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The document discusses rare-earth elements, which are a set of 17 metals that are difficult to separate due to similar chemical properties. Some key points: - Rare-earth elements were discovered as components of minerals found in Sweden in the late 18th century. Their separation and identification proved challenging. - Between 1839-1901, improved techniques like spectroscopy allowed scientists like Mosander, Lecoq de Boisbaudran, and Crookes to isolate and name additional rare-earth elements like cerium, lanthanum, and europium. - Despite their name, rare-earth elements are relatively abundant in Earth's crust, with cerium being the 25th most common element. They often occur together

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Rare-earthelement From Wikipedia,the free encyclopedia Jumpto navigationJumptosearch Rare-earthelements inthe periodictable Hydrogen Helium Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon Potassium Calcium Scandium Titanium Vanadium
Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium
Iodine Xenon Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium
Lead Bismuth Polonium Astatine Radon Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium
Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson Rare-earthore (shownwitha19 mm diameterUS1 centcoin forsize comparison) Refinedrare-earthoxidesare heavygrittypowdersusuallybrownorblack,butcan be lightercolorsas shownhere.Legend: gadolinium·praseodymium·cerium samarium· lanthanum neodymium The rare-earthelements(REE),alsocalledthe rare-earthmetalsor(incontext) rare-earthoxides,orthe lanthanides[1] (thoughyttriumandscandiumare usuallyincludedasrare-earths) are asetof 17 nearly- indistinguishable lustroussilvery-whitesoftheavymetals.[2] Scandiumandyttriumare consideredrare- earthelementsbecausetheytendtooccurin the same ore depositsasthe lanthanidesandexhibit similarchemical properties,buthave differentelectronicandmagneticproperties.[3][4] These metalstarnishslowlyinairat room temperature andreactslowlywithcoldwatertoform hydroxides,liberatinghydrogen.Theyreactwithsteamtoformoxides,andat elevatedtemperature (400 °C) ignite spontaneously. These elementsandtheircompoundshave nobiological function.The water-soluble compoundsare mildlytomoderatelytoxic,butthe insolubleonesare not.[5] Compoundscontainingrare earthshave diverseapplicationsinelectricalandelectroniccomponents, lasers,glass,magneticmaterials,andindustrial processes.
Despite theirname,rare-earthelementsare relativelyplentiful inEarth'scrust,withceriumbeingthe 25th mostabundantelementat68 parts per million,more abundantthancopper.All isotopesof promethiumare radioactive,anditdoesnotoccur naturallyinthe earth'scrust,exceptfora trace amountgeneratedbyspontaneousfissionof uranium238. Theyare oftenfoundinmineralswith thorium,andlesscommonlyuranium.Because of theirgeochemical properties,rare-earthelementsare typicallydispersedandnotoftenfoundconcentratedinrare-earthminerals.Consequently, economicallyexploitableore depositsare sparse (i.e."rare").[6] The firstrare-earthmineral discovered (1787) was gadolinite,ablackmineral composedof cerium, yttrium, iron,silicon,andotherelements. Thismineral wasextractedfroma mine inthe village of YtterbyinSweden;fourof the rare-earth elementsbearnamesderivedfromthissingle location. Contents 1 List 2 Discoveryandearlyhistory 2.1 Spectroscopicidentification 2.2 Early classification 2.3 Lightversusheavyclassification 3 Origin 4 Geological distribution 4.1 Geochemistryapplications 5 Production 5.1 China 5.2 Outside China 5.3 Othersources 5.4 Methods 6 Properties 7 Uses 8 Environmental considerations 8.1 RecyclingandreusingREEs 8.2 Impact of REE contamination 8.3 Remediationafterpollution
9 Geo-political considerations 10 See also 11 References 12 External links List A table listingthe 17 rare-earthelements,theiratomicnumberandsymbol,the etymologyof their names,andtheirmainuses(see alsoApplicationsof lanthanides) isprovidedhere.Some of the rare- earthelementsare namedafterthe scientistswhodiscoveredthem,orelucidatedtheirelemental properties,andsome afterthe geographical locationswhere discovered. Overviewof rare-earthmetalproperties Z Symbol Name Etymology Selectedapplications Abundance[7][8] (ppm[a]) 21 Sc Scandium fromLatin Scandia(Scandinavia). Lightaluminium-scandium alloysforaerospace components,additiveinmetal-halidelampsandmercury-vaporlamps,[9] radioactive tracingagentinoil refineries 22 39 Y Yttriumafterthe village of Ytterby,Sweden,wherethe firstrare earthore was discovered. Yttriumaluminiumgarnet(YAG) laser,yttriumvanadate (YVO4) ashostfor europiumin televisionredphosphor,YBCOhigh-temperature superconductors,yttria-stabilizedzirconia(YSZ) (used intooth crowns;as refractorymaterial - inmetal alloysusedinjetengines,andcoatingsof enginesand industrial gasturbines;electroceramics - formeasuringoxygenandpHof hot watersolutions,i.e.infuel cells;ceramicelectrolyte - usedinsolidoxide fuel cell;jewelry - foritshardnessandoptical properties; do-it-yourself hightemperature ceramicsandcementsbasedonwater),yttriumirongarnet (YIG) microwave filters,[9] energy-efficientlightbulbs(partof triphosphorwhite phosphorcoatingin fluorescenttubes,CFLsandCCFLs,and yellow phosphorcoatinginwhite LEDs),[10] sparkplugs,gas mantles,additive tosteel,aluminiumandmagnesium alloys,cancertreatments,cameraandrefractive telescope lenses(due tohighrefractive indexandverylow thermal expansion),batterycathodes(LYP) 33 57 La Lanthanum fromthe Greek"lanthanein",meaningtobe hidden. Highrefractive index and alkali-resistantglass,flint,hydrogenstorage,battery-electrodes,cameraandrefractive telescope lenses,fluidcatalyticcrackingcatalystforoil refineries 39 58 Ce Cerium afterthe dwarf planetCeres,namedafterthe Romangoddessof agriculture. Chemical oxidizingagent,polishingpowder,yellow colorsinglassandceramics,catalystforself- cleaningovens,fluidcatalyticcrackingcatalystforoil refineries,ferroceriumflintsforlighters,robust intrinsicallyhydrophobiccoatingsforturbine blades[11]66.5 59 Pr Praseodymium fromthe Greek"prasios",meaningleek-green,and"didymos",meaning twin. Rare-earthmagnets,lasers,core material forcarbonarc lighting,colorantinglassesand
enamels,additiveindidymiumglassusedinweldinggoggles,[9] ferroceriumfiresteel (flint) products, single mode fiberoptical amplifiers(asadopantof fluoride glass) 9.2 60 Nd Neodymium fromthe Greek"neos",meaningnew,and"didymos",meaningtwin. Rare-earthmagnets,lasers,violetcolorsinglassand ceramics,didymiumglass,ceramic capacitors,electricmotorsof electricautomobiles 41.5 61 Pm Promethium afterthe Titan Prometheus,whobroughtfire tomortals. Nuclear batteries,luminouspaint 1×10−15 [12][b] 62 Sm Samarium aftermine official,Vasili Samarsky-Bykhovets. Rare-earthmagnets, lasers,neutroncapture,masers,control rodsof nuclearreactors7.05 63 Eu Europium afterthe continentof Europe. Redand blue phosphors,lasers, mercury-vaporlamps,fluorescentlamps,NMRrelaxationagent 2 64 Gd Gadolinium afterJohanGadolin(1760–1852), tohonor hisinvestigationof rare earths. Highrefractive index glassorgarnets,lasers,X-raytubes,Bubble (computer) memories,neutron capture,MRI contrast agent,NMR relaxationagent,magnetostrictive alloyssuchasGalfenol,steel and chromiumalloysadditive,magneticrefrigeration(usingsignificantmagnetocaloriceffect),positron emissiontomographyscintillatordetectors,substrate formagneto-optical films,highperformance high temperature superconductors,ceramicelectrolyte usedinsolidoxide fuel cells,oxygendetectors, possiblyincatalyticconversionof automobile fumes. 6.2 65 Tb Terbium afterthe village of Ytterby,Sweden. Additive inNeodymiumbased magnets,greenphosphors,lasers,fluorescentlamps(aspartof the white tribandphosphorcoating), magnetostrictivealloyssuchasterfenol-D,naval sonarsystems,stabilizerof fuel cells 1.2 66 Dy Dysprosium fromthe Greek"dysprositos",meaninghardtoget. Additive in Neodymiumbasedmagnets,lasers,magnetostrictivealloyssuchasterfenol-D,harddiskdrives 5.2 67 Ho Holmium afterStockholm(inLatin,"Holmia"),nativecityof one of itsdiscoverers. Lasers,wavelengthcalibrationstandardsforoptical spectrophotometers,magnets 1.3 68 Er Erbium afterthe village of Ytterby,Sweden. Infraredlasers,vanadiumsteel,fiber- optictechnology 3.5 69 Tm Thulium afterthe mythological northernlandof Thule. Portable X-ray machines,metal-halidelamps,lasers 0.52 70 Yb Ytterbium afterthe village of Ytterby,Sweden. Infraredlasers,chemical reducingagent,decoyflares,stainlesssteel,stressgauges,nuclearmedicine,monitoringearthquakes 3.2 71 Lu Lutetium afterLutetia,the citythat laterbecame Paris. Positronemission tomography – PET scan detectors,high-refractive-indexglass,lutetiumtantalate hostsforphosphors, catalystusedinrefineries,LEDlightbulb 0.8 Parts permillioninearth'scrust,e.g.Pb=13 ppm No stable isotopesoccurringinnature.
A mnemonicforthe namesof the sixth-row elementsinorderis"Latelycollegepartiesneverproduce sexyEuropeangirlsthatdrinkheavilyeventhoughyoulook".[13] Discoveryandearlyhistory Rare earthswere mainlydiscoveredascomponentsof minerals.Ytterbiumwasfoundinthe "ytterbite" (renamedtogadolinitein1800). It wasdiscoveredbyLieutenantCarl Axel Arrheniusin1787 at a quarry inthe village of Ytterby,Sweden.[14] Arrhenius's"ytterbite"reachedJohanGadolin,aRoyal Academyof Turku professor,andhisanalysisyieldedanunknownoxide ("earth"),whichhe calledyttria.Anders Gustav Ekebergisolatedberylliumfromthe gadolinite butfailedtorecognizeotherelementsinthe ore. Afterthisdiscoveryin1794, a mineral fromBastnäsnearRiddarhyttan,Sweden,whichwasbelievedto be an iron–tungstenmineral,wasre-examinedbyJönsJacobBerzeliusandWilhelmHisinger.In1803 theyobtainedawhite oxide andcalleditceria.MartinHeinrichKlaprothindependentlydiscoveredthe same oxide andcalleditochroia. Ittook another30 yearsfor researcherstodeterminethatother elementswere containedinthe twooresceriaand yttria(the similarityof the rare-earthmetals' chemical propertiesmade theirseparationdifficult). In 1839 Carl Gustav Mosander,an assistantof Berzelius,separatedceriabyheatingthe nitrate and dissolvingthe productinnitricacid.He calledthe oxide of the soluble saltlanthana.Ittookhimthree more yearsto separate the lanthanafurtherintodidymiaandpure lanthana.Didymia, althoughnot furtherseparable byMosander'stechniques,wasinfactstill amixture of oxides. In 1842 Mosanderalsoseparatedthe yttriaintothree oxides:pure yttria,terbiaanderbia(all the names are derivedfromthe townname "Ytterby").The earth givingpinksaltshe calledterbium;the one that yieldedyellowperoxide he callederbium. So in1842 the numberof knownrare-earthelementshadreachedsix:yttrium, cerium,lanthanum, didymium,erbiumandterbium. NilsJohanBerlinandMarc Delafontaine triedalsotoseparate the crude yttriaandfoundthe same substancesthatMosanderobtained,butBerlinnamed(1860) the substance givingpinksaltserbium, and Delafontaine namedthe substancewiththe yellow peroxide terbium.Thisconfusionledto several false claimsof newelements,suchasthe mosandriumof J.Lawrence Smith,orthe philippiumand decipiumof Delafontaine.Due tothe difficultyinseparatingthe metals(anddeterminingthe separation iscomplete),the total numberof false discoverieswasdozens,[15][16] withsome puttingthe total numberof discoveriesatoverahundred.[17] Spectroscopicidentification
There were nofurtherdiscoveriesfor30 years,and the elementdidymiumwaslistedinthe periodic table of elementswithamolecularmassof 138. In 1879 Delafontaineusedthe new physical processof optical flame spectroscopyandfoundseveral new spectral linesindidymia.Alsoin1879, the new elementsamariumwasisolatedbyPaul Émile Lecoqde Boisbaudranfromthe mineral samarskite. The samaria earthwas furtherseparatedbyLecoqde Boisbaudranin1886, and a similarresultwas obtainedbyJeanCharlesGalissardde Marignacby directisolationfromsamarskite.Theynamedthe elementgadoliniumafterJohanGadolin,anditsoxide wasnamed"gadolinia". Furtherspectroscopicanalysisbetween1886 and 1901 of samaria,yttria,and samarskite byWilliam Crookes,Lecoqde BoisbaudranandEugène-AnatoleDemarçayyieldedseveral new spectroscopiclines that indicatedthe existence of anunknownelement.The fractionalcrystallizationof the oxidesthen yieldedeuropiumin1901. In 1839 the thirdsource for rare earthsbecame available.Thisisamineral similartogadolinite, uranotantalum(nowcalled"samarskite").Thismineral fromMiassinthe southernUral Mountainswas documentedbyGustavRose.The RussianchemistR.Harmannproposedthata new elementhe called "ilmenium"shouldbe presentinthismineral,butlater,ChristianWilhelmBlomstrand,Galissardde Marignac, and HeinrichRose foundonlytantalumandniobium(columbium) init. The exact numberof rare-earthelementsthatexistedwashighlyunclear,andamaximumnumberof 25 was estimated.The use of X-rayspectra(obtainedbyX-raycrystallography)byHenryGwyn Jeffreys Moseleymade itpossible toassignatomicnumberstothe elements.Moseleyfoundthatthe exact numberof lanthanideshadtobe 15, and that element61 hadyet to be discovered. Usingthese factsabout atomicnumbersfromX-raycrystallography, Moseleyalsoshowedthathafnium (element72) wouldnotbe a rare-earthelement.MoseleywaskilledinWorldWar I in1915, years before hafniumwasdiscovered.Hence,the claimof GeorgesUrbainthathe had discoveredelement72 was untrue.Hafniumisan elementthatliesinthe periodictable immediatelybelow zirconium,and hafniumandzirconiumare verysimilarintheirchemical andphysical properties. Duringthe 1940s, FrankSpeddingandothersinthe UnitedStates(duringthe ManhattanProject) developedchemical ion-exchangeproceduresforseparatingandpurifyingthe rare-earthelements.This methodwasfirstappliedtothe actinidesforseparatingplutonium-239andneptuniumfromuranium, thorium,actinium,andthe otheractinidesinthe materials producedinnuclearreactors.Plutonium-239 was verydesirable because itisafissile material.
