substratenation

LABNOTESGEMS&GEMOLOGYSPRING200953CUBICZIRCONIAReportedlyCoatedwithNanocrystallineSyntheticDiamondIthasbeentwodecadessinceG&Gfirstreportedoncubiczirconiawithathickdiamond-likecoating(Spring1987GemNews,p.
52)andE.
Fritschetal.
commentedontheremotepossi-bilityofgrowingathinnermono-crystallinefilmoncubiczirconia(CZ)thatwouldgivethethermalconductiv-ityofdiamond("Apreliminarygemo-logicalstudyofsyntheticdiamondthinfilms,"Summer1989G&G,pp.
84–90).
Recently,theGIALaboratoryhadtheopportunitytostudysomenew,commerciallyavailablesamplesofcubiczirconiareportedtobecoatedwithnanocrystallinesyntheticdia-mond(typicallydefinedashavinggrainsizeslessthan500nm).
SerenityTech-nologies(Temecula,California)andZirconmania(LosAngeles)suppliedthelabwithmaterialtheymarketasEternityCZandDiamond-Veneer,respectively.
TheSerenityTechnologieswebsiteclaimsitis"virtuallyimpossibletovisuallyidentifyEternityCZasany-thingbutadiamond.
TheonlywaytopositivelyidentifyEternityCZisbyitsweight,hardnessandchemicalcompo-nent"(www.
serenitytechnology.
com).
ItalsostatesthattheRIanddispersionchangeduetothenanocrystallinedia-mondcoating.
ZirconmaniamakessimilarclaimsaboutDiamond-Veneer(http://diamondveneer.
net).
Weexamined14roundbrilliantsamplesfromSerenity(0.
29–0.
32ct;e.
g.
,figure1)andfourfromZircon-mania(0.
13–2.
36ct).
SeventeenofthespecimenscorrespondedtotheDrangeontheGIAdiamondcolorgradingscale;thelastwasequivalenttoanE.
Alltheanalysesweperformedsuc-cessfullyidentifiedthesamplesasdia-mondsimulants.
Microscopicexami-redTag"style="COLOR:#000000;BACKGROUND-COLOR:#ffff00">nationwithdarkfieldillumiredTag"style="COLOR:#000000;BACKGROUND-COLOR:#ffff00">nationrevealedtheorangepavilionflashtypi-calofCZ.
Allalsotestedas"notdia-mond"withathermalconductivitydiamondtesterandtheDiamondSureinstrument.
Allthespecimensshowedchips,invarioussizes,whichappearedconchoidal,notstep-likeasonemightexpectfordiamond.
Additionally,allthesamplesrevealedthepresenceofacoatingonthecrownandpavilionwhenviewedinreflectedlight(figure2).
Thecoating'sappearancevariedwithinfacetsandparticularlyatthe2009GemologicalInstituteofAmericaGEMS&GEMOLOGY,Vol.
45,No.
1,pp.
53–58.
Editors'note:AllitemsarewrittenbystaffmembersoftheGIALaboratory.
Figure1.
This0.
31ctcubiczirco-niafromSerenityTechnologiesisreportedlycoatedwithnanocrys-tallinesyntheticdiamond.
Figure2.
Inreflectedlight,thecoatingonthesurfaceofthis2.
36ctcubiczirconiaisclearlyvisible.
Also,thechipslookconchoidal,incontrasttothetypicalstep-likeappearanceofdiamond.
Fieldofview1.
7*1.
3mm.
EditorsThomasM.
MosesandShaneF.
McClureGIALaboratory54LABNOTESGEMS&GEMOLOGYSPRING2009facetjunctions.
Finally,thecoatingcouldbescratchedwithacorundum(Mohs9)hardnesspoint—therefore,itdidnotseemtoaddsignificantlytotheCZ'sdurability.
SGvaluesrangedfrom5.
91to5.
96,ascalculatedbytheDiaVisionnoncontactmeasuringdevice.
ThisrangecoincideswiththereportedSGof5.
95foryttrium-stabilizedCZ(M.
O'Donoghue,Ed.
,Gems,6thed.
,Butterworth-Heinemann,Oxford,UK,2006).
