Therare-earth elements (REE), also called therare-earth metals orrare earths, and sometimes thelanthanides or lanthanoids (althoughscandium andyttrium, which do not belong to this series, are usually included as rare earths),[1] are a set of 17 nearly indistinguishable lustrous silvery-white softheavy metals. Compounds containing rare earths have diverse applications in electrical and electronic components,lasers, glass, magnetic materials, and industrial processes.The term "rare-earth" is amisnomer because they are not actually scarce, but historically it took a long time to isolate these elements.[2][3]They are relatively plentiful in the entireEarth's crust (cerium being the25th-most-abundant element at 68 parts per million, more abundant thancopper), 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 at great expense.
Scandium and yttrium are considered rare-earth elements because they tend to occur in the sameore deposits as the lanthanides and exhibit similar chemical properties, but have different electrical andmagnetic properties.[4][5]
These metals tarnish slowly in air at room temperature and react slowly with cold water to form hydroxides, liberatinghydrogen. They react with steam to form oxides and ignite spontaneously at a temperature of 400 °C (752 °F). These elements and their compounds have no biological function other than in several specialized enzymes, such as inlanthanide-dependent methanol dehydrogenases in bacteria.[6] The water-soluble compounds are mildly to moderately toxic, but the insoluble ones are not.[7] All isotopes ofpromethium are radioactive, and it does not occur naturally in the earth's crust, except for a trace amount generated byspontaneous fission ofuranium-238. They are often found inminerals withthorium, and less commonlyuranium.
Because of theirgeochemical properties, rare-earth elements are typically dispersed and not often found concentrated inrare-earth minerals. Consequently, economically exploitableore deposits are sparse.[8] The first rare-earth mineral discovered (1787) wasgadolinite, a black mineral composed of cerium, yttrium, iron, silicon, and other elements. This mineral was extracted from a mine in the village ofYtterby inSweden. Four of the rare-earth elements bear names derived from this single location.
A table listing the 17 rare-earth elements, theiratomic number and symbol, the etymology of their names, and their main uses (see alsoApplications of lanthanides) is provided here. Some of the rare-earth elements are named after the scientists who discovered them, or elucidated their elemental properties, and some after the geographical locations where discovered.
after the village ofYtterby, Sweden, where the first rare-earth ore was discovered.
Yttrium aluminium garnet (YAG) laser, yttrium vanadate (YVO4) as host for europium in television red phosphor,YBCOhigh-temperature superconductors,yttria-stabilized zirconia (YSZ) (used intooth crowns; as refractory material - in metal alloys used in jet engines, and coatings of engines and industrial gas turbines;electroceramics - for measuring oxygen and pH of hot water solutions, i.e. in fuel cells; ceramic electrolyte - used insolid oxide fuel cell; jewelry - for its hardness and optical properties; do-it-yourself high temperature ceramics and cements based on water),yttrium iron garnet (YIG)microwave filters,[11] energy-efficient light bulbs (part of triphosphor white phosphor coating in fluorescent tubes, CFLs and CCFLs, and yellow phosphor coating in white LEDs),[12]spark plugs, gas mantles, additive to steel, aluminium and magnesium alloys,cancer treatments, camera andrefractive telescope lenses (due to high refractive index and very low thermal expansion), battery cathodes (LYP)
A mnemonic for the names of the sixth-row elements in order is "Lately college parties never produce sexy European girls that drink heavily even though you look".[15]
Rare earths were mainly discovered as components of minerals. The term "rare" refers to these rarely found minerals and "earth" comes from an old name for oxides, the chemical form for these elements in the mineral.[16]: 5 The adjective "rare" may also mean strange or extraordinary.[17]: 12 In 1787, a mineral discovered by LieutenantCarl Axel Arrhenius at a quarry in the village ofYtterby, Sweden,[16]: 9 reachedJohan Gadolin, aRoyal Academy of Turku professor, and his analysis yielded an unknownoxide which he calledyttria.[18]
Anders Gustav Ekeberg isolatedberyllium from the gadolinite but failed to recognize other elements in the ore. After this discovery in 1794, a mineral fromBastnäs nearRiddarhyttan, Sweden, which was believed to be aniron–tungsten mineral, was re-examined byJöns Jacob Berzelius andWilhelm Hisinger. In 1803, they obtained a white oxide and called itceria.Martin Heinrich Klaproth independently discovered the same oxide and called itochroia. It took another 30 years for researchers to determine that other elements were contained in the two ores ceria and yttria. The similarity of the rare-earth metals' chemical properties made their separation difficult.
In 1839,Carl Gustav Mosander, an assistant of Berzelius, separated ceria by heating the nitrate and dissolving the product innitric acid. He called the oxide of the soluble saltlanthana. It took him three more years to separate the lanthana further intodidymia and pure lanthana. Didymia, although not further separable by Mosander's techniques, was in fact still a mixture of oxides.
In 1842, Mosander separated the yttria into three oxides: pure yttria, terbia, and erbia. All the names are derived from the town name "Ytterby". The earth giving pink salts he calledterbium. The one that yielded yellow peroxide he callederbium.[19]By then the number of known rare-earth elements had reached six: yttrium, cerium, lanthanum, didymium, erbium, and terbium.
Nils Johan Berlin andMarc Delafontaine tried also to separate the crude yttria and found the same substances that Mosander obtained. In 1860, Berlin named the substance giving pink saltserbium. Delafontaine named the substance with the yellow peroxide,terbium. This confusion led to several false claims of new elements, such as themosandrium ofJ. Lawrence Smith, or thephilippium anddecipium of Delafontaine. Due to the difficulty in separating the metals, and determining the separation is complete, the total number of false discoveries was dozens,[20][21] with some putting the total number of discoveries at over a hundred.[22]
There were no further discoveries for 30 years, and the elementdidymium was listed in the periodic table of elements with a molecular mass of 138. In 1879,Delafontaine used the new physical process ofoptical flame spectroscopy and found several new spectral lines in didymia. Also in 1879,Paul Émile Lecoq de Boisbaudran isolated the new elementsamarium from the mineralsamarskite.
In 1886, the samaria earth was further separated by Lecoq de Boisbaudran. A similar result was obtained byJean Charles Galissard de Marignac by direct isolation from samarskite. They named the elementgadolinium afterJohan Gadolin, and its oxide was named "gadolinia".
In 1839, the third source for rare earths became available. This is a mineral similar to gadolinite calleduranotantalum, now called "samarskite", an oxide of a mixture of elements such as yttrium, ytterbium, iron, uranium, thorium, calcium, niobium, and tantalum. This mineral fromMiass in the southernUral Mountains was documented byGustav Rose. The Russian chemist R. Harmann proposed that a new element he called "ilmenium" should be present in this mineral, but later,Christian Wilhelm Blomstrand, Galissard de Marignac, andHeinrich Rose found onlytantalum andniobium (columbium) in it.
The exact number of rare-earth elements that existed was highly unclear, and a maximum number of 25 was estimated. UsingX-ray spectraHenry Gwyn Jeffreys Moseley confirmed the atomic theory ofNiels Bohr and simultaneously developed the theory of atomic numbers for the elements.[23] Moseley found that the exact number of lanthanides had to be 15, revealing a missing element,element 61, a radioactive element with a half-life of 18 years.[24]
Using these facts about atomic numbers from X-ray crystallography, Moseley also showed thathafnium (element 72) would not be a rare-earth element. Moseley was killed inWorld War I in 1915, years before hafnium was discovered. Hence, the claim ofGeorges Urbain that he had discovered element 72 was untrue. Hafnium is an element that lies in the periodic table immediately belowzirconium, and hafnium and zirconium have very similar chemical and physical properties.
