Analysis led by the College of Utah has documented elevated concentrations of uncommon earth parts (REEs) in lively coal mines rimming the Uinta coal belt of Colorado and Utah, suggesting a brand new avenue for sourcing these supplies that play a vital position in renewable vitality and different high-tech methods.
“The model is: if you’re already moving rock, could you move a little more rock for resources towards energy transition?” mentioned Lauren Birgenheier, an affiliate professor of geology and geophysics. “In those areas, we’re finding that the rare earth elements are concentrated in fine-grain shale units, the muddy shales that are above and below the coal seams.”
This analysis was carried out in partnership with the Utah Geological Survey and Colorado Geological Survey as a part of the Division of Power-funded Carbon Ore, Uncommon Earth and Crucial Minerals challenge, or CORE-CM. The brand new findings will kind the idea for a grant request of an extra $9.4 million in federal funding to proceed the analysis.
Whereas these metals are essential for U.S. manufacturing, particularly in high-end applied sciences, they’re largely sourced from abroad.
“When we talk about them as ‘critical minerals,’ a lot of the criticality is related to the supply chain and the processing,” mentioned Michael Free, a professor 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.”
The affiliation between coal and REE deposits has been properly documented elsewhere, however little knowledge had been beforehand gathered or analyzed in Utah and Colorado’s coal fields.
“The goal of this phase-one project was to collect additional data to try and understand whether this was something worth pursuing in the West,” mentioned examine co-author Michael Vanden Berg, Power and Minerals Program Supervisor on the Utah Geological Survey. “Is there rare earth element enrichment in these rocks that could provide some kind of byproduct or value added to the coal mining industry?”
Researchers analyzed 3,500 samples from 10 mines, 4 mine waste piles, seven stratigraphically full cores, and even some coal ash piles close to energy vegetation.
“The coal itself is not enriched in rare earth elements,” Vanden Berg mentioned. “There’s not going to be a byproduct from mining the coal, but for a company mining the coal seam, could they take a couple feet of the floor at the same time? Could they take a couple feet of the ceiling? Could there be potential there? That’s the direction that the data led us.”
The group deployed two completely different strategies to file ranges of uncommon earths, expressed in components per million, or ppm, within the samples. One was a hand-held machine for fast readings within the area, the opposite used Inductively Coupled Plasma-Mass Spectrometry, or ICP-MS, in an on-campus lab.
“We’re mostly using this portable x-ray fluorescence device, which is an analysis gun that we hold to the rock for two minutes, and it only gives us five or six of the 17 rare earth elements,” Birgenheier mentioned. If samples confirmed concentrations larger than 200 ppm, they ran a extra full evaluation utilizing the extra pricey mass spectrometry gear.
The Division of Power has set 300 ppm because the minimal focus for uncommon earth mining to be doubtlessly economically viable. However for the examine, researchers deemed concentrations better than 200 ppm to be thought-about “REE enriched.”
The examine discovered the very best prevalence of such concentrations in coal-adjacent formations of siltstone and shale, whereas sandstone and the coal itself had been principally devoid of uncommon earths.
The group has analyzed 11,000 samples so far, way over had been used within the printed examine. Subsequent steps embrace figuring out how a lot uncommon earth ore is current, prone to be accomplished with colleagues on the College of Wyoming and New Mexico Institute of Mining and Expertise.
