Vol. 20 No. 3 July 1986 TheJournal of Gemmology

GEMMOLOGICAL ASSOCIATION OF GREAT BRITAIN OFFICERS AND COUNCIL

President: Sir Frank Claringbull Ph.D., F.lnst.P., F.G.S. Vice-Presidents: J. R. H. Chisholm, M.A., F.G.A. R. K. Mitchell, F.G.A. Chairman: D. ]. Callaghan, F.G.A. Vice-Chairman: N. W. Deeks, F.G.A. Honorary Treasurer: N. B. Israel, F. G. A.

Fell&Ws elected to Council: C. R. Cavey B. Jackson M. J. O'Donoghue, L. F. Cole C. B. Jones M. A., F.G.S. R. W. Croydon D. M. Larcher P. G. Read, C.Eug., P. J. E. Daly, B.Sc. D. Morgan M.I.E.E., M.I .E. R.E. A. J. French G. Neary A. W. R. Round S. E. Hiscox J. B. Nelson, Ph.D., F.R.M.S., E. Stern J. A. W. Hodgkinson F. InsLP., F.G.S. C. H. Winter D. Inkersole W. Nowak, C.Hug., F.R.Ae.S.

Branch Chairmen: Midlands Branch: P. West, F.G.A. Norlh-West Branch: S. Hill, F.G.A. South Yorkshire & Dislrict Branch: J. I. Reynolds, F.G.A.

Examiners: E. A. Jobbins, B.Sc., F.I.M.M., F.G.A. A. J. Allnutt, M.Sc., Ph.D., F.G.A. R. R. Harding, B .Sc., D . Phil. , F.G .A. G. H. Jones,B.Sc., Ph.D., F.G.A. D. G. Kent, F.G.A. E.M.Bruton,F.G.A. P. Sadler,B.Sc., F.G.S., F.G.A. C. Woodwara., B.Sc., F.G.A. A.E. Farn, F.G.A. M. Font-Altaba, D.Sc. ]. M. Bosch-Figueroa, D.Se. M. Virkkunen, M.Phil., F.G.A.

1 nstruc tors: V. G. Hinton, F.G.A. S. B. NikonCooper, B.D., F.G.A. P. A. Waters, F.G.A. J. Edwards, F.G.A. D. Pratt, F.G.A. R. J. Peace, B.Sc., F.G.A.

Editor: E. A. Jobbins, B.Sc., F.I.M.M., F.G.A. Consultant Editor: J. R. H. Chisholm, M.A., F.G.A. Editorial Assistant: Mary A. Burland Curator: C. R. Cavey, F.G.A. Secretary: Con Leuan, F.G.A. Deputy Secretary: Jonathan Brown, Barrister-at-Law, F.G.A.

Saint Dunstan's House, Carey Lane, London EC2V 8AB (By Goldsmith's Hall) Telephone:01-7264374 J. Gemm., 1986,20,3 137

TheJournalof^Journal of GemmologyGemmology

VOLUMEVOLUME 2020 NUMBERNUMBER THREETHREE JULYJULY 19819866

Cover PicturePicture ProtogeneticProtogenetic crystalscrystals ofof alteredaltered hornblendehornblende werewere first coatedcoated withwith anan initiainitiall layelayerr ofof opalopal andand thethenn laterlater werewere completelycompletely engulfedengulfed byby thisthis MexicanMexican opal.opal. TransmittedTransmitted andand obliqueoblique illumination.illumination. 4Sx.45x. SeeSee'Inclusion 'Inclusionss inin opal',opal', pppp.. 139-44.139-44. Photograph from'from 'PhotoatlasPhotoatlas ofofinclusions inclusions in in gemstones'. gemstones'.

ISSN:ISSN: 0022-12520022-1252 138 J. Gemm., 1986, 20, 3

NEW GEMMOLOGY COURSE

The Gemmological Association of Great Britain is proud to announce that from September 1986 it is introducing a new home study course in gemmology. This will prepare students for the examinations leading to the award of the Association's Fellowship Diploma.

The new course is radically different from other gemmological courses, and presents a new, friendly, step-by-step approach to learning that should be welcomed by students all over the world.

For further details, contact the Education Department, Gemmological Association of Great Britain, Saint Dunstan's House, Carey Lane, London, EC2V 8AB. Tel: 01-726 4374. Cables: GEMINST. JJ.. Gemm.Gemm.,, 1986,1986, 2020,, 3 139139

The long-awaitedlong-awaited new new bookbook about about inclusions inclusions in ingemstones gemstones by DrbyDrE. E. Giibelin Giibelin and and M r Mr J.I. J. KoivulaI. Koivula will will appear appear on on the marketmarket this this Autumn Autumn underunder the the title title of'Photoatlas of'Photoatlas of ofinclusions inclusions in gemstones'fin gemstones''f and and we arewe aredelighted delighted to learn to learn that that this bookbook is is dedicated dedicated to to Basil Basil W. W. Anderson. Anderson. Dr E. Giibelin has beenbeen successful successful in in securing securing the the co-operation co-operation ofProfessor of Professor H. 0 H.O.A. .A. Meyer Meyer and and Dr EDr . RoedderE. Roedder in in the UnitedUnited States, States, andand ofofProfessor Dr Dr H.A. H.A. StalderStalder inin Switzerland. Switzerland. The volume resultingresulting from from this this collaboration collaboration reveals reveals a spectacular a spectacular triumph triumph ofcolour of colour photomicrography, photomicrography, and the and the work isis obviouslyobviously destined destined to to become become a classic a classic in the in thefield. field. We Weare aretherefore therefore pleased pleased to publish to publish a foretaste a foretaste of this of work this work in thethe form form ofofthe the chapter chapter on on inclusions inclusions in inopal. opal. It isIt especiallyis especially appropriate appropriate to include to include it here, it here,since thesince subject the subject has not has not been presentedpresented in in the the Journal Journa lbefore. before. We congratulate Dr Dr Giibelin Giibelin and and his his team team on on their their great great achievement. achievement. The Editor

InclusionInclusionss inin opalopal

Dr Edward Gubelin,Gübelin, e.G.,C.G., F.G.A.* andJohnI.and John I. Koivula, C.G.,F.G.A.**C.G.,F.G.A.**

*Ratna*Ratna Mahal,Mahal, BenzeholzstrassBenzeholzstrassee 11II,, CH-604CH-60455 MeggeMeggenn LU,LU, SwitzerlandSwitzerland **Gemological**Gemological InstituteInstitute ofof America,America, Santa Monica,Monica, CACA 90406,90406, USAUSA

PreciousPrecious opal,opal, prizedprized forfor itsits spectralspectral playplay ooff andand thethe satisfyingsatisfying harmonyharmony ofof thethe livelylively colour­colour- colour,colour, iiss commonlycommonly describedescribedd asas anan amorphousamorphous play,play, isis thethe contemplationcontemplation ofof ththee manifoldmanifold uniqueunique silicasilica gel.gel. ButBut thethe amorphousamorphous statestate ofof opal'sopal's inclusionsinclusions - mainlymainly inin opalopal fromfrom Mexico.Mexico. ThisThis iiss structurestructure isis questionable.questionable. ItIt isis nownow knownknown thatthat opalopal especiallyespecially soso sincesince ththee greatgreat majoritymajority ofof opalsopals foundfound isis structurallystructurally composedcomposed ofof a more-or-Iessmore-or-less orderly,orderly, allall overover thethe worldworld eithereither havehave nono inclusionsinclusions oror thesethese close-packedclose-packed arrangementarrangement ofof submicroscopicsubmicroscopic cannotcannot bbee seenseen becausebecause ththee hosthost gemgem isis tootoo opaque.opaque. spheresspheres ofof twotwo crystallinecrystalline mineralmineralss - cristobalitecristobalite TheThe brownishbrownish opalopal termedtermed hyalite,hyalite, founfoundd inin andand tridymite.tridymite. InIn MexicanMexican opal,opal, whichwhich formedformed atat Mexico,Mexico, containscontains whitewhite spherulitesspherulites asas largelarge asas oneone higherhigher temperaturestemperatures thanthan itsits AustralianAustralian cousin,cousin, thethe millimetremillimetre inin diameter.diameter. ThisThis hyalitehyalite isis calledcalled irisiris spheresspheres consistconsist ratherrather ofof cristobalite.cristobalite. InIn thethe opalopal whenwhen itit displaydisplayss anan iridescenceiridescence resultingresulting AustralianAustralian opalopal theythey areare mormoree commonlycommonly tridymite.tridymite. fromfrom a finelyfinely layeredlayered internalinternal botryoidalbotryoidal structure.structure. TheThe sizesize ofof thesethese spheresspheres andand thethe interstitialinterstitial spacesspaces BrazilianBrazilian whitewhite opalsopals maymay containcontain tinytiny darkdark greygrey betweenbetween themthem dictate,dictate, throughthrough thethe diffractiondiffraction ooff octahedraoctahedra ofof thethe nickelnickel ironiron sulphide,sulphide, bravoite.bravoite. whitewhite light,light, thethe playplay ofof colourscolours anan opalopal willwill display.display. FineFine particlesparticles ofof sand-likesand-like matrixmatrix andand anan unevenuneven FormedFormed iinn sedimentarysedimentary oror volcanicvolcanic rocks,rocks, throughthrough distributiondistribution ofof body-colourbody-colour areare notednoted iinn somesome thethe invasioninvasion ofof low-temperaturelow-temperature silica-bearingsilica-bearing AustralianAustralian stones.stones. AsAs a resultresult ofof theirtheir translucenttranslucent toto solutions,solutions, opalopal isis essentiallyessentially composedcomposed ofof silica,silica, clearclear transparenttransparent opal-medium,opal-medium, oneone cancan seesee thatthat thethe withwith variablevariable waterwater ofof hydration.hydration. OpalsOpals may,may, inin firfiree opalsopals foundfound iinn MexicoMexico areare alivealive withwith inclusions.inclusions. time,time, looseloose theirtheir waterwater andand dehydratedehydrate toto chalcedony.chalcedony. NeedleNeedless ofof hornblende,hornblende, whichwhich onceonce protrudedprotruded fromfrom A smallsmall percentagepercentage ofof additionaladditional elementselements suchsuch asas thethe rhyoliterhyolite matrix,matrix, areare oftenoften trapped.trapped. Quartz,Quartz, aluminium,aluminium, iron,iron, calcium,calcium, magnesiummagnesium andand sodiumsodium goethitegoethite andand eveneven two-two- andand three-phasethree-phase inclusionsinclusions inin thethe formform ofof submicroscopicsubmicroscopic mineralmineral grains,grains, maymay areare bubutt a fewfew ofof thethe inclusionsinclusions identified.identified. TheThe alsoalso bbee present.present. followingfollowing richlrichlyy varyingvarying photomicrographsphotomicrographs ofof opalopal TheThe bodybody colourcolour ofof preciousprecious opalsopals rangesranges fromfrom inclusionsinclusions offeroffer anan impressiveimpressive showshow ofof theirtheir unsuspec­unsuspec­ nearnear colourlesscolourless toto milky-white,milky-white, yellow,yellow, orange,orange, red,red, tedted beautybeauty andand widewide variety.variety. greygrey ttoo nearlynearly blackblack,, andand brownbrown.. AsAs rapturouslyrapturously enchantingenchanting asas thethe contrastscontrasts ofof ththee gaygay kaleidoscopykaleidoscopy [Manuscript[Manuscript receivedreceived 31 31 March March 1986.] 1986. ]

tGiibelin,†Gübelin, E.,E., Koivula,Koivula, J.1.J.I. 1986.1986. PhotoatlasPhotoatlas of ofinclusions inclusions in gemstones. in gemstones. ABC Edition, ABC Edition Zurich., Zurich .

© CopyrightCopyright thethe GemmologicalGemmological AssociationAssociation ISSNISSN:: 0022-12520022-1252 140 J. Gemm., 1986, 20, 3

Fig. 1. Microscopic image showing the flow-structure in an opal from Querétaro, Mexico. Although usually present to some degree, flow zones are rarely as pronounced as here. Transmitted and oblique illumination. 15x.

Fig. 2. The flowing motion of the silica-gel which produced this Fig. 3. A confusing mass of acicular crystals of hornblende, all Mexican opal, had enough viscosity and force to break this displaying an opal coating. The entire grouping now needle-like crystal inclusion. Transmitted light. 40x. resides in this Mexican opal as a protogenetic jumble. Transmitted and oblique illumination. 20x.

Fig. 4. Here, it is clearly apparent how, in the first phase of Fig. 5. Botryoidal shapes, like these in blue opal from Mexico, solidification, a 'sock' of white opal enveloped a goethite are preferred by chalcedony inclusions. Darkfield illumina­ needle before the flaming Mexican fire opal enclosed this tion. 18x. primary formation with a secondary growth-phase. Darkfield with overhead lighting. 20x. J. Gemm., 1986, 20, 3 141

Fig. 6. A fire opal from Querétaro, Mexico, has equipped itself Fig. 7. Chalcedony inclusions, commonly resident in Mexican with an unmistakable identity-mark with the help of this opal, often surround themselves with curved fissures as a pair of white chalcedony 'eyes'. Darkfield with overhead result of internal tension. Darkfield illumination. 20x. illumination. lOx.

Fig. 8. Looking like glass, small aggregates of tiny plate-like Fig. 9. Translucent white cristobalite inclusions in a Mexican cristobalite crystallites hover in a water opal from Querétaro, opal, are suspended against a background of a deep Mexico. Darkfield illumination. 150x. blue/orange/red play of colour. Oblique illumination. 20x.

Fig. 10. This three-ph ase inclusion in a Mexican opal now occupies Fig. 11. Limonitized goethite needles once reached from the walls the area once filled by a rhombohedral crystal of a of the cavity in which this Mexican water opal solidified, mineral such as calcite or dolomite. A volume of liquid, a thereby being embraced as protogenetic inclusions. large gas bubble and numerous small red solid phases Dark-field illumination. 20x. now fill the void. Darkfield and oblique illumination 35x. 142 J. Gemm., 1986, 20, 3

Fig. 12. Earthy-brown inclusions in a Mexican opal, of the iron Fig. 13. A jumble of acicular crystals and thick black hornblende hydroxide goethite, illustrate the 'tree-ring' form produced crystals projecting from the rhyolite matrix into the by the repeated cycles of opal deposition on pre-existing Mexican opal. Oblique illumination. 30x. crystal inclusions. Transmitted and oblique illumination. 50x.

Fig. 14. A green-black hornblende crystal is covered with a crust of Fig. 15. Looking like billowy clouds, the dull white opaque limonite. Note the thickness of the limonite layer at the masses associated with this brown pseudomorph of top, near the fracture. Darkfield illumination. 34x. limonite after hornblende are inclusions of kaolinite, a clay mineral, in this Mexican opal. Oblique illumination. 40x.

Fig. 16. In a Mexican water opal, an unusual combination has Fig. 17. Limonitepseudomorphs after hornblende, create a speleo­ occurred through the intergrowth of hornblende-fragments logical image of stalagmites in a Mexican sherry opal. and kaolinite-platelets with some rhyolite-matrix. Darkfield Darkfield with side illumination. 8x. illumination. 34x. J. Gemm., 1986, 20, 3 143

Fig. 18. A yellow opal from Tanzania is charmingly enlivened by Fig. 19. Clear, transparent pinnacles of rock-crystal protrude from numerous dendrites of manganese oxide, varying in size. a crude mass of kaolinite in a Mexican blue opal. Transmitted illumination. 25x. Darkfield. 50x.

Fig. 20. A limonite-coated rock-crystal peak with flaming green Fig. 21. Premising Nature has sketched the Pyramids of Gizeh, colour-play, conjures up an ancient-Egyptian scene in a long before the Pharoahs of the IVth Dynasty erected fire opal from Querétaro, Mexico. Darkfield with side them: peaks of rock-crystal coated with limonite, and illumination. 12x. limonite rods, pierce a Mexican fire opal from the rhyolite matrix. The reflection offf the light-source gives the impression of a rising moon behind the pyramids. Darkfield with side illumination. 12x.

Fig. 22. An epigenetic pattern was produced when iron-rich fluids Fig. 23. The botryoidal finely laminated structure found in invaded the fracture in this Mexican opal and dried out. Mexican hyalite opals behaves as a diffraction grating Transmitted light. 40x. and gives rise to bright interference colours. Darkfield illumination. 45x. 144 J. Gemm., 1986, 20, 3

Fig. 24. (Top left.) The characteristic circular structure of Austra­ lian oolitic opal should not be confused with treated opals. Oblique illumination. 20x.

Fig. 25. (Top right.) The black cloud-like patches of subsurface soot characteristic of smoke-treated Mexican opals, are visible in this photomicrograph. Oblique illumination. 30x.

Fig. 26. (Left.) Porous Australian opals treated with sugar and sulphuric acid to give them a black body-colour. Under the microscope, such 'sugar-treated' opals have a pepper­ like character. Oblique illumination. 30x. J.J. Gemm.,Gemm., 1986,20,31986, 20, 3 145145

NotesNotes fromfrom thethe LaboratoryLaboratory -7

KennethScarratt,Kenneth Scarratt, F.G.A.F.G.A.

TheThe GemGem TestingTesting LaboratoryLaboratory ofof GreatGreat Britain,Britain, 2727 GrevilleGreville Street,Street, London,London, ECINEC1N 8SU8SU