The principal sources of rare-earth elements are the mineralsbastnäsite (RCO3F, where R is a mixture of rare-earth elements),monazite (XPO4, where X is a mixture of rare-earth elements and sometimes thorium), andloparite ((Ce,Na,Ca)(Ti,Nb)O3), and thelateritic ion-adsorptionclays. Despite their high relative abundance,rare-earth minerals are more difficult to mine and extract than equivalent sources oftransition metals, due in part to their similar chemical properties, making the rare-earth elements relatively expensive. Their industrial use was very limited until efficient separation techniques were developed, such asion exchange, fractional crystallization, andliquid–liquid extraction in the late 1950s and early 1960s.[25]
Someilmenite concentrates contain small amounts of scandium and other rare-earth elements, which could be analysed byX-ray fluorescence (XRF).[26]
Before the time thation exchange methods andelution were available, the separation of the rare earths was primarily achieved by repeatedprecipitation orcrystallization. In those days, the first separation was into two main groups, the cerium earths (lanthanum, cerium, praseodymium, neodymium, and samarium) and the yttrium earths (scandium, yttrium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium). Europium, gadolinium, and terbium were either considered as a separate group of rare-earth elements (the terbium group), or europium was included in the cerium group, and gadolinium and terbium were included in the yttrium group. In the latter case, the f-block elements are split into half: the first half (La–Eu) form the cerium group, and the second half (Gd–Yb) together with group 3 (Sc, Y, Lu) form the yttrium group.
The reason for this division arose from the difference insolubility of rare-earth double sulfates with sodium and potassium. The sodium double sulfates of the cerium group are poorly soluble, those of the terbium group slightly, and those of the yttrium group are very soluble.[27] Sometimes, the yttrium group was further split into the erbium group (dysprosium, holmium, erbium, and thulium) and the ytterbium group (ytterbium and lutetium), but today the main grouping is between the cerium and the yttrium groups.[28] Today, the rare-earth elements are classified as light or heavy rare-earth elements, rather than in cerium and yttrium groups.
The classification of rare-earth elements is inconsistent between authors.[17] The most common distinction between rare-earth elements is made byatomic numbers. Those with low atomic numbers are referred to as light rare-earth elements (LREE), those with high atomic numbers are the heavy rare-earth elements (HREE), and those that fall in between are typically referred to as the middle rare-earth elements (MREE).[29] Commonly, rare-earth elements with atomic numbers 57 to 61 (lanthanum to promethium) are classified as light and those with atomic numbers 62 and greater are classified as heavy rare-earth elements.[30]
Increasing atomic numbers between light and heavy rare-earth elements and decreasingatomic radii throughout the series causes chemical variations.[30] Europium is exempt of this classification as it has two valence states: Eu2+ and Eu3+.[30] Yttrium is grouped as a heavy rare-earth element due to chemical similarities.[31] The break between the two groups is sometimes put elsewhere, such as between elements 63 (europium) and 64 (gadolinium).[32] The actual metallic densities of these two groups overlap, with the "light" group having densities from 6.145 (lanthanum) to 7.26 (promethium) or 7.52 (samarium) g/cc, and the "heavy" group from 6.965 (ytterbium) to 9.32 (thulium), as well as including yttrium at 4.47. Europium has a density of 5.24.
Due to their chemical similarity, the concentrations of rare earths in rocks are only slowly changed by geochemical processes, making their proportions useful forgeochronology and dating fossils.
In their oxides, most rare-earth elements only have a valence of 3 and formsesquioxides (cerium formsCeO2). Five different crystal structures are known, depending on the element and the temperature. The X-phase and the H-phase are only stable above 2000 K. At lower temperatures, there are the hexagonal A-phase, the monoclinic B-phase, and the cubic C-phase, which is the stable form at room temperature for most of the elements. The C-phase was once thought to be inspace groupI213 (no. 199),[33] but is now known to be in space groupIa3 (no. 206).
The structure is similar to that offluorite orcerium dioxide (in which the cations form aface-centred cubic lattice and the anions sit inside the tetrahedra of cations), except that one-quarter of the anions (oxygen) are missing. Theunit cell of these sesquioxides corresponds to eight unit cells of fluorite or cerium dioxide, with 32 cations instead of 4. This is called thebixbyite structure, as it occurs in a mineral of that name ((Mn,Fe)2O3).[34]
The abundance of elements in Earth's crust per million Si atoms (y axis is logarithmic)
As seen in the chart, rare-earth elements are found on Earth at similar concentrations to many common transition metals. The most abundant rare-earth element iscerium, which is actually the 25th most abundant element inEarth's crust, having 68 parts per million (about as common as copper). The exception is the highly unstable and radioactivepromethium "rare earth" is quite scarce. The longest-lived isotope of promethium has a half-life of 17.7 years, so the element exists in nature in only negligible amounts (approximately 572 g in the entire Earth's crust).[35] Promethium is one of the two elements that do not have stable (non-radioactive) isotopes and are followed by (i.e. with higher atomic number) stable elements (the other beingtechnetium).
The rare-earth elements are often found together. During the sequentialaccretion of the Earth, the dense rare-earth elements were incorporated into the deeper portions of the planet. Early differentiation of molten material largely incorporated the rare earths intomantle rocks.[36] Thehigh field strength[clarification needed] and largeionic radii of rare earths make them incompatible with the crystal lattices of most rock-forming minerals, so REE will undergo strong partitioning into a melt phase if one is present.[36]
REE are chemically very similar and have always been difficult to separate, but the gradual decrease in ionic radius from light REE (LREE) to heavy REE (HREE), called thelanthanide contraction, can produce a broad separation between light and heavy REE. The larger ionic radii of LREE make them generally more incompatible than HREE in rock-forming minerals, and will partition more strongly into a melt phase, while HREE may prefer to remain in the crystalline residue, particularly if it contains HREE-compatible minerals likegarnet.[36][37] The result is that all magma formed from partial melting will always have greater concentrations of LREE than HREE, and individual minerals may be dominated by either HREE or LREE, depending on which range of ionic radii best fits the crystal lattice.[36]
Among the anhydrous rare-earth phosphates, it is the tetragonal mineralxenotime that incorporates yttrium and the HREE, whereas the monoclinicmonazite phase incorporates cerium and the LREE preferentially. The smaller size of the HREE allows greater solid solubility in the rock-forming minerals that make up Earth's mantle, and thus yttrium and the HREE show less enrichment in Earth's crust relative tochondritic abundance than does cerium and the LREE.[38]
This has economic consequences: large ore bodies of LREE are known around the world and are being exploited. Ore bodies for HREE are more rare, smaller, and less concentrated. Most of the current supply of HREE originates in the "ion-absorption clay" ores of Southern China. Some versions provide concentrates containing about 65% yttrium oxide, with the HREE being present in ratios reflecting theOddo–Harkins rule: even-numbered REE at abundances of about 5% each, and odd-numbered REE at abundances of about 1% each. Similar compositions are found in xenotime or gadolinite.[38]
Well-known minerals containing yttrium, and other HREE, include gadolinite, xenotime,samarskite,euxenite,fergusonite, yttrotantalite, yttrotungstite, yttrofluorite (a variety offluorite), thalenite, andyttrialite. Small amounts occur inzircon, which derives its typical yellow fluorescence from some of the accompanying HREE. Thezirconium mineraleudialyte, such as is found in southernGreenland, contains small but potentially useful amounts of yttrium. Of the above yttrium minerals, most played a part in providing research quantities of lanthanides during the discovery days.Xenotime is occasionally recovered as a byproduct of heavy-sand processing, but is not as abundant as the similarly recoveredmonazite (which typically contains a few percent of yttrium). Uranium ores from Ontario have occasionally yielded yttrium as a byproduct.[38]
Enriched deposits of rare-earth elements at the surface of the Earth,carbonatites andpegmatites, are related to alkalineplutonism, an uncommon kind of magmatism that occurs in tectonic settings where there is rifting or that are nearsubduction zones.[37] In a rift setting, the alkaline magma is produced by very small degrees of partial melting (<1%) of garnet peridotite in theupper mantle (200 to 600 km depth).[37] This melt becomes enriched in incompatible elements, like the rare-earth elements, by leaching them out of the crystalline residue. The resultant magma rises as adiapir, ordiatreme, along pre-existing fractures, and can be emplaced deep inthe crust, or erupted at the surface.[36][37]
