View source for Rare-earth element

{{short description|Any of the fifteen lanthanides plus scandium and yttrium}}
{{Periodic table (micro)|title=Rare-earth elements<br/>in the periodic table|mark=Sc,Y,La,Ce,Pr,Nd,Pm,Sm,Eu,Gd,Tb,Dy,Ho,Er,Tm,Yb,Lu}}
{{Use mdy dates|date=September 2020}}
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|caption1=[[Rare-earth mineral|Rare-earth ore]] ''(shown with a 19&nbsp;mm diameter [[United States penny|US 1&nbsp;cent]] coin for size comparison)''
|caption2=Refined rare-earth oxides are heavy, gritty powders usually brown or black, but can be lighter colors as shown here.{{longitem |''Legend:''<br />[[gadolinium]]{{·}}[[praseodymium]]{{·}}[[cerium]]<br />[[samarium]]{{·}}[[lanthanum]]<br />
[[neodymium]]|style=text-align: center; font-size: 0.9em;padding-top: 6px;}}
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The '''rare-earth elements''' ('''REE'''), also called the '''rare-earth metals''' or '''rare earths''', and sometimes the [[lanthanide]]s or lanthanoids (although [[scandium]] and [[yttrium]], which do not belong to this series, are usually included as rare earths),<ref>The 1985 [[International Union of Pure and Applied Chemistry]] "Red Book" (p.&nbsp;45) recommends that ''lanthanoid'' is used rather than ''lanthanide''. The ending "-ide" normally indicates a negative ion. However, owing to wide current usage, "lanthanide" is still allowed and is roughly analogous to rare-earth element.<br />{{RedBook2005|page=51}}</ref> are a set of 17 nearly indistinguishable lustrous silvery-white soft [[heavy metals]]. Compounds containing rare earths have diverse applications in electrical and electronic components, lasers, glass, magnetic materials, and industrial processes.

Scandium and yttrium are considered rare-earth elements because they tend to occur in the same [[ore]] deposits as the lanthanides and exhibit similar chemical properties, but have different electrical and [[magnetic properties]].<ref name="ASella2016"/><ref>{{cite book |title=The Elements |author=T Gray |publisher=Black Dog & Leventhal |year=2007 |pages=118–122 |chapter=Lanthanum and Cerium}}</ref> The term 'rare-earth' is a [[misnomer]] because they are not actually scarce, although historically it took a long time to isolate these elements.<ref>{{Cite news |date=2014-03-23 |title=Rare earths: Neither rare, nor earths |language=en-GB |work=BBC News |url=https://www.bbc.com/news/magazine-26687605 |access-date=2023-04-19}}</ref><ref>{{Cite web |last=Lee |first=Jordy |title=Rare Earths Explained |url=https://www.milkenreview.org/articles/rare-earths-explained |access-date=2023-04-19 |website=Milken Institute Review |language=en-US}}</ref>

These metals tarnish slowly in air at room temperature and react slowly with cold water to form hydroxides, liberating hydrogen. They react with steam to form oxides and ignite spontaneously at a temperature of {{cvt|400|C|F}}. These elements and their compounds have no biological function other than in several specialized enzymes, such as in lanthanide-dependent methanol dehydrogenases in bacteria.<ref>{{cite journal |last1=Huang |first1=Jing |last2=Yu |first2=Zheng |last3=Chistoserdova |first3=Ludmila |title=Lanthanide-Dependent Methanol Dehydrogenases of XoxF4 and XoxF5 Clades Are Differentially Distributed Among Methylotrophic Bacteria and They Reveal Different Biochemical Properties |journal=Frontiers in Microbiology |date=26 June 2018 |volume=9 |page=1366 |doi=10.3389/fmicb.2018.01366 |pmid=29997591 |pmc=6028718 |doi-access=free}}</ref> The water-soluble compounds are mildly to moderately toxic, but the insoluble ones are not.<ref>{{cite journal |last1=Malhotra |first1=Nemi |last2=Hsu |first2=Hua-Shu |last3=Liang |first3=Sung-Tzu |last4=Roldan |first4=Marri Jmelou M. |last5=Lee |first5=Jiann-Shing |last6=Ger |first6=Tzong-Rong |last7=Hsiao |first7=Chung-Der |date=2020-09-16 |title=An Updated Review of Toxicity Effect of the Rare Earth Elements (REEs) on Aquatic Organisms |journal=Animals |language=en |volume=10 |issue=9 |page=1663 |doi=10.3390/ani10091663 |issn=2076-2615 |pmc=552131 |pmid=32947815 |doi-access=free}}</ref> All isotopes of [[promethium]] are radioactive, and it does not occur naturally in the earth's crust, except for a trace amount generated by [[spontaneous fission]] of [[uranium-238]]. They are often found in minerals with [[thorium]], and less commonly [[uranium]].

Though rare-earth elements are technically relatively plentiful in the entire [[Earth's crust]] ([[cerium]] being the [[abundance of elements in Earth's crust|25th-most-abundant element]] at 68 parts per million, more abundant than [[copper]]), in practice this is spread thin across trace impurities, so to obtain rare earths at usable purity requires processing enormous amounts of raw ore at great expense, thus the name "rare" earths.

Because of their [[geochemical]] properties, rare-earth elements are typically dispersed and not often found concentrated in [[rare-earth mineral]]s. Consequently, economically exploitable [[ore|ore deposits]] are sparse.<ref name="Haxel02">{{cite web |url=http://pubs.usgs.gov/fs/2002/fs087-02/fs087-02.pdf |title=Rare Earth Elements—Critical Resources for High Technology |author=Haxel G. |author2=Hedrick J. |date=2002 |publisher=United States Geological Survey |editor=Peter H. Stauffer |editor2=James W. Hendley II |id=USGS Fact Sheet: 087-02 |access-date=2012-03-13 |quote=However, in contrast to ordinary base and [[precious 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. |author3=Orris J. |archive-date=December 14, 2010 |archive-url=https://web.archive.org/web/20101214095306/http://pubs.usgs.gov/fs/2002/fs087-02/fs087-02.pdf |url-status=live}}</ref> The first rare-earth mineral discovered (1787) was [[gadolinite]], a black mineral composed of cerium, yttrium, iron, silicon, and other elements. This mineral was extracted from a mine in the village of [[Ytterby]] in [[Sweden]]; four of the rare-earth elements bear names derived from this single location.

{{TOC limit|3}}

==Elements==
A table listing the 17 rare-earth elements, their [[atomic number]] and symbol, the etymology of their names, and their main uses (see also [[Lanthanide#Applications|Applications 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.

{| class="wikitable sortable"
|+Overview of rare-earth metal properties
|-
!scope="col"|[[Atomic number|Z]]
!scope="col"|Symbol
!scope="col"|Name
!scope="col" class="unsortable" |Etymology
!scope="col" class="unsortable" |Selected applications
!scope="col" data-sort-type="number" |Abundance<ref>{{cite web |url=https://geology.com/usgs/ree-geology/ |author1=Keith R. Long |author2=Bradley S. Van Gosen |author3=Nora K. Foley |author4=Daniel Cordier |title=The Geology of Rare Earth Elements |website=Geology.com |access-date=2018-06-19 |archive-date=October 26, 2021 |archive-url=https://web.archive.org/web/20211026102954/https://geology.com/usgs/ree-geology/ |url-status=live}}</ref><ref>{{cite book |editor-first=David R. |editor-last=Lide |title=CRC Handbook of Chemistry and Physics |date=1996–1997 |edition=77th |location=Boca Raton, Florida |publisher=CRC Press |isbn=0-8493-0477-6 |pages=10–12}}</ref><br/>(ppm{{efn|group=tab1|1=Parts per million in Earth's crust, e.g. Pb=13 ppm}})
|-
| style="text-align:center;" |21
| style="text-align:center;" |Sc
!scope="row"|[[Scandium]]
|from [[Latin]] ''Scandia'' ([[Scandinavia]]).
|Light [[aluminium-scandium alloy]]s for aerospace components, additive in [[metal-halide lamp]]s and [[mercury-vapor lamp]]s,<ref name="CRC_ed89_elements">{{cite book |author=C. R. Hammond |chapter=Section 4; The Elements |title=CRC Handbook of Chemistry and Physics |edition=89th |others=(Internet Version 2009) |editor=David R. Lide |publisher=CRC Press/Taylor and Francis |location=Boca Raton, FL}}</ref> radioactive tracing agent in oil refineries
| {{0}}22
|-
| style="text-align:center;" |39
| style="text-align:center;" |Y
!scope="row"|[[Yttrium]]
|after the village of [[Ytterby|Ytterby, Sweden]], where the first rare-earth ore was discovered.
|[[Yttrium aluminium garnet]] (YAG) laser, yttrium vanadate (YVO{{sub|4}}) as host for europium in television red phosphor, [[yttrium barium copper oxide|YBCO]] [[High-temperature superconductivity|high-temperature superconductors]], [[yttria-stabilized zirconia]] (YSZ) (used in [[tooth crowns]]; as refractory material - in metal alloys used in jet engines, and coatings of engines and industrial gas turbines; [[electroceramic]]s - for measuring oxygen and pH of hot water solutions, i.e. in fuel cells; ceramic electrolyte - used in [[solid 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,<ref name="CRC_ed89_elements"/> energy-efficient light bulbs (part of triphosphor white phosphor coating in fluorescent tubes, CFLs and CCFLs, and yellow phosphor coating in white LEDs),<ref>{{cite web |website=Think GlobalGreen |url=http://www.thinkglobalgreen.org/rare-earthmetals.html |title=Rare-earth metals |access-date=10 February 2017 |archive-url=https://web.archive.org/web/20161104194856/http://www.thinkglobalgreen.org/rare-earthmetals.html |archive-date=2016-11-04}}</ref> [[spark plug]]s, gas mantles, additive to steel, aluminium and magnesium alloys, [[cancer treatments]], camera and [[refractive telescope]] lenses (due to high refractive index and very low thermal expansion), battery cathodes (LYP)
| {{0}}33
|-
| style="text-align:center;" |57
| style="text-align:center;" |La
!scope="row"|[[Lanthanum]]
|from the Greek "lanthanein", meaning ''to be hidden''.
|High [[refractive index]] and alkali-resistant glass, flint, hydrogen storage, battery-electrodes, [[camera]] and [[refractive telescope]] lenses, [[fluid catalytic cracking]] catalyst for oil refineries
| {{0}}39
|-
| style="text-align:center;" |58
| style="text-align:center;" |Ce
!scope="row"|[[Cerium]]
|after the dwarf planet [[Ceres (dwarf planet)|Ceres]], named after [[Ceres (mythology)|the Roman goddess of agriculture]].
|Chemical [[oxidizing agent]], polishing powder, yellow colors in glass and ceramics, catalyst for [[self-cleaning oven]]s, [[fluid catalytic cracking]] catalyst for oil refineries, [[ferrocerium]] flints for lighters, robust intrinsically [[hydrophobic]] coatings for turbine blades<ref>{{cite journal |last1=Fronzi |first1=M |title=Theoretical insights into the hydrophobicity of low index CeO<sub>2</sub> surfaces |journal=Applied Surface Science |year=2019 |volume=478 |pages=68–74 |doi=10.1016/j.apsusc.2019.01.208 |arxiv=1902.02662 |url=https://hal.archives-ouvertes.fr/hal-02308396/document |bibcode=2019ApSS..478...68F |s2cid=118895100 |access-date=February 9, 2021 |archive-date=April 10, 2022 |archive-url=https://web.archive.org/web/20220410095114/https://hal.archives-ouvertes.fr/hal-02308396/document |url-status=live}}</ref>
| {{0}}66.5
|-
| style="text-align:center;" |59
| style="text-align:center;" |Pr
!scope="row"|[[Praseodymium]]
|from the Greek "prasios", meaning ''leek-green'', and "didymos", meaning ''twin''.
|[[Rare-earth magnet]]s, [[laser]]s, core material for [[carbon arc]] lighting, colorant in [[glass]]es and [[Vitreous enamel|enamel]]s, additive in [[didymium]] glass used in [[welding goggles]],<ref name="CRC_ed89_elements"/> [[ferrocerium]] firesteel (flint) products, single-mode fiber optical amplifiers (as a dopant of [[fluoride glass]])
| {{0|00}}9.2
|-
| style="text-align:center;" |60
| style="text-align:center;" |Nd
!scope="row"|[[Neodymium]]
|from the Greek "neos", meaning ''new'', and "didymos", meaning ''twin''.
|[[Rare-earth magnet]]s, [[laser]]s, violet colors in glass and ceramics, [[didymium]] glass, [[ceramic capacitor]]s, electric motors in electric automobiles
| {{0}}41.5
|-
| style="text-align:center;" |61
| style="text-align:center;" |Pm
!scope="row"|[[Promethium]]
|after the [[Titan (mythology)|Titan]] [[Prometheus]], who brought fire to mortals.
|[[Atomic battery|Nuclear batteries]], [[luminous paint]]
| data-sort-value="0" |{{0}}{{val|1e-15}}<ref>{{cite book |title=Ullmann's Encyclopedia of Industrial Chemistry |volume=31 |editor=Fritz Ullmann |others=Contributor: Matthias Bohnet |edition=6th |publisher=Wiley-VCH |year=2003 |isbn=978-3-527-30385-4 |page=24}}</ref>{{efn|group=tab1|1=Promethium has no [[stable isotope]]s or [[primordial radioisotope]]s; trace quantities occur in nature as [[fission product]]s.}}
|-
| style="text-align:center;" |62
| style="text-align:center;" |Sm
!scope="row"|[[Samarium]]
|after mine official, [[Vasili Samarsky-Bykhovets]].
|[[Rare-earth magnet]]s, [[laser]]s, [[neutron capture]], [[maser]]s, [[control rod]]s of [[nuclear reactor]]s
| {{0|00}}7.05
|-
| style="text-align:center;" |63
| style="text-align:center;" |Eu
!scope="row"|[[Europium]]
|after the continent of [[Europe]].
|Red and blue [[phosphor]]s, [[laser]]s, [[mercury-vapor lamp]]s, [[fluorescent lamp]]s, [[NMR]] [[relaxation (NMR)|relaxation agent]]
| {{0|00}}2
|-
| style="text-align:center;" |64
| style="text-align:center;" |Gd
!scope="row"|[[Gadolinium]]
|after [[Johan Gadolin]] (1760–1852), to honor his investigation of rare earths.
|High refractive index glass or [[garnet]]s, [[laser]]s, [[X-ray tube]]s, [[bubble memory|computer bubble memories]], [[neutron capture]], [[MRI contrast agent]], [[relaxation (NMR)|NMR relaxation agent]], steel and chromium alloys additive, [[magnetic refrigeration]] (using significant [[magnetocaloric effect]]), [[positron emission tomography]] [[scintillator]] detectors, a substrate for magneto-optical films, high performance [[high-temperature superconductor]]s, [[ceramic electrolyte]] used in [[solid oxide fuel cell]]s, [[oxygen]] detectors, possibly in catalytic conversion of automobile fumes.
| {{0|00}}6.2
|-
| style="text-align:center;" |65
| style="text-align:center;" |Tb
!scope="row"|[[Terbium]]
|after the village of [[Ytterby]], [[Sweden]].
|Additive in [[Neodymium magnet|neodymium based magnets]], green [[phosphor]]s, [[laser]]s, [[fluorescent lamp]]s (as part of the white triband phosphor coating), [[Magnetostriction|magnetostrictive alloys]] such as [[terfenol-D]], naval [[sonar]] systems, stabilizer of [[fuel cells]]
| {{0|00}}1.2
|-
| style="text-align:center;" |66
| style="text-align:center;" |Dy
!scope="row"|[[Dysprosium]]
|from the Greek "dysprositos", meaning ''hard to get''.
|Additive in [[neodymium magnet|neodymium based magnets]], [[laser]]s, [[magnetostriction|magnetostrictive alloys]] such as [[terfenol-D]], [[hard disk drives]]
| {{0|00}}5.2
|-
| style="text-align:center;" |67
| style="text-align:center;" |Ho
!scope="row"|[[Holmium]]
|after [[Stockholm]] (in Latin, "Holmia"), the native city of one of its discoverers.
|[[Laser]]s, wavelength calibration standards for optical [[spectrophotometry|spectrophotometer]]s, [[magnet]]s
| {{0|00}}1.3
|-
| style="text-align:center;" |68
| style="text-align:center;" |Er
!scope="row"|[[Erbium]]
|after the village of Ytterby, Sweden.
|Infrared [[laser]]s, [[vanadium steel]], [[optical fiber|fiber-optic]] technology
| {{0|00}}3.5
|-
| style="text-align:center;" |69
| style="text-align:center;" |Tm
!scope="row"|[[Thulium]]
|after the mythological northern land of [[Thule]].
|Portable [[X-ray machine]]s, [[metal-halide lamp]]s, [[laser]]s
| {{0|00}}0.52
|-
| style="text-align:center;" |70
| style="text-align:center;" |Yb
!scope="row"|[[Ytterbium]]
|after the village of Ytterby, Sweden.
|Infrared [[laser]]s, chemical [[reducing agent]], [[flare (countermeasure)|decoy flares]], [[stainless steel]], [[strain gauge]]s, [[nuclear medicine]], [[earthquake]] monitoring
| {{0|00}}3.2
|-
| style="text-align:center;" |71
| style="text-align:center;" |Lu
!scope="row"|[[Lutetium]]
|after [[Lutetia]], the city that later became [[Paris]].
|[[Positron emission tomography]] – PET scan detectors, high-refractive-index glass, [[lutetium tantalate]] hosts for phosphors, catalyst used in [[oil refinery|refineries]], [[LED light bulb]]
| {{0|00}}0.8
|}
{{notelist|group=tab1}}

