Are There Rare Earth Elements in Coal Mines?

Research at the University of Utah documented elevated concentrations of rare earth elements (REEs) in active mines in the coal belt of Colorado and Utah. It’s possible that the mines have a secondary resource stream in metals used in renewable energy. The researchers found that rare earth elements are concentrated in fine-grain shale above and below coal seams. The new findings will form the basis for a grant request for an additional $9.4 million in federal funding to continue the research.

The project looks for alternative and unconventional onshore sources for the materials. Phase one was to collect data to understand whether the search was worth pursuing in the West. Researchers analyzed 3,500 samples from 10 mines, four mine waste piles, seven stratigraphically complete cores, and even some coal ash piles near power plants.

They used two methods to record ppm levels of rare earths. One used a hand-held device for quick readings in the field, and the other used Inductively Coupled Plasma-Mass Spectrometry, or ICP-MS, in an on-campus lab.

The Department of Energy has set 300 ppm as the minimum concentration for rare earth mining to be economically viable. Researchers deemed initial concentrations must be greater than 200 ppm to be considered “REE enriched.” The highest prevalence of concentrations were found in coal-adjacent formations of siltstone and shale.

The team has analyzed 11,000 samples so far. The next steps include determining the amount of rare earth ores present.

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