The principal sourcesof rare-earthelementsare the mineralsbastnäsite,monazite,andlopariteandthe lateriticion-adsorptionclays.Despite theirhighrelative abundance,rare-earthmineralsare more difficulttomine andextractthanequivalentsourcesof transitionmetals(dueinpartto theirsimilar chemical properties),makingthe rare-earthelementsrelativelyexpensive.Theirindustrial use wasvery limiteduntilefficientseparationtechniquesweredeveloped,suchasionexchange,fractional crystallizationandliquid–liquidextractionduringthe late 1950s and early1960s.[18] Some ilmeniteconcentratescontainsmall amountsof scandiumandother rare-earthelements,which couldbe analysedbyXRF.[19] Early classification Before the time thation-exchangemethodsandelutionwere available,the separationof the rare earths was primarilyachievedbyrepeatedprecipitationorcrystallization.In those days,the firstseparation was intotwomaingroups,the ceriumearths(scandium, lanthanum, cerium, praseodymium, neodymium, andsamarium) andthe yttriumearths(yttrium,dysprosium,holmium, erbium, thulium, ytterbium,andlutetium).Europium,gadolinium,andterbiumwere eitherconsideredasa separate groupof rare-earthelements(the terbiumgroup),oreuropiumwasincludedinthe ceriumgroup,and gadoliniumandterbiumwereincludedinthe yttriumgroup.The reasonforthisdivisionarose from the difference insolubilityof rare-earthdouble sulfateswithsodiumandpotassium.The sodiumdouble sulfatesof the ceriumgroupare poorlysoluble,those of the terbiumgroupslightly,andthose of the yttriumgroupare verysoluble.[20] Sometimes,the yttriumgroupwasfurthersplitintothe erbium group(dysprosium,holmium,erbium,andthulium)andthe ytterbiumgroup(ytterbiumandlutetium), but todaythe maingroupingisbetweenthe ceriumandthe yttriumgroups.[21] Today,the rare-earth elementsare classifiedaslightorheavyrare-earthelements,ratherthaninceriumandyttriumgroups. Lightversusheavyclassification The classificationof rare-earthelementsisinconsistentbetweenauthors.[22] The mostcommon distinctionbetweenrare-earthelementsismade byatomicnumbers;those withlow atomicnumbers are referredtoas lightrare-earthelements(LREE),those withhighatomicnumbersare the heavyrare- earthelements(HREE),andthose thatfall inbetweenare typicallyreferredtoas the middle rare-earth elements(MREE).[23] Commonly,rare-earthelementswithatomicnumbers57to 61 (lanthanumto promethium) are classifiedaslightandthose withatomicnumbersgreaterthan62[clarificationneeded >62 or >61?] are classifiedasheavy-rare earthelements.[24] Increasingatomicnumbersbetweenlight and heavyrare-earthelementsanddecreasingatomicradii throughoutthe seriescauseschemical variations.[24] Europiumisexemptof thisclassificationasithas twovalence states:Eu2+ and Eu3+.[24] Yttriumis groupedasheavyrare-earthelementdue tochemical similarities.[25] The breakbetweenthe twogroups issometimesputelsewhere,suchasbetweenelements63(europium) and64 (gadolinium).[26] The actual metallicdensitiesof these twogroupsoverlap,withthe "light"group havingdensitiesfrom6.145 (lanthanum) to7.26 (promethium) or7.52 (samarium) g/cc,and the "heavy"
groupfrom 6.965 (ytterbium) to9.32 (thulium),aswell asincludingyttriumat4.47. Europiumhas a densityof 5.24. Origin Rare-earthelements,exceptscandium,are heavierthanironandthus are producedbysupernova nucleosynthesisorbythe s-processinasymptoticgiantbranchstars. Innature,spontaneousfissionof uranium-238producestrace amountsof radioactive promethium, butmostpromethiumissynthetically producedinnuclearreactors. Due to theirchemical similarity,the concentrationsof rare earthsinrocks are onlyslowlychangedby geochemical processes,makingtheirproportionsuseful for geochronologyanddatingfossils. Geological distribution Abundance of elementsinEarth'scrust permillionSi atoms(yaxisislogarithmic) As seeninthe chart to the right,rare-earthelementsare foundonearthat similarconcentrationsto manycommon transitionmetals.The mostabundantrare-earthelementiscerium, whichisactuallythe 25th mostabundantelementinEarth'scrust,having68 parts permillion(aboutascommonas copper). The exceptionisthe highlyunstable andradioactivepromethium"rare earth"isquite scarce.The longest-livedisotope of promethiumhasahalf-life of 17.7years,so the elementexistsinnature inonly negligible amounts(approximately572 g in the entire Earth'scrust).[27] Promethiumisone of the two elementsthatdonothave stable (non-radioactive) isotopesandare followedby(i.e.withhigheratomic number) stable elements(the otherbeingtechnetium). The rare-earthelementsare oftenfoundtogether.Duringthe sequentialaccretionof the Earth,the dense rare-earthelementswere incorporatedintothe deeperportionsof the planet.Early differentiationof moltenmaterial largelyincorporatedthe rare-earthsintomantlerocks.[28] The high fieldstrength[clarificationneeded]andlarge ionicradii of rare-earthsmake themincompatible withthe crystal latticesof mostrock-formingminerals,soREE will undergostrongpartitioningintoameltphase if one is present.[28] REEare chemicallyverysimilarandhave alwaysbeendifficulttoseparate,buta gradual decrease inionicradiusfromlightREE (LREE) to heavyREE (HREE),calledlanthanide contraction,can produce a broad separationbetweenlightandheavyREE.The larger ionicradii of LREE make themgenerallymore incompatible thanHREEin rock-formingminerals,andwill partitionmore stronglyintoa meltphase,whileHREEmay prefertoremaininthe crystalline residue,particularlyif it containsHREE-compatible mineralslike garnet.[28][29] The resultisthatall magma formedfrompartial meltingwill alwayshave greaterconcentrationsof LREEthan HREE, and individualmineralsmaybe dominatedbyeitherHREEor LREE, dependingonwhichrange of ionicradii bestfitsthe crystal lattice.[28]
Amongthe anhydrousrare-earthphosphates,itisthe tetragonal mineral xenotime thatincorporates yttriumandthe HREE, whereasthe monoclinicmonazite phase incorporatesceriumandthe LREE preferentially.The smallersize of the HREEallowsgreatersolidsolubilityinthe rock-formingminerals that make up Earth's mantle,andthusyttriumand the HREE show lessenrichmentinEarth'scrust relative tochondriticabundance thandoesceriumandthe LREE. Thishas economicconsequences:large ore bodiesof LREE are knownaroundthe worldandare beingexploited.Ore bodiesforHREE are more rare, smaller,andlessconcentrated.Mostof the current supplyof HREE originatesinthe "ion- absorptionclay"oresof SouthernChina.Some versionsprovide concentratescontainingabout65% yttriumoxide,withthe HREEbeingpresentinratiosreflectingthe Oddo–Harkinsrule:even-numbered REE at abundancesof about5% each,and odd-numberedREEat abundancesof about1% each.Similar compositionsare foundinxenotime orgadolinite.[30] Well-knownmineralscontainingyttrium,andotherHREE, include gadolinite,xenotime,samarskite, euxenite,fergusonite,yttrotantalite,yttrotungstite,yttrofluorite(avarietyof fluorite),thalenite, yttrialite.Small amountsoccurinzircon,whichderivesitstypical yellowfluorescence from some of the accompanyingHREE. The zirconiummineral eudialyte,suchasisfoundinsouthernGreenland,contains small butpotentiallyusefulamountsof yttrium.Of the above yttriumminerals,mostplayedapartin providingresearchquantitiesof lanthanidesduringthe discoverydays.Xenotime isoccasionally recoveredasa byproductof heavy-sandprocessing,butisnotas abundantas the similarlyrecovered monazite (whichtypicallycontainsafewpercentof yttrium).UraniumoresfromOntariohave occasionallyyieldedyttriumasabyproduct.[30] Well-knownmineralscontainingcerium,andotherLREE, include bastnäsite,monazite,allanite,loparite, ancylite,parisite,lanthanite,chevkinite,cerite,stillwellite,britholite,fluocerite,andcerianite.Monazite (marine sandsfromBrazil,India,orAustralia;rockfromSouthAfrica),bastnäsite (fromMountainPass rare earthmine,or several localitiesinChina),andloparite (KolaPeninsula,Russia)have beenthe principal oresof ceriumandthe lightlanthanides.[30] Enricheddepositsof rare-earthelementsatthe surface of the Earth, carbonatitesandpegmatites,are relatedtoalkaline plutonism,anuncommonkindof magmatismthatoccursin tectonicsettingswhere there isriftingorthat are near subductionzones.[29] Ina riftsetting,the alkaline magmaisproducedby verysmall degreesof partial melting(<1%) of garnetperidotiteinthe uppermantle (200to 600 km depth).[29] Thismeltbecomesenrichedinincompatibleelements,like the rare-earthelements,by leachingthemoutof the crystalline residue.The resultantmagmarisesasa diapir,ordiatreme,along pre-existingfractures,andcanbe emplaceddeepinthe crust,oreruptedatthe surface.Typical REE enricheddepositstypesforminginriftsettingsare carbonatites,andA- andM-Type granitoids.[28][29] Nearsubductionzones,partial meltingof the subductingplate withinthe asthenosphere (80to200 km depth) producesavolatile-richmagma(highconcentrationsof CO2andwater),withhigh concentrations of alkaline elements,andhighelementmobilitythatthe rare-earthsare stronglypartitionedinto.[28]
Thismeltmay alsorise alongpre-existingfractures,andbe emplacedinthe crustabove the subducting slabor eruptedat the surface. REE enricheddepositsformingfromthesemeltsare typicallyS-Type granitoids.[28][29] Alkaline magmasenrichedwithrare-earthelementsincludecarbonatites,peralkalinegranites (pegmatites),andnephelinesyenite.CarbonatitescrystallizefromCO2-richfluids,whichcanbe producedbypartial meltingof hydrous-carbonatedlherzolite toproduce aCO2-richprimarymagma, by fractional crystallizationof analkaline primarymagma,orbyseparationof a CO2-richimmiscible liquid from.[28][29] These liquidsare mostcommonlyforminginassociationwithverydeepPrecambrian Cratons,like the onesfoundinAfricaandthe CanadianShield.[28] Ferrocarbonatitesare the most commontype of carbonatite tobe enrichedinREE, andare oftenemplacedaslate-stage, brecciated pipesatthe core of igneouscomplexes;theyconsistof fine-grainedcalcite andhematite,sometimes withsignificantconcentrationsof ankerite andminorconcentrationsof siderite.[28][29] Large carbonatite depositsenrichedinrare-earthelementsinclude MountWeldinAustralia,ThorLake in Canada,ZandkopsdriftinSouthAfrica,andMountainPassinthe USA.[29] Peralkalinegranites(A-Type granitoids) have veryhighconcentrationsof alkaline elementsandverylow concentrationsof phosphorus;theyare depositedatmoderate depthsinextensionalzones,oftenasigneousring complexes,oras pipes,massivebodies,andlenses.[28][29] These fluidshave verylow viscositiesand highelementmobility,whichallowsforcrystallizationof large grains,despite arelativelyshort crystallizationtimeuponemplacement;theirlarge grainsize iswhythese depositsare commonly referredtoas pegmatites.[29] Economicallyviable pegmatitesare dividedintoLithium-Cesium-Tantalum (LCT) and Niobium-Yttrium-Fluorine(NYF) types;NYFtypesare enrichedinrare-earthminerals. Examplesof rare-earthpegmatitedepositsincludeStrange Lake inCanada,andKhaladean-Buregteyin Mongolia.[29] Nepheline syenite(M-Type granitoids) depositsare 90% feldsparandfeldspathoid minerals,andare depositedinsmall,circularmassifs.Theycontainhighconcentrationsof rare-earth- bearingaccessoryminerals.[28][29] Forthe mostpart these depositsare small butimportantexamples include Illimaussaq-KvanefeldinGreenland,andLovozerainRussia.[29] Rare-earthelementscanalsobe enrichedindepositsbysecondaryalterationeitherbyinteractionswith hydrothermal fluidsormeteoricwaterorbyerosionandtransportof resistate REE-bearingminerals. Argillizationof primarymineralsenrichesinsolubleelementsbyleachingoutsilicaandothersoluble elements,recrystallizingfeldsparintoclaymineralssuchkaolinite,halloysiteandmontmorillonite.In tropical regionswhere precipitationishigh,weatheringformsa thickargillizedregolith,thisprocessis calledsupergeneenrichmentandproduceslaterite deposits;heavyrare-earthelementsare incorporatedintothe residual claybyabsorption.Thiskindof depositisonlyminedforREEinSouthern China,where the majorityof global heavyrare-earthelementproductionoccurs.REE-lateritesdoform elsewhere,includingoverthe carbonatite atMountWeldinAustralia.REEmay alsoby extractedfrom placerdepositsif the sedimentaryparentlithologycontainedREE-bearing,heavyresistateminerals.[29] In 2011, YasuhiroKato, a geologistatthe Universityof Tokyowholedastudyof PacificOceanseabed mud,publishedresultsindicatingthe mudcouldholdrichconcentrationsof rare-earthminerals.The
deposits,studiedat78 sites,came from"[h]otplumesfromhydrothermal ventspull[ing] these materials out of seawateranddeposit[ing] themonthe seafloor,bitbybit,overtensof millionsof years.One square patch of metal-richmud2.3 kilometerswide mightcontain enoughrare earthstomeetmostof the global demandfora year,Japanese geologistsreportinNature Geoscience.""Ibelieve thatrare[- ]earthresourcesunderseaare muchmore promisingthanon-landresources,"saidKato. "[C]oncentrationsof rare earths were comparable tothose foundinclaysminedinChina.Some deposits containedtwice asmuchheavyrare earthssuch as dysprosium, acomponentof magnetsinhybridcar motors."[30][31] Geochemistryapplications The applicationof rare-earthelementsto geologyisimportanttounderstandingthe petrological processesof igneous,sedimentaryandmetamorphicrockformation.Ingeochemistry,rare-earth elementscanbe usedtoinferthe petrological mechanismsthathave affectedarockdue to the subtle atomicsize differencesbetweenthe elements,whichcausespreferentialfractionationof some rare earthsrelative toothersdependingonthe processesatwork.[23] In geochemistry,rare-earthelementsare typicallypresentedinnormalized"spider"diagrams,inwhich concentrationof rare-earthelementsare normalizedtoareference standardandare thenexpressedas the logarithmtothe base 10 of the value.Commonly,the rare-earthelementsare normalizedto chondriticmeteorites,asthese are believedtobe the closestrepresentationof unfractionatedsolar systemmaterial.However,othernormalizingstandardscanbe applieddependingonthe purpose of the study.Normalizationtoa standardreference value,especiallyof amaterial believedtobe unfractionated,allowsthe observedabundancestobe comparedtoinitial abundancesof the element.[23] Normalizationalsoremovesthe pronounced'zig-zag'patterncausedbythe differencesin abundance betweenevenandoddatomicnumbers.The trendsthatare observed in"spider"diagrams are typicallyreferredtoas"patterns",whichmaybe diagnosticof petrological processesthathave affectedthe material of interest.[23] The rare-earthelementspatternsobservedinigneousrocksare primarilyafunctionof the chemistryof the source where the rock came from,as well asthe fractionationhistorythe rockhasundergone.[23] Fractionationisinturna functionof the partitioncoefficientsof eachelement.Partitioncoefficientsare responsible forthe fractionation of atrace elements(includingrare-earthelements)intothe liquid phase (the melt/magma) intothe solidphase (the mineral).If anelementpreferentiallyremainsinthe solidphase itistermed‘compatible’,anditpreferentiallypartitionsintothe meltphase itisdescribedas ‘incompatible’.[23] Eachelementhasa differentpartitioncoefficient,andtherefore fractionatesinto solidandliquidphasesdistinctly.These conceptsare alsoapplicabletometamorphicandsedimentary petrology.