WewereunabletomeasuretheRIofthecoatedCZsusingastandardgemologicalrefractometer,but"read-through"observations,whichprovidearelativeapproximationofRI,yieldedresultsmoreconsistentwithCZthandiamond.
Raman,photoluminescence(PL;at325,488,514,and830nmlaserexcita-tions),andFourier-transforminfrared(FTIR)analysesusingstandardtech-niquesrevealednopeaksassociatedwithdiamond.
TheRamanandFTIRspectramatchedthoseofCZ.
Al-thoughwehavenotyethadanoppor-tunitytodeterminethethicknessofthecoating,itappearstobetoothintocontributesignificantlytothespectradominatedbytheunderlyingmaterial.
TheresultsofourtestsestablishthattheseEternityCZandDiamond-Veneersamplesareeasilyseparatedfromdiamond.
Characterizationofthecoatingmaterialisthefocusofongoingresearch.
Ifthecoatingmaterialisnanocrystallinesyntheticdiamond,itdoesnottakemuchimagiredTag"style="COLOR:#000000;BACKGROUND-COLOR:#ffff00">nationtopre-dictthatnaturaldiamond,insteadofCZ,mightbeusedasafuturesubstratematerialtoimprovetheappearanceorthecolorofthestone(see,e.
g.
,Summer1991GemNews,pp.
118–119).
Shouldsuchatreatmentbecomecommercial-lyavailable,itcouldbefarmorediffi-cultforgemologiststoidentify.
SallyEaton-MagaaandKarenM.
ChadwickDIAMONDAssemblagesofK-Feldspar,Hematite-Magnetite,andQuartzinEtchChannelsMostmineralsseenindiamondoccurassinglecrystals.
Rarelyhaveweencounteredinclusionsofmineralassemblagesformedatconditionsoutsidethediamondstabilityfield.
Recently,theNewYorklaboratoryexaminedagroupoffivediamonds(1.
67–3.
70ct)submittedtogetherbyasingleclient.
Thesestonescontaineddarksectorialclouds,aswellasnumerousetchpitsandetchchan-nels.
ThreeofthediamondswerecolorgradedFancyblack,andtheothertwoweregradedFancyDarkbrown.
Infraredspectroscopyshowedarelativelyhighconcentrationofhydrogeninallthestones,whichisthelikelycauseofthesectorialcloudsthatproducedthedarkcolors.
Ofgreatestinterestweretheassemblagesofmineralinclusionsseenintheetchpitsandchannelsofallthediamonds.
Microscopicexami-redTag"style="COLOR:#000000;BACKGROUND-COLOR:#ffff00">nationrevealedtheseasopaquedarkbrown,transparentgray,andtranspar-entnear-colorlesstowhitematerials.
Thelargestassemblage(~1.
1*0.
5*1.
0mm)—observedina2.
46ctovalmodifiedbrilliant-cutFancyblackdia-mond(figure3)—consistedoffourminerals(figure4)inanetchchannelthatbrokethesurfaceatthecrownshoulder.
Ramanspectroscopyidenti-fiedtheopaquedarkbrownportion,whichmadeupmostofthisassem-blage,asamixtureofhematiteandmagnetite.
Thebottompartofthismixturewastotallyenclosedinthediamondandshowedwell-formedsteppedsurfaces.
ThetransparentgrayinclusionswereidentifiedasK-feldspar,andthewhiteinclusionswerequartz.
A1.
67ctcut-corneredrectangularstep-cutFancyDarkbrowndiamondcontainedanassemblagealmostaslarge(~0.
9*0.
6*0.
5mm),whichbrokethesurfaceofthepavilionnearacorner.
Ramanspectroscopyidenti-fiedthisassemblageasamixtureofhematite-magnetiteandquartz.
Thepresenceofdarksectorialcloudsinallfivestonessuggestedthatthesediamondscouldhaveformedinasimilarenvironment.
SincequartzandK-feldsparwouldnotbestableinthehigh-temperatureandhigh-pres-Figure3.
This2.
46ctFancyblackdiamondcontaineddarksectori-alcloudsaswellasassemblagesofmineralinclusions,whichformedinetchchannels.
Figure4.
Thisassemblageofhematite-magnetite,K-feldspar,andquartzcrystallizedinanetchchannelofthediamondinfigure3assecondaryinclusions.
