Michael Vanden Berg, geologist with the Utah Geological Survey, examines a coal outcrop near Utah’s old Star Point mine. Credit: Lauren Birgenheier, University of Utah
These findings open the possibility that these mines could see a secondary resource stream in the form of metals used in renewable energy and numerous other high-tech applications, according to study co-author Lauren Birgenheier, an associate professor of geology and geophysics. “When we talk about them as ‘critical minerals,’ a lot of the criticality is related to the supply chain and the processing,” said Michael Free, a professor of metallurgical engineering and the principal investigator on the DOE grant. “This project is designed around looking at some alternative unconventional domestic sources for these materials.”. Team members included graduate students Haley Coe, the lead author, and Diego Fernandez, a research professor who runs the lab that tested samples.
Many lanthanide compounds are used in glass and catalysts, as well as magnets, superconductors, phosphors, lasers and luminescent materials. Rare earths also found in everyday technology, such televisions and smartphone screens, medical devices, auto- and fluid catalysts. Carbon-neutral energy technology, including wind turbines, solar panels, electric vehicles, rechargeable batteries and energy-efficient lighting, also require these elements.
The association between coal and REE deposits has been well documented elsewhere, but little data had been previously analyzed relevant to Utah and Colorado’s once busy coal fields, which have fallen on hard times as domestic demand for coal has shriveled. Among a longer-term decline, however, remaining active coal mines in Utah and Colorado report that they can’t mine fast enough in recent years to meet demand and high coal prices.
To gather samples, the team worked directly with mine operators and examined coal seam outcrops and processing waste piles. In some cases, they analyzed drilling cores, both archived cores and recently drilled ones at the mines. The team entered Utah mines to collect rock samples from the underground ramps that connect coal seams.