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".<ref>Mentioned by Prof. [[Andrea Sella]] on a BBC [[Business Daily]] programme, March 19, 2014 [http://www.bbc.co.uk/podcasts/series/elements]. Unfortunately this mnemonic doesn't distinguish very well between terbium and thulium.</ref>

==Discovery and early history==

Rare earths were mainly discovered as components of minerals. Ytterbium was found in the "ytterbite" (renamed to [[gadolinite]] in 1800) discovered by Lieutenant [[Carl Axel Arrhenius]] in 1787 at a quarry in the village of [[Ytterby]], Sweden<ref>{{cite journal |editor=Gschneidner K. A., Cappellen |title=1787–1987 Two hundred Years of Rare Earths |journal=Rare Earth Information Center, IPRT, North-Holland |volume=IS-RIC 10 |year=1987}}</ref> and termed "rare" because it had never yet been seen.<ref name="auto">{{cite web |website=[[Science History Institute]] |title=The History and Future of Rare Earth Elements |date=October 18, 2019 |url=https://www.sciencehistory.org/learn/science-matters/case-of-rare-earth-elements-history-future |access-date=January 31, 2023}}</ref> Arrhenius's "ytterbite" reached [[Johan Gadolin]], a [[The Royal Academy of Turku|Royal Academy of Turku]] professor, and his analysis yielded an unknown [[oxide]] ("earth" in the geological parlance of the day<ref name="auto"/>), which he called [[yttrium(III) oxide|yttria]]. [[Anders Gustav Ekeberg]] isolated [[beryllium]] from the gadolinite but failed to recognize other elements in the ore. After this discovery in 1794, a mineral from [[Bastnäs]] near [[Riddarhyttan]], Sweden, which was believed to be an [[iron]]–[[tungsten]] mineral, was re-examined by [[Jöns Jacob Berzelius]] and [[Wilhelm Hisinger]]. In 1803 they obtained a white oxide and called it [[cerium(IV) oxide|ceria]]. [[Martin Heinrich Klaproth]] independently discovered the same oxide and called it ''ochroia''. 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 in [[nitric acid]]. He called the oxide of the soluble salt ''lanthana''. It took him three more years to separate the lanthana further into ''didymia'' and pure lanthana. Didymia, although not further separable by Mosander's techniques, was in fact still a mixture of oxides.

In 1842 Mosander also 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 called ''terbium''; the one that yielded yellow peroxide he called ''erbium''.

In 1842 the number of known rare-earth elements had reached six: yttrium, cerium, lanthanum, didymium, erbium, and terbium.

[[Nils Johan Berlin]] and [[Marc Delafontaine]] tried also to separate the crude yttria and found the same substances that Mosander obtained, but Berlin named (1860) the substance giving pink salts ''erbium'', and Delafontaine named the substance with the yellow peroxide ''terbium''. This confusion led to several false claims of new elements, such as the ''mosandrium'' of [[J. Lawrence Smith (chemist)|J. Lawrence Smith]], or the ''philippium'' and ''[[decipium]]'' of Delafontaine. Due to the difficulty in separating the metals (and determining the separation is complete), the total number of false discoveries was dozens,<ref>''[https://www.osti.gov/scitech/servlets/purl/789650 History of the Origin of the Chemical Elements and Their Discoverers]''</ref><ref>{{cite book |author1=Stephen David Barrett |author2=Sarnjeet S. Dhesi |title=The Structure of Rare-earth Metal Surfaces |url=https://books.google.com/books?id=7fxpDQAAQBAJ&pg=PA4 |year=2001 |publisher=World Scientific |isbn=978-1-86094-165-8 |page=4}}</ref> with some putting the total number of discoveries at over a hundred.<ref>''[https://archive.org/stream/OnRareAndScatteredMetalsTalesAboutMetals/On_Rare_And_Scattered_Metals__Tales_About_Metals On Rare And Scattered Metals: Tales About Metals]'', Sergei Venetsky</ref>

===Spectroscopic identification===
There were no further discoveries for 30 years, and the element [[didymium]] was listed in the periodic table of elements with a molecular mass of 138. In 1879, [[Marc Delafontaine|Delafontaine]] used the new physical process of [[atomic emission spectroscopy|optical flame spectroscopy]] and found several new spectral lines in didymia. Also in 1879, [[Paul Émile Lecoq de Boisbaudran]] isolated the new element ''[[samarium]]'' from the mineral [[samarskite]].

The samaria earth was further separated by Lecoq de Boisbaudran in 1886, and a similar result was obtained by [[Jean Charles Galissard de Marignac]] by direct isolation from samarskite. They named the element ''[[gadolinium]]'' after [[Johan Gadolin]], and its oxide was named "[[gadolinium(III) oxide|gadolinia]]".

Further spectroscopic analysis between 1886 and 1901 of samaria, yttria, and samarskite by [[William Crookes]], Lecoq de Boisbaudran and [[Eugène-Anatole Demarçay]] yielded several new [[spectral line]]s that indicated the existence of an unknown element. The [[fractional crystallization (chemistry)|fractional crystallization]] of the oxides then yielded ''[[europium]]'' in 1901.

In 1839 the third source for rare earths became available. This is a mineral similar to gadolinite called ''uranotantalum'' (now called "[[samarskite]]") an oxide of a mixture of elements such as yttrium, ytterbium, iron, uranium, thorium, calcium, niobium, and tantalum. This mineral from [[Miass]] in the southern [[Ural Mountains]] was documented by [[Gustav 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, and [[Heinrich Rose]] found only [[tantalum]] and [[niobium]] ([[columbium]]) in it.

The exact number of rare-earth elements that existed was highly unclear, and a maximum number of 25 was estimated. The use of [[X-ray emission spectroscopy|X-ray spectra]] (obtained by [[X-ray crystallography]]) by [[Henry Moseley|Henry Gwyn Jeffreys Moseley]] made it possible to assign atomic numbers to the elements. Moseley found that the exact number of lanthanides had to be 15, but that [[promethium|element 61]] had not yet been discovered. (This is promethium, a radioactive element whose most stable isotope has a half-life of just 18 years.)

Using these facts about atomic numbers from X-ray crystallography, Moseley also showed that [[hafnium]] (element 72) would not be a rare-earth element. Moseley was killed in [[World War I]] in 1915, years before hafnium was discovered. Hence, the claim of [[Georges Urbain]] that he had discovered element 72 was untrue. Hafnium is an element that lies in the periodic table immediately below [[zirconium]], and hafnium and zirconium have very similar chemical and physical properties.

==Sources and purification==
During the 1940s, [[Frank Spedding]] and others in the United States (during the [[Manhattan Project]]) developed chemical [[ion-exchange]] procedures for separating and purifying rare-earth elements. This method was first applied to the [[actinide]]s for separating [[plutonium-239]] and [[neptunium]] from [[uranium]], [[thorium]], [[actinium]], and the other actinides in the materials produced in [[nuclear reactor]]s. Plutonium-239 was very desirable because it is a [[fissile material]].

The principal sources of rare-earth elements are the minerals [[bastnäsite]] ({{chem2|RCO3F}}, where R is a mixture of rare-earth elements), [[monazite]] ({{chem2|XPO4}}, where X is a mixture of rare-earth elements and sometimes thorium), and [[loparite]] ({{chem2|(Ce,Na,Ca)(Ti,Nb)O3}}), and the [[laterite|lateritic]] ion-adsorption [[clay]]s. Despite their high relative abundance, [[rare-earth mineral]]s are more difficult to mine and extract than equivalent sources of [[transition metal]]s (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 as [[ion exchange]], fractional crystallization, and [[liquid–liquid extraction]] during the late 1950s and early 1960s.<ref>Spedding F., Daane A. H.: "The Rare Earths", John Wiley & Sons, Inc., 1961.</ref>

Some [[ilmenite]] concentrates contain small amounts of scandium and other rare-earth elements, which could be analysed by [[X-ray fluorescence]] (XRF).<ref>{{cite book |title=Hydrometallurgy of Rare Earths |last=Qi |first=Dezhi |publisher=Elsevier |year=2018 |isbn=978-0-12-813920-2 |pages=162–165}}</ref>

==Classification==
Before the time that [[ion exchange]] methods and [[elution]] were available, the separation of the rare earths was primarily achieved by repeated [[precipitation (chemistry)|precipitation]] or [[crystallization]]. 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.<ref name="coldfusion77">{{Cite web|url=http://n-t.ru/ri/ps/pb064.htm|title=Популярная библиотека химических элементов. Гадолиний|trans-title=Popular library of chemical elements. Gadolinium|language=ru|website=n-t.ru|access-date=2020-01-07}} Reprinted from {{cite book|author=<!--none-->|date=1977|title=Популярная библиотека химических элементов. Серебро — Нильсборий и далее|chapter=Гадолиний|trans-title=Popular library of chemical elements. Silver through nielsbohrium and beyond|trans-chapter=Gadolinium|language=ru|publisher=[[Nauka (publisher)|Nauka]]|quote=Но с гадолиния начинается иттриевая подгруппа редкоземельных элементов, а это значит, что на электронных оболочках его атомов должны быть электроны с антипараллельными спинами.}}</ref> The reason for this division arose from the difference in [[solubility]] 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.<ref>B. Smith Hopkins: "Chemistry of the rarer elements", D. C. Heath & Company, 1923.</ref> 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.<ref>{{Ullmann |volume=31 |page=184 |last1=McGill |first1=Ian |contribution=Rare Earth Elements |doi=10.1002/14356007.a22_607}}</ref> Today, the rare-earth elements are classified as light or heavy rare-earth elements, rather than in cerium and yttrium groups.

===Light versus heavy classification===
The classification of rare-earth elements is inconsistent between authors.<ref>{{cite book |url=http://site.ebrary.com/id/10660751 |title=Rare earth elements: a new approach to the nexus of supply, demand and use: exemplified along the use of neodymium in permanent magnets |last=Zepf |first=Volker |date=2013 |publisher=Springer |isbn=978-3-642-35458-8 |location=Berlin; London |language=en}}</ref> The most common distinction between rare-earth elements is made by [[atomic number]]s; 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).<ref name="Rollinson">{{cite book |last=Rollinson |first=Hugh R. |title=Using geochemical data: evaluation, presentation, interpretation |date=1993 |publisher=Longman Scientific & Technical |isbn=978-0-582-06701-1 |location=Harlow, Essex, England |oclc=27937350}}</ref> 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.<ref name=Brownlow>{{cite book |title=Geochemistry |last=Brownlow |first=Arthur H |date=1996 |publisher=Prentice Hall |oclc=33044175 |isbn=978-0-13-398272-5 |location=Upper Saddle River, N.J.}}</ref> Increasing atomic numbers between light and heavy rare-earth elements and decreasing [[atomic radius|atomic radii]] throughout the series causes chemical variations.<ref name=Brownlow/> Europium is exempt of this classification as it has two valence states: Eu{{sup|2+}} and Eu{{sup|3+}}.<ref name=Brownlow/> Yttrium is grouped as heavy rare-earth element due to chemical similarities.<ref name=gsl/> The break between the two groups is sometimes put elsewhere, such as between elements 63 (europium) and 64 (gadolinium).<ref>{{cite web |title=Seltene Erden – Daten & Fakten |url=https://www.oeko.de/oekodoc/1110/2011-001-de.pdf |publisher=Öko-Institut e.V. |date=Jan 2011}}</ref> 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.

==Origin==
Rare-earth elements, except [[scandium]], are heavier than [[iron]] and thus are produced by [[supernova nucleosynthesis]] or by the [[s-process]] in [[asymptotic giant branch]] stars. In nature, [[spontaneous fission]] of [[uranium-238]] produces trace amounts of radioactive [[promethium]], but most promethium is synthetically produced in nuclear reactors.

Due to their chemical similarity, the concentrations of rare earths in rocks are only slowly changed by geochemical processes, making their proportions useful for [[geochronology]] and dating fossils.

==Compounds==
Rare-earth elements occur in nature in combination with [[phosphate]] ([[monazite]]), [[carbonate]]-[[fluoride]] ([[bastnäsite]]), and oxygen anions.

In their oxides, most rare-earth elements only have a valence of 3 and form [[sesquioxide]]s (cerium forms {{chem2|CeO2}}). 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&nbsp;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 in [[space group]] ''I''2{{sub|1}}3 (no. 199),<ref>{{cite journal |last1=William Zachariasen |title=The Crystal Structure of the Modification C of the Sesquioxides of the Rare Earth Metals, and of Indium and Thallium |journal=[[Norsk Geologisk Tidsskrift]] |date=Jan 11, 1927 |volume=9 |pages=310–316 |url=https://njg.geologi.no/images/NJG_articles/NGT_09_3_4_310-316.pdf}}</ref> but is now known to be in space group ''Ia''{{overline|3}} (no. 206). The structure is similar to that of [[fluorite]] or [[cerium dioxide]] (in which the cations form a [[face-centred cubic]] lattice and the anions sit inside the tetrahedra of cations), except that one-quarter of the anions (oxygen) are missing. The [[unit cell]] of these sesquioxides corresponds to eight unit cells of fluorite or cerium dioxide, with 32 cations instead of 4. This is called the [[bixbyite]] structure, as it occurs in a mineral of that name ({{chem2|(Mn,Fe)2O3}}).<ref>{{cite journal |author=M. V. Abrashev |author2=N. D. Todorov |author3=J. Geshev |title=Raman spectra of R 2O3 (R—rare earth) sesquioxides with C-type bixbyite crystal structure: A comparative study |journal=Journal of Applied Physics |date=Sep 9, 2014 |volume=116 |issue=10 |page=103508 |doi=10.1063/1.4894775 |bibcode=2014JAP...116j3508A |hdl=10183/107858 |s2cid=55024339 }}</ref>

==Geological distribution==
[[File:Elemental abundances.svg|thumb|upright=2|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 is [[cerium]], which is actually the 25th most abundant element in [[crust (geology)|Earth's crust]], having 68 parts per million (about as common as copper). The exception is the highly unstable and radioactive [[promethium]] "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&nbsp;g in the entire Earth's crust).<ref>{{cite journal |author1=P. Belli |author2=R. Bernabei |author3=F. Cappella |author4=R. Cerulli |author5=C. J. Dai |author6=F. A. Danevich |author7=A. d'Angelo |author8=A. Incicchitti |author9=V. V. Kobychev |author10=S. S. Nagorny |author11=S. Nisi |author12=F. Nozzoli |author13=D. Prosperi |author14=V. I. Tretyak |author15=S. S. Yurchenko |year=2007 |title=Search for α decay of natural Europium |journal=Nuclear Physics A |volume=789 |issue=1–4 |pages=15–29 |doi=10.1016/j.nuclphysa.2007.03.001 |bibcode=2007NuPhA.789...15B}}</ref> 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 being [[technetium]]).