Theorangecolorislikelyduetoironstainingfromweatheringoftheiron-bearinghematite-mag-netite.
Fieldofview0.
8mm.
QuartzK-feldsparHematite-magnetiteLABNOTESGEMS&GEMOLOGYSPRING200955surestabilityfieldofdiamond,theseassemblagescouldonlyhaveformedatconditionsoutsidethediamondsta-bilityfield,suchaswithintheconti-nentalcrust,wherethesemineralsarestable.
Furthermore,thewell-devel-opedcrystallinequalityandmorphol-ogyoftheseincludedmineralssuggestformationandgrowthafterthedia-mondwasbroughttoarelativelyshal-lowdepthintheearth.
Mostofthemineralinclusionsweobserveinthelaboratoryareprotoge-neticorsyngeneticinclusionsformedwithinthediamondstabilityfield.
Theseassemblagesprovideexcellentexamplesofepigeneticmineralinclu-sionsthatformedoutsidethedia-mondstabilityfieldandaretypicallyassociatedwithcrustalprocesses.
WaiL.
WinandRenLuClarityGradingRadiationStainsRadiationstainscanappearasgreenorbrownpatchesindiamond.
Theyaretypicallyassociatedwithnaturals,indentednaturals,feathers,oretchfeatures,andarethoughttobecausedbyexposuretoradioactiveelementsinanear-surface,low-temperatureenvi-ronment.
Radiationstainsaregreenwhentheyformandcanturnbrownifthediamondissubjectedtorelativelyhightemperatures,suchasthosethatoccurduringthepolishingprocess.
Theirimpactonadiamond'sclaritygradedependsonwhetherornottheypenetratethesurfaceofthestone.
Recently,theNewYorklaboratoryexamineda1.
01ctroundbrilliantcutsubmittedforgrading.
Anetchchannelextendedintothediamondfromabezelsurface;itwasidentifiablebyitsdistinctelongatedformandangularoutline,aswellasthegrowthmark-ingsalongitsedges(figure5).
Sphericalbrownzoneswerevisiblereachingbeyondtheetchchannelintwoareas.
Theirunusualappearance,color,andrelationshiptotheetchchannelimme-diatelyidentifiedthemasradiationstains.
Theyprobablyformedwhenradioactiveparticleslodgedintheetchchannel,affectingonlythoseareas.
Toassesstheeffectofaradiationstainonadiamond'sclaritygrade,thegradermustfirstdetermineifthestainisaninclusionorablemish.
Whileallradiationstainspenetrateintothedia-mondtoacertainextent,theyareonlyconsideredinclusionsifthepenetra-tionisvisibleat10*magnification,aswasthecasewiththestainsillustrat-edhere.
Otherwise,thestainingistreatedasablemish,whichhasonlyaminoreffectontheclaritygrade.
VincentCraccoandAlyssaGrodotzkeRareMixedType(Ia/IIb)DiamondwithNitrogenandBoronCentersTypeIIbdiamondsareamongtherarestandmostvaluedofallnaturaldiamonds.
Theircharacteristicbluecolororiginatesfromaverylowcon-centrationofboronimpurities,whichisalsoresponsiblefortheirdistinctiveproperties(see,e.
g.
,J.
M.
Kingetal.
,"Characterizingnatural-colortypeIIbbluediamonds,"Winter1998G&G,pp.
246–268).
Ingeneral,typeIIbdia-mondsdonothavethequantityandvarietyofinclusionsoftenobservedintypeIandsometypeIIadiamonds,whicharedifferentiatedbythepres-ence(typeI)andrelativeabsence(typeIIa)ofnitrogenimpurities.
TheNewYorklaboratoryrecentlyexaminedaveryrarenaturaltypeIIbdiamondwithanoticeabletypeIacomponent.
This0.
17ctroundbril-liantcutwasgradedFancyLightgray-ishblue(figure6,left).
NumerousFigure5.
Thetwobrownpatchesofcolorinthisetchchannel,shownhereat100*magnifica-tion,areradiationstains.
Theetchchannelwasvisibleat10*magnification;asaresult,thesestainswereconsideredinclusionsforthepurposeofclaritygrading.
Figure6.
This0.
17ctFancyLightgrayishbluetypeIIbdiamond(left)con-tainedunusualamountsofnitrogenandhydrogen,characteristicofatypeIadiamond.