ItIt hashas beenbeen saidsaid thatthat asas thethe AuthorAuthor hashas writtenwritten TheThe groupgroup ofof pearlspearls examinedexamined inin 19811981 meetsmeets withwith 'N'Note otess fromfrom thethe Laboratory'Laboratory' fromfrom whatwhat appearappear toto bebe thisthis descriptiondescription (Figures(Figures la,la,lb) 1b). . ItsIts lengthlength isis threethree differentdifferent laboratorieslaboratories overover thethe lastlast five years,years, approximately 37.237.2 rom,mm, thethe widthwidth isis approximately somesome explanationexplanation isis needed.needed. 18.318.3 mmmm andand itsits weightweight isis 24.7924.79 ct.ct. ItIt isis not,not, asas mightmight bebe thought,thought, thatthat thethe authorauthor TheThe 'Southern'Southern Cross'Cross' isis saidsaid toto havehave beenbeen foundfound likeslikes toto flitflit fromfrom oneone laboratorylaboratory toto another,another, indeedindeed inin oneone piecepiece byby a boyboy namednamed Clark,Clark, butbut beforebefore hehe hehe hahass remaineremainedd inin jusjustt oneone.. IItt iiss thethe Laboratory'sLaboratory's couldcould hanhandd itit oveoverr toto hishis employeremployer,, JamesJames KellyKelly,, itit namnamee thatthat hahass changed,changed, firstly frofromm 'The'The GemGem hahadd brokebrokenn intintoo threethree distincdistinctt piecespieces.. TestinTestingg LaboratorLaboratoryy ooff thethe LondonLondon ChambeChamberr ooff KunKunzz andand StevensoStevensonn furthefurtherr creditcredit HenryHenry CommercCommercee anandd IndustryIndustry'' anandd thethenn ttoo 'The'The BritishBritish TauntoTauntonn asas makingmaking a 'positiv'positivee statement'statement' thathatt 'there'there GeGemm TestinTestingg LaboratorLaboratoryy ofof thethe LondoLondonn ChamberChamber werweree onlyonly eigheightt pearlpearlss iinn ththee clusteclusterr whewhenn itit waswas soldsold ofof Commerc Commercee anandd Industry'Industry'.. ThThee LaboratorLaboratoryy iiss nonoww bbyy KellKellyy iinn 1883,1883, andand ttoo makmakee iitt resembleresemble a wellwell­- knowknownn aass 'The'The GemGem TestingTesting LaboratoryLaboratory ooff GreatGreat proportionedproportioned croscrosss - ththee rightright armarm beinbeingg absenabsentt -- Britain' .. anotheanotherr pearpearll ooff suitablesuitable sizesize anandd shapeshape wawass ThiThiss lateslatestt change,change, howeverhowever,, hahass beebeenn a littlelittle subsequentlysubsequently securedsecured atat CossackCossack anandd attacheattachedd inin moremore thanthan jusjustt a changechange iinn namename.. TheThe LaboratoryLaboratory iiss ththee propeproperr placplacee ttoo ththee others,others, whicwhichh iinn thethe nonoww nono longerlonger a parpartt ooff ththee LondoLondonn ChambeChamberr ooff meantimemeantime,, hahadd beebeenn re-fastenere-fastenedd togethertogether bbyy diamonddiamond CommerceCommerce.. ItIt isis anan entitentityy onon ititss ownown andand iiss cementcement,, thusthus makingmaking threethree artificialartificial jointjointss ...... ' administereadministeredd bbyy a committecommitteee madmadee uupp frofromm thethe IIff ththee grougroupp ooff pearlpearlss examineexaminedd iinn 19819811 iiss thethe Laboratory'Laboratory'ss membersmembers,, anandd representativerepresentativess fromfrom 'Souther'Southernn Cross'Cross',, whilswhilstt alalll ththee pearlpearlss forminformingg ththee ththee GemmologicaGemmologicall AssociatioAssociationn ooff GreaGreatt BritainBritain,, ththee croscrosss araree naturalnatural,, thertheree araree nonoww onlonlyy twtwoo naturalnatural NationaNationall AssociatioAssociationn ooff GoldsmithGoldsmithss anandd ththee BritishBritish jointjointss betweebetweenn ththee pearlpearlss ((AA anandd B iinn FigurFiguree 2)2).. JewellerJewellerss AssociationAssociation.. IItt iiss financed bbyy ititss membersmembers JoinJointt 'A'A'' hahass beebeenn strengthenestrengthenedd bbyy ththee additioadditionn ooff anandd ththee abovabovee AssociationsAssociations,, aass welwelll aass ththee LondonLondon somsomee adhesivadhesivee oonn ononee sidsidee anandd alalll ththee remainingremaining DiamonDiamondd Bourse,Bourse,., ththee LondoLondonn DiamonDiamondd CluClubb andand jointjointss araree nonoww artificial.artificial. othersothers.. ThThee LaboratoryLaboratory,, initiallinitiallyy directedirectedd bbyy B.B.W W.. ThThee internainternall naturanaturall structurestructuress iinn ththee individualindividual AndersoAndersonn frofromm 19219255 anandd thethenn bbyy A.EA.E.. FarFarnn fromfrom pearlpearlss araree fine, anandd thereforetherefore ththee detaidetaill iinn thethe 19719722 ttoo 19819811 hahass nonoww entereenteredd a neneww ereraa iinn whicwhichh thethe radiograpradiographh ooff thithiss grougroupp wilwilll nonott reproducreproducee wellwell.. AssociationAssociationss havhavee mormoree influencinfluencee oveoverr ititss operationsoperations.. ThThee radiograpradiographh iinn FigurFiguree 3 displaydisplayss ththee junctionsjunctions betweebetweenn ththee pearlspearls.. •* * *• * • • • WhilsWhilstt readinreadingg a newlnewlyy publishepublishedd boobookk oonn * * * pearlspearls(l)(1) wwee notenotedd a halhalff pagpagee descriptiodescriptionn ooff ononee ooff ththee mosmostt intriguinintriguingg ooff alalll 'pearls''pearls',, ththee 'Southern'Southern AAtt leasleastt ttoo ththee unaideunaidedd eyeeye,, glasglasss cacann providprovidee ononee Cross'Cross'.. ThiThiss reminderemindedd uuss ooff ouourr examinatioexaminationn iinn ooff ththee mosmostt convincinconvincingg imitationimitationss ooff jadeitejadeite.. IInn ththee 19819811 ooff a grougroupp ooff pearlpearlss whicwhichh werweree reputereputedd ttoo bbee paspastt thithiss hahass beebeenn particularlparticularlyy trutruee ooff glasglasss whicwhichh ththee 'Souther'Southernn Cross'Cross'.. hahass a mottlemottledd greegreenn colourincolouringg anandd a profusioprofusionn ooff The Book of thethe Pearl bbyy KunKunzz anandd Stevenson(2)Stevenson(2) sphericasphericall bubblesbubbles.. ThiThiss typtypee wawass ofteoftenn useusedd forfor describedescribess ththee 'Souther'Southernn CrossCross'' aass ' ...... ninninee attachedattached beabeadd necklacesnecklaces.. pearlpearlss forminformingg a RomaRomann CrosCrosss abouaboutt ononee anandd ononee AnotheAnotherr glasglasss whicwhichh iiss provinprovingg ttoo bbee a populapopularr halhalff incheinchess iinn lengthlength,, sevesevenn pearlpearlss constitutinconstitutingg ththee substitutsubstitutee foforr jadeitjadeitee iiss ththee ddevitrifiede vi trifled typetype.. ThisThis shafshaftt oorr standardstandard,, whilwhilee ththee armarmss araree formeformedd bbyy ononee materiamateriall cacann bbee madmadee ttoo resemblresemblee jadeitjadeitee closelcloselyy iinn pearpearll oonn eaceachh sidsidee ooff ththee seconsecondd ononee frofromm ththee uppeupperr botbothh coloucolourr anandd generagenerall appearanceappearance.. WheWhenn cabocabo­­ end'end'.. chonchonss araree sesett iinn ringringss thetheyy cacann bbee ververyy convincingconvincing..

© CopyrighCopyrightt ththee GemmologicalGemmological AssociationAssociation ISSNISSN:: 0022-12520022-1252 146 J. Gemm., 1986, 20, 3

Fig. 1. (a) Group ofnatural pearls said to be the'Southern Cross' (b) Group ofnatural pearls said to be the 'Southern Cross' (front). (back).

Fig. 2. Diagram of 'Southern Cross' (see Figure lb) indicating Fig. 3. Radiograph of the 'Southern Cross' displaying the the remaining natural junctions between the pearls junctions between the pearls. (A and B). All the remaining joints are artificial. J. fiemm., 1986, 20, 3 147

The stones set in the ring in Figure 4 are Amongst the modern buildings which are the examples of how plausible this material can be, Bahrain of today, merchants can still be found particularly when seen in the 'correct' setting. Both trading in the age old way (Figure 6) and even a cabochons are glass with RIs in the region of 1.52 humble rubbish skip makes a passer-by aware of the and fibrous inclusions (Figure 5). country's history (Figure 7). Bahrain was one of the greatest pearling centres and is still a centre for natural pearls'" it is said to be illegal to import a cultured pearl. In about 1915, Qatar, a close neighbour of Bahrain and another of the great pearling nations, had 350 pearling boats based in its main town Doha. At that time Doha was a town of some 12 000 people with a suq of about 50 shops and a Ruler's palace. There were also 60 sea-going trading boats running to Oman and nearly 100 fishing boats. This may seem a little out of place in 'Notes from the Laboratory', but many gemmologists make the journey to Sri Lanka or Thailand at least once in their lives, if not on a regular basis. Sadly only a few have taken the opportunity to break their flights Fig. 4. Two pieces of devitrified green glass, cut as drop-shaped either in Bahrain or Qatar, or any of the other Gulf cabochons and set in a ring. The setting is similar to that commonly used for jadeite. States which are regular stops for most aircraft flying between the UK and the Far East. There is much of gemmological interest in both Bahrain and Qatar. The National Museum in Qatar boasts an excellent display of the many qualities of natural pearl (Figure 8) and pearl diving and trading equipment (Figures 9 and 10). In the same museum a large aquarium brings home to the visitor the many natural dangers faced by the pearl divers each time they entered the Gulf waters. Simply, this 'note' is a reminder to the organizers of gemmological tours which pass through the Gulf, and to the regular traveller, that a large slice of gemmological history evolved in the area.

Fig. 5. Fibrous inclusions in the devitrified glass of Figure 4. • • •

• • • A green diamond brought into the Laboratory for The introduction of the cultured pearl could have testing (Figure 11) was found to be radioactive, and spelled disaster for the economies of the Gulf States it was possible to detect this radioactivity through a which were reliant upon the pearl as one of their sheet of lead 0.1 mm in thickness. Monitor main sources of income. However, the discovery of measurements indicated that the degree of radio­ oil and gas relegated the pearl, in terms of activity in the pavilion area was much greater than proportion of national income, to a much lower that in the crown area. level, and therefore all was saved. Whilst still in its setting the stone was placed on Even with this wealth, the old pearling nations its side, as in Figure 12, on a piece of X-ray film for have not altogether forgotten the traditions associ­ 118 hours. This produced the autoradiograph in ated with producing some of the world's finest Figure 13. pearls. The pearling families have not deserted the As the stone aroused a little curiosity the client pearl, and much of the trading flow in natural pearls was asked if he would give his permission for it to be is now in the opposite direction. The pearls that unset. This was necessary in order to obtain a were fished in the Gulf and sold on the European clearer view of its pavilion surface and to record its markets are now returning to the Gulf. spectrum. 148 J. Gemm., 1986, 20, 3

Fig. 6. A pearl merchant in Bahrain with his natural pearls and Fig. 7. Insignia on rubbish skips in Bahrain display the importance the tools of his trade. the pearling industry has had for the country.

Fig. 8. Yakkah or second quality natural pearls on display at the museum in Doha.

Fig. 9. Pearl diving equipment on display at the museum in Fig. 10. Pearl merchants equipment on display in the museum in Doha. Doha. J. Gemm., 1986, 20, 3 149

Fig. 11. Radioactive green diamond set in a ring. Fig. 12. Radioactive green diamond set in ring (as Figure 11), side view. Refer to Figure 13.

The spectrum displayed a weak GR1 band (Figure 14), and unlike a previously reported stone(3), which had brown diamond characteristics, this appeared to be a Cape series stone. When examined with a microscope, it could be seen that the green colour was located at and just below the surface of the pavilion facets. There was no green coloration in the crown facets. The colour in the pavilion facets was blotchy with many pin­ point sized, and some slightly larger, near colourless areas (Figure 15). In addition there were many small deep green marks, which varied in size and shape, in the same area. It would seem that this diamond had been treated on the pavilion only and not on the crown. This was Fig. 13. Autoradiograph produced by the green diamond of confirmed by two further autoradiographs, the first Figure 11 when positioned on X-ray film in the manner of which (Figure 16) was taken with the table facet of Figure 12 for a period of 118 hours. down on X-ray film. Here it can be seen that there has barely been any exposure of the film in the area which was in contact with, or close to, the crown of the stone. The second autoradiograph (Figure 17) was taken with one of the pavilion facets resting on the film. In comparing Figures 16 and 17 it should be noted that the exposure time for Figure 16 is W/i hours whilst that used for Figure 17 is only 30 minutes. With the stone in the same position, a similar and only slightly weaker exposure to that in Figure 17 was obtained in only 15 minutes. A close examination of Figure 17 will reveal a number of intense black spots which appear to be associated with the deep green marks on the surface of the stone. The stone measured 8.23-8.50 x 4.52 mm and weighed 1.91 ct.

Fig. 15. The blotchy coloration on the pavilion facets of the • • • radioactive diamond in Figure 11. Note also the intense green spots. 150 J. Gemm., 1986,20,3 3-16

~ U RADIUM Z TREATED Q§ DIAMOND o~ rJ1 CQ-e

-- 1 """ ~ 1-6 +-1 _ 1 '390 NANOMETRES 750

Fig. 14, The absorption curve of the radioactive green diamond in Figure II displaying a Cape series spectrum and a weak GRI band. The curve was obtained using a Pye Unicam PU8800103 UV/visible spectrophotometer (Basil Anderson model) with a speed of 0.5 nmls and a bandwidth of 0.5 nm at approximately 120 K.

Fig. 16. Autoradiograph produced by the green diamond in Fig. 17. Autoradiograph produced by the green diamond in Figure II when positioned with its table in contact with Figure II when positioned with a pavilion facet in X-ray film. Exposure time 16'/2 hours. contact with X-ray film. Exposure time 30 minutes. J. Gemm., 1986,20,3 151

A recent gift to the Laboratory collection is seen in Figure 18. It is a fibrolite (sillimanite), the identity of which has been confirmed by X-ray powder diffraction. The specimen is a 1.48 ct slice taken from a light yellowish water-worn crystal. The SGas determined by hydrostatic weighing, is 3.30 and the RIs are 1.660-1.682. Whilst the RI readings as determined on a Rayner Dialdex refractometer appear to be biaxial positive the difference between a and 13 is so small as to make this determination difficult.

Fig. 18. A 1.48 ct fibrolite specimen given to the Laboratory 2·0 collection.

Under both long-wave and short-wave ultraviolet light the stone fluoresces a weak orange. This fluorescence is stronger under long-wave ultraviolet than short-wave. The pleochroism is strong, the colours being yellow, light yellow and colourless. The absorption spectrum is shown in Figure 19 and the main absorption peaks are at 460.2, 440.8, 412.8, 389 and 360.8 nm. ~ *** U Z FIBROLITE We are fortunate in that at the same time as our < benefactor donated the fibrolite to the Laboratory lXl [SILLIMANITE] collection, he also gave us the opportunity to ~ examine an interesting specimen of taaffeite. o The stone, which is a bluish, smoky grey colour u: in daylight, is shown photographed in artificial light lXl in Figure 20. It weighs 0.70 ct and measures 5.19 x < 4.68 x 2.78 mm.

0·0 ~ 3~0 om

Fig. 20. Four examples of taaffeite. (i) A round faceted stone Fig. 19. The absorption curve of the fibrolite in Figure 18. The weighing 0.86 ct from the British Museum (Natural curve was obtained using a Pye Unicam PU8800/03 History) collection (BM 1967.309). (ii) A 0.70 ct stone UV/visible spectrophotometer (Basil Anderson model) belonging to Mark L. Jones, F.G.A. (iii) Rough ma­ with a speed of 0.5 nm/s and a bandwidth of 0.5 nm at terial weighing 2.78 cts from the BM (NH) collection room temperature. The path length was 2.39 mm. The (BM 1979.417). (iv) The 0,56 ct cushion-shaped, type main peaks in the curve are at 460.2, 440.8, 412.8, 389 specimen, owned by R.K. Mitchell, F.G,A. and on loan and 360.8 nm. to the Geological Museum. 152 J. Gemm., 1986,20,3

TAAFFEITE

~ U Z

325 NANOMETRES 750

Fig. 21. The spectra produced by the four taaffeites in Figure 20. Curve A is that of the rough specimen (Figure 21 iii), curve B is that of the specimen belonging to Mark L. Jones, F.G.A. (Figure 21 ii), curve Cis that of the type specimen (Figure 21 iv), and curve D is that of the round faceted stone (Figure 21 i). The peaks indicated by * are at a slightly different wavelength for each specimen. These are, A.385 nm , B.383.4 nm, C.384.4 nrn, D.384.8 nm. All curves were recorded under similar conditions using a Pye Unicam PU8800103 UV/visible spectrophotometer (Basil Anderson model) with a speed of I nrn/s for curves A, C and D and 0.5 nm/s for curve B. The bandwidth for each curve was 0.5 nm, the span 2A and each was recorded at room temperature. The path lengths were approximately A, 7.1 mm, B, 2.78 mm, C, 4.89 mm and D, 5.28 mm. J. Gemm., 1986, 20, 3 153

The refractive indices as determined with a Recently we were asked to examine a sample of Rayner Dialdex refractometer are 1.718-1.724 and synthetic diamond grit weighing 1.33 ct in which the SG obtained by hydrostatic weighing is 3.67. the average grain size was 0.4 mm (Figure 22). There is very little difference between the The sample was attracted to a hand magnet and, absorption spectrum produced by the ordinary ray as is normal for synthetic diamond grit, and that produced by the extraordinary ray. The the individual crystals were heavily included spectrum recorded at approximately 90° to the optic (Figure 22). It appeared also that the greater the axis is reproduced as (B) in Figure 21. By way of amount of inclusions the greater the reaction there comparison the spectra of three further taaffeites, was to the magnet. including the type specimen, (Figure 21), were The examination to estimate the percentage of examined under similar conditions. These spectra impurity present was carried out in the manner are also reproduced in Figure 21. described by Anderson(4). Two small samples from the larger sample were examined and the impurity percentages were found to be 9.78% and 0.78%. The impurity reacted strongly to a magnet.

Acknowledgements It is with pleasure that the Laboratory gratefully acknowledges the gift of the fibrolite from Mark L. Jones, F.G.A. We are also indebted to Mr Jones for the sight of his taaffeite specimen, and to Dr R.R. Harding, and Mr R.K. Mitchell, F.G.A., for Fig. 22. Heavily included synthetic diamond grit with an average allowing us to examine the spectra of the other three grain-size of 0.4 mm. specimens of taaffeite. Figures 1 and 2 were taken by Mr T.J. Rappitt, F.G.A., in 1981. As explained by Anderson in his book Gem Testing(4) the Laboratory on many occasions has been asked to examine diamond grits and powders, when dealers in industrial diamond have been concerned about the purity or grit size of lots they References propose to purchase. 1. Taburiaux, J. 1985. Pearls, Their Origin, Treatment and Although we are not asked quite so often Identification. NAG Press, Ipswich, England. 2. Kunz, G.F. and Stevenson, C.H. 1908. The Book of the Pearl. nowadays to examine these grits and powders, Macmillan and Co. Ltd., London. when we are they are usually composed of very fine­ 3. Scarratt, K. 1985. Notes from the Laboratory. J. Gemm., XIX, grained natural diamond and only occasionally are 8, 653. they synthetic diamond. When they have been 4. Anderson, B.W. 1980. Gem Testing, 9th edn, 239-41. synthetic diamond, the grain size has also been very Butterworths, London. small. [Manuscript received 14 April 1986.] 154 J. Gemm., 1986, 20, 3

Some observations on brown tourmalines from Elahera, Sri Lanka

Ulrich Henn and Martin Schramm

Institut für Edelsteinforschung, University of Mainz, West Germany

Abstract Ca Mg3 (Al5, Mg) [(OH)4(B03)3(Si6018)] - Uvite This paper deals with the description of brown Na Mg3 Al6 [(OH)4(B03)3(Si6018)] - Dravite tourmalines from Elahera, Sri Lanka. They were The occurrence of brown tourmalines of classified as uvite and dravite as a result of their gemstone quality in the Elahera area was mentioned chemical and optical properties. by Henn (1983), but more detailed studies were not made earlier. Introduction In the Sinhalese linguistic usage, the name Results tourmaline is applied as a generic term to a number For the analyses orientated slices from brown to of coloured gemstones. But the mineral tourmaline dark brown tourmaline crystals were cut and itself is relatively rare and it occurs exclusively in polished. The following values for the refractive the brown variety. Until now the known deposits indices and densities were measured: are located in the Uva region, in the Ratnapura Dravite Uvite district and in the Tissamaharma area (Dunn, 1977 n0= 1.640 nc= 1.635- 1.648 and Zwaan, 1982). These occurrences are always ne= 1.623 ne=1.619- 1.631 alluvial deposits. ne-no=-0.017 ne-no=0.016 - 0.021 All tourmalines are members of solid solution D-2.922 g/cm3 D=2.85 - 3.24 g/cm3 series with the general composition: XY3Z6 Under the microscope the tourmalines show their [(OH)4(B03)3(Si6018)] with X=Na, Ca; Y=Li, Al, characteristic unorientated feathers, consisting Mg, Fe, Mn; Z=A1, Fe, Mg. mostly of elongated fluid and two-phase inclusions. Analyses from Dunn (1977) classified the brown Furthermore orientated hollow tubes are present, tourmalines from Sri Lanka as uvite and dravite: which are often filled with two immiscible fluids. As

Fig. 1. Rounded zircon crystals in a brown tourmaline from Fig. 2. Rounded zircon crystals in a brown tourmaline from Elahera, Sri Lanka. (25x) Elahera, Sri Lanka. (125x) J.J. Gemm.,Gemm., 1986,20,31986, 20, 3 155155 mineraminerall inclusioninclusionss roundedrounded zirconzircon crystalcrystalss (Figs(Figs.. 1 andand 2)2) werweree observeobservedd andand theirtheir chemicachemicall composi­composi­ Uvite tiontionss analysedanalysed withwith ththee electronelectron microprobemicroprobe.. TheThe resultsresults araree listedlisted inin TablTablee 11..