The rare-earth elements are often found together. During the sequential [[accretion (geology)|accretion]] 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 into [[Mantle (geology)|mantle]] rocks.<ref name="winter">{{cite book |title=Principles of igneous and metamorphic petrology |last=Winter |first=John D. |date=2010 |publisher=Prentice Hall |isbn=978-0-321-59257-6 |edition=2nd |location=New York |oclc=262694332}}</ref> The [[magnetic moment|high field strength]]{{Clarify|date=April 2021}} and large [[ionic radius|ionic 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.<ref name="winter"/> 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 the [[lanthanide 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 like [[garnet]].<ref name="winter"/><ref name="Michel">{{cite book |title=Geology of mineral resources |last1=Jébrak |first1=Michel |last2=Marcoux |first2=Eric |last3=Laithier |first3=Michelle |last4=Skipwith |first4=Patrick |publisher=Geological Association of Canada |isbn=978-1-897095-73-7 |edition=2nd |location=St. John's, NL |oclc=933724718 |year=2014}}</ref> 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.<ref name="winter"/>

Among the anhydrous rare-earth phosphates, it is the tetragonal mineral [[xenotime]] that incorporates yttrium and the HREE, whereas the monoclinic [[monazite]] 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 to [[chondrite|chondritic]] abundance than does cerium and the LREE. 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 the [[Oddo–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.<ref name=Powell/>

Well-known minerals containing yttrium, and other HREE, include gadolinite, xenotime, [[samarskite]], [[euxenite]], [[fergusonite]], yttrotantalite, yttrotungstite, yttrofluorite (a variety of [[fluorite]]), thalenite, and [[yttrialite]]. Small amounts occur in [[zircon]], which derives its typical yellow fluorescence from some of the accompanying HREE. The [[zirconium]] mineral [[eudialyte]], such as is found in southern [[Greenland]], 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 recovered [[monazite]] (which typically contains a few percent of yttrium). Uranium ores from Ontario have occasionally yielded yttrium as a byproduct.<ref name=Powell/>

Well-known minerals containing cerium, and other LREE, include [[bastnäsite]], [[monazite]], [[allanite]], [[loparite]], [[ancylite]], [[parisite]], [[lanthanite]], chevkinite, [[cerite]], [[stillwellite]], britholite, [[fluocerite]], and cerianite. Monazite (marine sands from [[Brazil]], [[India]], or [[Australia]]; rock from [[South Africa]]), bastnäsite (from [[Mountain Pass rare earth mine]], or several localities in China), and [[loparite]] ([[Kola Peninsula]], [[Russia]]) have been the principal ores of cerium and the light lanthanides.<ref name=Powell/>

Enriched deposits of rare-earth elements at the surface of the Earth, [[carbonatite]]s and [[pegmatite]]s, are related to alkaline [[plutonism]], an uncommon kind of magmatism that occurs in tectonic settings where there is rifting or that are near [[subduction]] zones.<ref name=Michel/> In a rift setting, the alkaline magma is produced by very small degrees of partial melting (<1%) of garnet peridotite in the [[upper mantle (Earth)|upper mantle]] (200 to 600&nbsp;km depth).<ref name=Michel/> 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 a [[diapir]], or [[diatreme]], along pre-existing fractures, and can be emplaced deep in [[crust (geology)|the crust]], or erupted at the surface. Typical REE enriched deposits types forming in rift settings are carbonatites, and A- and M-Type granitoids.<ref name=winter/><ref name=Michel/> Near subduction zones, partial melting of the subducting plate within the [[asthenosphere]] (80 to 200&nbsp;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.<ref name=winter/> 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.<ref name=winter/><ref name=Michel/>

Alkaline magmas enriched with rare-earth elements include carbonatites, peralkaline granites (pegmatites), and [[nepheline syenite]]. [[Carbonatite]]s crystallize from {{CO2}}-rich fluids, which can be produced by partial melting of hydrous-carbonated [[lherzolite]] to produce a CO{{sub|2}}-rich primary magma, by [[fractional crystallization (geology)|fractional crystallization]] of an alkaline primary magma, or by separation of a {{CO2}}-rich immiscible liquid from.<ref name=winter/><ref name=Michel/> These liquids are most commonly forming in association with very deep Precambrian [[craton]]s, like the ones found in Africa and the Canadian Shield.<ref name=winter/> Ferrocarbonatites are the most common type of carbonatite to be enriched in REE, and are often emplaced as late-stage, [[breccia]]ted 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.<ref name=winter/><ref name=Michel/> Large carbonatite deposits enriched in rare-earth elements include Mount Weld in Australia, Thor Lake in Canada, Zandkopsdrift in South Africa, and [[Mountain Pass rare earth mine|Mountain Pass]] in the USA.<ref name=Michel/> [[Pegmatite|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.<ref name=winter/><ref name=Michel/> 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.<ref name=Michel/> Economically viable pegmatites are divided into Lithium-Cesium-Tantalum (LCT) and Niobium-Yttrium-Fluorine (NYF) types; NYF types are enriched in rare-earth minerals. Examples of rare-earth pegmatite deposits include Strange Lake in Canada and Khaladean-Buregtey in Mongolia.<ref name=Michel/> Nepheline syenite (M-Type granitoids) deposits are 90% feldspar and feldspathoid minerals. They are deposited in small, circular massifs and contain high concentrations of [[rare-earth mineral|rare-earth-bearing accessory minerals]].<ref name=winter/><ref name=Michel/> For the most part, these deposits are small but important examples include Illimaussaq-Kvanefeld in Greenland, and Lovozera in Russia.<ref name=Michel/>

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 produces [[laterite]] 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.<ref name=Michel/>

In 2011, Yasuhiro Kato, a geologist at the [[University 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 in ''[[Nature 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."<ref name=Powell>Powell, Devin, [https://www.sciencenews.org/article/rare-earth-elements-plentiful-ocean-sediments "Rare earth elements plentiful in ocean sediments"], ''[[ScienceNews]]'', 3 July 2011. Via Kurt Brouwer's [http://blogs.marketwatch.com/fundmastery/2011/07/05/rare-earth-supply-demand/ Fundmastery Blog] {{Webarchive|url=https://web.archive.org/web/20110710022849/http://blogs.marketwatch.com/fundmastery/2011/07/05/rare-earth-supply-demand/ |date=July 10, 2011}}, ''MarketWatch'', 2011-07-05. Retrieved 2011-07-05.</ref><ref>{{cite journal |last1=Kato |first1=Yasuhiro |last2=Fujinaga |first2=Koichiro |last3=Nakamura |first3=Kentaro |last4=Takaya |first4=Yutaro |last5=Kitamura |first5=Kenichi |last6=Ohta |first6=Junichiro |last7=Toda |first7=Ryuichi |last8=Nakashima |first8=Takuya |last9=Iwamori |first9=Hikaru |date=2011 |title=Deep-sea mud in the Pacific Ocean as a potential resource for rare-earth elements |url=https://www.nature.com/articles/ngeo1185 |journal=Nature Geoscience |language=en |volume=4 |issue=8 |pages=535–539 |doi=10.1038/ngeo1185 |bibcode=2011NatGe...4..535K |issn=1752-0908}}</ref>

The global demand for rare-earth elements (REEs) is expected to increase more than fivefold by 2030.<ref>{{Cite web |title=Press corner |url=https://ec.europa.eu/commission/presscorner/home/en |access-date=2023-11-30 |website=European Commission - European Commission |language=en}}</ref><ref name=":170">{{Cite web |title=Europe Must Get Serious About Critical Minerals |url=https://www.eib.org/en/stories/critical-raw-materials-europe |access-date=2023-09-25 |website=European Investment Bank |language=en}}</ref>

==Geochemistry==
The REE geochemical classification is usually done on the basis of their [[atomic weight]]. One of the most common classifications divides REE into 3 groups: light rare earths (LREE - from <sub>57</sub>La to <sub>60</sub>Nd), intermediate (MREE - from <sub>62</sub>Sm to <sub>67</sub>Ho) and heavy (HREE - from <sub>68</sub>Er to <sub>71</sub>Lu). REE usually appear as trivalent ions, except for Ce and Eu which can take the form of Ce<sup>4+</sup> and Eu<sup>2+</sup> 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 have ''f'' 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 the [[shielding effect]] towards the nuclear charge due to the progressive filling of the 4''f'' orbital which acts against the electrons of the 6''s'' and 5''d'' 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. The effect of the lanthanide contraction can be observed in the REE behaviour both in a CHARAC-type geochemical system (CHArge-and-RAdius-Controlled<ref>{{cite journal |last=Bau |first=Michael |date=1996-04-01 |title=Controls on the fractionation of isovalent trace elements in magmatic and aqueous systems: evidence from Y/Ho, Zr/Hf, and lanthanide tetrad effect |journal=Contributions to Mineralogy and Petrology |language=en |volume=123 |issue=3 |pages=323–333 |doi=10.1007/s004100050159 |bibcode=1996CoMP..123..323B |s2cid=97399702 |issn=1432-0967}}</ref>) 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 the [[ionic 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 Ho<sup>3+</sup> (0.901 Å) to be almost identical to that of Y<sup>3+</sup> (0.9 Å), justifying the inclusion of the latter among the REE.

===Applications===
The application of rare-earth elements to geology is important to understanding the petrological processes of [[igneous rock|igneous]], [[sedimentary rock|sedimentary]] and [[metamorphic rock|metamorphic]] rock formation. In [[geochemistry]], rare-earth elements can be used to infer the petrological mechanisms that have affected a rock due to the subtle [[atomic radius|atomic size]] differences between the elements, which causes preferential [[fractional crystallization (geology)|fractionation]] 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 to [[chondrite|chondritic meteorites]], as these are believed to be the closest representation of [[fractional crystallization (geology)|unfractionated]] 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 odd [[atomic number]]s. 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:
:<math>[\text{REE}_i]_n = \frac{[\text{REE}_i]_\text{sam}}{[\text{REE}_i]_\text{std}}</math>

where '''''n''''' indicates the normalized concentration, <math>{[\text{REE}_i]_\text{sam}}</math> the analytical concentration of the element measured in the sample, and <math>{[\text{REE}_i]_\text{ref}}</math> the concentration of the same element in the reference material.<ref>{{cite journal |last1=Alibo |first1=Dia Sotto |last2=Nozaki |first2=Yoshiyuki |date=1999-02-01 |title=Rare earth elements in seawater: particle association, shale-normalization, and Ce oxidation |url=https://www.sciencedirect.com/science/article/pii/S0016703798002798 |journal=Geochimica et Cosmochimica Acta |language=en |volume=63 |issue=3 |pages=363–372 |doi=10.1016/S0016-7037(98)00279-8 |bibcode=1999GeCoA..63..363S |issn=0016-7037}}</ref>

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.<ref name="Rollinson"/>

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:
:<math>\frac{\text{REE}_i}{\text{REE}_i^*} = \frac{[\text{REE}_i]_n \times 2}{[\text{REE}_{i-1}]_n + [\text{REE}_{i+1}]_n}</math>

where <math>[\text{REE}_i]_n</math> is the normalized concentration of the element whose anomaly has to be calculated, <math>[\text{REE}_{i-1}]_n</math> and <math>[\text{REE}_{i+1}]_n</math> 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.<ref name=Rollinson/> Fractionation is in turn a function of the [[partition coefficient]]s 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'.<ref name=Rollinson/> 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 in [[felsic]] melts, the following observations apply: anomalies in europium are dominated by the crystallization of [[feldspar]]s. [[Hornblende]], controls the enrichment of MREE compared to LREE and HREE. Depletion of LREE relative to HREE may be due to the crystallization of [[olivine]], [[pyroxene|orthopyroxene]], and [[pyroxene|clinopyroxene]]. On the other hand, the depletion of HREE relative to LREE may be due to the presence of [[garnet]], as garnet preferentially incorporates HREE into its crystal structure. The presence of [[zircon]] may also cause a similar effect.<ref name=Rollinson/>

In sedimentary rocks, rare-earth elements in [[clastic rock|clastic 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.<ref name=Rollinson/>

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 vent]]s, and [[aeolian processes|aeolian]] sources;<ref name=Rollinson/> this is important in the investigation of ocean mixing and circulation.<ref name=gsl>{{cite web |author=Working Group |url=https://www.geolsoc.org.uk/~/media/shared/documents/policy/Rare%20Earth%20Elements%20briefing%20note%20final%20%20%20new%20format.pdf |title=Rare Earth Elements |date=December 2011 |publisher=Geological Society of London |access-date=18 May 2018 |archive-date=February 9, 2022 |archive-url=https://web.archive.org/web/20220209233309/https://www.geolsoc.org.uk/~/media/shared/documents/policy/Rare%20Earth%20Elements%20briefing%20note%20final%20%20%20new%20format.pdf |url-status=live}}</ref>

Rare-earth elements are also useful for dating rocks, as some [[radioactive isotope]]s display long half-lives. Of particular interest are the {{sup|138}}La-{{sup|138}}Ce, [[samarium-147|{{sup|147}}Sm]]-{{sup|143}}Nd, and {{sup|176}}Lu-{{sup|176}}Hf systems.<ref name=gsl/>

==Production==
[[File:Rareearth production.svg|thumb|Global production 1950–2000|upright=1.5]]
Until 1948, most of the world's rare earths were sourced from [[placer deposit|placer]] sand deposits in [[India]] and [[Brazil]]. Through the 1950s, South Africa was the world's rare earth source, from a monazite-rich reef at the [[Steenkampskraal mine]] in [[Western Cape]] province.<ref name=Rose60>{{cite web |last1=Rose |first1=Edward Roderick |title=Rare Earths of the Grenville Sub-Province, Ontario and Quebec |date=4 February 1960 |issue=Paper 59–10 |url=http://ftp.maps.canada.ca/pub/nrcan_rncan/publications/ess_sst/101/101254/pa_59_10.pdf |access-date=18 May 2018 |publisher=Geological Survey of Canada |location=Ottawa}}{{Dead link|date=January 2023 |bot=InternetArchiveBot |fix-attempted=yes}}</ref> Through the 1960s until the 1980s, the [[Mountain 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 in [[Inner Mongolia]],<ref name="Haxel02"/><ref name="Wikinvest">[https://www.wikinvest.com/China%27s_Rare_Earth_Dominance China's Rare Earth Dominance], Wikinvest. Retrieved on 11 Aug 2010.</ref> although it had only 36.7% of reserves. Australia was the second and only other major producer with 15% of world production.<ref>{{cite book |last1=Gambogi |first1=Joseph |title=Mineral Commodity Summaries |date=January 2018 |publisher=U.S. Geological Survey |pages=132–133 |chapter-url=https://minerals.usgs.gov/minerals/pubs/commodity/rare_earths/mcs-2018-raree.pdf |access-date=14 February 2018 |chapter=Rare Earths |archive-date=January 25, 2019 |archive-url=https://web.archive.org/web/20190125055346/https://minerals.usgs.gov/minerals/pubs/commodity/rare_earths/mcs-2018-raree.pdf |url-status=live}}</ref> All of the world's heavy rare earths (such as dysprosium) come from Chinese rare-earth sources such as the [[polymetal]]lic [[Bayan Obo]] deposit.<ref name="Wikinvest"/><ref>Chao E. C. T., Back J. M., Minkin J., Tatsumoto M., Junwen W., Conrad J. E., McKee E. H., Zonglin H., Qingrun M. [http://pubs.usgs.gov/bul/b2143/ "Sedimentary carbonate‐hosted giant Bayan Obo REE‐Fe‐Nb ore deposit of Inner Mongolia, China; a cornerstone example for giant polymetallic ore deposits of hydrothermal origin"] {{Webarchive|url=https://web.archive.org/web/20220120135314/http://pubs.usgs.gov/bul/b2143/ |date=January 20, 2022}}. 1997. United States Geological Survey. 29 February 2008. Bulletin 2143.</ref> The Browns Range mine, located 160&nbsp;km south east of [[Halls Creek]] in northern [[Western Australia]], was under development   in 2018 and is positioned to become the first significant dysprosium producer outside of China.<ref>{{cite web |url=http://northernminerals.com.au/browns-range/overview/ |title=Overview |publisher=Northern Minerals Limited |access-date=2018-04-21 |archive-date=August 6, 2020 |archive-url=https://web.archive.org/web/20200806170453/http://northernminerals.com.au/browns-range/overview/ }}</ref>

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.<ref>{{cite web |url=https://pubs.usgs.gov/fs/2014/3078/pdf/fs2014-3078.pdf |title=The Rare-Earth Elements—Vital to Modern Technologies and Lifestyles |date=November 2014 |publisher=United States Geological Survey |access-date=2018-03-13 |archive-date=January 19, 2022 |archive-url=https://web.archive.org/web/20220119103001/http://pubs.usgs.gov/fs/2014/3078/pdf/fs2014-3078.pdf |url-status=live}}</ref>
Increased demand has strained supply, and there is growing concern that the world may soon face a shortage of the rare earths.<ref>{{cite web |url=http://theanchorhouse.com/ |title=Cox C. 2008. Rare earth innovation. Herndon (VA): The Anchor House Inc; |access-date=2008-04-19 |archive-date=July 8, 2022 |archive-url=https://web.archive.org/web/20220708230509/https://www.theanchorhouse.com/ |url-status=live}}</ref> In several years from 2009 worldwide demand for rare-earth elements is expected to exceed supply by 40,000 tonnes annually unless major new sources are developed.<ref name=Reuters>[https://www.reuters.com/article/newsOne/idUSTRE57U02B20090831 "As hybrid cars gobble rare metals, shortage looms"] {{Webarchive|url=https://web.archive.org/web/20220605204539/https://www.reuters.com/article/newsOne/idUSTRE57U02B20090831 |date=June 5, 2022}}. Reuters. August 31, 2009. Retrieved Aug 31, 2009.</ref> 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. Furthermore, 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.<ref name=Massari>{{cite journal |date=2013-03-01 |title=Rare earth elements as critical raw materials: Focus on international markets and future strategies |journal=Resources Policy |language=en |volume=38 |issue=1 |pages=36–43 |doi=10.1016/j.resourpol.2012.07.001 |issn=0301-4207 |last1=Massari |first1=Stefania |last2=Ruberti |first2=Marcello|bibcode=2013RePol..38...36M }}</ref> In addition there are over a hundred ongoing mining projects with many options outside of China.<ref>{{Cite journal |last=Liu |first=Shuang-Liang |last2=Fan |first2=Hong-Rui |last3=Liu |first3=Xuan |last4=Meng |first4=Jianyin |last5=Butcher |first5=Alan R. |last6=Yann |first6=Lahaye |last7=Yang |first7=Kui-Feng |last8=Li |first8=Xiao-Chun |date=2023-06-01 |title=Global rare earth elements projects: New developments and supply chains |url=https://linkinghub.elsevier.com/retrieve/pii/S0169136823001439 |journal=Ore Geology Reviews |volume=157 |pages=105428 |doi=10.1016/j.oregeorev.2023.105428 |issn=0169-1368|doi-access=free }}</ref>

