Flux Heated and Glass Filled Rubies From Mozambique

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Transcript of Flux Heated and Glass Filled Rubies From Mozambique

FAPFH/GFFTreatedRubyfromMozambique apreliminaryreportVincentPardieu,NickSturman,SudaratSaesaew,GarryDuToit,KamolwanThirangoon GIALaboratory,Bangkok.(May11,2010)

Figure1:Thethreedifferentpowdersusedintheprocess,remnantsofaceramiccrucibleandsomeoftheuntreatedand treatedsamplesexaminedinthisstudy.Photo:N.Sturman.

Introduction: AfterthediscoveryoftheMontepuezrubyminingareainMozambique,duringspring2009(Pardieu,etal.,2009a),within fewmonths,gemologistsattheGIALaboratoryBangkokstartedtoseemanystonesoriginatingfromthisnewdeposit. Manyunheatedstonesweresubmittedforexamination,butthiswasquicklyfollowedbymaterialthathadbeenheatedat hightemperatureusingafluxassistedpartialfissurehealing(FAPFH)processthatappearedsimilartothatwhichhas beenusedonthematerialfromMongHsu(Burma)sincetheearly1990s.InDecember2009theauthorsbeganto collaboratewithThawatchaiSomjainuek,whohadbeendevelopingatreatmentprocesssimilartothatusedontheMong HsumaterialforthematerialfromMontepuez. Afterstudyingnumeroustreatedrubiesfromthisnewdeposittheauthorsobservedthatinmanycasesinadditiontothe usual(forMongHsumaterial)partiallyhealedfissures,thestonesalsocontainedavariablenumberofsurfacereaching fissuresthatwerenotpartiallyhealedandweresimplyfilledwithglass(GFF)similartothefissurefillingseenintheso calledleadglassfissurefilled(LGFF)rubiesanddiamondswherefissureshavebeenfilledwithglass.Inthecaseoftreated rubiesfromMongHsuthathaveundergonetheFAPFHprocess,whiletheobservationofglassfilledsurfacecavitiesisnot unusual,unhealedfissuresthatarefilledwithglass(GFF)are.

PardieuV.,Sturman,N.,Saesaew,S.,Thirangoon,K.,DuToit,G.(2010)FAPFH/GFFTreatedRubyfromMozambiqueapreliminaryreport.May11,2010. http://www.giathai.net/lab.php

WhiletheglassthatfillsunhealedfissuresintheMontepuezrubiesdoesnotcontainsignificantquantitiesofleadasinthe LGFFrubies,theintentofthetreatmentisthesameandtheresultsandeffectsareatleastsimilar.Therefore,inmany situationswiththeserubiesthetreatmentprocessresultsintwoseparatelydefinedtreatmenttypeswithinasinglestone FAPFHandGFF. AttheendofMarch2010theGIAlaboratoriesinBangkok,CarlsbadandNewYork,begantoissuereportsforthese multipletreatmentrubiesusingwhereappropriatetheTEscale(SeeLMHCInformationSheet#1)todescribetheeffectsof theFAPFHprocesstogetherwiththeclarityenhancementstatementsalsousedfortheeffectsoftheLGFFprocess. ItisimportanttoreiteratethattheglassfoundintheseGFFrubiesdoesnotcontainasignificantamountofleador bismuth,nevertheless,itisstillaglassandthusincomparisontotherubyitself,maybeunstableatelevatedtemperatures andtochemicalagents.SpecialcareshouldbetakenwhencleaningorreparingjewelryitemssetwithGFForLGFF corundum.