TableTable 1.1. ElectroElectronn microprobmicroprobee analysesanalyses ofof zirconzircon inclusioninclusionss inin browbrownn tourmalinestourmalines fromfrom ElaheraElahera,, SriSri LankLankaa (W(Wtt %%)) Mg/Fe 50%

InclusioInclusionn 1 InclusionInclusion 2 InclusioInclusionn 3

Si02 29.729.766 32.432.422 29.829.800 A1Al22003 0.00.033 0.060.06 0.080.08 NaNa2020 0.00.011 - 0.020.02 CaOCaO - 0.040.04 - Schorl 50% Dravite Ti022 0.10.199 0.030.03 0.030.03 Mg/Fe V 0 - 0.100.10 0.0 0.044 v2o33 MnMnOO - 0.290.29 0.00.055 FeFeOO 0.510.51 0.60.600 0.5 0.544 FigFig.. 3 SystemSystem uvite-dravite-schoruvite-dravite-schorll witwithh samplessamples frofromm ElaheraElahera plottedplotted.. Zr0ZrOz2 71.7471.74 68.668.688 68.368.344 TotaTotall 102.25102.25 102.19102.19 98.9098.90 Uvite:Uvite: (Ca(Ca0O.&'-O.7,.6-o.7? NaNaO.2-0.4)0.2_o.4) (Mg2..7_- 33.4,.4, FeO.l-O.Z)Fe0.i_0.2) Al5s.4_.4--6.o6.o [(OHMB0[(OH)4(B033)MSi3(Si60181S))]] DraviteDravite:: TablTablee 2.2. ElectronElectron microprobmicroprobee analysesanalyses ofof brownbrown (Cao.3(CaO.3,, NaNao.S)0.5) (Mgz2.7 , FeO.3)Fe0.3) A\A16A6 . 1 [(OH)4[(OH)4 tourmalinetourmaliness frofromm ElaheraElahera,, SriSri LankLankaa (Wt(Wt %%)) (B033)MSi3(Si60 181S))]] Fig.Fig. 3 showsshows thethe placplacee ofof thethe tourmalinetourmaline samplessamples UvitUvitee frofromm ElaherElaheraa iinn thethe systemsystem uvite-dravite-schorl.uvite-dravite-schorl. variatiovariationn ououtt ofof AbsorptionAbsorption spectrspectraa ofof tourmalinetourmaliness werewere describeddescribed 1111 samplessamples averagaveragee DraviteDravite bbyy FayeFaye et al. (1968)(1968),, ManninManningg (1968)(1968),, FayFayee et al. (1974)(1974) anandd SmithSmith (1978).(1978). FigFig.. 4 showsshows absorptionabsorption SiOzSi0 36.95-37.736.95-37.766 37.437.455 37.1 37.133 2 spectraspectra witwithh varyingvarying orientationsorientations ofof uviteuvitess fromfrom Alz0A1 0 29.01-30.2129.01-30.21 29.6029.60 32.232.244 2 3 ElaherElaheraa inin polarizepolarizedd light.light. TheThe absorptioabsorptionn maximamaxima NaNa200 0.77-0.77- 0.980.98 0.880.88 1.591.59 2 anandd ththee correspondincorrespondingg charge-transfecharge-transferr processesprocesses KzOK 0 0.030.03-- 0.150.15 0.070.07 0.060.06 2 areare listedlisted iinn TableTable 3.3. ThThee absorptionabsorption bandband,, causedcaused MgMgOO 11.22-13.4511.22-13.45 12.2312.23 11.2711.27 bbyy ththee charge-transfecharge-transferr procesprocesss FeFe2+~Fe3+2+-^Fe3+ hahass oneone CaOCaO 3.80-A.133.80--4.13 3.93.933 1.961.96 maximummaximum atat 767600 nnmm foforr E||Elkc anandd ononee aatt 690690 nmnm forfor FeFeOO 0.640.64-- 1.501.50 1.111.11 0.780.78 ElcElc.. TheseThese absorptioabsorptionn bandsbands werewere observeobservedd iinn MnOMnO n.d.n.d.-- 0.070.07 0.040.04 0.040.04 Ti02 0.340.34-- 1,061,06 0.630.63 0.590.59 25 Total 85.93 Total 84.37-87.6884.37-87.68 85.93 85.6685.66 (%T)

ChemicaChemicall analyseanalysess ooff ththee tourmalinetourmaliness werweree alsoalso determinedeterminedd byby ththee electronelectron microprobmicroprobee (Table(Table 2)2).. WithWith ononee exceptionexception,, alalll examineexaminedd samplessamples areare uviteuvitess (Ca>Na(Ca>Na)) witwithh thethe uviteuvite formingforming 60.060.0 toto 77.877 .8%% ofof thethe crystalcrystal.. OnlOnlyy ononee samplesample waswas analysedanalysed aass a dravitedravite (CaNCa>Naa anandd Ca

TableTable 33.. AbsorptionAbsorption maximamaxima andand charge-transfercharge-transfer ReferencesReferences processeprocessess ooff browbrownn uvitesuvites fromfrom Elahera,Elahera, DunnDunn,, P.}.P.J. 1977.1977. Uvite,Uvite, A NewlNewlyy ClassifiedClassified GemGem TourmalineTourmaline.].. J. SriSri LankaLanka Gemm. 15,15, 300-8300-8.. Faye,Faye, G.H.G.H.,, Manning,Manning, P.GP.G.. andand NickelNickel,, E.HE.H.. 1968.1968. TheThe Polarized Optical Absorption Absorption Spectra Spectra of of Tourmaline, Tourmaline, Cordierite, Cordie­ absorptionabsorption charge-transfercharge-transfer Chloritoidrite, Chloritoid and Vivianite: and Vivianite: Ferrous-Ferric Ferrous-Ferric Electronic Electronic maximmaximaa (nm)(nm) processesprocesses InteractionInteraction aass a SourcSourcee ooff Pleochroism.Pleochroism. Amer. Miner. 5353,, 1174-1201.1174-1201. E||Ellec 767600 Fe2+-^Fe3+ FayeFaye,, G.H.,G.H., ManningManning,, P.G.,P.G., GosselinGosselin,, J.RJ.R.. anandd TremblayTremblay,, R.J.R.J. 1974.1974. TheThe OpticalOptical AbsorptioAbsorptionn SpectraSpectra ooff Tourmaline:Tourmaline: 500500 ImportanceImportance ofof Charge-TransfeCharge-Transferr Processes.Processes. Can. Mineral. 1212,, 460 370-380. 460 Fe2+^Ti4+ 370-380. 430 Henn,Henn, U.U. 1983.1983. EinschlüssEinschliissee inin EdelsteineEdelsteinenn auauss ElaheraElahera,, SriSri 430 LankaLanka.. Goldschmiede Zeitung, Zeitung, 11,11 ,76. 76 . ElElcc 690690 Fe2+--..."FeFe2+^Fe3H+ ManningManning,, P.GP.G.. 1968.1968. AnAn OpticaOpticall AbsorptioAbsorptionn StudyStudy ofof ththee OriginOrigin 444400 Fel+---'>TiHFe2+->Ti4+ ooff ColourColour anandd PleochroisPleochroismm iinn PinPinkk andand BrownBrown Tourmalines.Tourmalines. Can. Mineral., 99,, 678---90.678-90. brown and green tourmalines (Smith, 1978) and Smith,Smith, G.G. 1978.1978. A ReassessmenReassessmentt ooff ththee RoleRole ofof IronIron iinn thethe brown and green tourmalines (Smith, 1978) and -1 havhavee onlonlyy slightslight influencinfluencee oonn ththee colourcolour (Manning,(Manning, 5000-300005000-30000 cmcm ~ [ RegioRegionn ooff thethe ElectronicElectronic AbsorptioAbsorptionn SpectraSpectra ofof TourmalineTourmaline.. Phys. Chem. Minerals, 33,, 343-73343-73.. 1968).1968). ThThee absorptionabsorption responsibleresponsible foforr thethe brownbrown ZwaanZwaan,, P.e.P.C. 1982.1982. SriSri LankaLanka:: TheThe GemGem IslandIsland.. Gems Gemol. coloucolourr hahass a maximumaximumm atat 444400 nnmm foforr ElcElc.. AAtt ElleE||c 18,18, 62-71.62-71. thisthis bandband splitsplit inin threthreee maximamaxima atat 500,500, 464600 andand 430430 nm.nm. ItIt isis causecausedd byby ththee charge-transfecharge--transferr processprocess [Manuscript[Manuscript receivedreceived 4 4 July July 1985.]1985. ] Fe'+---'>TiHFe2+^Ti4+ (Smith,(Smith, 1978)1978).. J]. . Gemm.Gemm.,, 19861986,, 2020,3, 3 151577

A re-investigationre-investigation ofof gahnospinelsgahnospinels fromfrom SriSri LankaLanka

ByBy DrDr Karl Karl Schmetzer* S chmelzer* andand Prof.Prof. DrDr Hermann Hermann BanktBank†

*Institut*Institulee ooff Mineralog Mineralogyy anandd PetrographyPetrography,, UniversitUniversityy ooff Heidelberg ,, WesWestt GermanGermanyy anandd DeutschDeutschee StiftunStiftungg EdelsteinforschungEdelsteinforschung,, Idar-ObersteinIdar·Oberstein,, WesWestt Germany.. †Idar-Obersteintldar-Oberstein,, WesWestt GermanGermanyy

AbstracAbstractt ThThee chemicachemicall compositiocompositionn anandd physicaphysicall propertiepropertiess ooff zinciazinciann spinelspinelss (gahnospinels(gahnospinels)) frofromm SrSrii Lankaa werweree re-investigatedre-investigated.. ThThee samplesampless werweree founfoundd ttoo represenrepresentt intermediatee membermemberss ooff ththee spinelgahnitspinelgahnitee solisolidd solutiosolutionn serieseriess witwithh minominorr componentcomponentss o ff hercynitehercynite.. RefractiveRefractive indiceindicess anandd densitiedensitiess ooff ththee samplesampless araree closelcloselyy correlatecorrelatedd ttoo ththee moleculamolecularr proportionss ooff ththee gemstonesgemstones.. ColourColour, absorptionabsorption spectra, spectra and, and inclusions inclusion ofs o zinc-bearingf zinc-bearing gahnospinels gahno­ spinels werweree founfoundd ttoo bbee similasimilarr ttoo ththee propertiepropertiess ooff ordinarordinaryy zinc-frezinc-freee spinels frofromm SrSrii Lanka.. ThThee datdataa publishepublishedd bbyy AndersoAndersonn et alal.. (1(1937937) as wellwell as the eexistencxistencee ooff a continuoucontinuouss solisolidd solutiosolution serieseriess betweebetweenn spinespinell anandd gahnite,, whicwhichh wawass alsalsoo assumeassumedd bbyy AndersoAnderson anandd hihiss co-workers,co-workers, were were confirmed confirmed by b thesey the investigations.se investigatio ns. Fig. 1I. GahnospinelGahnospinels frofromm SSrrii Lanka.Lanka. SizeSize oohhf thee samplesampless appr approxox. . 8 x 1010 mm.mm. PhPhotooro b yby O O.. M Medenbach,edenbach, Boc humBochum,, FRG FRG..

AluminouAluminouss magnesium-zinc-spinelmagnesium-zinc-spinelss frofromm SriSri TablTablee 1:1: SelectedSelected physicaphysicall anandd chemicalchemical LankaLanka werewere first describeddescribed bbyy AndersonAnderson et aial.. propertiepropertiess ooff gahnospinelsgahnospinels fromfrom SriSri Lanka*Lanka* (1937(1937)). TheThe densities andand refractivrefractivee indicesindices ooff 2222 samplessamples werweree founfoundd toto rangrangee fromfrom 33.58.5844 toto 33 3 d (glcm(g/cm ) n ZnO(~~)FeO(wt%)ZnO(wt%)FeO(wt< 3.9813.981 gg/cm/cm3 andand fromfrom 1.71531.7153 toto 1.7469,1.7469, respec­respec­ tively. OneOne samplesample waswas chemicallychemically analysedanalysed con­con­ 1 33.6.600 1.7161.716 0.14(U4 2.342.34 tainingtaining majormajor amounts ofof Ah03,A1203, ZnOZnO andand FeOFeO 2 3.60 1. 715 0.86 2 3.60 1.715 0.86 1.341.34 ((TablTablee 11)).. TheThe analysisanalysis representsrepresents a membermember ofof thethe 3 3.72 1.723 7.18 1.92 3 3.72 1.723 7.18 1.92 aluminousaluminous spinelspinel solidsolid solutionsolution seriesseries withwith dominantdominant 4 3.75 1.724 7.36 4 3.75 1.724 7.36 1.691.69 molecularmolecular percentagpercentageeSs ofof thethe idealizeidealizedd "endend membersmembers 5 33.7.777 1.7311.731 10.2710.27 2.522.52 spinelspinel MgAl 2004 ((62.4%62.4%)) andand gahnitegahnite ZnAl2004 6 3.80 1.733 11.55 z 4 z 4 6 3.80 1.733 11.55 1.741.74 (33(33.5%).5%),, asas wellwell as subordinatesubordinate percentagespercentages ofof 7 33.8.866 1.7371.737 12.9812.98 1.471.47 hercynitehercynite FeAl 2004 ((4.1%)4.1 %).. AccordingAccording toto a proposalproposal 8 4.00 1.741 18.74 0.78 z 4 8 4.00 1.741 18.74 0.78 ofof AndersonAnderson et aial.. (1937(1937)),, zinc-bearingzinc-bearing spinelsspinels areare A 3.967 1.7465 18.21 1.93 3.967 1.7465 18.21 1.93 termedtermed zincianzincian spinelsspinels oror gahnospinelsgahnospinels inin thethe 9 4.05 1.752 24.81 9 4.05 1.752 24.81 1.901.90 literature.literature. B 4.060 1.7542 not analysed B 4.060 1.7542 not analysed SinceSince thatthat timetime gahnospinelsgahnospinels havehave beenbeen frequentlyfrequently encounteredencountered inin thethe gemmologicalgemmological laboratorylaboratory ofof thethe * forfor complcompletetee chemicalchemical datadata seesee SchmetzerSchmetzer & LondonLondon ChamberChamber ofof Commerce.Commerce. However,However, onlyonly BankBank (1985(1985) oneone samplesample waswas rerecognizecognizedd afterafter 2525 yearsyears ofof reresearchsearch,, whichwhich exceededexceeded thethe rangerange forfor refractiverefractive A samplesample analyanalysesedd byby AndersonAnderson etet al.al. (1937(1937) indiceindices andand densitiesdensities aass dedescribescribedd inin thethe ((19371937)) paperpaper ((AndersonAnderson,, 19641964)).. ThisThis samplesample showedshowed B samplesample describeddescribed byby AndersonAnderson (1964(1964)) withwith outstandinglyoutstandingly highhigh figuresfigures forfor densitydensity andand refractiverefractive extraordinarilyextraordinarily highhigh valuesvalues forfor densitydensity andand indexindex ((TablTablee 1)1) indicatingindicating anan intermediateintermediate member.member refractiverefractive indexindex ofof thethe isomorphouisomorphous spinel-gahnitespinel-gahnite solidsolid solutionsolution

©© CopyrightCopyright thethe GemmGemmologicaologicall AAssociatiossociationn ISSN:ISSN: 0022-12520022-1252 158158 ].J. Gemm.Gemm.,, 1986,1986, 2020,, 3

seriesseries withwith moleculamolecularr proportionsproportions ofof approximatelyapproximately indicesindices anandd densitiedensitiess areare founfoundd ttoo bebe withiwithinn thethe 50%50% eaceachh oftheof the gahnitgahnitee andand thethe spinelspinel enendd member.member. rangrangee ooff ththee values publishepublishedd bbyy AndersoAndersonn et al. AccordinAccordingg ttoo thethe physicaphysicall datadata ooff AndersonAnderson et al. (1937(1937)) anandd AndersoAndersonn (1964)(1964).. TheThe consistencconsistencyy ooff (1937),(1937), thertheree iiss nono evidenceevidence forfor a miscibilitymiscibility gapgap thesthesee propertiesproperties (Figur(Figuree 2)2) maymay indicateindicate samplesampless ooff betweenbetween botbothh enendd membersmembers ooff ththee solidsolid solutionsolution similarsimilar chemicalchemical compositioncompositionss iinn botbothh investiga­investiga­ series,series, spinelspinel andand gahnitegahnite.. However,However, chemicalchemical datadata tionstions.. OuOurr microprobmicroprobee analysesanalyses indicateindicate thatthat thethe ooff onlyonly oneone samplesample araree availableavailable iinn ththee literature.literature. spinelsspinels represenrepresentt intermediatintermediatee membermemberss ofof thethe ThereforeTherefore,, furthefurtherr investigationinvestigationss ofof chemicachemicaIl andand spinelgahnitespinelgahnite seriesseries withiwithinn a compositionacompositionall rangrangee ooff physicaphysicall propertiepropertiess ofof gahnospinelsgahnospinels frofromm SriSri LankaLanka thethe predominanpredominantt enendd membermemberss spinelspinel (95.1-(95.1- werewere carriecarriedd ououtt iinn orderorder toto completcompletee ththee presentpresent 45.345.3 mol%mol%)) anandd gahnitegahnite (0.2-50.4(0.2-50.4 mol%mol%)) withwith knowledgeknowledge onon intermediatintermediatee membermemberss ofof ththee spinel­spinel­ minominorr componentscomponents ofof hercynithercynitee (1.7-5.4(1.7-5.4 mol%)mol%).. gahnitegahnite solidsolid solutionsolution seriesseries (Schmetzer(Schmetzer & Bank,Bank, ThThee physicaphysicall propertiesproperties areare closelyclosely correlatecorrelatedd ttoo thethe 1985).1985). molecularmolecular proportionproportionss ooff ththee samples,samples, i.ei.e.. anan AlAlll samplessamples availablavailablee toto thethe authorsauthors werewere trans­trans­ increasincreasee ooff botbothh densitydensity andand refractivrefractivee indeindexx iiss parentparent,, cutcut blueblue,, bluish-violebluish-violett oorr violeviolett materialmaterialss ooff causecaused·d bbyy aann increasingincreasing Zn-componentZn-component iinn thethe gemgem qualitqualityy (Figure(Figure 1).1). MosMostt ofof ththee materialmaterial wawass spinel-gahnitespinel-gahnite solidsolid solutionsolution series.series. TheseThese physicalphysical selectedselected frofromm cutcut gemgem spinelsspinels ofof ordinarordinaryy parcelsparcels datdataa areare alsalsoo influencedinfluenced bbyy ththee slightlyslightly variablevariable originatinoriginatingg frofromm SriSri LankaLanka.. ThereforeTherefore,, nono furtherfurther hercynitehercynite percentagepercentagess ofof ththee samplessamples (Tabl(Tablee 1,1, detaildetailss aboutabout ththee exactexact localitielocalitiess forfor thethe zmClanzincian FigurFiguree 2)2).. spinelsspinels araree available.available. TheThe coloucolourr ofof gahnospinelgahnospinelss frofromm SriSri LankaLanka SelectedSelected chemicachemicall andand physicalphysical datdataa ooff thethe (Figur(Figuree 1)1) iiss identicalidentical withwith ththee coloucolourr variationvariation samplessamples areare summarizedsummarized iinn TablTablee 1.1. RefractiveRefractive observeobservedd foforr ordinaryordinary blueblue,, bluish-violebluish-violett andand violet

4.10

4.00 d [g/cm3j 390 +.,t l:::,.13.0 3.80 +611.6 7.1. ~ ~ 10.3 7.2~ t 3.70 + #+ 3.60 o.9~=tf 0.1 1.71 1.72 1.73 1.74 1.75 1.76 n

FigFig.. 22.. PlotPlot ofof densitiesdensities vvss refractiverefractive indiceindicess ooff gahnospinelgahnospinelss fromfrom SriSri Lanka;Lanka; + indicatesindicates samplessamples describeddescribed bbyy AndersoAndersonn eletal. al. (1937),(1937), E8© indicatesindicates thethe samplsamplee witwithh extraordinarilextraordinarilyy highighh values foforr densitydensity anandd refractiverefractive indeindexx describedescribedd bbyy AndersonAnderson (1964)(1964),6, A indicatesindicates samplesampless ooff SchmetzerSchmetzer & BanBankk (1985);(1985); thethe figures indicateindicate weightweight percentagepercentagess ooff ZnO.ZnO. J. Gemm., 1986, 20, 3 159

Fig. 3 Stringers of small particles in gahnospinel from Sri Lanka. Fig. 4. Stringers of small particles in gahnospinel from Sri 45x. Lanka. 5Ox.

Fig. 5. Two octahedral crystals, one of them surrounded by a Fig. 6. Octahedral crystal in gahnospinel from Sri Lanka. 80x. liquid feather, and one negative octahedron (middle) in gahnospinel from Sri Lanka. 60x.

