The Journal of Gemmology Volume 26 No. 1 January 1998

The Gemmological Association and Gem Testing Laboratory of Great Britain Gemlnological Association and Gem Testing Laboratory of Great Britain 27 Greville Street, London ECIN 8SU Tel: 0171 404 3334 Fax: 0171 404 8843 e-mail: [email protected] Website: www.gagtl.ac.uk/ gagtl President: Professor RA Howie Vice-Presidents: E.M. Bruton, AE. Farn, D.G. Kent, RK. Mitchell Honorary Fellows: RA Howie, RT. Liddicoat Jnr, K. Nassau Honorary Life Members: D.J. Callaghan, E.A Jobbins, H. Tillander Council of Management: CR Cavey, T.J. Davidson, N.W. Deeks, RR Harding, I. Thomson, V.P. Watson Members' Council: AJ. Allnutt, P. Dwyer-Hickey, R Fuller, J. Greatwood, B. Jackson, J. Kessler, J. Monnickendam, L. Music, J.B. Nelson, P.G. Read, R Shepherd, CH. Winter Branch Chairmen: Midlands - G.M. Green, North West - I. Knight, Scottish - B. Jackson Examiners: AJ. Allnutt, M.5c., Ph.D., FGA, S.M. Anderson, B.Sc. (Hons), FGA, L. Bartlett, B.Sc., M.Phil., FGA, DGA, E.M. Bruton, FGA, DGA, CR Cavey, FGA, S. Coelho, B.Sc., FGA, DGA, Prof. AT. Collins, 8.Sc., PhD, AG. Good, FGA, DGA, CJ.E. Hall, 8.Sc. (Hons), FGA, G.M. Howe, FGA, DGA, G.H. Jones, B.Sc., Ph.D., FGA, M. Newton, B.Sc., D.Phil., H.L. Plumb, B.Sc., FGA, DGA, RD. Ross, B.Sc., FGA, DGA, P.A Sadler, B.Sc., FGA, DGA, E. Stern, FGA, DGA, Prof. I. Sunagawa, D.Sc., M. Tilley, GG, FGA, CM. Woodward, 8.Sc., FGA, DGA

Tb.e JotJnra1o.£G~nunology Editor: Dr R.J~. Harding A$st'stant Ed1.tor$:M~J. a'Donoghue, P:G .. Read AssQeiat~ E,d.,#Pf'5: S~M. M!lietson (LOi1dott), Dr C.E.S. Alps (Leid~n), G~B9Sshart (ll.,'tt~~)j' Ptof.A.'t C~i (Lond.ll>:tll. Dr J.W. HlUTis (Gla$gow), Prof. RA. Howie (Derbyshire), Dr J.M.. Ogden. (Cambridge). .. Or J.E. Shigl~(Carlsbad;)~ &0,£. DoC. Smith (Paris), E. stem (London), Prof-I. Sunagawa Cf~kYo), Dr M. Superchi (Mil~lil),C.M.Woodward (London) Production Editor:M.A. Burland

Vol 26, No.1, January 1998 ISSN: 1355-4565 Turquoise from Hubei Province, China Qi Lijian, FGA, DGA, Yan Weixuan, FGA, DGA, and Yang Mingxin, FGA China University of Geosciences, Wuhan, 430074, P.R. China

ABSTRACT: The turquoise deposit in Yunyang district, Hubei Province, China, is characterized by its large scale, complex and variable ore-body types and colour varieties, compared with similar bodies outside China. The copper and phosphorus in the deposit originate mainly from finely dispersed sulphides in layered carbonaceous-siliceous slates, and from colloidal apatites (collophane) that occur in an irregular and patchy distribution pattern. The host rocks favourable for the formation of the turquoise are relatively rich in silica, copper and phosphorus and relatively poor in potassium, calcium and magnesium. The ore occurs mainly in lenticular bodies compressed between the layers. The distinctive mineralization is controlled by lithology, structure and the effects of ground water movement. The colouring mechanism of the turquoise results from a combination of [Cu (H20)4]2+, Fe3+ and Fe2+ ions. The colouring ions and the existing form and content of H20 limit directly the colour of the turquoise. The turquoise deposit can be considered as having been formed by a process of secondary leaching.

Keywords: turquoise, mineral deposit, secondary leaching 1

Introduction unyang in Hubei Province, located in the eastern section of the Qinling fold Yzone at the intersection of Hubei, Henan and Shanxi provinces (Figure 1), is well known not only for its high-quality turquoise but also for its excellent carving techniques and life-like handicrafts (Figure 2). The exceptionally long mining history of turquoise can be deduced from the 20 turquoise beads unearthed with Qijia cultural relics of late Neolithic Age, located in Yongjing County, Gansu Province, China. This indicates a mining history of about 3200-3800 years (Hao Yongwei et al, 1982). Figure 1: Location map of the turquoise deposits At present, the holes for extraction of the in Hubei. Bai He is approximately 500 km NWof turquoise ore are readily apparent (Figure 3). Wuhan.

© Gemmological Association and Gem Testing Laboratory of Great Britain ISSN: 1355-4565 Figure 3: AncientAncient cavescaves where turquoise waswas mined.mined. 2 Figure 4: Turquoise deposits at Yungaisi,Yungaisi, Yunxian County,County, Hubei. Hubei. Figure 2: Turquoise carving 'A picture ofof Paradise' (32x48x27 (32x48x27 cm). cm). Photo: Photo: Yuan Yuan Jiaqi. Jiaqi.

ThThee complecomplexx metallogenimetallogenicc anandd geologicalgeological conditionconditionss ooff ththee turquoiseturquoise,, ththee variousvarious morphologiemorphologiess ooff ththee ororee bodybody,, ththee widwidee spatialspatial distributiodistributionn ooff ththee turquoisturquoisee anandd ititss irregularirregular occurrencoccurrencee iinn thithiss districdistrictt havhavee attracteattractedd littllittlee attentioattentionn frofromm ththee GovernmenGovernmentt foforr a lonlongg timetime.. IInn 19801980,, a teamteam fromfrom thethe HubeiHubei BureauBureau ofof GeologGeologyy anandd MineraMinerall ResourceResourcess carriecarriedd ououtt a reconnaissance geologicageologicall survesurveyy ooff ththee turquoisturquoisee deposidepositt aatt 1:200,001:200,0000 scalescale.. IInn 19821982,, ZhanZhangg HuifenHuifen,, JianJiangg ZechunZechun,, et ah,al., frofromm ththee GuiyanGuiyangg GeochemistrGeochemistryy InstitutInstitutee undeunderr ththee AcademAcademyy SinicSinicaa madmadee a detailedetailedd investigatioinvestigationn intintoo ththee turquoisturquoisee mineralogmineralogyy iinn thithiss districdistrictt anandd oonn ththee basibasiss ooff thithiss iitt wawass evidenevidentt thathatt mormoree needeneededd ttoo bbee donedone.. FoForr ththee paspastt severaseverall yearsyears,, ththee first-namedfirst-named authoauthorr anandd hihiss colleaguecolleaguess iinn ththee GemmologicaGemmologicall InstitutInstitutee ooff ththee UniversitUniversityy ooff ChinChinaa (Wuhan(Wuhan)) havhavee climbeclimbedd ththee QinlinQinlingg

J.J. Gemm., 19981998,26,1,1-12, 26, 1, 1- 12 mountains,mountains, havehave investigatedinvestigated severalseveral tunnelstunnels whichwhich werewere stillstill beingbeing activelyactively minedmined andand havehave exploredexplored severalseveral abandonedabandoned cavescaves inin orderorder toto tracetrace thethe originorigin ofof thethe turquoiseturquoise andand toto prospectprospect forfor newnew occurrencesoccurrences (Figure 4) 4)..

StratigraphicalStratigraphical andand lithologicallithological featuresfeatures TheThe ore-bearingore-bearing bedbed hashas beenbeen identifiedidentified asas thethe LowerLower CambrianCambrian ShuigoukouShuigoukou FormationFormation (E(e^g) jsg),, partpart ofof a regionallregionallyy metamorphosedmetamorphosed rockrock successionsuccession (Bao(Hao YongweYongweii et aI.ah,, 1982)1982).. ItsIts lithology isis composedcomposed mainly mainly of ofcarbonaceous-siliceous carbona­ ceous-siliceous slates,slates, carbonaceouscarbonaceous claclayy andand siliceoussiliceous slates,slates, bandebandedd thin-layethin-layerr siliceoussiliceous slates,slates, carbonaceoucarbonaceouss micmicaa quartzquartz rocks, calcareoucalcareouss micamica quartz-schistsquartz-schists andand carbonaceouscarbonaceous claclayy marbles.marbles. ThThee turquoiseturquoise Figure 6: Collophane (Apa)(Apa) and and quartz quartz (Si) (Si) occuroccurss mainlmainlyy inin ththee firstfirst threethree typetypess ofof rocksrocks.. along aa bedding bedding plane plane in incarbonaceous-siliceous carbonaceous-siliceous ThThee carbonaceous-siliceouscarbonaceous-siliceous slateslatess (th(thee hosthostss ooff slate, x60. x60. the turquoiseturquoise oreore bodies)bodies) havehave been been universally univer­ sally silicifiesilicifiedd anandd recrystallizerecrystallizedd intointo massivmassivee typicatypicall ofof quartz,quartz, carbonaceouscarbonaceous materialmaterialss andand slatslatyy quartzitquartzitee (Figure 5) 5).. This Thi srock roc kis i sgrey gre yto t o sericite,sericite, cacann bbee observeobservedd (Figure 6), 6), together togethe r blacblackk anandd characterizecharacterizedd mainlmainlyy bbyy aann witwithh colloidacolloidall structurestructuress anandd isotropiisotropicc areas.. intermediate-to-finintermediate-to-finee granulagranularr structurestructure,, anandd a 3 3 FielFieldd observationobservationss shoshoww thathatt ththee intensitintensityy ooff densdensee anandd harhardd texturetexture.. ThThee rocrockk iiss composedcomposed mineralizationmineralization,, ororee bodbodyy morphologmorphologyy anandd ororee ooff quartquartzz (80-85%)(80-85%),, carbonaceoucarbonaceouss materiamateriall qualitqualityy ooff thithiss districdistrictt araree alalll controllecontrolledd bbyy ththee (10-15%)(10-15%),, sericitsericitee (3-5%)(3-5%),, anandd albitalbitee (<1%)«1%).. lithologlithologyy (Figure 7). 7). ThThee carbonaceoucarbonaceouss siliceousiliceouss slateslatess frofromm ththee stronglstronglyy mineralizemineralizedd segmensegmentt ooff thithiss districdistrictt contaicontainn mormoree ooff ththee patchpatchyy colloidacolloidall apatitesapatites Figure 7: Mineralized intermediate toto thickly thickly (collophane)(collophane).. IIff thithiss rocrockk iiss sectionesectionedd anandd bedded carbonaceous-siliceous carbonaceous-siliceous slates slates.. The marker The marker observed through thethe microscope,microscope, the the features, features, indicates the the mineralization. mineralization.

Figure 5:5: Thin Thin section section of ofcarbonaceous-siliceous carbonaceous-siliceous slate,slate, finefine toto medium medium grained grained,, in incrossed crossed polars, polars, x60.

TurquoiseTurquoise from HubHubeiei Province, China Table I:I: Chemical compositions of rocks associated withwith turquoiseturquoise

LithologyLithology NumberNumber of of WeightWeight per per cent cent oxide oxide PartsParts perper miliummillion (ppm)(ppm) analysesanalyses SiO SiO,z A1A2lP03 , CaOCaO MgOMgO KK,O20 Ppp2O5 , CuCu PbPb ZnZn MoMo VV Ag NiNi Mn

CarbonaceousCarbonaceou-s- 3322 90.990.922 2.22.266 0.20.211 0.30.388 0.50.511 0.40.433 747.2747.233 25.425.411 177.4177.455 19625 196.25 1962.1962.55 4.94.955 158.7158.755 929255 siliceousiliceous sslat slaete

CarbonaceouCa rbonaceous s 7 7 84.684,633 5.25.288 0.30.344 0.5 0.566 3.43.444 0.070.0755 28.728.788 31.131.144 79.679.688 176.1176.177 1420. 1420.66 7.27.266 47.447.411 866.6866.677 muddmuddy yan andd siliceousiliceous sslat slaete

MicMiaca quart quarztz 1122 64.364.388 13.713.766 1.91.955 1.31.399 4.34.388 0.190.1944 21.121.199 27.627.655 52.052.066 41.341.333 125.0125.044 1.01.099 14.514.533 815.7815.744 schisschitst

CalcareouCalcareouss mic miaca 44 33.233.233 4.34.377 43.343.311 3.63.688 2.32.355 0.020.0266 43.343.399 13.713.733 24.524.544 64.864.811 92.292.266 <0.<0.33 13.613.655 540.1540.16 quartz-schisquartz-schitst

MuddM uddy ymarbl marble e 5 5 14.614.622 2.02.055 53.853.877 16.516.522 0.70.722 0.120.1288 5.45.422 11.311.377 18,918.922 32.332.366 85.285.299 <0.<0.33 9.49.444 672.0672.011

NoteNote:: contencontentt ooff carbocarbonn nonott determined.determined.

GeochemicalGeochemical featurefeaturess ooff ththee rockrockss silica,silica, coppecopperr anandd phosphoruphosphoruss iinn ththee oreore­- containingcontaining ththee turquoisturquoisee ororee bearinbearingg carbonaceous-siliceoucarbonaceous-siliceouss slatesslates areare mucmuchh highehigherr thathann thosthosee iInn ththee ore-freeore-free ThThee chemicachemicall compositioncompositionss ooff 6600 freshfresh carbonaceoucarbonaceouss anandd siliceousiliceouss slatesslates anandd otherother unmineralizeunmineralizedd rocrockk samplesampless collectecollectedd fromfrom differendifferentt sectionssections closclosee ttoo ththee turquoiseturquoise rocksrocks.. FurthermoreFurthermore,, ththee contentcontentss ooff coppercopper depositdeposit revealreveal thathatt theitheirr petrochemicalpetrochemical andand phosphoruphosphoruss areare fafarr higherhigher thathann thethe compositionscompositions differdiffer greatlygreatly frofromm thosethose ooff thethe regionalregional geochemicageochemicall backgrounbackgroundd valuesvalues 4 4 ore-bearingore-bearing segmentsegment (Table D. I). The Th econtents content sof o f (eu:(Cu: 8080 ppmppm,, P:P: 0.05%)0.05%)..

Figure 8: The relationship between the ratio of Al22003 3 to SiOzSi02 in different rock types in the metamorphic rock system and its correlation with zones in the areore deposit (based on the chemicalchemical analysis of 60 rock samples).

SiQ % * Al2O3/SiO2=0.01 Si022 % •• CaCarbonaceous-siliceourbonaceous-siliceouss sslatlatee

x x CCarbonaceous-siliceouarbonaceous-siliceouss sslatlatee

...A MMicicaa ququartz-schisartz-schistt

80 o• CalcCalcareouareouss micmicaa ququartz-schisartz-schist t •• MMudduddy mamarblrblee ...... (I)(I) Richh oreore zzononee 60 ...... -- -- Y ___ _ ' ______~::::— .::.— (II) (II )Mi Mineralizeneralized dz onzone e p (III) Zone without ore 40- / (III) Zone without ore (III(Ill)) / (III) .• A10 I. 20 20- P/ . j ·1 A120 3% A1203% ~l2 1 61 1 101 1 141 1 118 1 22T " 2 6 10 14 18 22

J./. Gemm., 1998 1998,26,1,1-12, 26, 1, 1-12 InIn orderorder toto furtherfurther understandunderstand thethe statestate ooff occurrenceoccurrence ofof ththee coppercopper andand phosphorusphosphorus inin thethe ore-bearingore-bearing rocks,rocks, eighteight samplessamples werewere chosenchosen fromfrom thethe varietiesvarieties ofof rocksrocks inin thethe ShuigoukoyShuigoukoy FormationFormation inin ththee YungaisiYungaisi profileprofile (E(e ajsg)sg) anandd theitheirr constituentconstituentss analyzeanalyzedd inin detail.detail. ResultsResults showshow thatthat thethe coppercopper occursoccurs mainlymainly inin sulphidessulphides finelyfinely disperseddispersed throughoutthroughout thethe rockrock andand thatthat itit constitutesconstitutes onlyonly a veryvery smallsmall percentagepercentage ofof thethe silicates.silicates. PhosphoruPhosphoruss occursoccurs mainlymainly inin thethe irregularirregular patchypatchy colloidalcolloidal apatitesapatites (collophane).(collophane).

CalculationsCalculations ofof thethe ratioratio AlP/Si0Al203/Si02 indicateindicate thatthat silicificationsilicification isis closelyclosely associatedassociated witwithh thethe mineralizationmineralization inin thisthis districtdistrict (Figure 8). 8). That Tha tis, is with, with the the increase increase in in mineralization,mineralization, thethe A1Al220/Si003/Si02 ratioratio decreases;decreases; whenwhen thethe ratioratio ofof AlP/Si0Al203/Si02 isis Figure 9: Turquoise in in a acompressed compressed fractured fractured <0.05%,<0.05%, itit isis favourablefavourable forfor metallogenesis.metallogenesis. zone betweenbetween beds beds of slate.of slate. AnotherAnother markermarker inin termsterms ofof thethe petrochemistrypetrochemistry favourablefavourable forfor thethe formationformation ooff nodulesnodules inin ththee compressecompressedd andand fracturedfractured turquoiseturquoise inin thisthis districtdistrict isis thethe relativelyrelatively highhigh zoneszones betweebetweenn ththee layerslayers ofof complexcomplex foldfold concentrationconcentration ofof Si02 comparedcompared withwith ~O,I^O, structuresstructures andand iinn tensiotensionn jointsjoints.. IInn thithiss sensesense,, CaOCaO andand MgOMgO inin thethe carbonaceous-siliceouscarbonaceous-siliceous thethe YunyanYunyangg regioregionn iiss distinctivelydistinctively slate,slate, thathatt isis (CaO+~O+MgO)/Si02<0.02%.(Ca<>Kp4MgO)/SiO2<0.02%. characterizedcharacterized bbyy tectonitectonicc controcontroll ooff ththee ororee 5 5 ItIt isis importantimportant toto notenote thatthat thisthis districtdistrict waswas (Figures 9 9and and 10). 10). subjectsubject toto a seriesseries ofof geologicalgeological processesprocesses MostMost ooff ththee fracturfracturee zonezoness iinn thethe includingincluding weathering,weathering, leachingleaching andand migrationmigration YunyangYunyang DistricDistrictt araree compressecompressedd betweebetweenn thethe ofof metallogenicmetallogenic elements,elements, whichwhich resultedresulted inin stratastrata ofof ththee intermediate-intermediate- ttoo thick-beddedthick-bedded thethe formationformation ofof thethe turquoiseturquoise depositdeposit throughthrough locallocal concentrationconcentration andand precipitation.precipitation. Figure 10: Turquoise filling filling tension tension joints joints in in slate. GeologicalGeological featuresfeatures ofof thethe slate. turquoiseturquoise depositdeposit TheThe turquoiseturquoise depositsdeposits inin YunyangYunyang DistrictDistrict occuroccur atat thethe southernsouthern edgeedge ofof thethe easterneastern sectionsection ofof thethe QinlingQinling foldfold zonezone andand atat thethe westernwestern edgeedge ofof thethe WudangshanWudangshan terrainterrain (Y(Yuu GaiGai SiSi MineMine andand LaLa BaBa ShanShan Mine).Mine). OnOn thethe whole,whole, thethe turquoiseturquoise depositsdeposits followfollow thethe samesame directiondirection asas thethe majormajor regionalregional strikesstrikes andand tectonictectonic lineslines (Hao(Hao YongweiYongwei et al.,ah, 1982;1982; PengPeng Yuanguo,Yuanguo, 1989).1989). InIn thisthis region,region, secondarysecondary foldsfolds andand fracturefracture tectonicstectonics areare wellwell developed,developed, butbut thethe tectonictectonic patternspatterns cancan bebe veryvery complex.complex. TheyThey have,have, however,however, createdcreated veryvery favourablefavourable spacespace conditionsconditions forfor thethe formationformation ofof thethe turquoise.turquoise. GemGem qualityquality turquoisturquoisee suitablesuitable forfor useuse inin jewellerjewelleryy oftenoften occursoccurs asas lenticleslenticles andand

Turquoise fromfrom HubeiHubei Province,Province, ChinaChina Figure 13: Detail of typical nodular turquoise.turquoise.

Figure 11: Nodular turquoise in the lenticles compressed between slate beds.

carbonaceous-siliceouscarbonaceous-siliceous slates.slates. GenerallyGenerally speaking,speaking, thethe moremore thethe lenticleslenticles havhavee beenbeen compressecompressedd betweebetweenn ththee stratastrata,, ththee moremore nodulanodularr ththee turquoiseturquoise andand thethe bettebetterr itsits gemgem 1746 6 quality.quality. InIn additionaddition toto turquoise,turquoise, thethe lenticleslenticles 14: are composedcomposed largely largely of looseof loose clay, clay, carbonaceous carbona­ Figure 14: Turquoise fromfrom aa quartzquartz vein.vein. ceous materialsmaterials,, limonitelimonite,, siltsilt,, sandsand andand protolithic breccia breccia (Figure (Figure 11). 11). shapeshape anandd typetype.. ThThee coloucolourr varietievarietiess andand ComparedCompared witwithh turquoisturquoisee depositsdeposits excellenexcellentt qualityquality areare amonamongg ththee besbestt inin thethe outsideoutside ChinaChina (Faya(Fayazz anandd Forghani,Forghani, 19751975;; worldworld.. InIn Yunyang,Yunyang, alsoalso,, therethere areare moremore IvanovaIvanova,, v.P.,V.P., 1974),1974), thethe YunyangYunyang turquoiseturquoise complexcomplex parageneseparagenesess anandd a greatergreater varietvarietyy ooff depositsdeposits araree largelargerr anandd mormoree complexcomplex inin bothboth associatedassociated mineralsminerals iinn thethe region.region. ThThee turquoiseturquoise oreore bodbodyy iiss lenticularlenticular Figure 12: Nodular turquoise mined from a overalloverall,, bubutt therethere araree somsomee secondarsecondaryy veins.veins. tunnel. LocallLocallyy ththee accumulationaccumulation ofof turquoiseturquoise isis nodularnodular,, massivmassivee oror botryoidabotryoidall (Figures 12,12,13 13 and 14). ThThee turquoiseturquoise depositdeposit isis verticallverticallyy zonedzoned anandd atat YungaisiYungaisi,, forfor exampleexample (Figure 15), aatt oror neanearr ththee groundground surfacesurface 820-840820-840 m abovabovee seasea levelevell ththee turquoisturquoisee depositdepositss araree palpalee inin colour,colour, poopoorr iilln quality,quality, andand ofof smalsmalll volumevolume andand lowlow hardnesshardness.. BuButt aatt ththee approximateapproximate groundground watewaterr surfacsurfacee 720-800720-800 m aboveabove seasea levellevel thertheree areare prolifiprolificc oreore zoneszones withwith turquoisturquoisee ooff ththee besbestt qualityquality andand excellentexcellent colours.colours. ForFor instanceinstance,, aboutabout 60060000 kkgg hahass beenbeen mineminedd frofromm jusjustt ononee lenticulalenticularr ororee bodybody,, withwith somesome individualindividual massemassess ooff turquoisturquoisee asas heavheavyy aass 100100 kgkg.. AAtt depthdepthss lowerlower thathann 707000 m

/J.. Gemm., 1998,1998,26,1,1-12 26, 1, 1-12 C> 1000O m YUYU qAISICfAI SI ) ^ SW21SW215 ^ I1 1 1

800800 Ik^^lm^ AA B 600600 ^$H 6 ^y i^_ x x x x — XY^»^—x —- X ^ VTTvX C x \\\ E1sg Z2d 1 e 400 lSg Z2d 400 c. c. - _ _ 1 -1 -—. ->_ —»_ Ca—Ca-c. — -- - l-l 1 --->_ -«_ c.—Ca- c.— ~ ~ ~ ~^-— --*_ -N_ 200 vm///turquoise sil iceous sla te mudd1- 1y mi ca quartz calcCa ic Ca->mica- 700 siliturquoisceous slea te si liceous slat e limmuddestonye micsca hiquarst t z qucalciartzc- scmichisat s liceous sla e limestone schist <3uartz-schis t II II 200m Fx~xj-x—x- ) ~1 « -II D G 0 200 m A B - muddIIy -Im ~I rbl e oxidized ore shoot mineralicza tion i_ 1 1 m uddy marb le oxidizezod ne orzoe shoone t lowem ineralizatir limit zocn ne leaching zone zone lower limit zone

Figure 15: Schematic diagram of the turquoise range of occurrence.occurrence. abovabovee seasea levellevel,, turquoisturquoisee rarelrarelyy occursoccurs.. ButBut chemicachemicall constituentconstituentss A1~0203,' P20O5s anandd ~O,H20 , 7 7 ththee quantitquantityy ooff massivmassivee allophaniteallophanite araree relativelrelativelyy stablstablee (Table II) II).. markedlmarkedlyy increasesincreases.. BeneatBeneathh 686800 m abovabovee seseaa FresFreshh turquoiseturquoise,, massivmassivee anandd opaque, levellevel,, turquoisturquoisee iiss virtuallvirtuallyy absenabsentt (thes(thesee displaydisplayss a weaweakk lustrlustree describedescribedd aass waxwaxyy figurefiguress applapplyy ttoo ththee regioregionn whoswhosee watewaterr tabltablee anandd a conchoidaconchoidall fracturefracture.. ThrougThroughh ththee elevatioelevationn iiss abouaboutt 808000 m abovabovee seseaa level)level).. microscopmicroscopee ththee structurstructuree ooff turquoisturquoisee cacann bbee seeseenn ttoo bbee cryptocrystallincryptocrystallinee ttoo GemstonGemstonee anandd mineraminerall microcrystallinemicrocrystalline,, anandd localllocallyy spheruliticspherulitic featurefeaturess ooff ththee turquoisturquoisee (Figures 1616 and and 17) 17).. In In places, places ,pisolitic pisoliti cand and oolitiooliticc structurestructuress cacann bbee observeobservedd (Figure 18). 18). TurquoisTurquoisee iiss a hydrouhydrouss coppecopperr aluminiumaluminium ThThee refractivrefractivee indeindexx ooff ththee turquoisturquoisee rangerangess phosphatphosphatee witwithh a chemicachemicall compositiocompositionn ooff frofromm 1.611.6144 ttoo 1.652,1.652, itsits hardnesshardness isis betweenbetween 55

CuAlCuAI6(P044))4,(OH)s,5Hp.4.(OH)8.5H20. AlthougAlthoughh ththee anandd 5.5.44 anandd specifispecificc gravitgravityy lieliess betweebetweenn 2.52.566 coloucolourr ooff turquoisturquoisee iiss variablevariable,, ititss maimainn anandd 2.782.78.. BrownBrown andand blackblack lineslines andand irregularirregular

Table II. ChemicalChemical composition of turquoiturquoisese fromfrom Yunyang, 1Hubei, China (in weight perper centcent oxides) Sample Colour Al 0 Fe 0 FeO CuO CaO H 0 Total Sample Colour AlP2 3 3 PP2O250 5 Fe2203 3 FeO Cuo CaO Hp2 Total numbernumber T-00T-0011 BluBluee 35.935.922 34.634.644 1.21.211 - 8.38.344 0.00.044 19.719.755 99.999.900 T-00T-0066 Pale-bluPale-bluee 36.136.122 33.433.400 1.11.144 - 7.57.522 0.00.022 20.620.644 98.898.844 T-01T-0199 Blue-greeBlue-greenn 35.535.577 34.1 34.155 2.72.700 0.00.033 7.17.177 - 20.320.322 99.999.944 T-02T-0222 GreeGreenn 34.734.799 35.135.111 3.03.077 0.00.044 6.36.388 0.00.Q22 18.718.711 98.198.122 T-02T-0255 Yellow-greeYellow-greenn 34.034.066 34.8 34.899 6.56.588 0.00.088 6.26.233 - 18.718.733 100.5100.577

TurquoiseTurquoise fromfrom HubHubeiei Province, China Figure 18: Turquoise displaying oolitic shapes, x20.

Figure 16: Spherulitic structure in turquoise,turquoise, crossed polars,polars, x100.xlOO.

whitewhite veinsveins iinn thethe turquoiseturquoise areare commoncommon featuresfeatures (Figure 19); thethe blacblackk lineslines areare attributedattributed toto carbonaceouscarbonaceous material,material, andand thethe brownbrown toto ironiron oxidesoxides oror hydroxides.hydroxides. 8 8 FourierFourier transformtransform infraredinfrared spectroscopyspectroscopy (using(using a NicoleNicolett - 550)550) cancan bbee performeperformedd onon Figure 19: Irregular brown (iron) and black KBrKBr pressedpressed discsdiscs containingcontaining thethe turquoiseturquoise toto (carbon) lines with white vein striation crossing determinedetermine itsits infraredinfrared absorptionabsorption spectrum.spectrum. turquoise, xl0.xlO. OneOne spectrumspectrum isis shownshown inin Figure 20 wherewhere thethe peakpeakss areare interpretedinterpreted asas resultingresulting fromfrom Figure 17: Spherulitic structure of turquoise,turquoise, ththee stretchingstretching andand curvingcurving vibrationsvibrations mainlymainly crossed polars,polars, x100.xlOO. fromfrom OH,OH, H 200 andand alsoalso fromfrom thethe [P0[P041] tetrahedrontetrahedron (Table III).III). InIn thethe presenpresentt paperpaper,, thethe differentialdifferential scanningscanning calorimetrycalorimetry (DTA(DTA iinn DSCDSC mode)mode) techniquetechnique isis employedemployed toto determindeterminee thethe behavioubehaviourr ofof turquoiseturquoise powdepowderr withwith increaseincrease inin temperature,temperature, withwith thethe turquoiseturquoise samplessamples andand referencereference samplessamples beinbeingg subjectsubject toto thethe samesame adjustableadjustable temperaturetemperature conditions.conditions. TheThe resultresultss areare shownshown inin Figure 21, inin whichwhich thethe valuesvalues onon thethe ordinateordinate representrepresent HeatHeat FlowFlow (mW).(mW). TheThe resultsresults showshow thatthat thethe waterwater (HP)(H20) inin turquoisturquoisee isis drivendriven offoff whenwhen heatingheating throughthrough thethe temperaturetemperature rangerange fromfrom 350°C350°C toto 380°C,380°C, andand thethe resultinresultingg endothermicendothermic effecteffect isis causedcaused byby thethe completecomplete breakdowbreakdownn ofof thethe crystalcrystal latticelattice ofof thethe turquoise.turquoise. Therefore,Therefore, itit isis concludedconcluded thatthat thethe waterwater inin turquoiseturquoise occursoccurs nonott onlyonly asas crystallinecrystalline waterwater bubutt alsoalso asas

J. Gemm., 1998,1998,26,1,1-12 26, 1, 1-12 Table III. Infrared absorption spectra of turquoise (peak positions in em:")

Source Present paper Zhang Huifen H. Moenke (blue, 1996) (blue, 1982) (1962) Vibration type Stretch ing vib rat ion of OH and H2O 3508.70 3511 3508 3465.97 3465 3463 3448.20 3440 3446 3289.15 3320 3295 3088.23 3090 3090

Curving vibration of H2O 1633.47 1625 1650 Stre tching vibratio n of P-o(13) 11 82.40 1184 1195 1157.52 1160 11 75 11 09.70 1105 1115 1060.40 1050 1063 1011 .53 1010 1016 Stretchi ng vibration of P-o(l l) 902 890 905

Curving vibra tion of OH 835 837 838 778 777 790 723 717 698 Curving of vibra tion of P-o(14) 648 645 615 615 600 615 588 585 596 567 540 580 502 475 480 478 450 460 I 9 Curving vibra tion of P-O(12) 446 422 425 432 410 405 411

Figure 20: Infrared absorption spectrum of turquoise.

7. 71 6 6 1633.47 5 5

~ 4 7. ~ 4 . ~ 3571 ~ 6 ~ 31 6 Ii' 25 1011.53 5 5 1157.52 IN 587.93 3508.70 4 1060.40 3465.97 4 35 1109.70 31 25 4000 3500 3000 2500 2000 1500 1000 500 Wave numbers (cm')

Turquoise from HubeiProvince, China Tu012Tu012 ^ 350.0 777.46777.46°°C C 300.0 245.647245.64 mW7 mW > Tu015Tu01 5 ~ E 250.0 i=: 764.52°C ~ 198.645j 0 200.0 P a 0 Tu029 "d o 150.0 i=: ~ ~ 1 350.25°C 0 100.0 2.040mW ~ o Tu002 ~ Tu002 ::r:QJ 50.0 S 0.0

-50.0 250.0 500.0—I 750.01 1000.0I 250.0 500.0 750.0 1000.0 Temperature (0C) Temperature (°C)

Figure 21: Differential thermal analysis (DTA) in Differential Scanning Calorimetry (DSC)(DSC) mode:spectra ofof turquoisesturquoises ofof differentdifferent colours.colours. (Tu012(Tu012 grey-yellow;grey-yellow; Tu015Tu015 yellow-green;yellow-green; Tu029Tu029 blue­blue- green; Tu002 blue). 1010 constitutionaconstitutionall waterwater,, andand ththee exothermicexothermic effecteffect BecausBecausee ththee heaheatt stabilitstabilityy ooff ththee turquoiseturquoise showshownn iinn ththee temperaturtemperaturee rangrangee fromfrom 760°760°CC toto frofromm thithiss districtdistrict isis relativelrelativelyy poorpoor,, ththee gemgem 800°800°CC hahass resulteresultedd fromfrom recrystallizatiorecrystallizationn afterafter shouldshould bbee welwelll lookelookedd afteafterr andand shouldshould bebe expellinexpellingg ththee constitutionalconstitutional watewaterr fromfrom thethe protecteprotectedd frofromm totooo mucmuchh exposureexposure ttoo ththee sunsun turquoise, resulting resulting in ina newa new heatphase heatphase transformation trans­ oor r ttoo highighh temperaturestemperatures.. IInn thithiss wawayy thethe formation productproduct.. ThisThis phasphasee isis anan coloucolourr ofof ththee stonestone cancan bbee maintained.maintained. aluminiualuminiumm phosphatphosphatee whoswhosee structurstructuree isis TheThe paragenetiparageneticc anandd otherother mineralsminerals similarsimilar ttoo thosthosee ofof cristobalitcristobalitee andand tridymitetridymite accompanyingaccompanying ththee turquoisturquoisee cancan bbee divideddivided (Khorassan(Khorassanii andand AbediniAbedini,, 1976;1976; ZhanZhangg HuifenHuifen intointo twtwoo majomajorr groupsgroups accordingaccording ttoo theirtheir et ah,al., 1982;1982; AndersonAnderson,, 1962)1962) andand whoswhosee colourcolour origin:origin: isis brownbrown.. IInn additionaddition,, iitt shoulshouldd bbee notenotedd thatthat turquoisturquoisee samplessamples differindifferingg inin colour,colour, 1.1. quartzquartz,, sericitesericite,, colloidacolloidall apatitesapatites hardneshardnesss andand degredegreee ofof weatherinweatheringg displaydisplay (collophane)(collophane) anandd sulphides;sulphides; endothermicendothermic anandd exothermicexothermic effecteffectss atat slightlyslightly different temperatures. temperatures. 22.. halloysitehalloysite,, allophaneallophane,, variscitevariscite,, evansite,evansite, woodhouseitewoodhouseite,, goethite,goethite, limonite,limonite, jarositejarosite,, IInn summarysummary,, ththee colouringcolouring mechanismechanismm ooff chalcanthite,chalcanthite, barytebaryte,, cuprocalcite,cuprocalcite, ththee blubluee turquoisturquoisee resultresultss mainlmainlyy fromfrom thethe 2+ brochantitbrochantitee anandd azuritazuritee (Figures 22, 23 hydratehydratedd ionionss ofof coppecopperr [CU(HP)4[Cu(H 0) ] +.. TheThe 2 4 F and 24). existinexistingg forformm andand contencontentt ooff H200 inin thethe turquoisturquoisee structurestructure playplayss aann extremelyextremely ThThee mineralmineralss inin ththee firstfirst grougroupp werewere importanimportantt rolrolee iinn ththee qualitqualityy ofof itsits brilliantbrilliant formeformedd durinduringg diagenesidiagenesiss anandd ththee secondsecond colourcolour anandd alsalsoo isis oneone ofof ththee majomajorr causescauses forfor grougroupp consistsconsists ooff mineralmineralss formedformed duringduring ththee fadinfadingg ooff turquoiseturquoise.. WitWithh anan increasincreasee ooff weatherinweatheringg processesprocesses.. BotBothh groupsgroups ooff 2+ 3+ Fe2+ oorr Fe3+ content,content, ththee colourcolour ofof turquoiseturquoise mineralmineralss areare closelcloselyy connecteconnectedd witwithh thethe mamayy varvaryy fromfrom blubluee ttoo blue-greeblue-greenn ttoo green.green. origioriginn ofof ththee turquoise.turquoise.