===China===
{{See also|Rare earths trade dispute}}

These concerns have intensified due to the actions of China, the predominant supplier.<ref>{{cite magazine |magazine=Foreign Affairs |url=https://www.foreignaffairs.com/articles/china/2012-04-25/china-digs-it |title=China Digs It |first=Damien |last=Ma |date=25 April 2012 |access-date=10 February 2017 |archive-date=April 10, 2022 |archive-url=https://web.archive.org/web/20220410095515/https://www.foreignaffairs.com/articles/china/2012-04-25/china-digs-it |url-status=live}}</ref> Specifically, China has announced regulations on exports and a crackdown on smuggling.<ref name="Livergood2010">{{cite web |author=Livergood, R. |url=http://csis.org/files/publication/101005_DIIG_Current_Issues_no22_Rare_earth_elements.pdf |title=Rare Earth Elements: A Wrench in the Supply Chain |date=5 October 2010 |publisher=Center for Strategic and International Studies |access-date=2012-03-13 |archive-date=February 12, 2011 |archive-url=https://web.archive.org/web/20110212024126/http://csis.org/files/publication/101005_DIIG_Current_Issues_no22_Rare_earth_elements.pdf |url-status=live}}</ref> 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.<ref>{{cite web |url=http://www.manufacturing.net/article.aspx?id=215574 |title=China To Limit Rare Earths Exports |archive-url=https://web.archive.org/web/20110726201410/http://www.manufacturing.net/article.aspx?id=215574 |archive-date=2011-07-26 |website=Manufacturing.net, 1 September 2009. |access-date=2010-08-30}}</ref> 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."<ref>{{cite web |url=http://thehill.com/blogs/e2-wire/677-e2-wire/124853-china-to-cut-exports-of-rare-earth-minerals-vital-to-energy-tech |title=China to cut exports of 'rare earth' minerals vital to energy tech |archive-url=https://web.archive.org/web/20101021053554/http://thehill.com/blogs/e2-wire/677-e2-wire/124853-china-to-cut-exports-of-rare-earth-minerals-vital-to-energy-tech |archive-date=2010-10-21 |website=The Hill's E{{sup |2}} Wire |author=Ben Geman |date=19 Oct 2009 |access-date=2010-10-19}}</ref> 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.<ref>{{cite web |date=January 18, 2011 |url=http://thechinaperspective.com/articles/china039srareearthexportssurgeinvalue8111/index.html |author=Tony Jin |title=China's Rare Earth Exports Surge in Value |website=The China Perspective |access-date=January 19, 2011 |archive-url=https://web.archive.org/web/20110213042905/http://thechinaperspective.com/articles/china039srareearthexportssurgeinvalue8111/index.html |archive-date=2011-02-13}}</ref> 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 tonnes.<ref>{{cite web |author1=Zhang Qi |author2=Ding Qingfen |author3=Fu Jing |title=Rare earths export quota unchanged |url=http://www.chinadaily.com.cn/bizchina/2011-07/15/content_12910072.htm |work=China Daily |date=2011-07-15 |archive-url=https://web.archive.org/web/20110724114258/http://www.chinadaily.com.cn/bizchina/2011-07/15/content_12910072.htm |archive-date=2011-07-24}}</ref> 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.<ref name=ReutersSept611/> 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.<ref name=reuters>{{cite web |url=https://www.reuters.com/article/china-trade-eu-idUSL5E8ED6520120313 |title=WRAPUP 4-US, EU, Japan take on China at WTO over rare earths |date=13 March 2017 |access-date=10 February 2017 |website=Reuters |archive-date=June 26, 2022 |archive-url=https://web.archive.org/web/20220626172529/https://www.reuters.com/article/china-trade-eu-idUSL5E8ED6520120313 |url-status=live}}</ref><ref name="Distillations"/> In August 2012, China announced a further 20% reduction in production.<ref>{{cite web |url=http://www.cnn.com/2012/08/08/business/china-rare-earth/index.html?section=money_news_international |author=Kevin Voigt |website=CNN |title=China cuts mines vital to tech industry |date=August 8, 2012 |access-date=August 8, 2012 |archive-date=May 7, 2021 |archive-url=https://web.archive.org/web/20210507144841/https://www.cnn.com/2012/08/08/business/china-rare-earth/index.html?section=money_news_international |url-status=live}}</ref>
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.<ref name="Distillations"/>

In response to the opening of new mines in other countries ([[Lynas]] in Australia and [[Molycorp]] in the United States), prices of rare earths dropped.<ref>{{cite web |url=https://www.theregister.co.uk/2012/12/23/rare_earth_non_monopoly/ |title=El Reg man: Too bad, China – I was RIGHT about hoarding rare earths |date=23 Dec 2012 |author=Tim Worstall |website=The Register |access-date=10 February 2017 |archive-date=February 1, 2020 |archive-url=https://web.archive.org/web/20200201021147/https://www.theregister.co.uk/2012/12/23/rare_earth_non_monopoly/ |url-status=live}}</ref>
The price of dysprosium oxide was US$994/kg in 2011, but dropped to US$265/kg by 2014.<ref name=WTI>{{cite web |title=China scraps quotas on rare earths after WTO complaint |website=The Guardian |date=Jan 5, 2015 |url=https://www.theguardian.com/world/2015/jan/05/china-scraps-quotas-rare-earth-wto-complaint |access-date=Jan 5, 2015 |url-status=live |archive-url=https://web.archive.org/web/20220615084158/https://www.theguardian.com/world/2015/jan/05/china-scraps-quotas-rare-earth-wto-complaint |archive-date=June 15, 2022}}</ref>

On August 29, 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.<ref name=WTO>{{cite web |url=http://www.wto.org/english/tratop_e/dispu_e/cases_e/ds431_e.htm |title=DS431: China — Measures Related to the Exportation of Rare Earths, Tungsten and Molybdenum |access-date=May 1, 2014 |publisher=[[World Trade Organization]] |archive-date=June 30, 2022 |archive-url=https://web.archive.org/web/20220630141201/https://www.wto.org/english/tratop_e/dispu_e/cases_e/ds431_e.htm |url-status=live}}</ref>

In 2019, [[China]] supplied between 85% and 95% of the global demand for the 17 rare-earth powders, half of them sourced from [[Myanmar]].<ref>R. Castellano (Jun. 02, 2019). [https://seekingalpha.com/article/4267839-china-trade-invest-based-on-rare-earth-price-hikes "China Trade - Invest Based On Rare Earth Price Hikes"] {{Webarchive|url=https://web.archive.org/web/20220626125758/https://seekingalpha.com/article/4267839-china-trade-invest-based-on-rare-earth-price-hikes |date=June 26, 2022}}. ''seekingalpha.com''. Retrieved 25 February 2021.</ref> {{Dubious|date=July 2022}} After the [[2021 Myanmar coup d'état|2021 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-act [[economic sanction]]s imposed by the US and EU countries. Rare-earth metals serve as crucial materials for [[electric vehicle]] manufacturing and high-tech military applications.<ref>S. Burns (Feb. 16, 2021). [https://agmetalminer.com/2021/02/16/rare-earths-are-the-next-geopolitical-chess-game/ "Rare earths are the next geopolitical chess game"] {{Webarchive|url=https://web.archive.org/web/20220615124349/https://agmetalminer.com/2021/02/16/rare-earths-are-the-next-geopolitical-chess-game/ |date=June 15, 2022}}. ''MetalMiner.com''. Retrieved 25 February 2021.</ref>

===Myanmar (Burma)===
[[Kachin State]] in Myanmar is the world's largest source of rare earths.<ref name=":03">{{cite web |date=2022-08-09 |title=New evidence shows massive and rapid expansion of illicit rare earths industry in Myanmar, fuelling human rights abuses, environmental destruction and funding military-linked militias |url=https://www.globalwitness.org/en/press-releases/new-evidence-shows-massive-and-rapid-expansion-illicit-rare-earths-industry-myanmar-fuelling-human-rights-abuses-environmental-destruction-and-funding-military-linked-militias/ |access-date=2023-03-27 |website=Global Witness |language=en}}</ref> In 2021, China imported {{US$|200 million}} of rare earths from Myanmar in December 2021, exceeding 20,000 tonnes.<ref name=":1">{{cite web |date=2022-08-09 |title=Myanmar's poisoned mountains |url=https://www.globalwitness.org/en/campaigns/natural-resource-governance/myanmars-poisoned-mountains/ |access-date=2023-03-27 |website=Global Witness |language=en}}</ref> Rare earths were discovered near [[Pang War]] in [[Chipwi Township]] along the [[China–Myanmar border]] in the late 2010s.<ref name=":2">{{cite web |title=Illegal rare earth mining harms environment in Myanmar's Kachin state |url=https://www.rfa.org/english/news/myanmar/mining-03102022184456.html |access-date=2023-03-27 |website=Radio Free Asia |language=en}}</ref> As China has shut down domestic mines due to the detrimental environmental impact, it has largely outsourced rare-earth mining to Kachin State.<ref name=":1"/> Chinese companies and miners illegally set up operations in Kachin State without government permits, and instead circumvent the central government by working with a [[Border Guard Forces|Border Guard Force]] militia under the [[Tatmadaw]], formerly known as the [[New Democratic Army – Kachin]], which has profited from this extractive industry.<ref name=":1"/><ref>{{cite web |last=Makichuk |first=Dave |date=2021-05-03 |title=Is Myanmar's junta benefiting from rare-earth boom? |url=https://asiatimes.com/2021/05/is-myanmars-junta-benefitting-from-rare-earth-boom/ |access-date=2023-03-27 |website=Asia Times |language=en-US}}</ref> {{As of|2022|March}}, 2,700 mining collection pools scattered across 300 separate locations were found in Kachin State, encompassing the area of [[Singapore]], and an exponential increase from 2016.<ref name=":1"/> Land has also been seized from locals to conduct mining operations.<ref name=":1"/>

===Other countries===
As a result of the increased demand and tightening restrictions on exports of the metals from China, some countries are stockpiling rare-earth resources.<ref>{{cite news |url=http://business.financialpost.com/2011/09/06/eu-stockpiles-rare-earths-as-tensions-with-china-rise/ |work=Financial Post |title=EU stockpiles rare earths as tensions with China rise |agency=Reuters |date=September 6, 2011 |access-date=2011-09-07 |archive-date=July 19, 2014 |archive-url=https://web.archive.org/web/20140719233436/http://business.financialpost.com/2011/09/06/eu-stockpiles-rare-earths-as-tensions-with-china-rise/ |url-status=live}}</ref> Searches for alternative sources in [[Australia]], [[Brazil]], [[Canada]], [[South Africa]], [[Tanzania]], [[Greenland]], and the [[United States]] are ongoing.<ref>{{cite news |url=https://www.nytimes.com/2009/09/10/business/global/10mineral.html?scp=10&sq=brazil&st=nyt |title=Canadian Firms Step Up Search for Rare-Earth Metals |agency=Reuters |work=[[The New York Times]] |date=September 9, 2009 |access-date=2009-09-15 |archive-date=April 10, 2022 |archive-url=https://web.archive.org/web/20220410095515/https://www.nytimes.com/2009/09/10/business/global/10mineral.html?scp=10&sq=brazil&st=nyt |url-status=live}}</ref> 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 many [[barriers to entry]].<ref name=Livergood2010/><ref name="Leifert2010">{{cite magazine |author=Leifert, H. |title=Restarting US rare earth production? |magazine=Earth |date=June 2010 |pages=20–21}}</ref> Significant sites under development outside China include [[Steenkampskraal mine|Steenkampskraal]] 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.<ref>{{cite magazine |editor-last=Casey |editor-first=Jessica |date=5 February 2022 |title=Monoceros Mineral Resources invests in Steenkampskraal Rare Earths |magazine=Global Mining Review |url=https://www.globalminingreview.com/finance-business/15022022/monoceros-mineral-resources-invests-in-steenkampskraal-rare-earths/ }}</ref> Over 80% of the infrastructure is already complete.<ref>{{cite web |url=https://www.steenkampskraal.com/the-mine/ |title=About The Mine |website=Steenkampskraal Rare Earths Mine |date=May 3, 2016 |language=en-US |access-date=2019-07-19 |archive-date=May 17, 2022 |archive-url=https://web.archive.org/web/20220517013624/https://www.steenkampskraal.com/the-mine/ |url-status=live}}</ref> Other mines include the Nolans Project in Central Australia, the [[Bokan Mountain]] project in Alaska, the remote [[Hoidas Lake]] project in northern Canada,<ref>{{cite web |url=http://www.gwmg.ca/pdf/Insinger_Report.pdf |author=Lunn, J. |date=2006 |title=Great western minerals |location=London |publisher=Insigner Beaufort Equity Research |access-date=2008-04-19 |archive-url=https://web.archive.org/web/20080409121623/http://www.gwmg.ca/pdf/Insinger_Report.pdf |archive-date=2008-04-09}}</ref> and the [[Mount Weld]] project in Australia.<ref name=Wikinvest/><ref name="Leifert2010"/><ref>{{cite news |url=https://www.reuters.com/article/idUSN2838509920090831 |title=California mine digs in for 'green' gold rush |access-date=2010-03-22 |work=Reuters |date=August 30, 2009 |first=Steve |last=Gorman |archive-date=April 10, 2022 |archive-url=https://web.archive.org/web/20220410095515/https://www.reuters.com/article/idUSN2838509920090831 |url-status=live}}</ref> The [[Hoidas Lake]] project has the potential to supply about 10% of the $1 billion of REE consumption that occurs in North America every year.<ref>{{cite web |url=http://www.gwmg.ca/projects/hoidas-lake |title=Hoidas Lake, Saskatchewan |publisher=Great Western Mineral Group Ltd. |access-date=2008-09-24 |archive-url=https://web.archive.org/web/20090331102738/http://www.gwmg.ca/projects/hoidas-lake |archive-date=2009-03-31}}</ref> [[Vietnam]] signed an agreement in October 2010 to supply Japan with rare earths<ref name="supply deal">{{cite news
|url=https://www.bbc.co.uk/news/world-asia-pacific-11661330
|title=Rare earths supply deal between Japan and Vietnam
|work=BBC News
|date=31 October 2010
|access-date=June 21, 2018
|archive-date=July 3, 2022
|archive-url=https://web.archive.org/web/20220703011024/https://www.bbc.co.uk/news/world-asia-pacific-11661330
|url-status=live
}}</ref> from its [[Tây Bắc|northwestern]] [[Lai Châu Province]],<ref>{{cite news
|url=http://english.aljazeera.net/news/asia-pacific/2010/10/2010103191334878158.html
|title=Vietnam signs major nuclear pacts |publisher=[[Al Jazeera Media Network|AlJazeera]] |date=31 October 2010 |access-date=31 October 2010}}</ref> however the deal was never realized due to disagreements.<ref>{{cite web |last=VnExpress |title=Gần 10 năm chưa khai thác được đất hiếm |url=https://vnexpress.net/gan-10-nam-chua-khai-thac-duoc-dat-hiem-4537518.html |access-date=2022-12-24 |website=vnexpress.net |language=vi}}</ref>

The largest rare-earth deposit in the U.S. is at [[Mountain Pass rare earth mine|Mountain Pass]], California, sixty miles south of [[Las Vegas]]. Originally opened by [[Molycorp]], the deposit has been mined, off and on, since 1951.<ref name=Wikinvest/><ref>{{cite web |title=Mountain Pass Mine |publisher=Mindat |url=https://www.mindat.org/loc-11616.html |archive-url=https://web.archive.org/web/20220909142430/https://www.mindat.org/loc-11616.html |archive-date=9 September 2022 |url-status=live}}</ref> A second large deposit of REEs at Elk Creek in southeast [[Nebraska]]<ref name="Lasley-2022">{{cite magazine |last=Lasley |first=Shane |date=6 September 2022 |title=Elk Creek deposit proves to be rare earth |magazine=Metal Tech News |url=https://www.metaltechnews.com/story/2022/05/25/tech-metals/elk-creek-deposit-proves-to-be-rare-earth/947.html |archive-url=https://web.archive.org/web/20220909141058/https://www.metaltechnews.com/story/2022/05/25/tech-metals/elk-creek-deposit-proves-to-be-rare-earth/947.html |archive-date=9 September 2022 |url-status=live}}</ref> is under consideration by NioCorp Development Ltd <ref>{{cite web |title=Mining Venture Draws $200 Million in Tax Incentives and Red Flags (1) |url=https://news.bloombergtax.com/daily-tax-report-state/mining-venture-draws-200-million-in-tax-incentives-and-red-flags |access-date=2020-12-01 |website=news.bloombergtax.com |language=en |archive-date=June 18, 2022 |archive-url=https://web.archive.org/web/20220618141715/https://news.bloombergtax.com/daily-tax-report-state/mining-venture-draws-200-million-in-tax-incentives-and-red-flags |url-status=live}}</ref> who hopes to open a niobium, scandium, and titanium mine there.<ref>{{cite news |url=http://www.omaha.com/money/long-discussed-niobium-mine-in-southeast-nebraska-is-ready-to/article_33913f7a-93fa-11e7-9144-8f1cad9c36eb.html |title=Long-discussed niobium mine in southeast Nebraska is ready to move forward, if it gathers $1 billion in financing |access-date=2019-05-18 |archive-date=May 11, 2020 |archive-url=https://web.archive.org/web/20200511210056/https://www.omaha.com/money/long-discussed-niobium-mine-in-southeast-nebraska-is-ready-to/article_33913f7a-93fa-11e7-9144-8f1cad9c36eb.html |url-status=live}}</ref> That mine may be able to produce as much as 7200 tonnes of ferro niobium and 95 tonnes of scandium trioxide annually,<ref>{{cite web |url=http://niocorp.com/wp-content/uploads/NIoCorp_Corporate_Presentation.pdf |title=NioCorp Superalloy Materials The Elk Creek Superalloy Materials Project |access-date=2019-05-18 |archive-date=August 19, 2021 |archive-url=https://web.archive.org/web/20210819204036/http://niocorp.com/wp-content/uploads/NIoCorp_Corporate_Presentation.pdf }}</ref> although, as of 2022, financing is still in the works.<ref name="Lasley-2022"/>