TheDiamondViewfluorescenceimage(right)showsthehet-erogeneousdistributionofboron(darkerblueareasrepresentedbyspots1and4)andnitrogen(lighterblueareasrepresentedbyspots2and3).
SP1SP4SP2SP356LABNOTESGEMS&GEMOLOGYSPRING2009graphiteparticlesweretheonlyinclu-sionsobserved.
Electricalconductivity,asmeasuredwithagemologicalcon-ductometer,wasconsistentwiththatofatypicaltypeIIbdiamond.
Thestoneshowedveryweakbluefluores-cencetolong-waveultraviolet(UV)radiationandwasinerttoshort-waveUV.
Itshowedbothblueandredphos-phorescence,asistypicalofnaturalIIbstones.
DiamondViewimagesrevealedzoneswithvarioushuesofbluefluo-rescence(figure6,right),whichsug-gestedaheterogeneousdistributionofdefectsandimpurities.
Themid-infraredspectrum(figure7)hadadominantIIbcharacter,withaboroncomponentindicatedbyabandat~2801cm1.
However,evi-denceofanitrogencomponentwithbothAandBaggregateswasclearlypresentinthe1280–1170cm1region,indicatingatypeIanatureaswell.
Anoticeableamountofhydro-genwasalsoobservedat3107and1405cm1,which—tothebestofthiscontributor'sknowledge—isthefirsttimehydrogenhasbeendirectlyobservedinanaturaltypeIIbdia-mond.
Therelativeintensitiesoftheboron,nitrogen,andhydrogenbandsvariednoticeablyamongtheregionssampled.
Unfortunately,thenatureofourinfraredsystemandtheshapeofthestonedidnotallowustocorre-latethedifferentIRfeaturestospecif-icregionsthatwereindicatedbytheDiamondViewimage.
However,wewereabletocorre-latelow-temperaturePLspectraat325,488,and514nmexcitationstothosespecificregions(figure8).
Thistechniqueallowedustoprobepoint-by-pointforthepresenceorabsenceofnitrogen-relatedfeatures,effectivelymappingthestone'stypeIIbandIaregions.
Specifically,PLspectratakenfromthelighterblueregion(spots2and3infigure6,right)showednitro-genfeaturestypicaloftypeIastones,suchastheN3,H3,H4,andNV0cen-ters;spectrafromthedarkerblueregions(spots1and4)exhibitedvirtu-allynoneofthesefeatures,correlatingtotypeIIb.
ThisPLmappingallowedararedirectobservationoftheN3defectat415nm(alongwithH3,H4,andNV0)inamostlytypeIIbstone,whichisquitenoteworthybecausetheN3defectisconsideredthekeyfeatureinthedistinctionoftypeIfromtypeIIdiamonds.
Figure8.
Takenat325nmUVwavelength,low-temperaturePLspectracol-lectedfromthelighterblueareas(spots2and3)infigure6showedopticalcenters(e.
g.
,N3,H3,H4,andNV0)consistentwithtypeIadiamonds,whereasspectrafromthedarkerblueareas(spots1and4)werefreeofthesenitrogenfeatures,whichisconsistentwithatypeIIbdiamond.
Figure7.
Themid-IRspectrumofthe0.
17ctdiamondshowsadominantlytypeIIbnature,withaboron-relatedbandnear2801cm1,butalso—seeinsets—evidenceofatypeIanature,withnitrogen(e.
g.
,the1173cm1band,correlatingtoB-aggregates)andhydrogen(3107and1405cm1)impurities.
LABNOTESGEMS&GEMOLOGYSPRING200957Mixed-typediamondswithatypeIIbcomponenthavebeenexaminedpreviouslyattheGIALaboratory(e.
g.
,LabNotes:Summer2000,pp.
156–157;Summer2005,pp.
167–168;andWinter2008,pp.
364–365).
However,typeIIbdiamondswithanextensivetypeIacomponenthavebeenobservedonlyrarely.
Themixed-typenatureindicatesasubstantialchangeinthegeochemi-calenvironmentduringthediamond'scrystallization.
Furtheranalysisoftheavailabledatamayshedlightontheinteractionbetweenboron,carbon,nitrogen,andhydrogen,andtheirimpactonthespectralandphysicalproperties.