/J.. Gemm., 1998, 26,26,126,1,1-12 1, 1-12 Figure 22: Evansite, an accompanying mineral of the turquoise.

Figure 24: Brochantite, associated with the turquoise deposit.

waterwater level.level. ThThee petrochemicapetrochemicall indicatorsindicators favourablefavourable forfor mineralizatiomineralizationn araree highighh silica,silica,

coppercopper andand phosphoruphosphoruss anandd loloww CaO,CaO, KK2200 andand MgO;MgO; additionally,additionally, ththee ratiratioo AIP/Si0Al203/Si02 shouldshould bbee <0.05%<0.05%,, andand (CaO+Kp+MgO)j(CaO+K20+MgO)/ Si0SiO <0.02%<0.02%.. 2 11 11 Figure 23: Variscite, associated with the TheThe majomajorr oreore shooshoott occursoccurs inin lenticularlenticular turquoise deposit. bodiesbodies compressecompressedd betweebetweenn ththee maimainn rockrock strata.strata. ThisThis ore-bodyore-body morphologmorphologyy andand thethe SummarySummary gemgem qualityquality areare botbothh controlledcontrolled bbyy ththee scalescale ofof thethe fracturefracture zonezone compressecompressedd betweebetweenn thethe TheThe YunyangYunyang turquoiseturquoise depositdeposit isis locatedlocated strata.strata. InIn spacespace,, ththee directiodirectionn ofof ththee mineralmineral atat anan intermediateintermediate latitudelatitude wherewhere humidhumid andand occurrenceoccurrence isis ththee samsamee asas thathatt ofof ththee overalloverall rainyrainy seasonsseasons alternatealternate withwith highhigh structuralstructural trentrendd ooff ththee stratastrata andand faults.faults. temperaturestemperatures andand drydry weather.weather. ThisThis weatherweather patternpattern isis favourablefavourable forfor thethe weathering,weathering, TheThe turquoisturquoisee ofteoftenn occuroccurss inin massivemassive leaching,leaching, migration,migration, concentrationconcentration andand nodulesnodules oorr aass veiveinn fillings.fillings. ItIt containscontains precipitationprecipitation ofof metallogenicmetallogenic elements.elements. concentricconcentric layerelayeredd structuresstructures resemblingresembling WeatheringWeathering andand erosionerosion havehave affectedaffected thethe specificspecific spheruliticspherulitic,, oolitiooliticc oorr pisolitipisoliticc bodies;bodies; ancientancient landland ofof WudangWudang forfor a longlong periodperiod ofof suchsuch structuresstructures araree characteristicharacteristicc ofof mineralsminerals time,time, andand a greatgreat numbernumber ofof metallogenicmetallogenic formedformed bbyy secondarysecondary leachingleaching processesprocesses materialsmaterials occuroccur inin thisthis district.district. TheirTheir (Mitchell(Mitchell et ah,al., 1978).1978). InIn verticaverticall section,section, thethe abundanceabundance inin thethe ore-bearingore-bearing rocksrocks isis tenstens ofof turquoiseturquoise deposidepositt iiss markedlmarkedlyy zonezonedd aass a timestimes thethe regionalregional backgroundbackground levels.levels. TheThe resultresult ofof groundground watewaterr activity.activity. coppercopper andand phosphorusphosphorus occuroccur mainlymainly inin AfterAfter comprehensivcomprehensivee analysisanalysis ooff thethe finelyfinely disperseddispersed sulphidessulphides inin thethe geologicalgeological features,features, ththee mineralmineral carbonaceous-siliceouscarbonaceous-siliceous slates,slates, andand inin thethe compositions,compositions, ththee paragenetiparageneticc mineralmineral irregularirregular patchypatchy colloidalcolloidal apatitesapatites assemblageassemblage anandd structuralstructural featuresfeatures ofof thethe (collophane).(collophane). turquoiseturquoise depositdeposit,, iitt isis concludedconcluded thathatt thethe TheThe intensityintensity ofof mineralizationmineralization isis turquoiseturquoise inin ththee YunyanYunyangg districdistrictt wawass formedformed controlledcontrolled byby lithology,lithology, structurestructure andand groundground byby secondarysecondary leachinleachingg processes.processes.

Turquoise fromfrom HubeiHubei Province,Province, ChinaChina ThereThere areare strongstrong indicationsindications thatthat thethe FayazFayaz,, H.,H., andand Forghani,Forghani, AH.,A.H., 1975.1975. TheThe turquoisturquoisee ofof Iran.Iran. turquoiseturquoise resourcesresources ofof thethe YunyangYunyang districtdistrict Rocks and and Minerals,Minerals, 50, 50 526-8, 526- 8 Hao Yongwei, et al., 1982. 1:200,000 Regional geological have much potential and are of possible Hao Yongwei, et al., 1982. 1:200,000 Regional geological have much potential and are of possible surveyingsurveying reporreportt inin YunyangYunyang,, HubeHubeii ProvinceProvince,, China,China, significantsignificant developmentdevelopment inin ththee future.future. Hubei Bureau of Geology and Mineral Resources,Resources, unpublished,unpublished,2-37 2-3 7 Ivanova,Ivanova, V.P.,V.P., 1974.1974. ThermoanalysisThermoanalysis ofof rockrockss andand minerals.minerals. AcknowledgementsAcknowledgements NedraNedra PressPress,, LeningradLeningrad,, 182-223182-223 KhorassaniKhorassani,, A.A,, andand Abedini,Abedini, M.P.,M.P., 1976.1976. A neneww studystudy ooff WeWe wouldwould likelike ttoo thanthankk ththee editorseditors ofof TheThe turquoisturquoisee fromfrom IranIran.. Mineral. Mag., Mag., 40,40 ,640-2 640-2 Journal ofof Gemmology Gemmology for fo theirr thei supportr suppor andt an d Mitchell,Mitchell, R.S.RS.,, et al., 1978.1978. Rocks and and Minerals, Minerals, 53, 53 214-8, 214- 8 helphelp inin revisingrevising thethe paper.paper. Moenke,Moenke, H.,H., 1962.1962. Mineralspektren I. Akademie-Verlag, I. Akademie-Verlag Berlin, Berli n PenPengg Yuanguo,Yuanguo, 1989.1989. TheThe originorigin andand prospectinprospectingg ooff turquoiseturquoise.. Information of geological science andand ReferencesReferences technology in in Hubei, Hubei, 2, 12-172, 12-1 7 ZhanZhangg HuifenHuifen,, JianJiangg Zechun,Zechun, et al., 1982.1982. TheThe investigationinvestigation AndersonAnderson,, W.R.W.R.,, 1962.1962. SecondarySecondary phosphatephosphatess fromfrom intointo turquoisturquoisee mineralogymineralogy.. JournaJournall of Mineralogy,Mineralogy, BinghamBingham,, Utah.Utah. Am. Miner., 47, 47 ,1303-9 1303-9 Guiyang, China, China, 4, 4254-61, 254-6 1

immnLONDON mmm®DIAM:OND ~EPORTmmm

12 12 The Cem Testing Laboratory

Diamond grading service established In 1980 Diamond grading service established in 1980 Each diamond graded by three experienced graders Each diamond graded by three experienced graders Report based on the current International grading Report baseproceduresd on the currenfor colourt internationa and clarityl grading procedures for colour and clarity Whether buying or seiling, tne London Diamond Report Whether buyinassuresg or theselling prestige, the Londo of yourn Diamon stone d Report assures the prestige of your stone

The cern Testing Laboratory of Creat Britain ThCACTLe Gem. 27 Testin Grevilleg Laborator Street. Londony of Grea EC1Nt Britai 8SU n TelephoneGAGTL, 27: Grevill0171·405e Street 3351 , FaLondox: 0171n EC1·8319479N 8SU Telephone: 0171-405 3351 Fax: 0171-831 9479

J. Gemm., 1998, 1998, 26,26,1,1-12 1, 1-12 Iridescence in plagioclase feldspars R.A. Howie Matlock, Derbyshire DE4 2AE

ABSTRACT: The play of colours shown by peristerite and some varieties of labradorite are an optical interference phenomenon caused by the occurrence of sets of plagioclase lamellae of two different compo- sitions and thicknesses. It is now becoming clear that these lamellar intergrowths are restricted to and caused by two immiscibility regions in the compositional range of the plagioclase series. These cause distinct differences in the precise structure of the resulting plagioclases and the sharp boundaries of the lamellae.

Introduction The advent of electron microscopy enabled the individual lamellae to be seen, or at least two hundred years, e.g. Nissen et al. (1967), but it is only now that mineralogists and gem lovers have the crystal physicists, crystallographers and marvelled at and enjoyed the strong thermodynamicists have been able to iridescence shown by some labradorite, ever provide a plausible scenario based on the since the first specimens of this material were plagioclase series as a whole. 13 brought back from Paul Island, off the coast of Labrador, Canada, reputedly by Mr Wolfe, It is believed that within the albite- a missionary, around 1770 (Dana, 1982). But anorthite series1 there are at least three although numerous explanations have been miscibility gaps due to structural transitions advanced for this phenomenon, the first (Figure 1). These were first mooted by Ribbe detailed scientific investigations were not (1962) and their tentative boundaries reported until Lord Rayleigh's paper to the outlined by McConnell (1974) and by Smith Royal Society in 1923 and that of Boggild in and Brown (1988), but the paper by 1924. Rayleigh (1923) made a detailed study Carpenter (1994) proposed an equilibrium of the optical scattering and calculated that phase diagram relating the three miscibility the intergrowth texture giving rise to this gaps to breaks in the ordering behaviour as a scattering was ~6 pm across. Over the next function of composition across the plagio- two to three decades further work began to clase series. It is unlikely to be a coincidence establish the existence of a layered structure, that iridescence is seen in the exact composi- the iridescence in the visible range being an tional ranges of these three gaps. These gaps interference phenomenon (reminiscent of have become known as the peristerite gap, that seen in opal) due to the periodicity of the the Boggild gap and the Huttenlocher gap layered lamellar structures. (Pe, Bo, Hu in Figure 1).

It was known from chemical analyses that As mentioned above, the iridescence is an no impurities or inclusions were responsible interference phenomenon and occurs for this effect and that somehow plagioclase because the lamellar intergrowths are on with more than one composition was present. the same submicroscopic scale as the

1. For further details of feldspar nomenclature, etc., see, for example, Deer et at., 1992.

© Gemmological Association and Gem Testing Laboratory of Great Britain ISSN: 1355-4565 15001500

HA HAHAssS S HA HAHA HAHAssS S HAHA HAHAssS S HA HA 12001200 HA HAssS S HAHA HAHAssS S HAHA HAHAssS S / / u / 2 800 h°- 800 \ LA ~ /:\ /" * * 400 Pe _ IntermediateIntermediate _ * structurestructure P-An I P-An-.....z...^ 00 I I I I I I I I I L_ 00 1010 2020 3030 404 0 505 0 606 0 707 0 808 0 909 0 10010 0 AlbiteAlbite OligoclaseOligoclase AndesineAndesine LabradoniteLabradonite Bytownite Bytownite AnorthiteAnorthit e

NaANaAlSilSip30 s8 CaALzSipCaAl2Si2Os g MoMoll. .% %An A n

Figure 1: Schematic illustration of variation in crystal structure across thethe plagioclaseplagioclase series. series. HA, HA, high high albite; I-An,I-An, body-centredbody-centred anorthite;anorthite; LA,LA, lowlow albite;albite; P-An, P-An, primitiveprimitive anorthite;anorthite; ss ss (subscript)(subscript) indicatesindicates solid solution; Pe, peristerite intergrowth; Be, Beggild intergrowth; Hu, Huttenlocher intergrowthintergrowth 1414 (after Deer etet al.al.,, 1992). * RegionsRegions ofofl-feldspar 2-feldspar intergrowth.intergrowth.

Figure 2: Peristerite: sodic plagioclase showing wavelengtwavelengthh ofof visiblvisiblee light,light, i.e.i.e. a fefeww hundredhundred 'delicate' interference colours. nanometresnanometres.. InIn ththee plagioclasplagioclasee serieseriess thertheree areare twtwoo compositionalcompositional rangerangess whicwhichh mamayy showshow iridescence,iridescence, thosthosee representinrepresentingg a compositioncomposition ooff ththee peristeritperisteritee gagapp anandd ththee bettebetterr knownknown labradorescencelabradorescence iinn ththee BoggilB0ggildd gap.gap.

PeristerescencePeristerescence Peristerescence isis restricterestrictedd ttoo thosethose plagioclaseplagioclasess inin ththee albite-oligoclasealbite-oligoclase (AnCAn17)(An^An^) rangrangee whicwhichh showshow a plaplayy ooff colourcolourss (or(or schiller)schiller) reminiscenreminiscentt ofof thosthosee onon ththee necneckk ooff a pigeopigeonn (Gree(Greekk peristera)peristera).. TheThe namnamee wawass givengiven bbyy ThomsonThomson (1843)(1843) forfor a specimenspecimen ofof iridescentiridescent albitealbite inin a graniticgranitic pegmatitpegmatitee frofromm PerthPerth,, Ontario.Ontario. PeristeritePeristerite hahass sincesince beebeenn describedescribedd frofromm Froland,Froland, NorwayNorway,, anandd frofromm manmanyy otheotherr localitielocalitiess inin OntarioOntario anandd ththee U.S.AU.S.A.. (Flee(Fleett & RibbeRibbe,, 1965)1965) anandd EuropEuropee (Nisse(Nissenn et al,al., 1967).1967). ThThee colourscolours areare generallgenerallyy mormoree delicatdelicatee thathann forfor labradorescencelabradorescence,, oftenoften appearingappearing oonn a whitewhite oorr buff-colourebuff-colouredd plagioclasplagioclasee (Figure 2). FromFrom

J. Gemm., 1998, 26,26,1,13-16 1, 13-16 detailedetailedd worworkk witwithh ththee electroelectronn microscopmicroscopee anandd ththee electroelectronn microprobemicroprobe,, iitt hahass beebeenn showshownn thathatt ththee colourcolourss araree produceproducedd bbyy alternatinalternatingg planaplanarr thicthickk anandd thithinn lamellalamellaee ooff albitalbitee (An(Ana)0) anandd oligoclasoligoclasee (An252s))', respectivelyrespectively.. ThThee sodisodicc componencomponentt iiss orderedordered low-temperaturlow-temperaturee albitalbitee whilwhilee ththee calcicalcicc componencomponentt appearappearss ttoo bbee leslesss welwelll ordereorderedd oligoclaseoligoclase,, ththee compositionacompositionall differencedifference beinbeingg ooff ththee ordeorderr ooff 2020%% AnAn.. ThThee albitalbitee lamellalamellaee araree alwayalwayss considerablconsiderablyy thickethickerr thathann ththee oligoclasoligoclasee lamellaelamellae,, generallgenerallyy bbyy 2:12:1;; mosmostt simplesimple lamellalamellarr peristeriteperisteritess havhavee periodicitieperiodicitiess foforr a + b ooff 50-30050-300 nm.

LabradorescencLabradorescencee Figure 3:3: LabradoritLabradorite:e: intermediate intermediate plagioclase plagioclase showing strong strong interference interference qolours. colours. ThThee seconsecondd anandd mormoree familiafamiliarr typtypee ooff plagioclasplagioclasee iridescenciridescencee occuroccurss iinn ththee andesine-labradoritandesine-labradoritee (An44s5 - An6060)) rangrangee andand thicknesthicknesss witwithh increasinincreasingg AAnn contencontentt anandd thethe iiss knowknownn aass labradorescence. After Afte rbeing bein g An-poor setset decreases decreases slowly slowly. The The differences differ­ originalloriginallyy founfoundd iinn orthopyroxene­orthopyroxene- ences iinn compositiocompositionn betweebetweenn ththee twtwoo setsetss ooff plagioclasplagioclasee gabbrgabbroo aatt PauPaull IslandIsland,, i itt iiss nownow lamellae areare -12-15~ 12-15 mol. mol. perper cent cent An, An, typically typi­ knownknown ttoo occuroccur inin ththee adjacenadjacentt NainNain cally fromfrom ~An~An45-4645^6 ttoo An58S8-{,()^0.. MiUraMiura et alal.. gabbroicgabbroic complexcomplex onon ththee mainlanmainlandd ooff (1975)(1975) proposedproposed a modelmodel witwithh a schematicschematic LabradorLabrador andand inin manymany PrecambrianPrecambrian arrangementarrangement asas shownshown inin Figure 44 for fo r twotw o 1515 basic/ultrabasibasic/ultrabasicc igneousigneous rocksrocks worldwide.worldwide. compositionalcompositional varietiesvarieties ofof plagioclase,plagioclase, AsAs iinn peristerite,peristerite, labradorescencelabradorescence isis aann termedtermed a andand bb.. MoreMore recently,recently, aann interferencinterferencee phenomenonphenomenon duedue toto reflectedreflected investigationinvestigation ofof B0ggildBoggild intergrowthintergrowth iinn lightlight waveswaves fromfrom a multilayermultilayer assemblageassemblage ooff plagioclaseplagioclase fromfrom YUimma,Ylamma, Finland,Finland, usingusing twtwoo periodicallyperiodically stackedstacked lamellarlamellar structures.structures. high-resolutionhigh-resolution transmissiotransmissionn electronelectron TheThe colourscolours displayeddisplayed areare inin thethe blue, reredd microscopymicroscopy demonstratedemonstratedd thethe occurrenceoccurrence ooff andand yellowyellow partsparts ofof thethe spectrum,spectrum, thethe overalloverall twotwo phasephasess ofof compositioncomposition An6600 andand An4An47 forfor effecteffect beingbeing somewhatsomewhat darkerdarker thanthan foforr the thicker and thinnerthinner lamellae,lamellae, respectivelyrespectively peristeriteperisterite (Figure 3) 3).. NissenNissen etet alah. (1967)(1967 ) carriedcarried outout electronelectron microprobemicroprobe analysesanalyses ooff Figure 4: 4: SchematicSchematic representation representation of a modelof a model for for aroundaround 100100 specimensspecimens andand checkedchecked ththee lamellar structure structure in iniridescent iridescent labradorite labradorite (after (after presencepresence ofof a submicroscopicsubmicroscopic layeredlayered Miura etet aI.,al, 1975).1975). structurestructure byby electronelectron microscopy.microscopy. TheyThey foundfound thatthat allall thethe iridescentiridescent specimensspecimens containedcontained anan appreciableappreciable amountamount ofof thethe potassiumpotassium n feldsparfeldspar (orthoclase(orthoclase KAISips)KAlSi3Og) moleculemolecule n (now(now generallygenerally putput atat ~2.5%)~2.5%) andand thatthat ththee ~~~ ____+.~ __~ a 2 wavelength of the average iridescence wavelength of the average iridescence nb (colour)(colour) increasedincreased withwith thethe AnAn contentcontent (blue(blue An ----~LT+------3 48.s-52' green-yellow An52_555, orange-red na An48.5-52' green-yellow AnS2-55.5' orange-red An55_558). The lamellar periodicities for a. + b -r~; 4 } AnS5-55.s). The lamellar periodicities for a + b areare ~50-280-50-280 nm,nm, butbut inin labradorescencelabradorescence ththee b : periodicitperiodicityy difference in thicknesses of the two r -'-______ee!!J~+:p. a~...~ __-'- ' 2N-l a+ bb difference in thicknesses of the two a n 2N-1 f alternatingalternating lamellaelamellae isis ratherrather small,small, althoughalthough -r------~~--~a 22NN \ thethe moremore An-richAn-rich setset increasesincreases rapidlyrapidly iinn

IridIridescenceescence in plagioclase feldspars feldspars (Hoshi(Hoshi et al.,ah, 1996),1996), witwithh a bulbulkk compositioncomposition DanaDana,, E.5.,E.S., 1892.1892. The System of Mineralogy (6th (6t hedition). edition) . NewNew YorYorkk (John(John WileyWiley & Sons,Sons, Inc),Inc), lxiv,1xiv, 11341134 ofof AnS6565.5;; thethe matchinmatchingg ofof ththee crystalcrystal latticeslattices across the exsolution lamellae was noted. DeerDeer,, W.A.W.A.,, HowieHowie,, R.A.R.A.,, andand ZussmanZussman,, J.J.,, 1992.1992. An across the exsolution lamellae was noted. Introduction to to the the Rock-Forming Rock-Forming Minerals Minerals (2nd edition).(2nd edition) . LondonLondon (Longman),(Longman), xvi,xvi, 696696 Fleet,Fleet, S.G.,S.G., andand RibbeRibbe,, P.H.P.H.,, 1965.1965. AAnn electron-microscopeelectron-microscope HuttenlocherHuttenlocher intergrowthintergrowth studystudy ofof peristeriteperisterite plagioclases.plagioclases. Min. Mag., 35, 35 ,165-76 165-76 HoshiHoshi,, T.,T., Tagai,Tagai, T.,T. ,and and Suzuki, Suzuki ,M., M. ,1996. 1996 .Investigation Investigation on on TheThe thirdthird ofof ththee miscibilitymiscibility gapsgaps inin thethe BoggildBøggild intergrowthintergrowth ofof intermediateintermediate plagioclasplagioclasee byby plagioclaseplagioclase seriesseries isis inin ththee calciccalcic labradorite­labradorite- high-resolutiohigh-resolutionn transmissiotransmissionn electronelectron microscopy.microscopy. ZZ.. Krist., 211, 211 ,879-883 879-883 bytownite range (~An(-An67-A~o)'-An ). The lamellar bytownite range 67 90 The lamellar McConnellMcConnell,, J.D.C.J.D.C.,, 1974.1974. AnalysisAnalysis ofof thethe structurestructure inin thithiss regionregion isis calledcalled thethe time-temperature-transformatiotime-temperature-transformationn behavioubehaviourr ofof thethe HuttenlocherHuttenlocher intergrowthintergrowth andand cancan bebe seenseen byby plagioclase feldspars.feldspars. In:In: MacKenzie,MacKenzie, W.S.,W.S., andand electronelectron microscopymicroscopy.. ItIt isis mucmuchh coarsercoarser thanthan ZussmanZussman,, J.J. (eds).(eds). The Feldspars. Manchester Mancheste rUniv. Univ . intergrowthsintergrowths inin thethe moremore sodicsodic partpartss ofof thethe PressPress,, Manchester,Manchester, 460-7460-777 Miura,Miúra, Y.Y.,, Tomiska,Tomiska, T.,T. ,and and Kato, Kato ,T., T. 1975., 1975 Labradorescence. Labradorescenc e plagioclaseplagioclase seriesseries andand soso isis unlikelyunlikely ttoo showshow andand ththee idealideal behaviobehaviorr ofof thicknessesthicknesses ofof alternatealternate ananyy visiblevisible iridescenceiridescence - indeedindeed nonenone hashas yetyet lamellalamellaee iinn ththee BoggildBøggild intergrowth.intergrowth. Min. J. (Japan),(Japan), 7, 7, beebeenn discovered.discovered. 526-41526-41 NissenNissen,, H.-D.,H.-U., EggmanEggman,, H.H.,, andand LavesLaves,, F.,E, 1967.1967. SchillerSchiller andand submicroscopicsubmicroscopic lamellaelamellae ofof labradorite.labradorite. A ReferenceReferencess preliminarypreliminary report.report. Schweiz. Min. Petr.Petro Mitt., 4747,, 289-30289-3022 BøggildBoggild,, O.B.,O.B., 1924.1924. OnOn ththee labradorizationlabradorization ofof thethe RayleighRayleigh,, L.,L., 1923.1923. StudiesStudies ofof iridescentiridescent colourcolour andand thethe feldspars.feldspars. K. Danske VidenskVidensk Selsk. Selsk. Mat.-Fys. Mat.-Fys. Meddel., Meddel., structurestructure producingproducing itit:: IIIIII.. ThThee colourscolours ofof labradoritelabradorite 6(3},1-796(3), 1-79 feldspar.feldspar. Proc.Roy.Soc.London, l03A, 103A 34-5, 34- 5 Carpenter,Carpenter, M.A.,M.A., 1994.1994. SubsolidusSubsolidus phasphasee relationsrelations ofof thethe Smith,Smith, J.V.,J.V., andand Brown,Brown, W.L.W.L.,, 1988.1988. Feldspar Minerals: Minerals: 1. 1. plagioclaseplagioclase feldsparfeldspar solidsolid solution.solution. InIn:: Parsons,Parsons, II.. (ed)(ed) Crystals Structures, Structures, Physical, Physical, Chemical Chemical and Microtextural and Microtextural Feldspars and and their their Reactions, Reactions, Dordrecht Dordrech (Kluwert (Kluwe Acad.r Acad . Properties. Berlin, Berlin Heidelberg, Heidelber g& &New New York Yor k(Springer­ (Springer- 1616 Publishers},221-69Publishers), 221-69 Verlag),Verlag), xviiixviii,, 828288

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J. Gemm., Gemm., 1998, 1998,26,1,13-16 26, 1, 13-16 Notes from the Gem and Pearl Testing Laboratory, Bahrain - 6

Ali Safar, FGA, and Nick Sturman, FGA, DGA Gem and Pearl Testing Laboratory of Bahrain, Ministry of Commerce, P.O. Box 5479, Manama, State of Bahrain

ABSTRACT: Owing to amber's frequent use as prayer beads in the Middle East, we test quite a few pieces each month and these generally include some interesting or unusual examples. In these notes we will describe the surface enhancement, cavity filling, 'construction of and repair to' and chatoyancy observed in five amber prayer beads that were submitted for examination. The notes end with three items on pearls.

Surface-enhanced amber was tested with a thermal probe to see if urface-enhanced amber is a topic we more of the 'surface colour' could be have discussed on more than one removed to reveal the true underlying Soccasion in 'Notes from the Gem and colour. This was carefully done to avoid Pearl Testing Laboratory of Bahrain' spoiling the appearance of the bead's (Scarratt, 1992; Bubshait and Sturman, 1993). surface. Once removed (the material that was 17 The reason for mentioning it again is that the removed gave a typical resinous 'amber' colour difference between the surface area odour) the colour difference was more and the underlying 'body colour' of the 33 noticeable (Figure 1). Because it was difficult round beads, two disc-shaped spacers and one cylindrically-shaped terminating bead Figure 1: The obvious colour difference between (the Arabic name for this bead is 'Shaahed') the surface and interior of colour-enhanced is exceptional. The row appeared semi- amber. opaque to opaque, dark red to almost black when viewed under an ordinary desk lamp, and black in daylight. However, under a fibre-optic light source a translucent orange/red colour was observed, although it was still difficult to get a clear view of the interior as the light did not penetrate effec- tively even at full intensity. A saving grace for us was that the 'Shaahed bead' had been broken in two and this allowed the end of the fibre-optic light source to be placed right up against its 'interior surface'. It was evident that the pale yellow interior of this bead was markedly different from the dark orange /red marginal colour. With the customer's permission a small area around the fracture

© Gemmological Association and Gem Testing Laboratory of Great Britain ISSN: 1355-4565 Figure 2: The head sectionsection ofof thethe praying-mantispraying-mantis Figure 3: Air bubbles trapped within the filler inin like insect.insect. amber (transmitted light).light).

toto inspectinspect thethe interiorinterior structurestructure ofof thethe beadsbeads involved.involved. HoweverHowever,, twtwoo setssets ofof amberamber prayerprayer andand findfind sufficientsufficient evidenceevidence forfor a naturanaturall oror beadsbeads examinedexamined recently,recently, submittedsubmitted byby pressedpressed structure,structure, thesethese beadbeadss werweree returnedreturned differentdifferent customerscustomers atat differentdifferent times,times, ttoo ththee customercustomer withwith onlyonly a verbaverball report.report. revealedrevealed interestininterestingg fillings.fillings. The customercustomer was was told told that that tests tests were were inconclusive incon­ TheThe firstfirst setset consistedconsisted ofof beadbeadss thatthat clusive andand furtherfurther progresprogresss wawass onlyonly containedcontained a numbernumber ofof goodgood insectinsect inclusionsinclusions possiblpossiblee throughthrough removaremovall ofof thethe colouredcoloured inin mostlmostlyy clearclear amber,amber, includingincluding whatwhat skinskin - eithereither fromfrom a necklacenecklace beadbead oror fromfrom appearedappeared ttoo bbee ththee heaheadd sectionsection ofof a praying­praying- material of of the the same same type. type. mantis-likemantis-like specimenspecimen (Figure 2).2). UnfortunatelUnfortunatelyy thithiss inclusioninclusion wawass awkwardawkward 1818 FilledFilled amberamber beadsbeads toto photograph.photograph. MostMost fillingsfillings werewere confinedconfined toto smallsmall surfacesurface cavities,cavities, butbut twotwo oror threethree AlthoughAlthough filledfilled stonesstones areare oftenoften surfacesurface reachingreaching fracturesfractures runninrunningg throughthrough mentionementionedd inin gemmologicalgemmological literature,literature, itit isis somesome beadsbeads werewere alsoalso filled.filled. OneOne usuallusuallyy thethe mormoree costlycostly gemstonesgemstones suchsuch asas characteristiccharacteristic ofof thesthesee particularparticular fillingsfillings waswas diamond,diamond, rubrubyy andand emeraldemerald thatthat areare thathatt numerounumerouss airair bubblebubbless werewere foundfound asas inclusionsinclusions withinwithin ththee fillerfiller (Figure 3). InIn reflected light some of these bubbles were Figure 4: The same subject as Figure 3 in reflected light some of these bubbles were reflected light.light. NoteNote thethe 'blow'blow holes'.holes'. evidentevident asas 'blow-holes''blow-holes' onon ththee surfacesurface (Figure 4 transmittetransmittedd andand reflectereflectedd lightlight samesame feature).feature). TheThe secondsecond rowrow comprisingcomprising 3333 prayerprayer beadsbeads,, weigheweighedd approximatelyapproximately 650650 caratscarats andand diddid notnot containcontain insectinsect inclusions.inclusions. TheThe beadbeadss werewere mostlmostlyy transparentransparentt toto translucenttranslucent,, clearclear ttoo cloudy,cloudy, yellowyellow oror yellow/orangyellow / orangee andand showedshowed evidenceevidence ofof heatheat treatment.treatment. HoweverHowever,, asas itit isis nonott rarraree forfor amberamber toto bbee heatheat treatetreatedd thesthesee days,days, itit waswas notnot thithiss thatthat interestedinterested usus butbut a numbenumberr ooff fillings.fillings. OnOn thethe wholewhole ththee beadsbeads werweree finefine andand unaffectedunaffected,, bubutt ththee 'Shaahed''Shaahed' beabeadd (see(see 'constructed'constructed Shaahed'Shaahed' below)below),, twotwo carvedcarved cylindrically-shapedcylindrically-shaped spacersspacers andand oneone ovaloval beadbead werweree eacheach selectivelselectivelyy filled.filled. TheThe materiamateriall useusedd ttoo fillfill ththee 'Shaahed''Shaahed' lookedlooked

J. Gemm., 1998, 26,26,1,17-23 1, 17-23 Figure 5: Large filled area in one of the oval Figure 6: An air bubble trapped in the adhesive amber beads. used to repair aa bead.bead. quitequite differentdifferent fromfrom thathatt usedused ttoo fillfill thethe otherother ththee otherother beadbeadss inin thethe rowrow andand alsoalso fromfrom a threethree beads.beads. InIn thethe 'Shaahed','Shaahed', oneone endend ofof anan singlesingle piecepiece ofof suchsuch material.material. ThereThere areare alsoalso unusedunused drill-holedrill-hole waswas filledfilled withwith whatwhat goldgold oror silversilver 'Shaaheds''Shaaheds' whicwhichh areare oftenoften appearedappeared toto bbee a transparent,transparent, possiblypossibly moremore durabledurable thanthan amber.amber. InIn manymany stringsstrings ooff colourlescolourlesss oorr yelloyelloww adhesive,adhesive, whilswhilstt thethe beadbeadss wwee havhavee examined,examined, ththee 'Shaahed''Shaahed' hashas fillerfiller useusedd onon thethe otheotherr threethree beadbeadss tooktook onon a sufferedsuffered breakagbreakagee andand thenthen beebeenn repaired,repaired, cloudy,cloudy, translucenttranslucent toto opaqueopaque appearance,appearance, witwithh varyingvarying degreesdegrees ofof skill,skill, usingusing anan thatthat couldcould easilyeasily bbee mistakemistakenn forfor thethe adhesive.adhesive. ThisThis probleproblemm isis nonott surprisingsurprising frequentlyfrequently seenseen cloudycloudy areasareas inin somesome typestypes ooff givengiven thethe ratiratioo ofof thicknessthickness toto lengthlength ofof thethe translucenttranslucent toto opaqueopaque amber.amber. TheThe cloudycloudy 'Shaahed''Shaahed' andand ththee sometimessometimes roughrough fillerfiller wawass mosmostt apparentapparent inin ththee ovaloval bead,bead, handlinhandlingg thatthat thethe prayeprayerr beadbeadss experience.experience. 1919 wherewhere itit hahadd beenbeen usedused toto fillfill a largelarge surface­surface- TheThe repairerepairedd areaarea isis usuallusuallyy ververyy easyeasy toto reachinreachingg cavitycavity (Figure 5), originallyoriginally eithereither a detect,detect, andand commonlycommonly containscontains oneone oror moremore gasgas bubblbubblee oror perhapsperhaps eveneven thethe locatiolocationn ofof a bubblebubbless inin ththee adhesiveadhesive (Figures 6 and 7). pollepollenn grain.grain.

TheThe fillersfillers inin botbothh setssets ofof prayerprayer beadsbeads Figure 7: The constructed Shaahed. Note the werweree firstfirst detecteddetected bbyy opticaloptical examination.examination. translucency of the central section, compared to Secondly,Secondly, exposureexposure ttoo ultravioleultraviolett lightlight the pieces on either side. This bead waswas fashionedfashioned revealedrevealed a subtlesubtle differencedifference inin fluorescencefluorescence from three separate piecespieces of of amber amber that that had had been been thatthat couldcould easilyeasily havehave beebeenn overlooked,overlooked, asas bonded together with adhesive. thethe fluorescencefluorescence ofof thethe largerlarger amberamber beadsbeads maskedmasked ththee fluorescencefluorescence ofof ththee filler.filler. Finally,Finally, thethe thermal-probethermal-probe providedprovided confirmationconfirmation ooff ththee presencpresencee ofof fillersfillers inin botbothh setssets ofof beads;beads; eacheach meltedmelted andand gavegave wax-likewax-like odours.odours. AlthougAlthoughh wwee coulcouldd nonott identifyidentify ththee fillers,fillers, theythey werweree significantlysignificantly differentdifferent fromfrom amber.amber.

RepairedRepaired andand constructedconstructed 'Shaahed''Shaahed' beadsbeads A Shaahed,Shaahed, thethe ArabicArabic namename givengiven toto thethe 'turned''turned' cylindricalcylindrical beadbead thatthat commonlycommonly terminatesterminates a rowrow ofof prayeprayerr beadbeadss (Figure 7), isis usuallyusually fashionedfashioned fromfrom thethe samesame materialmaterial asas

Notes from the Gem and Pearl Testing Laboratory Bahrain - 6 Figure 8:8: TheThe chatoyant chatoyant effect effect noted noted in one in onebead bead Figure 9: 9: The The 'banded'banded'' internal internal structure structure partly partly fromfrom aa rowrow of of prayer prayer beads beads.. responsible for for the the chatoyancy chatoyancy seen seenin Figure in Figure 8. 8.

