Updates to this story
As China tightens its hold on the market for rare earths, the US has been on the hunt for other sources. And just look what it's found - 13 million metric tonnes of the stuff, hidden down the back of the sofa.
While most rare earths aren't actually that rare, mining is almost exclusively concentrated in China, which has warned that it plans to limit exports. This week, EU officials plan to plead with the country to change its mind.
The US, meanwhile, has been looking closer to home, and yesterday released a report detailing estimates of its own domestic rare earth element (REE) resources.
And it's good news. The US Geological Society has found significant deposits of REE in 14 states, with the largest at Mountain Pass, California, where REE was previously mined until 2002. Other large deposits include Bokan Mountain, Alaska, and the Bear Lodge Mountains in Wyoming.
REEs were also found in Colorado, Florida, Georgia, Idaho, Illinois, Missouri, Nebraska, New Mexico, New York and North and South Carolina.
“This is the first detailed assessment of rare earth elements for the entire nation, describing deposits throughout the United States,” says Marcia McNutt of the US Geological Survey.
“Although many of these deposits have yet to be proven, at recent domestic consumption rates of about 10,000 metric tons annually, the US deposits have the potential to meet our needs for years to come."
The problem is, though, that the world needs rare earths now - and mines can take years to build.
"Many... nickel mines have required in excess of 10 years of process development plus delays because of market timing," the report concedes. "A new REE mine would almost certainly fall into this last category for many of the same reasons — complex metallurgy and restricted opportunities for market entry."
In any case, says independent analyst Jack Lifton, such mines are hard to make profitable.
"I believe that this was the dirty little secret of why the rare-earth-mining industry failed in the non-Chinese world during the last generation," he says on his blog.
"China’s secret of success was not brilliant market-entry timing or low labor costs, as the pundits have theorized, but rather it was state participation in absorbing overheads, either as direct grants or mandated, shared-infrastructure resources."