Rare earth elements

Where Found

Mixtures of the rare earth elements are present, but only in small amounts, in most rocks of the Earth. The rare earth elements are more concentrated in rocks of the continents than in those of the ocean basins. The minerals monazite, a phosphate mineral, and bastnäsite, a fluorine-carbonate mineral, form the main ores for the rare earth elements with lower atomic numbers. Xenotime, another phosphate mineral, is mined for its concentration of the rare earth elements with higher atomic numbers. The largest sources of rare earth elements are from bastnäsites mined in China and the United States. Monazite deposits are found in Australia, Brazil, Chile, India, Malaysia, South Africa, Sri Lanka, Thailand, and the United States.

Primary Uses

Mixtures of the rare earth elements are used for breaking down hydrocarbons in petroleum to form more gasoline, to remove impurities from iron and steel, as polishing materials, for carbon arcs, and in metallurgy. Pure rare earth elements are used as coloring agents.

Technical Definition

The rare earth elements (abbreviated REE), or lanthanide elements, are a group of elements from atomic numbers 57 to 71. Their atomic weights range from 138.91 to 174.99. This large group of elements is grouped together because they have similar chemical properties. The names of the rare earth elements, from low to high atomic numbers, are lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium. In addition, the elements scandium and yttrium (atomic numbers 21 and 39, respectively) are sometimes included with the rare earth elements because they have chemical properties similar to those of the rare earth elements. The density of the pure metals ranges from 5.23 to 9.84 grams per cubic centimeter. Melting points for the metals range from 798° to 1,663° Celsius.

Description, Distribution, and Forms

The rare earth elements, because of their similar chemical properties, do not occur as separate individual elements in minerals. Rather, they are fractionated in similar ways within or on the Earth. The rare earth elements are not normally soluble in water, so they are not transported in solution by natural waters.

The rare earth elements are widely distributed in the rocks of the world. The concentrations of some of the rare earth elements are as high as those of copper or zinc. For example, the dark, fine-grained rocks composing much of the ocean floor (called basalts) contain about 3 to 5 parts per million lanthanum, whereas igneous and sedimentary rocks on the continents typically contain 20 to 100 parts per million lanthanum. The rare earth elements are lowest in concentration in carbonate rocks such as limestone.

History

A mineral now called gadolinite was discovered by Johan Gadolin, who subsequently separated an “element” called yttria from gadolinite in 1796. Later, it was discovered that yttria actually consisted of a concentration of the heavy rare earth elements. Another “element” called ceria was separated in the early nineteenth century; ceria was later discovered to consist of a concentration of the light rare earth elements.

By the mid-nineteenth century, individual rare earth element oxides were separated from yttria and ceria by a series of chemical separations and identified after analytical techniques such as the spectrograph were developed.

Obtaining Rare Earth Elements

Overall, China has the world's largest reserves of rare earth elements and dominates the global mining, processing, and refining industry. Monazite and the associated xenotime are mined from beach sands in Brazil, India, Australia, and South Africa. Monazite is weakly magnetic and may be separated from the non-ore minerals by magnetic separation. Bastnäsite is mined in Africa, China, and the United States. It occurs in large amounts at Mountain Pass in California, mixed with the non-ore minerals quartz, barite, and calcite. The ore is crushed, and bastnäsite is concentrated by flotation. The rare earth elements are further concentrated by heating and leaching with hydrochloric acid. Minor amounts of the rare earth elements are also produced as by-products from other ore processing, such as uranium production.

Uses of Rare Earth Elements

Rare earth elements have a wide variety of end uses; modern technology, including consumer electronics, clean energy, military technology, and the medical industry, relies heavily on these elements. They are used in glass-polishing agents, ceramics, computer monitors (phosphors), cellphones, televisions, fluorescent lighting, radar, precision-guided missiles, chemicals, petroleum-refining catalysts, pharmaceuticals, magnets, metallurgy, and laser and scintillator crystals. Renewable and clean energy technologies also rely on rare earth metals, including electric and hybrid cars, wind turbine generators, solar panels, and catalytic converters in vehicles and industrial applications.

Pure europium mixed with yttrium oxides, for example, produces an intense red fluorescence, so the mixture is used in television screens. Pure lanthanum oxide is used to make quality glass for lenses. Rare earth elements are also used in X-rays, magnetic resonance imaging (MRI) scans, contrast agents used in health care, high-quality magnets, artificial diamonds, and superalloys. As a polishing powder, rare earth elements aid in semiconductor manufacturing.

Bibliography

Brouziotis, Antonios Apostolos, et al. "Toxicity of Rare Earth Elements: An Overview on Human Health Impact." Frontiers in Environmental Science, vol. 10, 6 Sept. 2022, doi:10.3389/fenvs.2022.948041. Accessed 22 Nov. 2025.

Delfrey, Keith N., editor. Rare Earths: Research and Applications. Nova Science Publishers, 2008.

Greenwood, N. N., and A. Earnshaw. Chemistry of the Elements. 2nd ed., Butterworth-Heinemann, 1997.

Gschneidner, Karl A., editor. Industrial Applications of Rare Earth Elements: Based on a Symposium Sponsored by the Division of Industrial and Engineering Chemistry at the Second Chemical Congress of the North American Continent (180th ACS National Meeting), Las Vegas, Nevada, August 25-26, 1981. American Chemical Society, 1981.

Gschneider, Karl A., Jr. "Rare-Earth Element." Britannica, 19 Nov. 2025, www.britannica.com/science/rare-earth-element. Accessed 22 Nov. 2025.

"History and Future of Rare Earth Elements." Science History Institute, www.sciencehistory.org/education/classroom-activities/role-playing-games/case-of-rare-earth-elements/history-future. Accessed 22 Nov. 2025.

Kogel, Jessica Elzea, et al., editors. “Rare Earth Elements.” Industrial Minerals and Rocks: Commodities, Markets, and Uses. 7th ed., Society for Mining, Metallurgy, and Exploration, 2006.

Krebs, Robert E. “Lanthanide Series (Rare-Earth Elements): Period 6.” The History and Use of Our Earth’s Chemical Elements: A Reference Guide. 2nd ed., Illustrations by Rae Déjur. Greenwood Press, 2006.

"Rare Earths Statistics and Information." US Geological Survey, www.usgs.gov/centers/national-minerals-information-center/rare-earths-statistics-and-information. Accessed 22 Nov. 2025.

"What Are Rare Earth Elements, and Why Are They Important?" American Geosciences Institute, profession.americangeosciences.org/society/intersections/faq/what-are-rare-earth-elements-and-why-are-they-important. Accessed 22 Nov. 2025.