Fig. 7. Rounded mineral inclusions, most probably apatites, in Fig. 8. Rounded mineral inclusion in gahnospinel from Sri gahnospinel from Sri Lanka. lOOx. Lanka. 65x. 160 J. Gemm., 1986, 20, 3 gem spinels from Sri Lanka. The absorption complete solid solution series with major compo­ spectra of gahnospinels and ordinary spinels do not nents of spinel and gahnite and minor components show any significant differences. According to of hercynite. At present, the compositional range of Dickson & Smith (1976) the absorption bands of gahnospinels from Sri Lanka is found to vary within natural blue spinels in the visible area are mainly the aluminous spinel solid solution series from due to spin-forbidden transitions of tetrahedrally about 95 to 45 mol% spinel, and from août 0.2 to co-ordinated Fe2+. Thus, the colour of spinels of 50 mol% gahnite with hercynite components of unknown composition, e.g. of rough spinels, is of about 2-5 mol%. No significant difference is found no diagnostic value for a distinction between between the absorption spectra and colour of ordinary spinels and gahnospinels. gahnospinels and ordinary gem spinels from Sri The inclusions observed in gahnospinels from Sri Lanka nor between the inclusions in zinc-containing Lanka do not reveal any extraordinary properties and zinc-free samples. compared to the inclusions which are common for ordinary gem spinels from this country (Figures 3- 8). Most frequently stringers of small particles, either in straight lines or as fingerprints, were found. Individual octahedra, occasionally sur­ rounded by a liquid feather, as well as mineral References inclusions of various shapes were observed. In two Anderson, B.W. 1964. Three Stones for the Record. J. Gemm., samples, one solid inclusion was exposed on the IX, 7, 215-21. table of the cut gemstone in each case. Both Anderson, B.W., Payne, C.J. & Hey, M.H. 1937. Magnesium- inclusions were determined as apatite by microprobe zinc-spinels from Ceylon. Mineral. Mag., 24, 547-54. analysis. Dickson, B.L. & Smith, G. 1976. Low-temperature optical absorption and Mössbauer spectra of staurolite and spinel. The chemical composition and the physical data Canad. Mineral., 14, 206-15. of gahnospinels from Sri Lanka confirm the Schmetzer, K. & Bank, H. 1985. Crystal chemistry of zincian assumptions of, Anderson et al. (1937). These spinels (gahnospinels) from Sri Lanka. N. Jb. Miner. Mh., authors suggested that transparent blue or violet 1985, 8, 353-6. gem spinels from Sri Lanka with extraordinary high densities and refractive indices are members of a [Manuscript received 18 June 1985.] J.J. GemmGemm..,, 1986,20,31986, 20, 3 161161

SomeSome unusualunusual cat's-eyescat's-eyes

Yasuhirolto,Yasuhiro Ito, G.G.,F.G.AG.G., F.G.A..

Osaka,Osaka, JapanJapan

ChatoyancChatoyancyy addaddss beautbeautyy anandd rarityrarity ttoo a gemstone.gemstone. 'eyes'eyes'' araree usuallusuallyy broabroadd andand dulldull,, andand theythey cancan oftenoften SomeSome chatoyanchatoyantt gems,gems, suchsuch asas zirconzircon,, tanzanitetanzanite bebe identifieidentifiedd atat sightsight andand withoutwithout ththee useuse ooff anandd opal,opal, maymay commancommandd a veryvery highhigh priceprice,, bubutt theythey instruments.instruments. araree notnot necessarilnecessarilyy beautifulbeautiful.. InIn thithiss shortshort reporreportt I InIn 19841984 I obtaineobtainedd a 0.70.733 cctt stone,stone, reputedlyreputedly shallshall describdescribee threthreee unusuaunusuall cat's-eyescat's-eyes frofromm mymy frofromm SriSri LankaLanka.. ThisThis hahass a beautifubeautifull yellowish­yellowish- collection.collection. greengreen colourcolour anandd a veryvery sharpsharp eyeeye duduee toto a goodgood fibrous structurestructure (Figure(Figure 1).1). ThThee stonestone resemblesresembles Sillimanite cat's-eyescafs-eyes (whic(whichh araree nonoww available)available) chrysoberychrysoberyll cat's-eycat's-eyee ofof googoodd quality,quality, soso chatoyantchatoyant araree mostlymostly frofromm IndiaIndia.. SeriousSerious collectorcollectorss cancan sillimanitesillimanite nonoww hahass ttoo bbee considereconsideredd aass a chrysoberylchrysoberyl usuallusuallyy obtainobtain themthem.. TheyThey areare commonlcommonlyy greyish­greyish- simulant.simulant. TheThe stonestone wawass identifieidentifiedd aass sillimanitesillimanite greegreenn iinn colourcolour,, witwithh blacblackk inclusioninclusionss proveprovedd ttoo bebe frofromm ththee refractivrefractivee indeindexx (1.6(1.677 bbyy ththee distandistantt vision magnetitmagnetitee anandd hematithematitee (Zwaan,(Zwaan, 1982). ThereThere methodmethod)) anandd ititss X-raX-rayy diffractiodiffractionn data.

FigFig.. 1I.. SillimanitSillimanitee (fibrolite(librolite)) cat's-eyecat's-eye,, 0.70.733 ctct.. FigFig.. 22.. KyanitKyanitee cat's-eycat's-eyee witwithh tubulatubularr inclusionsinclusions..

FigFig.. 33.. TubulaTubularr inclusioninclusionss iinn kyanitkyanitee cat's-eyecat's·eye.. FigFig.. 44.. PetalitPetalitee cat's-eycat's-eyee possiblpossiblyy frofromm SoutSouthh AfricaAfrica,, 17.017.033 ctct..

© CopyrighCopyrightt ththee GemmologicalGemmological AssociatioAssociationn ISSNISSN:: 0022-12520022-1252 162 J. Gemm., 1986, 20, 3

Kyanite cafs-eye came into my possession in 1984 South Africa is sometimes cut en cabochon and may when I bought a few cabochons. They all had a royal show chatoyancy. Petalite-analcime cat's-eyes, trans­ blue colour but were of low quality due to heavy lucent and pinkish-brown in colour, have been cleavage and inclusions. One flat cabochon weighing found (Bank, 1982) in Zimbabwe. My stone 5.26 ct (Figure 2) shows chatoyancy. It shows (Figure 4) is pink, and no analcime lines were found prominent cleavages and tubular inclusions running in the X-ray diffraction pattern. Thus, this stone at right angles to the cleavages (Figure 3). The may be described as petalite cat's-eye, maybe from chatoyancy could be due to the tubular inclusions, South Africa. and as these are coarse the 'eye' is not very sharp, I wish to thank Mr S. Kinoshita, Mr S. Kihara although it can be seen under a normal fluorescent and Mr K. Kuraya for their kind and useful advice, lamp without a penlight. Such a stone is a collectors' and Mr S. Fujiwara for taking X-ray diffraction item only and is useless for jewellery on account of photographs. its fragility and inclusions. Petalite cafs-eye was sold to me as analcime from an unknown locality. This pretty pale pink stone weighs 17.03 ct, is almost opaque and massive, but References possesses a sharp but superficial chatoyancy. The Bank, H. 1982. Petalite-analcime cat's-eyes from Zimbabwe. refractive index was determined as 1.50 by the Z.Dt.Gemmol.Ges.,31, 3, 193-4. distant vision method. The X-ray diffraction data Zwaan, P.C. 1982. Sillimanite cat's-eyes from Kangayam, proved the stone to be petalite. Madras, India. J.Gemm., XVIII, 4, 277-81. Petalite in the gem market is usually colourless [Manuscript received 26 July 1985, revised 31 January and transparent, but massive pink material from 1986.] J.J. Gemm.,Gemm., 1986,20,31986, 20, 3 163163

A peculiarpeculiar inclusioninclusion inin a yellowyellow corundumcorundum fromfrom MalawiMalawi

Prof. Odino Grubessi* and Dr Renata Marconi M arcont†

*Dipartimento*Dipartimento didi ScienzeScienze delladella Terra,Terra, UniversitilUniversità deglidegli StudiStudi didi Roma,Roma, Rome,Rome, ItalItalyy tlstituto†Istituto GemmologicoGemmologico Italiano,Italiano, Rome,Rome, ItalyItaly

InIn anan investigationinvestigation ofof a yelloyelloww crystalcrystal ofof MalawiMalawi ature.ature. OnOn thethe leftleft oneone cancan seesee thethe primaryprimary inclusioninclusion corundumcorundum (gemmological(gemmological andand chemicalchemical character­character­ atat temperaturetemperature T 44;; whenwhen temperaturetemperature decreasesdecreases ththee isticsistics areare summarizedsummarized inin TableTable 1),1), a syngeneticsyngenetic neckingnecking-dow -downn processprocess taketakess placplacee [T 33 andand T T 212] andand inclusion,inclusion, wherewhere 'necking-down''necking-down' tooktook placeplace afterafter causescauses thethe formationformation ofof separateseparate inclusionsinclusions whichwhich inin trapping,trapping, waswas observed.observed. TheThe necking-downnecking-down processprocess ourour casecase containcontain bothboth a liquidliquid andand a gaseousgaseous phasephase cancan taketake placplacee afterafter thethe formationformation ofof crystalscrystals anandd [Td·[T,]. primarprimaryy inclusions,inclusions, butbut atat highhigh temperaturetemperature anandd SuchSuch inclusionsinclusions areare notnot unusual;unusual; theythey havehave beenbeen pressurepressure onlyonly (Roedder,(Roedder, 1984).1984). observedobserved inin amethystsamethysts fromfrom NortNorthh CarolinaCarolina (USA),(USA), IndeedIndeed inclusionsinclusions withwith largelarge surfacesurface areasareas veryvery sapphiressapphires fromfrom MontanaMontana (USA),(USA), andand inin manymany otherother oftenoften tendtend toto splitsplit intintoo twotwo oror moremore separateseparate parts,parts, minerals.minerals. andand eveneven toto causecause apparentlyapparently isolatedisolated inclusionsinclusions iinn FiguresFigures 2-72-7 showshow photographphotographss ofof thethe corundumcorundum thethe hosthost mineral.mineral. SuchSuch inclusionsinclusions maymay containcontain takentaken underunder differentdifferent conditionsconditions studied.studied. FromFrom ththee solid,solid, liquidliquid oror gaseousgaseous phasephasess oror theirtheir mixtures.mixtures. necking-downnecking-down processprocess twtwoo cavitiescavities connectedconnected byby aa FigureFigure 1 schematicallyschematically showsshows thethe developmentdevelopment ofof thinthin hollowhollow andand surroundedsurrounded byby otherother smallsmall cavities,cavities, necking-downnecking-down withwith timetime byby decreasingdecreasing thethe temper-temper­ apparentlyapparently isolated,isolated, werewere formed.formed.

Time and decrease in temperature __

T1

Fig.Fig. I.1. SchematicSchematic developmentdevelopment ofof 'necking-down'necking-down' inclusioninclusion..

© Copyright the Gemmological Association ISSN: 0022-1252 TSSM-nfm-i-K-) (C) Convrieiir the Gfmmnlnairnl Assnrifltinn 164 J. Gemm., 1986, 20, 3

Fig. 2. The 'necked-down' three-phase inclusion. Within the Fig. 3 The external fingerprint inclusion and the triangular or cavity are seen the thin radiating needles, the gaseous tetrahedral nuclei of crystallization show better. Reflected phase and the small nuclei of crystallization. A fingerprint illumination. 20x. surrounds the three-phase inclusion. Direct illumination. 18x.

Fig. 4. This picture shows the moving of a vapour bubble nearer Fig. 5. The vapour bubble disappears owing to its re-absorption the trapping. Direct illumination, polarized light. 40x. in the canal connecting the two cavities. Direct illumina­ tion, polarized light. 40x.

Fig. 6. The bigger part of the 'necked-down' inclusion, with Fig. 7. The same subject as Figure 6. The needle-shaped thin radiating and crossed needles and small traingular or inclusions are a reddish-golden colour; they are probably tetrahedral nuclei of crystallization. Direct illumination, rutile. Reflected illumination. 70x. closed diaphragm. 70x. J. Gemm., 1986, 20, 3 165

Table 1: Properties of yellow corundum The two largest cavities, surrounded by a (Malawi) fingerprint, can be considered as a single inclusion. It contains three phases: a solid phase formed by thin radiating biréfringent needles (possibly Ti02); COLOUR yellow a liquid phase (possibly C02) and a gaseous phase LUSTRE vitreous outlined by a moving bubble (upper left in Figure 2) HARDNESS 9 which disappears (homogenizes) by heating at DENSITY 4.00 g/cm3 31°-32°C. OPTICS n(0 = 1.769 ny = 1.759 Within the largest cavity, small triangular or BIREFRINGENCE 0.010 tetrahedral markings (Figures 5, 6) can be seen; PLEOCHROISM none they are likely to be small nuclei of crystallization. ABSORPTION/ absorption band at 690-700 SPECTRUM nm (hand spectroscope) LUMINESCENCE UVL-yellow weak: UVS -none INCLUSIONS three-phase inclusion, cavi­ Acknowledgements ties, fingerprint inclusion, The Authors wish to thank Professor E. Roedder fractures, twins for helpful suggestions. The work was supported by Centro di Mineralogia e Petrologia delle Formazioni Ignée, C.N.R., Italia 1984. Chemical analysis EDAX

A1203 97.83 Reference Fe203 0.82 Roedder, E. (ed.). (1984) Fluid inclusions. Reviews in Mineralogy. MnO 0.02 Min. Soc. of America. MgO 0.89 [Manuscript received 10 July 1985,revised 10 February Na20 0.22 CaO 1986.] K20 0.03 Cr203 0.04 NiO 0.02 CuO 0.10 CoO H20 Total 99.97 166166 JJ.. Gemm.Gemm.,, 1986,20,31986, 20, 3

TheThe veryvery sphinxsphinx ofof diamondsdiamonds

A.E. Farn, F.G.A.F.G.A.

Seaford,Seaford, EasEastt Sussex,Sussex, BN2BN255 3H3HPP

AAss a gemmologistgemmologist I havhavee alwayalwayss hahadd a lovelove ooff bothboth LaboratorLaboratoryy rulerule.. I was facedfaced witwithh twtwoo majormajor colouredcoloured anandd colourlescolourlesss stones.stones. I believebelievedd inin mmyy changechangess ttoo accept,accept, andand ttoo teacteachh ttoo neneww staff.staff. earlyearly daysdays thathatt gemmologgemmologyy waswas principallprincipallyy aboutabout FashionFashionss changechange iinn gemsgems,, commercialcommercial outloooutlookk andand colouredcoloured stones.stones. ColourlesColourlesss stones,stones, suchsuch aass purepure iinn policiespolicies.. IInn mmyy earlieearlierr daydayss wwee seldomseldom lookelookedd atat examplesexamples ofof berylberyl,, quartzquartz,, topaztopaz andand corundum,corundum, diamondsdiamonds becausbecausee diamondiamondd merchantsmerchants diddid notnot needneed laclackk thatthat subtlesubtle touchtouch ofof impurityimpurity soso carelesslcarelesslyy andand ourour helphelp ttoo teltelll themthem theirtheir stonesstones werewere diamonds.diamonds. inadequatelinadequatelyy bestowebestowedd bbyy nature.nature. JustJust a littllittlee touchtouch YelloYelloww oorr browbrownn diamonddiamondss werewere nonott veryvery saleablesaleable ooff chromiumchromium altersalters considerablyconsiderably ththee berylberyl,, thethe anyway.anyway. MucMuchh ooff ththee earlearlyy workwork bbyy AndersonAnderson onon corundumcorundum oror thethe topaztopaz.. HoweverHowever,, aass a gemmologist,gemmologist, II ththee absorptioabsorptionn spectraspectra ofof diamondsdiamonds,, togethetogetherr withwith founfoundd thatthat tradtradee laboratorlaboratoryy practicpracticee demandeddemanded a C.Jc.J.. Payne'Payne'ss contributioncontribution onon thethe zoningzoning ofof naturalnatural knowledgknowledgee ooff alalll kindkindss andand colourcolourss ofof gemstones,gemstones, browbrownn diamond,diamond, anandd Webster'Webster'ss workwork onon fluores­ whethewhetherr amorphousamorphous oorr crystallinecrystalline,, opaquopaquee oror cencecence anandd phosphorescencphosphorescencee underunder X-rayX-ray excitationsexcitations transparenttransparent,, organiorganicc oror inorganicinorganic.. IInn ththee LaboratoryLaboratory I formedformed a tremendoutremendouss fundfund ofof knowledge.knowledge. ThisThis hadhad a lovellovelyy longlong rurunn ooff testingtesting colourecolouredd stonesstones yearyear knowledgeknowledge wawass puputt toto goodgood ususee laterlater whewhenn peoplepeople afteafterr yearyear anandd becambecamee proficienproficientt iinn thethe ususee ooff thethe becambecamee moremore awarawaree ofof colourcolour inin diamonds.diamonds. OOrr wawass microscopemicroscope,, spectroscopespectroscope andand thethe x 1010 lens.lens. BecauseBecause II iitt diversiondiversion ooff moneymoney ttoo a neneww formform ofof hedghedgee againstagainst wawass soso busbusyy witwithh colourecolouredd stonesstones I waswas somewhatsomewhat inflationinflation?? detachedetachedd fromfrom whatwhat wawass reallreallyy ouourr raison d' d'etre, etre, that that TwoTwo factorfactorss foforr mmee hahadd changed.changed. PearlPearlss had toto bebe iiss ttoo say,say, pearls. mymy metiersmetiers anandd wewe had ttoo acceptaccept diamonddiamond gradinggrading MyMy worlworldd thoughthough waswas ooff gemstonesgemstones,, colouredcoloured forfor aass parpartt ofof a LaboratorLaboratoryy service.service. WeWe becambecamee thethe preference,preference, withwith hardhard ttoo find inclusioninclusionss whichwhich werewere CIBJCIBJOO recognizedrecognized LaboratorLaboratoryy forfor diamonddiamond grading,grading, hallmarkshallmarks inin thatthat sphere.sphere. TheThe absorptionabsorption spectraspectra ooff andand pearpearll anandd colourecolouredd stonestone testingtesting,, inin GreatGreat gemstonesgemstones examinedexamined bbyy ththee hanhandd spectroscopespectroscope BritainBritain.. (Beck(Beck prismprism)) andand measuremeasuredd bbyy thethe BeckBeck wavelengthwavelength IInn pearpearll testingtesting bbyy X-raX-rayy methods,methods, thathatt iiss ttoo saysay measurinmeasuringg spectroscopespectroscope werweree ththee toolstools ooff thethe trade.trade. radiography,radiography, wwee ofteoftenn X-rayeX-rayedd piecepiecess ooff jewelleryjewellery WWee werewere testintestingg arounaroundd 6060 000000 pearlpearlss annually,annually, setset witwithh pearlspearls.. OOnn ththee negativenegative filmfilm,, duedue toto thethe withwith a tremendoustremendous peapeakk ofof somesome 100000100 000 pearlspearls inin massmass densitydensity ofof metalmetal,, i.ei.e.. golgoldd oror silver,silver, thethe mountmount ononee particularparticular year.year. PearlPearlss werewere,, anandd stillstill are,are, a veryvery itselfitself woulwouldd standstand ououtt iinn sharpsharp relierelieff comparedcompared withwith importanimportantt parpartt ofof thethe LaboratorLaboratoryy worworkk andand income.income. thethe greategreaterr transparencytransparency ofof ththee pearlpearlss (calcium(calcium HoweverHowever,, witwithh ththee retirementretirement ofof AndersonAnderson,, PaynePayne carbonate)carbonate).. TheThe strikingstriking featurefeature ooff manmanyy ooff thesethese andand Webster,Webster, mmyy enjoyablenjoyablee gemmologicagemmologicall (stone(stone piecespieces ooff jewellerjewelleryy whichwhich containedcontained diamonddiamondss also,also, testingtesting)) daysdays werewere numbered.numbered. I switchedswitched toto pearlpearl wawass thathatt ththee diamondsdiamonds werweree allall transparentransparentt ttoo XX­- testingtesting,, simplysimply becausbecausee atat thatthat timetime witwithh LaboratoryLaboratory raysrays.. ThiThiss gavegave thethe picturpicturee oorr radiographradiograph thethe movesmoves anandd stafstafff retirementretirementss thertheree wawass nnoo ononee elselsee toto appearanceappearance ofof emptyempty settings.settings. InIn thisthis mannermanner ddoo ththee jobjob.. althoughalthough notnot requested,requested, wwee inadvertentlinadvertentlyy provedproved InIn mmyy annuaannuall reporreportt I wrotwrotee ooff thethe 'wind'wind ooff ththee diamonds.diamonds. ThThee pearlpearlss coulcouldd bbee mucmuchh moremore change'change',, borrowingborrowing ththee phrasphrasee fromfrom oneone ofof ourour difficult!difficult! BecausBecausee ofof soso mucmuchh concentrationconcentration onon pearlpearl PrimePrime MinisterMinisterss whowho shallshall bebe namelessnameless.. TheThe windwind testintestingg bbyy opticaopticall anandd X-raX-rayy methodmethodss I becamebecame ofof changechange certainlcertainlyy blew,blew, anandd ononee wonderswonders whetherwhether specializedspecialized andand inin mymy retiremenretirementt havhavee givegivenn talkstalks onon changechange isis sometimessometimes forfor bettebetterr oror iiss ttoo bbee deplored.deplored. pearlspearls.. ForFor ththee majomajorr portioportionn ofof mymy gegemm testintestingg liflifee anandd forfor WritingWriting recentlrecentlyy upouponn pearlspearls,, I consulteconsultedd variousvarious thethe entireentire lengtlengthh ofoftha thatt ofof mmyy colleaguecolleaguess Anderson,Anderson, ofof myoIdmy old bookbookss uponupon gemstonegemstoness includinincludingg 'Pearls'Pearls PaynePayne anandd Webster,Webster, wwee neveneverr gavgavee opinionopinionss oror andand PearlinPearlingg Life',Life', bbyy EdwiEdwinn WW.. StreeterStreeter (London,(London, examinedexamined diamonddiamondss foforr colourcolour oorr puritypurity.. ThaThatt waswas a 1886).1886). LaterLater,, needinneedingg toto consultconsult thithiss bookbook againagain,, I