Typical REE enriched deposits types forming in rift settings are carbonatites, and A- and M-Type granitoids.[36][37] Near subduction zones, partial melting of the subducting plate within theasthenosphere (80 to 200 km depth) produces a volatile-rich magma (high concentrations of CO2 and water), with high concentrations of alkaline elements, and high element mobility that the rare earths are strongly partitioned into.[36] This melt may also rise along pre-existing fractures, and be emplaced in the crust above the subducting slab or erupted at the surface. REE-enriched deposits forming from these melts are typically S-Type granitoids.[36][37]
Alkaline magmas enriched with rare-earth elements include carbonatites, peralkaline granites (pegmatites), andnepheline syenite.Carbonatites crystallize from CO2-rich fluids, which can be produced by partial melting of hydrous-carbonatedlherzolite to produce a CO2-rich primary magma, byfractional crystallization of an alkaline primary magma, or by separation of a CO2-rich immiscible liquid from.[36][37] These liquids are most commonly forming in association with very deep Precambriancratons, like the ones found in Africa and the Canadian Shield.[36]
Ferrocarbonatites are the most common type of carbonatite to be enriched in REE, and are often emplaced as late-stage,brecciated pipes at the core of igneous complexes. They consist of fine-grained calcite and hematite, sometimes with significant concentrations of ankerite and minor concentrations of siderite.[36][37] Large carbonatite deposits enriched in rare-earth elements include Mount Weld in Australia, Thor Lake in Canada, Zandkopsdrift in South Africa, andMountain Pass in the USA.[37]
Peralkaline granites (A-Type granitoids) have very high concentrations of alkaline elements and very low concentrations of phosphorus; they are deposited at moderate depths in extensional zones, often as igneous ring complexes, or as pipes, massive bodies, and lenses.[36][37] These fluids have very low viscosities and high element mobility, which allows for the crystallization of large grains, despite a relatively short crystallization time upon emplacement; their large grain size is why these deposits are commonly referred to as pegmatites.[37]
Economically viable pegmatites include Niobium-Yttrium-Fluorine (NYF) types enriched in Yttrium and other rare-earth minerals, with REE-rich deposits found at Strange Lake in Canada and Khaladean-Buregtey in Mongolia.[37] Nepheline syenite (M-Type granitoids) deposits are 90% feldspar and feldspathoid minerals. They are deposited in small, circular massifs and contain high concentrations ofrare-earth-bearing accessory minerals.[36][37] For the most part, these deposits are small but important examples include Illimaussaq-Kvanefeld in Greenland, and Lovozera in Russia.[37]
Rare-earth elements can also be enriched in deposits by secondary alteration either by interactions with hydrothermal fluids or meteoric water or by erosion and transport of resistate REE-bearing minerals.Argillization of primary minerals enriches insoluble elements by leaching out silica and other soluble elements, recrystallizing feldspar into clay minerals such kaolinite, halloysite, and montmorillonite. In tropical regions where precipitation is high, weathering forms a thick argillized regolith, this process is called supergene enrichment and produceslaterite deposits. Heavy rare-earth elements are incorporated into the residual clay by absorption. This kind of deposit is only mined for REE in Southern China, where the majority of global heavy rare-earth element production occurs. REE-laterites do form elsewhere, including over the carbonatite at Mount Weld in Australia. REE may also be extracted from placer deposits if the sedimentary parent lithology contains REE-bearing, heavy resistate minerals.[37]
In 2011, Yasuhiro Kato, a geologist at theUniversity of Tokyo who led a study of Pacific Ocean seabed mud, published results indicating the mud could hold rich concentrations of rare-earth minerals. The deposits, studied at 78 sites, came from "[h]ot plumes from hydrothermal vents pull[ing] these materials out of seawater and deposit[ing] them on the seafloor, bit by bit, over tens of millions of years. One square patch of metal-rich mud 2.3 kilometers wide might contain enough rare earths to meet most of the global demand for a year, Japanese geologists report inNature Geoscience." "I believe that rare[-]earth resources undersea are much more promising than on-land resources," said Kato. "[C]oncentrations of rare earths were comparable to those found in clays mined in China. Some deposits contained twice as much heavy rare earths such as dysprosium, a component of magnets in hybrid car motors."[38][39]
The global demand for rare-earth elements (REEs) is expected to increase more than fivefold by 2030.[40][41]
The REE geochemical classification is usually done on the basis of theiratomic weight. One of the most common classifications divides REE into 3 groups: light rare earths (LREE - from57La to60Nd), intermediate (MREE - from62Sm to67Ho) and heavy (HREE - from68Er to71Lu). REE usually appear as trivalent ions, except for Ce and Eu which can take the form of Ce4+ and Eu2+ depending on the redox conditions of the system. Consequentially, REE are characterized by a substantial identity in their chemical reactivity, which results in a serial behaviour during geochemical processes rather than being characteristic of a single element of the series. Sc, Y, and Lu can be electronically distinguished from the other rare earths because they do not havef valence electrons, whereas the others do, but the chemical behaviour is almost the same.
A distinguishing factor in the geochemical behaviour of the REE is linked to the so-called "lanthanide contraction" which represents a higher-than-expected decrease in the atomic/ionic radius of the elements along the series. This is determined by the variation of theshielding effect towards the nuclear charge due to the progressive filling of the 4f orbital which acts against the electrons of the 6s and 5d orbitals. The lanthanide contraction has a direct effect on the geochemistry of the lanthanides, which show a different behaviour depending on the systems and processes in which they are involved.[42]
The effect of the lanthanide contraction can be observed in the REE behaviour both in a CHARAC-type geochemical system (CHArge-and-RAdius-Controlled[42]) where elements with similar charge and radius should show coherent geochemical behaviour, and in non-CHARAC systems, such as aqueous solutions, where the electron structure is also an important parameter to consider as the lanthanide contraction affects theionic potential. A direct consequence is that, during the formation of coordination bonds, the REE behaviour gradually changes along the series. Furthermore, the lanthanide contraction causes the ionic radius of Ho3+ (0.901 Å) to be almost identical to that of Y3+ (0.9 Å), justifying the inclusion of the latter among the REE.
The application of rare-earth elements to geology is important to understanding the petrological processes ofigneous,sedimentary andmetamorphic rock formation. Ingeochemistry, rare-earth elements can be used to infer the petrological mechanisms that have affected a rock due to the subtleatomic size differences between the elements, which causes preferentialfractionation of some rare earths relative to others depending on the processes at work.
The geochemical study of the REE is not carried out on absolute concentrations – as it is usually done with other chemical elements – but on normalized concentrations in order to observe their serial behaviour. In geochemistry, rare-earth elements are typically presented in normalized "spider" diagrams, in which concentration of rare-earth elements are normalized to a reference standard and are then expressed as the logarithm to the base 10 of the value.
Commonly, the rare-earth elements are normalized tochondritic meteorites, as these are believed to be the closest representation ofunfractionated Solar System material. However, other normalizing standards can be applied depending on the purpose of the study. Normalization to a standard reference value, especially of a material believed to be unfractionated, allows the observed abundances to be compared to the initial abundances of the element. Normalization also removes the pronounced 'zig-zag' pattern caused by the differences in abundance between even and oddatomic numbers. Normalization is carried out by dividing the analytical concentrations of each element of the series by the concentration of the same element in a given standard, according to the equation:
wheren indicates the normalized concentration, the analytical concentration of the element measured in the sample, and the concentration of the same element in the reference material.[43]
It is possible to observe the serial trend of the REE by reporting their normalized concentrations against the atomic number. The trends that are observed in "spider" diagrams are typically referred to as "patterns", which may be diagnostic of petrological processes that have affected the material of interest.[29]
According to the general shape of the patterns or thanks to the presence (or absence) of so-called "anomalies", information regarding the system under examination and the occurring geochemical processes can be obtained. The anomalies represent enrichment (positive anomalies) or depletion (negative anomalies) of specific elements along the series and are graphically recognizable as positive or negative "peaks" along the REE patterns. The anomalies can be numerically quantified as the ratio between the normalized concentration of the element showing the anomaly and the predictable one based on the average of the normalized concentrations of the two elements in the previous and next position in the series, according to the equation:
where is the normalized concentration of the element whose anomaly has to be calculated, and the normalized concentrations of the respectively previous and next elements along the series.
