Rare-earth element

• 1. Introduction

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  The rare-earth elements are a family of 17 soft, silvery-white metals, and the first thing to know about them is that their name is misleading. Cerium, the most plentiful member, makes up 68 parts per million of Earth's crust. That ranks it 25th among all elements and puts it ahead of copper. If these metals are common, why do governments now treat them as strategic prizes? And why did chemists need over a century to sort them out?

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• 2. A Misleading Name

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  The word earth in the name is a relic of an old term for oxides, the chemical form in which these elements first showed up inside minerals. The word rare originally pointed to those unusual minerals. It may also carry the sense of strange or extraordinary, or reflect how exotic the metals seemed when they were discovered.

  None of that means the metals are scarce. The real obstacle is that they never occur as pure metals. They sit in compounds, mixed with one another or with radioactive thorium and, less commonly, uranium, spread thinly as trace impurities. Getting a usable amount at decent purity means processing enormous quantities of raw ore. That is costly and energy intensive.

  In 2016 the chemist Andrea Sella described the paradox. Under analysis the elements are virtually inseparable, because their chemistry is almost identical. Yet in their electronic and magnetic behaviour, each one fills a technological niche that nothing else can. He gave an example from the glassblowing bench. Sella noted that praseodymium and neodymium "can both be embedded inside glass." In his words, they "completely cut out the glare from the flame when one is doing glass-blowing."

  Scandium and yttrium earn a place in the group anyway. They turn up in the same ore deposits as the 15 lanthanides and behave chemically like them. Their electrical and magnetic properties, however, differ.

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• 3. Sorting the Look-Alikes

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  In 1787, Lieutenant Carl Axel Arrhenius found a mineral in a quarry at Ytterby, a village in Sweden. A sample reached Johan Gadolin, a professor at the Royal Academy of Turku. His analysis turned up an unknown oxide, which he named yttria. The black mineral, later called gadolinite, held cerium, yttrium, iron and silicon, among other elements. Four elements would end up named for that single village: yttrium, terbium, erbium and ytterbium.

  Progress was slow, because the chemistry of these metals is so alike. In 1794, the Swedish analytical chemist Anders Gustav Ekeberg extracted beryllium from gadolinite but missed the other elements in it. In 1803, Jöns Jacob Berzelius and Wilhelm Hisinger re-examined a mineral from Bastnäs, near Riddarhyttan. They obtained a white oxide and called it ceria. Martin Heinrich Klaproth found the same oxide independently and named it ochroia. Another 30 years passed before researchers realized that both ores hid further elements.

  In 1839, Carl Gustav Mosander, an assistant to Berzelius, heated the nitrate of ceria and dissolved the product in nitric acid. He named the oxide of the soluble salt lanthana, a name that echoes a Greek word meaning to be hidden. Three more years of work split it into didymia and pure lanthana. In 1842 he divided yttria into three oxides: pure yttria, terbia and erbia. He called the earth giving pink salts terbium, and the one with a yellow peroxide erbium.

  By then six rare earths were known: yttrium, cerium, lanthanum, didymium, erbium and terbium. Then the confusion began. Nils Johan Berlin and Marc Delafontaine repeated the yttria work and found the same substances Mosander had. In 1860, Berlin gave the name erbium to the pink-salt substance, while Delafontaine gave terbium to the yellow one. The names had swapped places. False claims followed, among them J. Lawrence Smith's mosandrium and Delafontaine's philippium and decipium. The total of false discoveries ran to dozens, and some counts exceed a hundred.

  For 30 years nothing new appeared, and the periodic table listed didymium with a molecular mass of 138. In 1879, Delafontaine applied a new physical technique, optical flame spectroscopy, and saw fresh spectral lines in didymia. That same year Paul Émile Lecoq de Boisbaudran isolated samarium from the mineral samarskite. The element took its name from a mine official, Vasili Samarsky-Bykhovets. In 1886, Lecoq de Boisbaudran separated the samaria earth further. Jean Charles Galissard de Marignac reached a similar result straight from samarskite. They named the new element gadolinium, after Johan Gadolin. More spectral clues from William Crookes, Lecoq de Boisbaudran and Eugène-Anatole Demarçay led to europium, which fractional crystallization of the oxides produced in 1901.

