Rare Earth Elements – A Subset of Critical Minerals

Rare earth elements (REEs)—a subset of critical minerals and materials (Figure 1)—are essential materials in a broad range of technologies significant to national security, energy systems, medicine, and consumer products (Figure 2). REEs occur throughout the earth’s crust, commonly at low concentrations (Figure 3^{b,c,d,e,f,g,h,i} and Figure 4^c,d,i,j). They are not found in an isolated form readily available for extraction, but are distributed throughout a variety of minerals, and are also found in coal and coal by-products. REE-bearing mineral deposits are relatively rich in either light rare earth elements (LREEs) or heavy rare earth elements (HREEs), with LREEs generally more abundant. The environmental footprint created by conventional REE processing techniques has long been a key consideration in determining where these elements are mined and subsequently produced.

REEs typically occur at low concentrations throughout the Earth’s crust. REEs are not found in an isolated form readily available for extraction but are distributed throughout a variety of minerals as monazite, bastnaesite, and xenotime. They can also be found in coal-based resources. REE-bearing mineral deposits are relatively rich in either light rare earth elements (LREEs) or heavy rare earth elements (HREEs), with the LREEs being more abundant (Figure 3).

As nonfuel minerals or materials, CMM are essential to our modern economy and national security and have a supply chain vulnerable to disruption. In addition to REEs, CMM include aluminum (bauxite), antimony (Sb), arsenic (As), barite (BaSO4), beryllium (Be), bismuth (Bi), cesium (Cs), chromium (Cr), cobalt Cr), fluorspar (CaF2), gallium (Ga), germanium (Ge), graphite (natural), hafnium (Hf), helium (He), indium (In), lithium (Li), magnesium (Mg), manganese (Mn), niobium (Nb), platinum group metals, potash, the REEs group, rhenium (Re), rubidium (Rb), scandium (Sc), strontium (Sr), tantalum (Ta), tellurium (Te), tin (Sn), titanium (Ti), tungsten (W), uranium (U), vanadium (V), and zirconium (Zr). The average mean CMM concentration in carbon ore and select alternate materials is shown in Figure 4.

Dating back to the 1960s, the United States was the leading global producer of REEs until approximately 1998 when United States production significantly declined and China became the dominant global supplier (Figure 5).^k The United States currently imports over 74% of its rare earth oxides (REOs) directly from China, with portions of the remainder indirectly sourced from China through other countries.

Since 2011, China’s decision to restrict exports and favor its own domestic industries has resulted in REE price volatility. Consequently, rising concern among industrialized nations has driven the resurgence of global interest in REE mineral exploration and extraction, and related research on supply, demand, utilization, recycling, reuse, and substitution. Several new domestic commercial REE projects are in various stages of planning and development and are focused on diversifying supply. In contrast, new efforts to purify and refine REEs are limited. Overall, the United States is heavily reliant on foreign imports to supply REEs and associated compounds as well as intermediate and end-products containing rare earths such as permanent magnets, motors, and turbines.

The importance of REEs cannot be understated. With hundreds of end-uses and applications ranging from clean energy production, oil refining, electronics, batteries for electric vehicles, phosphors for lighting, to defense technologies, rare earths are critical to the stability and growth of modern society. Secure, reliable, and sustainable domestic supplies of these strategic resources is both essential to the continued health of U.S. energy and electronics industries and an important contributor to national security. Projects funded through the Department of Energy’s Critical Minerals and Materials Program directly contribute to rebuilding U.S. leadership in extraction and processing technologies, and reestablishing secure domestic supplies of rare earths.

^a DOE. (July 28, 2023). Notice of Final Determination on 2023 DOE Critical Materials List. Retrieved from https://www.energy.gov/sites/default/files/2023-07/preprint-frn-2023-critical-materials-list.pdf

^b DOE. (2017). Report to Congress: Report on Rare Earth Elements from Coal and Coal Byproducts. Retrieved from https://www.energy.gov/sites/prod/files/2018/01/f47/EXEC-2014-000442%20-%20for%20Conrad%20Regis%202.2.17.pdf

^cFinkelman, R. (1993). Trace and Minor Elements in Coal, in Organic Geochemistry: Principles and Applications. (M.H. Engel, & S.A. Macko, Eds.) Boston, MA: Springer US.

^d Ketris, M., & Yudovich, Y. (2009). Estimations of Clarkes for Carbonaceous biolithes: World averages for trace element contents in black shales and coals. International Journal of Coal Geology, 78(2), pp. 135-148.

^e NETL. (September 2020). NETL Rare Earth Element and Critical Minerals Virtual Annual Review Meeting.

^f USGS. (2016, February). 2013 Minerals Yearbook: Rare Earths. Retrieved from https://d9-wret.s3.us-west-2.amazonaws.com/assets/palladium/production/mineral-pubs/rare-earth/myb1-2013-raree.pdf

^g Hoatson, D. M., Jaireth, S., & Miezitis, Y. (2011). The major rare-earth-element deposits of Australia: geological setting, exploration, and resources, Chapter 3: Geological Settings of Rare-Earth-Element Deposits in Australia. Geoscience Australia. Retrieved from http://www.ga.gov.au/webtemp/image_cache/GA19677.pdf

^h Birdwell, J. E. (2012). Review of Rare Earth Element Concentrations in Oil Shales of the Eocene Green River Formation. U.S. Geological Survey Open-File Report 2012–1016. Retrieved from https://pubs.usgs.gov/of/2012/1016/report/OF12-1016.pdf

ⁱ Liang, H., Zhang, P., Jin, Z., & DePaoli, D. (2017). Rare-earth leaching from Florida phosphate rock in wet-process phosphoric acid production. Minerals & Metallurgical Processing, 34(3), pp. 146-153.

^j Gladney, E., O'Malley, B., Roelandts, I., & Gills, T. (1987). Compilation of elemental concentration data for NBS clinical, biological, geological, and environmental Standard Reference Materials. Gaithersburg, MD: NIST.

^k USGS. Rare Earths, Statistics and Information Mineral Commodity Summaries