ChatoyancChatoyancyy iinn ambeamberr ooff prayeprayerr beadsbeads,, wwee werweree surprisesurprisedd ttoo findfind ononee beabeadd thathatt appeareappearedd ttoo displadisplayy a IfIf studentstudentss abouaboutt ttoo sisitt theitheirr gemmologygemmology chatoyanchatoyantt effeceffectt neanearr ththee drill-holdrill-holee (Figure 8). 8). examinatioexaminationn werweree askeaskedd ttoo namnamee anyany chatoyanchatoyantt gemstonegemstone,, thetheyy woulwouldd probablyprobably CloseCloserr examinatioexaminationn revealerevealedd thathatt iitt wawass a suggessuggestt ththee namenamess ooff ththee mormoree likellikelyy stonestoness chatoyanchatoyantt effeceffectt produceproducedd bbyy finelfinelyy bandedbanded sucsuchh aass chrysoberylchrysoberyl,, quartzquartz,, tiger's-eye,tiger's-eye, streamstreamss ooff minutminutee bubblebubbless (Figure 9) 9) combined combine d apatiteapatite,, tourmalintourmalinee oorr scapolitescapolite.. IItt woulwouldd bbee witwithh a serieseriess ooff 'chatte'chatterr marksmarks'' iinn ththee samsamee doubtfudoubtfull iiff anyonanyonee woulwouldd mentiomentionn ambeamberr directiodirectionn oonn ththee surfacsurfacee ooff ththee bead.. ThThee becausbecausee iitt iiss nonott iinn ththee textextt bookbookss andand untiluntil chattechatterr markmarkss seemeseemedd ttoo enhancenhancee ththee ratheratherr weak chatoyant effect from the internal ververyy recentlrecentlyy wwee hahadd nonott seenseen a convincingconvincing weak chatoyant effect from the internal bubbles. As with obsidian, this is considered to 2020 exampleexample.. However,However, whewhenn wwee werweree carryingcarrying bubbles. As with obsidian, this is considered to be an accidental optical effect and not to be ououtt a routinroutinee inspectioinspectionn ooff ththee beadbeadss inin a rowrow be an accidental optical effect and not to be consideredconsidered iinn ththee samesame wawayy asas chatoyantchatoyant varietievarietiess ofof chrysoberylchrysoberyl oorr tourmalintourmalinee whosewhose Figure 10: The 29.22 ct non-nacreous andand opticaopticall effecteffectss araree structurallystructurally controlled.controlled. nacreous, brown brown and and white white pearl. pearl. NNon-nacreou on-nacreouss andand nacreounacreouss pearpearll MosMostt ooff ththee pearlpearlss thatthat gemmologicalgemmological laboratorieslaboratories aroundaround ththee worldworld examineexamine duringduring theirtheir day-to-dayday-to-day routinroutinee areare nacreous.nacreous. AlthoughAlthough thesethese pearlspearls areare commerciallycommercially moremore desirable,desirable, thethe majoritymajority ofof gemmologistsgemmologists andand jewellersjewellers alsoalso knowknow thatthat thertheree areare certaincertain non-nacreous pearls that areare alsoalso veryvery desirable,desir­ able, butbut muchmuch harderharder toto findfind inin goodgood quality.quality. TheseThese includeinclude pearlspearls fromfrom variousvarious varietiesvarieties ofof conch,conch, namelynamely queenqueen conchconch (Strombus[Strombus gigas],gigas], horsehorse conchconch [Pleuroploca[Pleuroploca gigantealgigantea] andand MeloMelo volutesvolutes asas wellwell asas pearlspearls fromfrom otherother molluscsmolluscs suchsuch asas thethe giantgiant damclam (Tridacna(Tridacna gigas)gigas) andand otherother lesser-knownlesser-known species. TheseThese speciesspecies alwaysalways produceproduce non-nacreousnon-nacreous pearls,pearls, unlikeunlike thethe nacreousnacreous pearl-producingpearl-producing speciesspecies whichwhich cancan produceproduce bothboth kindskinds (Bubshait(Bubshait andand Sturman, 1994, Hurwit,Hurwit, 1989,1989,1991). 1991).

J.J.Gemm., Gemm., 1998,1998,26,1,17^13 26, 1, 17-23 A dark-browndark-brown pearlpearl (Figure 10), submittedsubmitted forfor examinationexamination bbyy AI-MajidAl-Majid Jewellery, showedshowed thisthis interesting interesting phenomenon pheno­ menon onconcee againagain.. TheThe undrilledundrilled pearl,pearl, weighingweighing 29.229.222 ctct,, anandd measuringmeasuring approximatelapproximatelyy 18.21-18.3418.21-18.34 x 14.5114.51 mm,mm, waswas founfoundd iinn ththee ArabiaArabiann GulGulff overover fortfortyy yearsyears agagoo anandd hahass beebeenn iinn ththee possessiopossessionn ooff thethe AlAl­- MajidMajid familyfamily everever since.since. ThThee button-shapedbutton-shaped (bouton)(bouton) pearpearll appearappearss darkdark browbrownn overover mostmost ofof itsits surface,surface, bubutt possessepossessess a whitewhite circularcircular areareaa atat ititss basebase.. TheThe wholwholee ofof thethe browbrownn areaarea isis non-nacreousnon-nacreous,, whilstwhilst thethe whitewhite areareaa iiss nacreousnacreous.. SinceSince ththee pearpearll waswas undrilledundrilled,, anan adhesiveadhesive waswas useusedd toto mountmount iitt intintoo a rinringg foforr displadisplayy aatt anan exhibitionexhibition inin BahrainBahrain.. OnOnee ooff ththee AI-MajidAl-Majid brotherbrotherss triedtried ttoo recalrecalll frofromm whatwhat speciesspecies ooff oysteroyster thethe pearpearll waswas foundfound anandd althougalthoughh unsurunsuree (h(hee wawass a youngyoung boboyy aatt thethe time),time), thoughthoughtt thathatt iitt mamayy havehave beebeenn fromfrom 'th'thee samesame typetype ooff oysteroyster Figure 11: Orange-red fluorescence displayed by thatthat produceproducess th thee usuausuall (nacreous)(nacreous) pearls',pearls', the naturally coloured brown part of the brown i.e.i.e. PinctadaPinctada radiataradiata.. HoweverHowever,, consultationconsultation and white pearl. witwithh ththee BahrainBahrain CentreCentre foforr StudiesStudies & Research and another pearl merchant with a Research and another pearl merchant with a ThThee reactioreactionn ooff ththee pearpearll ttoo ultra-violetultra-violet large stock of this type of pearl suggested that large stock of this type of pearl suggested that lighlightt wawass additionalladditionallyy ooff greagreatt interestinterest.. Figure 21 21 the oyster often, but not solely, responsible the oyster often, but not solely, responsible 11 showsshows thathatt ththee pearpearll fluorescefluorescedd a strongstrong for producing this type of non-nacreous for producing this type of non-nacreous orangey-reorangey-redd colourcolour overover ththee browbrownn areaareass andand pearl (usually under 5-6 mm) is Pinctada pearl (usually under 5-6 mm) is Pinctada a typicaltypical blue-whiteblue-white overover thethe nacreousnacreous areaarea atat margaritifera. Exactly which of these two margaritifera. Exactly which of these two ththee basebase.. ThiThiss reactioreactionn fitsfits inin witwithh thosthosee seenseen species produced this particular pearl is species produced this particular pearl is iinn otherother completelcompletelyy ttoo partiallpartiallyy colouredcoloured unclear. unclear. brownbrown,, blacblackk oorr greygrey pearlspearls examinedexamined Gemmologically,Gemmologically, thithiss pearpearll wawass veryvery previouslpreviouslyy includingincluding ththee famoufamouss HopeHope PearlPearl interesting,interesting, becausbecausee onon firstfirst impressioimpressionn ththee (Kennedy(Kennedy et aI.,ah, 1994)1994) anandd iiss generallygenerally whitwhitee areareaa oonn ththee basbasee lookelookedd aass ifif itit couldcould consideredconsidered toto bbee prooprooff thathatt thethe coloucolourr iiss havhavee beebeenn 'fixed'fixed'' intointo positiopositionn witwithh anan naturalnatural.. TheThe brighbrightt blue/whitblue/whitee fluorescingfluorescing adhesivadhesivee ttoo fillfill a surfacesurface cavitycavity.. However,However, nono areaareass iinn thethe crackcrackss appeareappearedd ttoo resulresultt fromfrom features indicatingindicating a a cavity cavity of of any any description descrip­ residuaresiduall adhesiveadhesive useusedd toto fixfix ththee pearpearll inin thethe tion coulcouldd bbee foundfound witwithh eithereither a microscopemicroscope rinringg foforr displaydisplay,, describeddescribed aboveabove.. FoForr oorr mormoree importantlyimportantly bbyy usinusingg X-radiography.X-radiography. interestinterest,, wwee contactedcontacted a numbenumberr ooff naturalnatural ClosClosee examinatioexaminationn ooff ththee junctiojunctionn betweenbetween pearpearll dealersdealers iinn ManamaManama (Bahrain's(Bahrain's capital)capital) thethe nacreousnacreous andand non-nacreounon-nacreouss 'junction''junction' andand askeaskedd ifif wwee couldcould browsbrowsee throughthrough theirtheir alsalsoo revealerevealedd that,that, althoughalthough a crackcrack rarann allall stocksstocks ofof brown/blacbrown/blackk pearlpearlss toto trtryy anandd findfind ththee wawayy around,around, a veryvery smalsmalll portioportionn ooff thethe similarsimilar examplesexamples foforr comparisoncomparison.. AfterAfter non-nacreounon-nacreouss areareaa wawass naturallnaturallyy intergrownintergrown browsinbrowsingg througthroughh numerousnumerous lotslots ooff pearlspearls,, witwithh thethe nacreounacreouss areaarea.. OnOnee possiblpossiblee reasonreason onlonlyy a fewfew werweree founfoundd toto possespossesss part­part- forfor developmendevelopmentt ooff a craccrackk betweebetweenn thethe nacreousnacreous andand part-non-nacreoupart-non-nacreouss sections,sections, nacreounacreouss andand non-nacreounon-nacreouss areasareas,, isis thatthat anandd theirtheir featurefeaturess werweree similarsimilar toto thosethose overover timtimee ththee climateclimate togethetogetherr witwithh naturalnatural describedescribedd foforr ththee largelarge pearpearll discusseddiscussed ageinageingg hahadd produceproducedd naturalnatural shrinkageshrinkage inin aboveabove.. TheThe varievariedd fluorescencefluorescence ooff threthreee ooff one or both substances.substances. thesethese pearlspearls cancan bebe seenseen inin Figure 12. 12.

Notes from the Gem and Pearl Testing Laboratory Bahrain - 66 Figure 13: Radiograph showing the curiouscurious internal structure of the pearl purchased in Figure 12: Three brown pearls showing red-red­ Hong Kong (the opaque area aroundaround thethe pearlpearl isis orange fluorescence. due to lead).lead).

UpdatUpdatee oonn pearl-producinpearl-producingg areaareass freshwatefreshwaterr pearlpearlss frofromm ChinChinaa anandd possiblypossibly VietnaVietnamm araree alsoalso currentlycurrently availableavailable IInn discussiondiscussionss witwithh ththee BandaBandarr LengehLengeh 2222 throughouthroughoutt ththee MiddlMiddlee EasEastt andand thesthesee areare FisherieFisheriess CompanyCompany (Iran(Iran)) wwee havhavee learnedlearned generallgenerallyy mormoree prolifiprolificc thathann ththee JapaneseJapanese thathatt mostmost culturedcultured oror non-nucleatednon-nucleated keshkeshii pearls.pearls. cultureculturedd pearlpearlss produceproducedd bbyy IranIran comecome frofromm ththee islandislandss ofof KharKharkk (latitud(latitudee 29°12'N,29°12'N, longitudlongitudee 5050°10'E0 1O'E)) anandd LavaLavann (26°50'N,(26°50,N, SouthSouth SeaSea pearpearll 53°15'E)53°15'E) oorr frofromm alonalongg ththee BandaBandarr LengehLengeh WeWe werweree recentlyrecently askedasked ttoo determindeterminee thethe coasts.coasts. ThThee smalsmalll quantitquantityy ofof cultureculturedd andand naturenature ofof a SouthSouth SeaSea pearpearll pendanpendantt thathatt hadhad non-nucleatednon-nucleated culturedcultured pearlpearlss fromfrom thesethese beebeenn purchasepurchasedd iinn HongHong KongKong (it(it waswas sourcessources araree usuallusuallyy suppliedsupplied ttoo ththee locallocal accompaniedaccompanied bbyy a 'sales'sales certificatecertificate')7).. WeWe jewellerjewelleryy tradetrade.. TheThe pearlpearl farmfarm atat KishKish explainedexplained thathatt thethe tertermm 'Sout'Southh SeaSea pearl'' Island,Island, reportereportedd bbyy AndersonAnderson (Webster,(Webster, usuallyusually refersrefers toto culturedcultured pearlpearlss andand thethe 19831983 pp.. 525)525) isis apparentlyapparently nono longerlonger chanceschances ofof itit beingbeing naturalnatural werewere low.low. A operational.operational. radiographradiograph (Figure 13) waswas obtainedobtained andand InIn ththee laboratory,laboratory, wwee seesee fairlyfairly largelarge provedproved surprisingsurprising inin thatthat itit diddid notnot showshow a quantitiesquantities ofof marinemarine non-nucleatednon-nucleated shellshell beadbead nucleusnucleus asas expected,expected, butbut ratherrather a culturedcultured pearlspearls mixedmixed withwith naturalnatural cavitycavity containingcontaining anan innerinner 'solid'solid body'body' thatthat pearls.pearls. UpUp untiluntil ourour discussionsdiscussions withwith thethe inin turnturn hadhad a smallsmall cavity.cavity. InIn normalnormal BandarBandar LengehLengeh FisheriesFisheries Company,Company, thethe circumstances, wewe wouldwould askask thethe customercustomer toto thoughtthought thatthat IranIran couldcould bebe thethe sourcesource ofof a unsetunset thisthis particularparticular pearlpearl forfor furtherfurther majoritymajority ofof thesethese wawass naturallnaturallyy inin ourour radiography,radiography, soso thatthat wewe couldcould builbuildd uupp a minds.minds. However,However, nownow ourour informationinformation isis three-dimensionalthree-dimensional imageimage ofof thethe internalinternal thatthat mostmost ofof thethe non-nucleatednon-nucleated culturedcultured structure,structure, inin orderorder toto comecome toto a positivepositive pearlspearls wewe seesee appearappear toto originateoriginate fromfrom result. Unfortunately,Unfortunately, thethe customercustomer waswas onon a JapanJapan asas anan accidentalaccidental by-productby-product ofof thethe stop-overstop-over inin BahrainBahrain andand hadhad toto boardboard a traditionaltraditional culturingculturing process,process, i.e.i.e. 'keshi''keshi' oror flight thethe samesame day,day, soso wewe hadhad onlyonly a shortshort 'keshi-like''keshi-like' pearls.pearls. LargeLarge quantitiesquantities ofof timetime inin whichwhich toto examineexamine it.it. Therefore,Therefore, a

J. Gemm., 1998, 26,26,1,17-23 1. 17-23 clearclear ideideaa ooff ththee structurestructure coulcouldd nonott beb e AcknowledgementAcknowledgementss determined.determined. HoweverHowever,, ththee internainternall anandd TheThe authorauthorss wiswishh ttoo thanthankk MMrr K.K. ScarrattScarratt externaexternall appearanceappearance ofof ththee pearpearll suggestesuggestedd iitt forfor discussiondiscussionss oonn areaareass ofof ththee textextt duringduring thethe wawass mormoree likellikelyy ttoo bbee ooff 'cultured'cultured'' originorigin compilatiocompilationn ofof thesthesee notesnotes.. thathann naturanaturall anandd ththee pricpricee paipaidd forfor iitt waswas consistent with this conclusion. How this consistent with this conclusion. How this ReferenceReferencess pearpearll formedformed iiss unclearunclear.. IfIf 'cultured','cultured', aass Scarratt,Scarratt, K.K., , 1992.1992 . NoteNotess fromfrom ththee LaboratorLaboratoryy - 1616.. expectedexpected,, wawass ititss formationformation accidentaaccidentall oorr JJ.. Gemm., 2323,, 44,, 215-24215-24 intentionalintentional?? IfIf ththee 'nucleus''nucleus' wawass placedplaced BubshaitBubshait,, A.A.,, Sturman,Sturman, N.P.G.N.P.G.,, 1993.1993. NoteNotess fromfrom ththee GeGemm withiwithinn aann oysteoysterr onon purpospurposee ttoo forformm ththee & PearlPearl TestingTesting LaboratoryLaboratory,, BahraiBahrainn - 2.2. J.J. Gemm., 2323,, 7,398-4017, 398-401 largerlarger pearlpearl,, ththee correctcorrect nomenclaturnomenclaturee wouldwould BubshaitBubshait,, A.A.,, Sturman,Sturman, N.P.G.N.P.G.,, 1994.1994. NoteNotess fromfrom ththee GeGemm bbee a cultureculturedd pearlpearl;; if,if, howeverhowever,, ththee 'nucleus''nucleus' & PearlPearl TestingTesting Laboratory,Laboratory, BahrainBahrain - 3,3, J.J . Gemm., 2424,, and resulting pearl were a result of 1,42-41, 42-4 and resulting pearl were a result of HurwitHurwit,, K.K.,, 1989.1989. GeGemm TradTradee LaLabb NotesNotes.. Gems & Gemology, accidentaaccidentall growtgrowthh frofromm a piecpiecee ooff mantlemantle 2525,3,174, 3, 174 placeplacedd withiwithinn aann oyster,oyster, ththee tertermm 'non'non­- HurwitHurwit,, K.K.,, 1991.1991. GeGemm TradTradee LaLabb NotesNotes.. Gems & Gemology, 2727,2,, 2, 110-11110-11 nucleatenucleatedd cultureculturedd pearlpearl'' woulwouldd bbee moremore KennedyKennedy,, S.J.S.J.,, AkamatsuAkamatsu,, S.,S., IwahashiIwahashi,, Y.Y.,, 1994.1994. ThThee HopeHope appropriate.appropriate:' PearlPearl.. JJ.. Gemm., 2424,, 44,, 235-9235-9

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Notes fromfrom the Gem andand Pearl TestingTesting Laboratory Bahrain -- 6 Spinel and garnet star networks: an interesting asterism in gems from Sri Lanka

SpinelW.L.D.R.A. and garnetKumaratilake, star networks: FGA an inieresting asterism in Gem Unit, Sri Lankil Customs, Colombo, Sri Lankil eems from Sri Lanka W.L.D.R.A. Kumaratilake, FGA Gem Unit, Sri Lanka Customs, Colombo, Sri Lanka ABSTRACT: Four-rayFour-ray andand six-raysix-ray starstar networksnetworks araree reportereportedd iinn spinelspinel andand garnetgarnet frofromm SriSri Lanka.Lanka. DetailsDetails ooff theitheirr arrangementarrangement andand orientationsorientations areare discussed.discussed.

Keywords: networksnetworks,, groups,groups, loopsloops,, octahedral,octahedral, rhombicrhombic dodecahedrondodecahedron

IntroductionIntroduction several groups are oriented in different direc­directions tions andand cancan intersecintersectt ttoo forformm a wewebb oror a orneome SriSri LankaLankann spinelsspinels andand garnetsgarnets networknetwork.. ItIt isis apparenapparentt thathatt ththee starstar contentscontents exhibitexhibit starstar patternpatternss comprisincomprisingg four-rayfour-ray (ignoring(ignoring ththee starstar typetype)) ooff ththee 3 networknetwork and six-rayand six-ray stars combined stars combined in spectacular in spectac- 24 174 configurationconfigurationss areare determineddetermined bbyy thethe ular designsdesigns whicwhichh wilwilll bbee describedescribedd andand efficiency ofof aa looploop whichwhich isis defineddefined by: referrereferredd ttoo aass networks. Complete Complet enetworks network scan can . . NumbeNumberr ooff starsstars inin ththee networknetwork 24 bbee seenseen inin eggeggss cutcut fromfrom thesethese stonesstones (Figures 1 1 Loop efficiencyeffiCIency -= and 2). WhileWhile spinelspinel cancan showshow onlonlyy oneone NumbeNumberr ooff looploopss inin ththee networknetwork networnetworkk configuratioconfigurationn consistinconsistingg ooff four-rayfour-ray anandd six-raysix-ray stars,stars, garnegarnett may displadisplayy ononee SpinelSpinel consistinconsistingg onlyonly ofof four-rafour-rayy starsstars oror anotheranother Four-ray and six-ray network (Figure 1). with both four-ray and six-ray stars.stars. A spinelspinel octahedraloctahedral crystalcrystal hashas sixsix groupsgroups NumerouNumerouss lonlongg oror short,short, slenderslender andand whicwhichh orientorient paralleparallell ttoo thethe [110],[110], [110],[lTO], [101][101],, paralleparallell crystalcrystal inclusioninclusionss araree responsibleresponsible forfor [101],[10T], [011][Oil] andand [OIl][OlT] directiondirectionss (i.e.(i.e. aatt 90°90° ttoo thethe opticaloptical starstar effectseffects andand networknetwork thethe virtualvirtual rhombirhombicc dodecahedradodecahedrall crystalcrystal formationsformations.. SeveralSeveral suchsuch inclusioninclusion groupsgroups faces). They generate sixsix loopsloops whichwhich intersect inter­ (which(which mamayy bbee simplysimply calledcalled groups), orientorient sect anandd formform a networknetwork ooff eighteight six-raysix-ray starsstars themselvethemselvess alonalongg severalseveral directiondirectionss iinn thethe andand sixsix four-rafour-rayy stars.stars. TheThe formeformerr isis locatedlocated hosthost crystal.crystal. IInn spinelspinel thetheyy consisconsistt ooff eithereither aatt ththee centrcentree ooff evereveryy (111(111)) facfacee anandd ththee latterlatter rutilerutile (needle-like)(needle-like) (Figure 3a), sillimanitesillimanite aatt everyevery edgedgee poinpointt wherwheree foufourr crystalcrystal facesfaces (blade-like(blade-like)) (Figure 3b) 3b) or o diffuser diffus emicroscopic microscopi c meet.meet. TheThe looloopp efficiencyefficiency = 14/614/6 (i.e(i.e.. eacheach whitewhite granulegranuless whichwhich loolookk milkmilkyy andand looploop contributescontributes ttoo forformm 2%2!/3 four-rayfour-ray andand six­six- resembleresemble a solution,solution, whereawhereass iinn garnegarnett therethere ray stars). areare onlonlyy rutilerutile needlesneedles (Figure 4). 4). UpoUponn reflectionreflection ooff light fromfrom a groupgroup,, a GarnetGarnet chatoyantchatoyant banbandd formformss arounaroundd it,it, iinn a planplanee atat 90°90° toto thethe lengthlength ooff inclusionsinclusions,, anandd developsdevelops Four-ray network (Figure 2a). anan opticaloptical looploop,, inin thithiss papepaperr describedescribedd andand A rhombirhombicc dodecahedradodecahedrall garnegarnett crystacrystall referrereferredd ttoo asas a loop. Loops Loops so so generated generated from from possessepossessess fourfour groupsgroups orienteorientedd paralleparallell ttoo thethe

© GemmologicalGemmological AssociationAssociation andand GemGem TestingTesting LaboratoryLaboratory ofof GreatGreat BritainBritain ISSNISSN:: 1355-45651355-4565 Inside the octahedral star Spinel crystal: directions of corresponding star network 6 inclusion sets 6 loops configuration

[1IoJ

Star network environment 01 a

loop -l-rav star o-rav star

/6J<6\ (6 (\ )) (6 4) 6L-..16 (6x6)6) (4 6) 25 (4)= 4-ray star. (6)= 6-ray star. * Figure 1: Details of spinel four-ray and six-raystar network.

[1Il], [III], [111] and [111] directions (i.e. at crystal with directions [111], [Ill], [111] and 90° to virtual octahedral crystal faces). These [111]. Altogether they are responsible for 10 develop four loops, which intersect and loops and thus could be labelled as six create a network of twelve four-ray stars, at a octahedral loops and four rhombic dodecahedral rate of a star in the centre of every crystal loops. Octahedral loops are invariably weak face. The loop efficiency = 12/4 (=3), and, in intensity. Both kinds of loops may therefore, this kind of garnet network is more combine and create a network with thirty efficient than spinel loops but makes only four-ray stars and twenty six-ray stars, four-ray stars. making a total of 50 stars. The loop efficiency is 50/10 (=5) and although there are stars Four-ray andsix-ray network (Figure Zb). weak in intensity, these loops are the most efficient of the three networks discussed. A rhombic dodecahedral garnet crystal has 10 groups which fall into two classes of The correlation between octahedral and directions. One originates from a virtual rhombic dodecahedral loops can be seen in octahedral crystal which coincides with the the diagram given in Figure 5. host crystal, with directions [110], [l10], Box (b): A four-ray star results from an [101], [lOT], [011] and [011] - as in the octahedral loop and a rhombic dodecahedral example of spinel above, and the other loop. There are 24 stars in total; each located originates from the actual dodecahedral on every corner where two dodecahedral

Spinel andgarnet starnetworks: an interesting asterism in gemsfrom Sri Lanka ill'l,l, th, ,11<,mhc ,j,'ck"li1ni'd! .... t,lI l ,l'I'ti ,'1<,1\

\..il!l\tlill .... 1. 11 I.l~l)I."""r\l)I1,II!i': \1l't\\\\1" \nll!I'''':UI,111\' :-'-ll'lIt', I""p, ,)11 .... t," l "lI11C'il':-'.::

_ =4 loops (a) = 4 loops

[111]

(b) ,22222 2 , 2 2 =6 6 octahedral loopsloops [101] rjllj "•-• = 4 rhombic dodecahedral loops loops '[Oil]

2626

[101]

Figure 2: Details of two garnet star networks.

Figure 3(a): Six-ray star isolated fromfrom the Figure 3(b): Corresponding 'blade-like'blade-like'' silli­silli- spinel star network. manite inclusion groups.

}1.. Gemm.,Gemm ., 1998,1998, 26,1,26, 1 , 24-28 Figure 4(a): Four-ray star isolated fromfrom the Figure 4(b): Corresponding 'needle-like''needle-like rutile garnet four-rayfour-ray star network.network. inclusion groups. Figure 5: Anatomy of garnet four-ray and six-ray star network.network.

2727 Octahedral loops

I:l.'" 2 3 Represent virtual ....uo 0 .o- octahedral crystal. OIUS- 0 4-ray Stars are independent ..t::'"' ~'"g (6) @ from rhombic ..t:: dodecahedral loops, IU ...u and are weaker 4-ray in intensity 0 ® ® '" 1 (24) '" st r type @ ( o. of tars 2 6-ray (12) CD CD @

Correlation between octahedral and rhombic dodecahedral loops Iin the star network Represent actual rhombic dodecahedraRepresent actuall crystal rhombic. Each stadodecahedralr is affected crystal.by a singl Eache octhedrastar is affectedl loop by, a whicsingleh weakeocthedralr in intensitloop,y which is weaker in intensity

Spinel and garnet star networks: an interesting asterism in gems fromfrom Sri Lanka crystalcrystal facesfaces meet.meet. AsAs thethe octahedraloctahedral looploop iiss Boxes (a),(e),(!),(h)(a),(e),(f),(h) and (0:(i): TheseThese looploop weakerweaker inin intensityintensity comparedcompared toto thethe otherother combinationscombinations areare notnot validvalid forfor thethe network.network. rhombicrhombic dodecahedraldodecahedral looploop ofof thethe four-rayfour-ray Boxes (b) (b) and and (c): (c): Represent Represen ant a actualn actua rhombicl rhombi c star,star, rarelyrarely stonesstones havehave beenbeen cut toto isolateisolate thethe dodecahedraldodecahedral crystal,crystal, wherewhere eacheach starstar inin thethe strongerstronger loop;loop; thethe resultingresulting stonestone mamayy networknetwork isis affectedaffected bbyy a singlesingle octahedraloctahedral resembleresemble a cat's-eyecat's-eye andand therebythereby bbee loop.loop. potentiallpotentiallyy deceptive.deceptive. Boxes (d) and (g): RepresentRepresent anan unaffectedunaffected Box (c): A six-raysix-ray starstar resultsresults fromfrom aann virtualvirtual octahedraloctahedral crystaLcrystal. octahedraloctahedral looploop andand twotwo rhombicrhombic dodecahedradodecahedrall loops;loops; againagain thethe weakerweaker ConclusionConclusion octahedraloctahedral looploop isis immediatelyimmediately noticeable.noticeable. ThereThere areare 1212 starsstars inin total,total, eacheach locatedlocated atat thethe TheThe directionsdirections ofof thethe inclusionsinclusions andand theirtheir centrecentre ofof everyevery rhombicrhombic dodecahedraldodecahedral crystalcrystal contextscontexts areare ththee mostmost importantimportant featuresfeatures iinn face.face. formationformation ofof thethe networks.networks. First,First, theythey shouldshould bbee paralleparallell witwithh referencereference toto eacheach otherother ttoo Box (d): A four-rayfour-ray starstar isis formedformed solelysolely formform a groupgroup and,and, secondly,secondly, severalseveral suchsuch byby twotwo weakweak octahedraloctahedral loops.loops. ThereThere araree groupsgroups orientorient themselvesthemselves alongalong specificspecific sixsix starsstars inin totaltotal andand eacheach isis locatedlocated oonn directionsdirections relatedrelated toto thethe crystallographiccrystallographic everyevery edgeedge pointpoint wherewhere fourfour rhombicrhombic orientationorientation ofof thethe hosthost stone.stone. dodecahedraldodecahedral crystalcrystal facesfaces meet.meet. Box (g):(g): A A six-ray six-ray star sta ris i sthe the outcome outcome of o fthree three AcknowledgementsAcknowledgements weakweak octahedraloctahedral loops.loops. ThereThere areare eighteight weakweak stars,stars, eacheach locatedlocated onon everyevery edgeedge pointpoint wherewhere ManyMany thanksthanks toto MrMr T.G.N.R.T.G.N.R. MalindaMalinda foforr threethree rhombirhombicc dodecahedraldodecahedral crystalcrystal facesfaces finefine photographsphotographs,, andand MrMr R.R. SamaranayakeSamaranayake 2828 meet.meet. forfor micro-photographmicro-photograph ofof garnetgarnet inclusions.inclusions.

c ------,.------•

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J.J.Gemtn., Gemm .• 1998.1998,26,1,24-28 26. 1. 24-28 Colour in topazes from rhyolite domes of the San Luis Potosi volcanic field, Mexico

Sarah Dewonck1, Jacques L. Leroy1 and Y. Dusausoy2 1. Universite Henri Poincare-Nancyl, UMR G2R (EP 578) BP 239,54506 Vandoeuvre-les-Nancy cedex, France 2. Universite Henri Poincare-Nancyl, laboratoire LCM3B BP 239,54506 Vandoeuvre-les-Nancy cedex, France

ABSTRACT: In the San Luis Potosi volcanic field (Mexico), both colourless and amber-coloured topazes (up to 4 cm) have crystallized in voids and fractures of the Cerro El Gato lava dome, near the village of Tepetate. They are well crystallized and the largest crystals are cut and marketed. In the neighbouring Cerro El Lobo lava dome, the topazes are very small (less than 5 mm) and slightly yellow tinted. Comparing these different crystals with respect to their growth environments in the field, habits, chemical compositions and EPR characteristics enable an explanation of the crystallization conditions and the amber colour to be given. The zonal distribution of the crystals in the deposits according to their colour can be used as a guide-line for prospecting. 29

Introduction Jequitinhonha river basin (Minas Gerais opaz is an aluminium fluorosilicate, State, Brazil), in Mexico on the eastern side of the Sierra Madre Occidental, from America Al2Si04F2_x(0H)x, that frequently Toccurs as accessory minerals in in the Durango State to the north to Apulco fluorine-rich rhyolites, pegmatites, greisens (Hidalgo State) to the south. Clear and and hydrothermal veins. Deposits are known transparent crystals exist, but the most and mined in many places in the world economically interesting ones (the gems) are (Hoover, 1992), such as in the Volyn region usually yellow, brown, blue, pink or violet. (Ukraine) and along the east side of the Ural Most studies on topaz are focused on the Mountains, between Verkhoturye in the crystallographic (Zemann et ah, 1979; Parise north and the Sanarka deposits, 400 km et ah, 1980), physical (Aines and Rossman, towards the south; along the eastern coast of 1986; Londos et al, 1992; Petrov, 1977; Ribbe Australia (Mount Surprise in Queensland is and Gibbs, 1971), optical (Ribbe and the largest topaz-producing area in Rosenberg, 1971), thermodynamic (Barton, Australia), in the western United States 1982) and chemical (Akizuki et al, 1979; rhyolite belt (Thomas Range, Spor Mountain, Ribbe, 1982; Hervig et al, 1987) properties Wah Wah Mountains in Utah, for example), with the purpose of identifying the colour in the Ouro Preto district and in the origin (transition metals or colour centres)

© Gemmological Association and Gem Testing Laboratory of Great Britain ISSN: 1355-4565 SpectrometrSpectrometryy (ICP-MS),(ICP-MS), anandd ElectronElectron ParamagnetiParamagneticc ResonancResonancee (EPR)(EPR) (Dewonck,(Dewonck, 1996).1996).

