Mineral Profiles | Niobium-Tantalum
MineralsUK Mineral profile Centre for sustainable mineral development per cent isotope urally-occurring niobiumconsistsalmostexclusivelyofthe Niobium isashiny, ductilemetalwithawhitelustre.Nat Anders Ekeberg. Tantalum wasdiscoveredin1802byaSwedishscientist, some time,before‘niobium’wasfinallyacceptedin1949. it ‘niobium’.Thenameswereusedinterchangeablyfor nised byaGermanchemist,HeinrichRose,whonamed named ‘columbium’;itwassubsequentlyalsorecog discovered in1801byCharlesHatchett,andwasoriginally thus commonlygroupedtogether(Table 1).Niobiumwas very similarphysicalandchemicalproperties,are Niobium (Nb)andtantalum(Ta) aretransitionmetalswith Definitions andcharacteristics deposits Definitions, mineralogyand economically importantspecies areoxides. typically havelowconcentrations.Thevastmajorityofthe for majorionsinanumberofotherminerals,whichthey are relativelyrare.Niobiumandtantalumalsosubstitute minerals; silicatesofniobiumandtantalumdoexist,but mineral species(Table 2).The majorityoftheseareoxide metals, butareessentialcomponentsinarangeof Niobium andtantalumdonotoccurnaturallyasfree Mineralogy are typicallydepletedinbothniobiumandtantalum. subduction zones,andthatmagmasformedinthissetting continental crustwasformedatconvergentmarginsabove crust. Thiscanbeattributedtothefactthatmuchof bium andtantalumareratherdepletedinthecontinental other metallicelementssuchasthelightrareearths,nio tantalum of0.7ppm(RudnickandGao,2004).Comparedto having anabundanceofeightpartspermillion(ppm)and average continentalcrustarerelativelylow, niobium The overallabundancesofniobiumandtantaluminthe both elementshavebeensynthesised. BGS ©NERC2011. Allrightsreserved. contained inthisreportarevested inNERC. Unless otherwisestated,copyright ofmaterials 93 180 Nb; naturaltantalumismainly Ta. Anumberofotherradioactiveisotopes Niobium–tantalum 181 Ta, with0.012
- - - Lavinsky, iRocks.com (http://www.irocks.com/) –CC-BY-SA-3.0.iRocks.com Lavinsky, licence (accessed25/03/2011 atwww.commons.wikimedia.org). Attribution:Rob 1 Table 1 Figure 1 found asaprimarymineralinalkalineigneousrocks. rich inbothniobiumandtantalum.Pyrochloreistypically has awidecompositionalrange,includingsomespecies economic importance,particularlyforniobium.Thisgroup tantalum. Thepyrochloregroup(Figure2)isofgreat minerals. Wodginite isalsoan important sourceof most commongroupoftantalum-andniobium-bearing The columbite-tantalitemineralgroup(Figure1)isthe
(g/cm Density at293K Atomic weight Atomic number Crystal structure ohm-metres) resistivity (nano Electrical MPa Vickers hardness Boiling point°C Melting point°C Image takenbyRob Lavinsky. Permissiontousegiven byacreativecommons 3 ) Selected propertiesofniobiumandtantalum. Dark colouredtantalitewithpale colouredalbite Niobium (Nb) Body centred 152 at0°C 92.90638 8.581 cubic 1320 4930 2468 41 Tantalum (Ta) Body centred 131 at20°C 180.9479 16.677 cubic 5425 2996 873 73 April 2011 1 . 2 Niobium–tantalum Lavinsky, iRocks.com (http://www.irocks.com/) – CC-BY-SA-3.0.iRocks.com Lavinsky, licence (accessed25/03/2011 atwww.commons.wikimedia.org). Table 2 2 Figure 2 (Na those foundinalkalineigneous rockssuchaseudialyte as substitutesinarangeofsilicate minerals,typically economic interest.Similarly, niobiumandtantalumoccur these mineralsarerarelyhighenoughtomakethemof rutile, andilmenite.Contentsofniobiumtantalumin ions insomecommonoxidegroupssuchascassiterite, group. Niobiumandtantalumalsosubstituteformajor include tapiolite,ixiolite,andmineralsoftheperovskite Other, lesscommonoxidesofniobiumandtantalum
Columbite Mineral name Euxenite Ilmenorutile Struverite Loparite Wodginite Ixiolite Lueshite Pyrochlore Tantalite Microlite Tapiolite Image takenbyRob Lavinsky. Permissiontousegiven byacreativecommons 4 (Ca,Ce) Selected niobiumandtantalummineralsindicativecontents ofNb Pyrochlore. Source:RobLavinsky(iRocks.com) 2 (Fe ++ ,Mn,Y)ZrSi Columbite-tantalite Mineral group Euxenite Rutile Rutile Perovskite Wodginite Ixiolite Perovskite Pyrochlore Columbite-tantalite Pyrochlore Tapiolite 8 O 22 (OH,Cl) 2 ). Attribution: Rob (Fe,Mn)(Nb,Ta) Formula (Y, Ca,Ce,U,Th)(Nb,Ti, Ta) Fe (Ti,Ta,Fe)O (Ce,La,Na,Ca,Sr)(Ti,Nb)O (Ta,Nb,Sn,Mn,Fe)O (Ta,Nb,Sn,Mn,Fe) NaNbO (Na,Ca) (Fe,Mn)(Ta,Nb) (Na,Ca) (Fe,Mn) (Ta,Nb) x (Nb,Ta) 2 . 2 2 3 Ta Nb 2x 2 2 2 O 4Ti carbonate minerals. potassium- and/orsodium-rich mineralalkalifeldspar. rock (magma). monly associatedwithigneousrocks Niobium andtantalummineraldepositsaremostcom Deposits 6 5 4 3 not known. the categoriesgivenabove,buteconomicexamplesare found insomegranitesandpegmatitesthatdonotfallinto Moderately highcontentsofniobiumandtantalummaybe 3. 2. 1. with whichtheyareassociated(Küster, 2009): into threemaintypes,onthebasisofigneousrocks Primary NiobiumandTantalum depositscanbedivided descriptions below. sources, andsotheyarenotconsideredseparatelyinthe occur inrelativelycloseassociationwiththeirprimary end ofthissection).Ingeneral,thesesecondarydeposits processes, arealsoknown(seeTable 3andFigureatthe have beenconcentratedbyweatheringandsedimentary deposits, whereniobium-andtantalum-bearingminerals pegmatites O
6 Carbonatites: igneous rocksconsistingofmorethan50percent primary Syenites: coarse-grainedigneousrocksthat arecomposedlargelyofthe Pegmatites: verycoarse-grainedigneous rocks. Igneous rocks:rockswithacrystallinetexture thatcrystallisedfrommolten 6 (O,OH,F) (O,OH,F) 2005). in lithium(Li),caesium(Cs),tantalum)(C Granites andpegmatitesoftheLCTfamily(enriched Alkaline toperalkalinegranitesandsyenites Carbonatites andassociatedrocks 1-x 2 2 2 O O O O 6 6 4 6 2 O 2 8 4 , syenites 3 2 O 6 2 O 5 andTa 5 andcarbonatites 2 O www.MineralsUK.com 5 Nb . 11.32 47.43 81.09 16.15 78.72 75.12 27.9 8.37 8.30 1.33 2 n.a. n.a. O 5 3 (%) , includinggranites, 6 . Somesecondary ˇ erný andErcit, Ta 37.65 22.53 69.58 68.96 83.96 86.17 83.53 2 n.a. n.a. n.a. n.a. n.a. O 5 (%) - 3 Niobium–tantalum magmatic differentiation rarely upto1.0percent),butnotore-grade.However, bodies aremoderatelyhigh(commonly0.01–0.1percent, In general,bulkrockniobiumcontentsforcarbonatite niobium-rich silicatessuchastitanite(Mitchell,2005). the perovskiteandpyrochloremineralgroups,aswell bearing mineralsfoundincarbonatitesincludemembersof high tantalumcontents(Möller, 1989).Common niobium- rich melts,andsocarbonatitesdonotgenerallyhave preferentially enrichedovertantalumincarbondioxide- zirconium (Zr),uranium(U)andthorium(Th).Niobiumis strontium (Sr),fluorine(F),phosphorus(P),niobium(Nb), including therareearthelements(REE),barium(Ba), Carbonatites aretypicallyenrichedinarangeofelements, and water-rich fluidsratherthanmagmas. surface. are concentratedeither inthecrystallinerockorresidual moltenmagma. rock bytheactionoffluids. rich inmagnesiumand/oriron. magnesium and/oriron. silica contents. rarely occurringaslargeplutonsorextrusive small plugs(lessthanonekilometreindiameter),more Carbonatites aremostcommonlyfoundasdykes,sillsand directly fromthemantlewithverylittlecrustalinfluence. contain certaincharacteristicminerals. Earth’s surface. occurring atthepresentdayinEastAfrica. rifting exclusively foundinareasofcontinentalextensionand 50 percentprimarycarbonateminerals.Theyarealmost Carbonatites areigneousrocksthatconsistofmorethan Carbonatites andassociatedrocks 16 15 14 13 12 11 10 9 8 7 rocks, ormafic rounded byametasomatised and Kjarsgaard,2008).Manycarbonatitebodiesaresur commonly associatedwithalkaline sequences. Theyrarelyoccurinisolation,beingmore carbohydrothermal carbonatite. Somecarbonatitebodiesareconsideredtobe alteration ofthecountryrocksbyfluidsderivedfrom rich insodium(Na)and/orpotassium(K),formedthrough pyrochlore. Weathering processes tling mayconcentrateniobium-bearingmineralssuchas nepheline syeniteandotherfeldspathoid-bearing
Alkaline rocks:igneousrocksthatarerichinsodiumandpotassium, Extrusive: extrusivevolcanicrocksareformedbyeruptionofmagmaontothe Continental rifting:thegradualbreak-upofacontinentunderextension,asis Weathering processes:processesbywhichrocksare alteredattheearth’s Magmatic differentiation:processesbywhich certainelementsorminerals Carbohydrothermal: formedfromhotcarbon dioxide-richandwater-rich fluids. Metasomatised: havingundergonemetasomatism, chemicalalterationofa Ultramafic: arockalmostentirelymade up ofdark-colouredmineralsthatare Mafic rock:arockcontainingabundantdark-colouredmineralsthatarerichin Feldspathoids: agroupoflight-colouredmineralsthathaverelativelylow 7 , andtheirsourcemagmasarethoughttobederived 11 toultramafic 14