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 the [[Longonjo#Economy|Longonjo mine]] in Angola and other sources as they become available.<ref>{{cite web |title=Building an independent and sustainable supply of magnet metal rare earths for the Electric Vehicle and Offshore Wind OEMs |date=18 August 2022 |publisher=Pensana Plc |url=https://pensana.co.uk/wp-content/uploads/2022/08/RNS-REACH-Pensana-to-provide-magnet-metal-rare-earths-to-electric-vehicle-and-offshore-wind-OEMs_18August-2022-003.pdf |archive-url=https://web.archive.org/web/20220909152152/https://pensana.co.uk/wp-content/uploads/2022/08/RNS-REACH-Pensana-to-provide-magnet-metal-rare-earths-to-electric-vehicle-and-offshore-wind-OEMs_18August-2022-003.pdf |archive-date=9 September 2022 |url-status=live}}</ref><ref name="Arnoldi">{{cite magazine |last=Arnoldi |first=Marleny |date=25 May 2022 |title=Pensana confirms $494m capital cost for its Saltend, Longonjo operations |magazine=Mining Weekly |url=https://www.miningweekly.com/article/pensana-confirms-494m-capital-cost-for-its-saltend-longonjo-operations-2022-05-25 |archive-url=https://web.archive.org/web/20220712220855/https://www.miningweekly.com/article/pensana-confirms-494m-capital-cost-for-its-saltend-longonjo-operations-2022-05-25 |archive-date=12 July 2022 |url-status=live}}</ref> 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 tons of magnet metal rare earths.<ref>{{cite web |title=Pensana breaks ground at Saltend and secures ATF funding |date=22 July 2022 |website=Pensana PLC |url=https://pensana.co.uk/wp-content/uploads/2022/07/Pensana-Plc-RNS-Saltend-Ground-Breaking-22-July-2022-1.pdf |archive-url=https://web.archive.org/web/20220722105048/https://pensana.co.uk/wp-content/uploads/2022/07/Pensana-Plc-RNS-Saltend-Ground-Breaking-22-July-2022-1.pdf |archive-date=22 July 2022 |url-status=live}}</ref><ref>{{cite web |title=UK's first magnet refinery given huge financial boost as first ever strategy for supply of critical minerals published |date=22 July 2022 |url=https://www.gov.uk/government/news/uks-first-magnet-refinery-given-huge-financial-boost-as-first-ever-strategy-for-supply-of-critical-minerals-published |website=GOV.UK |language=en}}</ref>

Also under consideration for mining are sites such as [[Thor Lake]] in the [[Northwest Territories]], and various locations in [[Vietnam]].<ref name=Wikinvest/><ref name=Reuters/><ref name=Cbc2013-11-04>{{cite news
|url=http://www.cbc.ca/news/canada/north/federal-minister-approves-n-w-t-rare-earth-mine-1.2356245
|title=Federal minister approves N.W.T. rare earth mine
|quote=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".
|publisher=[[CBC News]]
|date=2013-11-04
|access-date=November 5, 2013
|archive-date=June 22, 2022
|archive-url=https://web.archive.org/web/20220622012302/https://www.cbc.ca/news/canada/north/federal-minister-approves-n-w-t-rare-earth-mine-1.2356245
|url-status=live
}}</ref> Additionally, in 2010, a large deposit of rare-earth minerals was discovered in [[Kvanefjeld]] in southern [[Greenland]].<ref>{{cite web |url=http://www.ggg.gl/Rare-Earth-Elements/Rare-Earth-Elements-at-Kvanefjeld.htm |title=Rare Earth Elements at Kvanefjeld |website=Greenland Minerals and Energy Ltd. |archive-url=https://web.archive.org/web/20100918165406/http://www.ggg.gl/Rare-Earth-Elements/Rare-Earth-Elements-at-Kvanefjeld.htm |archive-date=2010-09-18 |access-date=2010-11-10}}</ref> Pre-feasibility drilling at this site has confirmed significant quantities of black [[lujavrite]], which contains about 1% rare-earth oxides (REO).<ref>{{cite web |url=http://www.ggg.gl/Projects/New-Multi-Element-Targets-and-Overall-Resource-Potential.htm |title=New Multi-Element Targets and Overall Resource Potential |website=Greenland Minerals and Energy Ltd. |archive-url=https://web.archive.org/web/20101118075404/http://www.ggg.gl/Projects/New-Multi-Element-Targets-and-Overall-Resource-Potential.htm |archive-date=2010-11-18 |access-date=2010-11-10}}</ref> The [[European Union]] has urged Greenland to restrict Chinese development of rare-earth projects there, but as of early 2013, the [[government of Greenland]] has said that it has no plans to impose such restrictions.<ref>{{cite news |author=Carol Matlack |url=http://www.businessweek.com/articles/2013-02-10/chinese-workers-in-greenland |title=Chinese Workers—in Greenland? |date=February 10, 2013 |work=Business Week |access-date=March 9, 2013 |archive-date=February 13, 2013 |archive-url=https://web.archive.org/web/20130213141927/http://www.businessweek.com/articles/2013-02-10/chinese-workers-in-greenland }}</ref> 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.<ref>{{cite web |url=https://www.wsj.com/articles/SB10001424127887324077704578357792781721964 |title=Greenland Votes to Get Tough on Investors |first=Clemens |last=Bomsdorf |date=March 13, 2013 |work=The Wall Street Journal |access-date=10 February 2017 |archive-date=October 28, 2020 |archive-url=https://web.archive.org/web/20201028082449/https://www.wsj.com/articles/SB10001424127887324077704578357792781721964 |url-status=live}}</ref>

In central [[Spain]], [[Province of Ciudad Real|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.<ref>{{cite web |url=https://www.elmundo.es/cronica/2019/05/24/5ce58be121efa0e77f8b4651.html |title=Hay tierras raras aquí y están... en un lugar de La Mancha |date=2019-05-24 |website=ELMUNDO |language=es |access-date=2019-05-24 |archive-date=June 23, 2022 |archive-url=https://web.archive.org/web/20220623164720/https://www.elmundo.es/cronica/2019/05/24/5ce58be121efa0e77f8b4651.html |url-status=live}}</ref>

Adding to potential mine sites, [[Australian Securities Exchange|ASX]] listed Peak Resources announced in February 2012, that their Tanzanian-based [[Ngualla]] 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.<ref>{{cite web |url=http://www.asx.com.au/asxpdf/20120229/pdf/424pl5vn67q4h0.pdf |publisher=Peak Resources |title=Maiden Resource, Ngualla Rare Earth Project |website=ASX Release |date=February 29, 2012 |access-date=April 11, 2012 |archive-date=April 16, 2012 |archive-url=https://web.archive.org/web/20120416073235/http://www.asx.com.au/asxpdf/20120229/pdf/424pl5vn67q4h0.pdf |url-status=live}}</ref>

[[North Korea]] has been reported to have exported rare-earth ore to China, about US$1.88 million worth during May and June 2014.<ref name="Petrov">{{cite news |last1=Petrov |first1=Leonid |title=Rare earths bankroll North Korea's future |url=http://www.atimes.com/atimes/Korea/NH08Dg01.html |archive-url=https://web.archive.org/web/20120808102430/http://atimes.com/atimes/Korea/NH08Dg01.html |archive-date=August 8, 2012 |access-date=22 October 2018 |work=Asia Times |date=Aug 8, 2012}}</ref><ref>{{cite web |url=http://www.voakorea.com/a/north-korea-rare-earth/1966603.html |title=북한, 올 5~6월 희토류 중국 수출 크게 늘어 |date=July 28, 2014 |website=voakorea.com |language=ko |trans-title=North Korea Rare Earth exports to China increased significantly from May to June |access-date=February 10, 2017 |archive-date=March 30, 2019 |archive-url=https://web.archive.org/web/20190330104756/https://www.voakorea.com/a/north-korea-rare-earth/1966603.html |url-status=live}}</ref>

In May 2012, researchers from two universities in Japan announced that they had discovered rare earths in [[Ehime Prefecture]], Japan.<ref>{{cite web |title=Japan Discovers Domestic Rare Earths Reserve |url=http://www.brightwire.com/news/207869-japan-discovers-domestic-rare-earths-reserve |archive-url=https://archive.today/20120723024000/http://www.brightwire.com/news/207869-japan-discovers-domestic-rare-earths-reserve |archive-date=2012-07-23 |publisher=BrightWire}}</ref>

On 12 January 2023, Swedish state-owned mining company LKAB announced that it had discovered a deposit of over 1 million tonnes of rare earths in the country's [[Kiruna]] area, which would make it the largest such deposit in Europe.<ref>{{cite web |url=https://www.reuters.com/markets/commodities/swedens-lkab-finds-europes-biggest-deposit-rare-earth-metals-2023-01-12/ |title=Sweden's LKAB finds Europe's biggest deposit of rare-earth metals |work=Reuters |date=13 January 2023}}</ref>

China processes about 90% of the world's REEs and 60% of the world's [[lithium]]. As a result, the [[European Union]] imports practically all of its rare earth elements from China. The EU Critical Raw Materials Act of 2023 has set in action the required policy adjustments for Europe to start producing two-thirds of the lithium-ion batteries required for [[electric vehicle]]s and [[energy storage]].<ref name=":170"/><ref>{{Cite news |last1=Chee |first1=Foo Yun |last2=Blenkinsop |first2=Philip |last3=Chee |first3=Foo Yun |date=2023-11-13 |title=EU agrees mineral supply targets to cut reliance on China |language=en |work=Reuters |url=https://www.reuters.com/sustainability/eu-set-okay-rules-secure-critical-raw-materials-eu-official-says-2023-11-13/ |access-date=2023-11-30}}</ref><ref>{{Cite web|url=https://www.europarl.europa.eu/RegData/etudes/ATAG/2022/733586/EPRS_ATA(2022)733586_EN.pdf|title=Securing the EU's supply of critical raw materials}}</ref> In 2024, an EU backed lithium mining project created large scale [[2024 Serbian environmental protests|protests in Serbia]].<ref>{{cite news |last1=Ferreira Santos |first1=Sofia |title=Thousands protest against lithium mining in Serbia |url=https://www.bbc.com/news/articles/cged9qgwrvyo |access-date=13 August 2024 |agency=BBC |date=10 August 2024}}</ref>

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.<ref>{{Cite news |last=Maio |first=Pat |date=February 7, 2024 |title=Rare Earths Discovery Near Wheatland So Big It Could Be World Leader |url=https://cowboystatedaily.com/2024/02/07/rare-earths-discovery-near-wheatland-so-big-it-could-be-world-leader/ |access-date=2024-02-15 |newspaper=cowboystatedaily.com |language=en}}</ref>

In June 2024, Rare Earths Norway found a rare-earth oxide deposit of 8.8 million metric tons in [[Telemark]], 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.<ref>{{Cite web |last=Meredith |first=Sam |date=2024-06-11 |title=Norway discovers Europe's largest deposit of rare earth metals |url=https://www.cnbc.com/2024/06/11/norway-discovers-europes-largest-deposit-of-rare-earth-metals.html |access-date=2024-06-12 |website=CNBC |language=en}}</ref>

====Malaysian refining plans====
In early 2011, Australian mining company [[Lynas]] was reported to be "hurrying to finish" a US$230 million rare-earth refinery on the eastern coast of Peninsular Malaysia's industrial port of [[Kuantan]]. The plant would refine ore&nbsp;— lanthanides concentrate from the [[Mount Weld]] mine in Australia. The ore would be trucked to [[Fremantle]] and transported by [[container 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 counting [[China]].<ref>{{cite news |last=Bradsher |first=Keith |url=https://www.nytimes.com/2011/03/09/business/energy-environment/09rare.html?ref=science |title=Taking a Risk for Rare Earths |work=The New York Times |date=March 8, 2011 |others=(March 9, 2011 p. B1 NY ed.) |access-date=2011-03-09 |archive-date=June 15, 2022 |archive-url=https://web.archive.org/web/20220615115941/https://www.nytimes.com/2011/03/09/business/energy-environment/09rare.html?ref=science |url-status=live}}</ref> The Kuantan development brought renewed attention to the Malaysian town of [[Bukit Merah, Perak#District of Kinta, Central Perak|Bukit Merah]] in [[Perak]], where a rare-earth mine operated by a [[Mitsubishi Chemical Holdings|Mitsubishi Chemical]] subsidiary, Asian Rare Earth, closed in 1994 and left [[#Environmental considerations|continuing environmental and health concerns]].<ref>{{cite web |url=https://pengguna.org.my/index.php/pembangunan/alam-sekitar/768-kronologi-peristiwa-di-kilang-nadir-bumi-bukit-merah |title=Kronologi Peristiwa di Kilang Nadir Bumi, Bukit Merah |trans-title=Chronology of Events at the Rare Earth Factory, Red Hill |language=ms |publisher=Penang Consumer Association |access-date=26 August 2019 |archive-date=December 4, 2020 |archive-url=https://web.archive.org/web/20201204084605/https://pengguna.org.my/index.php/pembangunan/alam-sekitar/768-kronologi-peristiwa-di-kilang-nadir-bumi-bukit-merah }}</ref><ref name=NYT01>{{cite news |last=Bradsher |first=Keith |title=Mitsubishi Quietly Cleans Up Its Former Refinery |newspaper=The New York Times |date=8 March 2011 |others=(March 9, 2011 p. B4 NY ed.) |url=https://www.nytimes.com/2011/03/09/business/energy-environment/09rareside.html |access-date=2011-03-09 |url-status=live |archive-url=https://web.archive.org/web/20161229042639/http://www.nytimes.com/2011/03/09/business/energy-environment/09rareside.html |archive-date=December 29, 2016}}</ref> In mid-2011, after protests, Malaysian government restrictions on the Lynas plant were announced. At that time, citing subscription-only ''[[Dow Jones Newswire]]'' reports, a ''[[Barron's (newspaper)|Barrons]]'' report said the Lynas investment was $730 million, and the projected share of the global market it would fill put at "about a sixth."<ref name="B01">{{cite web |last=Coleman |first=Murray |url=http://blogs.barrons.com/focusonfunds/2011/06/30/rare-earth-metals-etf-soars-as-plans-to-break-chinas-hold-suffer-setback/ |title=Rare Earth ETF Jumps As Plans To Break China's Hold Suffer Setback |work=Barron's |date=June 30, 2011 |access-date=2011-06-30 |archive-url=https://web.archive.org/web/20110703100420/http://blogs.barrons.com/focusonfunds/2011/06/30/rare-earth-metals-etf-soars-as-plans-to-break-chinas-hold-suffer-setback/ |archive-date=2011-07-03}}</ref> An independent review initiated by the Malaysian Government, and conducted by the [[International Atomic Energy Agency]] (IAEA) in 2011 to address concerns of radioactive hazards, found no non-compliance with international radiation safety standards.<ref>{{cite conference |title=Report of the International Review Mission on the Radiation Safety Aspects of a Proposed Rare Earths Processing Facility (Lynas Project) |conference=(29 May – 3 June 2011) |url=http://www.iaea.org/newscenter/news/pdf/lynas-report2011.pdf |publisher=International Atomic Energy Agency |access-date=15 February 2018 |archive-date=12 November 2011 |date=2011 |archive-url=https://web.archive.org/web/20111112121737/http://www.iaea.org/newscenter/news/pdf/lynas-report2011.pdf}}</ref>

However, the Malaysian authorities confirmed that as of October 2011, Lynas was not given any permit to import any rare-earth ore into Malaysia. On February 2, 2012, the Malaysian AELB (Atomic Energy Licensing Board) recommended that Lynas be issued a temporary operating license subject to meeting a number of conditions. On 2 September 2014, Lynas was issued a 2-year full operating stage license by the AELB.<ref name="MI 20140902">{{cite news |last1=Ng |first1=Eileen |title=Lynas gets full operating licence before TOL expiry date |url=http://www.themalaysianinsider.com/malaysia/article/lynas-gets-full-operating-licence-before-tol-expiry-date |newspaper=The [[Malaysian Insider]] |access-date=3 September 2014 |date=2 September 2014 |archive-url=https://web.archive.org/web/20140904034335/http://www.themalaysianinsider.com/malaysia/article/lynas-gets-full-operating-licence-before-tol-expiry-date |archive-date=4 September 2014}}</ref>