RenLuPurplishPinkSPINELfromTajikistan—BeforeandAfterCuttingInDecember2007,Pakistan-basedclientSyedIftikharHussainsubmit-tedaparcelofspinelroughreportedlyfromTajikistan(figure9,left).
These84samples,thelargestweighing48.
5g,exhibitedvaryingsaturationsofpur-plishpinkcolor.
Littlehasbeenwrit-tenonthepropertiesofTajikspinel(see,e.
g.
,J.
I.
KoivulaandR.
C.
Kam-merling,"ExamiredTag"style="COLOR:#000000;BACKGROUND-COLOR:#ffff00">nationofagemspinelcrystalfromthePamirMoun-tains,"ZeitschriftderDeutschenGemmologischenGesellschaft,Vol.
38,1989,pp.
85–88),soinNovember2008theBangkoklaboratorywasfor-tunatetohaveanopportunitytobrieflyexaminesevenstonesthattheclienthadfacetedfromthisparcel(fig-ure9,right).
Mostoftheoriginalroughconsist-edofbrokenpieces,andonlyafewshowedtheoctahedralcrystalformstypicalofspinel.
WecouldnotperformaccurateRImeasurementsbecauseofthelackofflatsurfaces,sowehadtorelyonothertests.
ThehydrostaticSGmeasurements,spectraseenwithahandheldspectroscope,polariscopereactions,andUVfluorescencewereconsistentwithspinel.
Theseobserva-tionswerefurthersubstantiatedbyPLspectroscopy(514nmlaserexcitationatroomtemperature)onthelargestpiece,whichproveditwasnaturalspinel.
Themostprominentinclusionsseeninthesampleswereeuhedralcrystals,needles,andcrystalswithwhiteparticulatetrailsforming"comettails"(figure10).
Aftertheroughwascut,weobtainedstandardgemologicalproper-tiesforthesevenfacetedstones.
Theresultswerefairlyconsistent:RI—1.
712–1.
713,SG—3.
59–3.
62,strongredfluorescencetolong-waveUVradiationandweakredtoweak-to-moderateorange(somewithachalkygreenishcast)fluorescencetoshort-waveUV,andacharacteristic"organpipe"spectrum(withsomegeneralabsorptionintheorange/yellowandpartofthegreenregion)seenwiththeFigure10.
Amongtheinclusionsobservedintheroughspinelswereafineeuhedralcrystal(left,magnified75*)andcrystalswithwhiteparticulatetrailsforming"comettails"(right,magnified35*).
Figure9.
Theparcelofroughspinelontheleft,reportedlyfromTajikistan,containspiecesweighingupto48.
5g.
Thesevenfacetedspinelsontheright(9.
04–28.
16ct)werefashionedfromsomeofthisrough.
58LABNOTESGEMS&GEMOLOGYSPRING2009spectroscope.
WhiletherefractiveindiceswerealmostidenticaltothatofthecrystaldetailedbyKoivulaandKammerling(andaTajikspinelreport-edintheSpring1989LabNotes,pp.
39–40),theSGsvariedslightly.
Sincethecleanestpiecesofroughwerelikelyselectedforfaceting,itwasnosurprisethatsixofthecutstonesshowedfewinclusions.
The11.
96ctpearshapehostedthemostinternalfeatures,whichconsistedofaplaneofoctahedralnegativecrystalsandsomeeuhedralcrystals(figure11).
Tinynegativecrystalswereonlyfaintlyvisibleinoneotherstone.
Unfortunately,therewasnotimetoidentifyinclusionsineithertheroughorcutspinelswithRamanspec-troscopy.
ThePLspectrumofthepear-shapedstonecloselymatchedthatoftheroughsample.
NicholasSturmanFigure11.
Oneofthefacetedspinelscontainedaplaneofnegativecrystals(left,magnified50*)andagroupofeuhedralcrystals(right,magnified20*).
PHOTOCREDITSRobisonMcMurtry—1;KarenM.
Chadwick—2;JianXin(Jae)Liao—3,6left;WaiL.
Win—4;JasonDarley—5;RenLu—6right;KenScarratt—9left,10;SuchadaKittayachaiwattana—9right;NicholasSturman—11.