FeatureFeaturess ofof MexicaMexicann topaztopaz Topaz-bearinTopaz-bearingg rhyoliterhyolitess araree commocommonn inin 22° MexicoMexico.. TheTheyy correspondcorrespond ttoo aann extensiveextensive 05' TertiaryTertiary felsifelsicc volcanivolcanicc belbeltt whicwhichh extendsextends fromfrom centracentrall MexicMexicoo ttoo westerwesternn UniteUnitedd StatesStates.. IInn MexicoMexico,, ththee depositdepositss relaterelatedd ttoo rhyolitrhyolitee areare locatelocatedd onon ththee easterneastern sideside ooff ththee SierraSierra Cerro El Gato MadrMadree Occidental,Occidental, frofromm DurangDurangoo StateState (Americ(Americaa anandd CerrCerroo dede loloss RenidiosRenidios)) toto HidalgHidalgoo StateState (Apulco)(Apulco),, bubutt mainlmainlyy inin thethe centralcentral parpartt ooff ththee belbeltt iinn SanSan LuiLuiss PotosPotosii andand t (j ~ O GuanajuatGuanajuatoo StateStatess (Forsha(Forshagg anandd FriesFries,, 19421942;; N MenziesMenzies,, 1995;1995; SinkankasSinkankas,, 1959,1959, 1976)1976).. Skm Cerro El Lobo I I CrystalsCrystals areare usuallusuallyy ratheratherr smallsmall anandd a 1010 ctct gegemm woulwouldd bbee considereconsideredd large.large. HoweverHowever,, iinn 101°15' ththee TepetateTepetate areaarea (Sa(Sann LuiLuiss PotosPotosii State)State) finefine [==:11 [==:1 2 _3[==:1 4 crystalscrystals may reacreachh 1515 cmcm inin lengthlength andand thethe largeslargestt flawlessflawless cucutt stonestone iiss reportereportedd aass oO investigatedinvestigated arcaarea weighinweighingg 2255 ctct (Sinkankas,(Sinkankas, 1976).1976). TheThe topazestopazes Figure 1: Geological map map and and location location of theof the selectedselected forfor investigatioinvestigationn havhavee beebeenn sampledsampled 3030 Cerros ElEl Gato Gato and and El El Lobo Lobo (San (San Luis Luis Potosi Potosi frofromm ththee CerrosCerros EEll GatGatoo anandd EEll LoboLobo,, whichwhich State, Mexico)Mexico) (from (from Aguillon-Robles, Aguillon-Robles, 1994). 1994). 1 - 1 -araree twtwoo rhyolitirhyoliticc domesdomes ooff ththee SanSan LuiLuiss PotosiPotosi San Miguelito rhyolite;rhyolite; 2 2- -Cantera Cantera ignimbrite; ignimbrite; volcanivolcanic c field,field, neanearr ththee villagvillagee ooff TepetateTepetate,, 3 - Panalillo rhyolite; rhyolite; 4 - 4Quaternary. - Quaternary. 4400 km southwessouthwestt ooff SanSan LuiLuiss PotosPotosii citycity (Figure 1). 1). Only Only the the topazes topaze sfrom from the the Cerro Cerro El E l andand describingdescribing thethe morphologicalmorphological diversity.diversity. GatoGato areare workedworked.. TheTheyy areare mainlmainlyy marketedmarketed TopazTopaz presentspresents variousvarious crystalcrystal habits,habits, welwelll forfor mineraminerall exhibitioexhibitionn andand salesale.. ThThee largeslargestt oorr describeddescribed byby GoldschmidtGoldschmidt (1913).(1913). OtherOther ththee best-crystallizebest-crystallizedd stonestoness areare cucutt (M(M.. Luna,Luna, paperspapers dealdeal withwith thethe petrogenesispetrogenesis ofof thethe TepetateTepetate,, perspers.. comm.)comm.).. topaz-bearingtopaz-bearing rhyolitesrhyolites (Christiansen(Christiansen et al.,a/., 1985),1985), thethe geologicalgeological characteristicscharacteristics ofof thethe GeologicalGeological environmentenvironment variousvarious topaztopaz depositsdeposits (Hoover,(Hoover, 1992),1992), originorigin (Olsen,(Olsen, 1971)1971) andand crystallizationcrystallization contextcontext ThThee topaz-bearintopaz-bearingg SanSan MiguelitMiguelitoo rhyoliterhyolite,, (Foord(Foord et a/.,al., 1988).1988). ButBut nonenone ofof thethe paperspapers witwithh anan agagee ooff 30±1.530±1.5M Maa (K-A(K-Arr method,method, combinecombine thethe resultsresults ofof thethe laboratorylaboratory Labarthe-HernandeLabarthe-Hernandezz et al,a/., 1982)1982) andand analysesanalyses withwith thethe fieldfield studiesstudies toto determinedetermine 29.2±0.829.2±0.8M Maa (K-A(K-Arr onon biotitebiotite,, Aguillon­Aguillon- thethe growthgrowth conditionsconditions ofof thethe crystals.crystals. RobleRobless et al.,a/., 1994)1994) iiss a silica-richsilica-rich,, meta-tometa-to ItIt isis thethe aimaim ofof thithiss studystudy toto investigateinvestigate thethe peraluminouperaluminouss lavlavaa witwithh a fluorfluor contentcontent morphologicalmorphological propertiesproperties (crystal(crystal habithabit andand ranginrangingg fromfrom 0.10.1 ttoo 0.350.35 wt%wt%.. SnSn mineralsminerals size)size) andand thethe colourcolour differencesdifferences ofof somesome (cassiterite)(cassiterite) areare alwayalwayss presenpresentt inin ththee lavalava topazestopazes fromfrom thethe SanSan LuisLuis PotosiPotosi volcanicvolcanic dome,dome, bubutt araree withouwithoutt economiceconomic valuevalue.. field in Mexico, usingusing bothboth thethe fieldfield observa­observations IInn ththee CerrCerroo EEll GatoGato,, ththee studiestudiedd topaz­topaz- tions andand thethe laboratorylaboratory determinationsdeterminations ooff ricrichh zonezoness areare locatedlocated iinn ththee south-easternsouth-eastern crystallography,crystallography, chemicalchemical analysesanalyses byby bordeborderr ooff ththee lavalava domdomee (Figure 1), 1), in in a a more more InductivelyInductively CoupledCoupled Plasma-AtomicPlasma-Atomic oorr leslesss anastomosedanastomosed networnetworkk ofof fracturesfractures Emission Spectrometry (ICP-AES) andand Mass anandd irregulairregularr anandd elongatedelongated voidvoidss (some(some 1100

/J.. Gemm.,Gemm.,1998,26,1,29-39 1998,26,1,29-39 Figure 2a and b: Topaz-bearing voids in rhyolites from the San Luis Potosi volcanic field,field. (a) (left) The anastomosed network of fracturesfractures and elongated cavities as exposed in the mined trenchestrenches of the Cerro El Gato deposits. This is considered as an open system for fluid circulation. Around the cavities the rhyolitic lava is greyish-white due to chemical leaching.leaching, (b) (right) The near spherical,spherical closed and isolated cavities (up to 2 cm across) of the Cerro el hoboLobo lava (the largest cavity shown is 1.5 cm across). cmcm long),long), paralleparallell ttoo ththee lavalava flow (Figure 2a). 2a). crystallizedcrystallized inin anan openopen system,system, wherewhere fluid InIn ththee investigatedinvestigated zonezone,, ththee lavalava flow iiss circulatedcirculated witwithh possiblepossible renewarenewall andand steeplysteeply dippingdipping ttoo neanearr verticalvertical,, bubutt topaztopaz chemicalchemical elementelement enrichment.enrichment. can alsoalso bebe observedobserved in in more more or orless less horizontal hori­ TheThe CerroCerro EIEl LobLoboo (Figure 1) 1) is i sa asmaller smalle r zontal lavalava flows. TheThe colourcolour ofof ththee topaztopaz lavlavaa dome,dome, characterizedcharacterized bbyy ththee presencpresencee ooff crystalscrystals (up(up toto 4 cm)cm) varievariess accordingaccording ttoo theirtheir smallsmall (less(less thathann 2200 mmmm)) spherical-shaped,spherical-shaped, locationlocation inin ththee depositdeposit.. TheyThey areare yellowyellow toto closedclosed anandd isolatedisolated cavitiescavities,, disseminateddisseminated 3131 amber-colouredamber-coloured inin thethe centralcentral parpartt ofof thethe throughoutthroughout ththee lavalava (Figure 2b). 2b). As A sat a tCerro Cerro mineralizedmineralized zone,zone, whereawhereass crystalscrystals towardstowards EEIl Gato,Gato, fluids havhavee separatedseparated fromfrom thethe lavalava thethe peripheryperiphery areare colourless,colourless, somesome withwith redred duringduring risinrisingg and/and/o orr cooling,cooling, bubutt inin contrastcontrast ttoo blackblack inclusionsinclusions ofof Fe-minerals.Fe-minerals. HematiteHematite toto thathatt localitylocality thethe fluids atat CerroCerro EEIl LobLoboo diddid lamellaelamellae areare alsoalso associatedassociated witwithh thesethese notnot coalescecoalesce andand remainedremained inin thethe lavalava asas colourlesscolourless topazes.topazes. ArounAroundd thethe mineralizedmineralized isolatedisolated bubblesbubbles.. HoweverHowever,, veryvery palpalee yellowyellow fracturesfractures,, ththee initiallyinitially greygrey rhyoliterhyolite iiss palerpaler inin topazestopazes occuroccur inin thesethese cavities,cavities, bubutt dodo notnot colour,colour, resultinresultingg fromfrom chemicalchemical leaching.leaching. exceedexceed 5 mmmm inin length.length. Their growthgrowth FroFromm thethe fieldfield observations,observations, itit cancan bebe environmentenvironment cancan bbee consideredconsidered asas a closedclosed concluded thatthat these thesetopazes havetopazes have system.system.

AnalyticaAnalyticall proceduresprocedures distinguished.distinguished. UsingUsing ththee MillerMiller indicesindices ooff all the listed pinacoids, prisms and bi­ Crystal habit all the listed pinacoids, prisms and bi- pyramids,pyramids, ththee topatopazz crystacrystall classclass (mmm)(mmm) TheThe variouvariouss habitshabits ofof thethe topatopazz crystalscrystals andand theitheirr unit-celunit-celll parametersparameters (a(a = 4.64994.6499 witwithh theirtheir crystallographiccrystallographic parametersparameters A,A, b = 8.79688.7968 A,A, cc == 8.39098.3909 A)A) (Rosenberg,(Rosenberg , havehave beenbeen determineddetermined usingusing a two-circletwo-circle 1967),1967), a theoreticaltheoretical crystalcrystal modelmodel hashas beenbeen 1 opticaloptical goniometer forfor ththee millimetre­millimetre- drawndrawn forfor eacheach groupgroup (Figure 3) 3) using using the the sizedsized crystalscrystals andand a self-collimatingself-collimating computercomputer programmprogrammee SHAPESHAPE andand telescopetelescope forfor ththee centimetre-sizedcentimetre-sized onesones.. comparedcompared ttoo ththee naturanaturall crystalscrystals.. TheThe measurementsmeasurements ofof thethe angleangle betweenbetween thethe normalnormalss toto thethe crystalcrystal facesfaces allowallow indexationindexation ofof ththee crystallographicallycrystallographically Chemical characteristicscharacteristics associatedassociated formsforms bbyy theirtheir MilleMillerr indicesindices.. InIn orderorder ttoo characterizecharacterize thethe factorsfactors thatthat FouFourr morphologicalmorphological groupsgroups cancan bbee thusthus controlcontrol ththee colour,colour, 5566 chemicalchemical elementselements

Colour in topazes fromfrom rhyoliterhyolite domesdomes ofof thethe SanSan Luis PotosiPotosi volcanicvolcanic field,field, Mexico Mexico were analyzed in three crystals: an physical optic effects (Nassau, 1978). Pure were analyzed in three crystals: an physical optic effects (Nassau, 1978). Pure amber-coloured crystal and a colourless topaz is a colourless mineral. Its colour can amber-coloured crystal and a colourless topaz is a colourless mineral. Its colour can one from the Cerro El Gato and a slightly be due to the presence of trace amounts of one from the Cerro El Gato and a slightly be due to the presence of trace amounts of tinted one from the Cerro El Lobo. Eleven a transition element and/or to hole/ tinted one from the Cerro EI Lobo. Eleven a transition element and/ or to hole/ elementelementss werweree analyzeanalyzedd bbyy InductivelInductivelyy electroelectronn centrescentres,, whicwhichh areare colourcolour centrescentres Coupled Plasma-Atomic Emission and can be explained by crystal field Coupled Plasma-Atomic2 Emission and can be explained by crystal field SpectrometrSpectrometryy (ICP-AES)(ICP-AES)2(Si(Si,, AlAI,, FeFe,, MnMn,, theorytheory.. MosMostt ooff thesthesee chemicachemicall defectsdefects areare MgMg,, CaCa,, NaNa,, KK,, TiTi,, PP,, Sc)Sc),, 4433 bbyy InductivelyInductively paramagnetiparamagneticc duduee ttoo ththee presencpresencee ofof oneone oror Coupled Plasma-Mass Spectrometry (ICP- several unpaired electrons. Thus they can Coupled3 Plasma-Mass Spectrometry (ICP­ several unpaired electrons. Thus they can MS)MS)3 (As (As,, BaBa,, Be,Be, Bi,Bi, Cd,Cd, Ce,Ce, Co, Co ,Cr, Cr ,Cs Cs, ,C Cuu, , bebe identifiedidentified byby their their electronic electronic paramagnetic paramag­ DyDy,, ErEr,, EuEu,, GaGa,, GdGd,, GeGe,, HfHf,, HoHo,, InIn,, LaLa,, LuLu,, netic properties.. ElectroElectronn ParamagneticParamagnetic MoMo,, NbNb,, NdNd,, NiNi,, PbPb,, PrPr,, RbRb,, SbSb,, SmSm,, SnSn,, SrSr,, ResonancResonancee (EPR(EPR)) studiestudiess (Wei(Weill et aI.,a\.f 1995)1995) TaTa,, TbTh,, ThTh,, TmTm,, UU,, VV,, W, Y,, YbYb,, Zn,Zn, Zr),Zr), LiLi wilwilll providprovidee datdataa abouaboutt ththee irradiationirradiation 4 bbyy atomiatomicc absorptionabsorption4 anandd FF bbyy defectdefectss relatedrelated ttoo mineraminerall colour.. AlthoughAlthough 5 potentiometrypotentiometry5.. OnlOnlyy ththee significansignificantt thithiss analyticaanalyticall methomethodd iiss non-destructivnon-destructivee iiff resultresultss araree givegivenn iinn TableTable 1. I. dondonee oonn aa singlsinglee crystalcrystal,, mosmostt EPEPRR spectraspectra areare obtainedobtained fromfrom powderpowder samples. samples.

EPREPR characteristicscharacteristics ThThee crystacrystall iiss placeplacedd insidinsidee ththee magnetimagneticc MosMostt mineral mineralss owowee theitheirr coloucolourr eitheeitherr ttoo fielfieldd BB (Gauss(Gauss)) ooff ththee electromagneelectromagnett whicwhichh ththee presencpresencee iinn theitheirr structurstructuree ooff transitiotransitionn splitsplitss electroelectronn spispinn sublevelsublevelss witwithh aann energyenergy metametall and/oand/ orr lanthanidlanthanidee elementelementss aass differencdifferencee g(3g~BB proportionaproportionall ttoo ththee valuvaluee ooff majomajorr oorr tractracee amountsamounts,, oorr ttoo ththee presencpresencee ththee magnetimagneticc fielfieldd (((~3 isis thethe BohrBohr magnetonmagneton ooff defectdefectss iinn theitheirr latticlatticee (Dusauso(Dusausoyy anandd equaequall ttoo 9.27314.109.27314.10-2-211 ererg g G-11 anandd g isis a non­non- WeilWeiI,, 19941994)) formeformedd bbyy naturanaturall irradiationirradiation.. dimensionedimensionedd factofactorr characteristicharacteristicc ooff ththee 3232 ColouColourr cacann bbee explaineexplainedd iinn aa numbenumberr ooff paramagnetiparamagneticc defect)defect).. FoForr instanceinstance,, iinn ththee waywayss anandd thesthesee havhavee beebeenn classifieclassifiedd intintoo cascasee ooff ononee unpaireunpairedd electronelectron,, thertheree iiss a foufourr distincdistinctt groupsgroups:: crystacrystall fieldfield,, smalsmalll bubutt essentiaessentiall differencdifferencee givegivenn bbyy ththee moleculamolecularr orbitalorbital,, banbandd theorietheoriess oorr BoltzmanBoltzmannn distributiodistributionn iinn ththee electronielectronicc spispinn

/(001(001)) ^(021)

ii) Mi / (HI) \ /A 1 \ i Y (120) 1 i 1 (010) • 1 \ 1 • 1 \ Y (no) i (120) i dio) i 1

1 i i I

J.J. Gemm.,Gemm., 19981998,26,1,29-39, 26, 1, 29- 39 ^(001) /^^"T*™\ /(112)/(112)\ /«- — •*--•» * - -1 \ (101)/^Y4A—I \ (021) //'^T- 1 - J '• \ \ /' m /(ill); >\f\

(120) (110) (no) i \ • \ (120) I |

(001) ^(011(011)) (101) £^~r~r

(021) ^ an) \ \^ (lll)J-J-V th "A* M (110) (no) j 3333 (120)(120) (120) I

(120)

Figurefigure 3: Natural topaz crystals from the San Luis Potosi volcanic area and the theoreticaltheoretical habits of topaz crystals derived from computer calculations (produced by the computer programme SHAPE). The crystal morphology of the types is defined in Table I. a :: type 1 (23 x 9 mm, 11.35 ct). b :: type 2 (22 x 11 mm, 12.85 ct). c : typetype 33(7 (7 x 10 mm, 3.5 ct). d :: type 4 (5.5 x 4 mm, 0.6 ct).ct).

Colour inin topazes fromfrom rhyolite domes of thethe San Luis Potosi volcanic field,field, MexicoMexico Table 1.I. Presence of the various forms in the four types of topaz crystals in the San Luis Potosi rhyolites.rhyolites.

locality10calihJ Cerroro ElEI GatoGato CerroCerro ElEI LoboLobo typetyp e 11 22 33 4 colourcolour amberamber andand colourless colourless amberamber colourlesscolourless yellowyellow tintedtinted sizesize cmem cmcm cmcm mm crystalcrystal form form {110(1101} ++ ++ ++ + {120{1201} ++ ++ ++ + {00110011} ++ ++ ++ + {01010101} ++ +

{11111111} ++ ++ ++ +

{112(1121} ++ +

{11311131} ++ {22112211} +

{02110211} ++ ++ ++ ++

{01110111} ++ ++

{10111011} ++ ++ ++

populations of the ground and excited the g factor defines the change in the populations of the ground and excited thepositio g factorn of thdefinese absorptio the changen line inin thethe 34 levels. A second magnetic field B1 34 levels.(frequenc Ay vsecond and energ magneticy hv, witfieldh h thBIe positspectruionm ofdependin the absorptiong on thlinee featurein thes (frequencyPlanck constan v andt equa energyl to 6.62554.10" hv, with2 7 herg.s the) spectrumparticular tdependingo the state ofon th e theparamagneti featuresc Planckis used constant to stimulat equale totransition 6.62554.10s -betwee27 erg.sn) partielectrocunlar i nto th thee studiestate odf thedefect paramagnetic. But many isadjacen usedt toenerg stimulatey levels transitions. If the sampl betwee enis enuclelectroni o fin paramagnetithe studied cdefect. ions oButr ligandmanys nuclei of paramagnetic ions or ligands adjacentplaced in energysuch a magnetilevels. cIf fielthed Bsamplev applie isd have a magnetic nuclear spin. In this case, placedperpendicularl in such ya magneticto field field B, B]Iinsid appliede a havif the ea magneticelectronic nuclearmagneti spin.c spi Inn thisis i ncase th,e perpendicularlyresonance cavity, itto come fields int oB resonanc, insidee (ra) ifneighbourhoo the electronicd o fmagnetic a nuclea r spinmagneti is inc spinthe , resonancewhen the magneticavity, itc comesfield magnitud into resonancee B or th(r)e neighbourhoodan interaction wilof al nuclearproduc emagnetic an additona spin, l an interaction will produce an additonal whenfrequenc they magnetic v has beefieldn magnitudeadjusted Bso or tha thet weak splitting of the electron's spin levels. weak splitting of the electron's spin levels. frequencyhvr = g|3B r. v has been adjusted so that It will be expressed as new absorption hvr = g~Br ' Itline wills in bethe exEPpressedR spectru asm newcalle dabsorption hyperfine In practice, adjusting v is more difficult lines in the EPR spectrum called hyperfine In practice, adjusting v is more difficult structure (HFS) if electronic and nuclear than varying B. An EPR spectrometer structurespins belon (HFS)g to thif e electronicsame atom and, an dnuclear called thanoperate varyings at constan B. Ant frequenc EPR yspectrometer v produced spins belong to the same atom, and called operates at constant frequency v produced superhyperfine structure (SHFS) if the by a microwave source, i.e. an electron superhyperfine structure (SHFS) if the by a microwave source, i.e. an electron nuclear spin is located on the ligands tube (Klystron) yielding a strictly nuclear spin is located on the ligands tube (Klystron) yielding a strictly surrounding the paramagnetic centre. monochromatic emission, but at variable surrounding the paramagnetic centre. monochromatic emission, but at variable SHFS is of prime importance in locating magnetic field B produced by the SHFS is of prime importance in locating magnetic field B produced by the the electronic paramagnetic centre in the electromagnet with two different thecrystallographi electronic paramagneticc structure. Fo centrr instancee in the, in electromagnet with two different crystallographic structure. For instance, in configurationconfigurationss : X-bandX-band atat v=9.5v=9.5 GHzGHz topaz, the HSFS of the electron paramagnetic 9 topaz, the HSFS of the electron para­ (9.510(9.5 109 herzherz)) withwith B fromfrom zerozero toto 88,00,0000 centre Fe3+ allows the conclusion magnetic centre Fe3+ allows the conclusion GausGausss oror Q-bandQ-band atat v=35v=35 GHz aanndd B fromfrom that iron is linked to fluoride atoms with a zero to 20,000 Gauss. that iron is linked to fluoride atoms with a zero to 20,000 Gauss. nuclearnuclear spin.spin. ThusThus ironiron substitusubstitutetess forfor anan InIn ththee simpsimpleslestt case,case, thethe resultingresulting aluminiumaluminium atomatom toto formform anan octahedronoctahedron absorption curve shows a single line and Fe04F2 and occupies a Wyckoff position 8d absorption curve shows a single line and Fe04F2 and occupies a Wyckoff position 8d

J./. Gemm., 1998, 26,26,1, 1, 29-3929-39 ofof loca locall symmetrsymmetryy poin pointt 11 i nin ththee spacspacee 11 manufacturemanufacturded b byy N.VN.V.. nederlandschnederlandschee grougroupp Pbn Pbnmm (n°6 (n0262 Internationa Internationall Table Tabless fo forr InstrumenteInstrumentenn compagniecompagnie, , VenloVenlo, , X-RaX-Ryay Crystallography) Crystallography).. HollanHollandd 2 JY70 type 2, manufactured by Jobin ThThee EP EPRR stud studyy wa wass performe performedd o onn th thee 2 JY70 type 2, manufactured by Jobin YvoYvonn crystalcrystalss thathatt werweree chemicallchemically y analysedanalysed;; 3 model Elan 2000, manufactured by eitheeitherr singl singlee crystal crystalss (2(2 mm mm)) oorr powder powderss 3 model Elan 2000, manufactured by (6(600 mg mg)) whos whosee grain-siz grain-sizee distributio distributionn i sis i nin PerkiPerkinn Elme Elmerr ththe e ordeorderr ofof umpm,, usinusingg a a BruckeBruckerr 44 modemodlel Perki Perkinn Elme Elmerr 400 40000 spectrometerspectrometer6 6 operatinoperatingg aatt X-banX-bandd 55 manufacturemanufacturedd b byy Tacusse Tacussell betweebetweenn 0 0 an andd 4,00 4,0000 Gaus Gauss sa att 9 955 K K (liqui (liquidd 66 manufacturemanufacturedd bbyy BruckeBruckerr SpectrospiSpectrospinn nitrogenitrogenn temperature) temperature).. S.A.S.A.,, F-6716 F-671600 Wissembour Wissembourgg

ResultResultss thethe borderborder zonezone ooff ththee samesame mineralizedmineralized structure,structure, areare ofof typestypes 1 anandd 3.3. ThThee typetype 4 Crystal habits morphologymorphology waswas onlonlyy observedobserved iinn smallsmall InIn thethe maximumaximumm symmetrysymmetry ofof thethe topaztopaz crystalcrystalss frofromm CerrCerroo EEIl LoboLobo.. ThThee mostmost orthohombiorthohombicc system,system, MillerMiller indicesindices {h00}{hOO}', complecomplexx habithabit thuthuss appearsappears ttoo bebe {OkO}{OkO} andand {OOl}{001} describdescribee pinacoidspinacoids,, {hkO}{hkO}', characteristicharacteristicc ofof ththee smallestsmallest crystalscrystals,, thosethose {hOl}{h01} andand {OkI}{Okl }prisms prism sand and {hkl} {hkl }bi-pyramids. bi-pyramids . whicwhichh crystallizecrystallizedd iinn a closedclosed system.system. FourFour morphologicamorphologicall groupsgroups (type(typess 1 toto 4)4) areare thuthuss distinguishedistinguishedd (Figures 3a 3a to to 3d; 3d; Table Table 1). I). Chemical characteristicscharacteristics ThThee pinacoipinacoidd {OOl}{001} andand aa stronglystrongly developeddeveloped prismatiprismaticc system,system, whicwhichh alwaysalways consistsconsists ooff MajoMajorr elemenelementt contentcontentss havehave beenbeen ththee {ll0}{110} andand {l20}{120} prismsprisms,, areare observeobservedd inin determineddetermined onlyonly forfor twtwoo larglargee crystalscrystals fromfrom 3535 thethe foufourr groupsgroups.. TheThe {OlD}{010} pinacoipinacoidd iiss notnot ththee CerrCerroo EIEl GatGatoo (Table II). II). These Thes etopazes topaze s = alwayalwayss presentpresent.. ThThee groupsgroups mainlmainlyy differdiffer (averag(averagee compositiocompositionn : Si02 = 3333 wt%,wt%, frofromm eaceachh otherother iinn thethe combinatiocombinationn ooff AIP3A1203 = 57 wt%,wt%, F = 1919 wt%wt%)) presenpresentt a pyramipyramidd formsforms.. TheThe crystalcrystal habitshabits varvaryy andand normanormall compositiocompositionn foforr topatopazz associatedassociated areare representedrepresented bbyy 1 ttoo 4 bi-pyramidbi-pyramidss anandd 1 witwithh rhyoliterhyolitess (Penfiel(Penfieldd andand MinorMinor,, 1894)1894).. ttoo 3 prismsprisms.. CompositionalCompositional differencesdifferences betweebetweenn thethe amber-colouredamber-coloured andand ththee colourlesscolourless crystalcrystalss ofof ThThee morphologymorphology ooff type-type-11 topazestopazes thethe CerroCerro EEIl GatGatoo araree veryvery small.small. (Figure 3a) isis thethe simplestsimplest andand thethe pyramidapyramidall shapeshape consistconsistss onlyonly ofof thethe TheThe 4444 tractracee elementelementss mentionedmentioned aboveabove combinationcombination ofof thethe {02l}{021} prismprism andand thethe {1l1}{111} havehave beebeenn analyzedanalyzed inin thethe samesame crystalscrystals fromfrom bi-pyramidbi-pyramid.. TheThe type-type-22 topatopazz crystalscrystals CerroCerro EIEl GatGatoo andand inin a yellowishyellowish topatopazz fromfrom (Figure 3b) 3b) differ diffe rfrom from those thos eof o ftype typ e1 1by b ythe th e CerrCerroo EEIl Lobo.Lobo. OnlOnlyy ththee significantsignificant elementelement additionaddition ofof bi-pyramibi-pyramidd {1l2}{112} anandd prismprism contents,contents, i.ei.e.. thosethose higherhigher thanthan thethe ICP-MSICP-MS {l0l}{101} onon thethe pyramidapyramidall terminationtermination.. TheThe limitslimits ofof detection,detection, areare givengiven inin Table II. II. For Fo r typetype 3 habithabit (Figure 3c) 3c) is i scharacterized characterized by by a a mostmost ooff thesethese tracetrace elementselements,, asas forfor thethe majormajor combinatiocombinationn ofof {111}{111} bi-pyramibi-pyramidd andand {021{O21}} elementselements,, therethere araree nono significantsignificant differencesdifferences anandd {l0l}{101} prismsprisms.. TheThe typetype 4 morphologymorphology witwithh respectrespect toto thethe crystacrystall typestypes.. (Figure 3d) isis thethe mosmostt complexcomplex withwith a However,However, somesome elementselements seemseem toto bebe combinatiocombinationn ooff threethree prismsprisms,, {O21},{021}, {011{Oll}} significantsignificant iinn eacheach ofof ththee threethree crystals.crystals. TheThe andand {l01},{101}, anandd foufourr bi-pyramidbi-pyramidss {221},{221}, {1ll},{111}, amber-colouredamber-coloured topazetopazess araree richerricher iinn volatilevolatile {1l2}{112} andand {113}.{113} . elementelementss suchsuch aass AAss andand Sb,Sb, thanthan thethe TheThe amber-coloureamber-colouredd topazetopazess fromfrom thethe colourlescolourlesss ones.ones. Conversely,Conversely, ththee lattelatterr areare CerroCerro EEIl GatoGato araree characterizecharacterizedd bbyy thethe richerricher inin LiLi,, NbNb,, TaTa,, ZrZr anandd inin metallicmetallic presencpresencee ooff ththee typtypee 1 anandd typtypee 2 habitshabits,, elementselements,, suchsuch asas CrCr,, NNii anandd ZnZn.. TheThe smallsmall whereaswhereas ththee colourlesscolourless topazestopazes,, locatedlocated iinn topatopazz crystalcrystalss sampledsampled iinn ththee vesiclevesicless ooff thethe

Colour in topazes fromfrom rhyoliterhyolite domesdomes ofof thethe SanSan LuisLuis Potosi volcanicvolcanic field,field, Mexico Mexico TableTable II.II. ChemicalChemical compositioncomposition ofof threethree representativerepresentative topazestopazes fromfrom thethe San San Luis Luis PotosiPotosi rhyolitrhyoliteses Weight Cerro El Gato Cerro El hobo Weight Cerro El Gato Cerro El Lobo % amber yellow tinted % amber cocolourlesslourless yellow tinted

Si02 33.29 33.43 — Si02 33.29 33.43 - A1203 57.71 58.10 - AIP 3 57.71 58.10 - Fe Fe2°30 t 00.0.066 0.040.04 0.040.04 P 2 3t 0.07 P20S2°5 0.060.06 0.07 -- LOlLOI 1.281.28 1.301.30 -- F 18.7718.77 19.1019.10 -- Cerro El Gato CerroCerro El El Lobo Lobo yellowyellow tintedtinted rtg/gwig amber colourlesscolourless AsAs 76.5765 4.944.94 1212..00 BaBa 0.880.88 4.184.18 1.41.4 BeBe trtr trtr 1.121.12 CrCr 0.970.97 33.2.266 0.890.89 CuCu 1.041.04 0.940.94 3.53.5 GaGa 77.6.688 99.3.344 13.613.6 GeGe 2323..8 21.21.88 21.221.2 LiLi 5959 7070 -- NNbb 4.834.83 10.0910.09 12.4512.45 NNii trtr 3.393.39 2.262.26 1 PbPb 1.011.01 1.11.1 1.271.27 1 RbRb 2.42.4 11.6.633 1.131.13 SbSb 0.290.29 00.0.033 0.220.22 Sr 00.1.188 00.1.1 9 ttrr TTaa 11.7.744 2.812.81 2.792.79 3636 V trtr 0.050.05 0.470.47 W 1.971.97 22.34.34 0.910.91 ZZnn 1.521.52 2.84 5.965.96 ZZrr 1.781.78 55.3.322 4.374.37 numbernumberss ooff ionionss oonn ththee basibasiss ooff 2244 (0,(O, OH,OH, FF)) SiSi 3.940}} 3.926}3.926} AAIl 0.0600.060}} 4.004.00 0.074}0.074} 4.004.00 All 7.992}7.992} 7.971}7.971} Fe3+ Fe3+ 0.0050.005}} 8.008.00 00.004.004}} 7.987.98 P 0.0060.006}} 0.007}0.007} LOll } 8.04 1.019} 8.12 OOHH 1.011} 8.04 1.019} 8.12 F 7.026} 7.095} F 7.026} 7.095} NotesNotes:: ThThee analyticaanalyticall resultresultss ooff variouvariouss techniquetechniquess havhavee beebeenn combinecombinedd iinn thithiss tabletable.. TotaTotall iroironn valuevaluess listelistedd aass FeFe,03t203t;; LOLO!I meanmeanss loslosss oonn ignitionignition;; ttrr meanmeanss tracetrace;; -- meanmeanss nonott determinedeterminedd

CerrCerroo EEll LobLoboo lavlavaa havhavee aann intermediateintermediate characterizcharacterizee ththee paramagnetiparamagneticc centrecentress aass compositiocompositionn foforr botbothh volatilvolatilee anandd metallimetallicc potentiapotentiall causecausess ooff coloucolourr (Thye(Thyerr et al., 1967;1967 ; elementselements;; thetheyy alsalsoo contaicontainn tracetracess ooff CuCu,, PPbb HoluHolujj anandd QuickQuick,, 19681968;; BarrBarryy anandd HolujHoluj,, anandd ZnZn.. 1973)1973).. DickinsoDickinsonn anandd MooreMoore,, 19671967,, connecteconnectedd 3+3 4+4 coloucolourr anandd paramagnetiparamagneticc centrecentress Fe +,, VV +,, 3+ Cr 3+ anandd sisixx differendifferentt coloucolourr centrecentress EPREP R characteristics characteristics correspondincorrespondingg ttoo threthreee electron-centreelectron-centress ee-~ (A,(A, AA numbenumberr ooff investigationinvestigationss oonn colourecolouredd BB,, CC)) anandd ttoo threthreee hole-centrehole-centress ee++ (X(X,, YY,, Z),, topatopazz havhavee beebeenn performeperformedd iinn ordeorderr ttoo whicwhichh disappeadisappearr witwithh ththee coloucolourr bbyy heatinheatingg

/J.. Gemm.,Gemm ., 191998,98, 26 26,1,, 1, 29- 29-3939 ttoo 500°500°C.C PetroPetrovv (1993(1993)) givegivess aa comparisocomparisonn o off amber-coloured dl/dB topaamber-colouredz (Cerro El Gato ) coloucolourr anandd paramagnetiparamagneticc centrecentress betweebetweenn 8 dildO topaz (Cerro EI Gato) hydrothermahydrothermall topazetopazess (pin(pinkk V0V(j2+2+ anandd TiTP+;3+; 3+ 2+ 3+3 orangorangee CrCr3+ anandd MnMn2+;; yelloyelloww FeFe +)) anandd Colour centres pneumatolytipneumatolyticc topazetopazess (colourles(colourlesss FeFe33++ anandd A1QJ-Alot;; browbrownn Si0SiOr3'/2 /2227A17AI ,, SiO^/Sior27 j2A\7Al anandd POJ-;bluePOf-)Pot; blue PO~-).. IInn alalll threthreee selecteselectedd topazestopazes,, ththee FeFe33++ colourless topaz spectruspectrumm consistconsistss ooff setsetss ooff SHFSHFSS mixemixedd (Cerro EI Gato) triplettripletss (140(14000 ttoo 18018000 gaussgauss)) duduee ttoo ththee couplincouplingg ooff ththee electroelectronn spispinn S ofof Fe3+ (S=5/2)(S=5/2 ) anandd ththee nucleanuclearr spispinn 1 ooff eaceachh atoatomm ooff 1919FF (1=1/2(1=1/2,, naturanaturall abundancabundancee 100%)100%).. ThThee presencpresencee ooff ononee fluoridfluoridee atoatomm iinn ththee neighbourhooneighbourhoodd ooff Fe33+ induceinducess 21+21+11 micro-indusion resonancresonancee lineslines,, i.ei.e.. a tripletriplett iinn ththee EPEPRR FeFe33++ spectruspectrumm anandd ththee presencpresencee ooff n fluoridefluoride Colour atomatomss induceinducess 2nl+ 1l lineliness mormoree oorr leslesss centre mixedmixed.. ThThee presencpresencee ooff Fe3+ iinn ththee colourlescolourlesss topatopazz indicateindicatess thathatt thithiss paramagnetiparamagneticc centrcentree yellowish topaz doedoess nonott plaplayy ananyy rolrolee iinn ththee coloucolourr ooff ththee (Cerro EI Lobo) B investigated MexicaMexicann topazestopazes.. A ververyy weaweakk bubutt broabroadd banbandd aatt 25025000 GaussGauss cancan bebe possiblypossibly 606000 12012000 18018000 24024000 30030000 360 36000 gausgausss 3 assigneassignedd ttoo twtwoo POPO~-" centrecentress aatt twotwo crystallographicallcrystallographicallyy nonequivalennonequivalentt positions.. Figure 4:4: EPREPR sspectrapectra obtain obtaineded from from powder powdereded 3737 samples at atT T = = 95 95 K ,K, 9.45 9.45 Ghz Ghz (9.5 (9.510 UP her9z herz)) with with ThThee EPR-spectruEPR-spectrumm ooff ththee amber-colouredamber-coloured the magneticmagnetic fieldfield B B rangingranging from from 0 0to to4000 4000 topatopazz (Figur(Figuree 4a 4a)) exhibits exhibit s severalsevera l linesline s thattha t gauss. ThThee s pspectraectra correspond correspond to the to derivati the derivativeve of of araree relaterelatedd ttoo colour-centrecolour-centress (3200(3200 ttoo 36036000 the intensityintensity as as a a function function of ofth ethe magnetic magnetic field field B. B. gauss)gauss).. TheThe firstfirst well-developedwell-developed lineline (a) amber-coloured amber-coloured topaz; topaz; (b) c(b)olourless colourless topaz; topaz;(c) (c) (g(g = 2.01)2.01) iiss related ttoo X hole-centrehole-centre oror ttoo yellowishyellowish topaz topaz twtwoo SiOSi03_r /2/ 22277AAl 1 centres. TheThe secondsecond (g(g = 1.88)1.88) isis relatedrelated toto electron-centreelectron-centre A DiscussionDiscussion andand conclusionconclusion whichwhich vanishesvanishes withwith thethe colourcolour bbyy heatingheating atat 500°C.500°C. TwoTwo weakweak lineslines cancan bebe assignedassigned toto 1.1. TheThe smallsmall topatopazz crystalscrystals fromfrom thethe CerroCerro EEll ttwwo B centrescentres (g(g == 1.921.92 andand 1.94).1.94) . InIn contrastcontrast LoboLobo presentpresent thethe mostmost complexcomplex habitshabits toto thatthat ofof thethe amber-colouredamber-coloured topaztopaz thethe EPR­- (Table II,, typetype 4),4), whereaswhereas thethe largerlarger spectrumspectrum ofof thethe colourless topaztopaz doesdoes notnot crystalscrystals fromfrom thethe CerroCerro ElEl GatoGato areare lessless showshow additionaladditional lineslines thatthat cancan bebe assignedassigned tto complexcomplex (types(types 1,21,2 andand 3).3). SeveralSeveral factorsfactors colourcolour centrescentres (Figure 4b). 4b). cancan influenceinfluence thethe crystallizationcrystallization ofof a mineralmineral andand thusthus itsits habit.habit. FromFrom fieldfield TheThe slightlyslightly yellowyellow tintedtinted topaztopaz observationsobservations itit cancan bebe concludedconcluded thatthat (Figure(Figure 4c) 4c) presents, presents ,in i naddition addition to t othe th eFe Fe3+3+ relationshipsrelationships existexist betweenbetween thethe sizesize ofof thethe centre,centre, a broadbroad bandband atat 28502850 GaussGauss observedobserved crystals,crystals, theirtheir habitshabits andand theirtheir onon bothboth powderpowder andand singlesingle crystalcrystal spectraspectra,, crystallizationcrystallization environment.environment. TheThe vesiclesvesicles mostmost probablyprobably duedue toto magneticmagnetic micro­micro- wherewhere thethe typetype 4 topazestopazes crystallizedcrystallized areare inclusions.inclusions. TheThe X-holeX-hole centrecentre atat g = 22.0.011 hashas smallsmall andand consideredconsidered asas closedclosed systemssystems producedproduced thethe onlyonly wellwell defineddefined lineline inin thisthis withwith lowlow fluidfluid abundanceabundance andand nono fluidfluid spectrumspectrum. ThusThus thethe colourcolour ofof thethe investigatedinvestigated renewal.renewal. SuchSuch conditionconditions dodo notnot permitpermit topazestopazes isis clearlyclearly relatedrelated toto thethe presencepresence ofof thethe developmentdevelopment ofof largelarge crystals.crystals. OnOn thethe colourcolour centres.centres. contrary,contrary, inin anan openopen systemsystem withwith fluidfluid