In igneous rocks,particularlyinfelsicmelts,the followingobservationsapply:anomaliesineuropiumare dominatedbythe crystallizationof feldspars.Hornblende,controlsthe enrichmentof MREE compared to LREE and HREE. Depletionof LREErelative toHREE may be due to the crystallizationof olivine, orthopyroxene,andclinopyroxene.Onthe otherhand,depletionof HREErelative toLREE may be due to the presence of garnet,as garnetpreferentiallyincorporatesHREEintoitscrystal structure.The presence of zirconmayalsocause a similareffect.[23] In sedimentaryrocks,rare-earthelementsinclasticsedimentsare a representationprovenance.The rare-earthelementconcentrationsare nottypicallyaffectedbyseaandriverwaters,asrare-earth elementsare insoluble andthushave verylow concentrationsinthese fluids.Asaresult,whena sedimentistransported,rare-earthelementconcentrationsare unaffectedbythe fluidandinsteadthe rock retainsthe rare-earthelementconcentrationfromitssource.[23] Seaand riverwaterstypicallyhave lowrare-earthelementconcentrations.However,aqueous geochemistryisstillveryimportant.Inoceans,rare-earthelementsreflectinputfromrivers, hydrothermal vents,andaeoliansources;[23] thisisimportantin the investigationof oceanmixingand circulation.[25] Rare-earthelementsare alsouseful fordatingrocks,assome radioactive isotopesdisplaylonghalf-lives. Of particularinterestare the 138La-138Ce, 147Sm-143Nd, and 176Lu-176Hf systems.[25] Production Global production1950–2000 Until 1948, mostof the world'srare earthswere sourcedfromplacersanddepositsinIndiaandBrazil. Throughthe 1950s, SouthAfricawas the world'srare-earthsource,froma monazite-richreef atthe Steenkampskraalmine inWesternCape province.[32] Throughthe 1960s until the 1980s, the Mountain Passrare earth mine inCaliforniamade the UnitedStatesthe leadingproducer.Today,the Indianand SouthAfricandepositsstillproduce some rare-earthconcentrates,but theyare dwarfedbythe scale of Chinese production.In2017, Chinaproduced81% of the world'srare-earthsupply,mostlyinInner Mongolia,[6][33] althoughithadonly36.7% of reserves.Australiawasthe secondandonlyothermajor producerwith15% of worldproduction.[34] All of the world'sheavyrare earths(suchasdysprosium) come from Chinese rare-earthsourcessuchasthe polymetallicBayanObodeposit.[33][35] The Browns Range mine,located160 kmsoutheast of HallsCreekinnorthernWesternAustralia,iscurrentlyunder developmentandispositionedtobecome the firstsignificantdysprosiumproduceroutsideof China.[36]
Increaseddemandhasstrainedsupply,andthere isgrowingconcernthatthe worldmay soonface a shortage of the rare earths.[37] In several yearsfrom2009 worldwide demandforrare-earthelementsis expectedtoexceedsupplyby40,000 tonnesannuallyunlessmajornew sourcesare developed.[38] In 2013, itwas statedthat the demandforREEs wouldincrease due tothe dependenceof the EU on these elements,the factthatrare earth elementscannotbe substitutedbyotherelementsandthatREEs have a lowrecyclingrate.Furthermore,due tothe increaseddemandandlow supply,future pricesare expectedtoincrease andthere isa chance that countriesotherthanChinawill openREEmines.[39] REE isincreasingindemanddue tothe fact that theyare essential fornew andinnovative technologythatis beingcreated.These newproductsthatneedREEsto be producedare hightechnologyequipmentsuch as smart phones,digital cameras,computerparts,semiconductors,etc.Inaddition,these elementsare more prevalentinthe followingindustries:renewableenergytechnology,militaryequipment,glass making,andmetallurgy.[40] China See also:Rare earthstrade dispute These concernshave intensifieddue tothe actionsof China,the predominantsupplier.[41] Specifically, Chinahas announcedregulationsonexportsandacrackdownon smuggling.[42] OnSeptember1,2009, Chinaannouncedplanstoreduce itsexportquotato 35,000 tonsper yearin 2010–2015 to conserve scarce resourcesandprotectthe environment.[43] OnOctober19, 2010, ChinaDaily,citinganunnamed Ministryof Commerce official,reportedthatChinawill"furtherreduce quotasforrare[-]earthexports by 30 percentat mostnextyearto protectthe preciousmetalsfromover-exploitation."[44] The governmentinBeijingfurtherincreaseditscontrol byforcingsmaller,independentminerstomerge into state-ownedcorporations orface closure.Atthe endof 2010, Chinaannouncedthatthe firstround of exportquotasin2011 for rare earthswouldbe 14,446 tons,whichwasa 35% decrease fromthe previousfirstroundof quotasin2010.[45] Chinaannouncedfurtherexportquotason 14 July2011 for the secondhalf of the yearwithtotal allocationat30,184 tons withtotal productioncappedat93,800 tonnes.[46] InSeptember2011, Chinaannouncedthe haltinproductionof three of itseightmajorrare- earthmines,responsibleforalmost40%of China'stotal rare-earthproduction.[47] InMarch 2012, the US, EU, andJapan confrontedChinaatWTO about these exportandproductionrestrictions.China respondedwithclaimsthatthe restrictionshadenvironmentalprotectioninmind.[48][49] InAugust 2012, Chinaannouncedafurther20% reductioninproduction.[50] The UnitedStates,Japan,andthe EuropeanUnionfiledajointlawsuitwiththe WorldTrade Organizationin2012 againstChina,arguing that Chinashouldnotbe able to denysuch importantexports.[49] In response tothe openingof newminesinothercountries(LynasinAustraliaandMolycorpinthe UnitedStates),pricesof rare earthsdropped.[51] The price of dysprosiumoxidewas994 USD/kgin 2011, butdroppedto US$265/kg by 2014.[52] On August29, 2014, the WTO ruledthatChinahad brokenfree-tradeagreements,andthe WTO saidin the summaryof keyfindingsthat"the overall effectof the foreignanddomesticrestrictionsisto
encourage domesticextractionandsecure preferential use of those materialsbyChinese manufacturers."Chinadeclaredthatitwouldimplementthe rulingonSeptember26,2014, but would needsome time todo so.By January5, 2015, Chinahad liftedall quotasfromthe exportof rare earths, but exportlicenceswill still be required.[53] In 2019, Chinasuppliedbetween85%and 95% of the global demandforthe 17 rare earth powders,half of themsourcedfromMyanmar.[54] Afterthe 2021 militarycoupinthat country,future suppliesof critical oreswere possiblyconstrained.Additionally,itwasspeculatedthatthe PRCcouldagain reduce rare earthexportstocounter-acteconomicsanctionsimposedbythe US and EU countries.Rare earth metalsserve ascrucial materialsforEV-manufacturingandhigh-techmilitaryapplications.[55] Outside China As a resultof the increaseddemandandtighteningrestrictionsonexportsof the metalsfromChina, some countriesare stockpilingrare-earthresources.[56] SearchesforalternativesourcesinAustralia, Brazil, Canada,SouthAfrica,Tanzania,Greenland,andthe UnitedStatesare ongoing.[57] Minesinthese countrieswere closedwhenChinaundercutworldpricesinthe 1990s, and itwill take a few yearsto restartproductionas there are many barrierstoentry.[42] One example isthe MountainPassmine in California,whichannounceditsresumptionof operationsonastart-upbasison August27, 2012.[33][58] OthersignificantsitesunderdevelopmentoutsideChinainclude Steenkampskraalin SouthAfrica,the world's highestgrade rare earthsand thoriummine,whichisgearingtogoback into production.Over80% of the infrastructure isalreadycomplete.[59] Otherminesincludethe Nolans ProjectinCentral Australia,the BokanMountainprojectinAlaska,the remote HoidasLake projectin northernCanada,[60] and the Mount WeldprojectinAustralia.[33][58][61] The HoidasLake projecthas the potential tosupplyabout10% of the $1 billionof REEconsumptionthatoccursin NorthAmerica everyyear.[62] Vietnamsigned anagreementinOctober2010 to supplyJapanwithrare earths[63] from itsnorthwesternLai ChâuProvince.[64] In the US, NioCorpDevelopmentLtdhaslauncheda long-shotefforttosecure $1.1 billion[65] toward openinganiobium,scandium, andtitanium mine atitsElkCreeksite insoutheastNebraska[66] which may be able to produce as muchas 7200 tonnesof ferroniobiumand95 tonnesof scandiumtrioxide annually.[67] Alsounderconsiderationforminingare sitessuchasThor Lake inthe NorthwestTerritories,andvarious locationsinVietnam.[33][38][68] Additionally,in2010, a large depositof rare-earthmineralswas discoveredinKvanefjeldinsouthernGreenland.[69] Pre-feasibilitydrillingatthissite hasconfirmed significantquantitiesof blacklujavrite,whichcontainsabout1% rare-earthoxides(REO).[70] The EuropeanUnionhas urgedGreenlandtorestrictChinese developmentof rare-earthprojectsthere,but as of early2013, the governmentof Greenlandhassaidthatit hasno plansto impose such restrictions.[71] ManyDanishpoliticianshave expressedconcernsthatothernations,includingChina,
couldgaininfluence inthinlypopulatedGreenland,giventhe numberof foreignworkersandinvestment that couldcome from Chinese companiesinthe nearfuture because of the law passedDecember 2012.[72] In central Spain,CiudadReal Province,the proposedrare-earthminingproject'Matamulas'mayprovide, accordingto its developers,upto2,100 Tn/year(33% of the annual UE demand).However,thisproject has beensuspendedbyregional authoritiesdue tosocial andenvironmentalconcerns.[73] Addingtopotential mine sites,ASXlistedPeakResourcesannouncedinFebruary2012, that their Tanzanian-basedNguallaprojectcontainednotonlythe 6th largestdepositbytonnage outsideof China, but alsothe highestgrade of rare-earthelementsof the 6.[74] NorthKoreahas beenreportedtohave exportedrare-earthore toChina,aboutUS$1.88 millionworth duringMay and June 2014.[75][76] In May 2012, researchersfromtwouniversitiesinJapanannouncedthattheyhaddiscoveredrare earths inEhime Prefecture,Japan.[77] Malaysianrefiningplans In early2011, AustralianminingcompanyLynaswasreportedtobe "hurryingtofinish"aUS$230 million rare-earthrefineryonthe easterncoastof PeninsularMalaysia'sindustrial portof Kuantan.The plant wouldrefine ore — lanthanidesconcentratefromthe MountWeldmine inAustralia.The ore wouldbe truckedto Fremantle andtransportedbycontainership toKuantan.Withintwoyears,Lynaswassaidto expectthe refinerytobe able tomeetnearlyathirdof the world'sdemandforrare-earthmaterials,not countingChina.[78] The Kuantandevelopmentbroughtrenewedattentiontothe Malaysiantownof BukitMerah inPerak,where a rare-earthmine operatedbyaMitsubishi Chemical subsidiary,AsianRare Earth, closedin1994 and leftcontinuingenvironmentalandhealthconcerns.[79][80] Inmid-2011, after protests,Malaysiangovernmentrestrictionsonthe Lynas plantwere announced.Atthattime,citing subscription-onlyDowJonesNewswire reports,aBarronsreportsaidthe Lynas investmentwas$730 million,andthe projectedshare of the global marketitwouldfill putat"abouta sixth."[81] An independentreviewinitiatedbythe MalaysianGovernment,andconductedbythe InternationalAtomic EnergyAgency(IAEA) in2011 to addressconcernsof radioactive hazards,foundnonon-compliance with international radiationsafetystandards.[82] However,the Malaysian authoritiesconfirmedthatasof October2011, Lynaswas not givenanypermit to importany rare-earthore intoMalaysia.OnFebruary2, 2012, the MalaysianAELB (AtomicEnergy LicensingBoard) recommendedthatLynasbe issuedatemporaryoperatinglicense subjecttomeetinga
numberof conditions.On2 September2014, Lynaswas issueda2-yearfull operatingstage licenseby the AELB.[83] Othersources Mine tailings Significantquantitiesof rare-earthoxidesare foundintailingsaccumulatedfrom50 yearsof uranium ore,shale andloparite miningatSillamäe,Estonia.[84] Due tothe risingpricesof rare earths,extraction of these oxideshasbecome economicallyviable.The countrycurrentlyexportsaround3,000 tonnesper year,representingaround2%of worldproduction.[85] Similarresourcesare suspectedinthe western UnitedStates,where goldrush-eraminesare believedtohave discardedlarge amountsof rare earths, because theyhadno value atthe time.[86] Oceanmining In January2013 a Japanese deep-searesearchvesselobtainedsevendeep-seamudcore samplesfrom the PacificOceanseafloorat5,600 to 5,800 metersdepth,approximately250kilometres(160mi) south of the islandof Minami-Tori-Shima.[87] The researchteamfounda mudlayer2 to 4 metersbeneaththe seabedwithconcentrationsof upto0.66% rare-earthoxides.A potential depositmightcompare in grade withthe ion-absorption-type depositsinsouthernChinathatprovide the bulkof Chinese REO mine production,whichgrade inthe range of 0.05% to 0.5% REO.[88][89] Waste Anotherrecentlydevelopedsource of rare earthsiselectronicwaste andotherwastesthathave significantrare-earthcomponents.[90] Advancesinrecyclingtechnologyhave made extractionof rare earthsfromthese materialslessexpensive.[91] Recyclingplantsoperate inJapan,whereanestimated 300,000 tonsof rare earths are foundinunusedelectronics.[92] InFrance,the Rhodiagroupissetting up twofactories,inLa Rochelle andSaint-Fons,thatwill produce 200tons of rare earthsa yearfrom usedfluorescentlamps,magnetsandbatteries.[93][94] Coal andcoal by-productsare a potential source of critical elementsincludingrare earthelements(REE) withestimatedamountsinthe range of 50 millionmetrictons.[95] Methods One studymixedflyashwithcarbonblackand thensenta 1-secondcurrentpulse throughthe mixture, heatingitto 3,000 °C (5,430 °F).The flyashcontainsmicroscopicbitsof glassthat encapsulate the metals.The heatsshattersthe glass,exposingthe rare earths.Flashheatingalsoconvertsphosphates intooxides,whichare more solubleandextractable.Usinghydrochloricacidat concentrationslessthan 1% of conventional methods,the processextractedtwice asmuchmaterial.[96]
Properties Accordingto chemistryprofessorAndreaSella,rare-earthelementsdifferfromotherelements,inthat whenlookedatanalytically,theyare virtuallyinseparable,havingalmostthe same chemical properties. However,intermsof theirelectronic andmagneticproperties,eachone occupiesaunique technological niche thatnothingelse can.[3] Forexample,"the rare-earthelementspraseodymium(Pr) and neodymium(Nd)canbothbe embeddedinside glassandtheycompletelycutoutthe glare fromthe flame whenone isdoingglass-blowing."[3] Uses Global REE consumption,2015[97] Catalysts,24%(24%) Magnets,23% (23%) Polishing,12%(12%) "other",9%(9%) Metallurgy,8%(8%) Batteries,8%(8%) Glass,7% (7%) Ceramics,6%(6%) Phosphorsandpigments,3%(3%) US consumptionof REE, 2018[98] Catalysts,60%(60%) Ceramicsandglass,15% (15%) Polishing,10%(10%) "other",5%(5%) Metallurgy,10%(10%) The uses,applications,anddemandforrare-earthelementshasexpandedover the years.Globally,most REEs are usedfor catalystsandmagnets.[97] InUSA, more than half of REEs are usedfor catalysts,and ceramics,glassand polishingare alsomainuses.[98]
Otherimportantusesof rare-earthelementsare applicable tothe productionof high-performance magnets,alloys,glasses,andelectronics.Ce andLaare importantas catalysts,andare usedfor petroleumrefiningandasdiesel additives.Ndisimportantinmagnetproductionintraditional andlow- carbon technologies.Rare-earthelementsinthiscategoryare usedinthe electricmotorsof hybridand electricvehicles,generatorsinwindturbines,harddiscdrives,portable electronics,microphones, speakers. Ce,La andNd are importantinalloymaking,andinthe production of fuel cellsandnickel-metal hydride batteries.Ce,Gaand Ndare importantinelectronicsandare usedinthe productionof LCD and plasma screens,fiberoptics,lasers,[99] aswell asin medical imaging.Additionalusesforrare-earthelements are as tracers inmedical applications,fertilizers,andinwatertreatment.[25] REEs have beenusedinagriculture toincrease plantgrowth,productivity,andstressresistance seeminglywithoutnegative effectsforhumanandanimal consumption.REEsare usedin agriculture throughREE-enrichedfertilizerswhichisawidelyusedpractice inChina.[100] Inaddition,REEsare feed additivesforlivestockwhichhasresultedinincreasedproductionsuchaslargeranimalsanda higher productionof eggsand dairyproducts.However,thispractice hasresultedinREEbio-accumulation withinlivestockandhasimpactedvegetationandalgae growthinthese agricultural areas.[101] Additionallywhilenoill effectshave beenobservedatcurrentlow concentrationsthe effects overthe longtermand withaccumulationovertime are unknownpromptingsome callsformore researchinto theirpossible effects.[100][102] Giventhe limitedsupply,industriesdirectlycompete witheachotherforresources,e.g.the electronics sectoris indirectcompetitionwithrenewable energyuse inwindfarms,solarpanelsandbatteries.[103] Environmental considerations REEs are naturallyfoundinverylowconcentrationinthe environment.Minesare oftenincountries where environmental andsocial standardsare verylow,causinghumanrightsviolations,deforestation and contaminationof landandwater.[103][104] Nearminingandindustrial sitesthe concentrationscanrise tomanytimesthe normal background levels.Once inthe environmentREEs can leachintothe soil where theirtransportisdeterminedby numerousfactorssuchas erosion,weathering,pH,precipitation,groundwater,etc.Actingmuchlike metals,theycanspeciate dependingonthe soil conditionbeingeithermotileoradsorbedto soil particles.Dependingontheirbio-availabilityREEscanbe absorbedintoplantsandlaterconsumedby humansand animals.The miningof REEs,use of REE-enrichedfertilizers,andthe productionof phosphorusfertilizersall contributetoREE contamination.[105] Furthermore,strongacidsare used duringthe extractionprocessof REEs,whichcan thenleachoutinto the environmentandbe