On November 17 2024, [[Minister of Economy (Malaysia)|economy minister]] [[Rafizi Ramli]] said he hoped Malaysia is able to produce rare-earth elements within three years, through discussions with China to provide technology.<ref>{{Cite web |last=Reporters |first=F. M. T. |date=2024-11-17 |title=Govt targets domestic REE processing within 3 years |url=https://www.freemalaysiatoday.com/category/nation/2024/11/17/govt-targets-domestic-ree-processing-within-3-years/ |access-date=2024-11-18 |website=Free Malaysia Today {{!}} FMT |language=en}}</ref> In the past, plans to mine rare-earth elements at [[Kedah]] caused concerns of destroying forest reserves and harming water catchment areas.<ref>{{Cite web |last=Reporters |first=F. M. T. |date=2020-12-03 |title=Ministry pours cold water on Kedah’s rare earth mining plans |url=https://www.freemalaysiatoday.com/category/nation/2020/12/03/no-rare-earth-mining-without-technical-approvals-says-energy-and-natural-resources-ministry/ |access-date=2024-11-18 |website=Free Malaysia Today {{!}} FMT |language=en}}</ref><ref>{{Cite web |last=Rahman |first=Noorazura Abdul |date=2024-10-17 |title=NGO claims logging activities behind Kedah's worsening floods {{!}} New Straits Times |url=https://www.nst.com.my/news/nation/2024/10/1121241/ngo-claims-logging-activities-behind-kedahs-worsening-floods |access-date=2024-11-18 |website=NST Online |language=en}}</ref>

===Other sources===

====Mine tailings====
Significant quantities of rare-earth oxides are found in tailings accumulated from 50 years of [[uranium ore]], [[shale]], and [[loparite]] mining at [[Sillamäe]], [[Estonia]].<ref>{{cite book |title=Turning a Problem Into a Resource: Remediation and Waste Management at the Sillamäe Site, Estonia |last=Rofer |first=Cheryl K. |author2=Tõnis Kaasik |series=Volume 28 of NATO science series: Disarmament technologies |year=2000 |publisher=Springer |isbn=978-0-7923-6187-9 |page=229}}</ref> Due to the rising prices of rare earths, extraction of these oxides has become economically viable. The country currently exports around 3,000 tonnes per year, representing around 2% of world production.<ref>{{cite news |title=Estonia's rare earth break China's market grip |author=Anneli Reigas |newspaper=AFP |date=2010-11-30 |url=https://www.google.com/hostednews/afp/article/ALeqM5itXbI57zv-lwfcaFdBdh7UZXuVuA?docId=CNG.a00f68010092a06189a0276c763e93a4.141 |access-date=2010-12-01 |archive-date=May 13, 2012 |archive-url=https://web.archive.org/web/20120513001130/https://www.google.com/hostednews/afp/article/ALeqM5itXbI57zv-lwfcaFdBdh7UZXuVuA?docId=CNG.a00f68010092a06189a0276c763e93a4.141 |url-status=dead}}</ref> Similar resources are suspected in the western United States, where [[gold rush]]-era mines are believed to have discarded large amounts of rare earths, because they had no value at the time.<ref>{{cite news |title=Gold Rush Trash is Information Age Treasure |date=July 21, 2013 |url=https://www.usatoday.com/story/money/business/2013/07/21/gold-rush-era-discards-could-fuel-cellphones-tvs/2572761/ |work=USA Today |last=Cone |first=Tracie |access-date=July 21, 2013 |archive-date=June 15, 2022 |archive-url=https://web.archive.org/web/20220615124340/https://www.usatoday.com/story/money/business/2013/07/21/gold-rush-era-discards-could-fuel-cellphones-tvs/2572761/ |url-status=live}}</ref>

====Ocean mining====
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 {{convert|250|km|mi}} south of the island of [[Minami-Tori-Shima]].<ref>{{cite news |title=Seabed offers brighter hope in rare-earth hunt |url=http://asia.nikkei.com/Japan-Update/Seabed-offers-brighter-hope-in-rare-earth-hunt |access-date=11 December 2016 |work=Nikkei Asian Review |agency=Nikkei Inc. |date=25 November 2014 |archive-date=December 20, 2016 |archive-url=https://web.archive.org/web/20161220114144/http://asia.nikkei.com/Japan-Update/Seabed-offers-brighter-hope-in-rare-earth-hunt |url-status=live}}</ref> 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.<ref>{{cite web |title=Discovery of rare earths around Minami-Torishima |url=http://www.u-tokyo.ac.jp/en/utokyo-research/research-news/discovery-of-rare-earths-around-minami-torishima/ |website=UTokyo Research |publisher=University of Tokyo |access-date=11 December 2016 |date=2 May 2013 |archive-date=June 20, 2018 |archive-url=https://web.archive.org/web/20180620002602/https://www.u-tokyo.ac.jp/en/utokyo-research/research-news/discovery-of-rare-earths-around-minami-torishima/ |url-status=live}}</ref><ref>{{cite conference |last1=Zhi Li |first1=Ling |last2=Yang |first2=Xiaosheng |title=China's rare earth ore deposits and beneficiation techniques |url=http://www.eurare.eu/docs/eres2014/firstSession/XiaoshengYang.pdf |conference=1st European Rare Earth Resources Conference |publisher=European Commission for the 'Development of a sustainable exploitation scheme for Europe's Rare Earth ore deposits' |place=Milos, Greece |access-date=11 December 2016 |date=4 September 2014 |archive-date=January 19, 2020 |archive-url=https://web.archive.org/web/20200119193604/http://www.eurare.eu/docs/eres2014/firstSession/XiaoshengYang.pdf |url-status=live}}</ref>

====Waste and recycling====
Another recently developed source of rare earths is [[electronic waste]] and other [[waste]]s that have significant rare-earth components.<ref>{{cite book |last1=Um |first1=Namil |title=Hydrometallurgical recovery process of rare-earth elements from waste: main application of acid leaching with devised diagram |date=July 2017 |publisher=INTECH |isbn=978-953-51-3401-5 |pages=41–60}}</ref> Advances in [[recycling|recycling technology]] have made the extraction of rare earths from these materials less expensive.<ref>{{cite web |url=http://www.recyclinginternational.com/recycling-news/6976/research-and-legislation/belgium/new-liquid-extraction-frontier-rare-earths |date=March 26, 2013 |title=New liquid extraction frontier for rare earths? |publisher=Recycling International |access-date=10 February 2017 |archive-date=July 29, 2017 |archive-url=https://web.archive.org/web/20170729112611/http://www.recyclinginternational.com/recycling-news/6976/research-and-legislation/belgium/new-liquid-extraction-frontier-rare-earths }}</ref> Recycling plants operate in Japan, where an estimated 300,000 tons of rare earths are found in unused electronics.<ref>{{cite news |last=Tabuchi |first=Hiroko |author-link=Hiroko Tabuchi |url=https://www.nytimes.com/2010/10/05/business/global/05recycle.html |title=Japan Recycles Minerals From Used Electronics |work=[[New York Times]] |date=October 5, 2010 |access-date=February 25, 2017 |archive-date=June 22, 2022 |archive-url=https://web.archive.org/web/20220622084534/https://www.nytimes.com/2010/10/05/business/global/05recycle.html |url-status=live}}</ref> In [[France]], the [[Rhodia (company)|Rhodia]] group is setting up two factories, in [[La Rochelle]] and [[Saint-Fons]], that will produce 200 tons of rare earths a year from used [[fluorescent lamp]]s, magnets, and batteries.<ref>{{cite web |url=http://www.rhodia.com/en/news_center/news_releases/Recycle_rare_earths_031011.tcm |title=Rhodia to recycle rare earths from magnets |website=Solvay — Rhodia |date=October 3, 2011 |archive-url=https://web.archive.org/web/20140421050640/http://www.rhodia.com/en/news_center/news_releases/Recycle_rare_earths_031011.tcm |archive-date=2014-04-21}}</ref><ref>{{cite web |url=http://www.recyclinginternational.com/recycling-news/3948/e-waste-and-batteries/france/rhodia-expands-rare-earth-recycling-reach |date=October 11, 2011 |title=Rhodia expands rare earth recycling reach |publisher=Recycling International |access-date=10 February 2017 |archive-date=July 29, 2017 |archive-url=https://web.archive.org/web/20170729112600/http://www.recyclinginternational.com/recycling-news/3948/e-waste-and-batteries/france/rhodia-expands-rare-earth-recycling-reach |url-status=live}}</ref> [[Coal]]<ref>Sorokin, Anatoliy P., et al. "Distribution of Rare Earth and Selected Trace Elements in Combustion Products of Yerkovetskoe Brown Coal Deposit (Amur Region, Russia)." ''Energy Exploration & Exploitation'', vol. 37, no. 6, 2019, pp. 1721–36. JSTOR, https://www.jstor.org/stable/26785615. Retrieved 13 Dec. 2023.</ref> and coal by-products, such as [[Coal combustion products|ash]] 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.<ref>{{cite journal |author1=Wencai Zhang |author2=Mohammad Rezaee |author3=Abhijit Bhagavatula |author4=Yonggai Li |author5=John Groppo |author6=Rick Honaker |s2cid=128509001 |journal=International Journal of Coal Preparation and Utilization |doi=10.1080/19392699.2015.1033097 |volume=35 |year=2015 |issue=6 |pages=295–330 |title=A Review of the Occurrence and Promising Recovery Methods of Rare Earth Elements from Coal and Coal By-Products|bibcode=2015IJCPU..35..295Z }}</ref>

===Methods===
One study mixed [[fly ash]] with carbon black and then sent a 1-second current pulse through the mixture, heating it to {{Convert|3000|C}}. The fly ash contains microscopic bits of glass that encapsulate the metals. The heat shatters the glass, exposing the rare earths. Flash heating also converts [[phosphate]]s 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.<ref>{{cite web |last=Kean |first=Sam |date=February 9, 2022 |title=An electric jolt salvages valuable metals from waste |url=https://www.science.org/content/article/electric-jolt-salvages-valuable-metals-waste |access-date=2022-02-15 |website=www.science.org |language=en}}</ref>

==Properties==
According to chemistry professor [[Andrea Sella]], 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.<ref name="ASella2016">Professor of Chemistry at [[University College London]], [[Andrea Sella]], {{YouTube|UvQMiqqzcZE |Andrea Sella: "Insight: Rare-earth metals"}}, Interview on [[TRT World]] / Oct 2016, minutes 4:40 - ff.</ref> For example, "the rare-earth elements [[praseodymium]] (Pr) and [[neodymium]] (Nd) can both be embedded inside glass and they completely cut out the glare from the flame when one is doing [[glass-blowing]]."<ref name="ASella2016"/>

==Uses==
{{Pie chart
| thumb=right
| caption=Global REE consumption, 2015<ref name=zhou2015>{{cite journal |last1=Zhou |first1=Baolu |last2=Li |first2=Zhongxue |last3=Chen |first3=Congcong |title=Global Potential of Rare Earth Resources and Rare Earth Demand from Clean Technologies |journal=Minerals |date=25 October 2017 |volume=7 |issue=11 |page=203 |doi=10.3390/min7110203 |bibcode=2017Mine....7..203Z |quote=See production in Figure 1 on page 2 |doi-access=free}}</ref>
| other=
| label1=[[catalysis|Catalyst]]s, 24%
| value1=24
| color1=red
| label2=Magnets, 23%
| value2=23
| color2=aqua
| label3=Polishing, 12%
| value3=12
| color3=pink
| label4="other", 9%
| value4=9
| color4=fuchsia
| label5=Metallurgy, 8%
| value5=8
| color5=blue
| label6=Batteries, 8%
| value6=8
| color6=green
| label7=Glass, 7%
| value7=7
| color7=yellow
| label8=Ceramics, 6%
| value8=6
| color8=brown
| label9=Phosphors and pigments, 3%
| value9=3
| color9=turquoise
}}

{{Pie chart
| thumb=right
| caption=US consumption of REE, 2018<ref name=USGS2019>{{cite book |doi=10.3133/70202434 |page=132 |chapter-url=https://www.usgs.gov/centers/nmic/mineral-commodity-summaries |chapter=Mineral Commodity Summaries 2019 |title=Mineral Commodity Summaries |year=2019 |s2cid=239335855 |access-date=June 26, 2019 |archive-date=June 29, 2018 |archive-url=https://web.archive.org/web/20180629183108/https://minerals.usgs.gov/minerals/pubs/mcs/ |url-status=live}} <!-- Public domain --></ref>
| other=
| label1=Catalysts, 60%
| value1=60
| color1=red
| label2=Ceramics and glass, 15%
| value2=15
| color2=yellow
| label3=Polishing, 10%
| value3=10
| color3=pink
| label4="other", 5%
| value4=5
| color4=fuchsia
| label5=Metallurgy, 10%
| value5=10
| color5=blue
}}
The uses, applications, and demand for rare-earth elements have expanded over the years. Globally, most REEs are used for [[catalysis|catalyst]]s and magnets.<ref name=zhou2015/> In the US, more than half of REEs are used for catalysts; ceramics, glass, and polishing are also main uses.<ref name=USGS2019/>

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 for [[petroleum refining]] and as [[Diesel exhaust fluid|diesel additive]]s. Nd is important in magnet production in traditional and low-carbon technologies. Rare-earth elements in this category are used in the electric motors of [[hybrid vehicle|hybrid]] and [[electric vehicle]]s, generators in some [[wind turbine]]s, hard disc drives, portable electronics, microphones, and speakers.{{Citation needed|date=June 2022}}

Ce, La, and Nd are important in alloy making, and in the production of [[fuel cell]]s and [[nickel–metal hydride battery|nickel-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,<ref>[[F. J. Duarte]] (Ed.), ''Tunable Lasers Handbook'' (Academic, New York, 1995).</ref> and in medical imaging. Additional uses for rare-earth elements are as tracers in medical applications, fertilizers, and in water treatment.<ref name=gsl/>

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.<ref name=Pang>{{cite journal |last1=Pang |first1=Xin |last2=Li |first2=Decheng |last3=Peng |first3=An |s2cid=11359274 |date=2002-03-01 |title=Application of rare-earth elements in the agriculture of China and its environmental behavior in soil |journal=Environmental Science and Pollution Research |language=en |volume=9 |issue=2 |pages=143–8 |doi=10.1007/BF02987462 |pmid=12008295 |bibcode=2002ESPR....9..143P |issn=0944-1344 |url=http://ir.rcees.ac.cn/handle/311016/23951 |access-date=July 29, 2019 |archive-date=June 23, 2022 |archive-url=https://web.archive.org/web/20220623071752/https://ir.rcees.ac.cn/handle/311016/23951 |url-status=live}}<!--http://ir.rcees.ac.cn/handle/311016/23951--></ref> In addition, 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. However, this practice has resulted in REE bioaccumulation within livestock and has impacted vegetation and algae growth in these agricultural areas.<ref name=Kyung/> Additionally 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.<ref name=Pang/><ref name="Ali 123–134"/>

==Environmental considerations==
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.<ref name=rizk>{{cite web |title=What colour is the cloud? |first1=Shirley |last1=Rizk |date=21 June 2019 |url=https://www.eib.org/en/stories/digital-footprint |access-date=2020-09-17 |website=European Investment Bank |language=en |archive-date=April 14, 2021 |archive-url=https://web.archive.org/web/20210414035732/https://www.eib.org/en/stories/digital-footprint |url-status=live}}</ref><ref name=standaert>{{cite web |title=China Wrestles with the Toxic Aftermath of Rare Earth Mining |url=https://e360.yale.edu/features/china-wrestles-with-the-toxic-aftermath-of-rare-earth-mining |first1=Michael |last1=Standaert |date=2 July 2019 |access-date=16 June 2021 |publisher=Yale School of the Environment |work=Yale Environment 360 |archive-date=July 9, 2022 |archive-url=https://web.archive.org/web/20220709042527/https://e360.yale.edu/features/china-wrestles-with-the-toxic-aftermath-of-rare-earth-mining |url-status=live}}</ref> Generally, it is estimated that extracting 1 tonne of rare earth element creates around 2,000 tonnes of waste, partly toxic, including 1 ton of radioactive waste. The largest mining site of REEs, [[Bayan Obo Mining District|Bayan Obo]] in China produced more than 70,000 tons of radioactive waste, that contaminated ground water.<ref>{{cite web |last1=CHO |first1=RENEE |title=The Energy Transition Will Need More Rare Earth Elements. Can We Secure Them Sustainably? |url=https://news.climate.columbia.edu/2023/04/05/the-energy-transition-will-need-more-rare-earth-elements-can-we-secure-them-sustainably/ |website=State of the planet |date=April 5, 2023 |publisher=Columbia Climate School |access-date=27 September 2023}}</ref>