The rare-earth elements patterns observed in igneous rocks are primarily a function of the chemistry of the source where the rock came from, as well as the fractionation history the rock has undergone.[29] Fractionation is in turn a function of thepartition coefficients of each element. Partition coefficients are responsible for the fractionation of trace elements (including rare-earth elements) into the liquid phase (the melt/magma) into the solid phase (the mineral). If an element preferentially remains in the solid phase it is termed 'compatible', and if it preferentially partitions into the melt phase it is described as 'incompatible'.[29] Each element has a different partition coefficient, and therefore fractionates into solid and liquid phases distinctly. These concepts are also applicable to metamorphic and sedimentary petrology.
In igneous rocks, particularly infelsic melts, the following observations apply: anomalies in europium are dominated by the crystallization offeldspars.Hornblende, controls the enrichment of MREE compared to LREE and HREE. Depletion of LREE relative to HREE may be due to the crystallization ofolivine,orthopyroxene, andclinopyroxene. On the other hand, the depletion of HREE relative to LREE may be due to the presence ofgarnet, as garnet preferentially incorporates HREE into its crystal structure. The presence ofzircon may also cause a similar effect.[29]
In sedimentary rocks, rare-earth elements inclastic sediments are a representation of provenance. The rare-earth element concentrations are not typically affected by sea and river waters, as rare-earth elements are insoluble and thus have very low concentrations in these fluids. As a result, when sediment is transported, rare-earth element concentrations are unaffected by the fluid and instead the rock retains the rare-earth element concentration from its source.[29]
Sea and river waters typically have low rare-earth element concentrations. However, aqueous geochemistry is still very important. In oceans, rare-earth elements reflect input from rivers,hydrothermal vents, andaeolian sources;[29] this is important in the investigation of ocean mixing and circulation.[31]
Rare-earth elements are also useful for dating rocks, as someradioactive isotopes display long half-lives. Of particular interest are the138La-138Ce,147Sm-143Nd, and176Lu-176Hf systems.[31]
Until 1948, most of the world's rare earths were sourced fromplacer sand deposits inIndia andBrazil. In the 1950s, South Africa was the world's rare earth source, from a monazite-rich reef at theSteenkampskraal mine inWestern Cape province.[44] From the 1960s until the 1980s, theMountain Pass rare earth mine in California made the United States the leading producer. Today, the Indian and South African deposits still produce some rare-earth concentrates, but they were dwarfed by the scale of Chinese production. In 2017, China produced 81% of the world's rare-earth supply, mostly inInner Mongolia,[8][45] although it had only 36.7% of reserves.
In 2018, Australia was the world's second largest producer, and the only other major producer, with 15% of world production.[46] All of the world's heavy rare earths (such as dysprosium) come from Chinese rare-earth sources such as thepolymetallicBayan Obo deposit.[45][47] The Browns Range mine, located 160 km south east ofHalls Creek in northernWestern Australia, was under development in 2018 and is positioned to become the first significant dysprosium producer outside of China.[48]
REE is increasing in demand due to the fact that they are essential for new and innovative technology that is being created. These new products that need REEs to be produced are high-technology equipment such as smart phones, digital cameras, computer parts, semiconductors, etc. In addition, these elements are more prevalent in the following industries: renewable energy technology, military equipment, glass making, and metallurgy.[49]Increased demand has strained supply, and there is growing concern that the world may soon face a shortage of the rare earths.[50]
In 2009, future worldwide demand for rare-earth elements was expected to exceed supply by 40,000 metric tons annually unless major new sources are developed.[51] In 2013, it was stated that the demand for REEs would increase due to the dependence of the EU on these elements, the fact that rare-earth elements cannot be substituted by other elements and that REEs have a low recycling rate. Due to the increased demand and low supply, future prices are expected to increase and there is a chance that countries other than China will open REE mines.[52] In 2023, there were over a hundred ongoing mining projects, with many options outside of China.[53]
As a result of the increased demand and tightening restrictions on exports of the metals from China, some countries are stockpiling rare-earth resources.[54] Searches for alternative sources inAustralia,Brazil,Canada,South Africa,Tanzania,Greenland, and theUnited States are ongoing.[55] Mines in these countries were closed when China undercut world prices in the 1990s, and it will take a few years to restart production as there are manybarriers to entry.[56][57]
These concerns have intensified due to the actions of China, the predominant supplier.[58] Specifically, China has announced regulations on exports and a crackdown on smuggling.[56] On September 1, 2009, China announced plans to reduce its export quota to 35,000 tons per year in 2010–2015 to conserve scarce resources and protect the environment.[59] On October 19, 2010,China Daily, citing an unnamed Ministry of Commerce official, reported that China will "further reduce quotas for rare-earth exports by 30 percent at most next year to protect the precious metals from over-exploitation."[60]
The government in Beijing further increased its control by forcing smaller, independent miners to merge into state-owned corporations or face closure. At the end of 2010, China announced that the first round of export quotas in 2011 for rare earths would be 14,446 tons, which was a 35% decrease from the previous first round of quotas in 2010.[61] China announced further export quotas on 14 July 2011 for the second half of the year with total allocation at 30,184 tons with total production capped at 93,800 metric tons.[62] In September 2011, China announced the halt in production of three of its eight major rare-earth mines, responsible for almost 40% of China's total rare-earth production.[63]
In March 2012, the US, EU, and Japan confronted China at WTO about these export and production restrictions. China responded with claims that the restrictions had environmental protection in mind.[64][65] In August 2012, China announced a further 20% reduction in production.[66]The United States, Japan, and the European Union filed a joint lawsuit with the World Trade Organization in 2012 against China, arguing that China should not be able to deny such important exports.[65]
In 2012, in response to the opening of new mines in other countries (Lynas in Australia andMolycorp in the United States), prices of rare earths dropped.[67]The price of dysprosium oxide was US$994/kg in 2011, and dropped to US$265/kg by 2014.[68]
In August 2014, the WTO ruled that China had broken free-trade agreements, and the WTO said in the summary of key findings that "the overall effect of the foreign and domestic restrictions is to encourage domestic extraction and secure preferential use of those materials by Chinese manufacturers." China declared that it would implement the ruling on September 26, 2014, but would need some time to do so. By January 5, 2015, China had lifted all quotas from the export of rare earths, but export licenses will still be required.[69]
In 2019,China supplied between 85% and 95% of the global demand for the 17 rare-earth powders, half of them sourced fromMyanmar.[70][dubious –discuss] After the2021 military coup in that country, future supplies of critical ores were possibly constrained. Additionally, it was speculated that the PRC could again reduce rare-earth exports to counter-acteconomic sanctions imposed by the US and EU countries. Rare-earth metals serve as crucial materials forelectric vehicle manufacturing and high-tech military applications.[71]
In 2025, during theChina–United States trade war, China restricted exports of heavy rare earths to the United States.[72][73] Between 2020 and 2023, 70% of all rare earth compounds and metals imported into the United States came from China.[74]
Kachin State in Myanmar is the world's largest source of rare earths.[75] In 2021, China importedUS$200 million of rare earths from Myanmar in December 2021, exceeding 20,000 metric tons.[76] Rare earths were discovered nearPang War inChipwi Township along theChina–Myanmar border in the late 2010s.[77] As China has shut down domestic mines due to the detrimental environmental impact, it has largely outsourced rare-earth mining to Kachin State.[76]
Chinese companies and miners illegally set up operations in Kachin State without government permits, and instead circumvent the central government by working with aBorder Guard Force militia under theTatmadaw, formerly known as theNew Democratic Army – Kachin, which has profited from this extractive industry.[76][78] As of March 2022[update], 2,700 mining collection pools scattered across 300 separate locations were found in Kachin State, encompassing the area ofSingapore, an exponential increase from 2016.[76] Land has also been seized from locals to conduct mining operations.[76]
Significant sites under development includeSteenkampskraal in South Africa, the world's highest grade rare earths and thorium mine, closed in 1963, but has been gearing to go back into production.[79] Over 80% of the infrastructure is already complete.[80]