© CopyrightCopyright thethe GemmologicalGemmological AssociationAssociation ISSN:ISSN: 0022-12520022-1252 J. Gemm., 1986, 20, 3 167

inadvertently picked from my bookshelves another It rests now in France*, where the authorities are Edwin W. Streeter book, 'The Great Diamonds of active in re-assembling their own historic and the World' (London, 1882). Both books have gold notable jewels. leaf edging and somewhat similar sombre binding. I I cannot help hoping that the Sancy has reached opened it out of curiosity, and as I turned the pages its logical resting place, for if it cannot be England it my eye was attracted to 'The Sancy Diamond'. must surely be Paris. Despite Edwin Streeter's Although not a diamond man, still less a diamond description of 'the very Sphinx of diamonds' it grading advocate, I was nevertheless intrigued does, nevertheless, have a truly French connection. because I remembered having personally handled In 1976, during my time as Director of the the Sancy with Alan Jobbins. Readers will remem­ Laboratory, I was invited to participate in the ber Alan Jobbins's article in the Journal of accurate recording of the Sancy diamond. It was a Gemmology, 1977, XV, 5, 240-2, entitled 'A brief great honour, a considerable compliment to our look at the Sancy'. Laboratory, and for me a feeling of excitement to In a report by De Beers dated 1966 the stone is feel that T was there'. stated to be 55ct, white, pear-shaped, named Sancy One of the smallest and least known vicissitudes (Astor), an Indian stone belonging to the Astor suffered by the Sancy in its meandering occurred on family, England. Alan Jobbins's very full report that occasion. For a few seemingly endless moments giving accurate measurements and weight plus in an unfamiliar dark room (cell) about the size of a luminescent characteristics is dated 1976. The telephone kiosk I was preparing to expose the Sancy report which triggered my memory was in Edwin to short-wave ultraviolet exposure to form a contact Streeter's book of 1882. Streeter describes the immersion photograph. I lost the stone in the Sancy as 'the very Sphinx of diamonds'. He says complete darkness and fumbled around with 'the Sancy seems to be wrapped in a dense cloud of adrenalin-charged imagination working overtime mystery, defying the most subtle analysis and trying to locate it. Perhaps my colleagues never impenetrable to the attacks of the keenest processes even noticed the pause which to me seemed endless. of reasoning'. The Sancy was purchased in 1892 by I finished the exposure and added metaphorically William Waldorf Astor, first Viscount Astor. He one more fascinating facet to the Sancy travelogue. gave it as a wedding present to his son, whose wife Nancy, Lady Astor, wore it on state occasions in a [Manuscript received 27 January 1986.] tiara. It passed to her son after her death in 1964. It was on show in Paris in 1962. *The Sancy has been in the Louvre since 1978 - Verlet This brings it almost up to date, or at least to (Pierre), Le 'Sancy' rentre au Louvre, Gazette des Beaux January 1976 when tested by Alan Jobbins at the Arts, November 1978, pp. 165-8. - Ed. Geological Museum laboratory in full view of its then owner, Lord Astor. A good record now exists of its luminescent characteristics, density, weight and a contact immersion photograph showing its light transmission. 168168 J.J. Gemm.,Gemm., 1986,, 20 , 3

A treatmenttreatment procedureprocedure forfor improvingimproving colourcolour andand qualityquality ofof zirconszircons

M.S. Rupasinghe, M.Sc. and Atula Senaratne, M.Sc.M.Sc.

DepartmentDepartment ofof Mineralogy,Mineralogy, UniversityUniversity ofof Mainz, WestWest GermanyGermany

TherTheree areare somesome typestypes ofof gegemm mineralmineralss thathatt appearappear TableTable I.I. TreatmenTreatmentt combinationscombinations iinn thethe jewellerjewelleryy markemarkett onlyonly afteafterr somesome kinkindd ooff treatmentreatmentt whicwhichh makesmakes themthem mormoree attractivattractivee oorr ColourColourss TREATMENTTREATMENTSS 1000°ClOOO°C,, 1515 hrshrs.. saleablesaleable thanthan inin theitheirr naturanaturall state.state. BlueBlue andand colourlesscolourless zirconszircons occuroccur iinn naturenature,, theythey araree nonott foundfound inin sufficientsufficient quantity,quantity, anandd rarelrarelyy iinn TTll T2T2 T T33 T4T4 goodgood enoughenough qualityquality,, foforr commercialcommercial purposespurposes.. ButBut YellowYellow (a)(a) YYTT 1 YYTT 2 YTYT 3 YYT4T 4 witwithh ththee developmendevelopmentt ofof neneww methodsmethods,, gemmolo­gemmolo- GreenGreen (b)(b) GGTT 1 GGTT 2 GTGT 3 GGT4T 4 gistgistss havhavee beebeenn ablablee ttoo converconvertt leslesss attractivattractivee zirconszircons VioleViolett (c)(c) VTVT 1I VTVT 2 VVTT 3 VVT4T 4 intintoo colourlesscolourless andand alsalsoo colouredcoloured stones. DarDarkk GreeGreenn (d(d)) DGDGTT 1 DGDGTT 2 DGDGTT 3 DGDGTT 4 FoForr mormoree thathann ononee hundrehundredd yearyearss workerworkerss havehave suggestesuggestedd ththee possibilitpossibilityy ooff usinusingg zirconzirconss iinn placplacee ooff ...... oxidatiooxidationn --H- reductioreductionn •---> diamondsdiamonds.. TodaTodayy thithiss industrindustryy iiss progressinprogressingg oonn a TTll anandd TT33 - rapirapidd coolincoolingg aatt rooroomm temperaturetemperature ververyy larglargee scale. TT22 anandd TT44 - slosloww coolincoolingg insidinsidee ththee ovenoven

Original T 1 T2 T3 T4 colour Yellow (a)

Green (b)

Violet (c)

Dark Green (d )

o em 1 '---'--J

FigFig.. 11.. ResultResultss ooff ththee treatmentstreatments., (se(seee TablTablee 1)I)..

© CopyrighCopyrightt ththee GemmologicalGemmological AssociationAssociation ISSNISSN:: 0022-12520022-1252 J. Gemm., 1986, 20, 3 169

Table II Concentrations of important elements in zircons from Sri Lanka No. of Si% Fe% Zr% Hf% Th% U% Colour analyses Yellow 36 15.67 0.02 48.25 1.19 0.07 0.14 Green 63 15.87 0.07 47.69 1.44 0.12 0.41 Violet 33 16.02 0.02 48.65 1.01 0.09 0.11

As an accessory mineral in rocks, zircon has been To create an oxidizing environment, the alumina extensively studied by many previous workers crucible, in which the stones were treated, is kept (Vithanage 1957; Vance & Anderson 1972; open. In the case of reducing treatments, stones Sahama 1981). Due to its wide range of occurrences were covered with a thin carbon and a thick alumina in igneous and metamorphic rocks, it has also been layer successively and the crucible kept tightly used as an indicator mineral in petrogenesis. closed. In the present study, authors have experimented on the colour and quality variation in zircons of four Results and Discussion different colours placing them in high temperature, Colour and Chemistry under oxidizing or reducing conditions (Table I). The results obtained were fascinating and the Table II clearly illustrates the compositional findings have proved the success of producing high dépendance of colours in zircons. Green zircons gem-quality stones from less valuable zircons. usually have higher (about 3 times) amounts of iron and uranium, while the other two shows similar chemical properties. The Th content in green Materials and methods stones is relatively higher than that of the other two. Sediment samples from different locations in Green zircons represented nearly 50% of the Ratnapura gemming district of Sri Lanka were sample population subjected to analysis. The collected, washed and the zircon grains carefully majority of them are of metamict type and one can selected using the following techniques in addition expect maximum compositional irregularities, and to visual identification. hence an unusual correlation among elements in geiger - müller counter them. Their high representation in the present density measurements study may have masked the true correlations in refractive index (RI) measurements other coloured stones (Table III) Sommerauer X-ray diffractometer. (1976) reported a possible tolerance of substitution Separated zircon grains were then further of an element with ± 15% ionic size into the zircon divided into four different colours and represen­ lattice (Goldschmidt law). However the relation­ tative specimens were finally analysed chemically ship between green colour and the U content is using an electron-microprobe instrument unmistakable, and therefore the relationships (Cameca; Camebax microbeam). From each grain between colours and Th,Hf, and U content in 3 points have been analysed and also great care has zircons should be thoroughly investigated. been taken to avoid inclusions and tiny holes on surfaces. Three stones from each colour group were then subjected to the following heat treatment procedure.

Table III. Correlation coefficient matrix for the elements studied Si Fe Zr Hf Th Si 1.000 u Fe + 0.287 1.000 Zr - 0.308 0.329 1.000 Hf - 0.128 0.024 - 0.171 1.000 Th - 0.007 0.017 + 0.010 - 0.068 1.000 U - 0.049 -0.041 - 0.166 + 0.455 4- 0.040 1.000 170 J. Gemm., 1986, 20, 3

Quality of treated stones The results of the present study and earlier The combination YT2 (see Table I and Fig. 1) is studies suggest that the phenomenon behind the the most successful result obtained from the colour change is the variation in oxidation state and treatment, in order to produce a colourless and the sites of substitution of impurity ions (e.g. Fe2+, substitute for diamonds. The high reflective nature Fe3+ etc). and the brilliant lustre are the attractive improve­ ments made by this method on zircons. Yellow zircons which have been used for this combination of treatments are very often found in alluvial sediments. The cost of treatment is also very low Acknowledgements and proves its economic feasibility. This work forms part of the doctoral research By the treatment T2 the authors have been able to work of M.S.R. Authors gratefully thanks the Otto produce a reddish-violet stone from a honey-brown Benecke Stiftung (M.S.R.) and Deutscher zircon, which shows an improved lustre. Akademische Austauschdienst (A.S.) for financing Treatment T3 has been able to produce an their doctoral research work at University of Mainz. aquamarine-type light blue and high lustre stone from a green zircon. Further, dark green unattractive metamict zircons can also be changed by T3 into blue, References translucent stones which possibly can be used as 1. Sahama, G.T. 1981. Growth structure in Ceylon Zircon Bull. beads in jewellery. Mineral 104; 89-94. The effects of these treatments on differently 2. Sommeraur, J. 1976. Die Chemisch- Physikalische Stabilität Naturlischer Zirkone und ihr U-(Th)-Pb system. Ph.D Thesis, coloured stones can be seen in Fig. 1 and one can Zürch Tech. University. notice that the other treatment combinations do not 3. Vance, E.R. and Anderson, B.W. 1972. Differences among low improve the quality of stones. However, it is very Ceylon Zircons- Mineralog. Mag. 38, 721-724. interesting to note that all treatment combinations 4. Vitanage, W.P. 1957. Studies of Zircon types in Ceylon Pre- have been able to change the original colour, though cambrian complex -Journ. Geol. 65, 117-128. they do not improve the quality. [Revised manuscript received 10 May 1985.] J.J. Gemm.,Gemm., 1986,20,31986, 20, 3 171171

TheThe brilliantbrilliant cutcut - analysisanalysis ofof weightweight byby calculationcalculation

S.J.A. Currie, F.G.A.F.G.A.

P.O.P.O. BoxBox 566,566, Papakura,Papakura, NewNew ZealandZealand

InIn thethe dailydaily workwork ofof mostmost gemmologists,gemmologists, whowho areare 4.4. Anderson's Equation involvedinvolved inin thethe jewelleryjewellery trade,trade, thethe requirementrequirement ofof WtWt ofof stonestone inin caratscarats = D2D2 x H x 6 havinghaving toto calculatecalculate thethe weightweight ofof a mounted,mounted, roundround (D(D andand H inin cm)cm) brilliant-cutbrilliant-cut diamonddiamond cropscrops upup allall tootoo regularly.regularly. A looklook throughthrough thethe literatureliterature willwill revealreveal a varietyvariety Anderson'sAnderson's equationequation isis thethe samesame asas 3.3. butbut asas thethe ofof equationsequations thatthat havehave beebeenn usedused overover thethe yearsyears andand measurementsmeasurements areare inin cmcm ththee 0.00600.0060 factorfactor becomesbecomes atat firsfirstt glanceglance theythey looklook diversediverse andand confusing.confusing. 6.0.6.0. ItIt waswas thethe veryvery appearanceappearance ofof thesethese equationsequations thatthat 5.5. WtWt ofof stonestone inin caratscarats = DD22 x H x 3.523.52 x 0.0018 first arousedaroused thethe writer'swriter's interestinterest withwith thethe thoughtthought (D(D andand H inin mm)mm) thathatt theythey cannotcannot allall bbee right.right. AfterAfter a veryvery detaileddetailed study,study, inin whichwhich thethe writerwriter InIn thisthis casecase the'S'the 'S' factorfactor isis splitsplit intointo thethe generalgeneral triedtried toto forecastforecast thethe mostmost appropriateappropriate ShapeShape (S)(S) shapeshape factorfactor forfor roundround brilliant-cutbrilliant-cut stonesstones andand FactorFactor forfor a varietyvariety ofof proportions,proportions, a methodmethod multipliedmultiplied byby thethe specificspecific gravitygravity (3.52)(3.52) ofof diamond.diamond. evolvedevolved inin whichwhich thethe accuracyaccuracy ofof thethe calculationcalculation isis TheThe producproductt ofof thesethese twotwo isis 0.006336,0.006336, somesome 5.6%5.6% limitedlimited onlyonly byby thethe abilityability ofof thethe gemmologistgemmologist toto greatergreater thanthan 0.0060.0.0060. measuremeasure thethe parametersparameters ofof thethe stone.stone. 6.6. Leveridge's Equation Nowadays,Nowadays, thethe weightweight ofof a roundround brilliant-cutbrilliant-cut WWtt ooff stonestone iinn caratcaratss = RR22 x H x 0.02450.0245 diamondiamondd iiss usuallusuallyy calculatecalculatedd usinusingg ononee ooff thethe ((RR anandd H iinn mm)mm) followinfollowingg sixsix equationsequations,, wherwheree D iiss ththee diameter,diameter, H isis ththee totatotall heighheightt andand R isis ththee radiuradiuss ofof thethe stone.stone. AlthougAlthoughh Leveridge'Leveridge'ss equatioequationn looklookss quitequite differentdifferent,, ththee ususee ooff ththee 'radius'radius'' insteainsteadd ooff ththee usualusual l.1. GrodzinskïsGrodzinski's Equation 'diameter'diameter'' produceproducess ththee 0.0240.02455 factorfactor,, whicwhichh whenwhen 3 WWtt ooff stonestone iinn caratcaratss = (D/6.42)CD/6.42)3 (CDD measuremeasuredd iinn mm)mm) dividedividedd bbyy '4''4',, equalequalss 0.006150.00615,, makinmakingg ththee answeranswer 2.52.5%% greategreaterr thathann iiff 0.0060.00600 wawass used.used. Grodzinski'Grodzinski'ss equatioeq~ationn representrepresentss a straightstraight propro­­ EssentiallEssentiallyy ththee carat/weighcarat/weightt probleproblemm iiss ononee ooff portioportionn calculatiocalculationn oonn a 1 cctt brilliant-cubrilliant-cutt diamonddiamond elementarelementaryy mathematicmathematicss aass ththee rounroundd brilliant-cutbrilliant-cut anandd iiss quitquitee accurataccuratee oveoverr a considerablconsiderablee rangrangee ooff cancan,, iiff ththee facetfacetss araree disregardeddisregarded,, bbee representerepresentedd bbyy sizessizes,, bubutt iitt taketakess nnoo accounaccountt ooff ththee actuaactuall depthdepth,, ssoo a seriesseries ofof threethree conescones andand a thinthin cylinder,cylinder, asas inin iitt shoulshouldd bbee limitelimitedd ttoo diamonddiamondss ooff ververyy googoodd make.make. FigurFiguree 11.. 22.. WWtt ooff stonstonee iinn caratcaratss = DD33 x 0.50.599 x 0.00600.0060 Where-R = ththee radiuradiuss aatt ththee girdlegirdle.. ((DD iinn mm)mm) RGG = HHp=P = ththee deptdepthh ooff ththee pavilion.pavilion. ThiThiss equatioequationn useusess 0.0060.00600 aass a ShapShapee (S(S)) FactorFactor HHG=G = thicknesthicknesss ooff ththee girdlegirdle.. anandd assumeassumess thathatt ththee deptdepthh iiss 0.50.599 timetimess (59%(59%)) thethe ixRTy —= ththee radiuradiuss ooff ththee tabletable.. girdlgirdlee diameterdiameter,, a faifairr assumptioassumptionn foforr well-cuwell-cutt hhl, = totatotall heighheightt ooff conconee ooff crowncrown.. stonesstones.. hh22 = ththee heighheightt ooff ththee conconee removedremoved,, thethe 2 basbasee ooff whicwhichh iiss ththee tabletable.. 33.. WWtt ooff stonstonee iinn caratcaratss -= DD2 x H x 0.00600.0060 ((DD anandd H iinn mm)mm) thereforthereforee hi~hh 1 - h22 =H= Hec ththee heighheightt ooff ththee crown.crown. BByy calculatincalculatingg ththee volumvolumee ooff eaceachh ooff ththee solidssolids,, ThiThiss iiss a refinementrefinement,, wherwheree HH,, ththee totatotall depthdepth,, iiss i.ei.e.. ththee paviliopavilionn conecone,, ththee girdlgirdlee cylindecylinderr anandd twtwoo includeincludedd aass a measuremenmeasurementt iinn ititss owownn rightright,, crowcrownn conescones,, ththee volumvolumee ooff ththee stonstonee mamayy bbee overcominovercomingg earlieearlierr objections.objections. obtainedobtained.. ThThee volumvolumee ooff ththee crowcrownn iiss ththee volumvolumee ooff ththee wholwholee totopp conconee leslesss thathatt ooff ththee smallesmallerr conecone,, ththee

© CopyrighCopyrightt ththee GemmologicalGemmological AssociationAssociation ISSNISSN:: 0022-12520022-1252 172 J. Gemm., 1986, 20, 3

It should be noted that in both equations, the term HG, the girdle thickness is multiplied by three and shows that the volume, and consequently the weight, is three times as sensitive to changes in girdle thickness as it is to changes in the other heights. The following example will serve to demonstrate the use of these equations. Example: Find the carat weight of a round brilliant-cut diamond of the following dimensions - Diameter, 6.5 mm, Crown angle 34.5°, Table 60%, Pavilion 43.1%, Girdle 2.3%. Substituting in equation A where D=6.5 mm, Hp=0.431, HG=0.023, Â=34.5°, Tb=0.60 then 0.03686 (6.5/2)3 x [(0.431 + (3 x 0.023) 4- 0.5 x tan 34.5°) - (0.63 x 0.5 x tan 34.5°)] = 0.9736 ct. Fig. 1. Diagram illustrating that, if the facets are disregarded, a The total depth can be extracted from this equation round brilliant-cut diamond may be represented as a by the calculation - series of cones and a thin cylinder. (HP + HG + (0.5 x Tan 34.5°)) - (Tb x 0.5 x Tan 34.5°) = 0.591 (expressed as a decimal of the base of which is the table. girdle diameter) Using this method, two equations, A and B, may Replacing the 0.59 in equation 2 with the figure be obtained. One of them (A) uses the crown angle 0.591 and rearranging, the correct'S' factor can be whilst the other (B) makes use of the crown height. calculated -