transportedthroughwaterbodiesandresultinthe acidificationof aquaticenvironments.Another additive of REEminingthatcontributestoREE environmental contaminationisceriumoxide(CeO 2) whichisproducedduringthe combustionof diesel andisreleasedasanexhaustparticulate matter and contributesheavilytosoil andwatercontamination.[101] False-colorsatellite imageof the BayanOboMiningDistrict,2006 Mining,refining,andrecyclingof rare earthshave seriousenvironmental consequencesif notproperly managed.Low-level radioactivetailingsresultingfromthe occurrence of thoriumanduraniuminrare- earthelementorespresentapotential hazard[106] andimproperhandlingof these substancescan resultinextensive environmental damage.InMay 2010, Chinaannounceda major,five-month crackdownon illegal mininginordertoprotectthe environmentanditsresources.Thiscampaignis expectedtobe concentratedinthe South,[107] where mines –commonlysmall,rural,andillegal operations –are particularlyprone toreleasingtoxicwaste intothe general watersupply.[33][108] However,eventhe majoroperationinBaotou,inInnerMongolia,where muchof the world'srare-earth supplyisrefined,hascausedmajorenvironmental damage.[109] China'sMinistryof Industryand InformationTechnologyestimatedthatcleanupcostsinJiangxi province at$5.5 billion.[104] It ishoweverpossible tofilteroutandrecoverany rare earthelementsthatflow outwiththe wastewaterfromminingfacilities.However,suchfilteringandrecoveryequipmentmaynotalwaysbe presentonthe outletscarryingthe wastewater.[110][111][112] RecyclingandreusingREEs Furtherinformation:CirculareconomyandRenewable energy§Conservationareas,recyclingandrare- earthelements Wiki letterw.svg Thissectionismissinginformationaboutprocessestorecycle/REEsthatare established,demonstrated experimentallyorunderdevelopmentaswell asrelatedpolicies.Please expandthe sectiontoinclude thisinformation.Furtherdetailsmayexistonthe talkpage.(March 2022) Literature publishedin2004 suggeststhat alongwithpreviouslyestablishedpollutionmitigation,amore circularsupplychainwouldhelpmitigate someof the pollutionatthe extractionpoint.Thismeans recyclingandreusingREEsthat are alreadyinuse or reachingthe endof theirlife cycle.[102] A study publishedin2014 suggestsa methodtorecycle REEs fromwaste nickel-metal hydride batteries,the recoveryrate isfoundto be 95.16%.[113] Rare-earthelementscouldalsobe recoveredfromindustrial wasteswithpractical potential toreduce environmental/healthimpactsfrommining,waste-generation and importsif knownandexperimentalprocessesare scaledup.[114][115] A studysuggeststhat "fulfillmentof the circulareconomyapproachcouldreduce upto 200 timesthe impactinthe climate
change category and up to 70 timesthe cost due to the REE mining."[116] Inmost of the reported studiesreviewedbyascientificreview,"secondarywaste issubjectedtochemical andor bioleaching followedbysolventextractionprocessesforcleanseparationof REEs."[117] Impact of REE contamination On vegetation The miningof REEs has causedthe contaminationof soil andwateraroundproductionareas,whichhas impactedvegetationinthese areasbydecreasingchlorophyll productionwhichaffectsphotosynthesis and inhibitsthe growthof the plants.[101] However,the impactof REEcontaminationonvegetationis dependentonthe plantspresentinthe contaminatedenvironment:some plantsretainandabsorbREEs and some don't.Also,the abilityforthe vegetationtointake the REEis dependentonthe type of REE presentinthe soil,hence there are amultitude of factorsthatinfluence thisprocess.[118] Agricultural plantsare the maintype of vegetationaffectedbyREE contaminationinthe environment,the two plantswitha higherchance of absorbingandstoringREEs beingapplesandbeets.[105] Furthermore, there isa possibilitythatREEs can leachout intoaquaticenvironmentsandbe absorbedbyaquatic vegetation,whichcanthenbio-accumulate andpotentiallyenterthe humanfood-chainif livestockor humanschoose to eatthe vegetation.Anexample of thissituationwasthe case of the water hyacinth (Eichhorniacrassipes) inChina,where the waterwascontaminateddue toa REE-enrichedfertilizer beingusedina nearbyagricultural area.The aquaticenvironmentbecame contaminatedwithcerium and resultedinthe waterhyacinthbecomingthree timesmore concentratedinceriumthanits surroundingwater.[118] On humanhealth REEs are a large groupwithmanydifferentpropertiesandlevelsinthe environment.Becauseof this, and limitedresearch,ithasbeendifficulttodetermine safe levelsof exposureforhumans.[119] A numberof studieshave focusedonriskassessmentbasedonroutesof exposure anddivergence from backgroundlevelsrelatedtonearbyagriculture,mining,andindustry.[120][121] Ithas been demonstratedthatnumerousREEshave toxicpropertiesandare presentinthe environmentorinwork places.Exposure tothese canleadto a wide range of negative healthoutcomessuchascancer, respiratoryissues,dental loss,andevendeath.[39] HoweverREEsare numerousandpresentinmany differentformsandat differentlevelsof toxicity,makingitdifficulttogive blanketwarningsoncancer riskand toxicity assome of these are harmlesswhile otherspose arisk.[119][121][120] What toxicityisshownappearstobe at veryhigh levelsof exposurethroughingestionof contaminated foodand water,throughinhalationof dust/smoke particleseitherasan occupational hazardor due to proximitytocontaminatedsitessuchasminesandcities.Therefore,the mainissuesthatthese residents wouldface isbioaccumulationof REEsand the impacton theirrespiratorysystembutoverall,there can be otherpossible shorttermandlong-termhealtheffects.[122][101] Itwas foundthatpeople living nearminesinChinahad manytimesthe levelsof REEsintheirblood,urine,bone andhaircomparedto
controlsfar fromminingsites.Thishigherlevelwasrelatedtothe highlevelsof REEspresentinthe vegetablestheycultivated,the soil,andthe waterfromthe wells,indicatingthatthe highlevelswere causedby the nearbymine.[120][121] While REElevelsvariedbetweenmenandwomen,the group mostat riskwere childrenbecause REEscanimpactthe neurological developmentof children,affecting theirIQ andpotentiallycausingmemoryloss.[123] The rare earth miningandsmeltingprocesscanrelease airborne fluoride whichwill associatewithtotal suspendedparticles(TSP) toformaerosolsthatcanenterhumanrespiratorysystemsandcause damage and respiratorydiseases.ResearchfromBaotou,Chinashowsthatthe fluoride concentrationinairnear REE minesishigherthanthe limitvalue fromWHO,whichcanaffectthe surroundingenvironmentand become a riskto those thatlive or worknearby.[124] Residentsblamedarare-earthrefineryatBukitMerah forbirthdefectsandeightleukemiacaseswithin five yearsina communityof 11,000 — aftermany yearswithno leukemiacases.Sevenof the leukemia victimsdied.OsamuShimizu,adirectorof AsianRare Earth, said"the companymighthave solda few bags of calciumphosphate fertilizerona trial basisas itsoughtto marketbyproducts;calcium phosphate isnotradioactive ordangerous"inreplytoa formerresidentof BukitMerahwhosaidthat "The cows that ate the grass[grownwiththe fertilizer] all died."[125] Malaysia'sSupreme Courtruled on 23 December1993 that there wasno evidence thatthe local chemical jointventure AsianRare Earth was contaminatingthe local environment.[126] On animal health Experimentsexposingratstovariousceriumcompoundshave foundaccumulationprimarilyinthe lungs and liver.Thisresultedinvariousnegative healthoutcomesassociatedwiththose organs.[127] REEs have beenaddedtofeedinlivestocktoincrease theirbodymassandincrease milkproduction.[127] Theyare mostcommonlyusedtoincrease the bodymassof pigs,andit wasdiscoveredthatREEs increase the digestibilityandnutrientuse of pigs'digestive systems.[127] Studiespointtoa dose response whenconsideringtoxicityversuspositive effects.Whilesmall dosesfromthe environmentor withproperadministrationseemtohave noill effects,largerdoseshave beenshowntohave negative effectsspecificallyinthe organswhere theyaccumulate.[127] The processof miningREEsinChinahas resultedinsoil andwatercontaminationincertainareas,whichwhentransportedintoaquaticbodies couldpotentiallybio-accumulatewithinaquaticbiota.Furthermore,insome casesanimalsthatlive in the REE-contaminatedareashave beendiagnosedwithorganorsystemproblems.[101] REEshave been usedinfreshwaterfishfarmingbecauseitprotectsthe fishfrompossible diseases.[127] One main reasonwhytheyhave beenavidlyusedinanimal livestockfeedingisthattheyhave hadbetterresults than inorganiclivestockfeedenhancers.[128] Remediationafterpollution Ambox currentred.svg
Thissectionneedstobe updated.Please helpupdate thisarticletoreflectrecenteventsornewly available information.(May2019) Afterthe 1982 BukitMerah radioactive pollution,the mine inMalaysiahasbeenthe focusof a US$100 millioncleanupthatisproceedingin2011. Afterhavingaccomplishedthe hilltopentombmentof 11,000 truckloadsof radioactivelycontaminatedmaterial,the projectisexpectedtoentail insummer,2011, the removal of "more than 80,000 steel barrelsof radioactive wastetothe hilltoprepository."[80] In May 2011, afterthe FukushimaDaiichi nucleardisaster,widespreadproteststookplace inKuantan overthe Lynas refineryandradioactive waste fromit.The ore tobe processedhasverylow levelsof thorium,andLynas founderandchief executiveNicholasCurtissaid"There isabsolutelynorisktopublic health."T.Jayabalan,a doctorwho sayshe has beenmonitoringandtreatingpatientsaffectedbythe Mitsubishi plant,"iswaryof Lynas'sassurances.The argumentthat low levelsof thoriuminthe ore make it saferdoesn'tmake sense,he says,because radiationexposureiscumulative."[125] Construction of the facilityhasbeenhalteduntilanindependentUnitedNationsIAEA panel investigationis completed,whichisexpectedbythe endof June 2011.[129] New restrictionswere announcedbythe Malaysiangovernmentinlate June.[81] IAEA panel investigationiscompletedandnoconstructionhasbeenhalted.Lynasisonbudgetand on schedule tostartproducing2011. The IAEA reporthas concludedina reportissuedonThursdayJune 2011 saidit didnot findanyinstance of "anynon-compliance withinternational radiationsafety standards"inthe project.[130] If the propersafetystandardsare followed,REEminingisrelativelylow impact.Molycorp(beforegoing bankrupt) oftenexceededenvironmentalregulationstoimprove publicimage.[131] In Greenlandthere isasignificantdispute onwhethertostarta new rare earthmine inKvanefjelddue to environmental concerns.[132] Geo-political considerations A U.S.G.S.graph of global rare-earth-oxideproductiontrends,1956–2008. Global rare-earth-oxideproductiontrends,1956-2008 (USGS) Chinahas officiallycitedresourcedepletionandenvironmental concernsasthe reasonsfora nationwide crackdownon itsrare-earthmineral productionsector.[47] However,non-environmental motiveshave alsobeenimputedtoChina'srare-earthpolicy.[109] AccordingtoThe Economist,"Slashingtheirexports of rare-earthmetals…isall aboutmovingChinese manufacturersupthe supplychain,sotheycansell valuable finishedgoodstothe worldratherthanlowlyraw materials."[133] Furthermore,China currentlyhasan effective monopolyonthe world'sREE Value Chain.[134] (all the refineriesand
processingplantsthattransformthe raw ore intovaluable elements[135]).Inthe wordsof Deng Xiaoping,aChinese politicianfromthe late 1970s to the late 1980s, "The Middle East has oil;we have rare earths...it isof extremelyimportantstrategicsignificance;we mustbe sure tohandle the rare earthissue properlyandmake the fullestuse of ourcountry'sadvantage inrare earth resources."[136] One possible exampleof marketcontrol isthe divisionof General Motorsthatdealswithminiaturized magnetresearch,whichshutdownitsUS office andmoveditsentire staff toChinain2006[137] (China's exportquotaonlyappliestothe metal butnotproducts made fromthese metalssuchasmagnets). It was reported,[138] butofficiallydenied,[139] thatChinainstitutedanexportbanonshipmentsof rare-earthoxides(butnotalloys)toJapanon 22 September2010, in response tothe detainmentof a Chinese fishingboatcaptainbythe Japanese CoastGuard.[140][49] On September2,2010, a few days before the fishingboatincident,The Economistreportedthat"China...inJulyannouncedthe latestina seriesof annual exportreductions,thistime by40% to precisely30,258 tonnes."[141][49] The UnitedStatesDepartmentof Energyinits 2010 Critical MaterialsStrategyreportidentified dysprosiumasthe elementthatwasmostcritical intermsof importreliance.[142] A 2011 report"China'sRare-EarthIndustry",issuedbythe USGeological SurveyandUS Departmentof the Interior,outlinesindustrytrendswithinChinaandexaminesnational policiesthatmayguide the future of the country's production.The reportnotesthatChina'sleadinthe productionof rare-earth mineralshasacceleratedoverthe pasttwodecades.In1990, Chinaaccountedfor only27% of such minerals.In2009, worldproductionwas132,000 metrictons;Chinaproduced129,000 of those tons. Accordingto the report,recentpatternssuggestthatChinawill slow the exportof suchmaterialstothe world:"Owingtothe increase indomesticdemand,the Governmenthasgraduallyreducedthe export quotaduringthe past several years."In2006, Chinaallowed47 domesticrare-earthproducersand tradersand 12 Sino-foreignrare-earthproducerstoexport.Controlshave since tightenedannually;by 2011, only22 domesticrare-earthproducersandtradersand9 Sino-foreignrare-earthproducerswere authorized.The government'sfuture policieswill likelykeepinplace strictcontrols:"Accordingto China'sdraftrare-earthdevelopmentplan,annual rare-earthproductionmaybe limitedtobetween 130,000 and140,000 [metrictons] duringthe periodfrom2009 to 2015. The exportquotafor rare-earth productsmay be about 35,000 [metrictons] andthe Governmentmayallow 20 domesticrare-earth producersandtraders to exportrare earths."[143] The UnitedStatesGeological SurveyisactivelysurveyingsouthernAfghanistan forrare-earthdeposits underthe protectionof UnitedStatesmilitaryforces.Since2009 the USGS has conductedremote sensingsurveysaswell asfieldworktoverifySovietclaimsthatvolcanicrockscontainingrare-earth metalsexistinHelmandProvince nearthe village of Khanashin.The USGSstudyteamhas locateda sizable areaof rocks inthe centerof an extinctvolcanocontaininglightrare-earthelementsincluding
ceriumand neodymium.Ithasmapped1.3 millionmetrictonsof desirable rock,oraboutten yearsof supplyatcurrent demandlevels.The Pentagonhasestimateditsvalue atabout$7.4 billion.[144] It has beenarguedthatthe geopolitical importance of rare earthshasbeenexaggeratedinthe literature on the geopoliticsof renewable energy,underestimatingthe powerof economicincentivesfor expandedproduction.[145][146] Thisespeciallyconcernsneodymium.Due toitsrole inpermanent magnetsusedforwindturbines,ithasbeenarguedthatneodymiumwill be one of the mainobjectsof geopolitical competitioninaworldrunningonrenewable energy.Butthisperspectivehasbeen criticisedforfailingtorecognisethatmostwindturbineshave gearsanddonot use permanent magnets.[146] See also icon Geologyportal Rare-earthmineral Rare-earthmagnet List of elementsfacingshortage Material passport:listsusedmaterialsinproducts Digital ProductPassport:renewedinfunctionof the CircularEconomyActionPlan PensanaSaltEnd References The 1985 International Unionof Pure andAppliedChemistry"RedBook"(p.45) recommendsthat lanthanoidisusedratherthanlanthanide.The ending"-ide"normallyindicatesanegative ion.However, owingtowide currentusage,"lanthanide"isstill allowedandisroughlyanalogoustorare earth element. N. G. ConnellyandT.Damhus,ed.(2005). Nomenclature of InorganicChemistry:IUPAC Recommendations2005 (PDF).WithR. M. Hartshorn and A.T. Hutton. Cambridge:RSCPublishing.ISBN 978-0-85404-438-2. Archivedfromthe original (PDF) onMay27, 2008. RetrievedMarch13, 2012. Professorof ChemistryatUniversityCollegeLondon,AndreaSella,AndreaSella:"Insight:Rare-earth metals"onYouTube,InterviewonTRT World/ Oct 2016, minutes4:40 - ff. T Gray (2007). "LanthanumandCerium".The Elements.BlackDog& Leventhal.pp.118–122. Malhotra, Nemi;Hsu,Hua-Shu;Liang,Sung-Tzu;Roldan,Marri JmelouM.;Lee,Jiann-Shing;Ger,Tzong- Rong; Hsiao,Chung-Der(September16,2020). "An UpdatedReview of ToxicityEffectof the Rare Earth Elements(REEs) onAquaticOrganisms".Animals.10(9):1663. doi:10.3390/ani10091663. ISSN 2076- 2615. PMC 552131. PMID 32947815.