— formed fromcarbondioxide-rich 15 processessuchascrystalset- 13 12 or‘fenitised’zone,typically alkalinerocks(Woolley 16 9 mayalsoconcentrate silicaterocks,either 8 volcanic 10 igneous - cite carbonatite,glimmerite dominated bydolomitecarbonatitewithsubordinatecal ometre indiameter(NasraouiandWaerenborgh, 2001), Complex, aroughlycircularintrusionapproximately4.5 kil The AraxádepositlieswithintheBarreiroCarbonatite both deposits,pyrochloreisthemainniobiumoremineral. phoscorite in ratherunusualintrusionsconsistingofcarbonatite-and operated byAngloAmerican.Thesedepositsarehosted (CBMM). Asecondmajorniobiummine,atCatalão,is by theCompanhiaBrasileiradeMetalurgiaeMineraçao niobium depositisatAraxá,andownedexploited been alteredbytheeffects ofincreasedtemperature,pressure orfluidflow. resulting fromweathering undertropicalconditions. biotite orphlogopite.Canalsobecalled biotitite orphlogopititeasappropriate. carbonatites. ago. ultramafic-carbonatite complexesoftheLateCretaceous zil, wherethemainniobiumdepositsoccurinalkaline Much oftheworld’s niobiumsupplycomesfromBra- mineralisation. thermal activity, areathirdpotentialsourceof niobium and areasofmetasomatism,formedthroughcarbohydro these mineralsintheshallowsubsurface.Late-stageveins 22 21 20 19 18 17 Niobec mineinQuebec,Canada,operatedbytheIamgold The largestactiveniobiummineoutsideBrazilisthe centre ofthecomplex. mined depositisintheweatheredlateriticzoneabove tre ofthecomplex(Cordeiroetal.,2010).AsatAraxá, rocks thatbecomeincreasinglycommontowardsthecen and plugsofdolomite-carbonatitephoscorite-series (phlogopitite) atthemarginsofcomplex,withsheets six kilometresatthesurface.Itisdominatedbyglimmerite ed, zonedintrusivebodywithadiameterofapproximately in thenearbyCatalãoIIcomplex.Iisasteep-sid alkaline-carbonatite complex,butasimilardepositoccurs The mainworkeddepositatCatalãoisintheI to 2.5kilometrewide(NasraouiandWaerenborgh, 2001). carbonatite havebeenmetasomatisedinanaureole exploited byopen-pitmining.Thecountryrockstothe mean gradeof2.5percentniobiumoxide,andwhichis which pyrochlorehasbecomeconcentratedatareported zoic Alto Paranaibaigneousprovince,intrudedintoNeoprotero conditions toformathick(>200metres),lateritic part oftheintrusionhasbeenweatheredundertropical
Aureole: anareaaround abodyofigneousrockinwhichthe host rockshave Lateritic: relatingtolaterite,aresidualdeposit richinironandaluminium Glimmerite: Anultramaficrockconsisting almostentirelyofmica,either Phoscorite: Amagnetite,olivine,apatite rock, usuallyassociatedwith Neoproterozoic: aunitofgeologicaltimebetween1000to542millionyears Late Cretaceous:aunitofgeologicaltimebetween99to65millionyearsago. 18 metasedimentaryrocks.Thelargestcurrentlyworked 19 -series rockswithnoassociatedsyenites.In 20 andphoscorite.Thecentral www.MineralsUK.com 21 coverin 22 up - - - 17 - -
- 4 Niobium–tantalum by riversand/orcoastal processes. usually cylindricalwithsteepmargins. entirely coveredbyPalaeozoic surrounded byaringofsyenitesanddiorites,isalmost ferrocarbonatite (Belzile,2009).Thecarbonatitebodyis from calcitecarbonatitethroughdolomiteto of crescenticlensescarbonatite,younginginwards kilometres acrossatthesurface.Itconsistsofaseries which hasanellipticalshapeandisapproximatelyfour Neoproterozoic-age Saint-Honorécarbonatitecomplex, Corporation. Thismineliesinthesouthernpartof 26 25 24 23 ancient lake,associatedwithPermian upper orehorizonisaburiedplacerdeposit ered andalteredtoptothecarbonatitebody, whilstthe which isupto300metresthick,representstheweath concentrated intwoorehorizons.Thelowerhorizon, seminated throughoutthecarbonatite,butisparticularly tres (KravchenkoandPokrovsky, 1995).Pyrochloreisdis- having asurfaceareaofapproximately12squarekilome its mayremaintobefound.The smallerdepositsinclude published work(Bergeretal.,2009)andothersuchdepos- rare earthelementmineraldepositshavebeenrecordedin A totalof58carbonatitebodiescontainingniobiumand with 2897milliontonnesniobium(Pollard,1995). represent thelargestsingleniobiumdepositinworld its ageisuncertain(Bergeretal.,2009),butitthoughtto Seis Lagosdepositispoorlyknown,totheextentthateven niobium (KravchenkoandPokrovsky, 1995).TheMorrodos The upperorehorizoncontainsmorethan12percent nepheline-syenites, withacentralstock age Tomtor alkalinecomplexcomprisesanouterringof deposit inBrazil(Pollard,1995).TheNeoproterozoic- deposit inSiberia,RussiaandtheMorrodosSeisLagos exploited. Themostsignificantofthesearethe Tomtor are knownacrosstheworld,butnotcurrentlybeing Numerous othercarbonatite-hostedniobiumdeposits which iscurrentlybeingevaluated. carbonatite complexcontainsaniobium-tantalumdeposit same structurallineament,thenearbyCreviersyenite- is theonlyundergroundniobiummineinworld.On over 100metresbeneaththesurface,andNiobecmine (Belzile, 2009).Thesemineralisedzonesoccuratdepthsof long, withgradesof0.44–0.51percentniobiumoxide 50–150 metres wideanduptoapproximately750 is particularlyabundantinmineralisedlensesthatare plex. Itisdisseminatedthroughoutthecarbonatite,but is themainniobiummineralinSaint-Honorécom
Permian: aunitofgeological timebetween299and251million yearsago. Placer deposit:aconcentration ofheavymineralstransported anddeposited Stock: asmallbodyofigneousrock,emplaced beneaththeEarth’s surface, Palaeozoic: aunitofgeologicaltimebetween 542and251millionyearsago. 23 limestones.Pyrochlore 26 sedimentaryrocks. 24 ofcarbonatite, 25 formedinan - - - may alsobeformedinpost-collisional plate settingssuchaszonesofcontinentalrifting,butthey Strength Elements Several factorscontributetotheenrichmentofHighField tantalum. rare earthelements,butarelesscommonlyenrichedin high contentsofzirconium,yttrium(Y),niobiumandthe Mineral depositsinalkalineigneousrockstypicallycontain but lowniobiumandtantalum(Pollard,1989,Küster, 2009). rubidium (Rb),uranium,thoriumandrareearthelements by highcontentsofiron(Fe),fluorine,niobium,zirconium, such asalkaligranitesandsyenites,arecharacterised environments. Themostevolvedalkalineigneousrocks, tal collisionevent(orogeny). many other elements to form compounds) that are incompatible (see footnote 34). many otherelements toformcompounds)thatareincompatible (seefootnote34). Lueshe syenite-carbonatitecomplex,whichisCambrian of Congo),Oka(Quebec,Canada),andSökli(Finland).The well-studied examplesfromLueshe(DemocraticRepublic 33 32 31 30 29 28 27 for niobium.TheCretaceous zon whichisenrichedinpyrochlore,andhasbeenmined weathering ofthecarbonatiteshasformedalateritehori dolomite carbonatite(NasraouiandBilal,2000).Intense ameter, borderedbyaringdykeofcalcitecarbonatiteand in age, has a central core of syenite some 800 metres in di- Al in whichthemolecularamountofNa boles, oralkalipyroxenes).Peralkalinerocksareasubset potassium-rich minerals(feldspathoids,alkaliamphi mineralogy, asthoserockscontainingcertainsodium-or The alkalineigneousrocksareclassified,onthebasisof Alkaline toperalkalinegranitesandsyenites sedimentary hostrocks(Yang etal.,2009). formed bytheinteractionofcarbonatite-derivedfluidsand sociated withcarbonatitemagmatismandmayhavebeen deposit inChina,whichisalsoenrichedniobium,as (Lee etal.,2006).ThemajorBayanOborareearthelement abundant pyrochloreintheyoungerunitsofcomplex tised ultramaficrocks,carbonatitesandphoscorites,with of about20squarekilometres,andcomprisesmetasoma atite-phoscorite complexisDevonian groups (ZurevinskiandMitchell,2004).TheSöklicarbon containing mineralsoftheperovskiteandpyrochlore It includesthreeseparateniobium-mineraliseddeposits ing carbonatitesandfeldspathoid-bearingsilicaterocks. an elongatepluton,aboutsevenkilometreslong,compris
Na High field strength elements: Elements of high valency (able to combine with High fieldstrengthelements: Elementsofhighvalency(able to combinewith Post-orogenic: post-datingalltectonicprocesses associatedwithacontinen Post-collisional: post-datingthepeakof continental collision. Devonian: aunitofgeologicaltimebetween 416and359millionyearsago. Cretaceous: aunitofgeologicaltimebetween 145and65millionyearsago. Cambrian: aunitofgeologicaltimebetween 542and488millionyearsago. 2 O 2 3 O, K 30 . Alkalinerocksaremostcommonlyfoundinintra 2 O andAl 2 O 3 : sodiumoxide,potassiumoxideandaluminium oxide. 33 (HFSE),suchasniobiumandzirco- 28 Okacarbonatitecomplexis www.MineralsUK.com 2 29 O +K 31 inage,withanarea topost-orogenic 2 O exceeds - 27 - - 32 - - -
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5 Niobium–tantalum their formation.TheHFSEareincompatible years ago. rather thanintoearly-formingcrystalsof solidminerals. both theEarth’s crustandtheuppermost partofthemantle. lithospheric considered tobederivedfromtheenrichedsub-continental and syenites.Alkalinemagmasaremostcommonly nium, inalkalineigneousrockssuchasgranites 37 36 35 34 the subjectofanongoingexplorationprogramme. tion intheMotzfeldtintrusion(Steenfelt,1991)whichis also hosttheniobium-tantalum-REEpyrochloremineralisa mineralisation. Zonesofhydrothermallyalteredsyenite and theircountryrockscontainsignificanturanium-niobium Ilímaussaq Complex,hydrothermalveinsinthesyenites and Williams-Jones,2005).IntheKvanefjeldareaof these layersis0.1weightpercentniobiumoxide(Salvi niobium andtheREE.Theaveragegradeofin in eudialyte,withhighcontentsofzirconium,yttrium, which containstwenty-nineseparatelayersthatarerich occur inaunitoflayeredsyenitesknownaskakortokites, (Larsen andSorensen,1987).Themainmineraldeposits alkaline graniteswhicharespectacularlylayeredinplaces comprises arangeofmineralogicallyuniquesyenitesand Complex iselliptical,8x17kilometresatthesurface,and Ilímaussaq andMotzfeldtcomplexes.The Igneous Provinceinsouth-westGreenland,includingthe HFSE andREEthroughhydrothermal undergone furtherconcentrationofelementssuchasthe rocks, suchastheMotzfeldtdepositinGreenland,have land. However, manymineraliseddepositswithinalkaline way isintheIlímaussaqComplexofsouth-westGreen most famousexampleofaniobiumdepositformedinthis be accumulatedthroughcrystalsettlingintolayers.The HFSE typicallyformrelativelydenseminerals,whichmay and syenites.Furtherconcentrationcanoccurbecausethe found disseminatedthroughouthighlyevolvedgranites syenitic magmas;insomelocalities,oremineralsare they becomeenrichedinthemostevolved,graniticand major areaofinterestliesintheMesoproterozoic although explorationisunderwayinsomeareas.One mines operatinginalkalinegraniteandsyenitecomplexes, At thetimeofwriting,therearefewniobiumortantalum Jones, 2005). dioxide (Goodenoughetal.,2000,SalviandWilliams- that areenrichedinfluorine,chlorine(Cl)and/orcarbon highly mobileinfluidsassociatedwithperalkalinemagmas Williams-Jones, 2005).TheHFSEandREEappeartobe
