rare earth metals are not rare. The commonest members of the group occur more often than silver or copper. They are difficult to find in usable concentrations though, and in ores that readily give up their elements. In 2009, 95% of world production comes from China.
Chemically, the rare earths are the lanthanides, 15 similar elements that appear in one row of the periodic table, plus two elements with similar uses that appear right above them. Because they were difficult to process, they were long considered curiosities rather than substances of wide industrial use.
The U.S.G.S., alerted by the prospectors’ find, did a survey of the area. Nearby, the surveyors discovered a huge deposit of bastnaesite, an ore of rare earth minerals. It was only mildly radioactive, and was highly concentrated. Though rare earths are common, most deposits are contaminated by radioactive thorium to the point that they are unusable, or of too low a concentration to make mining worthwhile. This deposit was relatively clean, and very concentrated.
One of the original prospectors urged his employer, MCA (now Molycorp), to claim it. Molycorp took his advice, and became the owner of a huge source of rare earth minerals that was, at the time, close to worthless.
Times change. Within twenty years of the find, lanthanides were essential to science and technology. Europium brightens TV pictures. Lanthanum, gadolinium, and samarium are used in microwave ovens. Cerium, praseodymium, and neodymium are necessary to make glass for various technical applications. Neodymium also makes the Prius possible, as an essential ingredient in the magnets that store the cars’ energy. Wind turbines use neodymium too. Compact florescent bulbs each hold a pinch of rare earth, often from a California mine.
Mountain Pass is a scraggly desert community, usually unnoticed on the road from L. A. to Vegas. It holds the Mountain Pass Mine; a securely guarded open pit that long produced the majority of America’s neodymium. It used to be the biggest producer of rare earths in the world, but that title is now held by a mine in China.
The Mountain Pass mine has had problems. Spills of processing water contaminated a swath of desert, and mining stopped in 2002, though processing of already extracted ores and concentrates continued. Now the mine must follow rules that are stricter than anywhere else in the world. Layers of environmental safeguards protect the surrounding community, the desert, and the miners. Molycorp is aware of its corporate responsibilities, and very aware that it is under scrutiny.
The small company has been in talks with 18 California agencies that have jurisdiction over operations at the Mountain Pass Mine. Mining will begin again in 2011. The company estimates that it will spend $2.4 million each year on environmental protection. Rightly so. These expenses may increase the cost of American rare earth minerals though.
Will manufacturers buy American lanthanides? Since the production of modern cars and wind turbines are each a proudly green industry, it is likely they will. If they do, they will be endorsing clean mining. In addition, they will be helping to ensure that China, the only other sizable producer, does not hold monopoly power over the rare earth minerals.
