Your Prius' Deepest, Darkest Secret

So you're considering buying a hybrid car. Or maybe you already have. Good for you! You're saving a bundle on gas and reducing your environmental footprint at the same time. But fuel isn't the only natural resource that your car requires. Its motor also contains a small amount of neodymium, one of 17 elements listed at the very bottom of the periodic table. Known as the rare earths, these minerals are key to all kinds of green technology: Neodymium magnets turn wind turbines. Cerium helps reduce tailpipe emissions. Yttrium can form phosphors that make light in LED displays and compact fluorescent lightbulbs. Hybrid and electric cars often contain as many as eight different rare earths.

And the stuff is good for more than just renewable energy technology. Walk down the aisles of your local Best Buy and you'll be hard-pressed to find something that doesn't contain at least one of the rare earths, from smartphones to laptop batteries to flat-screen TVs. They're also crucial for defense technology—radar and sonar systems, tank engines, and the navigation systems in smart bombs.

Given all this, it's not surprising that the rare-earths industry is booming. Demand for the elements has skyrocketed in the past few years, and a recent report predicted it to grow by 50 percent by 2017.

For the last few decades, China controlled the world's market for rare earths, producing about 97 percent of the global supply. But in late 2010, China cut its exports by 35 percent in order to keep the valuable metals for its own manufacturers. The prices of rare earths rose almost immediately. Fearing a shortage, US legislators sprang into action. This past April, Rep. Mike Coffman introduced a bill that would kick-start a domestic rare-earths renaissance in the United States.

A few rare-earths mines are slated to open in the United States in the next few years, the most hyped of which is a facility called Mountain Pass in California's Mojave Desert. (It's actually been around off and on since the '50s, but a company called Molycorp has given it a major makeover.) When it's running at full capacity, Mountain Pass will be the largest rare-earths mine in the world, producing upwards of 40,000 tons of the stuff every year.

Which means Molycorp will also have to deal with a whole lot of waste.  Rare earths occur naturally with the radioactive elements thorium and uranium, which, if not stored securely, can leach into groundwater or escape into the air as dust. The refining process requires huge amounts of harsh acids, which also have to be disposed of safely. Molycorp claims that its new operations are leak-proof, but the company's ambitious plans have raised a few eyebrows among environmentalists, since the site has a history of spills.

But no matter how quickly new mines open, the United States won't be able to produce enough rare earths on its own—it's thought that North America contains only 15 percent of the world's supply. A recent Congressional Research Service report (PDF) recommended that the US seek reliable sources in other countries.