SCIENCE

Rare Earth Elements Not Rare, Just Playing Hard to Get

November 18, 2010

Given their name, rare earth elements, and the fact that China controls 96 percent of REE production, you might think the Chinese had won some geologic lottery. But these metallic substances—elements 57 to 71 on the periodic table, plus scandium and yttrium—are not all that rare. It's been economic and scientific smarts, not geologic luck, that has given China its near monopoly on these elements.

REE are almost ubiquitous in modern technology because they're incredibly useful. They are the "vitamins of chemistry," says Daniel Cordier, a mineral commodities specialist for rare earths at the U.S. Geological Survey. "They help everything perform better, and they have their own unique characteristics," he says, "particularly in terms of magnetism, temperature resistance and resistance to corrosion." Those characteristics have helped REE find homes in everything from flat-panel TVs and smart phones to anti-lock brakes and air bags in cars, from sunglasses and crystal to lasers and smart bombs.

The rare earths were common when Earth was accreting, and so they are more abundant in the inner parts of the planet. They concentrate on the surface only in places where mantle eruptions have worked their way up through the crust, mostly in igneous materials. But unlike more familiar metals, such as gold and copper, rare earths don't clump in single-element chunks. Instead, the REE all wait together as hot rocks are crystallizing. "They tend to follow phosphate around and hang out until the very end," says Cordier, "and then they'll crystallize out." Recoverable concentrations can be found in several minerals, such as bastnaesite and monazite. But refining these minerals into individual elements takes many days of heavy processing.

The United States has one of the richest REE deposits in the world, at Mountain Pass in California, but as interest in rare earths declined in this country in the late 20th century, China's interest was heating up. Chinese scientists had visited during the Nixon Administration and taken their knowledge home, applying it to their own rich deposits. By the end of the 20th century, they were able to undersell the competition and drive most of the rest of the world out of the business. "They now sit in the driver's seat," says Cordier.

Earlier this year, China blocked REE exports to Japan, renewing concerns about the Chinese monopoly and prompting new calls for developing rare earth production elsewhere. The Mountain Pass mine, which has been inactive for several years, is scheduled to start up again in 2011. A new report from the USGS documents REE deposits in 13 additional states, and India, Australia and Canada are planning to get into the rare earths business more heavily.

And anyone looking for new REE deposits could benefit from the years of Chinese work in this area. Most of the world's heavy rare earths come from ionic adsorption clays in southeast China, Cordier says, and no one has really looked at this type of clay elsewhere in the world. "There's a lot of opportunity for exploration," he says.