Mesoproterozoic: aunit ofgeologicaltimebetween1600and 1000million Hydrothermal: formed fromhotwater-rich fluids. Incompatible elements:arethosethat concentratedintomoltenmagmas, Lithospheric: thelithosphereisouter, rigidlayeroftheEarth,including 34 mantle,andareenrichedintheHFSEfrom 36 processes(Salviand 35 andthus 37 Gardar - - of secondaryHFSE-bearingminerals,includinggittinsite mineral, haematite. tisation zone wherethegranitehasundergoneextensivehaema area ofabout36squarekilometres.Ithasacentralore pluton, whichisMesoproterozoicinage,outcropsoveran In easternCanada,theStrangeLakeperalkalinegranite the REE. rich syenitesthatareenrichedinzirconium,niobiumand (> 500squarekilometres)alkalinecomplexwitheudialyte- age PilanesbergComplexofSouthAfricaisanotherlarge (Salvi andWilliams-Jones,2005).TheMesoproterozoic- cent niobiumoxideand0.7weightpertantalum concentrates haveaveragegradesofeightweightper been minedonandoffformanyyears,theloparite are richineudialyte,lopariteandapatite.Loparitehas syenite massifcontainslayeredsyeniteswithlayersthat In Russia’s KolaPeninsula,theDevonian-ageLovozero 39 38 a Palaeoproterozoic-agealbite-rich peralkalinegraniteat niobium andtantalumareextracted alongwithtinfrom consistent throughoutthegranite (Küster, 2009).InBrazil, tion oftheseoremineralsappearstoberemarkably chiefly columbite-tantaliteandpyrochlore.Thedistribu contains disseminatedtantalumandniobiumoreminerals, granite stockisabout800metresinsurfacediameterand veins (BGS,2009).InSaudiArabia,theGhurayyahalkaline tres longwithnumerousmineralised,pyrochlore-bearing an elongatebodyofnephelinesyeniteover3.5 kilome the Kanyikaniobium-tantalumdeposit,whichcomprises niobium oremineral.InMalawi,explorationisongoingat massif (Kovalenkoetal.,1995).Pyrochloreisthemain mally alteredlatephaseintrusionsofaperalkalinegranite zirconium-niobium-REE depositisformedbythehydrother In Mongolia,theDevonian-ageKhaldzan-Buregtey to developthemforREE,niobiumandtantalum. currently ownedbyAvalon Rare MetalsInc,whichintends and Williams-Jones,2005).TheThorLakedepositsare average gradesupto0.4weightpercentniobium(Salvi hosting themajorityofniobiumandtantalum, tantalum andzirconium,withcolumbite-tantaliteminerals posits areenrichedinberyllium(Be),yttrium,REE,niobium, alised zones,knownastheThorLakedeposits.Thesede granites withanumberofhydrothermallyalteredminer Lake igneouscomplexcomprisessyenitesandperalkaline Northwest Territories, thePalaeoproterozoicBlatchford Jones, 2005,SalviandWilliams-Jones,2006).InCanada’s of 0.56weightpercentniobiumoxide(SalviandWilliams- and pyrochlore.Orefromthiszonehasanaveragegrade
Gittinsite: Acalcium-zirconium-bearing silicatemineral. Haematisation: alteration associatedwiththeformationof ironoxide 38 andcalciummetasomatism,producingarange www.MineralsUK.com - - - - 39 -
- 6 Niobium–tantalum large peraluminousleucogranitic the world.Theseintrusionstypicallytakeformofa this typearethemainhostsfortantalumdepositsacross zones ofcontinentalcollision.Granitesandpegmatites most commonlyemplacedaspost-orogenicplutonsin formed bymeltingofpre-existingcrustalrocks,andwere than niobium)(C beryllium, tin(Sn),tantalumandniobium(tantalumgreater type offeldspar. aluminium oxide. lar (calciumoxide+sodiumpotassium oxide)islessthanmolecular peraluminous Granites andpegmatitesoftheLCTfamilyaretypically in lithium,caesium,tantalum) Granites andpegmatitesoftheLCTfamily(enriched Morocco, Nigeria,andNamibia. tantalum depositsoccurinmanyothercountries,including peralkaline intrusions with the potential for niobium and/or the Pitingamine(Bastos-Netoetal.,2009).Alkalineto 43 42 41 40 stage alteration,suchaskaolinisation Many ofthepegmatiteshavebeenhighlyaffectedbylate- (tin oxide)isalsoanimportantoremineralinsomebodies. microlite, ixioliteandwodginite.Tantalum-rich cassiterite the mostimportantaregenerallycolumbite-tantalite, types cancontainarangeoftantalumminerals,which pegmatites fallingintothefirstthreetypesarezoned.All type; andthealbitetype(C type; thecomplexlepidolitealbite-spodumene beryl type;thecomplex(spodumene-petalite-amblygonite) swarms. LCTpegmatitescanbedividedintofivetypes:the Many ofthelargesttantalumdepositsoccurinpegmatite and Cuney, 2005). trated intheuppermostpartsofgraniticbody(Linnen disseminated tantalumoreminerals,particularlyconcen alteration bylate-stagefluids.Thesegranitesmaycontain Australia, althoughproductionfromtheseminesceased has comefromtheGreenbushesandWodgina minesin In recentyears,muchoftheworld’s productionoftantalum heterogeneous, showingextensivealbitisation muscovite, topazandtourmaline,aretypicallyrather The granitebodiescontainmineralssuchasbiotite, sociated withexposedgraniticplutons. although insomeareasswarmsofpegmatitesarenotas at thegreatestdistancefromgranite(C halo ofpegmatites,withthemostmineralisedpegmatites
Kaolinisation: alteration ofrockstoproducekaolin,alsoknown aschinaclay. Albitisation: alteration byfluidstoproducethesodium-rich mineral, albite,a Leucogranitic: alight-coloured,silica-rich typeofgranite. Peraluminous: achemicaltermusedforrocks inwhichthetotalmolecu 40 andenrichedinlithium,rubidium,caesium, ˇ erný andErcit,2005).Thesemagmasare ˇ erný, 1989).Manyofthe 41 plutonsurroundedbya 43 . ˇ erný, 1989), 42 and - - - mineralised pegmatitesareknown fromtheSuperior Tanco pegmatite.Inaddition,numerousothertantalum- 1989). Caesiumandlithiumarealsoproducedfromthe ing thatprocessingofTanco ore isratherdifficult(C occur (14inall)andtheyaregenerallyfine-grained,mean grade incertainzones.Awiderangeoftantalumminerals als arefoundthroughout,thoughconcentratedathigher pegmatite type,andisstronglyzoned;tantalumoreminer a room-and-pillarundergroundmine.Itisofthecomplex thick and1600metresalongstrike,whichisexploitedin forms ashallowlydippingsheet,uptoabout100metres the Earth’s crust, usuallyanepisodeofcontinentalcollision. (greater thanthreekilometrelong)syn-tectonic mine insouth-westernAustraliaishostedagiant Advanced Metals(previouslyTalison). TheGreenbushes between 2008and2011.BothminesareownedbyGlobal 46 45 44 complex-type pegmatitebodyofArchaean metavolcanic bearing BernicLakepegmatitegroup,whichintrudes owned byCabotCorporation.Itispartoftherare-metal tantalum mineralisationatTanco, inManitoba,Canada, An Archaeanpegmatitebodyalsoformsthehostfor pegmatites isextractedbyopenpitmining. (Sweetapple andCollins,2002).Tantalum fromthese dumene type,andwodginiteisthemaintantalummineral is formedbyaseriesofpegmatitesheetsalbite-spo columbite andwodginite.AtMountCassiteritethedeposit tantalum mineral,togetherwithsomemanganese-rich of albite-type,withmanganese-richtantaliteasthemain Lode isadyke-likepegmatiteaboutonekilometrelong, erite tantalum-mineralisedpegmatites.TheWodgina Main which includestheWodgina Main LodeandMountCassit- important areahereistheWodgina pegmatitedistrict, include sometantalum-mineralisedexamples.Themost Archaean rocksofthePilbaraCraton,andmanythese a largenumberofpegmatiteswarmsoccurwithinthe pit andundergroundmining.Innorth-westernAustralia, Greenbushes pegmatitehasbeenexploitedbybothopen the maintantalummineral(Partingtonetal.,1995).The and laterhydrothermalmineralisation,wheremicroliteis and tapiolitesinfractureswithinearlysilicatephases; form inclusionsincassiteriteandtourmaline;tantalites formed mineralssuchaswodginiteandixiolite,which mineralisation arerecordedwithinthispegmatite:early- body (Partingtonetal.,1995).Threephasesoftantalum appear tobegeneticallyassociatedwithalargergranitic sociated withtinmineralisation.Thispegmatitedoesnot contains largeresourcesofbothtantalumandlithium,as