  By then no one knew how many rare earths existed, and estimates ran as high as 25. Henry Gwyn Jeffreys Moseley settled the question using X-ray spectra. His work confirmed Niels Bohr's atomic theory while he developed the theory of atomic numbers. It showed that there had to be exactly 15 lanthanides, which exposed a gap at element 61. It also showed that hafnium, element 72, was not a rare earth. Moseley was killed in the First World War in 1915, years before hafnium was discovered. Georges Urbain's claim to have discovered element 72 was therefore untrue.

  The 1940s brought a different breakthrough. During the Manhattan Project, Frank Spedding and others in the United States developed ion-exchange procedures for separating and purifying rare earths. The method was first used on actinides, to pull plutonium-239 and neptunium away from uranium, thorium and actinium in material from nuclear reactors. Plutonium-239 was prized because it is fissile. In 1945, the missing element 61 was finally made synthetically. Promethium, named for the Titan Prometheus who brought fire to mortals, became the last rare earth to be discovered. Industrial use stayed very limited until ion exchange, fractional crystallization and liquid-liquid extraction were developed in the late 1950s and early 1960s.

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• 4. Hidden in Rock

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  Every rare earth except scandium is heavier than iron, so these atoms were forged in supernovae or by the s-process inside asymptotic giant branch stars. Promethium is the odd one out. Its longest-lived isotope has a half-life of 17.7 years, so only about 572 grams exist in the entire crust, arising from spontaneous fission of uranium-238. Nearly all promethium is made in nuclear reactors. Promethium and technetium are the only two elements without stable isotopes that are followed by stable elements of higher atomic number.

  During the Earth's formation, the dense rare earths were drawn into deeper regions, and early melting left most of them in the mantle. A steady shrinking of ionic radius from the light rare earths to the heavy ones, called the lanthanide contraction, shapes where they end up. The larger light ions fit poorly into most rock-forming crystals, so they pass into melts readily. Heavy ones tend to stay behind in the solid residue, especially when garnet is present. The shrinking also explains why holmium, at 0.901 angstroms, is almost identical in size to yttrium at 0.9, which justifies counting yttrium in the group.

  The result has economic weight. Large ore bodies of light rare earths are known around the world and are being worked. Ore bodies of the heavy ones are rarer, smaller and less concentrated. Most of the heavy supply comes from ion-adsorption clay ores in southern China. Tropical rain weathers rock into a thick clay layer, and heavy rare earths cling to it. Of the mineral sources, bastnäsite, monazite and loparite have been the principal ores of cerium and the light lanthanides. Large carbonatite deposits include Mount Weld in Australia, Thor Lake in Canada, Zandkopsdrift in South Africa and Mountain Pass in the United States.

  In 2011, Yasuhiro Kato, a geologist at the University of Tokyo, published results on Pacific Ocean seabed mud. They suggested the mud could hold rich concentrations of rare-earth minerals, and he came to believe that undersea resources are more promising than land-based ones. In January 2013, a Japanese deep-sea research vessel took seven mud cores from 5,600 to 5,800 meters down, about 250 km south of the island of Minami-Tori-Shima. A layer 2 to 4 meters beneath the seabed held up to 0.66% rare-earth oxides. The clays of southern China, which supply the bulk of that country's mine output, grade between 0.05% and 0.5%.

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• 5. Magnets and Light

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  Wind turbines can use up to 600 kg of rare earths in their permanent-magnet generators. An electric vehicle needs 1-2 kg of neodymium and praseodymium. Rare-earth magnets are the strongest in the world, and that strength lets engineers shrink motors and generators. Neodymium-iron-boron magnets are the strongest at ambient temperatures, at ten times the strength of standard ferrite magnets. Above 150 °C, samarium-cobalt magnets take the lead, at six times ferrite strength. Neodymium and samarium also cost less than other rare earths. The same magnets turn up in industrial motors, electric bicycle motors, the small motors in computer hard disks, and magnetic resonance imaging.