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 1 H He 2 Li Be B C N O F Ne 3 Na Mg Al Si P S Cl Ar 4 K Ca Sc Ti V
Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr 5 Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb
Te I Xe 6 Cs Ba La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Hf Ta W Re Os Ir Pt Au
Hg Tl Pb Bi Po At Rn 7 Fr Ra Ac Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr Rf Db Sg Bh
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Rare.docx

  • 1. Rare-earthelement From Wikipedia,the free encyclopedia Jumpto navigationJumptosearch Rare-earthelements inthe periodictable Hydrogen Helium Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon Potassium Calcium Scandium Titanium Vanadium
  • 5. Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson Rare-earthore (shownwitha19 mm diameterUS1 centcoin forsize comparison) Refinedrare-earthoxidesare heavygrittypowdersusuallybrownorblack,butcan be lightercolorsas shownhere.Legend: gadolinium·praseodymium·cerium samarium· lanthanum neodymium The rare-earthelements(REE),alsocalledthe rare-earthmetalsor(incontext) rare-earthoxides,orthe lanthanides[1] (thoughyttriumandscandiumare usuallyincludedasrare-earths) are asetof 17 nearly- indistinguishable lustroussilvery-whitesoftheavymetals.[2] Scandiumandyttriumare consideredrare- earthelementsbecausetheytendtooccurin the same ore depositsasthe lanthanidesandexhibit similarchemical properties,buthave differentelectronicandmagneticproperties.[3][4] These metalstarnishslowlyinairat room temperature andreactslowlywithcoldwatertoform hydroxides,liberatinghydrogen.Theyreactwithsteamtoformoxides,andat elevatedtemperature (400 °C) ignite spontaneously. These elementsandtheircompoundshave nobiological function.The water-soluble compoundsare mildlytomoderatelytoxic,butthe insolubleonesare not.[5] Compoundscontainingrare earthshave diverseapplicationsinelectricalandelectroniccomponents, lasers,glass,magneticmaterials,andindustrial processes.
  • 6. Despite theirname,rare-earthelementsare relativelyplentiful inEarth'scrust,withceriumbeingthe 25th mostabundantelementat68 parts per million,more abundantthancopper.All isotopesof promethiumare radioactive,anditdoesnotoccur naturallyinthe earth'scrust,exceptfora trace amountgeneratedbyspontaneousfissionof uranium238. Theyare oftenfoundinmineralswith thorium,andlesscommonlyuranium.Because of theirgeochemical properties,rare-earthelementsare typicallydispersedandnotoftenfoundconcentratedinrare-earthminerals.Consequently, economicallyexploitableore depositsare sparse (i.e."rare").[6] The firstrare-earthmineral discovered (1787) was gadolinite,ablackmineral composedof cerium, yttrium, iron,silicon,andotherelements. Thismineral wasextractedfroma mine inthe village of YtterbyinSweden;fourof the rare-earth elementsbearnamesderivedfromthissingle location. Contents 1 List 2 Discoveryandearlyhistory 2.1 Spectroscopicidentification 2.2 Early classification 2.3 Lightversusheavyclassification 3 Origin 4 Geological distribution 4.1 Geochemistryapplications 5 Production 5.1 China 5.2 Outside China 5.3 Othersources 5.4 Methods 6 Properties 7 Uses 8 Environmental considerations 8.1 RecyclingandreusingREEs 8.2 Impact of REE contamination 8.3 Remediationafterpollution
  • 7. 9 Geo-political considerations 10 See also 11 References 12 External links List A table listingthe 17 rare-earthelements,theiratomicnumberandsymbol,the etymologyof their names,andtheirmainuses(see alsoApplicationsof lanthanides) isprovidedhere.Some of the rare- earthelementsare namedafterthe scientistswhodiscoveredthem,orelucidatedtheirelemental properties,andsome afterthe geographical locationswhere discovered. Overviewof rare-earthmetalproperties Z Symbol Name Etymology Selectedapplications Abundance[7][8] (ppm[a]) 21 Sc Scandium fromLatin Scandia(Scandinavia). Lightaluminium-scandium alloysforaerospace components,additiveinmetal-halidelampsandmercury-vaporlamps,[9] radioactive tracingagentinoil refineries 22 39 Y Yttriumafterthe village of Ytterby,Sweden,wherethe firstrare earthore was discovered. Yttriumaluminiumgarnet(YAG) laser,yttriumvanadate (YVO4) ashostfor europiumin televisionredphosphor,YBCOhigh-temperature superconductors,yttria-stabilizedzirconia(YSZ) (used intooth crowns;as refractorymaterial - inmetal alloysusedinjetengines,andcoatingsof enginesand industrial gasturbines;electroceramics - formeasuringoxygenandpHof hot watersolutions,i.e.infuel cells;ceramicelectrolyte - usedinsolidoxide fuel cell;jewelry - foritshardnessandoptical properties; do-it-yourself hightemperature ceramicsandcementsbasedonwater),yttriumirongarnet (YIG) microwave filters,[9] energy-efficientlightbulbs(partof triphosphorwhite phosphorcoatingin fluorescenttubes,CFLsandCCFLs,and yellow phosphorcoatinginwhite LEDs),[10] sparkplugs,gas mantles,additive tosteel,aluminiumandmagnesium alloys,cancertreatments,cameraandrefractive telescope lenses(due tohighrefractive indexandverylow thermal expansion),batterycathodes(LYP) 33 57 La Lanthanum fromthe Greek"lanthanein",meaningtobe hidden. Highrefractive index and alkali-resistantglass,flint,hydrogenstorage,battery-electrodes,cameraandrefractive telescope lenses,fluidcatalyticcrackingcatalystforoil refineries 39 58 Ce Cerium afterthe dwarf planetCeres,namedafterthe Romangoddessof agriculture. Chemical oxidizingagent,polishingpowder,yellow colorsinglassandceramics,catalystforself- cleaningovens,fluidcatalyticcrackingcatalystforoil refineries,ferroceriumflintsforlighters,robust intrinsicallyhydrophobiccoatingsforturbine blades[11]66.5 59 Pr Praseodymium fromthe Greek"prasios",meaningleek-green,and"didymos",meaning twin. Rare-earthmagnets,lasers,core material forcarbonarc lighting,colorantinglassesand
  • 8. enamels,additiveindidymiumglassusedinweldinggoggles,[9] ferroceriumfiresteel (flint) products, single mode fiberoptical amplifiers(asadopantof fluoride glass) 9.2 60 Nd Neodymium fromthe Greek"neos",meaningnew,and"didymos",meaningtwin. Rare-earthmagnets,lasers,violetcolorsinglassand ceramics,didymiumglass,ceramic capacitors,electricmotorsof electricautomobiles 41.5 61 Pm Promethium afterthe Titan Prometheus,whobroughtfire tomortals. Nuclear batteries,luminouspaint 1×10−15 [12][b] 62 Sm Samarium aftermine official,Vasili Samarsky-Bykhovets. Rare-earthmagnets, lasers,neutroncapture,masers,control rodsof nuclearreactors7.05 63 Eu Europium afterthe continentof Europe. Redand blue phosphors,lasers, mercury-vaporlamps,fluorescentlamps,NMRrelaxationagent 2 64 Gd Gadolinium afterJohanGadolin(1760–1852), tohonor hisinvestigationof rare earths. Highrefractive index glassorgarnets,lasers,X-raytubes,Bubble (computer) memories,neutron capture,MRI contrast agent,NMR relaxationagent,magnetostrictive alloyssuchasGalfenol,steel and chromiumalloysadditive,magneticrefrigeration(usingsignificantmagnetocaloriceffect),positron emissiontomographyscintillatordetectors,substrate formagneto-optical films,highperformance high temperature superconductors,ceramicelectrolyte usedinsolidoxide fuel cells,oxygendetectors, possiblyincatalyticconversionof automobile fumes. 6.2 65 Tb Terbium afterthe village of Ytterby,Sweden. Additive inNeodymiumbased magnets,greenphosphors,lasers,fluorescentlamps(aspartof the white tribandphosphorcoating), magnetostrictivealloyssuchasterfenol-D,naval sonarsystems,stabilizerof fuel cells 1.2 66 Dy Dysprosium fromthe Greek"dysprositos",meaninghardtoget. Additive in Neodymiumbasedmagnets,lasers,magnetostrictivealloyssuchasterfenol-D,harddiskdrives 5.2 67 Ho Holmium afterStockholm(inLatin,"Holmia"),nativecityof one of itsdiscoverers. Lasers,wavelengthcalibrationstandardsforoptical spectrophotometers,magnets 1.3 68 Er Erbium afterthe village of Ytterby,Sweden. Infraredlasers,vanadiumsteel,fiber- optictechnology 3.5 69 Tm Thulium afterthe mythological northernlandof Thule. Portable X-ray machines,metal-halidelamps,lasers 0.52 70 Yb Ytterbium afterthe village of Ytterby,Sweden. Infraredlasers,chemical reducingagent,decoyflares,stainlesssteel,stressgauges,nuclearmedicine,monitoringearthquakes 3.2 71 Lu Lutetium afterLutetia,the citythat laterbecame Paris. Positronemission tomography – PET scan detectors,high-refractive-indexglass,lutetiumtantalate hostsforphosphors, catalystusedinrefineries,LEDlightbulb 0.8 Parts permillioninearth'scrust,e.g.Pb=13 ppm No stable isotopesoccurringinnature.
  • 9. A mnemonicforthe namesof the sixth-row elementsinorderis"Latelycollegepartiesneverproduce sexyEuropeangirlsthatdrinkheavilyeventhoughyoulook".[13] Discoveryandearlyhistory Rare earthswere mainlydiscoveredascomponentsof minerals.Ytterbiumwasfoundinthe "ytterbite" (renamedtogadolinitein1800). It wasdiscoveredbyLieutenantCarl Axel Arrheniusin1787 at a quarry inthe village of Ytterby,Sweden.[14] Arrhenius's"ytterbite"reachedJohanGadolin,aRoyal Academyof Turku professor,andhisanalysisyieldedanunknownoxide ("earth"),whichhe calledyttria.Anders Gustav Ekebergisolatedberylliumfromthe gadolinite butfailedtorecognizeotherelementsinthe ore. Afterthisdiscoveryin1794, a mineral fromBastnäsnearRiddarhyttan,Sweden,whichwasbelievedto be an iron–tungstenmineral,wasre-examinedbyJönsJacobBerzeliusandWilhelmHisinger.In1803 theyobtainedawhite oxide andcalleditceria.MartinHeinrichKlaprothindependentlydiscoveredthe same oxide andcalleditochroia. Ittook another30 yearsfor researcherstodeterminethatother elementswere containedinthe twooresceriaand yttria(the similarityof the rare-earthmetals' chemical propertiesmade theirseparationdifficult). In 1839 Carl Gustav Mosander,an assistantof Berzelius,separatedceriabyheatingthe nitrate and dissolvingthe productinnitricacid.He calledthe oxide of the soluble saltlanthana.Ittookhimthree more yearsto separate the lanthanafurtherintodidymiaandpure lanthana.Didymia, althoughnot furtherseparable byMosander'stechniques,wasinfactstill amixture of oxides. In 1842 Mosanderalsoseparatedthe yttriaintothree oxides:pure yttria,terbiaanderbia(all the names are derivedfromthe townname "Ytterby").The earth givingpinksaltshe calledterbium;the one that yieldedyellowperoxide he callederbium. So in1842 the numberof knownrare-earthelementshadreachedsix:yttrium, cerium,lanthanum, didymium,erbiumandterbium. NilsJohanBerlinandMarc Delafontaine triedalsotoseparate the crude yttriaandfoundthe same substancesthatMosanderobtained,butBerlinnamed(1860) the substance givingpinksaltserbium, and Delafontaine namedthe substancewiththe yellow peroxide terbium.Thisconfusionledto several false claimsof newelements,suchasthe mosandriumof J.Lawrence Smith,orthe philippiumand decipiumof Delafontaine.Due tothe difficultyinseparatingthe metals(anddeterminingthe separation iscomplete),the total numberof false discoverieswasdozens,[15][16] withsome puttingthe total numberof discoveriesatoverahundred.[17] Spectroscopicidentification
  • 10. There were nofurtherdiscoveriesfor30 years,and the elementdidymiumwaslistedinthe periodic table of elementswithamolecularmassof 138. In 1879 Delafontaineusedthe new physical processof optical flame spectroscopyandfoundseveral new spectral linesindidymia.Alsoin1879, the new elementsamariumwasisolatedbyPaul Émile Lecoqde Boisbaudranfromthe mineral samarskite. The samaria earthwas furtherseparatedbyLecoqde Boisbaudranin1886, and a similarresultwas obtainedbyJeanCharlesGalissardde Marignacby directisolationfromsamarskite.Theynamedthe elementgadoliniumafterJohanGadolin,anditsoxide wasnamed"gadolinia". Furtherspectroscopicanalysisbetween1886 and 1901 of samaria,yttria,and samarskite byWilliam Crookes,Lecoqde BoisbaudranandEugène-AnatoleDemarçayyieldedseveral new spectroscopiclines that indicatedthe existence of anunknownelement.The fractionalcrystallizationof the oxidesthen yieldedeuropiumin1901. In 1839 the thirdsource for rare earthsbecame available.Thisisamineral similartogadolinite, uranotantalum(nowcalled"samarskite").Thismineral fromMiassinthe southernUral Mountainswas documentedbyGustavRose.The RussianchemistR.Harmannproposedthata new elementhe called "ilmenium"shouldbe presentinthismineral,butlater,ChristianWilhelmBlomstrand,Galissardde Marignac, and HeinrichRose foundonlytantalumandniobium(columbium) init. The exact numberof rare-earthelementsthatexistedwashighlyunclear,andamaximumnumberof 25 was estimated.The use of X-rayspectra(obtainedbyX-raycrystallography)byHenryGwyn Jeffreys Moseleymade itpossible toassignatomicnumberstothe elements.Moseleyfoundthatthe exact numberof lanthanideshadtobe 15, and that element61 hadyet to be discovered. Usingthese factsabout atomicnumbersfromX-raycrystallography, Moseleyalsoshowedthathafnium (element72) wouldnotbe a rare-earthelement.MoseleywaskilledinWorldWar I in1915, years before hafniumwasdiscovered.Hence,the claimof GeorgesUrbainthathe had discoveredelement72 was untrue.Hafniumisan elementthatliesinthe periodictable immediatelybelow zirconium,and hafniumandzirconiumare verysimilarintheirchemical andphysical properties. Duringthe 1940s, FrankSpeddingandothersinthe UnitedStates(duringthe ManhattanProject) developedchemical ion-exchangeproceduresforseparatingandpurifyingthe rare-earthelements.This methodwasfirstappliedtothe actinidesforseparatingplutonium-239andneptuniumfromuranium, thorium,actinium,andthe otheractinidesinthe materials producedinnuclearreactors.Plutonium-239 was verydesirable because itisafissile material.
