Abstract
Corundum is not uncommon on Earth but the gem varieties of ruby and sapphire are relatively rare. Gem corundum deposits are classified as primary and secondary deposits. Primary deposits contain corundum either in the rocks where it crystallized or as xenocrysts and xenoliths carried by magmas to the Earth’s surface. Classification systems for corundum deposits are based on different mineralogical and geological features. An up-to-date classification scheme for ruby deposits is described in the present paper. Ruby forms in mafic or felsic geological environments, or in metamorphosed carbonate platforms but it is always associated with rocks depleted in silica and enriched in alumina. Two major geological environments are favorable for the presence of ruby: (1) amphibolite to medium pressure granulite facies metamorphic belts and (2) alkaline basaltic volcanism in continental rifting environments. Primary ruby deposits formed from the Archean (2.71 Ga) in Greenland to the Pliocene (5 Ma) in Nepal. Secondary ruby deposits have formed at various times from the erosion of metamorphic belts (since the Precambrian) and alkali basalts (from the Cenozoic to the Quaternary). Primary ruby deposits are subdivided into two types based on their geological environment of formation: (Type I) magmatic-related and (Type II) metamorphic-related. Type I is characterized by two sub-types, specifically Type IA where xenocrysts or xenoliths of gem ruby of metamorphic (sometimes magmatic) origin are hosted by alkali basalts (Madagascar and others), and Type IB corresponding to xenocrysts of ruby in kimberlite (Democratic Republic of Congo). Type II also has two sub-types; metamorphic deposits sensu stricto (Type IIA) that formed in amphibolite to granulite facies environments, and metamorphic-metasomatic deposits (Type IIB) formed via high fluid–rock interaction and metasomatism. Secondary ruby deposits, i.e., placers are termed sedimentary-related (Type III). These placers are hosted in sedimentary rocks (soil, rudite, arenite, and silt) that formed via erosion, gravity effect, mechanical transport, and sedimentation along slopes or basins related to neotectonic motions and deformation.
Highlights
Ruby is the red gem variety of the mineral corundum
Thseupnlrieghset,nanced tohfisCmraaktesththee roucbtya’hs ecodlorar ml soirteeinatlesnoseg,iivncersearsiisnegtitos vsatrluoen. gThflisuflouroersecsceenncceeiws shomenetitmheesstone is exposedobtsoeruvletdrainvisomleatlllpiginhktis(h36ru5bniems, )fr.oTmhme ainrbtleendseiptyosoitfs,flthuaotrceosncteainncleittilse atofunoncirtoion,ninocfluCdrincgotnhcoesentration and thetrCadr/itFioenraalltyiofr[o4m3],Mbyeacnamuasre(tMhoegpokr,esMenoncge oHfsuF,e aonrdaNnaemxycae)s, saondf CrercteenntlydsfrtoomelVimietinnaamte aonrdquench the fluoArefgshcaenniscteanin[44r]u. bSoym. eInrubsioems feromstoanmepsh,ibtholeitefl(uMoorzeasmcbeinqcuee)caannd aelvkaelni-bbaesalstes e(Tnhawilahnedn) heaxvpeoaslseod to the ultraviobllaeebetonrcadoteomsrcipreisobelnidmeanitstt“ihpneiigrseuuonnse’lsiogbfhlottho,eda”tneirdnmltahtboiosrsatmrtooarnykglreyespftoluhrotesrebrsuuctebtnyhti’ssruicsbocieolsonrt(rwomhvieocrhrseiamilnebateencasnustsheee, milnoowcsrt-eirreaopsnuinttyagpbleiet, s value. This fluorescence is sometimes observed in small pinkish rubies, from marble deposits, that contain little to no iron, including those traditionally from Myanmar (Mogok, Mong Hsu, and Namya), and recently from Vietnam and Afghanistan [44]
The Ga/Mg ratio is highly variable, between 0.1 and 10, and some rubies such as those occurring as xenocrysts in alkali basalt (Chanthaburi-Trat and New England) and mafic and ultramafic rocks (M-ultramafic rock (UMR)) (Madagascar) plot in the magmatic field of sapphire
Summary
Ruby is the red gem variety of the mineral corundum. The name corundum was introduced in the early 19th century by French mineralogist De Bournon when gemmological terminology was transformed. Origin determination was introduced by Eduard Gübelin who worked on inclusions in gems using mainly microscopy [16,17], and Raman and infrared spectroscopy Such techniques are usually suitable for high value large rubies (that are usually never really free of mineral inclusions) but find their limits in the case of small clean stones or for heated stones (with inclusions that have been altered or even melted by heat treatment). EInrubsioems feromstoanmepsh,ibtholeitefl(uMoorzeasmcbeinqcuee)caannd aelvkaelni-bbaesalstes e(Tnhawilahnedn) heaxvpeoaslseod to the ultraviobllaeebetonrcadoteomsrcipreisobelnidmeanitstt“ihpneiigrseuuonnse’lsiogbfhlottho,eda”tneirdnmltahtboiosrsatmrtooarnykglreyespftoluhrotesrebrsuuctebtnyhti’ssruicsbocieolsonrt(rwomhvieocrhrseiamilnebateencasnustsheee, milnoowcsrt-eirreaopsnuinttyagpbleiet, s value This fluorescence is sometimes observed in small pinkish rubies, from marble deposits, that contain little to no iron, including those traditionally from Myanmar (Mogok, Mong Hsu, and Namya), and recently from Vietnam and Afghanistan [44]. Fcoirrsetlfyo, rthmeecdoruenfdoermr leodwunddrievrinlogw-fodrrciveincogn-fdoirtcieoncosnvdiaitiloanyserv-ibayl-alyaeyre-rbyg-rloaywetrhg(rSotwepth1()S.tIetps 1d)e.vIetlospdmeveenltowpmasenhtinwdaesrehdinbdyertehde brayptihdefroarpmidatifoonrmoaftsioenctoorf sbeocutonrdabroiuesn,dwarhiiecsh, wenhvicehlopenevdeiltopaned ictoannstditcuotenstthietu“tsektehleto“snk”eoleftothne”torafpthicehetrraupbicyh(eStreupby2)(.STtehpes2e).boTuhnedsearbieosufnodrmareieds wfohremnetdhewdhreinvinthgedforricveincgo-nfodrictieoncosnidncitrieoanssedinacnredasaeddheasnidvea-dtyhpeesigvreo-wtytphetgorookwptlhacteo.oFkinpalallcye,.aFdineaclrleya, saedinectrheeasderivninthgedforrivceincgo-nfodrictieocnosnadlliotiwonesdatlhloewfoerdmtahteiofnoromf gartioowntohfsgercotowrtshasnedcttohrescaonrdretshpeocnodrirnegspcorynsdtianlgfaccreyssthalrofaucgehs tohrrdoiunagrhyolradyienra-rbyy-llaayyeerr-bgyr-olwaytehr (gSrtoewp t3h).(STtheep g3r).owThthe gseroctworths fsielcletdorsthfielliendtetrhseticinetselresftticbeys ltehfet bsyectthoer sbeocutonrdbaoryu,ncdoamryp,lceotimngpltehteintgratphiechtreapteixcthuertee.xture
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