CColourolour iinn ttopazesopazes fromfrom rrhyolitehyolite d domesomes of of thethe SanSan LuisLuis PPotosiotosi vo volcaniclcanic fie field,ld, M Mexicoexico percolatiopercolationn andand renewarenewall andand mormoree spacespace amber-coloureamber-colouredd ones,ones, oorr presenpresentt iinn allall thethe (voids(voids anandd fractures)fractures),, largelargerr crystalcrystalss cacann crystalcrystalss (Fe)(Fe).. ThisThis iiss iinn googoodd agreementagreement crystallizcrystallizee andand thetheyy invariablinvariablyy havehave witwithh thethe datdataa ooff DickinsoDickinsonn anandd MooreMoore 3+ relativelrelativelyy simplesimple pyramidapyramidall terminations.terminations. (1967),(1967), whowho consideconsiderr thatthat Fe3+ playplayss nono 2.2. IInn thethe opeopenn systemsystem ooff thethe CerrCerroo EEIl GatoGato,, rolerole aass colourincolouringg agentagent,, iinn contrascontrastt ttoo witwithh a freefree circulationcirculation ooff thethe previoupreviouss studiesstudies (Lemmlei(Lemmleinn andand hydrothermahydrothermall fluids,fluids, ththee tracetrace elementelement Melankholin,Melankholin, 1951;1951; Grum-Grzhimaylo,Grum-Grzhimaylo, contentcontentss ofof ththee topazestopazes diffedifferr witwithh thethe 1953).1953). crystallizationcrystallization environmentenvironment iinn thethe 44.. ThThee EPEPRR studiesstudies clearlclearlyy indicateindicate thathatt thethe volcanivolcanicc structure.structure. VolatilVolatilee elementselements,, suchsuch colourscolours ooff thethe crystalscrystals araree causedcaused byby aass AAss andand Sb,Sb, areare enrichedenriched inin thethe amber­amber- coloucolourr centres.centres. AccordinAccordingg toto DickinsonDickinson colourecolouredd topazestopazes crystallizedcrystallized iinn ththee axisaxis ofof anandd MoorMooree (1967),(1967), thesthesee coloucolourr centrescentres areare ththee mineralizedmineralized zone,zone, whilwhilee thethe metallicmetallic onlonlyy stablestable below 500°C.500°C. WWee thereforetherefore elements,elements, sucsuchh asas CrCr,, NNii oorr ZnZn,, areare moremore mamayy concludeconclude thathatt ththee colourlesscolourless topaztopaz abundantabundant inin thethe colourlescolourlesss crystalcrystalss ooff thethe crystallizedcrystallized first,first, inin Ni-Cr-Zn-enrichedNi-Cr-Zn-enriched bordeborderr zonezone.. fluidsfluids anandd atat a temperaturetemperature aboveabove 500°C500°C,, ThesThesee differencedifferencess inin ththee tractracee elementelement whereawhereass thethe amber-colouredamber-coloured topaztopaz contentscontents reflectreflect variationsvariations iinn thethe crystallizedcrystallized mosmostt probablprobablyy later,later, inin hydrothermahydrothermall fluidfluid composition.composition. IInn thethe volatile-enrichevolatile-enrichedd fluidfluidss atat a lowerlower bordeborderr zonezone ooff thethe mineralizemineralizedd volcanicvolcanic temperaturetemperature,, belobeloww 500°C.500°C. TheThe structure,structure, ththee fluidsfluids areare stilstilll enricheenrichedd iinn crystallizatiocrystallizationn temperaturetemperature ooff thethe smallsmall thethe metallimetallicc elementelementss leacheleachedd frofromm thethe crystals,crystals, sampledsampled inin thethe vesiclesvesicles ofof thethe surroundingsurrounding rockrockss duringduring degassingdegassing andand CerroCerro EEIl LoboLobo lavalava,, coulcouldd bbee aroundaround thisthis fluidfluid circulationcirculation.. TopaTopazz wilwilll thuthuss bebe temperaturetemperature,, sincesince thetheyy contaicontainn onlonlyy oneone enricheenrichedd inin thesthesee elementselements.. Moreover,Moreover, coloucolourr centre.centre. ThThee crystallizationcrystallization 38 38 hematitehematite lamellaelamellae araree alsalsoo observedobserved iinn temperaturtemperaturee ooff ththee topatopazz isis thereforthereforee anan associationassociation withwith topatopazz inin thithiss zone.zone. importantimportant parameteparameterr controllingcontrolling thethe ConsequenConsequentt uponupon thisthis,, thethe fluidfluidss iinn ththee colourcolour ooff thethe topatopazz iinn thisthis area.area. axisaxis ofof ththee structurestructure areare impoverisheimpoverishedd iinn metallicmetallic elementselements bubutt enrichedenriched inin ththee mostmost volatilvolatilee elementselements,, AsAs andand SbSb.. AcknowledgementsAcknowledgements CrystallizatioCrystallizationn inin a closeclosedd systemsystem (Cerro(Cerro TheThe authorauthorss gratefullgratefullyy acknowledgacknowledgee thethe EEIl Lobo)Lobo) resultsresults iinn topazestopazes ooff intermediateintermediate assistancassistancee ofof ProfessorProfessorss BernardBernard LasnierLasnier andand compositiocompositionn withwith ththee presencpresencee ooff bothboth EmmanuelEmmanuel FritscFritschh (University(University ooff Nantes,Nantes, metallicmetallic anandd volatilvolatilee elements.elements. ThisThis iiss duedue FranceFrance)) anandd ththee anonymousanonymous refereereferee foforr allall toto ththee laclackk ooff opportunitopportunityy foforr spatialspatial fluidfluid theitheirr comments,comments, anandd AlfredoAlfredo Aguillon­Aguillon- differentiationdifferentiation asas inin anan opeopenn system.system. RobleRobless forfor hishis helhelpp inin ththee field.field. 33.. VariousVarious studiesstudies indicateindicate thathatt thethe colourcolour cancan bbee relatedrelated toto thethe ligandligand fielfieldd effecteffectss inin ReferenceReferencess transitiotransitionn groupgroup metametall impuritiesimpurities,, andand Aguillon-Robles,Aguillon-Robles, A.,A., 1994.1994. Estructura interna interna de delos los domos domos thathatt elementselements suchsuch aass FeFe (Nassa(Nassauu andand rioliticos del del area area de Tepetate,de Tepetate, S.L.P. S.L.P.Univ. Auton.Univ. Auton De San. D e San PrescottPrescott,, 1975;1975; Grigor'eGrigor'evv 1965),1965), NNii (Dee(Deerr LuisLuis PotosiPotosi,, InstitutoInstitute de Geologia,Geologia, folletofolleto tecnico,tecnico, 118,118, 58 pp et al.,al, 1982),1982), CCoo (Deer(Deer et al.,al, 1982),1982), CrCr 58pp Aguillon-Robles,Aguillon-Robles, A.,A., Aranda-GomezAranda-Gomez,, J.J.Jl,, andand SolorioSolorio­- (Nassau(Nassau andand Prescott,Prescott, 1975;1975; GiibelinGubelin andand MunguiaMunguia,, J.G.J.G.,, 1994.1994. GeologiaGeologia y tectonicatectonica dede unun KoivulaKoivula,, 1986)1986) andand TTii (Kievlenko(Kievlenko,, 19821982)) conjuntoconjunto de domodomoss rioliticosrioliticos dedell oligocenoligocenoo mediomedio enen cacann bbee ththee causcausee ooff coloucolourr iinn gemstones.gemstones. elel sursur dedell estadestadoo de SanSan LuiLuiss PotosiPotosi,, Mexico.Mexico. Revista BuButt inin thethe investigateinvestigatedd topazestopazes ooff thethe SanSan Mexicana de de Ciencias Ciencias Ceologicas, Geologicas, Univ. Univ Nadon.. Nacion Auton.. Auton . MexicoMexico,, 11(1),11(1), 29-429-422 LuisLuis PotosPotosii area,area, thesethese elementelementss areare eithereither AinesAines,, R.D.R.D.,, anandd Rossman,Rossman, G.R.,G.R., 1986.1986. RelationshipsRelationships nonott presenpresentt (Co,(Co, Ti)Ii),, moremore abundantabundant inin thethe betweebetweenn radiationradiation damagedamage anandd tractracee watewaterr iinn zirconzircon,, colourlesscolourless crystalcrystalss (C(Crr andand NiNi)) thathann inin quartz,quartz, anandd topaztopaz.. American Mineralogist, Mineralogist, 71, 711186--93, 1186-9 3

JJ. . Gemm.,Cemm., 1998,26,1,29-39 1998, 26, 1, 29-39 AkizukiAkizuki,, M.,M., HamparHampar,, M.S.M.s.,, andand ZussmanZussman,, J.J.,, 1979.1979. AnAn CenozoicoCenozoico dede llaa partpartee centralcentral deldel estadestadoo ddee SanSan LuisLuis explanationexplanation ofof anomalousanomalous opticaopticall propertiepropertiess ooff topaz.topaz. PotosiPotosi.. Folleto tecnico,técnico, Univ. Univ. Auton.Auton. SanSan LuisLuis Potosi,Potosi, 85,85, Mineralogical Magazine, 43,43, 237-41237-41 208pp208 pp 3+ Barry,Barry, W.R.,W.R., anandd Holuj,Holuj, F.,E, 1973.1973. ThThee ESESRR spectrumspectrum ofof Fe3+ Lemmlein,Lemmlein, G.G.,G.G., anandd Melankholin,Melankholin, N.M.N.M.,, 1951.1951. UbeUberr diedie inin Topaz.Topaz. III - ENDOENDORR ooff 1919F1.F1. Canadian JournalJournal ofof FarbeFarbe zweifarfigezweifarfigerr TopaskristalleTopaskristalle.. Tr. Inst.Inst. Krist.Krist. Akad.Akad. Physics, 5151,, 95-10195-101 Nauk. SSSR, 6,6, pppp 245--54245-54 Barton,Barton, M.D.M.D.,, 1982.1982. ThThee thermodynamicthermodynamic propertiepropertiess ooff Londos,Londos, C.A.c.A.,, Vassilikou-DovaVassilikou-Dova,, A.,A., GeorgiouGeorgiou,, G.G.,, andand topaztopaz solid solutionssolid solutions and some and petrologic some applications.petrologic applica­ Fytros,Fytros, L.,L., 1992.1992. InfraredInfrared studiesstudies ofof naturanaturall topaz.topaz. tions. American Mineralogist, 6767,, 956--74956-74 Physica status solidi A. Applied research, 133(2),133(2) , 473--9473-9 Christiansen, E.H., E.H., Sheridan, Sheridan, M.F., M.E, and andBurt, Burt, D.M., D.M., 1985. 1985. Menzies,Menzies, M.A.M.A.,, 1995.1995. ThThee mineralogymineralogy,, geologgeologyy andand ThThee geologygeology anandd geochemistrgeochemistryy ooff cenozoicenozoicc topaztopaz occurrencoccurrencee ofof topaztopaz.. Mineralogical Record, 26(1),26(1) , 5-565-56 rhyoliterhyolitess fromfrom thethe WesterWesternn UniteUnitedd States.States. GeologicalGeological NassauNassau,, K.K.,, 1978.1978. TheThe originoriginss ofof colorcolor inin minerals.minerals. SocietySociety ofof AmericaAmerica,, SpecialSpecial PaperPaper,, 205205,, 8282 pppp American Mineralogist, 63,63, 219-29219-29 Deer,Deer, W.A.W.A.,, Howie,Howie, R.A.,R.A., andand ZussmannZussmann,, J.J.,, 1982.1982. NassauNassau,, K.K.,, andand Prescott,Prescott, B.E.B.E.,, 1975.1975. BlueBlue anandd browbrownn topaztopaz Orthosilicates. 2n2ndd edition,edition, vovoIlA,l 1A, LongmansLongmans,, LondonLondon produceproducedd bbyy gammagamma irradiationirradiation.. AmericanAmerican Dewonck,Dewonck, S.,S., 1996.1996. CaracterisatioCaracterisationn etet conditionconditionss dede Mineralogist, 6060,, 705-9705-9 croissancecroissance dedess topazetopazess dede rhyolitrhyolitee aà topazetopazess SanSan LuisLuis OlsenOlsen,, D.R,D.R., 1971.1971. OrigiOriginn ofof topaztopaz depositsdeposits nearnear OuroOuro PotosPotosii (Mexique).(Mexique). Mem.Mém. DEADEA,, Univ.Univ. HenrHenrii Poincare­Poincaré- PretoPreto,, MinaMinass GeraisGerais,, Brasil.Brasil. Economic Geology, 6666,, NancNancyy 1,1, 5511 pppp 627-3627-311 Dickinson,Dickinson, A.c.,A.C., andand MooreMoore,, W.J.w.J.,, 1967.1967. ParamagneticParamagnetic PariseParise,, J.B.,J.B., CuffCuff,, C.c.,, andand Moore,Moore, F.H.EH.,, 1980.1980. A neutronneutron resonancresonancee ooff metalmetal ionsions anandd defecdefectt centrescentres iinn topaz.topaz. diffractiodiffractionn studystudy ooff topaztopaz:: evidenceevidence foforr a lowerlower Journal of Physical Chemistry, 7171(2),(2), 231-40231-40 symmetrysymmetry.. Mineralogical Magazine, 4343,, 943-4943-4 Dusausoy, Y., Y., andand Weil, Wei!, J.A., J.A., 1994. 1994. Point Point defects defects as precursorsas precur­ Penfield,Penfield, S.L.,S.L., anandd Minor,Minor, J.C.J.c.,, Jr.,Jr., 1894.1894. OnOn ththee chemicalchemical ofsors electron-hole of electron-hole centres. centres. Systematics Systematics and theories and theories compositioncomposition anandd relaterelatedd physicaphysicall propertiepropertiess ofof topaz.topaz. ofof radiatioradiationn centerscenters inin mineralsminerals.. Advanced Mineralogy,Mineralogy, American Journal of Sciences, 33(137),(137), 389-96389-96 Springer Verlag, vol 1, 180--7 Springer Verlag, vol 1, 180-7 PetrovPetrov,, L,I., 1977.1977. FarbuntersuchungeFarbuntersuchungenn aann TopasTopas.. Neues Foord, E.E., Jackson, L.L., Taggart, J.E., Crock, J.G., and Foord, E.E., Jackson, L.L., Taggart, J.E., Crock, J.G., and Jahrbuch fürfur Mineralogie - Abhandlungen, 130(3),130(3), King, T.V.V., 1988. Environment of crystallization of King, T.V.V., 1988. Environment of crystallization of 288-30288-3022 topaz as determined from crystal chemistry and topaz as determined from crystal chemistry and PetrovPetrov,, L,I., 1993.1993. ApplicatioApplicationn ooff EPREPR spectroscopspectroscopyy inin infraredinfrared spectraspectra.. GeologicalGeological SocietSocietyy ofof America,America, mineralogymineralogy,, petrologpetrologyy anandd geologygeology.. Habilitationsschrift,Habilitationsschrifi, abstractsabstracts witwithh programmeprogramme Philipps-UniversitäPhilipps-Universitatt Marburg,Marburg, 202202 pppp ForshagForshag,, W.F.W.E,, andand FriesFries,, c.,C., Jr,Jr, 1942.1942. TinTin depositsdeposits ofof thethe 39 Ribbe,Ribbe, P.H.,P.H., 1982.1982. Topaz.Topaz. inin P.HP.H.. RibbeRibbe (ed.),(ed.), Orthosilicates, 39 RepublicRepublic ofof MexicoMexico.. U.S. Geol.Geo!. Survey Bull,Bull., 935-C935-C,, 2n2ndd editionedition,, ReviewsReviews iinn MineralogyMineralogy,, 5,5, MineralogicalMineralogical 99-17699-176 SocietySociety ofof AmericaAmerica,, 215--30215-30 Goldschmidt,Goldschmidt, V.y.,, 1913.1913. Atlas der Krystallformen. CarlCarl Ribbe,Ribbe, P.H.,P.H., anandd GibbsGibbs,, G.V.G.y',, 1971.1971. TheThe crystalcrystal structurestructure ofof WinterWinter,, Heidelberg,Heidelberg, 1913-19261913-1926 topaztopaz andand ititss relatiorelationn ttoo physicaphysicall propertiesproperties.. American Grigor'ev,Grigor'ev, D.P.,D.P., 1965.1965. Ontogeny of minerals. DanieDaniell Davey,Davey, Mineralogist, 56,56, 24--3024-30 NeNeww YorkYork RibbeRibbe,, P.H.P.H.,, andand Rosenberg,Rosenberg, P.E.P.E.,, 1971.1971. OpticaOpticall andand X-rayX-ray Grum-Grzhimaylo, S.W., 1953. The colour of precious Grurn-Grzhimaylo, S.w., 1953. The colour of precious determinativdeterminativee methodmethodss foforr fluorinfluorinee inin topaztopaz.. American stones.stones. Zapiski VVsesoyuznogo sesoyuznogo MineralogicheskogoMineralogicheskogo Mineralogist, 56,56, 1812-211812-21 Obshchesta, 87,87, SerSer.. 2,2, 395--8395-8 RosenbergRosenberg,, P.E.P.E.,, 1967.1967. VariationsVariations inin ththee unit-cellunit-cell Giibelin,Gubelin, E.J.,E.J., andand Koivula,Koivula, J.,J., 1986.1986. Photoatlas of inclusions dimensionsdimensions ooff topatopazz andand theirtheir significance.significance. American in Gemstones. ABCABC,, ZurichZurich Mineralogist, 52,52, 1890-18951890-1895 Hervig,Hervig, R, R.,Kortemeier, Kortemeier, W.T., W.T., and and Burt, D.M.,D.M., 1987. 1987. Ionmicroprobe Ion­ Sinkankas,Sinkankas, J.,J., 1959.1959. Gemstones of North America. D.D. VanVan microprobeanalyses of Li andanalyses B in topaz of Lifrom and B in topaz from NostrandNostrand,, NeNeww York,York, 1,1, 676755 pppp differentdifferent environmentsenvironments.. American Mineralogist,Mineralogist, Sinkankas,Sinkankas, J.J.,, 1976.1976. Gemstones of North America. VanVan 72(3-4),392-672(3-4), 392-6 Nostrand Reinhold, New York, 2, 494 pp 3+ Nostrand Reinhold, New York, 2, 494 pp HolujHoluj,, E,E, anandd QuickQuick,, S.M.,S.M., 1968.1968. ThThee ESESRR spectrumspectrum ofof Fe3+ Thyer,Thyer, J.R,J.R., Quick,Quick, S.M.,S.M., andand HolujHoluj,, F.,E, 1967.1967. TheThe ESRESR inin TopazTopaz.. IIII - SuperhyperfineSuperhyperfine structure.structure. Canadian spectrumspectrum ofof Fe3+ iinn TopazTopaz.. I - FinFinee structurestructure.. Canadian Journal of Physics, 46,46, 1087-991087-99 Journal of Physics, 45,45, 3597-36103597-3610 HooverHoover,, D.B.D.B.,, 1992.1992. Topaz. ButterworthButterworth - Heinemann,Heinemann, Wei!,Weil, J.A.,J.A., Dusausoy,Dusausoy, Y.,Y., andand VotyakovVotyakov,, S.L.,S.L., 1995.1995. ElectronElectron OxfordOxford.. 207207 pppp ParamagnetiParamagneticc Resonance.Resonance. Advanced Mineralogy, Mineralogy, Vol Vo 2,l 2 40-55, 40-5 5 KievlenkoKievlenko,, E.,E., 1982.1982. Geologiya mestorozdeniy dragotsennykhdragotsennykh Zemann,Zemann, J.,J., ZobetzZobetz,, E.,E., HegerHeger,, G.G.,, anandd VollenkleVollenkle,, H.,H., kamney (Th(Thee geologgeologyy ofof precioupreciouss stonestoness deposits),deposits), 1979.1979. StrukturbestimmungStrukturbestimmung eineseines OH-reichenOH-reichen NedraNedra,, MoscowMoscow Topases.Topases. Osterreichische Akademia der Wissenschafien,Wissenschaften, Labarthe-HernandezLabarthe-Hernandez,, G.,G., Tristan-Gonzalez,Tristan-Gonzalez, M.,M., andand Mathematisch-Naturwissenschaftliche Klasse, 116,116, Aranda-Gomez,Aranda-Gomez, J.J.,J.J., 1982.1982. RevisioRevisionn estratigraficestratigraficaa deldel 145-7145-7

Colour in topazes fromfrom rhyoliterhyolite domesdomes ofof thethe SanSan LuisLuis Potosi volcanicvolcanic field,field, MexicoMexico Gem Tutorial Centre GemWinter/Sprin Tutorial gCentre 1998

4 February EMERALDS TODAY Winter/Spring 1998 4 February AEMERALDS valuable TODAYand concentrate d look at all aspects of emerald: natural rough and cut stonesA valuable, treated and, syntheti concentratec andd imitatiolook at nall stones aspects. of emerald: natural rough and cut Pricestones, £104 treated, + VAT synt (£122.20)hetic and -imitation includes stone. sandwich lunch 25 February RUBPriceY AN£104D SAPPHIR+ VAT (£122.20)E - THE INSID- includesE STOR sandwichY lunch 25 February ARUBY day Alookin D SAPPlflRg at allE aspect- THE sI NS ofID thesE STORYe gems : natural, treated, synthetic and imitation. PriceA day £104 looking + VAT at all (£122.20) aspects of - theseincludes gem sandwichs: natural, lunch treated, synthetic and imitation. Price £104 + VAT (£122.20) - includes sandwich lunch 11 March DIAMONDS TODAY 11 March ADIAMO valuablNDeS anTODAYd concentrate d look at all aspects of diamonds: rough and cut stones, treateA valuabled (lase ar nddrille concentrad and filled)ted look, syntheti at all caspects and imitatio of diamonds:n materials rough. and cut stones, Pricetreated £104 (laser + drilledVAT (£122.20) and filled), - includes synthetic sandwich and imitation lunch ma terials. Price £104 + VAT (£122.20) - includes sandwich lunch 25 March PRELIMINARY WORKSHOP 25 March APREUMJ day of practicaARY WORKSHOPl tuition for anyone who needs a start with instruments, stones and crystalsA day of. Lear practicaln to us tuitione the lO forx lenanyones at maximu who needsm efficienc a start ywith and instruments observe the, seffecttoness andand resultcrystals.s fro Learnm the to mai usen thegem-testin lOx lensg atinstruments maximum. efficiency and observe the effects and Priceresults £44 fro +m VATthe m (£51.70)ain gem-testing - includes ins trumsandwichents. lunch. GAGTLPrice £44 Student + VAT (£51.70)Price £32 - includes + VAT sandwich (£37.60) lun ch. GAGTL Student Price £32 + VAT (£37 .60) 1 April PHOTOGRAPHING GEMSTONES 1 April FranPHOTOGRAPHINGk Greenaway GEMSTONES, a leadin g professional photographer, will explain and demonstratFrank Greenaway,e the way s at o leadingget the bes professiot gemstonnale picturesphotographer,. Material swill are provideexplaind anandd yodeumon canst brinrateg theyou waysr ow nto stones get th.e best gemstone pictures. Materials are provided and Priceyou can to bebring confirmed your own - includes stones. sandwich lunch and materials Price to be confirmed - includes sandwich lunch and materials 40 40 Easter - A DAY TO STRING YOUR OWN BEADS Easter­ DAY TO SmI G YOUR OWN BEADS date to be LearA n to string with an expert stringer, step-by-step instruction, tips and date to be Learn to string with an expert stringer, step-by-step instruction, tips and confirmed hints on techniques. confirmed hints on techniques. Price £95 + VAT (£111.63) - includes sandwich lunch and a pack of beads and stringing Price £95 + VAT (£111.63) - includes sandwich lunch and a pack of beads and stringing material. Early booking is advised as there is limited space on this course material. Early booking is advised as there is limited space 011 this course Easter - BEAD STRINGING II Easter ­ B EA D S TRI GrNC II date to be For those who already know the rudiments of bead stringing. A day's date to be For those who already know the rudiments of bead stringing. A day's confirmed instruction from an expert stringer with lots of helpful hints and tips. confirmed instruction from an expert stringer with lots of helpful hints and tips. Price £95 + VAT (£111.63) - includes sandwich lunch and a pack of beads and stringing Price £95 + VAT (£111.63) - includes sandwich lunch and a pack of beads and stringing material. Early booking is advised as there is limited space on this course material. Early booking is advised as there is limited space 011 this course 28/29 April SYNTHETICS AND ENHANCEMENTS TODAY 28/29 April SYNTHETICS A 0 E HA CEME TS TODAY ArAree youyou awarawaree ooff th thee variouvariouss treatetreatedd anandd synthetisyntheticc materialmaterialss thathatt araree likellikelyy ttoo bbee masqueradinmasqueradingg amongsamongstt ththee stonestoness yoyouu araree buyinbuyingg anandd sellingselling?? WhetheWhetherr yoyouu araree valuingvaluing,, repairin repairingg o orr dealing dealing,, ca cann yo youu affor affordd toto mis misss thesthesee twtwoo daydayss ooff investigationinvestigation?? PricePrice £198 ++ VAT VAT (£232.65) (£232.65) - includes - includes sandwich sandwich IUll ches lunches

1188 Ma Mayy REVIEREVIWEW O OFF PRELIMINAR PRELIMI ARYY THEORTHEORYY AA dadayy fo forr Preliminar Preliminaryy student studensts t too revie revieww theitheirr theor theoryy worworkk anandd ttoo preparpreparee foforr theitheirr examinationsexaminations. .Tip Tipss o onn th thee consolidatio consolidationn an andd revisiorevisionn ooff factsfacts,, figurefiguress anandd principlesprinciples,, witwithh a a revie revieww o off examinatio examinationn technique technique. . PricePrice £44 ++ VATVAT (£51.70) (£51.70) - includes- includes a sandwich a sandwich lunch lunch.. GAGTLGAGTL StudentStlldent Price £32 £32 + +VAT VAT (£37.60) (£37.60) 18-218-200 Ma Mayy 3-DA3 -DAYY PRELIMINAR PRELIMINARYY WORKSHOWORKSHOPP ThiThiss three-da three-dayy cours coursee incorporate incorporatess a a theortheoryy reviewreview,, aann introductiointroductionn ttoo instrumentinstrumentss useusedd i nin ththee cours coursee an andd a a revie revieww ooff th thee materialmaterialss discussediscussedd iinn ththee preliminarpreliminaryy notesnotes.. PricePrice £156 ++ VAT VAT (£183.30) (£183.30) - includes - includes sandwich sandwich Ilinches. lunches. GAGTLGAGTL StudentStudent Price £111.49 £111.49 + VAT+ VAT (£131.00) (£131.00)

Forthcoming Events Gemstones and ornamental stones from Bolivia: a review

Dr Jaroslav Hyrsl1 and Alfred Petrov2 1 Kolin, Czech Republic 2 Cochabamba, Bolivia

ABSTRACT: Gem, ornamental and collectors' stones from Bolivia are described. The most economically important are ametrine, amethyst, citrine, sodalite and stromatolite. Ametrine, amethyst and citrine come from the La Gaiba mine in eastern Santa Cruz department. The sodalite deposit of Cerro Sapo in Cochabamba department has been mined probably for almost three thousand years. Gem-quality beryl, cassiterite, phosphophyllite and vivianite are also briefly discussed.

Keywords: Bolivia, gemstones, ametrine, amethyst, sodalite, stromatolite

Introduction

olivia, in the centre of South America, 1 - Corocoro 2 - Turco is famous mainly for its vast deposits 3 - Viloco 41 4 - Colquiri of silver and tin. It has been almost 5 - Mo rococo IG B 6 - Cerro Scpo unknown until now as a source of gemstones. 7 - Kami 8 - Alto Chapare Only a few collectors of rare gems have 9 - Sari Ramon area 10- Chuquitania known about the world's best cut cassiterites 11 - La Gaiba and phosphophyllites, but the situation has changed with the large production of ametrine in recent years; this has flourished in Bolivia's recent relatively stable political situation. Some relevant features of Bolivian gemstones and ornamental stones, including rare collector stones and several recent finds, are summarized below.

Apatite Attractive transparent purple apatites were found in the 1940s in Llallagua and Figure 1: Map of Bolivia showing main localities were described by Bandy (1944). More mentioned in the text. recently large apatite crystals have come from a magnetite-hematite vein cutting a transparent core. According to the X-ray dacite laccolith in Potosi department analysis, both the core and crust are probably (Figure 1). Crystals are up to 10 cm long, carbonate-hydroxylapatite. Stones faceted yellowish and opaque, and some have a from this material are yellowish-white and

© Gemmological Association and Gem Testing Laboratory of Great Britain ISSN: 1355-4565 Figure 3:3: Wood-tinWood-tin cassiteritecassiterite fromfrom Macha, Figure 2:2: CassiteriteCassiterite from from Viloco, Viloco, weights weights 11.77, 11.77, length of largest cabochon 19 mm (photo:(photo: 2.31 andand 1.09 1.09 ct ct(photo: (photo: P. Korbel). P. Korbel). PP. Korbel).

contaicontainn unusuaunusuall needle-likeneedle-like inclusionsinclusions.. TheirTheir CrystalCrystalss fromfrom VilocoViloco areare uupp toto 8 ccmm longlong andand refractivrefractivee indiceindicess areare nono = 1.6421.642 andand areare oftenoften partiallpartiallyy transparent,transparent, usuallyusually iinn a nene = 1.637,1.637, specificspecific gravitygravity isis 3.11-3.13.3.11-3.13. TheyThey thithinn layerlayer nearnear thethe surface.surface. ThThee transparenttransparent have aa palepale orange orange luminescence luminescence in inshortwave short­ parpartt iiss usuallusuallyy yelloyelloww ttoo browbrownn butbut ultravioletwave ultraviolet (SWUV). (SWUV). colourlescolourlesss cassiteritescassiterites araree alsalsoo knownknown (Figure 2). 2). Faceted Faceted cassiterites cassiterites are are usually usually less les s thathann 5 cctt bubutt therethere araree rarerare stonesstones uupp toto 2255 ctct.. BerBeryll 4242 Y FacetedFaceted cassiteritescassiterites areare extremelextremelyy beautiful,beautiful, VeryVery largelarge opaqueopaque crystalscrystals ooff beryberyll havehave bubutt theitheirr brittlenesbrittlenesss andand relativerelative softnesssoftness beebeenn knownknown forfor a lonlongg timetime fromfrom pegmatitespegmatites makmakee themthem unsuitablunsuitablee forfor settingsetting iinn ringsrings.. neanearr SantaSanta RosaRosa,, SanSan IgnacioIgnacio dede VelascVelascoo andand A secondsecond typtypee ofof cassiteritecassiterite usedused inin SanSan Ramon,Ramon, easeastt ofof SantaSanta CruzCruz.. RecentlyRecently jewellerjewelleryy iiss thethe opaqueopaque colloidacolloidall varietyvariety piecepiecess withwith a transparenttransparent bluisbluishh corcoree havehave callecalledd 'wood-tin','wood-tin', knowknownn mainlmainlyy fromfrom thethe beebeenn founfoundd anandd a fewfew lightlight aquamarineaquamariness upup Condor-IquinaCondor-Iquina volcanicvolcanic plateaplateauu ofof ththee PotosiPotosi ttoo aboutabout 2 cctt havehave beebeenn cutcut frofromm crystalscrystals department.department. ItIt hashas a finefine agate-likeagate-like structure,structure, frofromm ththee SanSan RamonRamon area.area. ReportsReports ooff alluvialalluvial sometimessometimes withwith layerslayers ofof opalopal oorr chalcedonychalcedony 'aquamarine'aquamarine'' crystalscrystals fromfrom streamsstreams drainingdraining andand iiss usuallyusually brownbrown,, creacreamm oror yellowyellow,, moremore thethe batholitbatholithh northnorth ofof LaLa PazPaz citycity havehave notnot rarelrarelyy blackblack,, reredd oorr pinkpink.. CabochonsCabochons cutcut fromfrom beebeenn confirmed.confirmed. thithiss materialmaterial cancan bbee ververyy attractivattractivee witwithh a IInn ththee eastereasternn SantSantaa CruCruzz departmentdepartment highhigh lustrelustre (Figure 3). 3). emeralemeraldd occuroccurss iinn veinveinss ofof quartquartzz andand feldsparfeldspar cuttingcutting shales.shales. TheThe crystalcrystalss areare uupp toto ChalcedonyChalcedony 1 cmcm inin length,length, areare lightlight greengreen toto aa goodgood emeraldemerald green,green, bubutt araree opaquopaquee anandd nono WhitWhitee toto greenisgreenishh oror greygrey chalcedonychalcedony cuttablcuttablee materiamateriall hashas yeyett beebeenn found.found. withwith smallsmall blebblebss ofof nativenative coppecopperr (i(inn placesplaces oxidizeoxidizedd toto greengreen malachitemalachite)) iiss a veryvery unusualunusual ornamentaornamentall stone.stone. ItIt waswas useusedd forfor CassiteriteCassiterite beadbeadss bbyy pre-Columbiapre-Columbiann IndianIndianss anandd thethe CassiteritCassiteritee isis ononee ofof ththee mostmost importantimportant sourcesource wawass rediscovererediscoveredd (Ahlfeld(Ahlfeld andand ReyesReyes,, BoliviaBoliviann mineralmineralss andand ththee depositsdeposits araree stillstill a 1955)1955) inin ththee TurcTurcoo Cu-depositCu-deposit iinn northernnorthern majormajor sourcesource ooff tintin.. ProbablProbablyy ththee world'sworld's bestbest OruroOruro department.department. cassiteritcassiteritee specimensspecimens comcomee frofromm ththee VilocVilocoo AnotherAnother typetype ofof chalcedonchalcedonyy waswas founfoundd bbyy minminee nearnear AracaAraca inin LaLa PazPaz department.department. ththee authorauthorss inin ththee vicinityvicinity ooff CapinotaCapinota neanearr

J. Gemm., 1998, 26,1,26,1,41-47 41-47 ChelseaChelsea FilterFilter and,and, whenwhen examinedexamined withwith a hand-held spectroscope, displaysdisplays two two absorp­ absorption tionlines lines in the in redthe partred partof the of spectrum.the spectrum . SomeSome stonesstones showshow a veryvery finefine agate-likeagate-like structurestructure andand othersothers containcontain a blackblack 'net''net' ofof FeFe­- oxides.oxides. MostMost ofof thethe roughrough materialmaterial isis exportedexported directlydirectly toto BrazilBrazil andand atat thethe 19951995 MunichMunich mineralmineral showshow thethe authorsauthors foundfound cutcut chromechrome chalcedonychalcedony describeddescribed asas 'apatite'apatite fromfrom Brazil',Brazil', whicwhichh couldcould welwelll havehave comecome originallyoriginally fromfrom thithiss sourcesource inin Bolivia.Bolivia. Figure 4:4: RoughRough chromechrome chalcedonychalcedony from Chiquitania, length length of oflargest largest piece piece 5 cm 5 (photocm (photo:: DanburiteDanburite P. Korbel).Korbel). ExcellenExcellentt doubly-terminatedoubly-terminatedd crystalcrystalss occuoccurr iinn metamorphosedmetamorphosed evaporitesevaporites inin ththee AltAltoo Cochabamba.Cochabamba. PoorlyPoorly consolidatedconsolidated CretaceousCretaceous ChaparChaparee regionregion easeastt ooff CochabambCochabambaa (Petrov(Petrov;, sandsand an andd gypsumgypsum marlmarl iiss cutcut bbyy a larglargee 1993).1993). ThThee danburitdanburitee crystalcrystalss araree usuallyusually numbenumberr ooff thithinn veinveinss containincontainingg chalcedonychalcedony opaque,opaque, duedue ttoo manymany dolomitedolomite inclusionsinclusions,, butbut whichwhich iiss usuallusuallyy milkmilkyy bubutt somesome bluisbluishh piecespieces somesome havehave beebeenn used inin theirtheir naturalnatural shapeshape ttoo resemblinresemblingg oldold chalcedonychalcedony frofromm NamibiaNamibia createcreate unusuaunusuall jewelleryjewellery.. AlthougAlthoughh crystalcrystalss ooff werweree alsoalso foundfound.. ThickeThickerr veinveinss usuallusuallyy havhavee a uupp ttoo 5 cmcm longlong havehave beenbeen found,found, theirtheir normalnormal centrecentre fillefilledd witwithh anhydrite.anhydrite. lengthlength iiss 1 toto 33 em cm. .Several Severa lspecimens specimens of o fbluish bluish danburitdanburitee witwithh paralleparallell inclusioninclusionss ofof a blueblue­- ChromChromee chalcedonychalcedony gregreyy amphiboleamphibole,, magnesioriebeckite,, havhavee beebeenn founfoundd anandd cabochon-cucabochon-cutt specimenspecimenss showshow 4343 RecentlRecentlyy discoverediscoveredd iinn BoliviaBolivia,, chromechrome a strongstrong cat's-eyecaf s-eye effecteffect (Figure 5). 5). chalcedonchalcedonyy iiss callecalledd 'Chiquitanita'Chiquitanita'' bbyy localocall jewellerjewellerss frofromm ititss occurrencoccurrencee iinn thethe DiamonDiamondd ChiquitaniChiquitaniaa regioregionn iinn eastereasternn SantSantaa CruzCruz departmentdepartment.. ItIt occuroccurss aass smalsmalll veins iinn a DiamondDiamondss havhavee beebeenn reportereportedd fromfrom silicifiesilicifiedd lateritlateritee overlyinoverlyingg CrCr-- anandd NiNi­- PermiaPermiann glaciaglaciall sedimentsedimentss ooff ththee TequejeTequeje,, bearinbearingg ultrabasiultra basicc intrusives.. SomSomee partpartss araree coloured brown by Fe-oxides but the best coloured brown by Fe-oxides but the best Figure 5:5: Cars-eyeCat's-eye danburite from Alto materiamateriall iiss translucentranslucentt greegreenn anandd facetablefacetable Chapare,Chapare, cut cut stone stone 0.49 0.49 ct (photoct (photo:: P. Korbel). P. Korbel). (Figure 4) 4).. ThThee refractivrefractivee indeindexx ooff ththee chromchromee chalcedonchalcedonyy iiss 1.530-1.551.530-1.5500 witwithh a birefringencebirefringence uupp ttoo 0.000.0055 anandd SSGG ooff 2.56-2.572.56-2.57.. IItt iiss a polypoly­- crystallincrystallinee aggregateaggregate,, whicwhichh doedoess nonott fluorescefluoresce iinn eitheeitherr shortshort-- oorr long-wavlong-wavee ultravioletultraviolet,, bubutt iitt iiss brightbright reredd undeunderr a ChelseaChelsea ColourColour Filter.Filter. TheThe absorptioabsorptionn spectruspectrumm showshowss aann emerald-likemerald-likee pattern witwithh twtwoo broabroadd bandbandss aatt 414166 anandd 606055 nm andand a smallsmall peakpeak atat 684684 nm,nm, withwith aa distincdistinctt minimuminimumm aatt 515100 nm. SimilarSimilar materialmaterial wawass describedescribedd undeunderr ththee tradtradee namnamee 'Mtorolite'Mtorolite'' frofromm MtoroshangMtoroshangaa iinn ZimbabwZimbabwee (se(seee PhillipPhillipss anandd BrownBrown,, 19891989,, anandd WebsterWebster,, 1994)1994).. DyeDyedd chalcedonchalcedonyy (imitatin(imitatingg chrysoprasechrysoprase)) iiss brownish-rebrownish-redd onlonlyy undeunderr ththee

GemstonesGemstones andand ornamentalornamental stonesstones fromfrom Bolivia:Bolivia: a rrevieweview FluoriteFluorite ThThee ColquiriColquiri anandd CondeauquCondeauquii fluoritefluorite occurrenceoccurrencess northnorth ofof OruroOruro havehave yieldeyieldedd manymany larglargee piecepiecess ofof transparenttransparent blue-greeblue-greenn materialmaterial..