Metavolcanic: metamorphosed volcanicrocks. Archaean: aunitofgeological timebetween3800and2500 million yearsago. Syn-tectonic: formedduringanepisodeof tectonicactivityanddeformationof 46 Archaeanrocks.TheTanco pegmatite www.MineralsUK.com 45 age,which 44 , zoned, ˇ erný, - - - - 7 Niobium–tantalum province, andtheyareconsideredtobeOrdovician intruded intotheProterozoicrocksofNampulaSub pegmatites, ownedbyNoventaLtd.Thesepegmatitesare tion currentlyfocusedinthezonedMarropinoandMorrua been minedsince1926,withtantalumminingandexplora contains numerousmineralisedpegmatiteswhichhave In Mozambique,theAltoLigonhaPegmatiteProvince Quemeneur, 1997). at Nazareno,intheMinasGeraisdistrict(Lagacheand for tantalum,niobiumandlithiumattheVolta Grandemine zoic Brazil, alarge(aboutonekilometrelong),zoned,Protero Province ofOntarioandManitoba(Selway 48 47 mineralised granitesandpegmatitesarealsofoundin (Graupner etal.,2010).Numerousexamplesoftantalum- are veryvariable betweendepositsandfigures givenareindicative only). Table 3 syenite Alkaline graniteand primary deposits Carbonatite-hosted LCT-type pegmatite LCT-type granite secondary deposits Carbonatite-sourced Deposit type
Ordovician: aunitofgeologicaltimebetween488and443millionyearsago. Proterozoic: aunitofgeologicaltimebetween2500and542millionyearsago. 47 pegmatitebodyofalbite-spodumenetypeismined Key characteristics andexamplesofthemajor typesof niobium andtantalumdeposits (gradesandtonnages or hydrothermalprocesses concentrated bymagmatic rocks. Oremineralsmaybe with silicicalkalineigneous lum depositsassociated Niobium andlessertanta- provinces rocks inalkalineigneous within carbonatiticigneous Niobium depositsfound (Li-Cs-Ta-enriched) type with pegmatitesofLCT bium depositsassociated Tantalum andlessernio- altered are oftenhydrothermally leucogranitic plutons,which ated withperaluminous niobium depositsassoci- Tantalum andlesser trated ore mineralsareconcen- intrusions inwhichniobium sions abovecarbonatite ing orsedimentarysucces- Zones ofintenseweather Brief description et al.,2005).In 48 inage - - - - at gradesof0.1to1%Nb Generally <100milliontonnes, at 0.59%Nb reserves: 23.5milliontonnes Niobec, proven&probable at gradesof<0.05%Ta Generally <100milliontonnes, at gradesof<0.05%Ta Generally <100milliontonnes, 3% Nb < 1000milliontonnesatupto known deposit atTomtor, tonnagenot Up to12%Nb Typical gradesandtonnage and <0.1%Ta be magmaticinorigin(Küster, 2009). matic alteration,thetantalummineralsareconsideredto the granitesshowsignificantevidenceoflatermetaso disseminated throughouttheseintrusions,andalthough rather thaninpegmatites.Columbite-tantalitemineralsare the mineralisationisfoundinstock-likegraniteintrusions, towards production.Thesedepositsareunusualinthat and Nuweibiprospectsarecurrentlybeingdeveloped tantalite minerals(Küster, 2009).InEgypt,theAbuDabbab complex-spodumene typewhichisminedforcolumbite- Pegmatite, aCambrian-agedyke-likezonedpegmatiteof tres, buttantalumminingisfocusedontheMainKenticha whole hasanareaofapproximately2500squarekilome granites inEgypt.AtKenticha,thepegmatitefieldasa pegmatites ofSomalia,andtheAbuDabbabNuweibi the KentichapegmatitefieldinEthiopia,Majahayan the Arabian-NubianShield(Küster, 2009).Theseinclude North Africa,intrudedintotheNeoproterozoicrocksof 2 O 5 inlateriticdeposits. 2 O 2 2 O 5 O
5 5 inplacer
2 2 O O 2 5 5 O 5
Congo Democratic Republicof Tomtor, Russia;Lueshe, Araxá andCatala˘o, Brazil; Major examples Marropino, Mozambique ticha, Ethiopia;Morrua& Volta Grande,Brazil; Ken- Australia; Tanco, Canada; Greenbushes andWodgina, Egypt; Yichun, China Abu DabbabandNuweibi, Arabia; Kanyika,Malawi Brazil; Ghurayyah,Saudi Lake, Canada;Pitinga, sia; ThorLakeandStrange Greenland; Lovozero,Rus- Motzfeldt andIlímaussaq, Canada Niobec, Canada;Oka, www.MineralsUK.com - - 8 Niobium–tantalum www.MineralsUK.com
Figure 3 Map showing the global distribution of niobium and tantalum mines, deposits and major occurrences. 9 Niobium–tantalum Several regionsofChinahavetantalum-mineralisedgran deposits derivedfromthepegmatites. deeply weatheredpegmatitesandfromsecondaryplacer 1995). Columbite-tantalitemineralsareminedbothfrom the DemocraticRepublicofCongo(RomerandLehmann, belt whichextendsthroughBurundi,Rwanda,Ugandaand mineralised pegmatitescutstheMesoproterozoicKibaran In CentralAfrica,azoneofNeoproterozoic-agetantalum- can bepoorlyconsolidated, andonlyrequire drillingand involving scrapers,bulldozers andloaders.Placerdeposits Land-based placerdepositsare amenabletostripmining are alsominedusingopen-pit methods. ore bodies,suchastheAraxá carbonatitedepositinBrazil, tres butseldomexceeds100metres.Heavilyweathered Open-pit miningmayreachdepthsofseveralhundredme by truckorconveyorbeltforstockpilingpriortoprocessing. digging orblastingtheore,followedbyremovalofore Open-pit methodscommonlyinvolveremovingoverburden, ore bodiesareamenabletoopen-pitminingtechniques. Massive, orsteeply-dipping,low-gradenear-surface Surface mining artisanal andsmallscalemining(ASM). amounts ofniobiumandtantalumarealsoextractedby underground) mining,oracombinationofboth.Significant extraction aresurface(oropen-pit)andsub-surface and depthoftheorebody. Themostcommonmethodsof mineral; thetonnageandgrade;shape,geometry include: thephysicalandchemicalpropertiesofore rence. Factorsthatdictatetheselectionofminingmethods tantalum aresimilartoothermetalsofcomparableoccur The miningmethodsemployedtoextractniobiumand Extraction Extraction methodsandprocessing reprocessed toproducetantalum. from secondaryplacerdeposits.Thetinslagsarebeing weathered tin-mineralisedgranitesandpegmatites, Malaysia andsouth-westernThailand,tinisproducedfrom have beenminedforcolumbite-tantaliteinthepast.In China) andtheNanpingpegmatites(south-eastern Elsewhere inChina,theAltaipegmatites(north-western rich cassiterite,andminormicrolite(Yin etal.,1995). in theformofdisseminatedcolumbite-tantalite,tantalum- lepidolite granite,whichcontainstantalummineralisation most partofthisbatholithisahighlyfractionatedtopaz- kilometres) graniticbatholithofJurassicage.Theupper deposit, whichishostedinasmall(lessthan10square ites andpegmatites.ThemostwellknownistheYichun - - - - reduction grade smelterwastescanbeupgradedbyelectrothermic although exceptionallythismayriseto30percent.Low- typically containseightto10percenttantalumoxide, decline and isaccessedviaa60-metreshaft20-degree Manitoba, Canada.ThemineislocatedunderBernicLake pillar miningmethodswereusedattheTanco pegmatitein conveyor ordumptrucktotheprocessingplant.Roomand roof support.Oreisblastedandthentransportedbyrail, per centtantalumandniobiumoxides(Roethe,1989). around 14 per cent. Tantalum is extracted from cassiterite However, thepercentageismuchhigherfor tantalumat for lessthantwopercentoftotalglobalniobiumproduction. of tinsmelterwaste.Niobiumproducedinthiswayaccounts Niobium andtantalumcanalsobeextractedasaby-product By-product production placer middlings and electrostatic furnace, utilisingcalcium oxide,ironoxideandcarbonasreducing agents. field. minerals usingmagneticforce. the formofaspiralramp. 55 54 53 52 51 50 49 ous stopes progresses inahorizontaldirectionbydevelopingnumer pillar isanundergroundminingtechniquewhere tion, geo-technicalsupportandorehandling.Room development includingshaftsinking,de-watering,ventila Underground operationscommonlyrequireextensivemine large, open-pitminingmethodsbecomeuneconomic. waste tooreratio,orstripratio.Oncetheratiobecomes factor inthedecisiontouseundergroundmethodsis example ifthedepositbecomestoodeep.Anothermajor surface methodsare,orbecomeprohibitivelyexpensive,for Underground miningmethodsareusuallyemployedwhen Underground mining less thanthoseforundergroundoperations. Capital andoperatingcostsforopen-pittechniquesarefar blasting techniques. tions, suchasWodgina Mine,areminedusingdrillingand simple strippingmethods,whilsthard-rocksurfaceopera example, tin-tantalumplacersinMalaysiaareminedusing blasting wherematerialshavebecomecemented.For
Electrothermic reduction: areductionreactionperformedin an electricarc Electrostatic separation:theselectivesorting oforemineralsusinganelectric Magnetic separation:theselectivesorting ofmagneticallysusceptibleore Middlings: particlesofintermediategrade andsize. Cassiterite: tinoxideoremineral,SnO Decline: amineentrancewhichisneitherhorizontalnorvertical;oftenittakes Stope: thevoidcreatedbyextractingore. 50 fromthesurface(Cabot,2001). 55 49 yieldingasyntheticconcentratewithupto50 , orrooms,leavingpillarsofmaterialfor 52 54 usingshakingtables,andmagnetic separationmethods.Tin smelterwaste 2 . www.MineralsUK.com 53
- - - 51
10 Niobium–tantalum
ORE TYPE
Pyroch lore Tantalit e e.g. Niobec Mine e.g. Greenbushes Mine
Crushing, milling and Undersize material screening sta ges to tailings Coarse desliming Fine desliming Coarse and fine gravity separation using shaking Coarse carbonate Fine carbonate tables, jigs and spirals flotation flotation Concentrate de-watering using cyclones and filter bed Desliming Slimes
Concentrate drying Low intensity Magnetite magnetic separation Concentrate (4-6% Ta2O5)
Diamine collector Pyrochlore flotation Tailings High intensity magnetic Non-magnetic separation fraction to tailings Xanthates Sulphide flotation Sulphides
Magnetic fraction roasted Antimony and
www.MineralsUK.com Hydrochloric Concentrate leaching minor sulphides to Acid tailings
Concentrate (54% Nb2O5) Concentrate (20-30% Ta2O5)