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. The mining of REEs, use of REE-enriched fertilizers, and the production of phosphorus fertilizers all contribute to REE contamination.<ref name="Volokh">{{cite journal |date=1990-06-01 |title=Phosphorus fertilizer production as a source of rare-earth elements pollution of the environment |journal=Science of the Total Environment |language=en |volume=95 |pages=141–148 |doi=10.1016/0048-9697(90)90059-4 |pmid=2169646 |issn=0048-9697 |bibcode=1990ScTEn..95..141V |last1=Volokh |first1=A. A. |last2=Gorbunov |first2=A. V. |last3=Gundorina |first3=S. F. |last4=Revich |first4=B. A. |last5=Frontasyeva |first5=M. V. |author6=Chen Sen Pal}}</ref> Furthermore, 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 is [[cerium(IV) oxide|cerium oxide]] ({{chem|Ce|O|2}}), which is produced during the combustion of diesel and released as exhaust, contributing heavily to soil and water contamination.<ref name="Kyung">{{cite journal |last=Rim |first=Kyung-Taek |s2cid=17407586 |date=2016-09-01 |title=Effects of rare earth elements on the environment and human health: A literature review |journal=Toxicology and Environmental Health Sciences |language=en |volume=8 |issue=3 |pages=189–200 |doi=10.1007/s13530-016-0276-y |bibcode=2016TxEHS...8..189R |issn=2005-9752}}</ref>

[[File:Baiyunebo ast 2006181.jpg|thumb|False-color satellite image of the [[Bayan Obo Mining District]], 2006]]
Mining, refining, and recycling of rare earths have serious environmental consequences if not properly managed. Low-level radioactive [[tailings]] resulting from the occurrence of [[thorium]] and [[uranium]] in rare-earth ores present a potential hazard<ref>Bourzac, Katherine. [http://www.technologyreview.com/energy/26655/?p1=MstCom "Can the US Rare-Earth Industry Rebound?"] {{Webarchive|url=https://web.archive.org/web/20120514220351/http://www.technologyreview.com/energy/26655/?p1=MstCom |date=May 14, 2012}} ''Technology Review''. October 29, 2010.</ref><ref>{{Cite web |date=2015-03-20 |title=Thorium - Cancer-Causing Substances - NCI |url=https://www.cancer.gov/about-cancer/causes-prevention/risk/substances/thorium |access-date=2024-02-14 |website=www.cancer.gov |language=en}}</ref> 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,<ref>{{cite web |url=http://www.chinamining.org/News/2010-05-21/1274404411d36358.html |title=Govt cracks whip on rare earth mining |publisher=China Mining Association |date=May 21, 2010 |access-date=June 3, 2010 |archive-url=https://web.archive.org/web/20110725170447/http://www.chinamining.org/News/2010-05-21/1274404411d36358.html |archive-date=2011-07-25}}</ref> where mines&nbsp;– commonly small, rural, and illegal operations&nbsp;– are particularly prone to releasing toxic waste into the general water supply.<ref name=Wikinvest/><ref>{{cite web |author=Lee Yong-tim |url=http://www.rfa.org/english/news/china_pollution-20080222.html |title=South China Villagers Slam Pollution From Rare Earth Mine |date=22 February 2008 |website=Radio Free Asia |access-date=16 March 2008 |archive-date=April 20, 2022 |archive-url=https://web.archive.org/web/20220420055708/https://www.rfa.org/english/news/china_pollution-20080222.html |url-status=live}}</ref> However, even the major operation in [[Baotou]], in Inner Mongolia, where much of the world's rare-earth supply is refined, has caused major environmental damage.<ref name="NYT">{{cite news |title=After China's Rare Earth Embargo, a New Calculus |author=Bradsher, Keith |newspaper=The New York Times |date=October 29, 2010 |url=https://www.nytimes.com/2010/10/30/business/global/30rare.html |access-date=October 30, 2010 |author-link=Keith Bradsher |archive-date=June 25, 2022 |archive-url=https://web.archive.org/web/20220625155338/https://www.nytimes.com/2010/10/30/business/global/30rare.html |url-status=live}}</ref> China's Ministry of Industry and Information Technology estimated that cleanup costs in Jiangxi province at $5.5 billion.<ref name=standaert/>

It is, however, possible to filter out and recover any rare-earth elements that flow out with the wastewater from mining facilities. However, such filtering and recovery equipment may not always be present on the outlets carrying the wastewater.<ref>{{cite journal |last1=Pereao |first1=Omoniyi |last2=Bode-Aluko |first2=Chris |last3=Fatoba |first3=Olanrewaju |last4=Laatikaine |first4=Katri |last5=Petrik |first5=Leslie |title=Rare earth elements removal techniques from water/wastewater: a review |journal=Desalination and Water Treatment |date=2018 |volume=130 |pages=71–86 |doi=10.5004/dwt.2018.22844 |bibcode=2018DWatT.130...71P |url=https://www.researchgate.net/publication/328637201 |issn=1944-3994}}</ref><ref>{{cite journal |title=Recovery of Rare Earth Elements from Wastewater Towards a Circular Economy |first1=Óscar |last1=Barros |first2=Lara |last2=Costa |first3=Filomena |last3=Costa |first4=Ana |last4=Lago |first5=Verónica |last5=Rocha |first6=Ziva |last6=Vipotnik |first7=Bruna |last7=Silva |first8=Teresa |last8=Tavares |date=March 13, 2019 |journal=Molecules |volume=24 |issue=6 |page=1005 |doi=10.3390/molecules24061005 |pmid=30871164 |pmc=6471397 |doi-access=free}}</ref><ref>{{cite web |url=https://lirias.kuleuven.be/retrieve/325732 |title=Towards zero-waste valorization of rare earth elements |access-date=June 7, 2021 |archive-date=June 7, 2021 |archive-url=https://web.archive.org/web/20210607160620/https://lirias.kuleuven.be/retrieve/325732 |url-status=live}}</ref>

===Recycling and reusing REEs===
{{Further|Circular economy|Renewable energy#Conservation areas, recycling and rare-earth elements}}

The rare-earth elements (REEs) are vital to modern technologies and society and are amongst the most critical elements. Despite this, typically only around 1% of REEs are recycled from end-products.<ref>{{Cite journal |last1=Jowitt |first1=Simon M. |last2=Werner |first2=Timothy T. |last3=Weng |first3=Zhehan |last4=Mudd |first4=Gavin M. |date=2018-10-01 |title=Recycling of the rare earth elements |url=https://www.sciencedirect.com/science/article/pii/S2452223617301256 |journal=Current Opinion in Green and Sustainable Chemistry |series=Reuse and Recycling / UN SGDs: How can Sustainable Chemistry Contribute? / Green Chemistry in Education |language=en |volume=13 |pages=1–7 |doi=10.1016/j.cogsc.2018.02.008 |bibcode=2018COGSC..13....1J |s2cid=135249554 |issn=2452-2236}}</ref> 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.<ref name="Balaram2019">{{Cite journal |last=Balaram |first=V. |date=2019-07-01 |title=Rare earth elements: A review of applications, occurrence, exploration, analysis, recycling, and environmental impact |journal=Geoscience Frontiers |language=en |volume=10 |issue=4 |pages=1285–1303 |doi=10.1016/j.gsf.2018.12.005 |bibcode=2019GeoFr..10.1285B |issn=1674-9871|doi-access=free }}</ref> For example, recovery of  neodymium requires manual disassembly of hard disk drives because shredding the drives only recovers 10% of the REE.<ref>{{Cite journal |last1=Sprecher |first1=Benjamin |last2=Xiao |first2=Yanping |last3=Walton |first3=Allan |last4=Speight |first4=John |last5=Harris |first5=Rex |last6=Kleijn |first6=Rene |last7=Visser |first7=Geert |last8=Kramer |first8=Gert Jan |date=2014-04-01 |title=Life Cycle Inventory of the Production of Rare Earths and the Subsequent Production of NdFeB Rare Earth Permanent Magnets |url=https://pubs.acs.org/doi/10.1021/es404596q |journal=Environmental Science & Technology |language=en |volume=48 |issue=7 |pages=3951–3958 |doi=10.1021/es404596q |pmid=24576005 |bibcode=2014EnST...48.3951S |issn=0013-936X}}</ref>

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.<ref name="Ali 123–134">{{cite journal |last=Ali |first=Saleem H. |date=2014-02-13 |title=Social and Environmental Impact of the Rare Earth Industries |journal=Resources |language=en |volume=3 |issue=1 |pages=123–134 |doi=10.3390/resources3010123 |doi-access=free}}</ref> A study published in 2014 suggests a method to recycle REEs from waste nickel-metal hydride batteries, demonstrating a recovery rate of 95.16%.<ref>{{cite journal |last1=Yang |first1=Xiuli |last2=Zhang |first2=Junwei |last3=Fang |first3=Xihui |date=2014-08-30 |title=Rare earth element recycling from waste nickel-metal hydride batteries |journal=Journal of Hazardous Materials |language=en |volume=279 |pages=384–388 |doi=10.1016/j.jhazmat.2014.07.027 |issn=0304-3894 |pmid=25089667|bibcode=2014JHzM..279..384Y }}</ref> 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.<ref>{{cite news |title=Rare earth elements for smartphones can be extracted from coal waste |work=New Scientist |url=https://www.newscientist.com/article/2307608-rare-earth-elements-for-smartphones-can-be-extracted-from-coal-waste/}}</ref><ref>{{cite journal |last1=Deng |first1=Bing |last2=Wang |first2=Xin |last3=Luong |first3=Duy Xuan |last4=Carter |first4=Robert A. |last5=Wang |first5=Zhe |last6=Tomson |first6=Mason B. |last7=Tour |first7=James M. |year=2022 |title=Rare earth elements from waste |journal=Science Advances |volume=8 |issue=6 |pages=eabm3132 |bibcode=2022SciA....8M3132D |doi=10.1126/sciadv.abm3132 |pmc=8827657 |pmid=35138886}}</ref> A study suggests that "fulfillment of the circular economy approach could reduce up to 200 times the impact [[Climate change mitigation|in the climate change category]] and up to 70 times the cost due to the REE mining."<ref>{{cite journal |last1=Amato |first1=A. |last2=Becci |first2=A. |last3=Birloaga |first3=I. |last4=De Michelis |first4=I. |last5=Ferella |first5=F. |last6=Innocenzi |first6=V. |last7=Ippolito |first7=N. M. |last8=Pillar Jimenez Gomez |first8=C. |last9=Vegliò |first9=F. |last10=Beolchini |first10=F. |date=1 May 2019 |title=Sustainability analysis of innovative technologies for the rare earth elements recovery |journal=Renewable and Sustainable Energy Reviews |language=en |volume=106 |pages=41–53 |doi=10.1016/j.rser.2019.02.029 |bibcode=2019RSERv.106...41A |issn=1364-0321 |s2cid=115810707 |hdl-access=free |hdl=11566/264482}}</ref> In most of the reported studies reviewed by a [[scientific review]], "secondary waste is subjected to chemical and or bioleaching followed by solvent extraction processes for clean separation of REEs."<ref>{{cite journal |last1=Jyothi |first1=Rajesh Kumar |last2=Thenepalli |first2=Thriveni |last3=Ahn |first3=Ji Whan |last4=Parhi |first4=Pankaj Kumar |last5=Chung |first5=Kyeong Woo |last6=Lee |first6=Jin-Young |date=10 September 2020 |title=Review of rare earth elements recovery from secondary resources for clean energy technologies: Grand opportunities to create wealth from waste |journal=Journal of Cleaner Production |language=en |volume=267 |page=122048 |doi=10.1016/j.jclepro.2020.122048 |bibcode=2020JCPro.26722048J |issn=0959-6526 |s2cid=219469381}}</ref>

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,<ref>{{Cite journal |last1=Borst |first1=Anouk M. |last2=Smith |first2=Martin P. |last3=Finch |first3=Adrian A. |last4=Estrade |first4=Guillaume |last5=Villanova-de-Benavent |first5=Cristina |last6=Nason |first6=Peter |last7=Marquis |first7=Eva |last8=Horsburgh |first8=Nicola J. |last9=Goodenough |first9=Kathryn M. |last10=Xu |first10=Cheng |last11=Kynický |first11=Jindřich |last12=Geraki |first12=Kalotina |date=2020-09-01 |title=Adsorption of rare earth elements in regolith-hosted clay deposits |journal=Nature Communications |language=en |volume=11 |issue=1 |page=4386 |doi=10.1038/s41467-020-17801-5 |issn=2041-1723 |pmc=7463018 |pmid=32873784|bibcode=2020NatCo..11.4386B }}</ref> ocean bed sediments, coal fly ash,<ref>{{Cite journal |last1=Liu |first1=Pan |last2=Huang |first2=Rixiang |last3=Tang |first3=Yuanzhi |date=2019-05-07 |title=Comprehensive Understandings of Rare Earth Element (REE) Speciation in Coal Fly Ashes and Implication for REE Extractability |url=https://pubs.acs.org/doi/10.1021/acs.est.9b00005 |journal=Environmental Science & Technology |language=en |volume=53 |issue=9 |pages=5369–5377 |doi=10.1021/acs.est.9b00005 |pmid=30912650 |bibcode=2019EnST...53.5369L |s2cid=85517653 |issn=0013-936X}}</ref> 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.<ref>{{Cite journal |last1=Liu |first1=Pan |last2=Zhao |first2=Simin |last3=Xie |first3=Nan |last4=Yang |first4=Lufeng |last5=Wang |first5=Qian |last6=Wen |first6=Yinghao |last7=Chen |first7=Hailong |last8=Tang |first8=Yuanzhi |date=2023-04-04 |title=Green Approach for Rare Earth Element (REE) Recovery from Coal Fly Ash |journal=Environmental Science & Technology |language=en |volume=57 |issue=13 |pages=5414–5423 |doi=10.1021/acs.est.2c09273 |issn=0013-936X |pmc=10077585 |pmid=36942728|bibcode=2023EnST...57.5414L }}</ref> 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|date=July 2023}}. According to a 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.<ref name="Balaram2019"/>

===Impact of REE contamination===
====On vegetation====
The mining of REEs has caused the [[soil contamination|contamination]] of soil and water around production areas, which has impacted vegetation in these areas by decreasing [[chlorophyll]] production, which affects photosynthesis and inhibits the growth of the plants.<ref name=Kyung/> 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.<ref name="sciencedirect.com">{{cite journal |last=Chua |first=H |date=18 June 1998 |title=Bio-accumulation of environmental residues of rare earth elements in aquatic flora ''Eichhornia crassipes'' (Mart.) Solms in Guangdong Province of China |journal=Science of the Total Environment |language=en |volume=214 |issue=1–3 |pages=79–85 |doi=10.1016/S0048-9697(98)00055-2 |issn=0048-9697 |bibcode=1998ScTEn.214...79C}}</ref> 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.<ref name=Volokh/> Furthermore, 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 the [[Eichhornia crassipes|water 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 with [[cerium]] and resulted in the water hyacinth becoming three times more concentrated in cerium than its surrounding water.<ref name="sciencedirect.com"/>

====On human health====
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.<ref name=HiranoSuzuki1996>{{Cite journal |last1=Hirano |first1=S |last2=Suzuki |first2=K T |date=March 1996 |title=Exposure, metabolism, and toxicity of rare earths and related compounds. |journal=Environmental Health Perspectives |language=en |volume=104 |issue=suppl 1 |pages=85–95 |doi=10.1289/ehp.96104s185 |issn=0091-6765 |pmc=1469566 |pmid=8722113}}</ref> Long term (18 months) inhalation of dust containing high levels (60%) of REEs has been shown to cause [[pneumoconiosis]] but the mechanism is unknown.<ref name=HiranoSuzuki1996/>

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.<ref name=Rim>{{cite journal |last1=Rim |first1=Kyung Taek |last2=Koo |first2=Kwon Ho |last3=Park |first3=Jung Sun |title=Toxicological Evaluations of Rare Earths and Their Health Impacts to Workers: A Literature Review |journal=Safety and Health at Work |volume=4 |issue=1 |pages=12–26 |doi=10.5491/shaw.2013.4.1.12 |pmid=23516020 |year=2013 |pmc=3601293}}</ref> One side effect of mining REEs can be exposure to harmful radioactive [[Thorium]] as has been demonstrated at large mine in Batou (Mongolia).<ref>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.</ref> 
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.<ref>{{cite journal |last1=Zhong |first1=Buqing |last2=Wang |first2=Lingqing |last3=Liang |first3=Tao |last4=Xing |first4=Baoshan |date=October 2017 |title=Pollution level and inhalation exposure of ambient aerosol fluoride as affected by polymetallic rare earth mining and smelting in Baotou, north China |journal=Atmospheric Environment |language=en |volume=167 |pages=40–48 |doi=10.1016/j.atmosenv.2017.08.014 |bibcode=2017AtmEn.167...40Z}}</ref>