Adding to potential mine sites,ASX listed Peak Resources announced in February 2012, that their Tanzanian-basedNgualla project contained not only the 6th largest deposit by tonnage outside of China but also the highest grade of rare-earth elements of the 6.[81]
Other mines include the Nolans Project in Central Australia, theBokan Mountain project in Alaska, the remoteHoidas Lake project in northern Canada,[82] and theMount Weld project in Australia.[45][57][83] TheHoidas Lake project has the potential to supply about 10% of the $1 billion of REE consumption that occurs in North America every year.[84]
The largest rare-earth deposit in the U.S. is atMountain Pass, California, sixty miles south ofLas Vegas. Originally opened byMolycorp, the deposit has been mined, off and on, since 1951.[45][89] A second large deposit of REEs at Elk Creek in southeastNebraska[90] is under consideration by NioCorp Development Ltd[91] who hopes to open a niobium, scandium, and titanium mine there.[92] That mine may be able to produce as much as 7,200 metric tons of ferro niobium and 95 metric tons of scandium trioxide annually.[93] As of 2022, financing is still in the works.[90]
In 2024 American Rare Earths Inc. disclosed that its reserves near Wheatland Wyoming totaled 2.34 billion metric tons, possibly the world's largest and larger than a separate 1.2 million metric ton deposit in northeastern Wyoming.[94]
In the UK, Pensana has begun construction of their US$195 million rare-earth processing plant which secured funding from the UK government's Automotive Transformation Fund. The plant will process ore from theLongonjo mine in Angola and other sources as they become available.[95][96] The company are targeting production in late 2023, before ramping up to full capacity in 2024. Pensana aim to produce 12,500 metric tons of separated rare earths, including 4,500 metric tons of magnet metal rare earths.[97][98]
In 2010, a large deposit of rare-earth minerals was discovered inKvanefjeld in southernGreenland.[99] Pre-feasibility drilling at this site has confirmed significant quantities of blacklujavrite, which contains about 1% rare-earth oxides (REO).[100] TheEuropean Union has urged Greenland to restrict Chinese development of rare-earth projects there, but as of early 2013, thegovernment of Greenland has said that it has no plans to impose such restrictions.[101] Many Danish politicians have expressed concerns that other nations, including China, could gain influence in thinly populated Greenland, given the number of foreign workers and investment that could come from Chinese companies in the near future because of the law passed December 2012.[102]
In centralSpain,Ciudad Real Province, the proposed rare-earth mining project 'Matamulas' may provide, according to its developers, up to 2,100 Tn/year (33% of the annual UE demand). However, this project has been suspended by regional authorities due to social and environmental concerns.[103]
In January 2023, Swedish state-owned mining company LKAB announced that it had discovered a deposit of over 1 million metric tons of rare earths in the country'sKiruna area, which would make it the largest such deposit in Europe.[107]
China processes about 90% of the world's REEs. As a result, theEuropean Union imports practically all of its rare earth elements from China. TheEuropean Union Parliament considers this to a strategic risk.[108]
In June 2024, Rare Earths Norway found a rare-earth oxide deposit of 8.8 million metric tons inTelemark, Norway, making it Europe's largest known rare-earth element deposit. The mining firm predicted that it would finish developing the first stage of mining in 2030.[109]
In early 2011, Australian mining companyLynas was reported to be "hurrying to finish" a US$230 million rare-earth refinery on the eastern coast of Peninsular Malaysia's industrial port ofKuantan. The plant would refine ore — lanthanides concentrate from theMount Weld mine in Australia. The ore would be trucked toFremantle and transported bycontainer ship to Kuantan. Within two years, Lynas was said to expect the refinery to be able to meet nearly a third of the world's demand for rare-earth materials, not countingChina.[112] The Kuantan development brought renewed attention to the Malaysian town ofBukit Merah inPerak, where a rare-earth mine operated by aMitsubishi Chemical subsidiary, Asian Rare Earth, closed in 1994 and leftcontinuing environmental and health concerns.[113][114]
In mid-2011, after protests, Malaysian government restrictions on the Lynas plant were announced. At that time, citing subscription-onlyDow Jones Newswire reports, aBarrons report said the Lynas investment was $730 million, and the projected share of the global market it would fill put at "about a sixth."[115] An independent review initiated by the Malaysian Government, and conducted by theInternational Atomic Energy Agency (IAEA) in 2011 to address concerns of radioactive hazards, found no non-compliance with international radiation safety standards.[116]
However, the Malaysian authorities confirmed that as of October 2011, Lynas was not given any permit to import any rare-earth ore into Malaysia. In February 2012, the Malaysian AELB (Atomic Energy Licensing Board) recommended that Lynas be issued a temporary operating license subject to meeting a number of conditions. In September 2014, Lynas was issued a 2-year full operating stage license by the AELB.[117]
In November 2024,economy ministerRafizi Ramli said he hoped Malaysia is able to produce rare-earth elements within three years, through discussions with China to provide technology.[118] In the past, plans to mine rare-earth elements atKedah caused concerns of destroying forest reserves and harming water catchment areas.[119][120]
Significant quantities of rare-earth oxides are found in tailings accumulated from 50 years ofuranium ore,shale, andloparite mining atSillamäe,Estonia.[121] Due to the rising prices of rare earths, extraction of these oxides has become economically viable. The country currently exports around 3,000 metric tons per year, representing around 2% of world production.[122] Similar resources are suspected in the western United States, wheregold rush-era mines are believed to have discarded large amounts of rare earths, because they had no value at the time.[123]
In January 2013 a Japanese deep-sea research vessel obtained seven deep-sea mud core samples from the Pacific Ocean seafloor at 5,600 to 5,800 meters depth, approximately 250 kilometres (160 mi) south of the island ofMinami-Tori-Shima.[124] The research team found a mud layer 2 to 4 meters beneath the seabed with concentrations of up to 0.66% rare-earth oxides. A potential deposit might compare in grade with the ion-absorption-type deposits in southern China that provide the bulk of Chinese REO mine production, which grade in the range of 0.05% to 0.5% REO.[125][126]
Another recently developed source of rare earths iselectronic waste and otherwastes that have significant rare-earth components.[127] Advances inrecycling technology have made the extraction of rare earths from these materials less expensive.[128] Recycling plants operate in Japan, where an estimated 300,000 tons of rare earths are found in unused electronics.[129] InFrance, theRhodia group is setting up two factories, inLa Rochelle andSaint-Fons, that will produce 200 tons of rare earths a year from usedfluorescent lamps, magnets, and batteries.[130][131]Coal[132] and coal by-products, such asash and sludge, are a potential source of critical elements including rare-earth elements (REE) with estimated amounts in the range of 50 million metric tons.[133]
A 2022 study mixedfly ash with carbon black and then sent a 1-second current pulse through the mixture, heating it to 3,000 °C (5,430 °F). The fly ash contains microscopic bits of glass that encapsulate the metals. The heat shatters the glass, exposing the rare earths. Flash heating also convertsphosphates into oxides, which are more soluble and extractable. Using hydrochloric acid at concentrations less than 1% of conventional methods, the process extracted twice as much material.[134]
According to chemistry professorAndrea Sella in 2016, rare-earth elements differ from other elements, in that when looked at analytically, they are virtually inseparable, having almost the same chemical properties. However, in terms of their electronic and magnetic properties, each one occupies a unique technological niche that nothing else can.[4] For example, "the rare-earth elementspraseodymium (Pr) andneodymium (Nd) can both be embedded inside glass and they completely cut out the glare from the flame when one is doingglass-blowing."[4]
This articleis missing information about advantages of using rare earths over alternatives. Please expand the article to include this information. Further details may exist on thetalk page.(February 2025)
The uses, applications, and demand for rare-earth elements have expanded over the years. Globally, most REEs are used forcatalysts and magnets.[135] In the US, more than half of REEs are used for catalysts; ceramics, glass, and polishing are also main uses.[136]
Other important uses of rare-earth elements are applicable to the production of high-performance magnets, alloys, glasses, and electronics. Ce and La are important as catalysts, and are used forpetroleum refining and asdiesel additives. Nd is important in magnet production in traditional and low-carbon technologies. Rare-earth elements in this category are used in the electric motors ofhybrid andelectric vehicles, generators in somewind turbines, hard disc drives, portable electronics, microphones, and speakers.[citation needed]