GarnetsGarnets DarDarkk almandinealmandiness uupp toto abouaboutt 1 ctct havehave beebeenn cutcut fromfrom smallsmall pebblepebbless fromfrom alluvialalluvial depositsdeposits iinn PotosPotosii department,department, bubutt gem­gem- qualitqualityy garnetsgarnets araree rarraree inin Bolivia.Bolivia.

PhosphophyllitePhosphophyllite BByy farfar ththee world'sworld's besbestt crystalscrystals ooff phosphophyllitphosphophyllitee werewere foundfound iinn thethe 1950s1950s andand Figure 6:6: Phosphophyllite Phosphophyllite crystal crystal about about 15 em15 cm1960s1960 s iinn thethe deepestdeepest levelslevels,, abouaboutt 300300 m long onon matrix. matrix.

Suapi anandd otherother riversrivers iinn northernnorthern LaLa PaPazz departmendepartmentt bbyy AhlfeldAhlfeld anandd ReyeReyess (1955)(1955) andand OppenheimOppenheim (1943)(1943).. TheyThey araree colourlescolourlesss oror pale yellow well-developedpale yellow well-developed crystals generally crystals gener­ ally weighinweighingg 0.10-0.30.10-0.355 ct,ct, withwith somesome upup ttoo 4444 1 ct. Two concessions1 ct. Two concessions were worked were in the worked in the 19208,1920s, bubutt theythey proveprovedd ttoo bbee uneconomic.uneconomic. KimberliteKimberlitess havehave beenbeen reportereportedd recentlyrecently fromfrom ththee AyopayAyopayaa provincprovincee nortnorthh ooff Cochabamba,Cochabamba, butbut informatioinformationn aboutabout diamonddiamondss isis lacking.lacking.

Figure 8: Ametrine slab with strong Brazil Figure 7:7: Tri-eolour Tri-colour ametrine ametrine from from La LaGaiba, Gaiba, Figure Ametrine slab with strong Brazil twinning, 39 x 22 mm (photo: P. Korbel). 81.52 etct (photo: (photo: P. P.Korbel). Korbel). twinning, 39 x 22 mm (photo: P. Korbel). Figure 9: Tri-eolourTri-colour quartz (purple-yellow­(purple-yellow- colourless) from from La La Gaiba, Gaiba, length length 30 mm 30 mm(photo: (photo: P. Korbel).Korbel)..

J. Gemm., 1998, 26,26,1, 1, 41-4741-47 ^^^0

**Z r"?^s. Figure 10: San FerritinFermin amethyst minemine (photo:(photo: J. HyrHyrsl).sl).

Figure 12: Quartz with dravite (4.20 ct) andand arsenopyrite (5.69 ct) inclusions fromfrom Kami (photo: P.P. Korbel).Korbel).

populapopularr BoliviaBoliviann gemstongemstonee (Figures 77,, 8 and 9). LocaLocall jewellerjewellerss calcalll iitt 'Bolivianita''Bolivianita'.. TheThe trutruee localitylocality wawass unknowunknownn foforr a lonlongg time,time, andand somesome originalloriginallyy thoughthoughtt thathatt iitt camecame fromfrom BrazilBrazil oorr thathatt itit wawass syntheticsynthetic.. AmetrineAmetrine occursoccurs atat AnahAnahii neanearr LLaa GaibaGaiba iinn ththee fafarr easteast 45 45 Figure 11: Amethyst specimens from San FFerminermin ofof thethe SantSantaa CruzCruz departmentdepartment inin (photo: J.J. Hyrsl). Hyrsl). hydrothermalhydrothermal quartzquartz veinveinss whicwhichh cutcut dolomitesdolomites andand limestones.. ThThee AnahAnahii minemine was described by Vasconcelos et al. (1994) underground,underground, ofof thethe famousfamous silversilver depositdeposit ooff was described by Vasconcelos et al. (1994) and Collyer et al. (1994), but since then more CerroCerro RicoRico dede PotosiPotosi (Hyrsl(Hyrsl andand Petrov, and Collyer et al. (1994), but since then more ametrine deposits have been found in the 1996).1996). TheyThey havehave a uniqueunique blue-greenblue-green colour, ametrine deposits have been found in the La Gaiba area at the Mina Pobre, although somesome areare partiallypartially transparenttransparent andand thethe La Gaiba area at the Mina Pobre, although quality and quantity do not match that from biggestbiggest crystalscrystals areare upup ttoo 1515 emcm longlong quality and quantity do not match that from the Anahi mine. The mine at La Gaiba is (Figure 6). OnlyOnly a fewfew hundredhundred crystalscrystals werewere the Anahi mine. The mine at La Gaiba is probably also the world's only source of found.found. PhosphophyllitePhosphophyllite isis extremelyextremely difficultdifficult probably also the world's only source of naturally coloured (unheated) citrine at the toto facetfacet duedue toto itsits perfectperfect cleavage, andand ofof thethe naturally coloured (unheated) citrine at the present time (Vasconcelos et al, 1994). limitedlimited numbernumber ofof facetedfaceted stonesstones whichwhich dodo present time (Vasconcelos et at., 1994). existexist veryvery fewfew areare overover 1010 ctct (maximum(maximum 7474 ct,ct, Amethyst ofof ververyy goodgood qualityquality isis wellwell AremArem 1987).1987). Consequently,Consequently, theythey areare inin greatgreat knownknown fromfrom thethe AnahiAnahi mine.mine. OtherOther amethystamethyst demanddemand byby collectors.collectors. occurrencesoccurrences fromfrom thethe LaLa GaibaGaiba areaarea havehave yieldedyielded crystalscrystals upup ttoo 5 kgkg suitablesuitable forfor PyrargyritePyrargyrite spheresspheres oror carving.carving. AhlfeldAhlfeld andand ReyesReyes (1955)(1955) describeddescribed a hugehuge hydrothermalhydrothermal amethystamethyst SeveralSeveral largelarge facetedfaceted stonesstones werewere cutcut fromfrom veinvein 6 kmkm longlong andand 4 toto 6 m widewide nearnear thethe materialmaterial fromfrom thethe veryvery richrich silversilver depositdeposit atat town of of Santa Santa Ana Ana in Santa in SantaCruz department, Cruz depart­ ColquechacaColquechaca south-eastsouth-east ofof Orura.Oruro. ment, butbut thethe amethystamethyst herehere isis ofof poorpoor quality.quality. NotNot farfar fromfrom SantaSanta Ana,Ana, otherother QuartzQuartz verticalvertical amethystamethyst veinsveins occuroccur nearnear thethe villagevillage WithoutWithout doubt,doubt, ametrineametrine (bi-colour(bi-colour ofof SanSan Fermin.Fermin. OneOne veinvein isis aboutabout 1 m widewide amethyst-citrineamethyst-citrine quartz)quartz) isis currentlycurrently thethe mostmost and is isaccessed accessed by a 33by m adeep 33 shaft m deep shaft

GemstonGemstoneses anandd oornamentalrnamental stonesstones from BoliviaBolivia:: aa r revieweview Figure 13: SodaSodalite lite boulder from Cerro Sapo, Figure 14: SodalitSodalitee mining camp on Cerro Sapo width 44 emcm (photo: J.J. Hyrsl) Hyrsl).. (photo(photo:: JJ.. HyrSl) Hyrsl)-.

(Jul(Julyy 1995,1995, Figure 10). ThThee veinvein hahass manymany SapphireSapphire cavitiescavities withwith crystalcrystalss anandd thethe amethystamethystss areare stronglystrongly zonedzoned,, ththee toptopss ooff crystalscrystals beingbeing Recently,Recently, severalseveral opaquopaquee toto translucenttranslucent blueblue usuallusuallyy coverecoveredd bbyy milkymilky quartz.quartz. AmethystAmethyst sapphiressapphires havhavee beebeenn foundfound associatedassociated withwith fromfrom thethe localitylocality isis rarelyrarely cuttablcuttablee andand isis almandinalmandinee iinn alluviualluviumm iinn PotosPotosii department.department. moremore usefuusefull foforr smallsmall carvingcarvingss oror tumbledtumbled TheyThey reacreachh onlyonly a fewfew millimetremillimetress iinn sizesize andand stonesstones (Figure 11). fewfew havhavee beebeenn facetedfaceted.. OneOne 909000 g translucenttranslucent sapphiresapphire wawass founfoundd bbyy DrFDr F.. AhlfelAhlfeldd inin thethe Quartz witwithh unusuaunusuall inclusionsinclusions comescomes golgoldd placerplacerss ooff ththee YungaYungass ddee LLaa PazPaz,, bubutt iitt tootoo frofromm severalseveral BoliviaBoliviann localitielocalitiess andand,, whenwhen wawass ooff poopoorr cuttincuttingg quality.. properlproperlyy cutcut,, cacann bbee aann interestininterestingg materialmaterial 4646 foforr jewelleryjewellery.. ThThee mosmostt interestininterestingg inclusionsinclusions araree browbrownn needleneedless ooff dravitdravitee tourmalintourmalinee andand SodalitSodalitee silversilveryy metallimetallicc blebblebss ooff pyrrhotite,pyrrhotite, arsenopyritarsenopyritee anandd marcasitemarcasite,, alalll frofromm thethe BeadBeadss ooff blubluee sodalitsodalitee havhavee beebeenn foundfound tungstetungstenn deposidepositt ooff KamKamii neanearr CochabambaCochabamba durinduringg archaeologicaarchaeologicall researcresearchh frofromm almosalmostt alalll (Figure 12). AndeaAndeann culturaculturall epochepochss includinincludingg ththee oldestoldest MizquMizquee perioperiodd (900-60(900--6000 BC)BC).. ThThee findfindss covecoverr a Smoky quartz iiss rarraree iinn BoliviaBolivia,, bubutt a fewfew ververyy larglargee areareaa ranginrangingg frofromm EcuadoEcuadorr ttoo larglargee cleacleann crystalcrystalss uupp ttoo abouaboutt 5500 ccmm longlong Argentina.. BecausBecausee a sodalitsodalitee deposidepositt wawass notnot havhavee comcomee frofromm recenrecentt diggingdiggingss iinn thethe knowknownn iinn ththee AndesAndes,, thertheree werweree hypotheseshypotheses pegmatitepegmatitess ooff ththee PrecambriaPrecambriann shielshieldd ooff abouaboutt aann origioriginn outsidoutsidee SoutSouthh America.America. SantSantaa CruCruzz department.department. HoweverHowever,, iinn 19231923,, ththee GermaGermann geologistgeologist Silicified limestone:limestone: AAnn unusuaunusuall fluorescentfluorescent FF.. AhlfelAhlfeldd founfoundd sodalitsodalitee outcropoutcropss oonn CerroCerro rocrockk comecomess frofromm PajchPajchaa PataPata,, soutsouthh ooff SapSapoo (420(42000 m)m),, AyopayAyopayaa province,province, CochabambaCochabamba.. IItt iiss a silicifiesilicifiedd dolomiticdolomitic CochabambCochabambaa departmendepartmentt (Ahlfel(Ahlfeldd andand limestonlimestonee frofromm ththee CretaceouCretaceouss TorotoroTorotoro WegenerWegener,, 1931)1931).. NinNinee ololdd tunneltunnelss werweree foundfound FormationFormation.. WhitWhitee carbonatcarbonatee graingrainss havhavee a bbyy Ahlfeld,, ththee largeslargestt beinbeingg 9900 m lonlongg andand nenett ooff dardarkk chalcedonchalcedonyy veinletsveinlets", widerwider 5 m highhigh.. TheiTheirr ageagess rangrangee frofromm pre-Incapre-Incann toto veinletveinletss araree bluisbluishh anandd sometimesometimess araree filledfilled ththee lateslatestt perioperiodd ooff mininminingg iinn ththee eighteentheighteenth bbyy quartquartzz microcrystals.. UndeUnderr short-waveshort-wave centurcenturyy bbyy ththee Jesuits, whwhoo believebelievedd thetheyy werewere UVUV,, ththee carbonatcarbonatee fluorescefluorescess whitwhitee anandd ththee mininminingg lapilapiss lazuli.. chalcedonchalcedonyy iiss green,, whilwhilee undeunderr long-wavelong-wave ThThee sodalitsodalitee veiveinn iiss abouaboutt 3 kkmm lonlongg (th(thee UUVV ththee carbonatcarbonatee iiss yellowisyellowishh anandd ththee ' productivproductivee parpartt iiss mucmuchh smallersmaller)) anandd frofromm 1 ttoo chalcedonchalcedonyy violetviolet.. ThThee carbonatcarbonatee showsshows 5 m widewide.. IInn detaildetail,, ththee 'vein' iiss a uniquuniquee typetype phosphorescencphosphorescencee afteafterr exposurexposuree ttoo eitheeitherr ooff carbonatitcarbonatitee dykedyke,, consistinconsistingg mainlmainlyy ooff palpalee longlong-- oorr short-wavshort-wavee UV.. greegreenn ankeriteankerite,, whitwhitee barytebaryte,, blubluee sodalitsodalitee anandd

J.Gemm.,J. Gemm" 19981998,26,1,41^7, 26,1, 41-47 OtherOther mineralsminerals andand ornamentalornamental rockrockss ChrysocollChrysocollaa andand malachitemalachite araree knownknown frofromm ththee vicinitievicinitiess ooff ththee AltiplanoAltiplano coppercopper depositsdeposits,, anandd thertheree araree minorminor occurrencesoccurrences ooff colourlescolourlesss topatopazz andand adularescentadularescent feldspafeldsparr iinn thethe alluvialalluvial 'woo'woodd tintin'' depositdepositss ofof MachMachaa inin ththee PotosiPotosi departmentdepartment.. PartiallPartiallyy transparenttransparent sideritesiderite crystalscrystals uupp ttoo 2020 ccmm lonlongg havhavee beenbeen discoverediscoveredd recentlrecentlyy iinn PotosiPotosi.. AlsAlsoo frofromm PotosPotosii iiss aann ornamentalornamental Figure 15: 15: StromatoliteStromatolite from from Potosi; Potosi; the theedge edge of ofstromatolitestromatolit e callecalledd Tucalita'Pucalita'' afterafter itsits locationlocation the cubecube is is 8 8em cm (photo: (photo: J. Hyrsl).J. Hyrsl). inin ththee CretaceouCretaceouss PucaPuca formationformation.. IItt iiss anan algalalgal rocrockk consistingconsisting mostlymostly ooff calcitecalcite,, dolomitedolomite andand minominorr amountsamounts ofof analcite,analcite, dawsonite,dawsonite, quartquartzz witwithh aann overaloveralll hardneshardnesss ooff abouaboutt 4 andand natrolitnatrolitee anandd sulphidessulphides (Figure 13). 13). It Icutst cut boths bot h SGSG ooff 2.62.6.. TheThe stromatolitestromatolite isis yellow-browyellow-brownn toto a nephelinenepheline syenitesyenite bodybody andand itsits surroundingsurrounding coffee-browcoffee-brownn withwith distinctdistinct dark-browndark-brown oorr hornfelhornfelss andand slate.slate. ThThee sodalitesodalite iiss aann attractiveattractive blacblackk layerlayerss anandd iiss cucutt andand polishepolishedd ttoo displaydisplay blubluee andand sometimessometimes formformss larglargee slabsslabs witwithh a ititss wavwavyy oorr concentriconcentricc bandingbanding,, ththee latterlatter distincdistinctt zonalzonal structure.structure. CabochonsCabochons overover 2 mmmm appearinappearingg asas 'eyes'eyes'' iinn appropriateappropriate specimensspecimens thicthickk areare opaqueopaque.. OneOne ofof thethe claimclaimss oonn ththee veiveinn (Figure 15). 15). iiss currentlcurrentlyy exploiteexploitedd bbyy aann ItalianItalian company,company, A neneww reredd varietvarietyy ooff stromatolitstromatolitee hahass beebeenn whichwhich hashas a veryvery welwelll equippedequipped mininminingg campcamp founfoundd iinn ththee OrurOruroo department. ItItss colourcolour iiss oonn ththee slopeslope ooff CerrCerroo SapoSapo (Figure 14). 14). The Th e probablprobablyy causedcaused bbyy hematithematitee anandd itsits structurestructure contencontentt ofof ankeriteankerite causescauses brownbrown patchespatches inin thethe iiss thethe samesame aass thethe yelloyelloww varietyvariety.. 4747 sodalitesodalite andand hinderhinderss outdooroutdoor ornamentaornamentall usesuses.. MorMoree recentlyrecently,, a veiveinn ofof sodalitesodalite uupp ttoo 3 cmcm widewide andand ofof goodgood qualityquality waswas foundfound ReferenceReferencess neanearr ththee towtownn ofof IndependenciaIndependencia.. IItt lieslies aboutabout AhlfeldAhIfeld,, F.,F., anandd Reyes,Reyes, J.M.,J.M., 1955.1955. LaLass especieespeciess mineralesminerales 2020 km southsouth ooff ththee CerroCerro SapoSapo occurrenceoccurrence ddee Bolivia.Bolivia. BilbaoBilbao and has the same strike. Ahlfeld,Ahlfeld, F.,F., andand Wegener,Wegener, R.R.,, 1931.1931. UbeUberr diedie HerkunfHerkunftt derder and has the same strike. iimm BereichBereich altperuanischeraltperuanischer KultureKulturenn gefundenengefundenen SchmuckstuckeSchmuckstucke auauss Sodalith.Sodalith. Ztschr. Ethnol. 6363,288-96, 288-96 Arem,Arem, J.E.J.E.,, 1987.1987. Color encyclopedia of gemstones. 2nd2nd Ed.Ed. TourmalinTourmalinee VanVan NostranNostrandd ReinholdReinhold,, NeNeww YorkYork GreenGreen tourmalinetourmaline occuroccurss iinn thethe BandyBandy,, M.C.M.C.,, 1944.1944. Mineralogy of Llallagua, Bolivia. PatinoPatino MinesMines & EnterpriseEnterprisess ConsolidatedConsolidated,, LLaa PazPaz pegmatitespegmatites ooff ththee PrecambrianPrecambrian shieldshield ooff Collyer,Collyer, T.,T., Fuzikawa,Fuzikawa, K.K.,, andand Schwarz,Schwarz, D.,D., 1994.1994. DasDas eastereasternn SantaSanta CruCruzz department,department, bubutt thethe cutcut Ametrin-VorkommenAmetrin-Vorkommen vovonn AnayAnay,, SantaSanta Cruz,Cruz, Bolivien.Bolivien. stonesstones araree totooo darkdark ttoo bbee attractive.attractive. Z.Z. Dt. Gemmol. Ges., 4343,, 117-26117-26 Hyrsl,Hyrsl, J.J.,, anandd Petrov,Petrov, A.A.,, 1996.1996. PotosPotosii unundd OruroOruro - diedie bedeutendstebedeutendstenn Silbererz-LagerstattenSilbererz-Lagerstatten Boliviens.Boliviens. VivianiteVivianite Mineralien-Welt, 77,, 36-4936-49 OppenheimOppenheim,, V.v.,, 1943.1943. DiamondDiamondss iinn thethe northeasternnortheastern GoodGood transparentransparentt crystalscrystals havehave beenbeen BolivianBolivian AndesAndes.. Econ. Geol., 38,38, 658--

Gemstones and ornamental stones fromfrom Bolivia: aa reviewreview BOOK REVIEWS

Rock-fonning minerals. [Second edition. Vol. 2B. beingbeing writtenwritten andand publishedpublished quitequite sslowllowly soso thathatt thethe Single-chainBOOK REVIEWS silicates .] suddensudden exexpenspensee isis notnot tootoo irksome!irksome! WhileWhile forfor GeologicalGeological Society members the cost is very reasonable the list price W.ARock-formin. DEER, RA.g minerals HOWIE .AND [Secon J. ZUSSMAN,d edition .1997. Vol. 2BThe. Society members the cost is very reasonable the list price Single-chainGeological silicates.] Society, London. pp x, 764, hardcover. £99.00 seemsseems fair,fair, bbearinearingg inin mindmind thethe workwork donedone overover manymany yearsyears andand soso painstakinglypainstakingly assembled.assembled. M.O'D.M.O'D. WA. [£50DEER to Geological, R.A. HOWI SocietyE AN membersl.D J. ZUSSMAN ISBN, 18977991997. Th77e 2.Geologica Obtainablel Society from, London the Society, pp x , at764 Burlington, hardcover .House, £99.00 Piccadilly,[£50 to Geologica Londonl Societ WIy V members] OJU [membersl. ISBN 1 89779 or 9[for 77 CartierCartier 1900-1939.1900-1939. members2. Obtainabl ofe thefrom public)the Societ fromy a tGeological Burlington SocietyHouse, J.J. RUDOERUOOE,, 1997. BritisBritishh MuseumMuseum PressPress forfor thethe TrusteesTrustees ofof PublishingPiccadilly, House,Londo nUnit W1 7,V Br OJassUmill [members Enterprise] oCentre,r [for TheThe BritisBritishh Museum, London.London, pppp 344,344, illus.illus. inin cocolourlour, memberBrassmills Lane,of th Bathe public BA1 3JN] fro. m Geological Society hardcover.. £50.00.£50.00. ISBNISBN 0 71417141 05840584 8.8. WhilePublishin theg progressHouse, Uni of tthe 7, Brassmilsecond editionl Enterpris [ofe DHZ Centre or, RFMlBrassmil wouldl Laneexpect, Bat toh BAproduce1 3JN. a much larger body of TheThe quickesquickestt glanceglance intintoo this beautifubeautifull boobookk showsshows informationWhile th eoverall progres, thiss o fvolume the secon willd editioprobablyn [o fbe DHZ found or thatthat iitt isis aann exhibitioexhibitionn catalogue.. InIn this casecase ththee exhibitionexhibition toRFM] display woul da expecproportionatelyt to produc greatere a muc increaseh larger overbody itsof iiss duedue (a(att ththee timtimee ooff writingwriting)) toto bbee heldheld aatt thethe originalinformatio form,n overall first ,published this volum ine 1961.will probablMineralogistsy be foun andd MetropolitanMetropolitan MuseumMuseum ooff Art,Art, NeNeww YorkYork,, frofromm 2 ApriAprill toto geologiststo display alreadya proportionatel know thaty thegreate amphiboler increas egroup over hasits 3 AugustAugust 1997,1997, andand atat TheThe BritishBritish MuseumMuseum fromfrom 3 OctoberOctober alwaysoriginal formposed, firs t problemspublished inof 1961 determination. Mineralogist s andand 19971997 ttoo 1 FebruaryFebruary 1998.1998. WhileWhile mosmostt ofof thethe textextt formformss thethe geologistnomenclatures alread andy kno contirtuesw that thtoe amphiboldo so: advancese group hains cataloguecatalogue,, preliminarypreliminary chapterchapterss describdescribee ththee historhistoryy ofof thethe determinativealways pose dtechniques problem haves o,f however,determinatio succeededn an ind firmfirm ofof CartierCartier frofromm itsits foundationfoundation bbyy Louis-FrLouis-Frangoian~oiss settingnomenclatur out a ebase an dfor continue some kinds t oof dpermanento so: advance structures in CartieCartierr iinn 18418477 atat 2299 RuRuee Montorgeuil,, Paris, anandd itsits fordeterminativ the group,e intotechnique whichs itshave individual, however members, succeede mayd fitin divisiondivision intintoo threthreee partsparts durinduringg ththee earlierearlier partpart ooff the 20th20th settinmore geasily out a thanbase beforefor som. Ate kin thde otimef permanen of reviewt structuring thee centurcenturyy witwithh separateseparate enterpriseenterprisess iinn Paris, NeNeww YorkYork and foInternationalr the group , Mineralogicalinto which its Associationindividual member is preparings may fitot London.. The yearyearss frofromm ththee establishmenestablishmentt ooff ththee threethree morpublishe easil a reviewy than ofbefore amphibole. At th groupe tim enomenclature. of reviewing the businessebusinessess araree describedescribedd iinn ththee secondsecond chapter,, whicwhichh isis 48 International Mineralogical Association is preparing to followefollowedd bbyy briebrieff reminiscencereminiscencess ooff celebratecelebratedd clients andand 48 Double-chain silicates are not all amphiboles, publish a review of amphibole group nomenclature. bbyy a revierevieww ooff productioproductionn processesprocesses.. ProcedureProceduress andand however, though the group takes up the bulk of the text. Double-chain silicates are not all amphiboles, markmarkss peculiapeculiarr ttoo eaceachh ooff ththee threthreee branchebranchess araree described.described. The interesting group of biopyriboles, the name coined in however, though the group takes up the bulk of the text. ThThee threthreee househousess maintaimaintainn theitheirr owownn archivearchivess whicwhichh areare 1911 from pyroxene, amphibole and 'bio' to include the The interesting group of biopyriboles, the name coined in fortunatelfortunatelyy availablavailablee foforr jewellerjewelleryy historianshistorians:: pagepagess fromfrom mica group, is surveyed for the first time in a major refer­ 1911 from pyroxene, amphibole and 1510' to include the stocstockk bookbookss araree reproduced.reproduced. ence book. mica group, is surveyed for the first time in a major reference The amphiboles are treated in four sections following ThThee catalogucataloguee propeproperr dealdealss firsfirstt witwithh ththee gradualgradual book. emergencemergencee ooff a distinctivdistinctivee stylstylee anandd thethenn witwithh ththee Russian a generalThe amphibole introduction:s are Mg-Fe-Mn-Litreated in four amphiboles:sections followin calcicg stylstylee whicwhichh begabegann ttoo appeaappearr frofromm abouaboutt 19019066 witwithh thethe aamphiboles general introduction (including: Mg-Fe-Mn-L tremolite ani amphibolesd actinolite,: calci thec productioproductionn ooff hardstonhardstonee flowerflowerss anandd whicwhichh laterlater amphibolesections likelys (includin to be of gmost tremolit intereste toan dthe actinolite gemmologist):, the developedevelopedd intintoo a widwidee varietvarietyy ooff objectobjectss rivallinrivallingg bubutt notnot sectionsodic-calcics likel yamphiboles: to be of mos sadiet interes amphiboles.t to the gemmologist) Then the: totooo closelcloselyy resemblinresemblingg thosthosee produceproducedd bbyy ththee firfirmm ooff sodic-calcibiopyribolesc amphibolesare described: sodi andc amphibolesfollowed by. Thethe nother the FabergFabergee whoswhosee LondoLondonn shoshopp hahadd closeclosedd iinn 1917, leadingleading biopyriboledouble-chains arsilicatese describe deerited an andd followe howieite,d b ynamed the otheafterr ttoo a movmovee ooff theitheirr clientelclientelee ttoo CartierCartier.. GolGoldd anandd eenamenamell double-chaitwo of the book'sn silicate authors.s deerit e and howieite, named after fashiofashionn accessoriesaccessories,, includinincludingg cigarettcigarettee anandd vanitvanityy casecasess two Eachof th esection book's containsauthors. its own list of references and aass welwelll aass watcheswatches,, araree describedescribedd iinn a chaptechapterr precedinprecedingg a speciesEac hare sectio describedn contain structurallys its own lisandt o fchemically, references withand treatmentreatmentt ooff ththee EgyptiaEgyptiann stylstylee whicwhichh flourisheflourishedd fromfrom specienotes ons ar experimentale described work,structurall thermodynamic,y and chemically optical, wit andh abouaboutt 19119100 ttoo ththee 1930s1930s:: PersianPersian,, IndianIndian,, ChinesChinesee andand notemagnetics on experimenta properties.l work Paragenesis, thermodynamic completes, optica l anthed JapanesJapanesee stylestyless ooff jewellerjewelleryy anandd accessorieaccessoriess followed.followed. magnetidescriptionc propertiesof each mineral.. Paragenesi As in previouss complete volumess th ofe descriptioboth editions,n of eaclistsh mineralshow .a Anumbers in previou of representatives volumes of ThThee catalogucataloguee continuecontinuess witwithh aann accounaccountt ooff CartierCartier''ss botexamples,h editions details, list s beingshow referreda numbe tor othef representativ appropriatee ususee ooff coloucolourr combinationcombinationss (blac(blackk materialmaterialss witwithh examplespapers. The, detail text scontains being well-drawnreferred to diagramsthe appropriat and thee diamonddiamondss araree especiallespeciallyy characteristic)characteristic),, witwithh diamonddiamond paperstypeface. Th is eeasy tex t tocontain read. s well-drawn diagrams and the jewellerjewelleryy betweebetweenn ththee warwarss anandd witwithh a revierevieww ooff designdesign typefacNaturallye is eas ythis to readis a. text for reference and not for drawingsdrawings.. TherTheree iiss a glossarglossaryy anandd a shorshortt bibliographybibliography.. 'readingNaturall through'y this (althoughis a text leafing for referenc throughe theand text no whilet for Itemitemss araree reproducereproducedd witwithh fulfulll descriptiondescriptionss whichwhich 'readinon the gtrack through of one' (althoug queryh throwsleafing upthroug manyh th othere text pointswhile includincludee provenanceprovenance,, measurements,, identificatioidentificationn ooff owhichn the tracneedk ofnoting one quer fory throwdetaileds u pexamination many other pointlater):s .materials. materials,, presenpresentt whereaboutwhereaboutss anandd publicatiopublicationn wherwheree whicgemmologistsh need notinneed gto foapproachr detaile amphiboled examinatio nomenclaturen later): appropriateappropriate.. WitWithh ssoo attractivattractivee a guidguidee wwee cacann onlonlyy awaiawaitt gemmologistwith some care.s nee dTho to approacse who h areamphibol also seriouse nomenclatur minerale ththee arrivaarrivall ooff ththee exhibitioexhibitionn itselitselff witwithh considerableconsiderable witcollectorsh som ewill care do. Thoswelle towh buyo ar ae copyalso -seriouit is s fortunatemineral anticipationanticipation.. ThThee pricpricee iiss bbyy nnoo meanmeanss unreasonablunreasonablee foforr a collectorthough sof wilcoursel do welinevitablel to bu ythat a copthe y complete- it is fortunat work ise boobookk produceproducedd ttoo ssoo highighh aa standardstandard.. M.O'DM.O'D.. though of course inevitable that the complete work is © GemmologicaGemmologicall AssociatioAssociationn anandd GeGemm TestinTestingg LaboratorLaboratoryy ooff GreaGreatt BritaiBritainn ISSNISSN:: 1355-45651355^565 Proceedings of the Gemmological Association and Gem Testing Laboratory of Great Britain and Notices

OBITUARY Phoenicia Hotel. Apart from retailing, he was closely involved with the design and manufacture Joseph Azzopardi, FGA (D. 1966), died on of jewellery and with valuations. 19 September 1997 at his home in Nantwich, Cheshire, aged 72 years. Joe was born in Malta and By 1984 health problems led Joe to decide to attended St. Aloysius College until he was drafted sell the business and retire with his wife to into the British Army for the last two years of the England where his two children had settled. Second World War. Joe became an active member of the North West On demobilization Joe joined the family Branch of the GAGTL and served as both Secretary business, The Sterling Jewellers (established as and Treasurer for six years. He was very much D. Azzopardi and Bros, in 1896) in Kingsway, admired and respected by Branch members and is Valletta. By 1971 he had become sole owner of the sadly missed. He was also a Registered Valuer with company and later opened a branch at the the National Association of Goldsmiths. 49

GIFTS TO THE ASSOCIATION High Pressure Diamond Optics, Inc., Tucson, Arizona, USA, for two 'busted' type Ha The Association is most grateful to the anvil diamonds. following for their gifts for research and teaching purposes: Dr J. Kanis, Veitsrodt, Germany, for a selection of cut stones from South Africa, Professor A. Chikayama, Japan, for a Zimbabwe, Zambia and Tanzania, including selection of I-pearls - imitation pearls made in emerald, tourmaline, topaz, iolite, citrine and Japan. tsavorite. Luella Woods Dykhuis, Tucson, Arizona, Marcia Lanyon Ltd, London, for 357 various USA, for a copy of the November 1978 issue of specimens including opal, garnet, ruby, the Lapidary Journal, Beautiful Queensland opals by sapphire (including a pinkish sapphire), Lee Cram, eight pieces of quartz and also various peridot, topaz and spinel. packs of stones including emerald, sodalite, tourmaline, labradorite, fluorite and ruby. Mrs C.M. Ou Yang, Hong Kong, for five examples of B-jade, typical of material currently Mr John R. Fuhrbach, FGA, Amarillo, Texas, on the market. USA, for specimens of cut and rough bytownite from New Mexico, USA, and for 45 items of Evelyn Ripley, Stockton, Cleveland, for 41 rough and polished gems - a wide range of stones including ruby, spinel, quartz, jet, opal material from worldwide sources. and turquoise. David Hargreaves, The Silurian Co. Ltd, Prashant R. Suchak of Suchak Mineral Kingston-upon-Thames, for a rough ruby from Resources Ltd, Arusha, Tanzania, for two Malawi. tanzanite crystals.