Figure 4 Generalised beneficiation flow diagrams, based upon the Niobec and Greenbushes operations. 11 Niobium–tantalum froth flotationusingdiaminecollectors sought-after pyrochloreiscollectedfromtheslurryby intensity magneticseparation,andsenttowaste.The stage. Magnetiteisremovedfromtheslurry, bylow of frothflotation,followedbyanadditionaldesliming metal oxides. ing. mineral acids. minerals fromhydrophilic(water-attracting) oreminerals. variations inmineraldensity. Screw) are removedfromaslurrybyseriesofrotatingrakes(similartoanArchimedes ity separation oxide usinganumberofmethodsinmultiplestages:grav- rock isfurtherconcentratedtoaround54percentniobium mineral particles.Theslurrycontainingniobiumandwaste desliming and classified,afterwhichtheresultantslurryissentfor At theNiobecoperationinCanadaniobiumoreisscreened the physicalandchemicalcharacteristicsofore. tantalum orefromgangue crushing theorefollowedbyseparationofniobiumand mally undertakenat,orcloseto,theminesiteandinvolves niobium andtantalumcontents.Initialconcentrationisnor After miningtheoresareprocessedtoincreasetheir Processing 62 61 60 59 58 57 56 upon thecharacteristicsofore. and magneticseparationtechniques,againdepending 30 percenttantalumoxideusingpredominantlygravity tantalum andwastematerialisconcentratedtoaround liberate tantalummineralparticles.Theslurrycontaining niobium ores;theyarecrushed,milledandscreenedto Tantalum oresareinitiallytreatedinasimilarmannerto niobium oxide(Figure4)(Iamgold,2009). ing afinalconcentratethatcontainsaround54percent Residual impuritiesareleachedbyhydrochloricacid,leav froth flotationisusedtoremovesulphides,suchaspyrite. vibrating screensandscrewclassifiers and milledinrodorballmillsoperatingclosedcircuitswith Niobium oreisfirstcrushedinjaw, coneorimpact crushers Ore beneficiation ent processingroute. tantalum aregeochemicallysimilareachrequiresadiffer of physicalandchemicalmethods.Althoughniobium separation, andacidleaching
Diamine collectors:a positivelychargedcationiccollectorused tofloatrare- Desliming: theremovalofparticlesin micronsizerangepriortoprocess Acid leaching:theprocessofextractingmetal fromaconcentrateusing Froth flotation:theselectiveseparation of hydrophobic(water-repelling) ore Gravity separation:theselectivesortingoforemineralsbyexploitingnatural Screw classifiers:awetgravityseparationmethodinwhichdenseparticles Gangue: wastematerialassociatedwithoreminerals. 61 . Carbonatematerialisremovedbytwostages 58 , frothflotation 56 material,usingacombination 60 59 may be used, depending on maybeused,dependingon , magnetic and electrostatic , magneticandelectrostatic 57 to liberate niobium toliberateniobium 62 . Afinalstageof
- - - - of potassiumtantalumfluoride(K mixed organicsolventsolutionresultsinthecrystallisation metal production.Theadditionofpotassiumfluoridetothe bides. Niobiumoxideisalsothestartingpointforniobium temperature isusedtoproduceniobiumandtantalumcar separation isusedtoseparatetheparamagnetic to sixpercenttantalumoxide.Highintensitymagnetic producing atantalumconcentratecontainingaboutfour powders withoutmelting. water). tion, phasetransitionsortheremovalof volatile matter(e.g.carbondioxideand externally appliedmagneticfield. of sintering furnace toformniobiumandtantalumoxides.Theprocess and jigs are processedusingacircuitofshakingtables,spirals At theGreenbushesmineinAustraliatin-tantalumores 66 65 64 63 sulphuric and tantalumcanbeextractedfromthehydrofluoric- ion exchange,toseparateniobiumfromtantalum.Niobium liquid separationmethods,involvingsolventextractionor tantalum-bearing acidsolutionisthentreatedusingliquid- mixture ofhydrofluoricandsulphuricacids.Theniobium- A mixedniobium-tantalumconcentrateisdigestedusinga main methods. reduced toformpuremetalsandmetalpowdersbytwo (Albrecht, 1989).Thetantalumandniobiumcompoundsare different compounds Tantalum andniobiummetalcanbeproducedfromthree Conversion tometal separate tantalumfromtin(Figure4)(Fetherston,2004). flotation androastingtoremovesulphides,smelting fraction isfurtherprocessedusingacombinationoffroth 30 percenttantalumoxidebyroasting.Thenon-magnetic paramagnetic fractionisfurtherconcentratedtoaround lum grainsfromthenon-magnetictin-tantalumgrains; for tantalummetalproduction(Figure5). monia (NH the mixedorganicsolventsolutionbyadditionofam Niobium andtantalumareprecipitatedashydroxidesfrom ant inkerosene. tantalum andisusuallyperformedusinganamineextract is usedtoproducehigh-puritysolutionsofniobiumand iron, manganese,tinandtitanium(Figure5).Ionexchange ketone (MIBK),whilstleavingbehindimpuritiessuchas cyclohexanone, tributylphosphate(TBP)ormethylisobutyl
Sintering: aprocess of formingacoherentbondedmassbyheating metal Calcined: athermalprocessappliedtoores inordertobringaboutdecomposi Paramagnetic: aformofmagnetismthat onlyoccursinthepresenceofan Shaking tables,spiralsandjigs:water gravitybasedseparationdevices. 63
. Theroughconcentrateisde-wateredanddried acid mixturebyusingorganicsolvents,suchas 3 ). Theresultanthydroxidesarecalcined 66 theoxideproducts,withcarbon,athigh — fluorides, oxidesandchlorides www.MineralsUK.com 2 TaF 7 ), thepre-requisite 64 tanta- 65 ina - - - - 12 Niobium–tantalum utilising high-energy electronbeamsasaheatsource. powder andironoxide asreducingagents. beam melting purification isachievedbyvacuum arcfurnaceorelectron tantalum vesselsunderlow-oxygenconditions.Further ics industry, theconversionprocessisperformedusing ensure ahighdegreeofpurity, asrequiredbytheelectron- metal powder, potassiumfluorideandsodiumfluoride. To then roastedinacontinuousfurnacetoproducetantalum liquid sodiumandinertsaltstoformapaste.Thepasteis talum metal.Potassiumtantalumfluorideisblendedwith with sodiumisthemostcommonmethodofproducingtan The reductionofpotassiumtantalumfluoridebyreaction added tothemixturepriorreduction(Albrecht,1989). containing about60percentniobium,ironoxidepowderis to increasethepurityofniobium.To produceferro-niobium, lime andfluorspar. Electronbeammelting is commonlyused 68 67 mic reduction um. High-purityniobiummetalisproducedbyaluminother niobium metalandtheotherisusedtoproduceferro-niobi- production ofniobiummetal:oneisusedtoproducepure Two slightlydifferentproductionroutesareavailableforthe Figure 5
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- - A c 69 Lezhnev (©EnoughProject) Figure 6 Artisanal miningofcoltan provide alivelihoodforover100 millionpeopleworldwide Artisanal andsmallscalemining (ASM)isbelievedto extracted byartisanalandsmall scalemining(ASM). cessed conventionally, significantamountsarealso Although niobiumandtantalumareextractedpro R alc m
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e h b e y - 13 Niobium–tantalum addition some large electronicscompanies arenow the problemsofASMandconflict mineraltrading.In charities haveinitiatedschemes aimedatalleviating Many non-governmentalorganisations (NGOs)and tronic goodssuchasmobilephones (Figure7). may beexportedtoAsiaforinclusioninconsumerelec components suchascapacitors.Finallythese then beshippedtothewesternworldforuseinelectrical the sourceoforiginalore.Theprocessedmaterialmay and smelting.Onceprocesseditisimpossibletodetermine Burundi orUgandamaybeshippedtoAsiaforprocessing tronic productsthroughouttheworld.OrefromRwanda, Illegally tradedcoltanoremayendupinconsumerelec ing (Bunting,2010). excess of$1billionin2009throughconflictmineraltrad- It isestimatedthatrebelgroupsintheDRCmade bouring countriessuchasRwanda,BurundiandUganda. the majorityofcoltanminedinDRCendsupneigh- quantity ofcoltanminedandexported.Itisbelievedthat Consequently itisdifficulttoaccuratelycalculatethe pegmatite sources,islabourintensiveandunregulated. small scaleminingofcoltan,fromeitheralluvialor global tantalumproductionwasfromAfrica.IntheDRC (DRC). Itisestimatedthatin2009over50percentof Africa, inparticulartheDemocraticRepublicofCongo Coltan isfoundinsignificantquantitiespartsofcentral ends andtofinancefurtherfighting. from thesaleofconflictmineralstofurthertheirown is oftenorganisedbyarmedgroupswhousetheprofits given risetotheterm‘conflictminerals’.Theirillicitmining The miningofthesemineralsundersuchconditionshas conditions ofarmedconflictandhumanrightsviolations. significant quantitiesbyASM,cansometimesbeminedin bite-tantalite (coltan)(Figure6),whichareproducedin Certain minerals,suchasgold,tin,tungstenandcolum (Hentschel etal.,2003). ties fallingoutsidethehostcountries’legalframework Additionally, ASMisoftenunregulatedwithmany activi ▪ ▪ ▪ ▪ ▪ characterised by: but capital-,mechanisation-andtechnology-poor. ASMis and isdefinedasminingactivitiesthatarelabour-intensive ▪ ▪ ▪ ▪ ▪ Insufficient considerationofenvironmentalissues Low salaries Inefficiency inextractionandprocessing Poorly qualifiedandtrainedpersonnel Poor occupationalsafety - - - - Figure 7 (Bunting, 2010). monitor exports,controlitsarmy andcombatrebelforces also reliesontheabilityofcountries liketheDRCto reasons explainedabove.The successoftheseschemes completely avoidtheuseofthese componentsforthe their products.However, itislikelytoprovedifficult refusing touseconflictmineral-bearingcomponentsin chain. Source:(EnoughProject,2011).
