Rare-earth elements could be hidden inside coal mines

Valuable rare earth elements that are crucial for batteries, touchscreens and other modern technologies may be snuggled right up against fossil fuels, researchers have discovered. 

A new study of coal mines in Utah and western Colorado found that rock layers alongside coal seams are rich in elements like scandium, yttrium and neodymium. These and other rare-earth elements are used in ubiquitous modern technologies like smartphones and are also crucial for green energy technologies such as wind turbines and hybrid cars. 

The vast majority of rare earth elements are currently mined or processed in China, and so the U.S. Department of Energy has been funding the hunt for these elements in the United States, in hopes of spurring domestic production. 

"There’s a real societal need to develop these minerals domestically," study co-author Lauren Birgenheier, a geologist at the University of Utah, told Live Science. 

Inspired by previous research that had found rare earth elements in association with coal in the Appalachian region, Birgenheier and her team took samples from six active and four idle coal mines in central Utah and western Colorado. The researchers used X-ray fluorescence and mass spectrometry — two geochemical methods for determining which elements exist within a sample — to look for traces of the 17 metallic rare earths elements. 

Related: Secrets of radioactive 'promethium' — a rare earth element with Mysterious applications — uncovered after 80-year search

The researchers found that between 24% and 45% of shale and siltstone rocks adjacent to coal seams had at least 200 parts per million (ppm) of these elements, while 100% of volcanic rocks sampled contained rare earth elements at those levels or higher.