© Gemmological Association and Gem Testing Laboratory of Great Britain ISSN: 1355-4565 BEQUESTBEQUEST OnOn 3 DecemberDecember atat thethe GemGem TutorialTutorial Centre,Centre, ProfessorProfessor AndrewAndrew RankinRankin ofof KingstonKingston UniversityUniversity WWee areare pleasedpleased ttoo announceannounce thathatt thethe GAGTLGAGTL gavegave a lecturelecture entitledentitled Fluid inclusioinclusions:ns: solution solutionss for for hashas recentlyrecently benefitebenefitedd fromfrom a bequbequesest mademade byby mineral g genesisenesis and and gem gem identification identification.. MrsMrs JeanneJeanne MaudeMaude HerbertHerbert Towers,Towers, daughterdaughter ooff thethe latelate HerbertHerbert Smith,Smith, CBE,, MA,MA, D.Sc.,D.Sc, whowho waswas PresidentPresident ofof ththee GemmologicalGemmological AssociationAssociation fromfrom MidlandsMidlands BranchBranch 19421942 toto 1953.1953 . OnOn 3131 OctoberOctober atat thethe DiscoveryDiscovery Centre,Centre, 7777 Vyse Vyse MrsMrs TowersTowers passedpassed awayaway onon 1616 DecemberDecember 19919966 Street, Birmingham,Birmingham, BrianBrian JacksonJackson ofof ththee NationalNational andand inin herher willwill leftleft ththee AssociationAssociation allall herher interestinterest MuseumsMuseums ofof ScotlandScotland gavegave anan illustrateillustratedd talktalk inin thethe copyrightcopyright ofof ththee boobookk GGemstonesemstones written writte nby b y entitledentitled The ssapphiresapphires of ofScotland Scotland.. herher fatherfather inin 19121912 asas thethe originaloriginal setset ofof coursecourse notesnotes On 16 November a Practical Gemmology forfor thethe firstfirst gemmologygemmology coursecourse inin ththee world.world. IInn On 16 November a Practical Gemmology TrainingTraining Day wawass held.held. additionaddition sheshe leftleft ththee AssociatioAssociationn oneone halhalff ofof thethe residuarresiduaryy estate; ofof whichwhich ththee AssenAssentt ofof copyrightcopyright OnOn 2288 NovemberNovember atat ththee DiscoverDiscoveryy Centre, inin GemGemstonesstones and and a asum sum of o £1f £166882 88 2has ha alreads already beeny bee n DaviDavidd CallaghanCallaghan gavegave anan illustratedillustrated taltalkk oonn Opals.. receivedreceived.. AAnn unquantifieunquantifiedd balancbalancee wilwilll follofolloww aatt a OnOn 6 DecembeDecemberr ththee Branch'Branch's 45t45thh AnnivAnniversarersaryy latelaterr datedate.. DinneDinnerr wawas helheldd atat BarnBarntt Green.Green. AAtt a recenrecentt meetinmeetingg ooff ththee CouncilCouncil ooff ManagemenManagementt iitt wawass decidedecidedd ttoo placplacee ththee moneymoney fromfrom thithiss bequesbequestt intintoo ththee GAGTGAGTLL PropertPropertyy FundFund NortNorthh WesWestt BrancBranchh whichwhich,, togethetogetherr witwithh otheotherr moniemoniess receivedreceived,, wilwilll OOnn 1717 SeptembeSeptemberr aatt ChurchChurch HouseHouse,, HanoverHanover hopefullhopefullyy enablenablee ththee organisatioorganisationn ttoo acquiracquiree a Street,Street, LiverpooLiverpooll 1,1, IrenIrenee KnighKnightt gavgavee a taltalkk oonn buildinbuildingg suitablsuitablee ttoo houshousee alalll ititss activitiesactivities andand jewellery, relatinrelatingg ttoo heherr visivisitt ttoo BeijingBeijing,, andand providprovidee ththee standarstandardd ooff serviceservice rightfullrightfullyy expectedexpected StanleyStanley HillHill spokespoke onon cloisonncloisonnee enameenamell work.work. by ththee membershipmembership.. OOnn 1515 OctoberOctober atat ChurchChurch HouseHouse,, DrDr JackJack OgdenOgden,, TToo develodevelopp ththee GAGTGAGTLL accommodatioaccommodationn forfor ChieChieff ExecutivExecutivee ooff ththee NAG, gave a taltalkk oonn mattermatterss 5050 teachingteaching,, researcresearchh anandd gem-testingem-testingg serviceservicess iiss highighh concerninconcerningg ththee jewellerjewelleryy trade.. oonn ththee Council'Council'ss lislistt ooff prioritieprioritiess anandd thetheyy woulwouldd OOnn 1199 NovembeNovemberr ththee AnnuaAnnuall GeneraGenerall MeetinMeetingg encouragencouragee membermemberss anandd well-wisherwell-wisherss ttoo consideconsiderr ooff ththee BrancBranchh wawass helheldd aatt whicwhichh IrenIrenee KnighKnightt wawass rememberinrememberingg th thee GAGTGAGTLL whewhenn planninplanningg theitheirr re-electere-electedd ChairmanChairman,, anandd DeannDeannaa Brady anandd DDrr estatesestates;; whethewhetherr iitt bbee iinn ththe forformm ooff gegemm materialsmaterials,, JohJohnn FrankFrankss electeelectedd SecretarSecretaryy anandd TreaTreasuresurerr booksbooks,, oorr a financiafinanciall donatiodonationn ttoo eitheeitherr ouourr respectively.. researcresearchh oorr buildinbuildingg funds,, thesthesee araree alwayalwayss mucmuchh appreciatedappreciated.. ScottisScottishh BrancBranchh MEMBERSMEMBERS'' MEETINGMEETINGSS OOnn 2200 OctobeOctoberr aatt ththee RoyaRoyall BritisBritishh Hotel, LondoLondonn 'Princess Street,, Edinburgh,, BriaBriann DunDunnn gavgavee a taltalkk entitleentitledd GemsGems -- aa valuer valuer's's hea heavenven or hell?or hell? OOnn 2244 SeptembeSeptemberr aatt ththee GeGemm TutoriaTutoriall Centre,, 2277 GrevillGrevillee Street ,, LondoLondonn EC1EClNN 8SU,, OOnn 2200 NovembeNovemberr aatt ththee RoyaRoyall BritisBritishh HoteHotell ProfessoProfessorr RoberRobertt AA.. HowieHowie,, PresidenPresidentt ooff ththee FreFredd WoodwarWoodwardd gavgavee a taltalkk entitleentitledd Scottish RiverRiver GAGTLGAGTL,, gavgavee a taltalkk entitleentitledd Rock-formingRock-forming Minerals Minerals Pearls.Pearls. - the writingwriting of of a a classic classic.. OOnn 1155 OctobeOctoberr aatt ththee GeGemm TutoriaTutoriall CentreCentre,, PRESENTATION OF AWARDS LynnLynnee BartletBartlettt gavgavee aann illustrateillustratedd lecturlecturee entitleentitledd PRESENTATION OF AWARDS From sparkssparks to tosparkle sparkle - a- bria ebrieff history history of the of usethe ofuse of ThThee PresentatioPresentationn ooff AwardAwardss gainegainedd iinn ththee 19919977 marcasite/pyrites.marcasite/pyrites. examinationexaminationss wawass helheldd aatt GoldsmithsGoldsmiths'7 Hall,, FosteFosterr \ OOnn 9 NovembeNovemberr aatt ththee BarbicaBarbicann Centre,, Lane,, LondoLondonn EC2, oonn MondayMonday,, 1100 NovemberNovember.. TheThe LondoLondonn EC2EC2,, ththee GAGTGAGTLL AnnuaAnnuall ConferencConferencee was PresidentPresident,, ProfessoProfessorr R.ARA.. Howie,, presidepresidedd anandd helheldd oonn ththee themthemee Collectors'Collectors' Gems.Gems. This Thi s waswa s welcomewelcomedd thosthosee presentpresent.. followefollowedd oonn 1100 NovembeNovemberr bbyy a tritripp ttoo ththee NaturaNaturall ProfessoProfessorr HowiHowiee relaterelatedd a recenrecentt probleproblemm hhee HistorHistoryy Museum, SoutSouthh KensingtonKensington.. A fulfulll reporreportt hahadd encounteredencountered:: ''AA researcresearchh studenstudentt frofromm ooff ththee ConferencConferencee wilwilll bbee publishepublishedd iinn ththee March overseasoverseas,, nonoww studyinstudyingg iinn BritaiBritainn aa subjecsubjectt outsidoutsidee issueissue ofof Gem Gem and and Jewellen) Jewellery News. News. ththee eartearthh sciencessciences,, wrotwrotee askinaskingg mmee ttoo helhelpp aa

/r. Gemm.,Gemm" 11998,26,1,49-58998, 26, 1, 49- 58 FORTHCOMINGFORTHCOMING EVENTEVENTSS 19981998 3030 JanuarJanuaryy MidlandMidlandss Branch.Branch. BringBring andand BuyBuy Sale;Sale; PracticalPractical GemmologyGemmology Quiz.Quiz. 1818 FebruarFebruaryy London.London. CollectingCollecting gemstonesgemstones inin ScotlandScotland.. BriaBriann Jackson.Jackson. 2222 FebruaryFebruary MidlandsMidlands Branch.Branch. GemGem ClubClub - microscopymicroscopy inin allall itsits aspectsaspects.. 2727 FebruaryFebruary MidlandsMidlands BranchBranch.. ChineseChinese andand JapanesJapanesee pearlspearls.. MichaelMichael Houghton.Houghton. 6--86-8 MarcMarchh FieldField triptrip toto WhitbyWhitby 1818 MarchMarch LondonLondon.. FiredFired witwithh enthusiasm:enthusiasm: ththee earlyearly historyhistory ofof enamel.enamel. DrDr JacJackk Ogden. Ogden. 22 March Midlands Branch. Gem Club - Gemstones. Professor RA. Howie 22 March Midlands Branch. Gem Club - Gemstones. Professor R.A. Howie 27 March Midlands Branch. Dr Jack Ogden. 27 March Midlands Branch. Dr Jack Ogden. 19 April Midlands Branch. Gem Club - Bragging pieces; collectors' stones 19 April Midlands Branch. Gem Club - Bragging pieces; collectors' stones 19-25 April Trip to Idar-Oberstein, Germany 19-25 April Trip to Idar-Oberstein, Germany 22 April London. Pearls - a fashion opportunity. Christianne Douglas 22 April London. Pearls - a fashion opportunity. Christianne Douglas 24 April Midlands Branch. AGM followed by a mosaic of gemmological 24 April tesseraMidland s Branch. AGM followed by a mosaic of gemmological

26 April tesserMidlandsa Branch. Diploma pre-examination seminar 5151 326 May Apri l MidlandMidlandss BranchBranch.. DiplomPreliminarya pre-examinatio pre-examinationn semina seminarr 313 Ma Mayy London.Midland sThe Branch gemstone. Preliminar collectionsy pre-examinatio of the GAGTLn semina r 1713 MayMay MidlandsLondon. Th Branch.e gems tonGeme collection Club - s 'Blackof the GAGTpearls'L of Guyana, James 17 May Gosling,Midland ands Branch The opals. Ge mof CooberClub - Pedy,'Blac kGwyn pearls Green' of Guyana, James 29 June GoslingLondon., anAnnuald The opalGenerals of Coobe Meetingr Pedy followed, Gwyn Greeby nthe Reunion of 29 June MembersLondon. andAnnua a Bringl Genera and lBuy Meetin Sale g followed by the Reunion of Members and a Bring and Buy Sale 8 JulyJuly London.London. TheThe evolutionevolution ofof GeorgianGeorgian andand VictorianVictorian jewellery.jewellery. JohnJohn BenjamiBenjaminn ForFor furtherfurther informationinformation onon ththee aboveabove eventsevents contact:contact: LondonLondon:: MarMaryy BurlanBurlandd onon 017140433340171 404 3334 MidlandsMidlands Branch:Branch: GwynGwyn GreenGreen onon 01210121 445445 53553599 NorthNorth WesWestt Branch:Branch: IreneIrene KnightKnight onon 01510151 9243103924 3103 ScottishScottish Branch:Branch: JoannJoannaa ThomsonThomson onon 0172172293601721 722936 GAGTLGAGTL WEWEBB SITSITEE ForFor up-to-the-minuteup-to-the-minute informatioinformationn onon GAGTLGAGTL eventsevents andand workshopsworkshops visitvisit ourour wewebb sitesite onon www.gagtl.ac.uklgagtlwww.gagtl.ac.uk/gagtl

Forthcoming Events Tou'Fourr specimensspecimens eventuallyeventually arrivedarrived anandd a quickquick glanceglance showedshowed thethemm ttoo bbee virtuallvirtuallyy colourlesscolourless crystacrystall fragmentsfragments,, somsomee 2 ccmm across,across, ofof calcite,calcite, fluoritefluorite anandd quartquartzz (two(two)) - bubutt hohoww ttoo provprovee itit toto hihiss satisfactionsatisfaction?? BeinBeingg retireretiredd anandd livinlivingg iinn ruralrural DerbyshireDerbyshire,, I havhavee nnoo refractometerrefractometer,, spectroscope,spectroscope, X-raX-rayy facilitiesfacilities oror eveneven microscopmicroscopee - jusjustt a loupeloupe andand mmyy witswits!! I havhavee nnoo hardneshardnesss sesett aass suchsuch,, butbut hardneshardnesss wawass ththee answer,answer, anandd I wawass soonsoon ablablee toto showshow thathatt ththee calcitecalcite hahass perfecperfectt cleavagecleavage andand waswas scratchescratchedd bbyy knowknownn fluoritefluorite;; ththee fluoritefluorite hahadd a ververyy fainfaintt purplispurplishh colour,colour, a goodgood cleavagecleavage andand wawass scratchescratchedd bbyy crystalcrystalss ooff apatiteapatite anandd quartquartzz andand ththee twtwoo quartzquartz piecepiecess werweree readilreadilyy scratchescratchedd byby topatopazz andand rubyruby.. I alsoalso notenotedd thathatt oneone quartzquartz displayeddisplayed growtgrowthh trigontrigonss onon ononee face:face: ververyy properproper forfor a trigonatrigonall mineralmineral,, bubutt I wondewonderr whethewhetherr mymy overseasoverseas enquireenquirerr hahadd growtgrowthh trigontrigonss oonn diamonddiamond iinn hihiss mindmind?? I wrotwrotee ououtt mmyy reporreportt anandd havhavee heardheard Dr Roger Harding, Professor Chen Zhonghui,Zhonghui, nnoo mormoree - bubutt aass ththee addressaddress onon hihiss notepapenotepaperr waswas Terry Davidson, Eric Bruton and (seated) thathatt ooff a NationaNationall MineraMinerall ExplorationExploration Professor Robert Howie at the Presentation ofof ProgrammeProgramme,, I diddid wondewonderr asas ttoo hihiss background!background! Awards. 'InIn anan incidentincident fromfrom earlieearlierr yearsyears,, whewhenn I waswas responsiblresponsiblee foforr assessinassessingg studentstudentss foforr admissionadmission toto colleaguecolleague iinn hihiss homhomee countrycountry whwhoo needeneededd somesome ththee GeologyGeology DepartmenDepartmentt atat KingKingss College,College, a crystacrystall samplessamples ttoo bbee reliablreliablyy identified.identified. HisHis candidatcandidatee bouncebouncedd inin andand announceannouncedd thathatt hhee hadhad colleagucolleaguee hahadd alreadalreadyy trietriedd a NationaNationall MuseuMuseumm inin a schemescheme he'dhe'd perfectedperfected forfor identifyingidentifying minerals,minerals, 5252 LondonLondon anandd ththee X-raX-rayy LaboratorLaboratoryy ofof a MidlandsMidlands dididd I wanwantt ttoo heahearr it?it? I toltoldd hihimm "No,"No, bubutt havhavee a gogo UniversitUniversityy bubutt feltfelt unhappunhappyy witwithh ththee resultsresults.. MyMy aatt identifyingidentifying thithiss specimen,"specimen," andand I passepassedd acrossacross namnamee hahadd beebeenn recommenderecommendedd aass someonesomeone ooff a translucenttranslucent octahedraloctahedral crystalcrystal ofof diamond.diamond. scientifiscientificc integritintegrityy whoswhosee opinionopinion hhee couldcould trust.trust. "Fluorite,"Fluorite,"" hhee said.said. I passepassedd acrosacrosss a Mohs'Mohs' hardneshardnesss setset andand askedasked hihimm ttoo testestt itit:: hhee soonsoon found that it scratched apatite, feldspar, quartz Preliminary Trade PrizePrize winner,winner, SimonSimon Millard,Millard, found that it scratched apatite, feldspar, quartz and topaz - at which point I stopped him, and said receiving his prize fromfrom Professor Chen and topaz - at which point I stopped him, and said "Any comment?" "Hard fluorite!" was his Zhonghui. "Any comment?" "Hard fluorite!" was his astonishingastonishing replyreply!! TheThe moramorall ofof thesthesee twotwo incidentincidentss isis thathatt (1)(1) yoyouu shoulshouldd puputt youyourr faitfaithh inin someonesomeone ofof knowknownn integrityintegrity anandd (2(2)) yoyouu musmustt trusttrust youyourr results.results. 'Bu'Butt whawhatt isis ththee relevancrelevancee ttoo tonight'stonight's occasion?occasion? SimplSimplyy thathatt youyou,, ththee awardaward winners,winners, havhavee indeedindeed puputt youyourr faitfaithh inin ththee integritintegrityy ooff thethe ExaminerExaminerss appointeappointedd bbyy ththee GemmologicalGemmological AssociationAssociation,, whicwhichh iiss whwhyy yoyouu havhavee comcomee fromfrom allall overover ththee worlworldd ttoo sitsit ourour examinations.examinations. NoNoww putput faithfaith iinn theitheirr judgemenjudgementt andand gogo fortforthh withwith confidenceconfidence ttoo begibeginn ttoo developdevelop youyourr careercareerss anandd toto profiprofitt fromfrom youyourr growinggrowing experienceexperience inin ththee ever­ever- increasinincreasingg complexitiescomplexities ooff reareall gemmology.gemmology 'I'Inn JanuarJanuaryy anandd JunJunee 1997,1997, 10491049 studentsstudents entereenteredd ththee PreliminaryPreliminary,, DiplomDiplomaa anandd GemGem DiamonDiamondd examinations.examinations. A totatotall ooff 189189 studentsstudents passepassedd ththee DiplomDiplomaa examinatioexaminationn andand thetheyy camecame frofromm 2211 countries,countries, inin alalll fivfivee continents.continents. HereHere tonightonightt wwee agaiagainn havhavee aann internationalinternational gatheringgathering

JJ.. Gemm.,Cemm., 1998, 26,1,26, 1, 49-5849-58 witwithh successfusuccessfull candidatecandidatess frofromm aass fafarr awaawayy aass CanadaCanada,, Japan Japan,, MyanmarMyanmar, , SrSrii LankLankaa anandd ththee USAUSA,, aass welwelll aass frofromm FinlandFinland,, GreeceGreece,, ThThee NetherlandNetherlandss anandd SwedenSweden.. Eighty-onEighty-onee studentstudentss passepassedd ththee GeGemm DiamonDiamondd ExaminatioExaminationn anandd althougalthoughh thithiss iiss nonott quitquitee . aass widespreawidespreadd aass ththee gemmologgemmologyy examexam,, thertheree werweree successfusuccessfull candidatecandidatess thithiss yeayearr frofromm ChinaChina,, CyprusCyprus,, HonHongg KonKongg anandd IndiaIndia:/ ProfessoProfessorr HowiHowiee introduceintroducedd ProfessoProfessorr CheChenn ZhonghuZhonghuii frofromm ththee ChinChinaa UniversitUniversityy ooff GeoscienceGeosciencess iinn WuhaWuhann whwhoo presentepresentedd ththee awardsawards.. ProfessoProfessorr HowiHowiee thethenn callecalledd oonn EriEricc Bruton,, immediatimmediatee paspastt PresidenPresidentt ooff ththee AssociationAssociation,, ttoo presenpresentt ththee BrutoBrutonn MedaMedall ttoo MisMisss RitRitaa TsanTsangg WaWaii YYii ooff HonHongg KongKong,, ththee firsfirstt occasiooccasionn oonn whicwhichh thithiss medamedall hahadd beebeenn awardedawarded.. ProfessoProfessorr CheChenn deliveredeliveredd hihiss addresaddresss (se(seee belowbelow)) anandd aa votvotee ooff thankthankss ttoo ProfessoProfessorr CheChenn wawass proposeproposedd bbyy TerrTerryy DavidsoDavidsonn whwhoo expresseexpressedd ththee EricEric BrutonBruton presentingpresenting thethe BrutonBruton MedalMedal toto hophopee thathatt ththee GAGTGAGTLL anandd ththee ChinChinaa UniversitUniversityy ooff RitaRita Tsang.Tsang. GeoscienceGeosciencess woulwouldd continucontinuee ttoo worworkk togethetogetherr intintoo ththee twenty-firstwenty-firstt centurycentury.. IInn conclusionconclusion,, ProfessoProfessorr HowiHowiee thankethankedd ththee anandd KeKenn ScarratScarrattt whwhoo offereofferedd uuss mucmuchh helhelpp iinn ththee GoldsmithsGoldsmiths'7 CompanCompanyy foforr allowinallowingg ththee GAGTGAGTLL ttoo initiainitiall stagestagess ooff ouourr ATCATe.. TheTheyy onconcee gavgavee uuss thithiss holholdd ththee ceremonceremonyy aatt ththee HallHall.. metaphometaphorr thathatt ththee BritisBritishh teacherteacherss araree liklikee aa wewett toweltowel;; thetheyy expecteexpectedd ouourr studentstudentss ttoo wrinwringg ououtt thithiss wewett toweltowel.. OuOurr studentstudentss dididd nonott disappoindisappointt thesthesee AddresAddresss bbyy BritisBritishh teachersteachers!! ThThee sincersinceree helhelpp frofromm thesthesee BritisBritishh 533^/53 ProfessoProfessorr CheChenn ZhonghuZhonghuii teacherteacherss hahass lailaidd aa solisolidd foundatiofoundationn foforr ththee smootsmoothh developmendevelopmentt ooff ouourr ATATCC sincsincee thenthen.. IInn 19931993,, aa neneww T'I aamm ververyy delightedelightedd ttoo attenattendd today'today'ss GeGemm DiamonDiamondd CoursCoursee openeopenedd iinn ouourr UniversitUniversityy PresentatioPresentationn ooff AwardAwardss 19971997.. FirsFirstt ooff allall,, II woulwouldd witwithh ththee helhelpp ooff EriEricc EmmsEmms.. ThiThiss iiss alsalsoo ththee firsfirstt iinn liklikee ttoo shoshoww mmyy gratitudgratitudee ttoo ththee GemmologicaGemmologicall ththee ChinesChinesee mainlandmainland. . SincSincee ththee establishmenestablishmentt ooff AssociatioAssociationn ooff GreaGreatt BritaiBritainn whicwhichh hahass kindlkindlyy ththee ATCATC iinn ouourr UniversityUniverSity,, 151555 studentstudentss havhavee inviteinvitedd mmyy wifewife,, ProfessoProfessorr YanYan,, anandd myselmyselff ttoo papayy obtaineobtainedd FGFGAA DiplomaDiplomass anandd 6644 studentstudentss havhavee thithiss visivisitt ttoo youyourr beautifubeautifull countrycountry.. II aamm alsalsoo obtaineobtainedd DGDCAA DiplomasDiplomas,, ooff whowhomm 1155 studentstudentss honourehonouredd ttoo presenpresentt ththee DiplomaDiplomass ttoo thosthosee whwhoo havhavee wowonn ththee certificatcertificatee witwithh distinctiondistinction,, anandd fivfivee havhavee passepassedd successfullsuccessfullyy ththee examinationexaminationss thithiss studentstudentss havhavee wowonn prizesprizes.. ThThee studentstudentss iinn ouourr ATATCC yearyear.. II woulwouldd liklikee ttoo extenextendd mmyy warmeswarmestt comcomee frofromm almosalmostt alalll ththee provincesprovinces,, autonomouautonomouss congratulationcongratulationss ttoo ththee diligendiligentt studentstudentss whwhoo havhavee regionregionss anandd municipalitiemunicipalitiess iinn ChinaChina.. ThThee graduategraduatess obtaineobtainedd ththee treasuretreasuredd DiplomasDiplomas,, especiallespeciallyy ttoo witwithh FGFGAA DiplomaDiplomass havhavee establisheestablishedd ththee firsfirstt thosthosee whwhoo havhavee obtaineobtainedd prizeprizess thithiss yearyear.. gemmologicagemmologicall testintestingg laboratorielaboratoriess iinn manmanyy Th'Thee GemmologicaGemmologicall InstituteInstitute,, ChinChinaa UniversitUniversityy differendifferentt partpartss ooff ChinaChina.. IInn thithiss sensesense,, thetheyy havhavee ooff GeosciencesGeosciences,, startestartedd ititss co-operatioco-operationn witwithh ththee playeplayedd aann importanimportantt rolrolee iinn ththee promotiopromotionn ooff ththee GemmologicaGemmologicall AssociatioAssociationn ooff GreaGreatt BritaiBritainn iinn 19881988.. gemmologgemmologyy anandd jewellerjewelleryy industrindustryy iinn ChinaChina.. ThThee TodaTodayy iiss ththee tenttenthh yeayearr ooff ouourr friendlfriendlyy co-operationco-operation.. achievementachievementss ooff thesthesee graduategraduatess frofromm ouourr ATATCC IInn ththee sprinspringg ooff 19881988,, AlaAlann JobbinJobbinss anandd DDrr JamiJamiee havhavee alsalsoo madmadee ththee FGFGAA anandd DGDCAA DiplomaDiplomass bbyy NelsoNelsonn paipaidd theitheirr firsfirstt visivisitt ttoo ouourr UniversitUniversityy aatt ththee GemmologicaGemmologicall AssociatioAssociationn ooff GreaGreatt BritaiBritainn WuhanWuhan,, ChinaChina.. AfteAfterr ththee friendlfriendlyy negotiationnegotiation,, botbothh knowknownn alalll oveoverr China.. ThThee experiencexperiencee witwithh ththee partiepartiess workeworkedd togethetogetherr anandd eventualleventuallyy madmadee aann FGFGAA anandd educatioeducationn iinn ththee GemmologicaGemmologicall InstitutInstitutee agreemenagreementt thathatt a neneww AllieAlliedd TeachinTeachingg CentrCentree ofof ourour University University qualifies qualifies us to us enrol to enrolthe undergraduate the under­ undeunderr ththee GemmologicaGemmologicall AssociatioAssociationn ooff GreaGreatt graduate studentstudentss iinn gemmologgemmologyy aatt ouourr UniversityUniversity.. BritaiBritainn bbee establisheestablishedd iinn ouourr University.. ThiThiss iiss ththee IInn additionaddition,, ththee GemmologicaGemmologicall InstitutInstitutee hahass alreadalreadyy firsfirstt ATC iinn ththee ChinesChinesee mainlandmainland,, anandd alsalsoo ththee openeopenedd variouvariouss short-tershort-termm trainintrainingg programmeprogrammess iinn firsfirstt ATATCC iinn ththee ChinesChinesee languaglanguagee iinn ththee world.. WWee gemmologgemmologyy anandd ththee gegemm diamondiamondd coursecourse.. AroundAround wilwilll neveneverr forgeforgett AlaAlann JobbinsJobbins,, DDrr JamiJamiee NelsoNelsonn 20002000 personspersons from fromthe gem the and jewellerygem and jewellery

ProceedingsProceedings and Notices PRESENTATIONPRESENTATION ININ WUHAN,WUHAN, CHINACHINA A presentationpresentation ofof gemmologicalgemmological awards,awards, includingincluding thosethose ofof thethe GAGTL,GAGTL, waswas heldheld atat thethe GemmologicalGemmological Institute,Institute, ChinaChina UniversityUniversity ooff Geosciences,Geosciences, Wuhan,Wuhan, onon 2222 NovemberNovember 1997,1997, duringduring thethe Institute'sInstitute's AnnualAnnual Conference.. StephenStephen KennedyKennedy ofof thethe GAGTLGAGTL gavegave a lecturelecture entitledentitled 'PearlTearl FishingFishing andand PearlPearl Identification'Identification' atat thethe ConferenceConference andand presentedpresented ththee Association'sAssociation's DiplomasDiplomas andand alsoalso thethe TullyTully MedalMedal whicwhichh hadhad beenbeen awardedawarded ttoo MsMs LiLi LipingLiping ofof Wuhan.

FEEGFEEG EXAMINATIONEXAMINATION REMINDERREMINDER - FEEFEEGG applicatioapplicationn formformss areare availableavailable frofromm LomeLome StatherStather atat thethe GemGem TutorialTutorial Centre,Centre, GAGTL.GAGTL. AlAlll applicantapplicantss areare reminderemindedd thatthat thetheyy musmustt alreadyalready holdhold a gemmologicagemmologicall DiplomaDiploma frofromm eitheeitherr GAGTGAGTLL oror oneone ooff ththee otheotherr membermember organizations.organizations. CandidatesCandidates shouldshould notnotee thathatt thertheree araree nnoo notenotess oorr otheotherr coursecourse materialmaterialss availableavailable witwithh thithiss exaexamm bubutt thathatt refresherefresherr coursecoursess coulcouldd bbee Stephen Kennedy presenting the Tully Prize to arrangearrangedd witwithh sufficiensufficientt noticenotice.. Ms Li Liping. ExaExamm datedate - 7 JulyJuly 19981998 FinaFinall entrentryy datedate - 3311 MayMay 19981998 5454 industrindustryy havhavee beebeenn trainetrainedd iinn thesthesee short-termshort-term programmesprogrammes.. BecausBecausee ooff ouourr persistenpersistentt effortsefforts THTHEE 26T26THH INTERNATIONALINTERNATIONAL anandd excellenexcellentt achievementachievementss iinn gemmologicalgemmological educatioeducationn iinn ChinaChina,, ththee GemmologicaGemmologicall InstituteInstitute GEMMOLOGICAGEMMOLOGICALL ooff ouourr UniversitUniversityy hahass wowonn ththee firsfirstt prizprizee iinn CONFERENCCONFERENCEE (IGC(IGC)) educatioeducationn aatt ththee provinciaprovinciall levellevel,, anandd ththee seconsecondd ThThee conferencconferencee iiss bienniabienniall anandd wawass helheldd iinn prizprizee iinn educatioeducationn aatt ththee nationanationall levelevell iinn 19971997.. September-OctobeSeptember-Octoberr 19971997,, aatt ththee HunsruckHunsruck ThiThiss hahass fullfullyy showeshowedd thathatt whawhatt wwee havhavee donedone FerienparFerienparkk HambachtalHambachtal,, a conferencconferencee anandd leisureleisure hahass beebeenn positivelpositivelyy acknowledgeacknowledgedd bbyy ththee centrcentree outsidoutsidee Idar-ObersteinIdar-Oberstein,, GermanyGermany.. IItt wawass relevanrelevantt authoritieauthoritiess anandd bbyy ththee publipublicc iinn China.China. attendeattendedd bbyy 4444 delegatedelegatess anandd 1100 observerobserverss fromfrom ThThee firsfirstt AllieAlliedd TeachinTeachingg CentrCentree iinn ththee 2255 countries.. ThThee lecturelecturess listelistedd belobeloww werweree ChinesChinesee languaglanguagee iinn ouourr universituniversityy resulteresultedd iinn deliveredeliveredd oonn 2299 SeptembeSeptemberr ttoo 2 OctobeOctoberr anandd ththee presenpresentt tetenn ATCATCss iinn ththee ChinesChinesee languaglanguagee iinn coverecoveredd a widwidee rangrangee ooff topicstopics;; a collectiocollectionn ooff ththee ChinesChinesee mainlandmainland,, HonHongg KonKongg anandd TaiwanTaiwan,, abstractabstractss ooff ththee talktalkss wawass provided.. anandd thithiss yeayearr alsalsoo a neneww ATATeC iinn SingaporeSingapore.. AAtt ththee IGIGCC businesbusinesss meetinmeetingg helheldd oonn 2 OctoberOctober,, ththee placplacee ooff ththee nexnextt meetinmeetingg iinn 19919999 wawass decidedecidedd LookinLookingg bacbackk oveoverr ththee paspastt tetenn yearsyears,, wwee havhavee anandd DDrr PanjikaPanjikarr ooff ththee GemmologicaGemmologicall InstitutInstitutee ooff enjoyeenjoyedd ouourr friendlfriendlyy co-operatioco-operationn witwithh ththee IndiaIndia,, BombayBombay,, wilwilll hoshostt ththee 27t27thh IGCIGC.. ThankThankss GemmologicaGemmologicall AssociatioAssociationn ooff GreaGreatt BritainBritain.. OnOnee werweree expresseexpressedd ttoo ProfessoProfessorr BankBank,, hihiss colleaguecolleaguess majomajorr purpospurposee ooff ouourr presenpresentt visivisitt ttoo youyourr anandd familfamilyy foforr a superblsuperblyy organizeorganizedd meetinmeetingg anandd AssociatioAssociationn iiss ttoo makmakee a joinjointt researcresearchh witwithh ththee programmprogrammee ooff events.. GemmologicaGemmologicall AssociatioAssociationn ooff GreaGreatt BritaiBritainn intintoo ththee enhancemenenhancementt anandd developmendevelopmentt ooff ouourr OOnn 3 October,, ththee finafinall dadayy ooff ththee conferenceconference friendlfriendlyy co-operatioco-operationn witwithh ththee AssociatioAssociationn anandd wawass spenspentt oonn a fielfieldd tritripp ttoo ththee EifelEifel,, north-wesnorth-westt ooff intintoo ththee expansioexpansionn ooff ouourr fielfieldd ooff co-operationco-operation.. II Idar-ObersteinIdar-Oberstein,, ttoo searcsearchh foforr peridotperidot,, sanidinsanidinee anandd aamm confidenconfidentt thathatt mormoree fruitfruitss wilwilll resulresultt frofromm ouourr hauynhauynee iinn ththee lavalavass anandd tufftuffss -- partpartss onlonlyy 1133 000000 sincersinceree co-operationco-operation.. II alsalsoo sincerelsincerelyy hophopee thathatt yearyearss ololdd (som(somee saisaidd thetheyy werweree stilstilll warwarmm bubutt thathatt ththee GemmologicaGemmologicall AssociatioAssociationn ooff GreaGreatt BritaiBritainn wawass jusjustt ththee autumautumnn sunshine!)sunshine!).. wilwilll makmakee aa greategreaterr developmendevelopmentt iinn ththee future.'future/ R.RR.R.. HardinHardingg