shipped tothewestern to Asiamanufacture electrical components consumer electronics S coltan inDemocratic Asia forsmelting and Co conversion tometal Rwanda, Ugandaor m M P Europe andthe USA such ascapacitors Republic ofCongo players, laptopsand Ore cameras aresoldin circuit boardsand world toproduce ro to neighbouring m al o Ore b c p An exampleofaconflictmineralsupply
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14 Niobium–tantalum other niobiumcompounds,suchaschloride(NbCl purity. Itisgenerallythestartingpointforproduction of produced indifferentgradesatbetterthan99percent Niobium pentoxide(Nb of forms,themostsignificantwhichare: Niobium andtantalumareutilisedtradedinavariety Specifications Specifications andUses 70 agent. tantalum carbide(TaC) andlithiumtantalate(LiTaO niobium carbide(NbC)andlithiumniobate(LiNbO metal includecarbothermicreduction at around800°C.Othermethods ofproducingtantalum reduction ofpotassiumtantalum fluoridesaltsbysodium Tantalum metalandpowder isformedbythe tantalum byweight. brown metallicpowdercontaininginexcessof90percent in afurnace.Theresultingtantalumcarbideisheavy, sintering fine-grainedtantalumpowderwithexcesscarbon hardness 9-10)refractoryceramiccompound,formedby Tantalum carbide(TaC) isanextremelyhard(Mohs Tantalum pentoxide(Ta solvent extraction. sium fluoridewiththetantalum-bearingextractantfrom tantalum metalpowderandisproducedbyreactingpotas Potassium tantalumfluoride(K electron beamorvacuumarcfurnacemelting. nothermic reaction.Furtherpurificationisachievedby pentoxide, ironoxideandaluminiumpowderbyalumi niobium andisproducedbyreducingamixtureof Ferro-niobium (60%Nb)containsabout60-70percent further purificationachievedbyelectronbeammelting. pentoxidewith by thealuminothermicreductionofniobium Niobium metalandpowder 87 percentniobium. a heavy, brown-greymetallicpowdercontaining around carbon andheatingtoaround1800°C.Niobiumcarbideis mixture offinely-groundniobiumpowderwithanexcess 8.5-9) refractoryceramiccompound,formedbysinteringa Niobium carbide(NbC)isaveryhard(Mohshardness tantalum compoundsincludingchloride(TaCl Carbothermic reduction: anexothermicreactioninvolvingcarbon asareducing 2 2 O O 5 5 ) ) isthestartingpointforother is a colourless, unreactive solid isacolourless,unreactivesolid 2 TaF is most commonly formed is mostcommonlyformed 7 ) istheprecursorto 70 oftantalum 3 ). ). 3 ). - 5 ),
5 - ), ), harmony withtissue withoutcausingdamagingchanges. cold-formed shape;returningtothepre-deformed shapeuponheating. temperature. to mechanicalstrain. the puremetal. ing thesameperiodoftime(Figure9). carbides andcapacitor-grade powdershasdecreaseddur period between2004and2010.Theproductionofboth and metalproductsallrepresentgrowthareasduringthe Metallurgical gradepowders,chemicals,tantalumingots carbides makeuptheremaining41percentofend-uses. for about48percent.Tantalum metalproducts,ingotand sources suggestthatcapacitor-grade powder mayaccount end-use oftantalumatabout24percent.Althoughsome while capacitor-grade powderproductionis the largest is usedinthemanufactureofmetallurgicalgradepowders to manufacturetantalumchemicals.Afurther17 percent In 2010almost18percentoftantalumproductionisused niobium hasdecreased(Figure8). production ofniobiummetalproductsandhigh-purityferro- niobium chemicals and niobium alloys has increased whilst products. Between2004and2010theproductionofboth high-purity ferro-niobium,andotherniobiummetal ture ofniobiumalloys,chemicalsandcarbides, steels; theremaining11percentisusedinmanufac to produceferro-niobium,usedinhighstrengthlowalloy About 89percentofglobalniobiumproductionisused ▪ ▪ ▪ ▪ ▪ ▪ plications (Table 4and5).Thesepropertiesinclude: vital componentsinadiverserangeofproductsandap The uniquepropertiesofniobiumandtantalummakethem Uses pentoxide andelectrolysis 76 75 74 73 72 71 piezoelectric properties are colourless,crystallinesolidswithuniqueopticaland Lithium-niobate (LiNbO be achievedinthefinalproduct. electron beammethods,averyhighdegreeofpuritycan salts. Bydoubleortriplemelting,usingarc-furnace ▪ ▪ ▪ ▪ ▪ ▪
Bio-compatibility: the abilityofaprosthesisimplantedinthe bodytoexistin Co-efficient ofcapacitance: theabilityofasolidtostorean electrical charge. Shape memoryproperties:theabilityofan alloyto‘remember’itsoriginal Superconductivity: azeroelectricalresistance occursinsomematerialsatlow Piezoelectric: theaccumulationofelectrical chargeinamaterialresponse Electrolysis: amethodofreducingmetalsfrommetalliccompoundstoobtain bio-compatibility high coefficientofcapacitance shape memoryproperties very highmeltingtemperatures corrosion-resistance superconductivity 76 73 3 72 ) andlithium-tantalate(LiTaO . 71 ofpotassiumtantalumfluoride 74 www.MineralsUK.com 75 3 ) - - - 15 Niobium–tantalum other inresponseto a changeingrainshape. 77 boundary deformation dition ofniobiumtosteelincreases strength,reducesgrain production ofhighstrengthlow alloysteels(HSLA).Thead- alloys. Niobium,intheformof ferro-niobium, isusedinthe Niobium andtantalumarebothusedintheproductionof Steel andotheralloys 1
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S i gh Vacuum gradeferro-niobium capable ofregainingtheirshapeonheatingto1120°C. Such alloyscanbebent,compressedordeformedbutare applications becauseoftheshapememoryproperties. Tantalum-ruthenium alloysareusedinanumberofmilitary such asmagneticresonanceimaging(MRI)scanners. ducting magnetsrequiredformedicalimagingequipment, niobium-tin alloyscanalsobeusedtoproducesupercon processing equipmentandpipelines.Niobium-titanium corrosion resistantandareusedtomanufacturechemical zirconium, titaniumandtin.Thesealloysareextremely Other metalswhichareusedinalloyswithniobiuminclude joints andmedicaldevicessuchaspacemakers. with humantissueisutilisedintheproductionofprosthetic rust-free fastenings.Thebio-compatibilityoftantalum-alloys quired suchaschemicalprocessingequipment(Figure10)and is alsousedinapplicationswherecorrosionresistancere- C103 oxidation andcorrosion. strength andcreepresistance attemperaturesabove700°C, andresistanceto niobium oxideandvacuumarcfurnacemelting. making itthecathodeofanelectrochemical cell. 89 percentniobium.Tantalum superalloys,ReneN6 two and 8.5 per cent tantalum. Many superalloys contain two and8.5percenttantalum. Manysuperalloyscontain tions suchasgasturbineblades,typicallycontainbetween tion and oilgaspipelines.Theyalsoprovidecathodeprotec- used tomanufacturevehiclebodies,shiphulls,railwaytracks, 80 79 78 CSMX-10 Inconel 718 stress applications.Examplesofniobiumsuperalloysinclude constituents ofsuperalloys t e
Superalloys: arehigh-performance alloysthathaveexceptional mechanical Vacuum gradeferro-niobium:ferro-niobiumproducedusinghigh-purity Cathode protection:atechniqueforreducing corrosionofametalsurfaceby e l 78 ® tolargesteelstructuressuchasoilplatforms.Tantalum , used in rocket thruster nozzles, which contains about , usedinrocketthrusternozzles,whichcontainsabout ® , usedinhigh-temperature,high-stressapplica- ® , which contains about five per cent niobium and , whichcontainsaboutfivepercentniobiumand 8 8 (Schwela, 2010a). of niobiumin2004and2010.Source: Figure 8 . 7 % 1 1 . 3 % Comparison ofend-uses 80 2010 usedinhigh-temperature,high- 79 and tantalum are important andtantalumareimportant www.MineralsUK.com 2 . 7 % 2 . 5 % 5 . 2 % 0 ® . and and 9 % - 16 Niobium–tantalum manufacture ofchemicalprocessingequipment. Figure 10 83 82 81 the formofTaNbC temperature applications.Tantalum andniobiumcarbides,in ceramic substancesthatareoftenusedinhigh-stress,high- Niobium andtantalumcarbidesareextremelyhard,refractory Carbides chromium, aluminium,molybdenum,titaniumandhafnium. nickel-iron; otherelementsalsousedinalloymixturesinclude appreciable amounts,upto50percent,ofnickel,cobalt,or Source: ©Corbis. Table 4 Physics Metallurgical Medicine Electronics Engineering Construction Chemicals surface coatings Ceramics and Automotive Industry
WTiTaNbC: tungsten-titanium-tantalum-niobium-carbide. WTiTaC: tungsten-titanium-tantalum-carbide. TaNbC: tantalum-niobium-carbide. Summary ofthe mainusesofniobiumbyindustry sector. Source:(TANB, 2011a). Tantalum andniobiumareusedinthe 81 , WTiTaC Particle physicsresearch Superalloys forjetenginesand turbineblades mapping) and magnetoencephalography(brainactivity Superconducting magnetic coils in MRI scanners technologies acoustic wavefiltersforsensorandtouchscreen Capacitors, streetlightingsystemsandsurface Cutting tools,railwaytracksandshiphulls systems forlargesteelstructures Architectural steelsandcathodeprotection pipelines Chemical processingequipmentandoilgas lenses Ceramic capacitors,glasscoatingsandcamera Vehicle bodies Usage 82 orWTiTaNbC 83 , may be added , maybeadded
purity, high-performancesolidmaterials. (CVD), orphysicalvapourdeposition(PVD) plied tosurfacesusingeitherchemicalvapourdeposition Thin coatingsofniobiumortantalumcarbidemaybeap cent titaniumcarbide,andninepercobaltbinder. tungsten carbide,10.5percenttantalumseven Such ahardmetalcompositemaycontain73.5percent metals arealsousedinhigh-speeddrillingandcuttingtools. strength andresistancetocorrosionabrasion,hard using acobaltornickelbinder. Onaccountoftheirveryhigh ite ofvariousmetalcarbidescementedintoacompactmass Cemented carbide,alsoknownashardmetal,isacompos- refractory coatingsinnuclearreactorsandfurnaces. and drillbitsfortheminingindustry. Carbidesare alsousedas speed cuttingandboringtools,teethforexcavatorbuckets to tungstencarbideinthemanufactureofindustrialhigh- 84 abrasion- andcorrosion-resistantcoatings,structural of productscontainingthesemetals,forexample,alloys, of applicationsandareoftentheprecursortoanumber Niobium andtantalumpowdersareusedinawiderange Powders resistance, increasingthelifeoftoolcuttingedges. Carbide coatingsoftenincreasestrengthandimprovewear
Vapour deposition:aprocessofthinfilmdepositionusedtomanufacturehigh- Niobium-titanium alloyandniobium-tin alloy nickel-niobium Vacuum-grade ferro-niobium andvacuum-grade niobium nitride Niobium-titanium alloy, niobium-tinalloyand niobate Niobium powder, niobiumoxideandlithium Niobium carbide HSLA ferro-niobium(60%Nb),niobiummetal and niobium-1%zirconiumalloy HSLA ferro-niobium(60%Nb),niobiummetal Niobium oxide HSLA ferro-niobium(60%Nb) Niobium product www.MineralsUK.com 84 techniques. - 17 Niobium–tantalum Table 5 heated orcooled. pounds withuniqueoptical,piezoelectricandpyroelectric Lithium niobateandlithiumtantalatearechemicalcom for useincapacitorsandhigh-performancebearings. eyeglass lenses,niobium-andtantalum-dopedceramics amples includehighrefractiveindexglassforcameraand production ofspecialityglassandstructuralceramics.Ex Niobium andtantalumoxidesarecommonlyusedinthe Chemicals than tantalum-basedcapacitors. but theyarecommonlylargerandhaveashorterlifespan Niobium powderisalsousedtomanufacturecapacitors powders formedium-voltage,medium-capacitanceuses. for low-voltage,high-capacitanceapplications;andflake powders forhigh-voltageapplications;nodular for capacitorproductionaremadeinthreeforms:angular mobile phonesin2010was417million.Tantalum powders capacitors (MBM,2006)andglobalproductionofnew because anaveragemobilephonecontains23tantalum capacitor isverysmallthisasignificantapplication an electricalcharge.Eventhoughthequantityusedineach the productionofcapacitorsbecauseitsabilitytohold ceramics. High-puritytantalumpowderisprimarilyusedin 85 Military Metallurgical Medicine Electronics Engineering Construction Chemicals surface coatings Ceramics and Automotive Industry