Keyacronyms: FAPFHFluxAssistedPartialFissureHealing GFFGlassFissureFilled ISLMHCInformationSheet LGFFLeadGlassFissureFilled LMHCLaboratoryManualHarmonizationCommittee

Historicalbackground: GlassfillingofcavitiesinThairubyandlatersapphirewasfirstreportedduringtheearly1980s.(Hughes,1984,Scarratt,et al.,1984).Intheensuingyears,glassfillingwascommonlyseeninrubiesfromtheMorogororegioninTanzaniaandtoa lessextentinstonesfromMogok(Burma)(Pardieu,etal.,2006). Intheearly90sThairubydealersplacedmostoftheirfocusontheMongHsudepositasanewtreatmentprocess,FAPFH, wasabletotransformthismaterialfromunsalablenearopaqueroughintowonderfultransparentfacetedredgems.The FAPFHprocesswasclearlysetoutbyHnniinadiagrammaticformthatisreproducedhere(withpermission)ontheleft sideofFigure2.Inshort;rubyisheatedtotemperaturesthatmayreachashighas1850Cinthepresenceofamoltenflux. Atthesetemperaturesthesurfacesoftheruby(alumina)incontactwiththefluxwillslowlydissolveintotheflux.During thegradualcooldownperiodthealuminacomesoutofthefluxandcrystallizesonthenearestavailablesurfaces.These surfacesmaybethoseofthecrucibleinwhichtheprocessistakingplaceorontherubiesbeingtreated.Ifcrystallization takesplaceontherubies,thismaybeontheoutersurfaces(facets)ofthestonesorontheinnersurfacesofanyfissures thatmaybepresent.Ifthecrystallizationisontheinsideoffissures,thebuildupofsyntheticmaterialwillcausethe fissurestograduallycloseorpartiallyheal(Figure2).Thesepartiallyhealedfissureshavetheappearanceofintricate networksoffinetubulescontainedinundulatingplaneswithinthestone.Thematerialthatcanbeobservedwithinthese planesismostlycomposedofaglass;thetransparentspaceswithintheplanesarewherethefissureshavebeenpartially healedwithsyntheticcorundum.

PardieuV.,Sturman,N.,Saesaew,S.,Thirangoon,K.,DuToit,G.(2010)FAPFH/GFFTreatedRubyfromMozambiqueapreliminaryreport.May11,2010. http://www.giathai.net/lab.php

a

b

Figure 2: Flux assisted healing of a fissure during the heating process. A fissure that has been healed by the synthesis of corundum or other materials during the heat treatment or crystal growth processes. (Hnni, H.A., 1998) (a) schematic (b) actual

UponformationoneofthefirsttasksthattheLMHC undertookwastoaddressthevariedtextsusedtodescriberubies thathaveundergonetheFAPFHprocess.TheLMHCInformationSheet#1(IS1)setsouttheagreednomenclature.Table1 setsoutthisthebasicLMHCnomenclatureforFAPFHtreatedrubies;readersareadvisedtodownloadandreadtheentire IS1forcontext.

1

Table1:LMHCResidueQuantificationterminologyforfluxhealedrubies.Condition Noindications ofheating Indicationsof heating(no residue) TE Indicationsofheatingwithresiduesinfissures

Report Alpha numeric Report Text

NTE

TE1

TE2

TE3

TE4

TE5

Noindications ofheating

Indicationsof heating

Minorresidueinfissures

Moderateresiduein fissures

Significantresiduein fissures

Condition Report Alpha numeric Report Text

Indicationsofheatingwithresiduesincavities C1 C2 C3

Minor Residueincavities

Moderate Residueincavities

Significant Residueincavities

In2000,ThaitradersstartedtobuylargequantitiesofrubiesfromAndilamenaandVatomandryinMadagascar.After severalyearsofexperimentssomeThaiburnerswereabletoadapttheclarityenhancementtechniquesdevelopedbythe YehudaCompanyforDiamondsinthe1980storubiesfromAndilamena;amaterialwithagoodshapeandcolorbut usuallyheavilyfissured.In2004,largequantitiesofLGFFrubiesfromAndilamenaappearedinthemarket(GAAJ,2004, Pardieu,2005).WhileFAPFH,LGFFandGFFstonesallresultinstonesthathavebeenclarityenhanced,theessential differencebetweenthethreetypesoftreatmentisthatthefissuresinFAPFHtreatedmaterialarehealedclosedby synthesiswhilefissuresineitherLGFForGFFarenot,i.e.,FAPFHfissuresarestable(onceanysurfaceglasshasbeen removedbyHF)whereasLGFFandGFFtreatedfracturesunstable(theywillbreakdownandbecomeobviouslyvisible), 1