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 possible [[bioaccumulation]] 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.<ref>{{cite journal |date=2013-10-01 |title=A human health risk assessment of rare earth elements in soil and vegetables from a mining area in Fujian Province, Southeast China |journal=Chemosphere |language=en |volume=93 |issue=6 |pages=1240–1246 |doi=10.1016/j.chemosphere.2013.06.085 |pmid=23891580 |issn=0045-6535 |bibcode=2013Chmsp..93.1240L |last1=Li |first1=Xiaofei |last2=Chen |first2=Zhibiao |last3=Chen |first3=Zhiqiang |last4=Zhang |first4=Yonghe |doi-access=free}}</ref> 
Analysis of REEs in street dust in China suggest "no augmented health hazard".<ref name=sun>{{cite journal |last1=Sun |first1=Guangyi |last2=Li |first2=Zhonggen |last3=Liu |first3=Ting |last4=Chen |first4=Ji |last5=Wu |first5=Tingting |last6=Feng |first6=Xinbin |s2cid=31655372 |date=2017-12-01 |title=Rare earth elements in street dust and associated health risk in a municipal industrial base of central China |journal=Environmental Geochemistry and Health |language=en |volume=39 |issue=6 |pages=1469–1486 |doi=10.1007/s10653-017-9982-x |pmid=28550599 |bibcode=2017EnvGH..39.1469S |issn=0269-4042 |url=http://ir.ihb.ac.cn/handle/342005/30223 |access-date=September 6, 2019 |archive-date=February 25, 2021 |archive-url=https://web.archive.org/web/20210225013613/http://ir.ihb.ac.cn/handle/342005/30223 }}</ref>
Similarly, analysis of cereal crops in mining areas in China found levels too low for health risks.<ref>{{cite journal |last1=Zhuang |first1=Maoqiang |last2=Wang |first2=Liansen |last3=Wu |first3=Guangjian |last4=Wang |first4=Kebo |last5=Jiang |first5=Xiaofeng |last6=Liu |first6=Taibin |last7=Xiao |first7=Peirui |last8=Yu |first8=Lianlong |last9=Jiang |first9=Ying |date=2017-08-29 |title=Health risk assessment of rare earth elements in cereals from mining area in Shandong, China |journal=Scientific Reports |language=En |volume=7 |issue=1 |page=9772 |doi=10.1038/s41598-017-10256-7 |pmid=28852170 |pmc=5575011 |issn=2045-2322 |bibcode=2017NatSR...7.9772Z}}</ref>

====On animal health====
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.<ref name=Pagano>{{cite journal |last1=Pagano |first1=Giovanni |last2=Aliberti |first2=Francesco |last3=Guida |first3=Marco |last4=Oral |first4=Rahime |last5=Siciliano |first5=Antonietta |last6=Trifuoggi |first6=Marco |last7=Tommasi |first7=Franca |title=Rare earth elements in human and animal health: State of art and research priorities |journal=Environmental Research |volume=142 |pages=215–220 |doi=10.1016/j.envres.2015.06.039 |pmid=26164116 |bibcode=2015ER....142..215P |year=2015 |hdl=11586/148470 |hdl-access=free}}</ref> REEs have been added to feed in livestock to increase their body mass and increase milk production.<ref name=Pagano/> 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.<ref name=Pagano/> 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.<ref name=Pagano/> 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. Furthermore, in some cases, animals that live in REE-contaminated areas have been diagnosed with organ or system problems.<ref name=Kyung/> REEs have been used in freshwater fish farming because it protects the fish from possible diseases.<ref name=Pagano/> 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.<ref>{{cite thesis |url=https://edoc.ub.uni-muenchen.de/5936/ |title=Rare Earth Elements in Agriculture with Emphasis on Animal Husbandry |last=Redling |first=Kerstin |date=2006 |type=Dissertation |location=LMU München |publisher=Faculty of Veterinary Medicine |access-date=2018-04-05 |archive-date=June 15, 2022 |archive-url=https://web.archive.org/web/20220615124341/https://edoc.ub.uni-muenchen.de/5936/ |url-status=live}}</ref>

===Remediation after pollution===
{{Update section|date=May 2019}}
After the [[1982 Bukit Merah radioactive pollution]], the mine in [[Malaysia]] 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."<ref name=NYT01/>

In May 2011, after the [[Fukushima nuclear disaster]], widespread protests took place in Kuantan over the [[#Production|Lynas 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."<ref name=Bl01>Lee, Yoolim, [https://www.bloomberg.com/news/2011-05-31/malaysia-rare-earths-in-largest-would-be-refinery-incite-protest.html "Malaysia Rare Earths in Largest Would-Be Refinery Incite Protest"] {{Webarchive|url=https://web.archive.org/web/20140911001724/http://www.bloomberg.com/news/2011-05-31/malaysia-rare-earths-in-largest-would-be-refinery-incite-protest.html |date=September 11, 2014}}, ''[[Bloomberg L.P.|Bloomberg Markets Magazine]]'', May 31, 2011 5:00 PM ET.</ref> Construction of the facility has been halted until an independent [[United Nations]] [[IAEA]] panel investigation is completed, which is expected by the end of June 2011.<ref>[https://www.bbc.co.uk/news/world-asia-pacific-13593213 "UN investigation into Malaysia rare-earth plant safety"] {{Webarchive|url=https://web.archive.org/web/20220622010100/https://www.bbc.co.uk/news/world-asia-pacific-13593213 |date=June 22, 2022}}, [[BBC]], 30 May 2011 05:52 ET.</ref> [[#Production|New restrictions]] were announced by the Malaysian government in late June.<ref name=B01/>

An [[IAEA]] 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.<ref>[http://www.iaea.org/newscenter/news/2011/malaysiamissionreport.html IAEA Submits Lynas Report to Malaysian Government] {{Webarchive|url=https://web.archive.org/web/20121007140824/http://www.iaea.org/newscenter/news/2011/malaysiamissionreport.html |date=October 7, 2012}}. Iaea.org (2011-06-29). Retrieved on 2011-09-27.</ref>

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.<ref>{{cite magazine |magazine=High Country News |title=Why rare-earth mining in the West is a bust |url=http://www.hcn.org/issues/47.11/why-rare-earth-mining-in-the-west-is-a-bust |author=Tim Heffernan |date=June 16, 2015 |access-date=September 26, 2017 |archive-date=November 3, 2021 |archive-url=https://web.archive.org/web/20211103103815/https://www.hcn.org/issues/47.11/why-rare-earth-mining-in-the-west-is-a-bust |url-status=live}}</ref>

In Greenland, there is a significant dispute on whether to start a new rare-earth mine in [[Kvanefjeld]] due to environmental concerns.<ref>{{cite news |title=Greenland votes, split on rare earth metals mining |newspaper=Deutsche Welle |date=2021-06-04 |url=https://www.dw.com/en/greenland-votes-split-on-rare-earth-metals-mining/a-57113587 |access-date=2021-04-07 |language=en-GB |archive-date=June 21, 2022 |archive-url=https://web.archive.org/web/20220621090757/https://www.dw.com/en/greenland-votes-split-on-rare-earth-metals-mining/a-57113587 |url-status=live}}</ref>

==Geopolitical considerations==
[[File:USGS rare earth oxides production graph.PNG|thumb|right|alt=A U.S.G.S. graph of global rare-earth-oxide production trends, 1956–2008|Global rare-earth-oxide production trends, 1956-2008 ([[USGS]])]]
China has officially cited [[resource depletion]] and environmental concerns as the reasons for a nationwide crackdown on its rare-earth mineral production sector.<ref name=ReutersSept611>{{cite web |url=https://www.reuters.com/article/china-rare-earth-idUSL3E7K620P20110906 |title=China halts rare earth production at three mines |website=Reuters |access-date=2011-09-07 |date=2011-09-06 |archive-date=April 10, 2022 |archive-url=https://web.archive.org/web/20220410095530/https://www.reuters.com/article/china-rare-earth-idUSL3E7K620P20110906 |url-status=live}}</ref> However, non-environmental motives have also been imputed to China's rare-earth policy.<ref name="NYT"/> According to ''[[The Economist]]'', "Slashing their exports of rare-earth metals&nbsp;... 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."<ref>[https://www.economist.com/blogs/babbage/2010/09/rare-earth_metals "The Difference Engine: More precious than gold"] {{Webarchive|url=https://web.archive.org/web/20180423192601/https://www.economist.com/blogs/babbage/2010/09/rare-earth_metals |date=April 23, 2018}}. ''[[The Economist]]'' September 17, 2010.</ref> Furthermore, China currently has an effective monopoly on the world's REE Value Chain.<ref>{{cite journal |doi=10.1016/j.jsm.2016.05.002 |title=Strategic evaluations and mining process optimization towards a strong global REE supply chain |journal=Journal of Sustainable Mining |volume=15 |issue=1 |pages=26–35 |year=2016 |last1=Barakos |first1=G |last2=Gutzmer |first2=J |last3=Mischo |first3=H |doi-access=free}}</ref> (All of the refineries and processing plants that transform the raw ore into valuable elements.<ref>{{cite web |url=http://www.investopedia.com/terms/v/valuechain.asp |title=Value Chain |website=Investopedia |access-date=September 26, 2017 |archive-date=June 10, 2022 |archive-url=https://web.archive.org/web/20220610222900/https://www.investopedia.com/terms/v/valuechain.asp |url-status=live}}</ref>) 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."<ref>{{cite web |url=http://www.businessinsider.com/seventeen-metals-the-middle-east-has-oil-china-has-rare-earth-2011-1 |title=Seventeen Metals: 'The Middle East has oil, China has rare earth' |website=Business Insider |author=Dian L. Chu |date=Nov 11, 2010 |access-date=September 27, 2017 |archive-date=June 24, 2022 |archive-url=https://web.archive.org/web/20220624033304/https://www.businessinsider.com/seventeen-metals-the-middle-east-has-oil-china-has-rare-earth-2011-1 |url-status=live}}</ref>

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 to [[China]] in 2006<ref>{{cite web |first=C. |last=Cox |url=http://theanchorhouse.com/2006/11/ |title=Rare earth innovation: the silent shift to China |archive-url=https://web.archive.org/web/20080421031137/http://theanchorhouse.com/2006/11/ |archive-date=2008-04-21 |date=16 November 2006 |publisher=The Anchor House, Inc |access-date=29 February 2008}}</ref> (China's export quota only applies to the metal but not products made from these metals such as magnets).

It was reported,<ref name="nytimes">{{cite news |last=Bradsher |first=Keith |title=Amid Tension, China Blocks Vital Exports to Japan |url=https://www.nytimes.com/2010/09/23/business/global/23rare.html?_r=1&partner=rss&emc=rss |publisher=The New York Times Company |access-date=22 September 2010 |date=2010-09-22 |archive-date=April 23, 2022 |archive-url=https://web.archive.org/web/20220423200732/https://www.nytimes.com/2010/09/23/business/global/23rare.html?_r=1&partner=rss&emc=rss |url-status=live}}</ref> but officially denied,<ref name="wsjs">{{cite news |last=James T. Areddy, David Fickling And Norihiko Shirouzu |title=China Denies Halting Rare-Earth Exports to Japan |url=https://www.wsj.com/articles/SB10001424052748704062804575509640345070222?mod=WSJ_hps_LEFTTopStories |newspaper=Wall Street Journal |access-date=22 September 2010 |date=2010-09-23 |archive-date=June 15, 2022 |archive-url=https://web.archive.org/web/20220615124340/https://www.wsj.com/articles/SB10001424052748704062804575509640345070222?mod=WSJ_hps_LEFTTopStories |url-status=live}}</ref> that China instituted an [[economic sanctions|export ban]] on shipments of rare-earth oxides (but not alloys) to Japan on 22 September 2010, in response to [[2010 Senkaku boat collision incident|the detainment of a Chinese fishing boat captain]] by the [[Japanese Coast Guard]].<ref>[https://www.telegraph.co.uk/finance/newsbysector/industry/mining/7970872/Backlash-over-China-curb-on-metal-exports.html Backlash over the alleged China curb on metal exports] {{Webarchive|url=https://web.archive.org/web/20180415150316/https://www.telegraph.co.uk/finance/newsbysector/industry/mining/7970872/Backlash-over-China-curb-on-metal-exports.html |date=April 15, 2018}}, ''[[Daily Telegraph]]'', London, 29 Aug 2010. Retrieved 2010-08-30.</ref><ref name="Distillations"/> On September 2, 2010, a few days before the fishing boat incident, ''The Economist'' reported that "China&nbsp;... in July announced the latest in a series of annual export reductions, this time by 40% to precisely 30,258 tonnes."<ref>[http://www.economist.com/node/16944034 "Rare earths: Digging in"] ''[[The Economist]]'' September 2, 2010.</ref><ref name="Distillations">{{cite web |title=Rare Earths: The Hidden Cost to Their Magic", Distillations Podcast and transcript, Episode 242 |url=https://www.sciencehistory.org/distillations/podcast/rare-earths-the-hidden-cost-to-their-magic |website=Science History Institute |date=June 25, 2019 |access-date=28 August 2019 |archive-date=August 3, 2019 |archive-url=https://web.archive.org/web/20190803101711/https://www.sciencehistory.org/distillations/podcast/rare-earths-the-hidden-cost-to-their-magic |url-status=live}}</ref>

The [[United States Department of Energy]] in its 2010 Critical Materials Strategy report identified [[dysprosium]] as the element that was most critical in terms of import reliance.<ref>Mills, Mark P. [https://blogs.forbes.com/markpmills/2011/01/01/techs-mineral-infrastructure-time-to-emulate-chinas-rare-earth-policies/ "Tech's Mineral Infrastructure&nbsp;– Time to Emulate China's Rare Earth Policies."] {{Webarchive|url=https://web.archive.org/web/20110526090822/https://blogs.forbes.com/markpmills/2011/01/01/techs-mineral-infrastructure-time-to-emulate-chinas-rare-earth-policies/ |date=May 26, 2011}} ''[[Forbes]]'', 1 January 2010.</ref>

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." 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."<ref>{{cite web |url=http://journalistsresource.org/studies/government/international/usgs-china-rare-earth-industry |title=US Geological Survey: China's Rare-Earth Industry |publisher=Journalist's Resource.org |date=2011-07-18}}</ref>

The United States Geological Survey is actively surveying southern [[Afghanistan]] 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 in [[Helmand Province]] near the village of [[Khanashin]]. 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.<ref>{{cite magazine |author=Simpson, S. |title=Afghanistan's Buried Riches |magazine=Scientific American |date=October 2011}}</ref>

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.<ref>{{cite web |title=EU, U.S. exploring new sources of Rare Earth Minerals, should China limit exports |last1=Trakimavicius |first1=Lukas |date=25 February 2021 |publisher=Energy Post |url=https://energypost.eu/eu-u-s-exploring-new-sources-of-rare-earth-minerals-should-china-limit-exports/ |access-date=25 February 2021 |url-status=live |archive-url=https://web.archive.org/web/20220215100817/https://energypost.eu/eu-u-s-exploring-new-sources-of-rare-earth-minerals-should-china-limit-exports/ |archive-date=February 15, 2022}}</ref><ref name=":0">{{cite journal |last=Overland |first=Indra |date=2019-03-01 |title=The geopolitics of renewable energy: Debunking four emerging myths |journal=Energy Research & Social Science |volume=49 |pages=36–40 |doi=10.1016/j.erss.2018.10.018 |issn=2214-6296 |doi-access=free|bibcode=2019ERSS...49...36O |hdl=11250/2579292 |hdl-access=free }}</ref> 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.<ref name=":0"/>

==In popular culture==

The plot of [[Eric Ambler]]'s now-classic 1967 international crime-thriller ''[[Dirty Story (novel)|Dirty Story]]'' (aka ''This Gun for Hire'', but not to be confused with the movie ''[[This Gun for Hire]]'' (1942)) 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.<ref>{{Cite web|url=https://www.kirkusreviews.com/book-reviews/a/eric-ambler/dirty-story/|title=Book Reviews, Sites, Romance, Fantasy, Fiction|website=Kirkus Reviews}}</ref>

==See also==
{{Portal|Geology}}
* [[List of elements facing shortage]]
* [[Material passport]]: lists used materials in products
* [[Pensana Salt End]]
* [[Precious metal]]
* [[Rare-earth magnet]]
* [[Rare-earth mineral]]

==References==
{{Reflist}}

==External links==
{{External media
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| float=upright
| headerimage=
| audio1=[https://www.sciencehistory.org/distillations/podcast/rare-earths-the-hidden-cost-to-their-magic "Rare Earths: The Hidden Cost to Their Magic"], Distillations Podcast and transcript, Episode 242, June 25, 2019, [[Science History Institute]] |video1=[https://www.sciencehistory.org/rare-earth-elements-project "10 ways rare earth elements make life better"], animation, [[Science History Institute]] |video2=[https://www.youtube.com/watch?v=aglMNj4hld0 "Rare-Earth Elements: The Intersection of Science and Society"], presentation and discussion led by [[Ira Flatow]], [[Science History Institute]], September 24, 2019}}
* {{Commons category-inline|Rare earth elements}}
* {{Britannica|491579|Rare-earth element}}

{{Periodic table (navbox)}}
{{Navbox periodic table}}
{{Industries}}
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[[Category:Rare earth elements| ]]
[[Category:Metallic elements]]
[[Category:Sets of chemical elements]]