Ce, La, and Nd are important in alloy making, and in the production offuel cells andnickel-metal hydride batteries. Ce, Ga, and Nd are important in electronics and are used in the production of LCD and plasma screens, fiber optics, and lasers,[137] and in medical imaging. Additional uses for rare-earth elements are as tracers in medical applications, fertilizers, and in water treatment.[31]
REEs have been used in agriculture to increase plant growth, productivity, and stress resistance seemingly without negative effects for human and animal consumption. REEs are used in agriculture through REE-enriched fertilizers which is a widely used practice in China.[138] REEs are feed additives for livestock which has resulted in increased production such as larger animals and a higher production of eggs and dairy products. This practice has resulted in REE bioaccumulation within livestock and has impacted vegetation and algae growth in these agricultural areas.[139] While no ill effects have been observed at current low concentrations, the effects over the long term and with accumulation over time are unknown, prompting some calls for more research into their possible effects.[138][140]
REEs also have applications in defense. The strength of neodynium magnets can be used in missile guidance systems. For high-end camera lenses used for intelligence, lanthanum enhances the clarity of the glass.[141]
REEs are naturally found in very low concentrations in the environment. Mines are often in countries where environmental and social standards are very low, leading to human rights violations, deforestation, and contamination of land and water.[142][143] Generally, it is estimated that extracting 1 metric ton of rare earth element creates around 2,000 metric tons of waste, partly toxic, including 1 ton of radioactive waste. The largest mining site of REEs,Bayan Obo in China produced more than 70,000 tons of radioactive waste, that contaminated ground water.[144]
Near mining and industrial sites, the concentrations of REEs can rise to many times the normal background levels. Once in the environment, REEs can leach into the soil where their transport is determined by numerous factors such as erosion, weathering, pH, precipitation, groundwater, etc. Acting much like metals, they can speciate depending on the soil condition being either motile or adsorbed to soil particles. Depending on their bio-availability, REEs can be absorbed into plants and later consumed by humans and animals.[145]
The mining of REEs, use of REE-enriched fertilizers, and the production of phosphorus fertilizers all contribute to REE contamination.[145] Strong acids are used during the extraction process of REEs, which can then leach out into the environment and be transported through water bodies and result in the acidification of aquatic environments. Another additive of REE mining that contributes to REE environmental contamination iscerium oxide (CeO 2), which is produced during the combustion of diesel and released as exhaust, contributing heavily to soil and water contamination.[139]
Mining, refining, and recycling of rare earths have serious environmental consequences if not properly managed. Low-level radioactivetailings resulting from the occurrence ofthorium anduranium in rare-earth ores present a potential hazard[146][147] and improper handling of these substances can result in extensive environmental damage. In May 2010, China announced a major, five-month crackdown on illegal mining in order to protect the environment and its resources. This campaign is expected to be concentrated in the South,[148] where mines – commonly small, rural, and illegal operations – are particularly prone to releasing toxic waste into the general water supply.[45][149]
The major operation inBaotou, in Inner Mongolia, where much of the world's rare-earth supply is refined, has caused major environmental damage.[150] China's Ministry of Industry and Information Technology estimated that cleanup costs in Jiangxi province at $5.5 billion.[143]
It is possible to filter out and recover any rare-earth elements that flow out with the wastewater from mining facilities. Such filtering and recovery equipment may not always be present on the outlets carrying the wastewater.[151][152][153]
REEs are amongst the most critical elements to modern technologies and society. Despite this, typically only around 1% of REEs are recycled from end-products.[154] Recycling and reusing REEs is not easy: these elements are mostly present in tiny amounts in small electronic parts and they are difficult to separate chemically.[155] For example, recovery of neodymium requires manual disassembly of hard disk drives because shredding the drives only recovers 10% of the REE.[156]
REE recycling and reuse have been increasingly focused on in recent years. The main concerns include environmental pollution during REE recycling and increasing recycling efficiency. Literature published in 2004 suggests that, along with previously established pollution mitigation, a more circular supply chain would help mitigate some of the pollution at the extraction point. This means recycling and reusing REEs that are already in use or reaching the end of their life cycle.[140] A study published in 2014 suggests a method to recycle REEs from wastenickel-metal hydride batteries, demonstrating a recovery rate of 95.16%.[157]
Rare-earth elements could also be recovered from industrial wastes with practical potential to reduce environmental and health impacts from mining, waste generation, and imports if known and experimental processes are scaled up.[158][159] A 2019 study suggests that "fulfillment of the circular economy approach could reduce up to 200 times the impactin the climate change category and up to 70 times the cost due to the REE mining."[160] In 2020, in most of the reported studies reviewed by ascientific review, "secondary waste is subjected to chemical and or bioleaching followed by solvent extraction processes for clean separation of REEs."[161]
Currently, people take two essential resources into consideration for the secure supply of REEs: one is to extract REEs from primary resources like mines harboring REE-bearing ores, regolith-hosted clay deposits,[162] ocean bed sediments, coal fly ash,[163] etc. A work developed a green system for recovery of REEs from coal fly ash by using citrate and oxalate who are strong organic ligand and capable of complexing or precipitating with REE.[164] The other one is from secondary resources such as electronic, industrial waste and municipal waste. E-waste contains a significant concentration of REEs, and thus is the primary option for REE recycling now[when?]. According to a 2019 study, approximately 50 million metric tons of electronic waste are dumped in landfills worldwide each year. Despite the fact that e-waste contains a significant amount of rare-earth elements (REE), only 12.5% of e-waste is currently being recycled for all metals.[155]
The mining of REEs has caused thecontamination of soil and water around production areas, which has impacted vegetation in these areas by decreasingchlorophyll production, which affects photosynthesis and inhibits the growth of the plants.[139] However, the impact of REE contamination on vegetation is dependent on the plants present in the contaminated environment: not all plants retain and absorb REEs. Also, the ability of the vegetation to intake the REE is dependent on the type of REE present in the soil, hence there are a multitude of factors that influence this process.[165] Agricultural plants are the main type of vegetation affected by REE contamination in the environment, the two plants with a higher chance of absorbing and storing REEs being apples and beets.[145]
There is a possibility that REEs can leach out into aquatic environments and be absorbed by aquatic vegetation, which can then bio-accumulate and potentially enter the human food chain if livestock or humans choose to eat the vegetation. An example of this situation was the case of thewater hyacinth (Eichhornia crassipes) in China, where the water was contaminated due to a REE-enriched fertilizer being used in a nearby agricultural area. The aquatic environment became contaminated withcerium and resulted in the water hyacinth becoming three times more concentrated in cerium than its surrounding water.[165]
The chemical properties of the REEs are so similar that they are expected to show similar toxicity in humans.Mortality studies show REEs are not highly toxic.[166] Long term (18 months) inhalation of dust containing high levels (60%) of REEs has been shown to causepneumoconiosis but the mechanism is unknown.[166]
While REEs are not major pollutants, the increase application of REEs in new technologies has increased the need to understand their safe levels of exposure for humans.[167] One side effect of mining REEs can be exposure to harmful radioactiveThorium as has been demonstrated at large mine in Batou (Mongolia).[168] The rare-earth mining and smelting process can release airborne fluoride which will associate with total suspended particles (TSP) to form aerosols that can enter human respiratory systems. Research from Baotou, China shows that the fluoride concentration in the air near REE mines is higher than the limit value from WHO, but the health effects of this exposure are unknown.[169]
Analysis of people living near mines in China had many times the levels of REEs in their blood, urine, bone, and hair compared to controls far from mining sites, suggesting possiblebioaccumulation of REEs. This higher level was related to the high levels of REEs present in the vegetables they cultivated, the soil, and the water from the wells, indicating that the high levels were caused by the nearby mine. However the levels found were not high enough to cause health effects.[170] Analysis of REEs in street dust in China suggest "no augmented health hazard".[171]Similarly, analysis of cereal crops in mining areas in China found levels too low for health risks.[172]