Equation A - using the crown angle (6.5)3 x 0.591 x

Pav. 39% 41% 43% 45% 47% Ct Wt 0.9208 0.9461 0.9714 0.9966 1.0219 'S' factor 0.00609 0.00604 0.00599 0.00595 0.00592 W -....) C'l :3 :3 " 00 - ::0 w N

J.';-< Gemm., 1986, 20, 3 "0"- ? 173 47 46 4S (c) factor and 44 % the'S' % 43 depth depth between 42 pavilion (b) Pavilion %, 41 relationships the respectively. 40 thickness % ~ girdle illustrating height 39 (a) Graphs crown and 38 2. Fig. -f 1 (b) 0061 factor 0. 0.0058 0.0062 0.0059 0.0060 's' 9 19 8 18 17 7 16 6 15 % % 5 14 ~ height ~ thickness 13 Crown Girdle 12 3 4 11 2 10 9 ----= ~ 8 factor factor 0.0061 0.0062 (a) 0.0058 (c) 0.0059 0.0059 0.0056 0.0058 0.0060 0.0064 0.0063 0.0062 0.0065 0.0061 0.0060 0.0055 's' 's' 174 J. Gemm., 1986, 20, 3

Tables of this type can be produced for the equations on spread cut stones introduces serious variation of the girdle thickness, crown height and errors. crown angle but the results are easier to appreciate if The particular value of the two equations A and B presented in graph form as illustrated. is that any diamond that can be measured as for a The graphs show clearly that the weight and the certificate, with either the crown angle or the crown 'S' factor respond rapidly to changes in girdle depth, can be calculated to quite accurate limits. thickness and crown angle. A small progressive Experience has shown that an error less than 0.5% change occurs in the factor with increasing pavilion can be considered normal for diamonds of good depth, while simple changes to the crown height symmetry. percentage are almost self-neutralizing as far as the As an aid to using the equations, any program­ 'S' factor is concerned. With a reduction in crown mable calculator that can accommodate fifty steps angle both the weight and the factor decrease and five variables, like the Sharp EL-5100, or rapidly. equivalent Casio models, can be used to program- It should be realized that each of the above graphs store and recall the equations at the touch of a features only one variable at a time, i.e. the one button. featuring the pavilion variations from 37% to 47% Equation B for instance can be stored in the relates only to a diamond with crown angle 34.5°, EL-5100 in this form: table 60%, girdle 2.3% but is irrespective of girdle f (ABCDE) = 0.03686x(A-2)Yx3x(B+(3xC) + diameter. x X (D-Kl-E)) (1-EY 3)) The author set out originally to establish a method of weight estimation by adding the separate Where - A = diameter in mm. components of these graphs but although this B = pavilion depth % expressed as a proved to be a mathematical nonsense, the graphs decimal can be used independently. C = girdle thickness % expressed as a The graph of the girdle thickness will probably decimal find the greatest application as it applies to an D= crown height % expressed as a otherwise well cut stone and can be used in decimal conjunction with equation No. 3. E = table % expressed as a decimal The diameter and total depth are inserted in the x equation, and the 'S' factor for the appropriate The term Y 3 appearing twice in the equation is girdle thickness is read off the graph and inserted in che terminology used by this particular machine to the equation instead of 0.0060, thereby making raise a function to the cube power. allowance for the one stone dimension which has Once stored, this equation can be recalled, the the greatest single influence on the 'S' factor and five measurements entered and the answer is consequently the weight. delivered almost instantaneously. The next problem is that of actually making the The graphs also show that 0.0060 is quite measurements. The obvious way would be with a accurate for any diamond within the following Proportionscope, and the 'View-through' type limits: might be suitable provided the culet and the girdle Pavilion between 41% and 44.5%. thickness can be seen and measured. A better Girdle between 2.0% and 2.7%. method would be the use of a microscope with a Table between 55% and 75% provided the Vernier calibrated stage. This would necessitate the angle is 34.5°. taking of measurements and subsequently convert­ The 'S' factor of 0.0060 should not be applied to ing them to decimals of the girdle diameter. any diamond with a crown angle less than 34.5°. The writer's preferred method is to use a zoom There is also a practice in the cutting industry to microscope fitted with a reticle in the eye-piece. thicken the girdle on smaller stones, which has the The most convenient form of reticle is one that is benefit of reducing the fragility of the stone for the divided into one hundred divisions and numbered setter. If diamonds of 3.0 mm, 4.0 mm, 5.0 mm one to ten. The piece of jewellery is clamped on the and 6.0 mm are calculated out, the'S' factor will be stage with the crown of the diamond under seen to start at approximately 0.0063 for 3.0 mm examination facing squarely upwards. The optics and 4.0 mm diamonds, reducing gradually to are then zoomed until the scale length exactly 0.0062 at 5.0 mm and 0.0061 at 6.0 mm. coincides with the girdle diameter. Hence it can be seen that all of the equations Under these conditions the girdle diameter Nos 1 to 6 can produce reasonably accurate results equals 100 divisions and the piece can then be within limited circumstances and provided the moved or rotated so that the table, crown, girdle crown angle is not less than 34.5°. The use of these and pavilion can all be read directly in percentages J. Gemm., 1986, 20, 3 175

of the girdle diameter under the magnification of Details of proof of Equation A (crown angle) (see the microscope. It only remains to take a measure­ Figure 3). ment of the girdle in mm to be able to solve equation Volume = I/aw R H + TT R H + lAn R hi - B. G P G G G 1/377 R^ h2 One final comment about the measuring of the 2 table diameter and the girdle thickness. As the Substituting for RT equals RG x Tb % and factorizing, junction points of the star and girdle facets are 2 Vs RG [(Hp + 3HG + hi) - (Tb x h2) outside the cone of the crown main facets, the table Now in the right angle triangle ABC representing diameter can be taken as the 'point to point' the crown - distance. For the girdle it is necessary to take an average of several measurements at the base of the hi/sin A = RG/sin B main facets. .-. hi = R sin A/sin B Although this technique is not for the smaller G stones, any set diamond of 0.75 ct or more, where the girdle and culet are visible, could warrant the full analysis of proportions. In this case the T gemmologist would have all the information neces­ b sary to make an accurate calculation of carat weight —RT— by this method. , 1

Appendix f, ? The equations A and B are derived as follows: referring to Figure 1 - i y VA HC (a) pavilion volume is VIIT RG HP Rc (b) the girdle volume is IT RG HG 1 ^— —H t The volume of the crown is represented by the whole top cone minus the smaller cone, the base of U D— A which is the table - e.g., Vm RG hi - Vm K\ h2 Although the girdle DIAMETER is the measure­ ment that gemmologists prefer to start with, the As L.A and LB are complementary, mathematics become awkward working with the 2 sin B = sin(90°-A) = cos A term (D/2) , so it is better to stay with R (radius) for and sin A/cos A = tan A the time being. Adding the four terms together and factorizing, Therefore hi = RG tan A and h2 = hx x Tb% = RG x tan A x Tb% Volume = Vvn [RG(HP + 3HG + h{) - (R£ X h2)] ...(X) Substituting for hi and h2, To convert this volume, which is expressed in .*. Volume = cubic mm, to weight in carats, it is necessary to - (a) Divide by 1000 to convert it to cubic cm | RG [(Hp + 3HG + (RG X tan A)) - (b) Multiply by 3.52 (SG of diamond) to convert (Tg x T x R x tan A)] the volume to grams b G and finally At this stage HP and HG are in the form of actual (c) Multiply by 5 to convert grams to carats measurements (mm), so if they are each divided by i.e. 1/1000 x 3.52 x5 = 0.0176 D (girdle diameter) they are in a much more usable form for the gemmologist. Volume = Thus

|RG [(HP x D)/D + (3HG x D)/D + (RG x Ct wt = 0.0176 x f [RG(HP + 3HG + hi) -

(R*xh2)] -.(Y) tan A) D - (Tg x RG x tan A)/D] Unfortunately this equation still includes the Substituting D/2 for RG and extracting D, terms 'hi' and 'h2', neither of which can be measured as they both originate from a point Volume = beyond the top of the stone. y- (D/2)3 [(H + 3H + 0.5 tan A) - Conversion of equation Y into equations A and B p G for use with the crown angle and the crown height (tg x 0.5 tan A)] respectively are shown below. 176176 J.J. Gemm.,Gemm., 1986,20,31986, 20, 3

ConvertingConverting thisthis volumevolume inin cubiccubic mmmm toto caratcarat weigh!weighi ExtractingExtracting thethe D andand substitutingsubstituting (D/2)(D/2) forfor RRGG, , ~1T2TT andand alsoalso takingtaking inin thethe 2;-~- givesgives thethe finalfinal multiply·multiply- VolVol = f- (D/2)3ÇD/2Y [(HI'[(Hp + 3HG3HG + (0((1 - TT b)HcIb)Hc/ inging constantconstant ofof 0.03686.0.03686. (1(1 -~ T~))]Tg))]

3 .... CtCt WtWt = 0.036860.03686 xx (D/2)3(D/2) [(HI'[(HP ++ 3HG3HG ++0. 0.55 tartar ConvertingConverting thisthis volumevolume inin cubiccubic mmmm toto caratcarat weightweight A)A) - (T~(Tg x 0.50.5 tantan A)]A)] ...... (A (A:; and also taking in the 2;277 gives the final multiply­ and also taking in the -=- gives the final multiply­ Details of proof of Equation B (crown height)height) ing constant of 0.03686. UsingUsing thethe samesame diagramdiagram andand introducingintroducing HeHc tt(c in...g Ctconstan Wt t= of0.03686 0.03686 x. (D/2)3 [(HI' + 3HG + replacereplace hIhi -— hzh and an dstarting starting ata tline line No.2No. 2 in in th( th e 3 2 ((1-.-. CtTb)HclO- Wt = 0.0368T&))]6 x (D/2) [(HP + 3H...G (B) + previousprevious proof,proof, ((l-Tb)Hc/(l-Tê))] ...(B) 2 VolumeVolume = 1/31TRbVBTTRG (HI'(HP + 3HG3HG + hIhi - (T~(J h x hz2)»)

AsAs HeHc = hIhi (1(1 -T- Tb%)%),, thenthen hIhi = HcI(1Hc/(1 - TTb%)b%) AcknowledgementsAcknowledgements andand hzh2 = hIhi x Tb%Tb% I shouldshould likelike toto thankthank DrDr G.G. Harrison-JonesHarrison-Jones foforr

SubstitutingSubstituting forfor hIhi andand hz,h2 , criticallycritically readingreading thethe paperpaper andand suggestingsuggesting improve­improve­ ments.ments. VolVol.. = i/snRl/mRbc [HI'[Hp + 3HG3HG + (HclO(Hc/(1 -T- Tb»)) -- ((n((Tg - Hd/OHc)/(1 - TTbb))»]] [Manuscript[Manuscript received 8 August 1985,1985, revisedrevised 1616 JanuaryJanuary 1986.]1986.] Vol.Vol. = VmRbVBHRG [HI'[Hp + 3H3HGG + (H(HclOc/(1 - TTb»Ob))(l -- T~)]Tg)]

NoNoww takingtaking eacheach ofof ththee measurementmeasurementss HI',HP, HGHG anandd HeHG anandd representinrepresentingg themthem asas a decimaldecimal ooff thethe diameterdiameter (Table(Table hashas alreadyalready beenbeen treated),treated),

= 1/31TRbVmRl [(Hp[(Hp x D/DDID)) ++ (3HG(3H Gx x DID)D/D )+ +

Hc x D/D He x DID ((11 _ T3)]T3)] (1(1 "- TTp)p) p J.J. Gemm.,Gemm., 1986,20,31986,20,3 177177

Light,Light, heavyheavy andand rarerare mineralsminerals inin thethe washedwashed gemgem gravelsgravels ofof SriSri LankaLanka

M.S. Rupasinghe, M.Sc.,* AlulaAtula Senaratne, M.Sc.* and C.B. Dissanayake, M.Sc.tM.Sc.†

* DepartmentDepartment ofof Mineralogy,Mineralogy, UniversityUniversity ofof Mainz,Mainz, WestWest GermanyGermany t† DepartmentDepartment ofof Geology,Geology, UniversityUniversity ofof Peradeniya,Peradeniya, Peradeniya,Peradeniya, SriSri LankaLanka

AbstractAbstract andand mostmost ofof themthem havehave beenbeen cultivatedcultivated forfor thethe pastpast Light,Light, heavyheavy andand somesome rarerare mineralsminerals asas foundfound inin twotwo thousandthousand years.years. thethe washedwashed gemgem gravels fromfrom SriSri LankaLanka havehave beenbeen TheThe accidentalaccidental discoverydiscovery ofof gemstonesgemstones inin th'fseth§se studied forfor theirtheir abundance abundance and and chemical chemical compositions. composi­ depositsdeposits attractedattracted peoplepeople intointo gemgem miningmining andand thisthis tions. AmongAmong thethe rarerare mineralsminerals foundfound werewere practicepractice hashas continuedcontinued unbrokenunbroken forfor moremore thanthan a fergusonite,fergusonite, geikielitegeikielite,, niobian-rutileniobian-rutile,, radioactiveradioactive thousanthousandd yearsyears.. rutile,rutile, allanitallanitee anandd thorite/thorianite.thorite/thorianite. AnalysesAnalyses forfor ThereThere areare twtwoo mainmain gemmingemmingg areaareass iinn SriSri Lanka,Lanka, rare-earthrare-earth elementselements andand 2255 otheotherr elementelementss werewere namelnamelyy RatnapuraRatnapura anandd ElaheraElahera,, andand alsalsoo a fewfew mademade,, anandd amonamongg ththee noteworthynoteworthy featurefeaturess areare thethe scatteredscattered locationslocations;; Rakwana,Rakwana, Tissamaharama,Tissamaharama, abundances of of Th Th and and U Uin zirconin zircon and and monazite. monazite. OkkampitiyOkkampitiyaa andand others.others. A noteworthnoteworthyy featurefeature iiss thatthat allall thesethese regionregionss areare locatelocatedd inin ththee HighlandHighland IntroductionIntroduction andand South-westSouth-west GroupGroup meta-sedimentarmeta-sedimentaryy for­for­ SriSri LankaLanka (Ceylon)(Ceylon) isis aann islandisland witwithh anan areareaa ooff mationsmations.. 6945069450 sq.kmsq.km andand isis essentiallessentiallyy a parpartt ooff ththee shieldshield TheThe aiaimm ofof thithiss studystudy isis toto identifyidentify allall typetypess ooff areareaa ooff peninsulapeninsularr India.India. GeologicallGeologicallyy andand physicallyphysically gemstonesgemstones andand otherother heavyheavy mineralmineralss iinn thethe gem­gem- SriSri LankaLanka iiss ththee southernsouthern continuatiocontinuationn ooff thethe bearinbearingg gravelgravelss frofromm thesthesee areas,areas, anandd alsalsoo toto IndianIndian sub-continent.sub-continent. ItIt iiss believedbelieved toto havhavee sepa­sepa­ identifidentifyy thethe majormajor differencesdifferences amonamongg thesthesee deposits.deposits. rateratedd inin recentrecent geologicalgeological timetimess duedue ttoo shallowshallow tectonitectonicc movements.movements. ThThee greategreaterr parpartt ooff ththee islanislandd (90%(90%)) iiss madmadee uupp ooff PrecambriaPrecambriann metamorphimetamorphicc rocksrocks,, whicwhichh cacann bbee GeologGeologyy ooff ththee areareaa studiedstudied divided.intdivided .intoo foufourr majomajorr divisionsdivisions,, vizviz.. HighlandHighland FigFig.. 1 illustratesillustrates thethe majormajor gemminggemming areasareas ofof SriSri GroupGroup,, South-wesSouth-westt GroupGroup,, EasterEasternn anandd WesternWestern LankaLanka,, anandd FigFig.. 2 illustrateillustratess ththee geologgeologyy ooff thethe VVijayani jay an ComplexesComplexes c"Munasinghe(Munasinghe andand Dissanayke,Dissanayke, RatnapurRatnapuraa anandd RakwanRakwanaa gegemm fields. ScatteredScattered 1982)1982).. AparApartt frofromm ththee twtwoo smalsmalll JurassiJurassicc sedimen­sedimen­ alluviualluviumm iiss founfoundd lyinlyingg oonn charnockite-meta­charnockite-meta- tartaryy basinbasinss (Fig(Fig.. 11)) (togethe(togetherr 8-18-100 sq.kmsq.km)) ththee restrest sedimentarsedimentaryy rocksrocks;; namelnamelyy charnockitescharnockites,, garnet­garnet- ooff ththee islanislandd (10%(10%)) iiss coverecoveredd bbyy TertiarTertiaryy (Miocene(Miocene sillimanitsillimanitee granulitesgranulites,, amphibolitesamphibolites,, anandd perthiteperthite­- limestone)limestone),, QuaternarQuaternaryy (re(redd bedsbeds,, clasticlasticc sediments)sediments) bearinbearingg garnet-biotite-granulitigarnet-biotite-granuliticc gneissesgneisses.. HereHere anandd RecenRecentt (alluvial(alluvial)) sediments.sediments. charnockitcharnockitee anandd pelitipeliticc garnet-sillimanitgarnet -sillimanitee granulitesgranulites ThThee HighlanHighlandd GrouGroupp occupieoccupiess ththee entirentiree hilhilll araree ththee prédominenpredominentt rocrockk typestypes.. FurtheFurtherr thethe countrcountryy ooff ththee islanislandd anandd iiss comprisecomprisedd ooff granulitegranulite occurrencoccurrencee ooff zircozirconn granitesgranites,, vein-quartvein-quartzz anandd facièfaciess metasedimentsmetasediments,, whilwhilee ththee VVijayani jay an complexescomplexes pegmatitepegmatitess iiss a notablnotablee featurfeaturee ooff ththee regionregion.. araree comrjTrisecomprisedd ooff granitoidsgranitoids,, migmatitemigmatitess anandd migmatitimigmatiticc gneissesgneisses.. ThThee South-wesSouth-westt GrouGroupp iiss alsalsoo madmadee uupp ooff granulitgranulitee facièfaciess metasedimentmetasedimentss anandd aass indicateindicatedd bbyy ththee presencpresencee ooff cordieritcordieritee (Kat(Katzz 19721972)) FigFig.. 3 illustrateillustratess ththee geologgeologyy ooff ththee ElaherElaheraa gegemm representrepresentss differen differentt pressure/temperaturpressure/temperaturee concon­­ field, situatesituatedd iinn ththee north-easnorth-eastt foofoott slopeslopess ooff ththee ditionsditions.. CentraCentrall HighlandsHighlands,, wherwheree a ridgridgee anandd vallevalleyy ThThee highighh ratratee ooff weatherin weatheringg iinn thithiss tropicatropicall islanislandd topographtopographyy iiss prédominentpredominent.. QuartziteQuartzite,, marblemarble,, hahass denudatedenudatedd ththee lanlandd foforr ththee paspastt fefeww milliomillionn garnet-sillimanite-biotitgarnet-sillimanite-biotitee gneissesgneisses,, witwithh tourmalinetourmaline yearyearss anandd givegivenn risrisee ttoo thicthickk anandd extensivextensivee pilepiless ooff (Rupasingh(Rupasinghee et al.,aZ., 19841984)) anandd charnockitcharnockitee araree ththee sedimentsedimentss iinn floodflood plainplainss ooff alalll majomajorr riversrivers.. OnOnee majomajorr rocrockk typetypess lyinlyingg iinn thithiss regionregion.. cacann alsalsoo seseee burieburiedd streamsstreams,, riverriverss anandd sedimentsediment­- filledfilled lakes.lakes. TheseThese vastvast alluvialalluvial plainsplains areare veryvery fertilefertile

© CopyrighCopyrightt ththee GemmologicaGemmologicall AssociatioAssociationn ISSNISSN:: 0022-1250022-12522 171788 JJ.. Gemm. Gemm., , 19861986,20, 20, ,3 3

WVC - Western VIJayan Complex E V[ - Eastern VIJayan Complex HG -Highland Group SWG - Southwest Group

~ main gemming areas

N t

8"00

~ E lahe ra ~ ~

Kandy

Nawalopltlya fZ..