The Laboratory Manual Harmonisation Committee (LMHC) is comprised of representatives from the following gemmological

laboratories located in Europe, America and Asia: CISGEM, GAAJ, GIA , GIT, Gbelin, SSEF

PardieuV.,Sturman,N.,Saesaew,S.,Thirangoon,K.,DuToit,G.(2010)FAPFH/GFFTreatedRubyfromMozambiqueapreliminaryreport.May11,2010. http://www.giathai.net/lab.php

(McClure,2006,Scarratt,2009).InseverecasesofLGFFtreatedrubiestheLMHClaboratoriesdevelopedseverelyworded descriptions;thesearerubywithglassandrubyglasscomposite. FollowingthediscoveryoftheWinza(Tanzania)depositinNovember2007(Pardieu,2008,Schwarz,etal.,2008)twonew rubydepositsinMozambiquewerediscovered.ThefirstwasnearMsawizevillage(Oct.2008)intheNiassaprovince (Pardieu,etal.,2009b)andthesecondwasnearthetownofMontepuez(April2009)intheCaboDelgadoprovince (Pardieu,etal.,2009a).LargequantitiesofthislattermaterialenteredThailandin2009. InSeptember2009inMozambique,oneoftheauthors(VP)metThaidealersfamiliarwiththeproductionfromthetwo deposits(NiassaandMontepuez).TheyreportedthatthebestunheatedmaterialwascomingfromNiassa,however, mostoftheproductionfromthisdepositwasonlysuitableforLGFFtreatment.Ontheotherhandmostofthe productionfromMontepuezcouldbetreatedusingaFAPFHprocessverysimilartotheprocessusedfortheheat treatmentofrubiesfromMongHsu.NeverthelessinNovemberwhilebackinThailandotherThaidealersexpressedtheir concernthattheaverageclarityoftheFAPFHtreatedMozambiquematerialwaslowerontheTEscalecomparedtothe averageMongHsumaterial.Theyfeltthatthiswasduetothematerialbeingmoreincludedandthepresenceoflarge fissureswhicharelesscommonintheMongHsumaterial. InDecember2009,whileVPwasvisitingtheMontepuezrubydeposittocollectreferencesamplesatthemines,theother authors(NS,GD,SS,KT)beganworkingincollaborationwithThawatchaiSomjainuek(KhunTai)whowastreating MozambiquematerialusingaderivationoftheFAPFHprocess.

AboutThawatchaiSomjainuek: ThawatchaiSomjainuek(KhunTai)isaThaicitizenwhointhe90swasveryactiveinthetreatmentofcorundum.He workedwithyellowsapphirefromSriLankaandthenwithsapphirefromMadagascar.Heisfamousforthediscoveryin 1995oftheberylliumtreatmentprocess;however,hedecidedtosuspendallhistreatmentactivitiesafterexperiencing someillfeelingstowardshisinvolvementinthistreatmentprocess. Herecentlydecidedtoreactivatehistreatmentactivities.However,inanattempttoensurethatheremainstransparent abouthisprocesses,thematerialsandresults,Somjainuekhastakentheunusualandpraiseworthystepofworkingwith theGIALaboratory,Bangkok,toensurethateachstepinhistreatmentprocessisrecordedandanalyzedsoastoavoidany complicationswhenthematerialismarketed.Oneofhismainconcernswasensuringthatnoberylliumwasinvolvedin hisprocessandthattherewerenoadditionalsurprises.

TheSomjainuektreatmentprocess: TheaimofthetreatmentcarriedoutbySomjainuekistoturnroughlowqualityrubywithacommensuratelowermarket valueintoamoresaleableproduct.Priortotreatmenttheroughispreformedandcleanedusingasolutionofdilute hydrofluoricacid(water1:1)for3days.Hethenheatsthematerialtostatedtemperaturesof1400Cforaround20hours inacontrolledoxidizingenvironment.Togetherwiththerubies,whichareheldinceramiccruciblesduringtheprocess,are boraxandsilica.Inthevolatileatmosphereofthecruciblethemoltensilicarichfluxcoverseverysurfaceoftherubiesand penetratesallthenumeroussurfacereachingfis