Experiments exposing rats to various cerium compounds have found accumulation primarily in the lungs and liver. This resulted in various negative health outcomes associated with those organs.[173] REEs have been added to feed in livestock to increase their body mass and increase milk production.[173] They are most commonly used to increase the body mass of pigs, and it was discovered that REEs increase the digestibility and nutrient use of pigs' digestive systems.[173] Studies point to a dose-response when considering toxicity versus positive effects. While small doses from the environment or with proper administration seem to have no ill effects, larger doses have been shown to have negative effects specifically in the organs where they accumulate.[173]
The process of mining REEs in China has resulted in soil and water contamination in certain areas, which when transported into aquatic bodies could potentially bio-accumulate within aquatic biota. In some cases, animals that live in REE-contaminated areas have been diagnosed with organ or system problems.[139] REEs have been used in freshwater fish farming because it protects the fish from possible diseases.[173] One main reason why they have been avidly used in animal livestock feeding is that they have had better results than inorganic livestock feed enhancers.[174]
This section needs to beupdated. Please help update this article to reflect recent events or newly available information.(May 2019)
After the1982 Bukit Merah radioactive pollution, the mine inMalaysia has been the focus of a US$100 million cleanup that is proceeding in 2011. After having accomplished the hilltop entombment of 11,000 truckloads of radioactively contaminated material, the project is expected to entail in summer, 2011, the removal of "more than 80,000 steel barrels of radioactive waste to the hilltop repository."[114]
In May 2011, after theFukushima nuclear disaster, widespread protests took place in Kuantan over theLynas refinery and radioactive waste from it. The ore to be processed has very low levels of thorium, and Lynas founder and chief executive Nicholas Curtis said "There is absolutely no risk to public health." T. Jayabalan, a doctor who says he has been monitoring and treating patients affected by the Mitsubishi plant, "is wary of Lynas's assurances. The argument that low levels of thorium in the ore make it safer doesn't make sense, he says, because radiation exposure is cumulative."[175] Construction of the facility has been halted until an independentUnited NationsIAEA panel investigation is completed, which is expected by the end of June 2011.[176]New restrictions were announced by the Malaysian government in late June.[115]
AnIAEA panel investigation was completed and no construction has been halted. Lynas is on budget and on schedule to start producing in 2011. The IAEA concluded in a report issued in June 2011 that it did not find any instance of "any non-compliance with international radiation safety standards" in the project.[177]
If the proper safety standards are followed, REE mining is relatively low impact. Molycorp (before going bankrupt) often exceeded environmental regulations to improve its public image.[178]
In Greenland, there is a significant dispute on whether to start a new rare-earth mine inKvanefjeld due to environmental concerns.[179]
Global rare-earth-oxide production trends, 1956-2008 (USGS)
China has officially citedresource depletion and environmental concerns as the reasons for a nationwide crackdown on its rare-earth mineral production sector.[63] Non-environmental motives have also been imputed to China's rare-earth policy.[150] In 2010, according toThe Economist, "Slashing their exports of rare-earth metals ... is all about moving Chinese manufacturers up the supply chain, so they can sell valuable finished goods to the world rather than lowly raw materials."[180]
China currently has an effective monopoly on the world's REE Value Chain.[181] (All of the refineries and processing plants that transform the raw ore into valuable elements.[182]) In the words of Deng Xiaoping, a Chinese politician from the late 1970s to the late 1980s, "The Middle East has oil; we have rare earths ... it is of extremely important strategic significance; we must be sure to handle the rare earth issue properly and make the fullest use of our country's advantage in rare-earth resources."[183]
One possible example of market control is the division of General Motors that deals with miniaturized magnet research, which shut down its US office and moved its entire staff toChina in 2006[184] China's export quota only applies to the metal but not products made from these metals such as magnets.
It was reported,[185] but officially denied,[186] that China instituted anexport ban on shipments of rare-earth oxides, but not alloys, to Japan on 22 September 2010, in response tothe detainment of a Chinese fishing boat captain by theJapanese Coast Guard.[187][65] On September 2, 2010, a few days before the fishing boat incident,The Economist reported that "China ... in July announced the latest in a series of annual export reductions, this time by 40% to precisely 30,258 tonnes."[188][65]
A 2011 report "China's Rare-Earth Industry", issued by the US Geological Survey and US Department of the Interior, outlines industry trends within China and examines national policies that may guide the future of the country's production. The report notes that China's lead in the production of rare-earth minerals has accelerated over the past two decades. In 1990, China accounted for only 27% of such minerals. In 2009, world production was 132,000 metric tons; China produced 129,000 of those tons. According to the report, recent patterns suggest that China will slow the export of such materials to the world: "Owing to the increase in domestic demand, the Government has gradually reduced the export quota during the past several years."[190]
In 2006, China allowed 47 domestic rare-earth producers and traders and 12 Sino-foreign rare-earth producers to export. Controls have since tightened annually; by 2011, only 22 domestic rare-earth producers and traders and 9 Sino-foreign rare-earth producers were authorized. The government's future policies will likely keep in place strict controls: "According to China's draft rare-earth development plan, annual rare-earth production may be limited to between 130,000 and 140,000 [metric tons] during the period from 2009 to 2015. The export quota for rare-earth products may be about 35,000 [metric tons] and the Government may allow 20 domestic rare-earth producers and traders to export rare earths."[190]
The United States Geological Survey was actively surveying southernAfghanistan for rare-earth deposits under the protection of United States military forces. Since 2009 the USGS has conducted remote sensing surveys as well as fieldwork to verify Soviet claims that volcanic rocks containing rare-earth metals exist inHelmand Province near the village ofKhanashin. The USGS study team has located a sizable area of rocks in the center of an extinct volcano containing light rare-earth elements including cerium and neodymium. It has mapped 1.3 million metric tons of desirable rock, or about ten years of supply at current demand levels.The Pentagon has estimated its value at about $7.4 billion.[191]
It has been argued that the geopolitical importance of rare earths has been exaggerated in the literature on the geopolitics of renewable energy, underestimating the power of economic incentives for expanded production.[192][193] This especially concerns neodymium. Due to its role in permanent magnets used for wind turbines, it has been argued that neodymium will be one of the main objects of geopolitical competition in a world running on renewable energy. But this perspective has been criticized for failing to recognize that most wind turbines have gears and do not use permanent magnets.[193]
The plot ofEric Ambler's now-classic 1967 international crime-thrillerDirty Story, akaThis Gun for Hire, not to be confused with the 1942 movieThis Gun for Hire, features a struggle between two rival mining cartels to control a plot of land in a fictional African country, which contains rich minable rare-earth ore deposits.[194]
^abHaxel G.; Hedrick J.; Orris J. (2002). Peter H. Stauffer; James W. Hendley II (eds.)."Rare Earth Elements—Critical Resources for High Technology"(PDF). United States Geological Survey. USGS Fact Sheet: 087-02.Archived(PDF) from the original on December 14, 2010. RetrievedMarch 13, 2012.However, in contrast to ordinary base andprecious metals, REE have very little tendency to become concentrated in exploitable ore deposits. Consequently, most of the world's supply of REE comes from only a handful of sources, almost entirely as a byproduct of mining other elements in commercially exploitable concentrations they occur alongside.
^Keith R. Long; Bradley S. Van Gosen; Nora K. Foley; Daniel Cordier."The Geology of Rare Earth Elements".Geology.com.Archived from the original on October 26, 2021. RetrievedJune 19, 2018.
^Lide, David R., ed. (1996–1997).CRC Handbook of Chemistry and Physics (77th ed.). Boca Raton, Florida: CRC Press. pp. 10–12.ISBN0-8493-0477-6.
^abcC. R. Hammond. "Section 4; The Elements". In David R. Lide (ed.).CRC Handbook of Chemistry and Physics. (Internet Version 2009) (89th ed.). Boca Raton, FL: CRC Press/Taylor and Francis.