Scale .1.500.000 o 10 20 30 Mis • i 'i " ', ' 10 30 50KTS

Fig.Fig . I.1 . GeneralizedGeneralized geologicalgeologica l mapmap ofof SriSr i LankaLanka withwith majormajor gemminggemming areas.areas . ":""' C).., 80"30" 8~40' 80· W , 3 13

:c00 .0' N ;=> ""

.... <, <, -,

, , " <, <, <, <, ;:/ <, , • ./ <,

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t>,.i;; ~[ <, [ZJ. . ! - U 'l ~RAIII <,

6·30

S" PIC tOCALIll 1ll1.'CE i ;: 'S I

Sf:I~!" S:.wPtE. j( .l.lIT, I I PO.c

8a? l ' 179

Fig, 2. Generalized geological map of the Ratnapura and Rakwana areas. 180 J. Gemm., 1986,20,3

7°45'

x

a :::> a z .....o. X x

7°40' I t I . '/1 -, "Y i , . I. I ''1' l;=;1 ",'d; v -~,. I A • k:J

I:'. :;': ':1 QUARTZITE E2J CHARNOCKITE IT2:IJ GARNET GNEISS ~ MARBLE L+: .::'+.::I GRANITE

~ STREAM

7°36" b" , I L '"'' I' ( ( fFFI~ ¢ -/{M f; ):; X Xi· :: j:·1 80°47 '

Fig. 3 Generalized geological map of the Elahera area. J. Gemm., 1986, 20, 3 181

Materials and methods Heavy and light mineral contents of the gem Sampling methods sediments Samples were collected from locations shown in The heavy mineral content of the Rakwana Figs 2 and 3. All samples were taken from existing sediments is higher than that in Elahera. However a gem pits. The pay gravel layers, locally termed marked similarity exists between sediments from 'illam', are usually composed of rounded or Rakwana and Ratnapura the heavy mineral subangular pebbles or boulders of quartz, heavy content of the Rakwana sediments being approxi­ minerals and also gemstones. mately twice as high as that in Elahera (see Fig. 4). 15-25 buckets of clayey gravel (illam)* were The greater abundance of pegmatites in the SW taken from each pit and washed until clay was region could well be a cause for the presence of high removed. The remaining portion, locally termed amounts of heavy minerals in that area. Minerals, 'nambuwa', was collected in polythene bags. The very often found in pegmatites and in rocks weight of an average sample varied in the range of associated with cordierite gneisses (Katz, 1972; 10-15 kg. However, during the process of washing Wadia and Fernando, 1944; Coomaraswamy, 1906), light gem minerals such as beryl (SG 2.7), and are found in greater amounts in sediments from the amethyst (SG 2.65) are often washed away with Rakwana and Ratnapura regions. other light minerals. In the Elahera area, pegmatites are more felsic and the heavy mineral content is very low. Analyses Further, the area is flat and covered by thick A quarter of a sample was taken for heavy/light alluvial sediments and the accumulation of heavy mineral separation (Fig. 4) and the percentages of minerals is comparatively less. In the hilly south­ heavy and light fractions measured. Here the west region, the high rate of errosion and trans­ minerals having higher densities than tetrabro- portation washes away the light minerals resulting methane (SG 2.96) were considered as heavy in high concentrations of heavy minerals in the minerals while the others were treated as light sediments. minerals. Other liquids of varying densities are also used in Radioactive minerals determining densities of minerals. The remaining The following minerals found in this study, were material of each sample was used in the following categorized as radioactive minerals: monazite; series (Fig. 5) of investigations (physical and zircon; thorianite; thorite; allanite. chemical), for identification and also in the under­ Among these, zircons are widely used in jewellery. standing of the processes involved in their formation. It is of interest to note that radioactive zircons have also been found in jewellery. Jobbins et al. (1977) have reported a monazite crystal with high radio­ activity found in a piece of Sri Lankan jewellery. 100 H-Heavy The radioactivity of gem-quality zircons varies L-Light according to their thorium and uranium contents.

76 75 Table 1. Th and U concentration of differently o/o 62 56 coloured zircons from Sri Lanka

50 44 Colour Th% U% 38 Green 0.11176 0.4095 24 Violet 0.0840 0.1131 L L L Yellow 0.0740 0.1360 V/ Rose 0.0600 0.1190 AA VA/. /// (Rupasinghe, 1984) Rakwana Ratnapura Elahera

Fig. 4 Percentage of heavy and light minerals in the sediments Table 1 shows the Th and U contents of some from the three major gem fields. zircons from Sri Lanka. It is apparent that the green *Local miners use a cane basket shaped like a gold prospector's zircons contain greater amounts of Th and U. steel pan, which is easily rotated in water even when it is full of An average monazite contains about 8% Th and 'illam'. 0.4% U. 181822 JJ.. Gemm.Gemm.,, 19861986,20,3, 20, 3

Native Light Minerals Heavy Minerals Metals

Gemstones

RA

Graphite Gold

Nb-Rutile* Rutile Quartz Monazite* Zircon* Ilmenite* Pyrolusite Orthoclase Zircon Tourmaline* Pyrite* Goethite Beryl Thorianite Corundum Apatite Fergusonite Moonstone Thorite Sillimanite Epidote Geikielite Calcite Allanite Kornerupine Titanite Sinhalite Topaz *-Analysed for Rare Earth Elements Spinel by Neutron Activation Technique Hessonite Chrysoberyl RA=radioactive minerals Pyropel Almandine/S pessartine

FigFig.. 55.. A generagenerall classificatioclassificationn ooff mineralmineralss foundfound inin washedwashed gemgem sedimentssediments ('nambuwa').('nambuwa').

Rare mineralsminerals Allanite 3+ 2+ TheThe followinfollowingg mineralsminerals founfoundd inin thethe gegemm gravelsgravels (Ca, Ce)zCe)2 (Fe3+,(Fe , FeFi+)) AI2Al[010HlSi02[OIOHISi04ISi4ISiz207107] ooff SriSri LankaLanka cancan bbee groupegroupedd aass rarerare mineralsminerals onon thethe ThisThis mineraminerall iiss founfoundd iinn ththee ElaheraElahera,, RatnapuraRatnapura basibasiss ofof theitheirr abundance:abundance: fergusonite;fergusonite; geikielite;geikielite; anandd RakwanaRakwana gegemm sediments,sediments, bubutt iinn smallsmall amounts.amounts. niobianniobian rutilerutile;; anandd alsoalso radioactiveradioactive rutile;rutile; allanite;allanite; TheyThey araree generallygenerally rounderoundedd inin shapeshape anandd areare thoritethoritelthorianite./ thorianite. consideredconsidered toto bbee derivedderived frofromm pegmatitespegmatites.. ItIt isis worthworthyy ofof notnotee thatthat allaniteallanitess founfoundd inin South-westSouth-west Fergusonite (Yt(Nb,(Yt(Nb, Ta)04)Ta)04 ) GrouGroupp sedimentssediments araree lessless radioactiveradioactive thathann thosethose ThisThis mineralmineral locallylocally termetermedd 'Gurupachcha'.'Gurupachcha'. foundfound inin thethe HighlandHighland GroupGroup sediments.sediments. ThisThis isis founfoundd onlyonly iinn ththee south-westsouth-west region.region. CoomaraswamCoomaraswamyy (1906(1906)) founfoundd somesome fergusonitefergusonite ThoritelthorianiteThorite I thorianite (ThSiOATh, (ThSi04l(Th, U)Oz)U)02 ) containingcontaining abouaboutt 22%% thorithoriaa anandd overover 4%4% ofof U3O8U 30 g, ThesThesee mineralmineralss areare foundfound onlyonly inin ththee South-westSouth-west andand believedbelieved toto bebe derivedderived fromfrom granitesgranites andand GroupGroup sedimentssediments andand dodo notnot generallygenerally traveltravel farfar pegmatites.pegmatites. GenerallyGenerally fergusonitefergusonite isis foundfound asas awayaway fromfrom source.source. OccurrencesOccurrences ofof richrich sourcessources ofof roundedrounded grains,grains, blackblack toto brownbrown inin colour,colour, andand veryvery thesethese mineralsminerals werewere foundfound byby previousprevious workersworkers richrich inin elementselements suchsuch asas Nb,Nb, TaTa andand BeBe (Rosier,(Rosier, (Coormaraswamy,(Coormaraswamy, 1906),1906), inin thethe BambarabotuwaBambarabotuwa 1980).1980). area.area. SearleSearle (1962)(1962) reportedreported thorianitethorianite withwith aboutabout 7l.45%71.45% ofof ThOThO andand 22.5%22.5% U33008g.• Geikielite (Mg Ti 0033) ThisThis mineralmineral isis onlyonly foundfound inin thethe RatnapuraRatnapura gemgem Niobian rutilerutile sediments.sediments. ItIt isis blackblack inin colour,colour, andand hashas a fleshy-redfleshy-red NiobianNiobian rutilerutile inin sedimentssediments waswas reportedreported forfor streak.streak. ThisThis maymay havehave beenbeen derivedderived fromfrom thethe South­South­ thethe fi.rstfirst timetime inin SriSri LankaLanka andand isis foundfound onlyonly inin thethe westwest GroupGroup calc-silicates.calc-silicates. TheThe X-rayX-ray diffractometerdiffractometer RakwanaRakwana sediments.sediments. ItIt isis veryvery richrich inin Nb,Nb, andand Ta,Ta, patternpattern isis veryvery similarsimilar toto thatthat ofof ilmeniteilmenite andand onlyonly andand alsoalso containscontains largelarge amountsamounts ofof CeCe andand LaLa chemicalchemical analysis oror specificspecific gravitygravity teststests enableenable oneone (270(270 ppm,ppm, 9191 ppmppm respectively).respectively). TheThe chemicalchemical toto distinguishdistinguish thisthis mineralmineral fromfrom ilmenite.ilmenite. compositioncomposition ofof thisthis mineralmineral isis shownshown inin TableTable 2.2. JJ.. Gemm.,Gemm., 1986,20,31986, 20, 3 183183

TableTable 2.2. MicroprobeMicroprobe analysisanalysis ofof sixsix differentdifferent andand 158158 ppmppm respectively).respectively). pointspoints inin a 'Niobian'Niobian rutile'rutile' 4 thethe accumulationaccumulation factorfactor (Table(Table 3)3) indicatesindicates thatthat NNbb mineralsminerals accumulataccumulatee iinn thethe RatnapuraRatnapura % ii iii iv v vi sedimentssediments moremore thanthan inin ElaheraElahera sediments.sediments. TheThe differencesdifferences inin physical,physical, mineralogicalmineralogical andand Ti022 58.1958.19 50.2750.27 49.6649.66 48.5748.57 58.4458.44 49.3649.36 FeOFeO 8.088.08 10.5310.53 10.0510.05 10.4410.44 8.438.43 10.6810.68 geochemicalgeochemical propertiesproperties ofof sedimentssediments maymay bebe duedue toto theirtheir geological,geological, geomorphologicalgeomorphological andand hydrologicalhydrological Nb2 05s 24.2324.23 29.6729.67 30.6330.63 31.031.044 23.2323.23 30.0030.00 Ta20sTa 0 9.509.50 9.549.54 9.599.59 9.959.95 9.909.90 9.969.96 historics.histories. 2 5 TheThe NNbb contentscontents inin thethe sizesize fractionfraction <0.63^o<0.63Mmn ofof TableTable 2 illustratesillustrates thethe compositionacompositionall inhomo­inhomo- gemgem sedimentssediments fromfrom Ratnapura,Ratnapura, RakwanaRakwana (SW(SW geneitygeneity inin a single graingrain ofof niobianniobian rutile.rutile. TheThe Group)Group) andand ElaheraElahera areare aboutabout thethe same.same. ButBut NbNb inin specificspecific gravitygravity ofof thisthis mineralmineral variesvaries accordingaccording toto 'nambuwa''nambuwa' fromfrom SWSW regionregion isis higherhigher thanthan IIIin thethe chemicalchemical composition,composition, inin thethe rangerange ofof 4.2-5.6.4.2-5.6. 'nambuwa''nambuwa' fromfrom ElaheraElahera byby a factorfactor ofof two.two. TheThe NNbb contentcontent inin thisthis mineralmineral isis approximatelyapproximately threethree timestimes higherhigher thanthan thatthat ofof lunarlunar NNbb rutilerutile Cuprite (CuD)(CuO) (Hlava(Hlava et al.,al, 1972)1972).. ThisThis mineralmineral hashas alsoalso beebeenn foundfound forfor thethe firstfirst timetime inin SriSri Lanka,Lanka, inin thethe RakwanaRakwana sediments.sediments. ThisThis TableTable 3.3. NbNb concentrationsconcentrations (ppm)(ppm) inin rocksrocks andand porouporouss andand earthy-greyearthy-grey mineralmineral hashas beebeenn testedtested byby washedwashed sedimentssediments ('nambuwa')('nambuwa') fromfrom RatnapuraRatnapura X-rayX-ray diffractometrydiffractometry andand itsits identificationidentification con­con­ andand ElaheraElahera firmed. CoomaraswamyCoomaraswamy (1906)(1906) hashas reportedreported a fewfew RocksRocks NNambuw ambuwaa occurrencesoccurrences ofof nativenative coppercopper inin thethe PelmadullaPelmadulla averageaverage averageaverage AccumulationAccumulation area.area. TheseThese werewere foundfound inin lateriteslatentes withwith ferruginousferruginous NbNb NNbb FactorFactor concretions.concretions. TheThe presencpresencee ofof cupritecuprite inin thisthis areaarea isis a clearclear indicationindication ofof a possiblpossiblee occurrenceoccurrence ofof nativenative RatnapuraRatnapura 1212 166166 1414 copper.copper. ElaherElaheraa 1010 88 9 Gold TheThe 'Mahawangsaya''Mahawangsaya' (the(the writtenwritten historyhistory ofof SriSri TableTable 4.4. NNbb concentrationsconcentrations inin differentdifferent rockrock LankaLanka - whichwhich runsruns backback somesome 26002600 years)years) statesstates typestypes fromfrom RatnapuraRatnapura andand ElaheraElahera thatthat SriSri LankansLankans havehave usedused goldgold iinn theirtheir jewellery,jewellery, religiousreligious monumentsmonuments andand thrones,thrones, forfor thousandsthousands ofof No.No. ofof AverageAverage NbNb years.years. RockRock samplesample samplessamples contentcontent DissanayakeDissanayake andand KarunaratneKarunaratne (1984)(1984) inin theirtheir Ratnapura geo-archaeologicalgeo-archaeological studystudy statestate thatthat thethe ancientancient AcidAcid charnockitecharnockite 7 1717 ppmppm SinhaleseSinhalese obtainedobtained nativenative goldgold fromfrom manymany differentdifferent BasicBasic charnockitecharnockite 6 1010 ppmppm locationslocations throughoutthroughout thethe island.island. DurinDuringg thethe coursecourse IntermediateIntermediate charnockitecharnockite 2 1212 ppmppm ofof thisthis study,study, threethree nativenative goldgold nuggetsnuggets ofof aboutabout BiotiteBiotite gneissesgneisses 3 1717 ppmppm 0.60.6 g werewere foundfound inin 'nambuwa''nambuwa' fromfrom thethe SWSW regionregion QtzQtz Felds.Felds. Gneisses 2 4 ppmppm andand thethe peoplepeople inin certaincertain villagesvillages (e.g.(e.g. Omatta)Omatta) hadhad SedimentsSediments 3030 2222 ppmppm mademade jewellerjewelleryy frofromm thisthis locallylocally foundfound gold.gold. InIn thethe seventeenthseventeenth century,century, planterplanterss iinn thesethese areasareas foundfound Elahera goldgold inin somesome alluvialalluvial sediments,sediments, butbut duedue toto tech­tech­ CharnockiteCharnockite 4 8 ppmppm nologicanologicall constraintsconstraints thisthis industryindustry hahass beenbeen GneissesGneisses 1111 1212 ppmppm abandoned.abandoned. InIn ordeorderr toto evaluateevaluate thethe economiceconomic MarbleMarble 4 1 ppmppm feasibilityfeasibility ofof thesthesee gold-bearinggold-bearing sediments,sediments, a SedimentsSediments 6 2424 ppmppm detaileddetailed studystudy isis essential.essential.

TablesTables 3 andand 4 showshow thethe NbNb contentscontents ooff Rare-earth element distribution in mineralsminerals 'nambuwa''nambuwa' andand variousvarious rocksrocks respectively.respectively. ItIt cancan bebe Nb-rutileNb-rutile,, monazite,monazite, zircon,zircon, tourmalinetourmaline andand pyritepyrite seenseen frofromm thesethese tablestables that:-that:- havehave beenbeen analysedanalysed bbyy neutronneutron activationactivation analysisanalysis 1 acidacid charnockitescharnockites containcontain nearlynearly twicetwice asas muchmuch forfor REEREE andand 2525 otherother elementselements (see(see TableTable 5)5).. NbNb asas basibasicc charnockitescharnockites (1(177 ppppmm andand 1010 ppmppm ZirconZircon anandd monazitemonazite araree ricrichh iinn thethe REEREE aass wellwell aass respectively) . ThThandU and U.. 2 biotitebiotite gneissesgneisses containcontain NbNb amountsamounts similarsimilar toto AcknowledgementsAcknowledgements acidacid charnockitescharnockites (17(17 ppm).ppm). Grateful thanksthanks areare duedue toto MessrsMessrs S.M.B.S.M.B. 3 NbNb contentcontent inin ElaheraElahera nambuwanambuwa isis lessless thanthan thatthat Amunugama,Amunugama, K.K. DunuhappawaDunuhappawa andand MrsMrs J.J. inin RatnapuraRatnapura andand RakwanaRakwana (88(88 ppm,ppm, 113113 ppmppm WijesekeraWijesekera forfor theirtheir assistance.assistance. 184184 J.J. Gemm.,Gemm., 1986,20,31986, 20, 3

TableTable 5.5. NeutronNeutron ActivationActivation AnalyticalAnalytical datadata ofof somesome importantimportant mineralsminerals foundfound inin SriSri LankanLankan gemgem sedimentssediments

ZirconZircon IlmeniteIlmenite Nb-rutileNb-rutile PyritePyrite TourmalineTourmaline MonaziteMonazite

Nb22005S _ - 24.23%24.23% - - - TiTi _ ' 32.6%32.6% 30.00%30.00% - - - FeFe 0.1%0.1% 36.1%36.1% 8.25%8.25% 47.58%47.58% 11.65%11.65% - NaNa 6 18.418.4 370370 2929 1.86%1.86% 538538 K 1515 1818 120120 2525 150150 1.01%1.01% ScSc 11.611.6 5353 130130 2525 162162 2 CrCr _ 350350 - 91309130 4444 2020 MnMn 4 23002300 154154 4 42154215 8585 CoCo 3 5555 - 158158 - 100100 ZnZn _ 470470 - - 360360 - GaGa _ 4 3333 - 383383 - AsAs _ 1 - 1313 3 - SeSe _ _ - 1212 - - BrBr _ — 4444 5 3 - SrSr _ _ 4400 - - - ZrZr 4747%% - - - - 1.35%1.35% MMoo - 1515 - - - - IInn _ — 2 - - - SbSb _ 1 - 1 1 2255 BBaa _ - 222200 - - 50005000 LaLa 0.40.4 1111 9911 1 2 1212 CCee _ 2626 272700 - 2 2626%% SmSm _ 1 - 0.040.04 436436 1%1% EuEu 0.0.55 0.10.1 0.50.5 0.10.144 - 104104 TTbb 2.2.22 - - - - 437437 DDyy 1919 0.50.5 - - - 10321032 HoHo 8 - - - - - YYbb 7744 0.0.33 - - - 123123 LLuu 1616 0.0.99 - - - 3355 HHff 22%% 4.4.55 444477 - - - TTaa 1 7788 77%% - 1.41.400 - W — 2222 28428444 - - - AAuu _ — - 0.00.033 - - TThh 424255 4 2255 - - 8.348.34%% U 24124100 - 252544 0.10.177 - 36436400 NoteNote:: AlAlll values iinn ppppmm excepexceptt thosthosee indicateindicatedd aass %.%.

