Yale e360 has an excellent article focusing on the risks associated with the spread of rare earth mining.
As global demand has surged in recent years for rare earth elements, fears have grown that China, which accounts for more than 95 percent of rare earths output, will withhold supplies, as it did temporarily two years ago during a dispute with Japan. As a result, across five continents and numerous countries — including the United States, Brazil, Mongolia, and India — rare earth processing projects are being launched or revived. With them comes the potential threats to the environment and human health that have plagued China’s processing sites.
“As the world’s hunger for these elements increases... the waste is going to increase,” says Nicholas Leadbeater, a chemist at the University of Connecticut whose research focuses on developing green technologies. “The more mines there are, the more trouble there’s going to be.” To avoid such problems, Leadbeater says some researchers are now looking into ways of recovering rare earths from existing products, and of manufacturing products capable of running without rare earths. Toyota, for example, is developing an electric motor that does not use rare earths in its battery, as most currently do.
Rare earth metals are not rare in that they are hard to discover, but in that they are difficult to separate out from the surrounding rock in which they are found. The chemicals required for the process and the long-term toxic danger they pose has researchers worried about the push for more mining and the under-regulated projects around the world.
Yale e360 does an excellent job of outlining the issue and what's at stake. We recommend reading their article in full.