^Fritz Ullmann, ed. (2003).Ullmann's Encyclopedia of Industrial Chemistry. Vol. 31. Contributor: Matthias Bohnet (6th ed.). Wiley-VCH. p. 24.ISBN978-3-527-30385-4.
^Mentioned by Prof.Andrea Sella on a BBCBusiness Daily programme, March 19, 2014[1]. Unfortunately this mnemonic doesn't distinguish very well between praseodymium and promethium and between terbium and thulium.
^abZepf, Volker (2013).Rare earth elements: a new approach to the nexus of supply, demand and use: exemplified along the use of neodymium in permanent magnets. Berlin; London: Springer.ISBN978-3-642-35458-8.
^Heilbron, J. L.; Moseley, H. G. J. (1974).H. G. J. Moseley: the life and letters of an English physicist, 1887-1915. Berkeley: University of California Press.ISBN978-0-520-02375-8.
^abcdWorking Group (December 2011)."Rare Earth Elements"(PDF). Geological Society of London.Archived(PDF) from the original on February 9, 2022. RetrievedMay 18, 2018.
^M. V. Abrashev; N. D. Todorov; J. Geshev (September 9, 2014). "Raman spectra of R 2O3 (R—rare earth) sesquioxides with C-type bixbyite crystal structure: A comparative study".Journal of Applied Physics.116 (10): 103508.Bibcode:2014JAP...116j3508A.doi:10.1063/1.4894775.hdl:10183/107858.S2CID55024339.
^P. Belli; R. Bernabei; F. Cappella; R. Cerulli; C. J. Dai; F. A. Danevich; A. d'Angelo; A. Incicchitti; V. V. Kobychev; S. S. Nagorny; S. Nisi; F. Nozzoli; D. Prosperi; V. I. Tretyak; S. S. Yurchenko (2007). "Search for α decay of natural Europium".Nuclear Physics A.789 (1–4):15–29.Bibcode:2007NuPhA.789...15B.doi:10.1016/j.nuclphysa.2007.03.001.
^abcdefghijklmnoJébrak, Michel; Marcoux, Eric; Laithier, Michelle; Skipwith, Patrick (2014).Geology of mineral resources (2nd ed.). St. John's, NL: Geological Association of Canada.ISBN978-1-897095-73-7.OCLC933724718.
^abBau, Michael (April 1, 1996). "Controls on the fractionation of isovalent trace elements in magmatic and aqueous systems: evidence from Y/Ho, Zr/Hf, and lanthanide tetrad effect".Contributions to Mineralogy and Petrology.123 (3):323–333.Bibcode:1996CoMP..123..323B.doi:10.1007/s004100050159.ISSN1432-0967.S2CID97399702.
^Gambogi, Joseph (January 2018)."Rare Earths"(PDF).Mineral Commodity Summaries. U.S. Geological Survey. pp. 132–133.Archived(PDF) from the original on January 25, 2019. RetrievedFebruary 14, 2018.
^Lunn, J. (2006)."Great western minerals"(PDF). London: Insigner Beaufort Equity Research. Archived fromthe original(PDF) on April 9, 2008. RetrievedApril 19, 2008.
^"Federal minister approves N.W.T. rare earth mine".CBC News. November 4, 2013.Archived from the original on June 22, 2022. RetrievedNovember 5, 2013.It follows the recommendation from the Mackenzie Valley Environmental Review Board in July, and marks a major milestone in the company's effort to turn the project into an operating mine. Avalon claims Nechalacho is "the most advanced large heavy rare earth development project in the world".
^"북한, 올 5~6월 희토류 중국 수출 크게 늘어" [North Korea Rare Earth exports to China increased significantly from May to June].voakorea.com (in Korean). July 28, 2014.Archived from the original on March 30, 2019. RetrievedFebruary 10, 2017.
^Bradsher, Keith (March 8, 2011)."Taking a Risk for Rare Earths".The New York Times. (March 9, 2011 p. B1 NY ed.).Archived from the original on June 15, 2022. RetrievedMarch 9, 2011.
^Rofer, Cheryl K.; Tõnis Kaasik (2000).Turning a Problem Into a Resource: Remediation and Waste Management at the Sillamäe Site, Estonia. Volume 28 of NATO science series: Disarmament technologies. Springer. p. 229.ISBN978-0-7923-6187-9.
^Zhi Li, Ling; Yang, Xiaosheng (September 4, 2014).China's rare earth ore deposits and beneficiation techniques(PDF). 1st European Rare Earth Resources Conference. Milos, Greece: European Commission for the 'Development of a sustainable exploitation scheme for Europe's Rare Earth ore deposits'.Archived(PDF) from the original on January 19, 2020. RetrievedDecember 11, 2016.
^Um, Namil (July 2017).Hydrometallurgical recovery process of rare-earth elements from waste: main application of acid leaching with devised diagram. INTECH. pp. 41–60.ISBN978-953-51-3401-5.
^Wencai Zhang; Mohammad Rezaee; Abhijit Bhagavatula; Yonggai Li; John Groppo; Rick Honaker (2015). "A Review of the Occurrence and Promising Recovery Methods of Rare Earth Elements from Coal and Coal By-Products".International Journal of Coal Preparation and Utilization.35 (6):295–330.Bibcode:2015IJCPU..35..295Z.doi:10.1080/19392699.2015.1033097.S2CID128509001.
^Environmental Technologies to Treat Rare Earth Element Pollution: Principles and Engineering. IWA Publishing. 2022. p. 103.ISBN9781789062236.
^Rizk, Shirley (June 21, 2019)."What colour is the cloud?".European Investment Bank.Archived from the original on April 14, 2021. RetrievedSeptember 17, 2020.
^abcVolokh, A. A.; Gorbunov, A. V.; Gundorina, S. F.; Revich, B. A.; Frontasyeva, M. V.; Chen Sen Pal (June 1, 1990). "Phosphorus fertilizer production as a source of rare-earth elements pollution of the environment".Science of the Total Environment.95:141–148.Bibcode:1990ScTEn..95..141V.doi:10.1016/0048-9697(90)90059-4.ISSN0048-9697.PMID2169646.
^Amato, A.; Becci, A.; Birloaga, I.; De Michelis, I.; Ferella, F.; Innocenzi, V.; Ippolito, N. M.; Pillar Jimenez Gomez, C.; Vegliò, F.; Beolchini, F. (May 1, 2019). "Sustainability analysis of innovative technologies for the rare earth elements recovery".Renewable and Sustainable Energy Reviews.106:41–53.Bibcode:2019RSERv.106...41A.doi:10.1016/j.rser.2019.02.029.hdl:11566/264482.ISSN1364-0321.S2CID115810707.
^Jyothi, Rajesh Kumar; Thenepalli, Thriveni; Ahn, Ji Whan; Parhi, Pankaj Kumar; Chung, Kyeong Woo; Lee, Jin-Young (September 10, 2020). "Review of rare earth elements recovery from secondary resources for clean energy technologies: Grand opportunities to create wealth from waste".Journal of Cleaner Production.267: 122048.Bibcode:2020JCPro.26722048J.doi:10.1016/j.jclepro.2020.122048.ISSN0959-6526.S2CID219469381.
^abChua, H (June 18, 1998). "Bio-accumulation of environmental residues of rare earth elements in aquatic floraEichhornia crassipes (Mart.) Solms in Guangdong Province of China".Science of the Total Environment.214 (1–3):79–85.Bibcode:1998ScTEn.214...79C.doi:10.1016/S0048-9697(98)00055-2.ISSN0048-9697.
^Chen, X. A., et al. "A twenty-year follow-up study on health effects-following long-term exposure to thorium dusts." HEIR 2004 (2005): 139.
^Zhong, Buqing; Wang, Lingqing; Liang, Tao; Xing, Baoshan (October 2017). "Pollution level and inhalation exposure of ambient aerosol fluoride as affected by polymetallic rare earth mining and smelting in Baotou, north China".Atmospheric Environment.167:40–48.Bibcode:2017AtmEn.167...40Z.doi:10.1016/j.atmosenv.2017.08.014.
