Rare earth elements (REEs)

The rare-earth elements (REE), also called rare-earth metals, or rare earths, are a set of 17 nearly indistinguishable lustrous silvery-white soft heavy metals. The 15 lanthanides (or lanthanoids), along with scandium, and yttrium, are usually included as rare earths. Compounds containing rare-earth elements have diverse applications in electrical and electronic components, lasers, glass, magnetic materials, and industrial processes. Rare-earths are to be distinguished from critical minerals, which are materials of strategic or economic importance that are defined differently by different countries, and rare-earth minerals, which are minerals that contain one or more rare-earth elements as major metal constituents.

The term "rare-earth" is a misnomer, because they are not actually scarce, but because they are found only in compounds, not as pure metals, and are difficult to isolate and purify. REEs are relatively plentiful in the entire Earth's crust (cerium being the 25th-most-abundant element at 68 parts per million, more abundant than copper), but in practice they are spread thinly as trace impurities, so to obtain rare earths at usable purity requires processing enormous amounts of raw ore which is costly and energy intensive. 

Scandium and yttrium are considered rare-earth elements because they tend to occur in the same ore deposits as the lanthanides and exhibit similar chemical properties, but have different electrical and magnetic properties. Promethium does not occur naturally in the Earth's crust, except for a trace amount generated by spontaneous fission of uranium-238. All isotopes of promethium are radioactive.

REEs are often found in minerals with thorium, and less commonly uranium. The co-occurrence of rare earth elements with radioactive mining deposits has spurred some nations to have greater consciousness about pollution and human rights considerations.

Because of their geochemical properties, rare-earth elements are typically dispersed and not often found concentrated in rare-earth minerals. Consequently, economically exploitable ore deposits are sparse. The first rare-earth mineral discovered (1787) was gadolinite, a black mineral composed of cerium, yttrium, iron, silicon, and other elements. This mineral was extracted from a mine in the village of Ytterby in Sweden. Four of the rare-earth elements bear names derived from this single location. Commercial production in modern times describes the reserves of the rare-earth elements in terms of "rare-earth oxides" (REOs) containing mixtures of various rare-earth elements in oxide compounds.

The uses, applications, and demand for rare-earth elements have expanded over the years. In 2015, most REEs were being used for catalysts and magnets. The global move towards renewable energy technologies, such as electric vehicles (EVs) and wind turbines, along with advanced electronics, defence applications, and consumer electronics such as smartphones, has caused increased demand for REEs.

REE extraction and processing can result in anthropogenic environmental enrichment. Effects of REE pollution on human and environmental health are still being explored. In recent years, there has been a sharp increase in published research on the health impacts as scholars call for more work to bridge gaps in available data. 

China dominates the rest of the world in terms of REE reserves and production; in 2019, it supplied around 90% of the global demand for the 17 rare-earth powders. The Chinese government has placed restrictions on its supply and sales of REEs since around 2010 for various reasons. After United States President Donald Trump escalated the trade war with China in 2025, China introduced further restrictions, leading other countries with known reserves to step up their exploration and production efforts. As of 2025, the US and Australia produce the second- and third-highest amounts of REEs, but Brazil has the second-largest reserves of the metals. A U.S. defense procurement restriction is scheduled to take effect in January 2027, prohibiting the use of Chinese-origin rare-earth metals and magnets in U.S. defense systems.