  • 11. The principal sourcesof rare-earthelementsare the mineralsbastnäsite,monazite,andlopariteandthe lateriticion-adsorptionclays.Despite theirhighrelative abundance,rare-earthmineralsare more difficulttomine andextractthanequivalentsourcesof transitionmetals(dueinpartto theirsimilar chemical properties),makingthe rare-earthelementsrelativelyexpensive.Theirindustrial use wasvery limiteduntilefficientseparationtechniquesweredeveloped,suchasionexchange,fractional crystallizationandliquid–liquidextractionduringthe late 1950s and early1960s.[18] Some ilmeniteconcentratescontainsmall amountsof scandiumandother rare-earthelements,which couldbe analysedbyXRF.[19] Early classification Before the time thation-exchangemethodsandelutionwere available,the separationof the rare earths was primarilyachievedbyrepeatedprecipitationorcrystallization.In those days,the firstseparation was intotwomaingroups,the ceriumearths(scandium, lanthanum, cerium, praseodymium, neodymium, andsamarium) andthe yttriumearths(yttrium,dysprosium,holmium, erbium, thulium, ytterbium,andlutetium).Europium,gadolinium,andterbiumwere eitherconsideredasa separate groupof rare-earthelements(the terbiumgroup),oreuropiumwasincludedinthe ceriumgroup,and gadoliniumandterbiumwereincludedinthe yttriumgroup.The reasonforthisdivisionarose from the difference insolubilityof rare-earthdouble sulfateswithsodiumandpotassium.The sodiumdouble sulfatesof the ceriumgroupare poorlysoluble,those of the terbiumgroupslightly,andthose of the yttriumgroupare verysoluble.[20] Sometimes,the yttriumgroupwasfurthersplitintothe erbium group(dysprosium,holmium,erbium,andthulium)andthe ytterbiumgroup(ytterbiumandlutetium), but todaythe maingroupingisbetweenthe ceriumandthe yttriumgroups.[21] Today,the rare-earth elementsare classifiedaslightorheavyrare-earthelements,ratherthaninceriumandyttriumgroups. Lightversusheavyclassification The classificationof rare-earthelementsisinconsistentbetweenauthors.[22] The mostcommon distinctionbetweenrare-earthelementsismade byatomicnumbers;those withlow atomicnumbers are referredtoas lightrare-earthelements(LREE),those withhighatomicnumbersare the heavyrare- earthelements(HREE),andthose thatfall inbetweenare typicallyreferredtoas the middle rare-earth elements(MREE).[23] Commonly,rare-earthelementswithatomicnumbers57to 61 (lanthanumto promethium) are classifiedaslightandthose withatomicnumbersgreaterthan62[clarificationneeded >62 or >61?] are classifiedasheavy-rare earthelements.[24] Increasingatomicnumbersbetweenlight and heavyrare-earthelementsanddecreasingatomicradii throughoutthe seriescauseschemical variations.[24] Europiumisexemptof thisclassificationasithas twovalence states:Eu2+ and Eu3+.[24] Yttriumis groupedasheavyrare-earthelementdue tochemical similarities.[25] The breakbetweenthe twogroups issometimesputelsewhere,suchasbetweenelements63(europium) and64 (gadolinium).[26] The actual metallicdensitiesof these twogroupsoverlap,withthe "light"group havingdensitiesfrom6.145 (lanthanum) to7.26 (promethium) or7.52 (samarium) g/cc,and the "heavy"
  • 12. groupfrom 6.965 (ytterbium) to9.32 (thulium),aswell asincludingyttriumat4.47. Europiumhas a densityof 5.24. Origin Rare-earthelements,exceptscandium,are heavierthanironandthus are producedbysupernova nucleosynthesisorbythe s-processinasymptoticgiantbranchstars. Innature,spontaneousfissionof uranium-238producestrace amountsof radioactive promethium, butmostpromethiumissynthetically producedinnuclearreactors. Due to theirchemical similarity,the concentrationsof rare earthsinrocks are onlyslowlychangedby geochemical processes,makingtheirproportionsuseful for geochronologyanddatingfossils. Geological distribution Abundance of elementsinEarth'scrust permillionSi atoms(yaxisislogarithmic) As seeninthe chart to the right,rare-earthelementsare foundonearthat similarconcentrationsto manycommon transitionmetals.The mostabundantrare-earthelementiscerium, whichisactuallythe 25th mostabundantelementinEarth'scrust,having68 parts permillion(aboutascommonas copper). The exceptionisthe highlyunstable andradioactivepromethium"rare earth"isquite scarce.The longest-livedisotope of promethiumhasahalf-life of 17.7years,so the elementexistsinnature inonly negligible amounts(approximately572 g in the entire Earth'scrust).[27] Promethiumisone of the two elementsthatdonothave stable (non-radioactive) isotopesandare followedby(i.e.withhigheratomic number) stable elements(the otherbeingtechnetium). The rare-earthelementsare oftenfoundtogether.Duringthe sequentialaccretionof the Earth,the dense rare-earthelementswere incorporatedintothe deeperportionsof the planet.Early differentiationof moltenmaterial largelyincorporatedthe rare-earthsintomantlerocks.[28] The high fieldstrength[clarificationneeded]andlarge ionicradii of rare-earthsmake themincompatible withthe crystal latticesof mostrock-formingminerals,soREE will undergostrongpartitioningintoameltphase if one is present.[28] REEare chemicallyverysimilarandhave alwaysbeendifficulttoseparate,buta gradual decrease inionicradiusfromlightREE (LREE) to heavyREE (HREE),calledlanthanide contraction,can produce a broad separationbetweenlightandheavyREE.The larger ionicradii of LREE make themgenerallymore incompatible thanHREEin rock-formingminerals,andwill partitionmore stronglyintoa meltphase,whileHREEmay prefertoremaininthe crystalline residue,particularlyif it containsHREE-compatible mineralslike garnet.[28][29] The resultisthatall magma formedfrompartial meltingwill alwayshave greaterconcentrationsof LREEthan HREE, and individualmineralsmaybe dominatedbyeitherHREEor LREE, dependingonwhichrange of ionicradii bestfitsthe crystal lattice.[28]
  • 13. Amongthe anhydrousrare-earthphosphates,itisthe tetragonal mineral xenotime thatincorporates yttriumandthe HREE, whereasthe monoclinicmonazite phase incorporatesceriumandthe LREE preferentially.The smallersize of the HREEallowsgreatersolidsolubilityinthe rock-formingminerals that make up Earth's mantle,andthusyttriumand the HREE show lessenrichmentinEarth'scrust relative tochondriticabundance thandoesceriumandthe LREE. Thishas economicconsequences:large ore bodiesof LREE are knownaroundthe worldandare beingexploited.Ore bodiesforHREE are more rare, smaller,andlessconcentrated.Mostof the current supplyof HREE originatesinthe "ion- absorptionclay"oresof SouthernChina.Some versionsprovide concentratescontainingabout65% yttriumoxide,withthe HREEbeingpresentinratiosreflectingthe Oddo–Harkinsrule:even-numbered REE at abundancesof about5% each,and odd-numberedREEat abundancesof about1% each.Similar compositionsare foundinxenotime orgadolinite.[30] Well-knownmineralscontainingyttrium,andotherHREE, include gadolinite,xenotime,samarskite, euxenite,fergusonite,yttrotantalite,yttrotungstite,yttrofluorite(avarietyof fluorite),thalenite, yttrialite.Small amountsoccurinzircon,whichderivesitstypical yellowfluorescence from some of the accompanyingHREE. The zirconiummineral eudialyte,suchasisfoundinsouthernGreenland,contains small butpotentiallyusefulamountsof yttrium.Of the above yttriumminerals,mostplayedapartin providingresearchquantitiesof lanthanidesduringthe discoverydays.Xenotime isoccasionally recoveredasa byproductof heavy-sandprocessing,butisnotas abundantas the similarlyrecovered monazite (whichtypicallycontainsafewpercentof yttrium).UraniumoresfromOntariohave occasionallyyieldedyttriumasabyproduct.[30] Well-knownmineralscontainingcerium,andotherLREE, include bastnäsite,monazite,allanite,loparite, ancylite,parisite,lanthanite,chevkinite,cerite,stillwellite,britholite,fluocerite,andcerianite.Monazite (marine sandsfromBrazil,India,orAustralia;rockfromSouthAfrica),bastnäsite (fromMountainPass rare earthmine,or several localitiesinChina),andloparite (KolaPeninsula,Russia)have beenthe principal oresof ceriumandthe lightlanthanides.[30] Enricheddepositsof rare-earthelementsatthe surface of the Earth, carbonatitesandpegmatites,are relatedtoalkaline plutonism,anuncommonkindof magmatismthatoccursin tectonicsettingswhere there isriftingorthat are near subductionzones.[29] Ina riftsetting,the alkaline magmaisproducedby verysmall degreesof partial melting(<1%) of garnetperidotiteinthe uppermantle (200to 600 km depth).[29] Thismeltbecomesenrichedinincompatibleelements,like the rare-earthelements,by leachingthemoutof the crystalline residue.The resultantmagmarisesasa diapir,ordiatreme,along pre-existingfractures,andcanbe emplaceddeepinthe crust,oreruptedatthe surface.Typical REE enricheddepositstypesforminginriftsettingsare carbonatites,andA- andM-Type granitoids.[28][29] Nearsubductionzones,partial meltingof the subductingplate withinthe asthenosphere (80to200 km depth) producesavolatile-richmagma(highconcentrationsof CO2andwater),withhigh concentrations of alkaline elements,andhighelementmobilitythatthe rare-earthsare stronglypartitionedinto.[28]
  • 14. Thismeltmay alsorise alongpre-existingfractures,andbe emplacedinthe crustabove the subducting slabor eruptedat the surface. REE enricheddepositsformingfromthesemeltsare typicallyS-Type granitoids.[28][29] Alkaline magmasenrichedwithrare-earthelementsincludecarbonatites,peralkalinegranites (pegmatites),andnephelinesyenite.CarbonatitescrystallizefromCO2-richfluids,whichcanbe producedbypartial meltingof hydrous-carbonatedlherzolite toproduce aCO2-richprimarymagma, by fractional crystallizationof analkaline primarymagma,orbyseparationof a CO2-richimmiscible liquid from.[28][29] These liquidsare mostcommonlyforminginassociationwithverydeepPrecambrian Cratons,like the onesfoundinAfricaandthe CanadianShield.[28] Ferrocarbonatitesare the most commontype of carbonatite tobe enrichedinREE, andare oftenemplacedaslate-stage, brecciated pipesatthe core of igneouscomplexes;theyconsistof fine-grainedcalcite andhematite,sometimes withsignificantconcentrationsof ankerite andminorconcentrationsof siderite.[28][29] Large carbonatite depositsenrichedinrare-earthelementsinclude MountWeldinAustralia,ThorLake in Canada,ZandkopsdriftinSouthAfrica,andMountainPassinthe USA.[29] Peralkalinegranites(A-Type granitoids) have veryhighconcentrationsof alkaline elementsandverylow concentrationsof phosphorus;theyare depositedatmoderate depthsinextensionalzones,oftenasigneousring complexes,oras pipes,massivebodies,andlenses.[28][29] These fluidshave verylow viscositiesand highelementmobility,whichallowsforcrystallizationof large grains,despite arelativelyshort crystallizationtimeuponemplacement;theirlarge grainsize iswhythese depositsare commonly referredtoas pegmatites.[29] Economicallyviable pegmatitesare dividedintoLithium-Cesium-Tantalum (LCT) and Niobium-Yttrium-Fluorine(NYF) types;NYFtypesare enrichedinrare-earthminerals. Examplesof rare-earthpegmatitedepositsincludeStrange Lake inCanada,andKhaladean-Buregteyin Mongolia.[29] Nepheline syenite(M-Type granitoids) depositsare 90% feldsparandfeldspathoid minerals,andare depositedinsmall,circularmassifs.Theycontainhighconcentrationsof rare-earth- bearingaccessoryminerals.[28][29] Forthe mostpart these depositsare small butimportantexamples include Illimaussaq-KvanefeldinGreenland,andLovozerainRussia.[29] Rare-earthelementscanalsobe enrichedindepositsbysecondaryalterationeitherbyinteractionswith hydrothermal fluidsormeteoricwaterorbyerosionandtransportof resistate REE-bearingminerals. Argillizationof primarymineralsenrichesinsolubleelementsbyleachingoutsilicaandothersoluble elements,recrystallizingfeldsparintoclaymineralssuchkaolinite,halloysiteandmontmorillonite.In tropical regionswhere precipitationishigh,weatheringformsa thickargillizedregolith,thisprocessis calledsupergeneenrichmentandproduceslaterite deposits;heavyrare-earthelementsare incorporatedintothe residual claybyabsorption.Thiskindof depositisonlyminedforREEinSouthern China,where the majorityof global heavyrare-earthelementproductionoccurs.REE-lateritesdoform elsewhere,includingoverthe carbonatite atMountWeldinAustralia.REEmay alsoby extractedfrom placerdepositsif the sedimentaryparentlithologycontainedREE-bearing,heavyresistateminerals.[29] In 2011, YasuhiroKato, a geologistatthe Universityof Tokyowholedastudyof PacificOceanseabed mud,publishedresultsindicatingthe mudcouldholdrichconcentrationsof rare-earthminerals.The
  • 15. deposits,studiedat78 sites,came from"[h]otplumesfromhydrothermal ventspull[ing] these materials out of seawateranddeposit[ing] themonthe seafloor,bitbybit,overtensof millionsof years.One square patch of metal-richmud2.3 kilometerswide mightcontain enoughrare earthstomeetmostof the global demandfora year,Japanese geologistsreportinNature Geoscience.""Ibelieve thatrare[- ]earthresourcesunderseaare muchmore promisingthanon-landresources,"saidKato. "[C]oncentrationsof rare earths were comparable tothose foundinclaysminedinChina.Some deposits containedtwice asmuchheavyrare earthssuch as dysprosium, acomponentof magnetsinhybridcar motors."[30][31] Geochemistryapplications The applicationof rare-earthelementsto geologyisimportanttounderstandingthe petrological processesof igneous,sedimentaryandmetamorphicrockformation.Ingeochemistry,rare-earth elementscanbe usedtoinferthe petrological mechanismsthathave affectedarockdue to the subtle atomicsize differencesbetweenthe elements,whichcausespreferentialfractionationof some rare earthsrelative toothersdependingonthe processesatwork.[23] In geochemistry,rare-earthelementsare typicallypresentedinnormalized"spider"diagrams,inwhich concentrationof rare-earthelementsare normalizedtoareference standardandare thenexpressedas the logarithmtothe base 10 of the value.Commonly,the rare-earthelementsare normalizedto chondriticmeteorites,asthese are believedtobe the closestrepresentationof unfractionatedsolar systemmaterial.However,othernormalizingstandardscanbe applieddependingonthe purpose of the study.Normalizationtoa standardreference value,especiallyof amaterial believedtobe unfractionated,allowsthe observedabundancestobe comparedtoinitial abundancesof the element.[23] Normalizationalsoremovesthe pronounced'zig-zag'patterncausedbythe differencesin abundance betweenevenandoddatomicnumbers.The trendsthatare observed in"spider"diagrams are typicallyreferredtoas"patterns",whichmaybe diagnosticof petrological processesthathave affectedthe material of interest.[23] The rare-earthelementspatternsobservedinigneousrocksare primarilyafunctionof the chemistryof the source where the rock came from,as well asthe fractionationhistorythe rockhasundergone.[23] Fractionationisinturna functionof the partitioncoefficientsof eachelement.Partitioncoefficientsare responsible forthe fractionation of atrace elements(includingrare-earthelements)intothe liquid phase (the melt/magma) intothe solidphase (the mineral).If anelementpreferentiallyremainsinthe solidphase itistermed‘compatible’,anditpreferentiallypartitionsintothe meltphase itisdescribedas ‘incompatible’.[23] Eachelementhasa differentpartitioncoefficient,andtherefore fractionatesinto solidandliquidphasesdistinctly.These conceptsare alsoapplicabletometamorphicandsedimentary petrology.