Pyroelectric: theabilityofamaterialtogeneratetemporaryvoltagewhen Summary ofthe mainusesoftantalumbyindustry sector. Source:(TANB, 2011b). goggles andGlobalPositioning Systems(GPS) Missile parts,ignitionsystems, nightvision rocket enginenozzles Furnace parts,superalloysfor jetenginesand devices suchashipjoints Pace makers,hearingaidsandprosthetic drives, andLEDlights sensor andtouchscreentechnologies,harddisc Capacitors, surfaceacousticwavefiltersfor Cutting tools bolts resistant fastenerssuchasscrews,andnuts structures suchasoilplatformsandcorrosion Cathode protectionsystemsforlargesteel Chemical processingequipment lenses andX-rayfilm Ceramic capacitors,glasscoatings,camera systems andenginemanagementmodules Anti-lock brakesystems,airbagactivation Usage - - 85
current technology. been fullygeologicallyevaluatedandiscommerciallylegallyminableusing of amineralcommodity. of rockthatis,ormaybecome,potentialeconomicinterestfortheextraction primary reserves and resources of niobium and tantalum are primary reservesandresourcesofniobiumtantalumare for niobiumandtantalumarenotwelldocumented.However, Unlike manyothermetalsglobalresourceandreservedata Resources production World resources,reservesand transistors anddigitalcircuits. applications suchaslightemittingdiodes(LED),solarcells, is aneffectivesemi-conductorusedinnumerouselectronic ducting magnets,usedinMRIscanners.Tantalum nitride Niobium nitrideisanimportantcomponentofsupercon used intouchscreentechnologies. devices, usedinrangefindingapplications.Theyarealso as mobilephones,motiondetectorsandlaserswitching acoustic wavefilters,whichareemployedindevicessuch electronic components,suchascapacitorsandsurface properties. Theyareprimarilyusedinthemanufactureof 87 86
Mineral reserves:amineralreserveisthepartofresourcewhichhas Mineral resources:amineralresourceisconcentrationofmineralsorbody Tantalum ingotsandtantalumoxide Tantalum metalandtantalumingots Tantalum metal ingots andtantalumnitride Lithium tantalate,tantalumpowder, tantalum Tantalum carbide Tantalum metal(sheets,rods,platesandwire) Tantalum metal Tantalum oxideandyttriumtantalate Tantalum powder Tantalum product 86 andreserves www.MineralsUK.com 87 - 18 Niobium–tantalum CBMM, 2011,Papp,2011a).Total resourcesarenotreportedasallcountriesincluded. Table 6 ** OnlyincludesresourcesfromCatalão(AngloAmerican,2011) * Deemeduneconomicat2010prices(Papp,2011a) Geological Survey. Statistics database, British 2009. Source:World Mineral ore) between1997and niobium contentofmined production (basedonthe Figure 11 respectively, accordingtotheTantalum-Niobium International to beabout317000tonnesandalmost153 number ofcountriesthanthoseniobiumandareestimated Tantalum oreresourcesandreservesarelocatedinagreater Tantalum resourcesandreserves seven percentoccurinCanada(Table 6). over 93percentoccurringinBrazilandtheremaining estimated tobeintheregionof485milliontonneswith Global niobiumorereserves,provedandprobable,are niobium resourcesincludeEgypt,MalawiandGreenland. and Canada.However, othercountrieswith unquantified Niobium resourcesarealmostexclusivelylocatedinBrazil Niobium resourcesandreserves for theforeseeablefuture,atleastnext500years. estimated tobemorethansufficientmeetglobaldemand Source Total United States Canada Brazil Estimated globalreservesandresourcesofniobiumore.(Iamgold, 2009,AngloAmerican,2011, Global niobium Proved andprobable reserves (tonnes) 484 436000 452 200000 32 086000 150 000*
Tonnes Nb 1 1 8 6 4 2 2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
1997 Contained Nb 11 322422 11 142740
1998 (tonnes) 179 682 ---- 1999 and refineryequipment.Demandforthesesteelsislinked HSLA, usedinthemanufactureofcars,buildings,ships niobium productionislinkedtogrowingconsumptionof the productionofcolumbiteandtin-slags.Theincreasein cent ofthetotal,withonlyminorproductioncomingfrom mineral pyrochlore,accountingforapproximately98per in 2009(Figure11).Theprimarysourceofniobiumisthe proximately 20000tonnesin1997toover100 World productionofniobiumrapidly increasedfromap Niobium production Production East, Africa,NorthAmericaandEurope(Table 7). 60 percentoccurinAustralia,Asia,RussiaandtheMiddle resources atapproximately40percent.Theremaining Production (DNPM–Brazil).Brazilhasthelargestshareof Study CentreandtheNationalDepartmentofMineral 2 2000 O 5
2001 Inferred resources
2002 11 900000 37 912000 (tonnes) n.a. 2003 ----
2004 www.MineralsUK.com 2005
2006 Contained Nb 214 200** (tonnes) 219 889 n.a.
2007 ----
2008 2
O - 5 2009 Source Most likely resource Percentage of Reserves (tonnes Ta) 88 base (tonnes Ta2O5) resources Brazil 129 274 40 87 360 Australia 65 771 21 40 560 China and Southeast Asia 33 112 10 7 800 Russia and Middle East 31 298 10 ---- Central Africa 28 576 9 3 120 Other Africa 21 318 7 12 480 North America 5443 2 1 500* Europe 2268 1 ---- Total 317 060 100 152 820 *Deemed uneconomic at 2010 prices (Papp, 2011b)
Table 7 Estimated global tantalum reserves and resources. (Papp, 2011b, Schwela, 2010a, DNPM, 2009).
particularly to the recent industrial development of nations (such as used in the Large Hadron Collider), glass and cam- such as China and India, and the rapid growth of the global era lens coatings, superalloys and functional and structural population. For example, in 1997 annual car production ceramics. was around 53 million vehicles compared with nearly 62 million in 2009 (OICA, 2011). In 1997 Brazil accounted for approximately 88 per cent of world niobium production. This figure has since risen to The increased demand for niobium may also be attributed about 95 per cent. Canada is responsible for the majority to its use in mobile telephones, superconducting magnets, of remaining production (Figure 12).
100%
90%
80%
n 70% o i t c
u 60% d o r p 50% g e a t n
e 40% c r e P 30%
20%
10% Figure 12 Global niobium production by country 0% 1 9 7 8 9 0 3 4 6 7 5 8 between 1997 and 2009. 2 0 0 0 9 9 0 0 0 0 9 0 0 0 0 0 0 9 9 0 0 0 0 9 0 0 0 2 2
Source: World Mineral 2 1 1 2 2 2 2 1 2 2 2 Statistics database, British Geological Survey. Brazil Canada Africa Niobium–tantalum
19 www.MineralsUK.com 20 Niobium–tantalum Geological Survey. Statistics database, British Source: World Mineral between 1997and2009. production bycountry Figure 14 Geological Survey. Statistics database,British 2009. Source:World Mineral ore) between1997and tantalum contentofmined production (basedonthe Figure 13 is avitalcomponentinwiderangeofconsumerproducts. tantalum isdrivenmainlybytheelectronicsindustrywhereit trates suchasstruveriteandcolumbite-tantalite.Demandfor remainder comesfromtin-slagmaterialandotherconcen- associated withtheprimaryoremineraltantalite,while 2009 (Figure13).Abouthalfofalltantalumproductionis tonnes; sincethenithasdeclinedtoabout900tonnesin Global tantalumproductionpeakedin2001atjustover2000 Tantalum production Global tantalum Global tantalum
Percentage production Tonnes Ta 1 1 1 2 2 1 2 3 4 5 6 7 8 9 0 5 0 5 0 5 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 % 0 % % % % % % % % % 0 0 0 0 %
1997 A 1997 u s t r
a 1998 1998 l i a
1999 1999
widespread althoughAfrica,predominantlyRwanda Unlike niobium,productionoftantalumismuchmore ume ofconflicttantalumenteringthemarketfromDRC. a resultoftheeconomicdownturn,andincreasedvol- and maintenanceduetothedropinpriceoftantalum,as mines, inAustralia.Theseoperationswereplacedoncare temporary closureofboththeWodgina andGreenbushes The recentdeclineintantalumproductionisrelatedtothe 2000 M 2000 a l a
y 2001 2001 s i a
2002 2002
2003 2003 B r a z
i 2004 2004 l
www.MineralsUK.com 2005 2005 C a n
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A 2008 2008 f r i c
a 2009 2009 and Democratic Republic of Congo, accounted for over Australia-based Gippsland Ltd is developing a huge 60 per cent of global tantalum production in 2009. In tantalum-tin resource in Egypt. The project includes the 2002 Australia produced about 60 per cent of global 44.5 million tonne Abu Dabbab deposit, scheduled for tantalum but this figure dropped to less than ten per cent production by 2013, and the 98 million tonne Nuweibi in 2009 due to the temporary closure of the Wodgina and project. The company plans to produce about 300 tonnes Greenbushes mines. Additional production comes mostly of tantalum pentoxide a year from its Abu Dabbab opera- from Brazil (about 20 per cent in 2009) with minor amounts tion (Gippsland, 2011). also produced in Malaysia and Canada (Figure 14). Globe Metals and Mining also plans to bring its Kanyika Projects under development project in Malawi into full production by 2013. The operation The growing markets for niobium and tantalum have led will produce approximately 200 tonnes of ferro-niobium, and to an increase in exploration for niobium and tantalum 190 tonnes of tantalum pentoxide per year. The operation in recent years. Many of the deposits being investigated will also produce by-product uranium oxide and zirconium contain both metals but, in many cases one is predomi- silicate (Schwela, 2010b). nant. Current exploration for both metals is focussed on carbonatite, peralkaline granite-hosted and LCT-type Australian company, Ram Resources Ltd, has acquired granite-hosted deposits (Table 8). 51 per cent of the Motzfeldt polymetallic deposit in south- ern Greenland. Motzfeldt has the potential to be a giant Global Advanced Metals (GAM), formerly Talison Metals, niobium-tantalum deposit with possible by-product rare has re-started mining at its Wodgina operation in Aus- earth elements. The overall resource could be in the region tralia. Tantalum pentoxide will be produced at Wodgina at of 500 million tonnes although further work is required to a rate of 318 tonnes per year, although at full capacity it define a JORC compliant estimate (RamResources, 2011). could be double that quantity. Material from Wodgina will be processed at Global Advanced Metals’ Greenbushes operation. Mining is not currently taking place at Green- World trade bushes (Schwela, 2010b). It is difficult to obtain trade data specific to niobium and tantalum as they are commonly reported under a combined
Deposit Location Company Type Resources* % Nb2O5 % Ta2O5 (Mt) Anita Canada Les Mineraux Carbonatite- 23.75 0.186 0.019 Crevier nepheline syenite Motzfeldt Greenland Ram Resources Alkaline-peral- 500 0.13–0.15 0.011–0.013 kaline granite Crevier Canada MDN Inc. Carbonatite- 25.4 0.2 0.023 nepheline syenite Kanyika Malawi Globe Metals Alkaline-peral- 21 0.41 0.018 and Mining kaline granite Abu Dabbab Egypt Gippsland LCT granite 44.5 n.a. 0.025