  Renewable energy does not drive every element equally. It accounts for under 10% of global dysprosium and neodymium demand. For the rarer praseodymium and terbium, clean energy claims over 30%.

  Light is the other great talent of these metals. Europium is the most common red emitter in phosphors and, in another form, the most common blue. Terbium is the most common green, with a peak at 542 nm. Together with lanthanum, yttrium and cerium, they color energy-saving lamps, LEDs, plasma displays and the old cathode-ray tubes. Crystals of lutetium silicate doped with cerium serve in positron emission tomography.

  Lanthanum chloride drives fluid catalytic cracking, which makes gasoline and diesel. Cerium oxide works in catalytic converters, and ceria is a key abrasive for polishing fine glass. In the United States, more than half of all rare earths go to catalysts. Smartphones absorb 8% of global rare-earth supply. Defense is another use: precision-guided systems need special rare-earth compounds, neodymium magnets are used in missile guidance, and lanthanum sharpens the glass of high-end intelligence camera lenses.

  As of late 2023, global demand for rare earths was expected to grow more than fivefold by 2030.

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• 6. China's Grip

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  Between 1985 and 1995, China raised its share of rare-earth production from 21% to 60%. The causes are attributed to tax reductions and favourable credit, helped by low labour costs and a lack of environmental regulation. Earlier leaders had come and gone. Until 1948, most rare earths came from placer sands in India and Brazil. South Africa's Steenkampskraal mine led in the 1950s, and California's Mountain Pass made the United States the top producer from the 1960s to the 1980s. France produced a great deal in the 1990s. After China undercut world prices in the 1990s, many mines elsewhere closed, and restarting one takes several years.

  In 2009 China announced plans to cut its export quota to 35,000 tons a year for 2010-2015, saying the aim was to conserve scarce resources and protect the environment. It also suspended rare-earth exports to Japan during a territorial dispute. Beijing forced smaller independent miners to merge into state-owned corporations or face closure. At the end of 2010, it set the first-round 2011 export quota at 14,446 tons, a 35% drop from the equivalent 2010 round. In September 2011, it halted three of its eight major rare-earth mines, which produced almost 40% of the national total.

  In March 2012, the United States, the European Union and Japan confronted China at the World Trade Organization. China replied that the restrictions were meant to protect the environment. In August 2012, it announced a further 20% production cut, and the three challengers filed a joint lawsuit. Meanwhile new mines opened in Australia, run by Lynas, and in the United States, run by Molycorp. Prices fell. Dysprosium oxide dropped from US$994 per kg in 2011 to US$265 per kg by 2014. In August 2014, the WTO ruled that China had broken free-trade agreements. By the 5th of January 2015, China had lifted all export quotas, although licences were still required.

  The dominance persisted. In 2017, China produced 81% of the world's rare-earth supply while holding only 36.7% of global reserves. As of 2022, all of the world's heavy rare earths, such as dysprosium, still came from Chinese sources, including the Bayan Obo deposit. By 2025, China dug up 70% of the global supply and processed about 90% of it. It refined nearly all of Myanmar's and Australia's ore, and almost half of American production. The European Union imports around 98% of its use from China.

  In April 2025, after President Donald Trump imposed high tariffs on Chinese goods, China retaliated by restricting sales of seven rare earths to America. In early October 2025 it added further controls. A United States defense procurement restriction scheduled for January 2027 will bar Chinese-origin rare-earth metals and magnets from American defense systems.

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• 7. Beyond China

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  In 2025, a former asbestos mine near the small Brazilian city of Minaçu began producing neodymium, praseodymium, dysprosium and terbium on a commercial scale. It was the first operation outside Asia to do so. Brazil holds 23% of the world's reserves, the second-largest share, and its government is providing nearly $1 billion through the Brazilian Development Bank and the funding agency Finep. The mine's operator, Serra Verde, is controlled by the American investment fund Denham Capital. It digs shallow holes and processes ore with only water and salt, but it exports the minerals to China for processing.