  • 16. In igneous rocks,particularlyinfelsicmelts,the followingobservationsapply:anomaliesineuropiumare dominatedbythe crystallizationof feldspars.Hornblende,controlsthe enrichmentof MREE compared to LREE and HREE. Depletionof LREErelative toHREE may be due to the crystallizationof olivine, orthopyroxene,andclinopyroxene.Onthe otherhand,depletionof HREErelative toLREE may be due to the presence of garnet,as garnetpreferentiallyincorporatesHREEintoitscrystal structure.The presence of zirconmayalsocause a similareffect.[23] In sedimentaryrocks,rare-earthelementsinclasticsedimentsare a representationprovenance.The rare-earthelementconcentrationsare nottypicallyaffectedbyseaandriverwaters,asrare-earth elementsare insoluble andthushave verylow concentrationsinthese fluids.Asaresult,whena sedimentistransported,rare-earthelementconcentrationsare unaffectedbythe fluidandinsteadthe rock retainsthe rare-earthelementconcentrationfromitssource.[23] Seaand riverwaterstypicallyhave lowrare-earthelementconcentrations.However,aqueous geochemistryisstillveryimportant.Inoceans,rare-earthelementsreflectinputfromrivers, hydrothermal vents,andaeoliansources;[23] thisisimportantin the investigationof oceanmixingand circulation.[25] Rare-earthelementsare alsouseful fordatingrocks,assome radioactive isotopesdisplaylonghalf-lives. Of particularinterestare the 138La-138Ce, 147Sm-143Nd, and 176Lu-176Hf systems.[25] Production Global production1950–2000 Until 1948, mostof the world'srare earthswere sourcedfromplacersanddepositsinIndiaandBrazil. Throughthe 1950s, SouthAfricawas the world'srare-earthsource,froma monazite-richreef atthe Steenkampskraalmine inWesternCape province.[32] Throughthe 1960s until the 1980s, the Mountain Passrare earth mine inCaliforniamade the UnitedStatesthe leadingproducer.Today,the Indianand SouthAfricandepositsstillproduce some rare-earthconcentrates,but theyare dwarfedbythe scale of Chinese production.In2017, Chinaproduced81% of the world'srare-earthsupply,mostlyinInner Mongolia,[6][33] althoughithadonly36.7% of reserves.Australiawasthe secondandonlyothermajor producerwith15% of worldproduction.[34] All of the world'sheavyrare earths(suchasdysprosium) come from Chinese rare-earthsourcessuchasthe polymetallicBayanObodeposit.[33][35] The Browns Range mine,located160 kmsoutheast of HallsCreekinnorthernWesternAustralia,iscurrentlyunder developmentandispositionedtobecome the firstsignificantdysprosiumproduceroutsideof China.[36]
  • 17. Increaseddemandhasstrainedsupply,andthere isgrowingconcernthatthe worldmay soonface a shortage of the rare earths.[37] In several yearsfrom2009 worldwide demandforrare-earthelementsis expectedtoexceedsupplyby40,000 tonnesannuallyunlessmajornew sourcesare developed.[38] In 2013, itwas statedthat the demandforREEs wouldincrease due tothe dependenceof the EU on these elements,the factthatrare earth elementscannotbe substitutedbyotherelementsandthatREEs have a lowrecyclingrate.Furthermore,due tothe increaseddemandandlow supply,future pricesare expectedtoincrease andthere isa chance that countriesotherthanChinawill openREEmines.[39] REE isincreasingindemanddue tothe fact that theyare essential fornew andinnovative technologythatis beingcreated.These newproductsthatneedREEsto be producedare hightechnologyequipmentsuch as smart phones,digital cameras,computerparts,semiconductors,etc.Inaddition,these elementsare more prevalentinthe followingindustries:renewableenergytechnology,militaryequipment,glass making,andmetallurgy.[40] China See also:Rare earthstrade dispute These concernshave intensifieddue tothe actionsof China,the predominantsupplier.[41] Specifically, Chinahas announcedregulationsonexportsandacrackdownon smuggling.[42] OnSeptember1,2009, Chinaannouncedplanstoreduce itsexportquotato 35,000 tonsper yearin 2010–2015 to conserve scarce resourcesandprotectthe environment.[43] OnOctober19, 2010, ChinaDaily,citinganunnamed Ministryof Commerce official,reportedthatChinawill"furtherreduce quotasforrare[-]earthexports by 30 percentat mostnextyearto protectthe preciousmetalsfromover-exploitation."[44] The governmentinBeijingfurtherincreaseditscontrol byforcingsmaller,independentminerstomerge into state-ownedcorporations orface closure.Atthe endof 2010, Chinaannouncedthatthe firstround of exportquotasin2011 for rare earthswouldbe 14,446 tons,whichwasa 35% decrease fromthe previousfirstroundof quotasin2010.[45] Chinaannouncedfurtherexportquotason 14 July2011 for the secondhalf of the yearwithtotal allocationat30,184 tons withtotal productioncappedat93,800 tonnes.[46] InSeptember2011, Chinaannouncedthe haltinproductionof three of itseightmajorrare- earthmines,responsibleforalmost40%of China'stotal rare-earthproduction.[47] InMarch 2012, the US, EU, andJapan confrontedChinaatWTO about these exportandproductionrestrictions.China respondedwithclaimsthatthe restrictionshadenvironmentalprotectioninmind.[48][49] InAugust 2012, Chinaannouncedafurther20% reductioninproduction.[50] The UnitedStates,Japan,andthe EuropeanUnionfiledajointlawsuitwiththe WorldTrade Organizationin2012 againstChina,arguing that Chinashouldnotbe able to denysuch importantexports.[49] In response tothe openingof newminesinothercountries(LynasinAustraliaandMolycorpinthe UnitedStates),pricesof rare earthsdropped.[51] The price of dysprosiumoxidewas994 USD/kgin 2011, butdroppedto US$265/kg by 2014.[52] On August29, 2014, the WTO ruledthatChinahad brokenfree-tradeagreements,andthe WTO saidin the summaryof keyfindingsthat"the overall effectof the foreignanddomesticrestrictionsisto
  • 18. encourage domesticextractionandsecure preferential use of those materialsbyChinese manufacturers."Chinadeclaredthatitwouldimplementthe rulingonSeptember26,2014, but would needsome time todo so.By January5, 2015, Chinahad liftedall quotasfromthe exportof rare earths, but exportlicenceswill still be required.[53] In 2019, Chinasuppliedbetween85%and 95% of the global demandforthe 17 rare earth powders,half of themsourcedfromMyanmar.[54] Afterthe 2021 militarycoupinthat country,future suppliesof critical oreswere possiblyconstrained.Additionally,itwasspeculatedthatthe PRCcouldagain reduce rare earthexportstocounter-acteconomicsanctionsimposedbythe US and EU countries.Rare earth metalsserve ascrucial materialsforEV-manufacturingandhigh-techmilitaryapplications.[55] Outside China As a resultof the increaseddemandandtighteningrestrictionsonexportsof the metalsfromChina, some countriesare stockpilingrare-earthresources.[56] SearchesforalternativesourcesinAustralia, Brazil, Canada,SouthAfrica,Tanzania,Greenland,andthe UnitedStatesare ongoing.[57] Minesinthese countrieswere closedwhenChinaundercutworldpricesinthe 1990s, and itwill take a few yearsto restartproductionas there are many barrierstoentry.[42] One example isthe MountainPassmine in California,whichannounceditsresumptionof operationsonastart-upbasison August27, 2012.[33][58] OthersignificantsitesunderdevelopmentoutsideChinainclude Steenkampskraalin SouthAfrica,the world's highestgrade rare earthsand thoriummine,whichisgearingtogoback into production.Over80% of the infrastructure isalreadycomplete.[59] Otherminesincludethe Nolans ProjectinCentral Australia,the BokanMountainprojectinAlaska,the remote HoidasLake projectin northernCanada,[60] and the Mount WeldprojectinAustralia.[33][58][61] The HoidasLake projecthas the potential tosupplyabout10% of the $1 billionof REEconsumptionthatoccursin NorthAmerica everyyear.[62] Vietnamsigned anagreementinOctober2010 to supplyJapanwithrare earths[63] from itsnorthwesternLai ChâuProvince.[64] In the US, NioCorpDevelopmentLtdhaslauncheda long-shotefforttosecure $1.1 billion[65] toward openinganiobium,scandium, andtitanium mine atitsElkCreeksite insoutheastNebraska[66] which may be able to produce as muchas 7200 tonnesof ferroniobiumand95 tonnesof scandiumtrioxide annually.[67] Alsounderconsiderationforminingare sitessuchasThor Lake inthe NorthwestTerritories,andvarious locationsinVietnam.[33][38][68] Additionally,in2010, a large depositof rare-earthmineralswas discoveredinKvanefjeldinsouthernGreenland.[69] Pre-feasibilitydrillingatthissite hasconfirmed significantquantitiesof blacklujavrite,whichcontainsabout1% rare-earthoxides(REO).[70] The EuropeanUnionhas urgedGreenlandtorestrictChinese developmentof rare-earthprojectsthere,but as of early2013, the governmentof Greenlandhassaidthatit hasno plansto impose such restrictions.[71] ManyDanishpoliticianshave expressedconcernsthatothernations,includingChina,
  • 19. couldgaininfluence inthinlypopulatedGreenland,giventhe numberof foreignworkersandinvestment that couldcome from Chinese companiesinthe nearfuture because of the law passedDecember 2012.[72] In central Spain,CiudadReal Province,the proposedrare-earthminingproject'Matamulas'mayprovide, accordingto its developers,upto2,100 Tn/year(33% of the annual UE demand).However,thisproject has beensuspendedbyregional authoritiesdue tosocial andenvironmentalconcerns.[73] Addingtopotential mine sites,ASXlistedPeakResourcesannouncedinFebruary2012, that their Tanzanian-basedNguallaprojectcontainednotonlythe 6th largestdepositbytonnage outsideof China, but alsothe highestgrade of rare-earthelementsof the 6.[74] NorthKoreahas beenreportedtohave exportedrare-earthore toChina,aboutUS$1.88 millionworth duringMay and June 2014.[75][76] In May 2012, researchersfromtwouniversitiesinJapanannouncedthattheyhaddiscoveredrare earths inEhime Prefecture,Japan.[77] Malaysianrefiningplans In early2011, AustralianminingcompanyLynaswasreportedtobe "hurryingtofinish"aUS$230 million rare-earthrefineryonthe easterncoastof PeninsularMalaysia'sindustrial portof Kuantan.The plant wouldrefine ore — lanthanidesconcentratefromthe MountWeldmine inAustralia.The ore wouldbe truckedto Fremantle andtransportedbycontainership toKuantan.Withintwoyears,Lynaswassaidto expectthe refinerytobe able tomeetnearlyathirdof the world'sdemandforrare-earthmaterials,not countingChina.[78] The Kuantandevelopmentbroughtrenewedattentiontothe Malaysiantownof BukitMerah inPerak,where a rare-earthmine operatedbyaMitsubishi Chemical subsidiary,AsianRare Earth, closedin1994 and leftcontinuingenvironmentalandhealthconcerns.[79][80] Inmid-2011, after protests,Malaysiangovernmentrestrictionsonthe Lynas plantwere announced.Atthattime,citing subscription-onlyDowJonesNewswire reports,aBarronsreportsaidthe Lynas investmentwas$730 million,andthe projectedshare of the global marketitwouldfill putat"abouta sixth."[81] An independentreviewinitiatedbythe MalaysianGovernment,andconductedbythe InternationalAtomic EnergyAgency(IAEA) in2011 to addressconcernsof radioactive hazards,foundnonon-compliance with international radiationsafetystandards.[82] However,the Malaysian authoritiesconfirmedthatasof October2011, Lynaswas not givenanypermit to importany rare-earthore intoMalaysia.OnFebruary2, 2012, the MalaysianAELB (AtomicEnergy LicensingBoard) recommendedthatLynasbe issuedatemporaryoperatinglicense subjecttomeetinga
  • 20. numberof conditions.On2 September2014, Lynaswas issueda2-yearfull operatingstage licenseby the AELB.[83] Othersources Mine tailings Significantquantitiesof rare-earthoxidesare foundintailingsaccumulatedfrom50 yearsof uranium ore,shale andloparite miningatSillamäe,Estonia.[84] Due tothe risingpricesof rare earths,extraction of these oxideshasbecome economicallyviable.The countrycurrentlyexportsaround3,000 tonnesper year,representingaround2%of worldproduction.[85] Similarresourcesare suspectedinthe western UnitedStates,where goldrush-eraminesare believedtohave discardedlarge amountsof rare earths, because theyhadno value atthe time.[86] Oceanmining In January2013 a Japanese deep-searesearchvesselobtainedsevendeep-seamudcore samplesfrom the PacificOceanseafloorat5,600 to 5,800 metersdepth,approximately250kilometres(160mi) south of the islandof Minami-Tori-Shima.[87] The researchteamfounda mudlayer2 to 4 metersbeneaththe seabedwithconcentrationsof upto0.66% rare-earthoxides.A potential depositmightcompare in grade withthe ion-absorption-type depositsinsouthernChinathatprovide the bulkof Chinese REO mine production,whichgrade inthe range of 0.05% to 0.5% REO.[88][89] Waste Anotherrecentlydevelopedsource of rare earthsiselectronicwaste andotherwastesthathave significantrare-earthcomponents.[90] Advancesinrecyclingtechnologyhave made extractionof rare earthsfromthese materialslessexpensive.[91] Recyclingplantsoperate inJapan,whereanestimated 300,000 tonsof rare earths are foundinunusedelectronics.[92] InFrance,the Rhodiagroupissetting up twofactories,inLa Rochelle andSaint-Fons,thatwill produce 200tons of rare earthsa yearfrom usedfluorescentlamps,magnetsandbatteries.[93][94] Coal andcoal by-productsare a potential source of critical elementsincludingrare earthelements(REE) withestimatedamountsinthe range of 50 millionmetrictons.[95] Methods One studymixedflyashwithcarbonblackand thensenta 1-secondcurrentpulse throughthe mixture, heatingitto 3,000 °C (5,430 °F).The flyashcontainsmicroscopicbitsof glassthat encapsulate the metals.The heatsshattersthe glass,exposingthe rare earths.Flashheatingalsoconvertsphosphates intooxides,whichare more solubleandextractable.Usinghydrochloricacidat concentrationslessthan 1% of conventional methods,the processextractedtwice asmuchmaterial.[96]
  • 21. Properties Accordingto chemistryprofessorAndreaSella,rare-earthelementsdifferfromotherelements,inthat whenlookedatanalytically,theyare virtuallyinseparable,havingalmostthe same chemical properties. However,intermsof theirelectronic andmagneticproperties,eachone occupiesaunique technological niche thatnothingelse can.[3] Forexample,"the rare-earthelementspraseodymium(Pr) and neodymium(Nd)canbothbe embeddedinside glassandtheycompletelycutoutthe glare fromthe flame whenone isdoingglass-blowing."[3] Uses Global REE consumption,2015[97] Catalysts,24%(24%) Magnets,23% (23%) Polishing,12%(12%) "other",9%(9%) Metallurgy,8%(8%) Batteries,8%(8%) Glass,7% (7%) Ceramics,6%(6%) Phosphorsandpigments,3%(3%) US consumptionof REE, 2018[98] Catalysts,60%(60%) Ceramicsandglass,15% (15%) Polishing,10%(10%) "other",5%(5%) Metallurgy,10%(10%) The uses,applications,anddemandforrare-earthelementshasexpandedover the years.Globally,most REEs are usedfor catalystsandmagnets.[97] InUSA, more than half of REEs are usedfor catalysts,and ceramics,glassand polishingare alsomainuses.[98]
  • 22. Otherimportantusesof rare-earthelementsare applicable tothe productionof high-performance magnets,alloys,glasses,andelectronics.Ce andLaare importantas catalysts,andare usedfor petroleumrefiningandasdiesel additives.Ndisimportantinmagnetproductionintraditional andlow- carbon technologies.Rare-earthelementsinthiscategoryare usedinthe electricmotorsof hybridand electricvehicles,generatorsinwindturbines,harddiscdrives,portable electronics,microphones, speakers. Ce,La andNd are importantinalloymaking,andinthe production of fuel cellsandnickel-metal hydride batteries.Ce,Gaand Ndare importantinelectronicsandare usedinthe productionof LCD and plasma screens,fiberoptics,lasers,[99] aswell asin medical imaging.Additionalusesforrare-earthelements are as tracers inmedical applications,fertilizers,andinwatertreatment.[25] REEs have beenusedinagriculture toincrease plantgrowth,productivity,andstressresistance seeminglywithoutnegative effectsforhumanandanimal consumption.REEsare usedin agriculture throughREE-enrichedfertilizerswhichisawidelyusedpractice inChina.[100] Inaddition,REEsare feed additivesforlivestockwhichhasresultedinincreasedproductionsuchaslargeranimalsanda higher productionof eggsand dairyproducts.However,thispractice hasresultedinREEbio-accumulation withinlivestockandhasimpactedvegetationandalgae growthinthese agricultural areas.[101] Additionallywhilenoill effectshave beenobservedatcurrentlow concentrationsthe effects overthe longtermand withaccumulationovertime are unknownpromptingsome callsformore researchinto theirpossible effects.[100][102] Giventhe limitedsupply,industriesdirectlycompete witheachotherforresources,e.g.the electronics sectoris indirectcompetitionwithrenewable energyuse inwindfarms,solarpanelsandbatteries.[103] Environmental considerations REEs are naturallyfoundinverylowconcentrationinthe environment.Minesare oftenincountries where environmental andsocial standardsare verylow,causinghumanrightsviolations,deforestation and contaminationof landandwater.[103][104] Nearminingandindustrial sitesthe concentrationscanrise tomanytimesthe normal background levels.Once inthe environmentREEs can leachintothe soil where theirtransportisdeterminedby numerousfactorssuchas erosion,weathering,pH,precipitation,groundwater,etc.Actingmuchlike metals,theycanspeciate dependingonthe soil conditionbeingeithermotileoradsorbedto soil particles.Dependingontheirbio-availabilityREEscanbe absorbedintoplantsandlaterconsumedby humansand animals.The miningof REEs,use of REE-enrichedfertilizers,andthe productionof phosphorusfertilizersall contributetoREE contamination.[105] Furthermore,strongacidsare used duringthe extractionprocessof REEs,whichcan thenleachoutinto the environmentandbe
