Abandoned mines from the 19th-century gold rush could contain rare earth metals, elements vital for the production of smartphones, TVs, hybrid cars, and other electronics. The Associated Press reports that dumps of discarded material from gold rush mines could be rich with rare earths. The US Geological Survey (USGS) and Department of Energy are current searching the country in the hope of uncovering the vital metals in the hope of breaking China's stranglehold on worldwide supply.

An 1870 sample collected from a failed copper mine was found to be high in Indium, an uncommon (but not "rare earth") metal used in solar panels. It's this discovery that led scientists to believe that abandoned mines could contain rare earths. Old mines "were almost never analyzed for anything other than what they were mining for," Larry Meinert, director of the mineral resource program for the USGS tells the AP, "if they turn out to be valuable that is a win-win on several fronts — getting us off our dependence on China and having a resource we didn't know about." The resulting search has already thrown up some surprises: rare earths were found alongside minerals that were not known to occur together.

Despite the name, rare earths aren't actually all that rare. The reason for the term is the elements are extremely difficult to mine. Not only do they occur in tiny quantities — you'll never find a rich "vein" of a rare earth as you would, say, copper — but they're also often fused together with other rare earths. As there's no simple way of separating two rare earths chemically (they're too closely linked in atomic structure), rare earth mining is extremely expensive. Presently, China controls the vast majority of rare earths, and has raised the per-kilogram price of some elements by as much as 1000 percent in recent years. It also cut off exports to Japan during a fishing dispute, and the worry of China having control over a high-demand resource reportedly sent the US government into "emergency mode," ramping up efforts to discover new sources on home soil. Energy independence has been a long-term goal of the US, and authorities don't want an oil-like situation where they're dependent on other countries for vital resources.

So far, researchers say they've found "several dozen" new locations that are elevated in "one or more critical metals." They want to use this data to predict further deposits, and hope to gain the assistance of native mining companies for their search.