  The Browns Range mine, 160 km south-east of Halls Creek in northern Western Australia, has operated since 2018. It was the first significant dysprosium producer outside China. In October 2025, Australia's prime minister, Anthony Albanese, and President Trump signed a deal on rare earths and other critical minerals. Each country committed at least US$1 billion over six months toward projects worth US$8.5 billion.

  India has been stepping up its own industry, with monazite in coastal and riverine sands across states such as Andhra Pradesh, Odisha and Kerala. Yet it lacks advanced processing skills. India exported only around 18 tonnes of rare-earth minerals between 2015 and 2025, and in 2025 its government launched the National Critical Mineral Mission to build self-reliance.

  Europe has found deposits but little mining. In January 2023, the Swedish state-owned company LKAB announced over 1 million metric tons of rare earths in the Kiruna area. In June 2024, Rare Earths Norway reported 8.8 million metric tons in Telemark, making it Europe's largest known deposit, with the first stage of mining expected to be ready by 2030. As of 2025, however, the European Union had no rare-earth mining at all. Its single operating processing facility is owned by the Canadian company Neo Performance Materials, and lengthy permitting slows new mines.

  Recycling offers another source. In Japan, an estimated 300,000 tons of rare earths sit unused inside old electronics. In France, the Rhodia group is setting up factories in La Rochelle and Saint-Fons to produce 200 tons a year from used fluorescent lamps, magnets and batteries.

  Old waste can also pay. Tailings from 50 years of uranium, shale and loparite mining at Sillamäe, Estonia, contain so many rare-earth oxides that rising prices made extraction viable. The country exports around 3,000 metric tons a year, roughly 2% of world production. Similar resources are suspected in the western United States, where gold-rush-era miners are believed to have thrown away large amounts of rare earths because they had no value at the time.

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• 8. The Price of Digging

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  In Bukit Merah, in Perak, Malaysia, a rare-earth mine run by Asian Rare Earth, a Mitsubishi Chemical subsidiary, closed in 1994. It left continuing environmental and health concerns. Those memories colored the debate when, in early 2011, the Australian company Lynas rushed to finish a US$230 million refinery in the port of Kuantan, on Peninsular Malaysia's east coast. The plant was to refine ore from the Mount Weld mine and was forecast to meet nearly a third of world demand outside China. After protests, the Malaysian government announced restrictions in mid-2011. An independent review by the International Atomic Energy Agency that year, aimed at the radioactive hazards, found the plant compliant with international radiation safety standards. In September 2014, Lynas received a two-year full operating license.

  Malaysia is not alone in worrying. Plans to mine rare earths in Kedah drew concern that the mines could destroy forest reserves and harm water catchment areas. In central Spain, the proposed Matamulas project in Ciudad Real Province was suspended by regional authorities over social and environmental concerns. The co-occurrence of rare earths with radioactive thorium and uranium has pushed some nations to take pollution and human rights more seriously.

  In Kachin State, Myanmar, the costs are starker. In 2021, China imported more than 20,000 metric tons of rare earths from Myanmar, mostly from Kachin, after shutting its own domestic mines because of their environmental impact. Chinese companies and miners are said to set up operations without government permits, working instead with a Border Guard Force militia under the Tatmadaw. Land has been seized from locals. Researchers counted 2,700 mining collection pools scattered across 300 locations in Kachin State, covering an area the size of Singapore, a sharp increase from 2016.

  The elements themselves are not entirely benign. Rare earths have no biological function except in a few specialized enzymes, such as the lanthanide-dependent methanol dehydrogenases in bacteria. Their water-soluble compounds are mildly to moderately toxic, while the insoluble ones are not. Mine tailings have been found to increase rare-earth enrichment in local soil and water. In recent years, published research on the health effects has risen sharply, and scholars are calling for more work to bridge the gaps in the available data.

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