  • 23. transportedthroughwaterbodiesandresultinthe acidificationof aquaticenvironments.Another additive of REEminingthatcontributestoREE environmental contaminationisceriumoxide(CeO 2) whichisproducedduringthe combustionof diesel andisreleasedasanexhaustparticulate matter and contributesheavilytosoil andwatercontamination.[101] False-colorsatellite imageof the BayanOboMiningDistrict,2006 Mining,refining,andrecyclingof rare earthshave seriousenvironmental consequencesif notproperly managed.Low-level radioactivetailingsresultingfromthe occurrence of thoriumanduraniuminrare- earthelementorespresentapotential hazard[106] andimproperhandlingof these substancescan resultinextensive environmental damage.InMay 2010, Chinaannounceda major,five-month crackdownon illegal mininginordertoprotectthe environmentanditsresources.Thiscampaignis expectedtobe concentratedinthe South,[107] where mines –commonlysmall,rural,andillegal operations –are particularlyprone toreleasingtoxicwaste intothe general watersupply.[33][108] However,eventhe majoroperationinBaotou,inInnerMongolia,where muchof the world'srare-earth supplyisrefined,hascausedmajorenvironmental damage.[109] China'sMinistryof Industryand InformationTechnologyestimatedthatcleanupcostsinJiangxi province at$5.5 billion.[104] It ishoweverpossible tofilteroutandrecoverany rare earthelementsthatflow outwiththe wastewaterfromminingfacilities.However,suchfilteringandrecoveryequipmentmaynotalwaysbe presentonthe outletscarryingthe wastewater.[110][111][112] RecyclingandreusingREEs Furtherinformation:CirculareconomyandRenewable energy§Conservationareas,recyclingandrare- earthelements Wiki letterw.svg Thissectionismissinginformationaboutprocessestorecycle/REEsthatare established,demonstrated experimentallyorunderdevelopmentaswell asrelatedpolicies.Please expandthe sectiontoinclude thisinformation.Furtherdetailsmayexistonthe talkpage.(March 2022) Literature publishedin2004 suggeststhat alongwithpreviouslyestablishedpollutionmitigation,amore circularsupplychainwouldhelpmitigate someof the pollutionatthe extractionpoint.Thismeans recyclingandreusingREEsthat are alreadyinuse or reachingthe endof theirlife cycle.[102] A study publishedin2014 suggestsa methodtorecycle REEs fromwaste nickel-metal hydride batteries,the recoveryrate isfoundto be 95.16%.[113] Rare-earthelementscouldalsobe recoveredfromindustrial wasteswithpractical potential toreduce environmental/healthimpactsfrommining,waste-generation and importsif knownandexperimentalprocessesare scaledup.[114][115] A studysuggeststhat "fulfillmentof the circulareconomyapproachcouldreduce upto 200 timesthe impactinthe climate
  • 24. change category and up to 70 timesthe cost due to the REE mining."[116] Inmost of the reported studiesreviewedbyascientificreview,"secondarywaste issubjectedtochemical andor bioleaching followedbysolventextractionprocessesforcleanseparationof REEs."[117] Impact of REE contamination On vegetation The miningof REEs has causedthe contaminationof soil andwateraroundproductionareas,whichhas impactedvegetationinthese areasbydecreasingchlorophyll productionwhichaffectsphotosynthesis and inhibitsthe growthof the plants.[101] However,the impactof REEcontaminationonvegetationis dependentonthe plantspresentinthe contaminatedenvironment:some plantsretainandabsorbREEs and some don't.Also,the abilityforthe vegetationtointake the REEis dependentonthe type of REE presentinthe soil,hence there are amultitude of factorsthatinfluence thisprocess.[118] Agricultural plantsare the maintype of vegetationaffectedbyREE contaminationinthe environment,the two plantswitha higherchance of absorbingandstoringREEs beingapplesandbeets.[105] Furthermore, there isa possibilitythatREEs can leachout intoaquaticenvironmentsandbe absorbedbyaquatic vegetation,whichcanthenbio-accumulate andpotentiallyenterthe humanfood-chainif livestockor humanschoose to eatthe vegetation.Anexample of thissituationwasthe case of the water hyacinth (Eichhorniacrassipes) inChina,where the waterwascontaminateddue toa REE-enrichedfertilizer beingusedina nearbyagricultural area.The aquaticenvironmentbecame contaminatedwithcerium and resultedinthe waterhyacinthbecomingthree timesmore concentratedinceriumthanits surroundingwater.[118] On humanhealth REEs are a large groupwithmanydifferentpropertiesandlevelsinthe environment.Becauseof this, and limitedresearch,ithasbeendifficulttodetermine safe levelsof exposureforhumans.[119] A numberof studieshave focusedonriskassessmentbasedonroutesof exposure anddivergence from backgroundlevelsrelatedtonearbyagriculture,mining,andindustry.[120][121] Ithas been demonstratedthatnumerousREEshave toxicpropertiesandare presentinthe environmentorinwork places.Exposure tothese canleadto a wide range of negative healthoutcomessuchascancer, respiratoryissues,dental loss,andevendeath.[39] HoweverREEsare numerousandpresentinmany differentformsandat differentlevelsof toxicity,makingitdifficulttogive blanketwarningsoncancer riskand toxicity assome of these are harmlesswhile otherspose arisk.[119][121][120] What toxicityisshownappearstobe at veryhigh levelsof exposurethroughingestionof contaminated foodand water,throughinhalationof dust/smoke particleseitherasan occupational hazardor due to proximitytocontaminatedsitessuchasminesandcities.Therefore,the mainissuesthatthese residents wouldface isbioaccumulationof REEsand the impacton theirrespiratorysystembutoverall,there can be otherpossible shorttermandlong-termhealtheffects.[122][101] Itwas foundthatpeople living nearminesinChinahad manytimesthe levelsof REEsintheirblood,urine,bone andhaircomparedto
  • 25. controlsfar fromminingsites.Thishigherlevelwasrelatedtothe highlevelsof REEspresentinthe vegetablestheycultivated,the soil,andthe waterfromthe wells,indicatingthatthe highlevelswere causedby the nearbymine.[120][121] While REElevelsvariedbetweenmenandwomen,the group mostat riskwere childrenbecause REEscanimpactthe neurological developmentof children,affecting theirIQ andpotentiallycausingmemoryloss.[123] The rare earth miningandsmeltingprocesscanrelease airborne fluoride whichwill associatewithtotal suspendedparticles(TSP) toformaerosolsthatcanenterhumanrespiratorysystemsandcause damage and respiratorydiseases.ResearchfromBaotou,Chinashowsthatthe fluoride concentrationinairnear REE minesishigherthanthe limitvalue fromWHO,whichcanaffectthe surroundingenvironmentand become a riskto those thatlive or worknearby.[124] Residentsblamedarare-earthrefineryatBukitMerah forbirthdefectsandeightleukemiacaseswithin five yearsina communityof 11,000 — aftermany yearswithno leukemiacases.Sevenof the leukemia victimsdied.OsamuShimizu,adirectorof AsianRare Earth, said"the companymighthave solda few bags of calciumphosphate fertilizerona trial basisas itsoughtto marketbyproducts;calcium phosphate isnotradioactive ordangerous"inreplytoa formerresidentof BukitMerahwhosaidthat "The cows that ate the grass[grownwiththe fertilizer] all died."[125] Malaysia'sSupreme Courtruled on 23 December1993 that there wasno evidence thatthe local chemical jointventure AsianRare Earth was contaminatingthe local environment.[126] On animal health Experimentsexposingratstovariousceriumcompoundshave foundaccumulationprimarilyinthe lungs and liver.Thisresultedinvariousnegative healthoutcomesassociatedwiththose organs.[127] REEs have beenaddedtofeedinlivestocktoincrease theirbodymassandincrease milkproduction.[127] Theyare mostcommonlyusedtoincrease the bodymassof pigs,andit wasdiscoveredthatREEs increase the digestibilityandnutrientuse of pigs'digestive systems.[127] Studiespointtoa dose response whenconsideringtoxicityversuspositive effects.Whilesmall dosesfromthe environmentor withproperadministrationseemtohave noill effects,largerdoseshave beenshowntohave negative effectsspecificallyinthe organswhere theyaccumulate.[127] The processof miningREEsinChinahas resultedinsoil andwatercontaminationincertainareas,whichwhentransportedintoaquaticbodies couldpotentiallybio-accumulatewithinaquaticbiota.Furthermore,insome casesanimalsthatlive in the REE-contaminatedareashave beendiagnosedwithorganorsystemproblems.[101] REEshave been usedinfreshwaterfishfarmingbecauseitprotectsthe fishfrompossible diseases.[127] One main reasonwhytheyhave beenavidlyusedinanimal livestockfeedingisthattheyhave hadbetterresults than inorganiclivestockfeedenhancers.[128] Remediationafterpollution Ambox currentred.svg
  • 26. Thissectionneedstobe updated.Please helpupdate thisarticletoreflectrecenteventsornewly available information.(May2019) Afterthe 1982 BukitMerah radioactive pollution,the mine inMalaysiahasbeenthe focusof a US$100 millioncleanupthatisproceedingin2011. Afterhavingaccomplishedthe hilltopentombmentof 11,000 truckloadsof radioactivelycontaminatedmaterial,the projectisexpectedtoentail insummer,2011, the removal of "more than 80,000 steel barrelsof radioactive wastetothe hilltoprepository."[80] In May 2011, afterthe FukushimaDaiichi nucleardisaster,widespreadproteststookplace inKuantan overthe Lynas refineryandradioactive waste fromit.The ore tobe processedhasverylow levelsof thorium,andLynas founderandchief executiveNicholasCurtissaid"There isabsolutelynorisktopublic health."T.Jayabalan,a doctorwho sayshe has beenmonitoringandtreatingpatientsaffectedbythe Mitsubishi plant,"iswaryof Lynas'sassurances.The argumentthat low levelsof thoriuminthe ore make it saferdoesn'tmake sense,he says,because radiationexposureiscumulative."[125] Construction of the facilityhasbeenhalteduntilanindependentUnitedNationsIAEA panel investigationis completed,whichisexpectedbythe endof June 2011.[129] New restrictionswere announcedbythe Malaysiangovernmentinlate June.[81] IAEA panel investigationiscompletedandnoconstructionhasbeenhalted.Lynasisonbudgetand on schedule tostartproducing2011. The IAEA reporthas concludedina reportissuedonThursdayJune 2011 saidit didnot findanyinstance of "anynon-compliance withinternational radiationsafety standards"inthe project.[130] If the propersafetystandardsare followed,REEminingisrelativelylow impact.Molycorp(beforegoing bankrupt) oftenexceededenvironmentalregulationstoimprove publicimage.[131] In Greenlandthere isasignificantdispute onwhethertostarta new rare earthmine inKvanefjelddue to environmental concerns.[132] Geo-political considerations A U.S.G.S.graph of global rare-earth-oxideproductiontrends,1956–2008. Global rare-earth-oxideproductiontrends,1956-2008 (USGS) Chinahas officiallycitedresourcedepletionandenvironmental concernsasthe reasonsfora nationwide crackdownon itsrare-earthmineral productionsector.[47] However,non-environmental motiveshave alsobeenimputedtoChina'srare-earthpolicy.[109] AccordingtoThe Economist,"Slashingtheirexports of rare-earthmetals…isall aboutmovingChinese manufacturersupthe supplychain,sotheycansell valuable finishedgoodstothe worldratherthanlowlyraw materials."[133] Furthermore,China currentlyhasan effective monopolyonthe world'sREE Value Chain.[134] (all the refineriesand
  • 27. processingplantsthattransformthe raw ore intovaluable elements[135]).Inthe wordsof Deng Xiaoping,aChinese politicianfromthe late 1970s to the late 1980s, "The Middle East has oil;we have rare earths...it isof extremelyimportantstrategicsignificance;we mustbe sure tohandle the rare earthissue properlyandmake the fullestuse of ourcountry'sadvantage inrare earth resources."[136] One possible exampleof marketcontrol isthe divisionof General Motorsthatdealswithminiaturized magnetresearch,whichshutdownitsUS office andmoveditsentire staff toChinain2006[137] (China's exportquotaonlyappliestothe metal butnotproducts made fromthese metalssuchasmagnets). It was reported,[138] butofficiallydenied,[139] thatChinainstitutedanexportbanonshipmentsof rare-earthoxides(butnotalloys)toJapanon 22 September2010, in response tothe detainmentof a Chinese fishingboatcaptainbythe Japanese CoastGuard.[140][49] On September2,2010, a few days before the fishingboatincident,The Economistreportedthat"China...inJulyannouncedthe latestina seriesof annual exportreductions,thistime by40% to precisely30,258 tonnes."[141][49] The UnitedStatesDepartmentof Energyinits 2010 Critical MaterialsStrategyreportidentified dysprosiumasthe elementthatwasmostcritical intermsof importreliance.[142] A 2011 report"China'sRare-EarthIndustry",issuedbythe USGeological SurveyandUS Departmentof the Interior,outlinesindustrytrendswithinChinaandexaminesnational policiesthatmayguide the future of the country's production.The reportnotesthatChina'sleadinthe productionof rare-earth mineralshasacceleratedoverthe pasttwodecades.In1990, Chinaaccountedfor only27% of such minerals.In2009, worldproductionwas132,000 metrictons;Chinaproduced129,000 of those tons. Accordingto the report,recentpatternssuggestthatChinawill slow the exportof suchmaterialstothe world:"Owingtothe increase indomesticdemand,the Governmenthasgraduallyreducedthe export quotaduringthe past several years."In2006, Chinaallowed47 domesticrare-earthproducersand tradersand 12 Sino-foreignrare-earthproducerstoexport.Controlshave since tightenedannually;by 2011, only22 domesticrare-earthproducersandtradersand9 Sino-foreignrare-earthproducerswere authorized.The government'sfuture policieswill likelykeepinplace strictcontrols:"Accordingto China'sdraftrare-earthdevelopmentplan,annual rare-earthproductionmaybe limitedtobetween 130,000 and140,000 [metrictons] duringthe periodfrom2009 to 2015. The exportquotafor rare-earth productsmay be about 35,000 [metrictons] andthe Governmentmayallow 20 domesticrare-earth producersandtraders to exportrare earths."[143] The UnitedStatesGeological SurveyisactivelysurveyingsouthernAfghanistan forrare-earthdeposits underthe protectionof UnitedStatesmilitaryforces.Since2009 the USGS has conductedremote sensingsurveysaswell asfieldworktoverifySovietclaimsthatvolcanicrockscontainingrare-earth metalsexistinHelmandProvince nearthe village of Khanashin.The USGSstudyteamhas locateda sizable areaof rocks inthe centerof an extinctvolcanocontaininglightrare-earthelementsincluding
  • 28. ceriumand neodymium.Ithasmapped1.3 millionmetrictonsof desirable rock,oraboutten yearsof supplyatcurrent demandlevels.The Pentagonhasestimateditsvalue atabout$7.4 billion.[144] It has beenarguedthatthe geopolitical importance of rare earthshasbeenexaggeratedinthe literature on the geopoliticsof renewable energy,underestimatingthe powerof economicincentivesfor expandedproduction.[145][146] Thisespeciallyconcernsneodymium.Due toitsrole inpermanent magnetsusedforwindturbines,ithasbeenarguedthatneodymiumwill be one of the mainobjectsof geopolitical competitioninaworldrunningonrenewable energy.Butthisperspectivehasbeen criticisedforfailingtorecognisethatmostwindturbineshave gearsanddonot use permanent magnets.[146] See also icon Geologyportal Rare-earthmineral Rare-earthmagnet List of elementsfacingshortage Material passport:listsusedmaterialsinproducts Digital ProductPassport:renewedinfunctionof the CircularEconomyActionPlan PensanaSaltEnd References The 1985 International Unionof Pure andAppliedChemistry"RedBook"(p.45) recommendsthat lanthanoidisusedratherthanlanthanide.The ending"-ide"normallyindicatesanegative ion.However, owingtowide currentusage,"lanthanide"isstill allowedandisroughlyanalogoustorare earth element. N. G. ConnellyandT.Damhus,ed.(2005). Nomenclature of InorganicChemistry:IUPAC Recommendations2005 (PDF).WithR. M. Hartshorn and A.T. Hutton. Cambridge:RSCPublishing.ISBN 978-0-85404-438-2. Archivedfromthe original (PDF) onMay27, 2008. RetrievedMarch13, 2012. Professorof ChemistryatUniversityCollegeLondon,AndreaSella,AndreaSella:"Insight:Rare-earth metals"onYouTube,InterviewonTRT World/ Oct 2016, minutes4:40 - ff. T Gray (2007). "LanthanumandCerium".The Elements.BlackDog& Leventhal.pp.118–122. Malhotra, Nemi;Hsu,Hua-Shu;Liang,Sung-Tzu;Roldan,Marri JmelouM.;Lee,Jiann-Shing;Ger,Tzong- Rong; Hsiao,Chung-Der(September16,2020). "An UpdatedReview of ToxicityEffectof the Rare Earth Elements(REEs) onAquaticOrganisms".Animals.10(9):1663. doi:10.3390/ani10091663. ISSN 2076- 2615. PMC 552131. PMID 32947815.
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