Nuweibi Egypt Gippsland LCT granite 98 0.0095 0.014
Marropino Mozambique Noventa LCT granite 7.4 n.a. 0.023
Upper Fir British Commerce Re- Carbonatite- 36.4 0.17 0.019 Columbia sources Corp. nepheline syenite *Includes all categories of resource
Table 8 Selected niobium-tantalum projects under development. (Schwela, 2010b, Gippsland, 2011, RamResources, 2011). Niobium–tantalum
21 www.MineralsUK.com 22 Niobium–tantalum in 2009(Papp, 2011a). Figure 15 overtaken Australia as exporters of tantalum, although this overtaken Australiaasexportersoftantalum,althoughthis South America(Brazil)andCentralAfricahaverecently ing countriesisnotavailable. States (Figure 15). Comparable data for other major import- suppliers ofniobiumoresandconcentratestotheUnited (48 percent)andCanada(32werethemain metal and86percentofitsniobiumoxide.Mozambique 69 percentofitsferro-niobium,91niobium In 2009,BrazilsuppliedtheUnitedStateswithabout United States,JapanandChina. cant importersofthesematerialsincludeGermany, the Canada isthesecondlargestexporterofniobium.Signifi form offerro-niobium,niobiumoxideandmetal. Brazil istheworld’s largestexporterofniobium,inthe other countries. and consequentlyitisentirelydependentonimportsfrom The EUdoesnotcurrentlyproduceanyniobiumortantalum efficiency andincreasedrecycling. of sustainabledevelopmentpractices,improvedresource gate againstthesesupplyrisks.Theseincludethepromotion on theEUeconomy. Strategiesarebeingconsidered tomiti- potential riskofsupplyshortagewithanassociatedimpact (EC., 2010).ThismeansthattheECconsiderstheretobea identified niobiumandtantalumas‘critical’rawmaterials tutes arenotavailable,theEuropeanCommission(EC)has ores, andbecauseformanyapplicationseffectivesubsti- Due toconcernsoverfutureaccessniobiumandtantalum ucts, oresandconcentrates,chemicals. Percentage Imports traded inavarietyofformsincludingmetallurgicalprod is compoundedbythefactthatniobiumandtantalumare trade codewithvanadiumandrhenium.Thisuncertainty 1 1 2 3 4 5 6 7 8 9 0 0 0 0 0 0 0 0 0 0 0 0 Sources ofUnited Statesniobiumimports Brazil Mozambique Ore andConcentrate Niobium oxide Niobium Metal Ferro-niobium Canada
- - powder inexcess ofUS$300perpound(Reisman, 2011). about US$240per pound;andcapacitor-grade tantalum was aboutUS$120perpound; tantalumoxidesandsalts ferent price:inFebruary2011 tantalum oreandconcentrate Tantalum istradedinthreeforms,eachcommandingadif- Burns, 2009). possibly duetoincreaseddemand(RamResources,2011, were reportedtobeaboutUS$3941perkilogram, to 14perkilogram.However, asofFebruary2011,prices Prior to2007ferro-niobiumpriceslayintherangeUS$12 prices basedoninterviewswithbuyersandsellers. confidential. Trade journalssometimes reportindicative negotiated betweenbuyerandsellergenerallyremain openly tradedonanymetalexchange;contractpricesare Unlike manyothermetalsniobiumandtantalumarenot Prices Portugal (14percent)(Figure16). came fromChina(15percent),Germany(12cent)and cent); tantalumscrapimportsintotheUnitedStates cent), Kazakhstan(27percent)andGermany(15 tantalum metaltotheUnitedStateswereChina(27per supplied afurther21percent.Themainexportersof 66 percentofitstantalumconcentratewhilstCanada In 2009,AustraliasuppliedtheUnitedStateswithabout slags totheEUincludeJapan,ChinaandKazakhstan. Currently themainexportersoftantalumores,scrap,andtin are intheformoftantalumoxideoraspotassiumsalt. Germany, JapanandChina.Themajorityoftantalumexports tantalum manufacturingandprocessingwasteincluding Greenbushes mines.Anumberofcountriescurrentlytrade is likelytochangewiththere-openingofWodgina and in 2009(Papp,2011b). Figure 16 Percentage Imports 1 2 3 4 5 6 7 0 0 0 0 0 0 0 0 A u s t r a Sources ofUnitedStatestantalumimports l i a C a n a d a C h i n a www.MineralsUK.com K a z a k h s t a n G e r m S M C a c o e n r n t a y a c p l e n t P r a o t r e t u ga l Recycling and substitution Focus on Britain Recycling Niobium and tantalum have never been commercially Both niobium and tantalum can be recovered from waste exploited anywhere in Britain, and there has been no metals and scrap and in both cases account for up to systematic evaluation of niobium and tantalum resources. 20 per cent of total supply (EC., 2010). Niobium is primar- Locations of potential interest are confined to alkaline and ily recovered from niobium-steels and superalloys, but the associated igneous rocks which are relatively rare in the amount recovered from other sources is minor. Tantalum UK. is recovered from a number of different items including cemented carbides and alloys; however, recycling from ca- Carbonatites and associated rocks pacitors is difficult and current technology is poorly devel- The only confirmed carbonatite body in the UK is associ- oped. Other items from which tantalum can be recovered ated with the Silurian89 alkaline Loch Borralan Complex include spent sputtering targets88, and edge trimmings and in the north-west Highlands of Scotland. The whole of shavings from metallurgical processes. the Loch Borralan Complex (including the carbonatite and associated ultramafic rocks) has generally low bulk-rock Substitution niobium contents, and niobium-bearing minerals such as Many of the uses of niobium and tantalum are very specific pyrochlore are not present (Young et al., 1994). and substitutes often incur a cost or performance penalty. Due to the physical and chemical similarities of niobium Carbonate veins and evidence of sodium metasomatism and tantalum the two metals can be substituted for each (fenitisation) have been found at several localities along other in a number of applications, for example, in corro- the Great Glen Fault near Inverness, and have been at- sion- resistant coatings. Where strength at high tempera- tributed to carbonatitic magmatism. Bulk-rock analyses ture is required in steel, metals such as molybdenum and indicate that niobium contents in the carbonate and fenite vanadium are often used as substitutes for niobium and veins are higher than in the surrounding country rocks, tantalum. Efforts are currently being made to substitute but niobium-bearing minerals such as pyrochlore have tantalum by aluminium or ceramics (Table 9 and 10). Some not been found (Garson et al., 1984). These veins are of applications are unique and as such suitable substitutes relatively limited extent, but it is possible that a larger are currently not available, for example, porous tantalum carbonatite mass may exist at depth. alloys used in the manufacture of prosthetic body parts. Alkaline to peralkaline granites and syenites Niobium product/ Possible substitutes Alkaline igneous rocks in the British Isles were formed dur- application ing three main magmatic episodes: the Caledonian mag- HSLA steels Molybdenum and vanadium matism (Silurian to Devonian); the Permo-Carboniferous90; 91 Stainless and high- Tantalum and titanium and the Palaeogene . strength steels Caledonian igneous rocks are widespread, but the vast High-temperature Ceramics, molybdenum, tantalum applications and tungsten majority are calc-alkaline in composition. A suite of alkaline, largely syenitic, plutons occurs in the north-west Table 9 Potential niobium substitutes. (Papp, 2011a). Highlands of Scotland, but all these intrusions are char- acterised by low bulk-rock niobium contents (Fowler et Tantalum product/ Possible substitutes al., 2008). Niobium- and tantalum-bearing minerals have application not been recognised in these syenites. In Wales, Ordovi- Capacitor manufacture Aluminium and ceramics cian to Silurian alkaline microgranites with relatively high Carbide material Niobium bulk-rock niobium contents (up to 150 ppm) occur both in production Snowdonia and the Llyˆn Peninsula. The Mynydd Mawr Corrosion-resistant Glass, niobium, platinum, microgranite in Snowdonia has been reported to contain equipment titanium and zirconium niobium and tantalum minerals (Bevins and Mason, 2010, High-temperature Hafnium, iridium, molybdenum, Young et al., 2002). applications niobium, and tungsten
Table 10 Potential tantalum substitutes. (Papp, 2011b). 89 Silurian: a unit of geological time between 443 and 416 million years ago. 90 Permo-carboniferous: a unit of geological time around 300 million years ago 88 Sputtering target: metallic materials used as targets for the deposition of that represents the end of the Carboniferous and the start of the Permian. 91
Niobium–tantalum thin-films of tantalum compounds (e.g. tantalum carbide). Palaeogene: a unit of geological time between 65 and 23 million years ago. 23 24 Niobium–tantalum tholeiitic and intoNorthernIreland.Themajorityoftheserocksare western sideofBritain,fromtheBristolChanneltoStKilda The BritishPalaeogeneigneousprovinceextendsalongthe ed througheithermagmaticorhydrothermalprocesses. are norecordsofniobium-bearingmineralsbeingconcentrat- niobium contents,upto180ppm(Uptonetal.,2007),butthere These trachyticigneousmasseshaverelativelyhighbulk-rock central Scotland,whicharetypicallytrachytic not beeninvestigatedindetail(IGS,1975). sediment samples,butthesourceofthesemineralshas ilmenorutile andcassiteritehavebeenfoundinstream- the CairngormGraniteinScotland,fergusonite,columbite, has alsobeendescribedfromtheseveins(Young, 1987).In mineral veinsoccurwithintheSkiddawGranite;columbite age. AtCarrockFellintheLakeDistrict,tungsten–bearing LCT-type mineralisationisrareingranitoidsofCaledonian minerals havenotbeenrecordedelsewhereinthisarea. plex ofnorth-westernScotland,butniobiumandtantalum occur acrossmuchoftheArchaeanLewisianGneissCom (von-Knorring andDearnley, 1960).Pegmatitesofthisage for alkalifeldspar, alsocontainscolumbite andpyrochlore Chaipaval pegmatite,whichhaspreviouslybeenquarried ing muscovite,biotite,berylandraretourmaline.The These havetypicalLCTmineralassemblages,includ occur ontheislandofSouthHarris,inOuterHebrides. A numberoflargePalaeoproterozoicgraniticpegmatites Granites andpegmatitesoftheLCTfamily been reportedfromtheLundyGranite(Thorpeetal.,1995). in miarolitic reported fromthenorthernArrangranite,whereitoccurs sonite, aniobium-andtantalum-bearingoxide,hasbeen moderate bulk-rockniobiumcontents(<50ppm).Fergu- element dataforthesegranitesgenerallyindicatelowto evolved rocksarepresent,chieflyasgraniticplutons. Trace surface. ago. granitic pegmatites. formed intheoceans oratcontinentalmargins. a mineralcalledalkalifeldspar;thefine-grained equivalentofsyenite. which iscircularinplan,withaflatfloor andashallowdomedroof. Scotland andnorthernEnglandduringtheCarboniferous Alkaline magmatismwasextensiveincentraltosouthern 97 96 95 94 93 92 form asetofsmallplugs are maficvolcanicrocks.Morehighlyevolvedmagmaticrocks Permian periods,butthemajorityofexposedigneousrocks
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