JJ.. Gemm.,Gemm., 11998,26,1,49-58998, 26, 1, 49-58 OraOrall presentationpresentationss (senio(seniorr authorauthorss onlonlyy listedlisted)) BalitskyBalitsky, , V.SV.S.. ThThee firsfirstt commerciacommerciall synthetisyntheticc MiyataMiyata,, TT.. RelatioRelationn betweebetweenn surfacsurfacee ametrinametrinee frofromm RussiRussiaa anandd ititss gemmologicagemmologicall microtopographmicrotopographss anandd growtgrowthh conditioconditionn ooff characteristiccharacteristicss quartquartzz crystalcrystalss BosshartBosshart, ,G G.. DiamonDiamondd inclusion inclusionss i nin corunducorundumm OOuu YangYang,, CMCM.. Definition-nomenclatureDefinition-nomenclature­- BrownBrown, ,G G.. AAnn opa opall nomenclatur nomenclaturee classificatioclassificationn ooff jad jadee Panjikar, J. New gem deposits from India ChikayamaChikayama,, AA.. ThThee imitatioimitationn pearpearll industrindustryy inin Panjikar, J. New gem deposits from India Pienaar, H.s. A fresh look at 'Kauri gum' from JapaJapann Pienaar, H.S. A fresh look at 'Kauri gum' from North Island, New Zealand DereppeDereppe,, J.MJ.M. . ClassificatioClassificationn ooff emeraldemeraldss bbyy North Island, New Zealand neural network analysis PoirotPoirot,, J.P J.P.. BezoaBezoarr neural network analysis Ponahlo, ]. CL emission and photoexcitation EliezriEliezri,, I.ZI.Z. .Th Thee isotopi isotopicc compositiocompositionn ooff oxygeoxygenn Ponahlo, J. CL emission and photoexcitation in emeralds as an indicator of origin spectrometry in gemmology in emeralds as an indicator of origin spectrometry in gemmology Forestier, F.H. Bactrian emeralds: myth or Saul, J.M. Libyan desert glass Forestier, F.H. Bactrian emeralds: myth or Saul, J.M. Libyan desert glass reality? Panjshir valley (Afghanistan) Schmetzer, K. Characterization of Chinese reality? Panjshir valley (Afghanistan) Schmetzer, K. Characterization of Chinese Fritsch, E. The morphology of natural gem hydrothermal synthetic emerald Fritsch, E. The morphology of natural gem hydrothermal synthetic emerald diamond: a status report Schwarz, D. The chemical properties of gem diamond: a status report Schwarzcorundums, D. Th frome chemica south-eastl propertie Asia s of gem Fritsch, E. About a blue quartz from Madagascar corundums from south-east Asia Fritsch(given, E. Abou on behalft a blu ofe quartB. Lasnier)z from Madagascar Sevdermish, M. The Diamond Pipeline into the Sevdermishthird millenium:, M. The Diamon part I.d ThePipelin restructurede into the Gao(give Yan.n Researchon behalf onof TiB. andLasnier Cr diffusion) treated Gao Yan. Research on Ti and Cr diffusion treated thirDiamondd millenium Pipeline:: par a t multi-channelI. The restructure systemd star sapphires Diamond Pipeline: a multi-channel system star sapphires and its effects on the retail diamond Gray, M. The benitoite gem mine: historical and its effects on the retail diamond Gray, M. The benitoite gem mine: historical jewellery industry production and future potential jewellery industry production and future potential Shida,]. Characteristics of cathodoluminescence Graziani, G. The origin assessment of the Shida, J. Characteristics of cathodoluminescence Graziani, G. The origin assessment of the for yellow diamonds of various types Roman archaeological emerald for yellow diamonds of various types Roman archaeological emerald Siripant, S. A gem colour communication system Giibelin, E.J. Gemstones of Switzerland Siripant, S. A gem colour communication system Gubelin, E.J. Gemstones of Switzerland Sobolev, N.V. Mineral inclusions in large crystals Hiinni, H.A. Maw-sit-sit kosmochlor-jade: a Sobolevof Yakutian, N.V. Minera diamondsl inclusion s in large crystals Hanni, H.A. Maw-sit-sit kosmochlor-jade: a metamorphic rock with a complex Sunagawa,of Yakutia I.n diamondGrowth-induceds imperfections 5555 metamorphic rock with a complex composition from Myanmar (Burma) Sunagawaand inhomogeneities, I. Growth-induce in singled imperfectioncrystals s Harding,compositio RRn Collectors' from Myanma stonesr (Burma ) Superchi,and inhomogeneitie M. Sapphires in singl occurrencese crystals at HardingHyrsl, J,. R.RGemstones. Collectors and' stone ornamentals stones of SuperchiAmbondromifehy,, M. Sapphir Antsirananae occurrence Provinces at, Hyrsl,Bolivia J. Gemstone s and ornamental stones of AmbondromifehyNorth Madagascar, Antsiranana Province, Joshi,Bolivi V. aComparative study of Indian rubies vis­ Sutherland,North Madagasca F.L. rRemarkable similarities Joshi,a-vis V. otherComparative rubies study of Indian rubies visa-visSutherland between, F.Lgem. Remarkablcorundume suitessimilaritie froms Kane, RE.othe Kashmirr rubies ruby - a preliminary report betweeBarrington,n ge Australia,m corundu andm Pailin suite, Cambodia,s from Kane,on R.E. the depositKashmir at ruby Nangirnali, - a preliminary Azad Kashmir, report Barringtonbasalt fields, Australia , and Pailin, Cambodia, oPakistann the deposi t at Nangimali, Azad Kashmir, Tay,basal TS.t fieldAmbers identification using micro­ KoivulaPakista, Jn.I. Reversible twinning in a unique Tay,Raman T.S. Ambe spectroscopyr identificatio n using micro- Koivulasynthetic, J.I. Reversiblmaterial e twinning in a unique Tillander,Raman H.spectroscop A critical yanalysis of rose cuts Levinson,syntheti cA.A. materia Thel Diamond Pipeline into the TillanderTombs, ,G.A. H. A Distinction critical analysi betweens of ros naturale cuts and Levinsonthird , millennium:A.A. The Diamon part dII. PipelinThe rolee int ofo ththee Tombssynthetic, G.A. orDistinctio imitationn betweeopal n natural and thirmodernd millennium diamond: cuttingpart II .industry The rol ofe oIndiaf the Zoysa,syntheti E.cG. o r imitatioColour n changeopal garnet from Milisenda,modern diamonCC Thed cuttinnew Tunduru-Songeag industry of Indi gema ZoysaThelulla, E.G-.Wellawaya Colour , changSri Lankae garne t from Milisendafields,, southernC.C. The Tanzanianew Tunduru-Songe a gem Zwaan,Thelulla-Wellawaya P.C Cultured pearls, Sri Lank froma Indonesia fields, southern Tanzania Zwaan, P.C. Cultured pearls from Indonesia Poster presentations Balitsky, V.S. High temperature pinkPoste quartzr andpresentation Kanis, J. Sandawanas emerald mines, Zimbabwe Balitskyother, V.S new. Hig synthetich temperatur colourede pink varietiesquartz an dof KanisShatsky,, J. Sandawan V. Newa emeralhydrothermald mines, Zimbabwsynthetice quartz sapphires, grown by TAIRUS Co. Ltd in other new synthetic coloured varieties of Shatsky, V. New hydrothermal synthetic Graziani, G. Tomb n.2, Necropolis of Vallerano, Novosibirsk, Russia quartz sapphires, grown by TAIRUS Co. Ltd in Rome, Italy: study about the jewels Sutherland, FL. Gem activities of the Australian Graziani, G. Tomb n.2, Necropolis of Vallerano, Novosibirsk, Russia Joshi, V. Gemstone deposits of India Museum Rome, Italy: study about the jewels Sutherland, F.L. Gem activities of the Australian Joshi, V. Gemstone deposits of India Museum

Proceedings and Notices GIAGIA SYMPOSIUM:SYMPOSIUM : CALLCALL FORFOR Garland,Garland, MaryMary I.,I., London,London, Ont.,Ont., Canada. 19971997 POSTERS Groom,Groom, Peter,Peter, Marlborough,Marlborough, Wilts.Wilts. 19831983 POSTERS Hainschwang,Hainschwang, ThomasThomas NikolaiNikolai Alexander,Alexander, TheThe GemologicalGemological InstituteInstitute ofof AmericaAmerica willwill Ruggell,Ruggell, Liechtenstein.. 19971997 hosthost thethe 19991999 InternationalInternational GemologicalGemological Hazelius-Berglund,Hazelius-Berglund, Wiveca, Lidingo,Lidingo, Sweden. 19971997 SymposiumSymposium inin SanSan Diego,Diego, CaliforniaCalifornia onon HeHe Xinping,Xinping, Guilin,Guilin, Guangxi,Guangxi, P.R.PR. China.China. 19971997 21-2421-24 June.June. MoreMore thanthan 20002000 peoplepeople areare expectedexpected KuangKuang YongYong Hong,Hong, Guilin,Guilin, Guangxi,Guangxi, P.R.PR. China. toto attendattend thisthis pivotalpivotal event.event. TheThe symposiumsymposium 19971997 programmeprogramme - withwith thethe themthemee 'Meeting'Meeting thethe Li Dongsheng, Guiling, Guangxi, P.R. China. 1997 , Li Dongsheng, Guiling, Guangxi, PR. China. 1997 Millennium'Millennium - willwill feature technicaltechnical sessionssessions andand MaMa HueiHuei Chi,Chi, Taipei,Taipei, Taiwan,Taiwan, Rep.Rep. ofof China.China. 19971997 panelpanel discussionsdiscussions onon a varietyvariety ofof topictopicss ofof vitalvital NgNg WaiWai Ching,Ching, HongHong Kong.Kong. 19971997 interestinterest toto allall membersmembers ofof thethe gemgem andand jewelleryjewellery Rimmer,Rimmer, RaRayy Ian, BootIe,Bootle, Merseyside.Merseyside. 19971997 industry.industry. InIn addition,addition, therethere willwill bebe anan openopen Semenets,Semenets, Elena, NorthNorth Vancouver,Vancouver, BC,, Canada. PosterPoster SessionSession featuringfeaturing originaloriginal presentationspresentations 19971997 onon suchsuch topictopicss asas neneww gemgem materials,materials, syntheticsynthetic Teskeredzic,Teskeredzic, Senada,Senada, London.London. 19971997 gegemm materials, treatments, gemgem identificationidentification TsangTsang WaWaii WanWan,, HonHongg KongKong.. 19919977 anandd gradinggrading,, instrumentatioinstrumentationn andand techniques,techniques, YaYauu HaHauu YeungYeung,, N.T.N.T.,, HonHongg Kong.. 19919977 gegemm localitieslocalities,, gemgem explorationexploration,, jewelleryjewellery ZengZeng,, Chunguang,Chunguang, SingaporeSingapore.. 19919966 manufacturing,manufacturing, anandd jewellerjewelleryy design.design. ZhanZhangg SumeiSumei,, Guilin,Guilin, Guangxi,Guangxi, PRP.R.. China.. 19919977 Contributions araree beinbeingg solicitesolicitedd forfor thisthis PosterPoster ZhZhuu YongYong,, Guilin,Guilin, GuangxiGuangxi,, PRP.R.. ChinaChina.. 19919977 Session.Session. ToTo bbee considereconsideredd foforr thithiss importantimportant eventevent (spac(spacee isis limited),limited), pleaspleasee submitsubmit a preliminarypreliminary OrdinaryOrdinary MembershipMembership abstracabstractt (n(noo mormoree thathann 252500 wordswords)) ttoo ononee ofof thethe Astor, Flora, London PosterPoster SessionSession organizerorganizerss bbyy 1 OctobeOctoberr 1998.1998. FoForr Astor, Flora, London furthefurtherr informationinformation oonn ththee PosterPoster Session,Session, contactcontact Barguirdjian,Barguirdjian, RalphRalph,, LondonLondon Beaty, Julie Marie, London DrDr JamesJames ShigleyShigley atat 760-603-4019760-603-4019 (Fax:(Fax: 760-603-4021760-603-4021, , Beaty, Julie Marie, London Begley-Gray, Margaret Mary, Little Carlton, E-mail:: [email protected]@gia.edu)) oorr MMss DonDonaa DirlaDirlamm aatt Begley-Gray, Margaret Mary, Little Carlton, Newark, Notts. 760-603-415760-603-41544 (Fax:(Fax: 760-603-425760-603-42566 oorr e-maile-mail:: Newark, Notts. 5656 [email protected])[email protected]).. FoForr informatioinformationn oonn thethe Bhangu,, GurpaulGurpaul,, IlfordIIford,, EsseEssexx Bhatia, Naresh, Richmond, Surrey SymposiumSymposium,, contaccontactt CaroCaroll MoffatMoffattt aatt 760-603-440760-603-44066 Bhatia, Naresh, Richmond, Surrey ([email protected])([email protected]).. Burgoyne, SheilaSheila,, TotteridgeTotteridge,, LondoLondonn ChonChongg WaWaii MingMing,, OrpingtonOrpington,, KenKentt CookseyCooksey,, BriaBriann DerekDerek,, BureBuress StSt.. MaryMary,, SuffolkSuffolk MEETINGMEETINGSS OOFF THTHEE COUNCICOUNCILL CortesCortes,, CarolinaCarolina,, LondoLondonn OOFF MANAGEMENTMANAGEMENT ddee BottonBotton,, CarolinCarolinee CoelhoCoelho,, LondoLondonn Draper, Zoe Shaw, Upper Abbeywood, London AAtt a meetinmeetingg ooff ththee CounciCouncill ooff ManagementManagement Draper, Zoe Shaw, Upper Abbeywood, London Dupuy, Harold A., Baton Rouge, La., USA helheldd aatt 2277 GrevillGrevillee StreetStreet,, LondoLondonn EC1EClNN 8SU8SU,, oonn Dupuy, Harold A., Baton Rouge, La., USA Freakley, Sharon Adele Maud, Bangkok, Thailand 1188 SeptembeSeptemberr 1997, ththee businesbusinesss transactedtransacted Freakley, Sharon Adele Maud, Bangkok, Thailand Gandhi, Amar A.A., Stanmore, Middx. includeincludedd ththee electioelectionn ooff ththee following:: Gandhi, Amar A.A., Stanmore, Middx. GarrettGarrett,, FranceFrancess S.J.S.J.,, Crawley,, W. SussexSussex Gray, Gisella,, LondoLondonn DiamonDiamondd MembershiMembershipp (DGA(DGA)) Grech,, CarrieannCarrieann, , RichmondRichmond,, SurreSurreyy HuHunn LaLaii ChanChan,, Macau,, HonHongg KongKong.. 19919977 GreenfieldGreenfield,, DawDawnn MelanieMelanie,, EynsfordEynsford,, KenKentt JosyfonJosyfon,, BrucBrucee MichaelMichael,, HoveHove,, EasEastt SussexSussex.. 19919977 HunterHunter,, PaulinPaulinee A.A.,, CaversfieldCaversfield,, OxonOxon.. LaLaww WaWaii HunHungg RaymondRaymond,, KowloonKowloon,, HonHongg KongKong.. KangKang,, BonBongg SukSuk,, LondoLondonn 19919977 Kellerson,, LaurenLaurentt P.P.,, LondoLondonn SimpsonSimpson,, PetePeterr RobertRobert,, RichmondRichmond,, SurreySurrey.. 19919977 KempKemp,, MargareMargarett AnneAnne,, BackwellBackwell,, N.. SomerseSomersett YaYann YeYeee MeiMei,, KowloonKowloon,, HonHongg KongKong.. 19919977 KonstandopoulouKonstandopoulou,, GaroufalliaGaroufallia,, AthensAthens,, GreecGreecee YiYipp ShuShu LeungLeung Christopher,Christopher, Kowloon,Kowloon, HongHong Kong.Kong. LinLin,, ChiChiaa Wei, LondoLondonn 19919977 MaungMaung,, HlHlaa WaiWai,, SingaporSingaporee YuaYuann JoJoee Chih-ChungChih-Chung,, TaipeiTaipei,, TaiwanTaiwan,, RepRep.. ooff NoyceNoyce,, David,, BognoBognorr RegisRegis,, WW.. SussexSussex China.. 19919977 O'Byrne,, Rose-Marie,, BicesterBicester,, OxonOxon.. PaphitisPaphitis,, Constantinos,Constantinos, LimassolLimassol,, CypruCypruss Patel,, NitaNita,, NewburyNewbury,, BerksBerks.. FellowshiFellowshipp (FGA(FGA)) PaulsenPaulsen,, Sarah-JeanSarah-Jean,, CuttesloweCutteslowe,, OxforOxfordd CaCaii BingBing,, GuilinGuiIin,, GuangxiGuangxi,, PRP.R.. ChinaChina.. 19919977 RigaRiga,, OlybiaOlybia,, AthensAthens,, GreecGreecee ChangChang,, CirclCirclee HuenHuen,, NortNorthh YorkYork,, Ont.,Ont., Canada.Canada. 19971997 RollissonRollisson,, AdeliaAdelia,, LondoLondonn

JJ.. Gemm.,Gemm., 1998,1998,26,1,49-58 26, 1,49-58 Saunders,Saunders, Frank,Frank, Spennymoor,Spennymoor, CoCo.. DurhamDurham Barsk,Barsk, Christer,Christer, PelloPello,, SwedenSweden Sethi,Sethi, Barti,Barti, LondonLondon Bienemann,Bienemann, AndreaAndreass M.M.,, PolsbroekPolsbroek,, ThThee Shemirani,Shemirani, Payam,Payam, LondonLondon NetherlandNetherlandss Strathnikova,Strathnikova, Mariya,Mariya, Stratford,Stratford, LondonLondon ChristouChristou,, AngelosAngelos,, Halkoutsa, LimassolLimassol,, CyprusCyprus Tulo,Tulo, KarenKaren Simone,Simone, Ludwigshafen,Ludwigshafen, GermanyGermany Deligianni,Deligianni, Christina,Christina, Athens,Athens, GreecGreecee Tulsyan,Tulsyan, Shalini,Shalini, Karnataka,Karnataka, IndiaIndia Deutscher,Deutscher, Gilad,Gilad, KiryatKiryat Ono,Ono, IsraelIsrael Valrani,Valrani, Anju,Anju, LondonLondon Dykhuis,Dykhuis, LuellaLuella Woods,Woods, Tucson,Tucson, ArizonaArizona,, USUSAA VerhoeffVerhoeff,, DirDirkk JacobusJacobus,, Leeuwarden,Leeuwarden, ThThee Edwards,Edwards, Heidi,Heidi, Burntwood,Burntwood, StaffsStaffs NetherlandNetherlandss Endo,Endo, MasahikoMasahiko,, OsakOsakaa City,City, OsakaOsaka,, JapanJapan Wood-HeathWood-Heath,, DaviDavidd LewisLewis,, neanearr MeophamMeopham,, KentKent Forward,Forward, Stephen,Stephen, LondonLondon YoungYoung,, GeoffreGeoffreyy William,William, Surbiton,Surbiton, SurreySurrey GlaserGlaser NvkNvk,, SonjaSonja I.,I., Galle,Galle, SriSri LankLankaa Hill,Hill, EmmaEmma,, MaidMaidaa ValeVale,, LondonLondon LaboratoryLaboratory MembershipMembership James,James, RobertRobert c.,C, NaplesNaples,, Fla.Fla.,, USUSAA Kataoka,Kataoka, NorikoNoriko,, MachidMachidaa City,City, TokyoTokyo,, JapanJapan ArtArtss & AntiqueAntiquess LtdLtd,, LondonLondon WWIl Koshiba,Koshiba, Shoko,Shoko, SagamiharaSagamihara City,City, KanagawKanagawaa Pref.,Pref., JethrJethroo MarieMarless TradinTradingg Co.Co.,, NewtoNewtonn Abbot,Abbot, Devon,Devon, JapanJapan TQ1TQ125LD2 5LD LamLam,, Jill,Jill, Rochester,Rochester, KentKent TheThe SouthernSouthern Goldsmiths,Goldsmiths, HaywardHaywardss Heath,Heath, LeeLee,, Dongjae,Dongjae, HappokuHappoku,, Masan,Masan, S.S. KoreaKorea Sussex,Sussex, RH1RH166 4L4LAA Maehara,Maehara, Tamao,Tamao, Isesaki,Isesaki, Gunma,Gunma, JapanJapan T.M.T.M. SuttonSutton Ltd,Ltd, London,London, SWlESW1E 5LB5LB McCabe,McCabe, MariannMariannee c.,C, Guildford,Guildford, SurreySurrey Monje,Monje, Lucy,Lucy, SantaSanta FeFe dada Bogota,Bogota, ColombiaColombia TransfersTransfers fromfrom FellowshipFellowship Moore,Moore, RowaRowann Duggan,Duggan, Stoke,Stoke, Coventry,Coventry, ttoo FGA,FGA, DGADGA Warwicks.Warwicks. OhtsukaOhtsuka,, Mayurni,Mayumi, NeyagawNeyagawaa CityCity,, Osaka,Osaka, JapanJapan BalBalll EdwardsEdwards,, Chantal,Chantal, Cheltenham,Cheltenham, GlosGlos.. Renard-RichardRenard-Richard,, Joelle,Joelle, RuislipRuislip,, Middx.Middx. Brooke-WebbBrooke-Webb,, Susannah,Susannah, LondonLondon Seki,Seki, Shoko,Shoko, OsakaOsaka CityCity,, OsakaOsaka,, JapanJapan CadbyCadby,, JohJohnn H.V.,H.V., TrowbridgeTrowbridge,, WiltsWilts.. Shih,Shih, Shu-Chuan,Shu-Chuan, HampsteadHampstead,, LondonLondon CarlssonCarlsson,, JohannJohannaa A.A.,, LondonLondon Soderstrom,Soderstrom, Jenny,Jenny, LannavaaraLannavaara,, SwedenSweden Cookson,Cookson, IanIan,, Darnall,Darnall, Sheffield,Sheffield, YorkYorkss Suzuki,Suzuki, NorikoNoriko,, IkomIkomaa City,City, NarNaraa Pref.,Pref., JapanJapan 5757 Dempster,Dempster, Stuart,Stuart, Shettleston,Shettleston, Glasgow,Glasgow, ScotlandScotland Tashiro,Tashiro, Hisami,Hisami, UjUjii CityCity,, JapanJapan Harris,Harris, AnnettAnnettee MiaMia,, HanburyHanbury,, WorcsWorcs.. VernonVernon,, PennPennyy Ann,Ann, HigHighh WycombeWycombe,, BuckBuckss Heilpern,Heilpern, HeleneHelene,, EppingEpping,, EsseEssexx WanWangg ChieChienn LingLing,, Taichung,Taichung, Taiwan,Taiwan, Rep.Rep. ofof ChinaChina Hopley,Hopley, KatharineKatharine Bridget,Bridget, CoventryCoventry,, WesWestt Yoshitake,Yoshitake, Yurni,Yumi, LondonLondon MidlandMidlandss LinLin HsiHsinn PeiPei,, Wuhan,Wuhan, HubeiHubei,, P.R.P.R. ChinaChina MaoMao LingyunLingyun,, BeijingBeijing,, P.RP.R.. ChinaChina TransfersTransfers frofromm OrdinaryOrdinary MartinMartin,, JennifeJenniferr FrancesFrances,, ActonActon,, LondonLondon MembershiMembershipp toto FGAFGA,, DGADGA Papadopoulos,Papadopoulos, AA.. Dimitrios,Dimitrios, Athens,Athens, GreecGreecee FenFengg HsiuHsiu YunYun,, Wuhan,Wuhan, HubeiHubei,, P.RP.R.. ChinaChina Randall,Randall, GarryGarry MarshallMarshall,, KingstonKingston,, SurreySurrey VerneyVerney WhiteWhite,, Catherine,Catherine, FulhamFulham,, LondonLondon Stather,Stather, LomLomee FrancisFrancis,, Charlton,Charlton, LondonLondon Wong,Wong, YikYik Shih,Shih, KualaKuala LumpurLumpur,, MalaysiaMalaysia Stead,Stead, GrahaGrahamm Scott,Scott, Tillsonburg,Tillsonburg, Ont.,Ont., CanadaCanada Thornton,Thornton, TimothyTimothy JohnJohn,, WimbledonWimbledon,, LondonLondon VareyVarey,, IrenIrenaa Maria,Maria, UllesthorpeUllesthorpe,, LeicsLeics.. TransferTransferss frofromm DiamondDiamond WhiteWhite,, RobertRobert,, Kingsthorpe,Kingsthorpe, NorthantsNorthants MembershipMembership ttoo FGAFGA,, DGADGA Wu Ming Hsun, Wuhan, Hubei, P.R. China Wu Ming Hsun, Wuhan, Hubei, P.R. China NottbuschNottbusch,, JurgeJurgenn UweUwe,, Appel,Appel, GermanyGermany Stossel,Stossel, HilaryHilary JeanneJeanne,, Perth,Perth, WAWA,, AustraliaAustralia TransferTransfer frofromm OrdinaryOrdinary AAtt a meetinmeetingg ofof ththee CouncilCouncil ofof ManagementManagement MembershiMembershipp toto DGADGA heldheld aatt 2727 GrevillGrevillee Street,Street, LondoLondonn EClNEC1N 8SU,8SU, onon 1515 OctobeOctoberr 1997,1997, ththee businesbusinesss transactetransactedd includedincluded FieldingFielding,, GeoffreyGeoffrey Ian,Ian, Tottington,Tottington, Bury,Bury, LanesLanes.. ththee electionelection ofof ththee following:following:

TransfersTransfers frofromm OrdinaryOrdinary DiamondDiamond MembershiMembershipp (DGA(DGA)) MembershiMembershipp toto FGFGAA MacDonald,MacDonald, KarenKaren JaneJane,, Dundonnell,Dundonnell, WesteWesterr RossRoss,, Arsenikakis,Arsenikakis, Helena,Helena, BlackwoodBlackwood,, SA,SA, AustraliaAustralia Scotland.Scotland. 19971997 BappooBappoo,, ReenabaiReenabai,, Croydon,Croydon, SurreySurrey Mak,Mak, TsuTsuii Sim,Sim, HonHongg Kong.Kong. 19971997

Proceedings and Notices FellowshiFellowshipp (FGA)(FGA) FellowshiFellowshipp (FGA)(FGA) BeentjesBeentjes,, TheodorusTheodorus,, ChichesterChichester,, WesWestt SussexSussex.. 19919900 CheChenn TaoTao,, Shanghai,Shanghai, PRP.R.. ChinaChina.. 19919977 CowleyCowley,, JacalyJacalynn GloriaGloria,, WimbledonWimbledon,, LondonLondon.. 19919977 DaviesDavies,, MaggiMaggiee WillowWillow,, WaresideWareside,, Hertfordshire.Hertfordshire. HsieHsiehh JuaJuann Ku-WeiKu-Wei,, ShiShinn JuanJuangg City,City, TaipeiTaipei,, 19971997 TaiwanTaiwan,, RepRep.. ofof ChinaChina.. 19919977 LeathleyLeathley,, AdaAdamm BrianBrian,, Shiptonthorpe,Shiptonthorpe, YorkYork.. 19919922 HuttonHutton,, KatieKatie,, LondonLondon.. 19919977 LiLiuu HuiHui,, ShanghaiShanghai,, PRP.R.. China.China. 19919977 KazemiKazemi,, Sima,Sima, NortNorthh VancouverVancouver,, BCBC,, Canada.Canada. 19919977 PaPann JieJie,, Shanghai,Shanghai, PRP.R.. ChinaChina.. 19919977 KonstantaraKonstantara,, AikateriniAikaterini,, Thessaloniki,Thessaloniki, Greece.Greece. 19919977 Rees-WardillRees-Wardill,, TanyaTanya,, WallingtonWallington,, Surrey.Surrey. 19919977 LindroosLindroos,, AnnAnnaa KaroliinaKaroliina,, PoriPori,, FinlandFinland.. 19919977 TunTun,, ThanThan,, YangonYangon,, MyanmarMyanmar.. 19919977 XXuu ZhiyiZhiyi,, ShanghaiShanghai,, PRP.R.. ChinaChina.. 19919977 LithibyLithiby,, JonathaJonathann PeterPeter,, Kingston-upon-Thames,Kingston-upon-Thames, ZhZhuu YeYe,, ShanghaiShanghai,, PRP.R.. ChinaChina.. 19919977 SurreySurrey.. 19919900 LuiLui,, AlicAlicee Miu-LingMiu-Ling,, RichmondRichmond,, BCBC,, Canada.Canada. 19971997 Miikiiriiinen,Makarainen, PiiiviPaivi HelenaHelena,, HelsinkiHelsinki,, FinlandFinland.. 19919977 OrdinarOrdinaryy MembershipMembership NiemiNiemi,, MarkkuMarkku,, LappeenrantaLappeenranta,, FinlandFinland.. 19919977 BrownBrown,, VanessaVanessa,, Sittingbourne,Sittingbourne, KenKentt PowellPowell,, GergoryGergory J.J.,, PrestatynPrestatyn,, NN.. WalesWales.. 19819866 BurgeBurge,, AnitAnitaa SiuSiu Sing,Sing, HaylinHaylingg IslandIsland,, HantsHants.. SuninmakiSuninmiiki,, VirpVirpii KristiinKristiinaa AnnikaAnnika,, Helsinki,Helsinki, DonnellyDonnelly,, Lee-onLee-onaa FreidaFreida,, AyAyrr FinlandFinland.. 19919977 HowesHowes,, RaymondRaymond,, WeymouthWeymouth,, DorsetDorset TseTse KwoKwokk FunFungg MatthewMatthew,, KowloonKowloon,, HonHongg KongKong.. HuddartHuddart,, AlastairAlastair,, LudlowLudlow,, ShropshireShropshire 19891989 MaxwellMaxwell,, Gary,Gary, LondonLondon vavann dederr VijghVijgh,, CarolinCarolinee ElviraElvira,, DiemenDiemen,, ThThee MizenMizen,, StevenSteven,, MarbellaMarbella,, SpainSpain NetherlandsNetherlands.. 19919977 ShaneShane,, ThomasThomas,, EnglewoodEnglewood,, COCO,, USUSAA WellsWells,, AndrewAndrew,, Caterham,Caterham, Surrey.Surrey. 19919911 Smith,Smith, SaraSarahh AnneAnne,, BristolBristol,, AvoAvonn YogalingamYogalingam,, NirupaNirupa,, ColomboColombo,, SriSri LankaLanka.. 19919977 TaylorTaylor,, WarreWarrenn MortoMortonn PearcePearce,, SevenoaksSevenoaks,, KenKentt ZhaoZhao,, YmgYing Ymg,Ying, Nanning, Nanning, Guangxi, Guangxi ,P.R. PR. China.China .1997 1997 WorrallWorrall,, EdwinEdwin,, RayleighRayleigh,, EsseEssexx YoneyamaYoneyama,, KimikoKimiko,, EalingEaling,, LondonLondon ZetlandZetland,, MartinMartin,, BlackpoolBlackpool,, LanesLanes.. 5858 OrdinaryOrdinary MembershipMembership ArnoldArnold,, JanJanee ElizabethElizabeth,, LondonLondon LaboratoryLaboratory MembershipMembership BernardBernard,, DaviDavidd AlfreAlfredd WilliamWilliam,, CarshaltonCarshalton AspreyAsprey,, LondoLondonn W1WIY OAROAR BeechesBeeches,, SurreySurrey K.c.K.C. GoldGold,, KualKualaa LumpurLumpur,, MalaysiaMalaysia EEIl MoussawiMoussawi,, HamedHamed,, LondonLondon FanFan,, PPoo ChuChu CynthiaCynthia,, ScarboroughScarborough,, Ont.Ont.,, CanadaCanada HodgsonHodgson,, JaneJane,, WatfordWatford,, HertfordshireHertfordshire MiddlemissMiddlemiss,, RonalRonaldd DavidDavid,, NorhilNorhilll onon TweedTweed,, ADVERTISINADVERTISINGG NorthumberlanNorthumberlandd iinn ththee JournaJournall ofof GemmologyGemmology MittalMittal,, Smita,Smita, DelhiDelhi,, IndiaIndia OlivaresOlivares,, ElkElkaa MarieMarie,, GibraltarGibraltar TheThe EditorEditorss ofof ththee JournaJournall invitinvitee SujananiSujanani,, RamesRameshh K.,K., OchoOcho RiosRios,, JamaicaJamaica,, W.Iw.I.. advertisementadvertisementss frofromm gemstonegemstone anandd mineraminerall dealersdealers,, publisherspublishers,, andand othersothers LaboratoryLaboratory MembershipMembership witwithh interestsinterests inin ththee gemmological,gemmological, DynastDynastyy JewelJewelss LtdLtd,, LondoLondonn EC1EClNN 8LY8LY mineralogicalmineralogical,, AAtt a meetinmeetingg ooff ththee CouncilCouncil ofof ManagementManagement lapidarylapidary anandd jewellerjewelleryy fields.fields. helheldd aatt 2277 GrevilleGreville Street,Street, LondoLondonn EC1EClNN 8SU,8SU, onon 1199 NovembeNovemberr 1997,1997, ththee businesbusinesss transactetransactedd includedincluded RateRatess peperr insertion,insertion, excludingexcluding VATVAT,, ththee electionelection ofof ththee following:following: areare asas follows:follows: WholWholee pagpagee HalHalff pagpagee QuarterQuarter pagpagee £18£1800 £10£1000 £6£600 DiamonDiamondd MembershiMembershipp (DGA)(DGA) EnquirieEnquiriess ttoo MarMaryy BurlandBurland,, HsuHsu,, RobertRobert,, TaipeiTaipei,, Taiwan,Taiwan, RepRep.. ofof ChinaChina.. 19919977 GAGTL,GAGTL, 27 GrevilleGreville StreetStreet., LondoLondonn EC1ECINN 8S8SUU PattniPattni,, UnnaUnnatt NagiNaginn GordhandasGordhandas,, Kingsbury,Kingsbury, TelTel:: 01701711 4040433344 3334 FaxFax:: 01710171 404044 88438843 LondonLondon.. 19919977

J. Gemm., 1998,1998,26,1,49-58 26, 1, 49-58 CCZZ COLOUCOLOURR A set of ten round brilliant-cut A set of ten round brilliant-cut stonesstones,, 0.90.900 cctt ttoo 1.01.000 ctct.. EacEachh stonstonee hahass beenbeen electronicallelectronicallyy testetestedd oonn aa GraGrann .Colorimete Colorimeterr (TM),(TM), individuallindividuallyy numberenumberedd anandd certifiedcertified.. SupplieSuppliedd iinn aa gradingradingg anandd displadisplayy containercontainer.. ©ff«* gpf^lA.~1.^ 0,,11l SPiel ££.1 14 400 PEPERR SESET·T (Usua(Usuall PricPricee £175*£175*)) *Price'Pricess excludexcludee VATVAT,, postagpostagee anandd packinpackingg IdeaIdeall foforr valuatiovaluationn purposepurposess

GemmologicaGemmologicall InstrumentInstrumentss LimitedLimited,, 2277 GrevillGrevillee StreetStreet,, LondoLondonn EOEelN N 8SU8SU.. TelTel:: 01701711 -40-4044 33333344 FaxFax:: 0171-4040171 -404 88438843 5959

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Contents ™e Journal of Gemmology Turquoise from Hubei Province, China Qi Lijian, Yan Weixuan and Yang Mingxin

Iridescence in plagioclase feldspars 13 RA. Howie

Notes from the Gem and Pearl Testing Laboratory, 17 Bahrain - 6 A Safar and N. Sturman

Spinel and garnet star networks: an interesting 24 asterism in gems from Sri Lanka W.L.D.R.A. Kumaratilake

Colour in tapazes from rhyolite domes of the 29 San Luis Potosi volcanic field, Mexico S. Dewonck, ].L. Leroy and Y. Dusausoy

Gemstones and ornamental stones from Bolivia: 41 a review }. Hyrsl and A Petrov

Book Reviews 48

Proceedings of the Gemmological Association and 49 Gem Testing Laboratory of Great Britain and Notices

Cover Picture A picture of Paradise A turquoise carving Copyright © 1998 photographed The Gemmological Association and by Yuan Jiaqi Gem Testing Laboratory of Great Britain (See Turquoise from Registered Office: Palladium House, 1-4 Argyll Street, London W1V 2LD Hubei Province, China, p. 1)

ISSN: 1355-4565 Printed by Quadrant Qffeet Limited,-HertJEpr Limited,-HertJEprd d