ReferenceReferencess 1.I. Coomaraswamy,Coomaraswamy, A.K. A.K. 1906. 1906. Administration Administration Report, Report, Mineralogical Minera­ 88.. RupasingheRupasinghe,, M.A.M.A.,, BanerjeeBanerjee,, A.A.,, PensePense,, JJ.. anandd DissanayakeDissanayake,, Survey,logical Ceylon Survey, (Sri Ceylon Lanka), (Sri 1-13. Lanka), 1-13. C.BC.B.. 19841984.. ThThee GeochemistrGeochemistryy ooff BerylliuBerylliumm anandd FluorinFluorinee iinn 22.. CoorayCooray,, P.G.P.G.,, 19571957.. The Geology ofof Ceylon.Ceylon. p.p. 323,323, NationalNational ththee GeGemm FieldFieldss ooff SrSrii LankaLanka,, Mineralium Deposita, 1919,, 86-9386--93.. MuseumMuseumss ooff CeyloCeylonn (Sr(Srii LankaLanka)) PublicationPublication.. 99.. RupasingheRupasinghe,, M.SM.S.. 19841984.. Ph.D. Thesis, (i(inn preparation)preparation) 33.. DissanayakeDissanayake,, C.BC.B.. anandd KarunaratneKarunaratne,, W.M.AW.M.A.. 19841984.. A UniversitUniversityy ooff MainzMainz,, WesWestt Germany.Germany. GeoarchaeologicaGeoarchaeologicall StudStudyy ooff AncienAncientt GolGoldd DepositDepositss iinn SrSrii 1010.. SearleSearle,, D.LD.L.. 19641964.. The Metamorphic History of Ceylon and thethe LankLankaa (i(inn preparation)preparation).. Origin of thethe Charnockite series. IntInt.. GeolGeol.. CongressCongress,, 22n22ndd 44.. JobbinsJobbins,, E.A.E.A.,, TreshamTresham,, A.EA.E.. anandd YoungYoung,, B.RB.R.. 19771977.. GeGemm SessionSession,, NeNeww DelhiDelhi.. 1313,, 45-584S-S8.. MonazitMonazitee frofromm SrSrii LankaLanka,, J. Gemm. XVXV,, 295-929S-9.. 1111.. WadiaWadia,, D.ND.N.. anandd FernandoFernando,, L.J.DL.J.D.. 19441944.. RecordRecordss ooff ththee 5S.. KatzKatz,, M.BM.B.. 19721972.. OOnn ththee OrigiOriginn ooff RatnapurRatnapuraa typtypee GeGemm DepartmenDepartmentt ooff MineralogMineralogyy CeyloCeylonn (Sr(Srii Lanka)Lanka),, ProfessionalProfessional DepositDepositss ooff SrSrii LankaLanka.. Econ. Geol. 6767,, 13-1513-IS.. PaperPaper.. 1-44.1-44. 66.. MunasingheMunasinghe,, TT.. anandd DissanayakeDissanayake,, C.BC.B.. 19821982.. A PlatePlate­- 1212.. HlavaHlava,, P.F.P.F.,, PrinzPrinz,, MM.. anandd KeilKeil,, KK.. 19721972.. NiobiaNiobiann RutilRutilee iinn tectonitectonicc ModeModell foforr ththee GeologiGeologicc EvolutioEvolutionn ooff SrSrii LankaLanka.Jour.. Jour. aann Apoll-1Apoll-144 KreeKreepp FragmentFragment,, Meteoritics, 77,, 44,, 479-85479-8S.. Geol. Soc. India,India, 2323,, 369-80369-80.. 77.. RösterRoster,, H.JH.J.. 19801980.. LehrbuchLehrbuch Der Mineralogie, VEBVEB DeutscherDeutscher VerlaVerlagg füfiirr GrundstoffindustrieGrundstoffindustrie,, LeipzigLeipzig.. 833833.. [[ManuscriptManuscript received 4 April 1985.J1985.] J. Gemm., 1986, 20, 3 185

Gemmological Abstracts

ALIPRANDI, R. 1984. Qualche osservazione sulla BORELLI, A. 1984. Metodo rapido per la distinzione presenza di inclusioni in rubini sintetici da dell'ambra dai suoi sostituti naturali o artificiali. fondente di récente produzione. (Observations (A quick method of distinguishing amber from on the presence of inclusions in synthetic ruby its natural and artificial substitutes.) La Gem­ from the beginning to the latest productions.) La mologia, 10, 3/4, 10-14. Gemmologia, 10, 3/4, 15-19, 5 figs in colour. Simple tests are outlined. M.O'D. Characteristic inclusions in different types of synthetic ruby are described and illustrated. M.O'D. BORELLI, A., SBRANA, G. 1981. Uso della spettro- grafia I.R. per distinguere la turchese naturale da quella sintetica e dagli altri sostituti e per ALIPRANDI, R., GUIDI, G. 1985. Berillo bicolore rilevarne eventuali sofisticazioni. (Use of infra­ deH'Orissa (India). (Bi-colour beryl from Orissa, red spectrography to distinguish between natural India.) La Gemmologia, 10, (sole issue of 1985), turquoise and synthetic material and various 27-31, 8 figs (3 in colour). substitutes with means of increasing sophisti­ A cut stone from Orissa, India, had colourless cation.) La Gemmologia, 7, 3/4, 9-13, 2 figs. and golden yellow sections. RI of the two sections Infrared spectroscopy can help to distinguish were 1.570, 1.575 and 1.574, 1.580, respectively. between natural and synthetic turquoise and some SG was 2.73-2.74. A much higher Fe3+ content was of its imitations. IR spectra are illustrated. M.O'D. found in the golden sections (0.67% compared with 0.13%). M.O'D. BORELLI, A., TROSTI FERRONI, R. 1981. Metoclo BENAVIDES,M.E. 1985. Gemologfa. (Gemmology.) non distruttivo per la determinazione al dif- Gaceta Mineralôgica, Sociedad Mexicana de fratometro a R.X. di gemme policristalline tipo Mineralogia, 1, 3, 12-14, 1 fig. giada e tipo turchesse, delle loro imitazioni A short account of what constitutes a gemstone. naturali e di certi sostituti artificiali. (A non­ M.O'D. destructive method for the X-ray diffraction study of jade- or turquoise-like poly crystalline BORELLI, A. 1981. La 'turquerenite' o 'turchese gems, their natural imitations and some artificial afgana' (magnesite colorata artificialmente) un substitutes.) La Gemmologia, 7, 1/2, 5-10, 4 figs sostituto minore délia turchese. ('Turquerenite' (1 in colour). or 'Afghan turquoise' (artificially coloured X-ray diffraction has been used to identify magnesite) a minor turquoise substitute.) La natural, natural imitations and man-made imitations Gemmologia, 7, 3/4, 14-17, 3 figs (2 in colour). of jade- and turquoise-like poly crystalline minerals. Dyed magnesite with an SG of 2.69-2.77 and a Diffraction patterns are given. M.O'D. hardness of between 4 and 5 has been used as a turquoise imitation. A strong absorption band at about 590nm is illustrated and there is also BORELLI, A., TROSTI FERRONI, R. 1981. Un absorption in the violet with fainter bands in the inconsueto materiale tipo giada. (An unusual blue. M.O'D. jade-like material.) La Gemmologia, 7, 1/2, 11-12, 3 figs (1 in colour). BORELLI, A. 1983. Turchese: porposta di classi- A green material resembling jade was found to be ficazione e nomenclature gemmologico-mer- an amphibole of the glaucophane type. X-ray ceologica. (Turquoise: proposals for a classifica­ diffraction was used and the spectra obtained are tion and nomenclature for gemmology and given. M.O'D. commerce.) La Gemmologia, 9, 1/2, 22-8. A system of classification and nomenclature for turquoise is outlined which includes treated and BOSCARDIN, M., COLMELET, G., VIOLATI imitation material as well as synthetic stones. TESCARI, Q. 1982. Xonotlite: un nuovo minérale M.O'D. italiano di interesse gemmologico. (Xonotlite, a 186 J. Gemm., 1986, 20, 3

new Italian mineral of gemmological interest.) La BROWN, G., SNOW, J. 1985. The Relite refracto­ Gemmologia, 8, 3/4, 12-16. meter light source. Australian Gemmologist, 15, Xonotlite, a calcium silicate with the composition 12, 458-9, 1 fig. Ca3Si308(OH)2 and a member of the monoclinic An evaluation of an extra-bright LED source for crystal system, has been found in an area of contact use with batteries or 9V DC mains converter. between monzonitic rocks and Triassic dolomites at Height of LED is adjustable. R.K.M. Contrada, Molini di Laghi, Vicenza, Italy. The hardness is 6 and the colour pink and white veining. BURLS, J. 1985. Diamonds from the Emerald Isle. Rlisa = ß = 1.583,7 = 1-593. M.O'D. Optima, 33, 169-79, 5 figs. Historical survey of the development of the De Beers Shannon plant synthesizing diamond grit, BOSCH-FIGUEROA, J.M. 1985. Caracteristicas producing syndite and syndie (for wire drawing) morfologicas de los diamantes. (Morphological occasioned by its Silver Jubilee. E. S. characteristics of diamonds.) Gemologia, 23, 67/68, 14-22, 2 figs. Characteristics of diamond crystals from a number of South African mines are given. M.O'D. BUTINI, E., ALIPRANDI, R. 1981. Corallo: imitaz- ioni e trattamenti. (Coral: imitation and treat­ BOSCH-FIGUEROA, J.M. 1985. Tratamientos ment.) La Gemmologia, 7, 111, 13-17. empleados para modificar el color del topacio. Descriptions and a table of coral and its (Treatment used to modify the colour of topaz.) imitations, including treated material, are given. Gemologia, 23, 67/68, 23-8, 4 figs. Among the natural simulants palygorskite is sug­ The treatment of topaz by a variety of methods gested as a possibility. M.O'D. resulting in alteration of colour is described. M.O'D. CAUCIA, F., SACCHETTI, A., SETTI, M., VENIALE, F. 1984. Studio di opali naturali e sintetici. (A BREITER, K., PASAVA, J. 1986. Bohemian quartz. study of natural and synthetic opal.) La Gem­ Lapidary Journal, 39, 11, 54-5, 4 figs. mologia, 10, 1/2, 16-21, 2 figs. Ferruginous quartz is found in some Ordovician Natural and synthetic opals were, examined by volcano-sedimentary iron ore deposits south-west X-ray diffraction, thermal analysis, IR spectrometry, of Prague, Czechoslovakia. A star-like red and electron microscopy and the electron microprobe. yellow quartz can be found on dumps near the Different types of structure are identified. M.O'D. mines at Zajecov and Svata Dobrotiva. M.O'D. COLLINS, A.T., 1983. Centri di colore nei diamanti. (Colour centres in diamond.) La Gemmologia, 9, BROWN, G. 1985. Conversion kits for built-in LED 3/4, 20-46, 19 figs. refractometer light sources. Australian Gem- A detailed review of the role played by colour mologist, 15, 12, 456-8, 3 figs. centres in the coloration of diamond with re­ An evaluation of Snow kits supplied for use with production of absorption spectra. M.O'D. different makes of refractometer. Fitting in some instances requires disassembly of the instrument COUTY, R., VELDE, B. 1986. Pressure-induced which might invalidate a guarantee. R. K. M. band splitting in infrared spectra of sanidine and albite. American Mineralogist, 71, 99-104, BROWN, G., HAMID, D., KELLY, S.M.B. 1985. 6 figs. Some information on the Kashmir sapphires. In the infrared spectra of sanidine and albite Australian Gemmologist, 15, 12, 448-9, 2 figs in under pressures of up to 40 kbar convergence was colour. noted. New bands were seen in the sanidine spectra Features extracts from diary of Melbourne and these are attributed to changes in the position of dealer, George Hamid, who visited the area in 1982 the alkali ion in the structure as it influences the but found no Kashmir sapphires. Suggests that the oxy gent s of the te trahedr al network. M.O'D. day of the Kashmir sapphire is over. R. K. M. COZAR, J.S. 1981. Alejandrita sintetica. (Syn­ BROWN, G., SNOW, J. 1985. Green dyed 'crackled thetic alexandrite.) Boletin del Instituto Gemologico beryl'. Australian Gemmologist, 15, 12, 454-5, Espanol, 21, 31-5, 8 figs in colour. 6 figs. Cut specimens of synthetic alexandrite grown by An 8.1 ct leek-green beryl which owed its colour Creative Crystals Inc. of Concord, California, were to heating and quenching in green dye. R. K. M. examined. RI was 1.740-1.749 and SG 3.70. A J. Gemm., 1986, 20, 3 187

normal absorption spectrum for alexandrite was FLAMINI, A., GASTALDI, L., GRUBESSI, O., observed. Flux inclusions indicated the origin. VITICOLI, S. 1983. Contributo della spettroscopia M.O'D. ottica ed EPR alia distinzione tra smeraldi naturali e sintetici. (The contribution of optical COZAR, J.S. 1984. Enstitita 'Ojo de Gato' en el spectroscopy and EPR to the distinction between olivino de la isla de Lanzarote. (Cat's-eye natural and synthetic emerald.) La Gemmologia, enstatite in the olivine of the island of Lanzarote.) 9, 1/2, 6-11, 3 figs. Boletin del Instituto Gemolögico Espanol, 25, Studies using optical absorption spectroscopy 30-50, 26 figs in colour. and EPR on natural and synthetic emerald are Cat's-eye green enstatite is found at Lanzarote in discussed. Work was carried out in a wide tem­ the Canary Islands where olivine of gem quality perature range. Spectra are reproduced and dis­ occurs. The enstatite is found as macroscopic tinction said to be nearly conclusive. M.O'D. inclusions in the olivine. M.O'D. FLAMINI, A., GASTALDI, L., GRUBESSI, O., COZAR, J.S., RIVAS, P., FERNADEZ, M. 1985. VITICOLI, S. 1983. Sulle caratteristiche^ parti- Alteraciones hidrotermales caracteristicas de la colari del berillo rosso dell'Utah. (Particular kimberlita de la chimenea Dutoitspan. (Character­ characteristics of red beryl from Utah.) La istic hydrothermal alterations of the Dutoitspan Gemmologia, 9,1/2,12-20, 20 figs (12 in colour). kimberlite pipe). Boletin del Instituto Gemolögico Cut stones and crystals of red beryl from Espanol, 26, 5-24, 12 figs (11 in colour). Wildhorse Spring and Wah Wah, Utah, USA, were A kimberlite sample from the Dutoitspan studied with a variety of methods. Colour is related diamond mine and its composition assessed; pecto- principally to divalent manganese and shows in cut lite is among the minerals identified. M.O'D. stones in a variety of characteristic patterns. Concentric pyramidal zoning of colour is noted in DE MICHÈLE, V. 1981. Materiali gemmiferi many cut stones; the pyramids have orange cores italiani. (Italian gem materials.) La Gemmologia, with purple and light pink showing as the edges are 7, 3/4, 17-25. reached. M.O'D. A list with brief descriptions of Italian gem and ornamental materials is given. Among them are FLAMINI, A., GASTALDI, L., GRUBESSI, O., adularia, albite, amber, andalusite, anglesite, apatite, VITICOLI, S. 1983. Risultati preliminari di sintesi axinite, beryl, varieties of quartz, chrysoberyl, di smeraldi. (Preliminary results on the synthesis datolite, diopside, epidote, euclase, garnets, leucite, of emeralds.) La Gemmologia, 9,3/4,6-9,6 figs (4 olivine, opal varieties, prehnite, serpentine, tour­ in colour). maline , vesuvianite and zircon. M.O'D. Single crystals of emerald were grown from a Li2Mo207 flux. Transition metal ions were used as DONTEN VILLE, S., CALAS, G., CERVELLE, dopants. Cell dimensions are reported and optical B. 1986. Etude spectroscopique des turquoises absorption spectra given. A strong band was seen at naturelles et traités. (Spectroscopic study of 825nm and ascribed to iron. M.O'D. natural and treated turquoise.) Revue de Gem- mologie, 86, 3-4, 3 figs. FLAMINI, A., GRUBESSI, O., MOTTANA, A. 1984. II Second part* of a paper covering the spectra of sistema chimico del berillo e le sue conseguenze Gilson turquoise and plastic-impregnated turquoise. sulle propriété fisiche. (The chemical system M.O'D. of beryl and its significance for its physical properties.)La Gemmologia, 10,1/2,6-15,6 figs. DRAGSTED, O. 1985. Nummite. Australian Gem- Synthetic emeralds have smaller unit cell para­ mologist, 15, 12, 461, 2 figs in colour. meters than natural ones and in this paper the A new ornamental variety of gedrite found at presence of water molecules is suggested as one of Godthab Fjord, Greenland, is brown with golden the causes of this. M.O'D. inclusions. R.K.M. FRANCIS, P. 1986. Indian antiquity. Lapidary FJORDGREN, O. 1986. Infrared detective. Lapidary Journal, 39, 12, 45-55, 3 figs. Journal, 39, 12, 39-41, 1 fig. An account of the mining in India of amethyst Infrared photography can be used to detect heat and citrine and their shipment to the West as far treatment of geuda corundum. M.O'D back as the first century AD. M.O'D.

FUENTES, J.C., ROSELLO, E.A. 1986. Topacios en * The first part was abstracted in J.Gemm., 1986, 20, 2, 125-6. la provinçia de Catamarca, Argentina. (Topaz 188 J. Gemm., 1986, 20, 3

from the province of Catamarca, Argentina.) GARZON JIMENEZ, J. 1983. El color de las gemas. Boletin del Instituto Gemolôgico Espanola, 27, (The colour of gems.) Boletin del Instituto 25-8, 5 figs (4 in colour). Gemolôgico Espanol, 24, 21-47, 22 figs in colour. Topaz is found at the contact between a A comprehensive review of the various causes of metamorphic rock and the host rock of the granitic colour in gemstones with diagrams of the processes Papachacra formation in the Belén Dept of involved. M.O'D. Argentina. The mineral is formed hydro thermally; some crystals are up to 50mm in length, euhedral to GAUTHIER, J.-P. 1986. L'opale noble au micro­ subhedral and light greenish-yellow. M. O ' D. scope électronique. (Precious opal under the electron microscope.) Revue de Gemmologie, 86, FUMEY, P. 1986. L'opale précieuse en territoire du 21-6, 20 figs. Sud-Australien: Coober Pedy. (Precious opal A study of the structure of precious opal as seen from South Australia: Coober Pedy.) Revue de with the electron microscope. High quality illustra­ Gemmologie, 86, 17-20, 4 figs (2 in colour). tions are provided. M.O'D. An account of the history and geology of the Coober Pedy opal deposit with a diagram of the formations in which it is found. M. O ' D. GRAETSCH, H., FLÖRKE, O.W., MIEHE, G. 1985. The nature of water in chalcedony and opal-C from Brazilian agate géodes. Physics and Chemistry GARCIA GIMENEZ, R., LEGUEY JIMENEZ, S. 1981. of Minerals, 12, 300-6, 10 figs. Influencia de elementos cromoforos en elbaitas Water species H20 (SiOH) and H20(moi) in zonadas. (Influence of chromophores in zoned chalcedony and opal-C (a type of opal occurring elbaites.) Boletin del Instituto Gemolôgico Espanol, with chalcedony in Brazilian agates) were studied 21, 21-8, 4 figs (2 in colour). by a variety of techniques. Both chalcedony and Iron and manganese are shown by spectroscopy opal-C have fully hydrated surfaces at the open to be responsible for the different colours of elbaite porosity and contain additional water at inner tourmaline. Electron microscopy was used to surfaces which are closed micropores in the case of examine the crystals. M. O ' D. opal-C and regions of accumulated defects in chalcedony. Tests indicated that chalcedony is formed at low temperatures. M.O'D. GARCIA GUINEA, J. 1983. Materiales gemolögicos espanoles, minerals, perspectivas générales. (Spanish gemmological materials, minerals, general overview.) Boletin del Instituto Gemolôgico GRECO, S. 1982. Notizie sull'ambra di Santo Espanol, 24, 9-18, 7 figs (6 in colour). Domingo. (Note on amber from Santo Domingo.) Spanish gemmological minerals include beryl, La Gemmologia, 8, 1/2, 25-34, 8 figs in colour. topaz, olivine, rose quartz, citrine and variscite. Characteristics of amber from Santo Domingo M.O'D. (Dominican Republic) are described and illustrated. M.O'D.

GARCIA GUINEA, J. 1986. Materiales gemolögicos espanoles: los zafiros de Goyân (Pontevedra). GUBELIN, E. 1985. II riconoscimento dei nuovo (Spanish gemmological materials: sapphires rubini sintetici. (The recognition of the new from Goyân (Pontevedra).) Boletin del Instituto synthetic rubies.) La Gemmologia, 10, (sole issue Gemolôgica Espanol, 27, 16-24, 14 figs (9 in of 1985), 6-18, 42 figs (41 in colour). colour). Translation into Italian of a paper first published Blue sapphires are found in andalusite masses in in J.Gemm., 1983, XVIII, 6,477-99. M.O'D. mica schist segregation veins at Goyân, Pontevedra, Spain. M.O'D. GÜBELIN, E. 1986. Deux nouveaux produits artificiels sur le marché des pierres précieuses: le GARCIA GUINEA, J., GALÀN HUERTOS, E. 1985. rubis synthétique 'Ramaura' et le gallo-aluminate Materiales gemolögicos espanoles: yacimientos d'yttrium. (Two new artificial products on the de cuarzo. (Spanish gemmological materials: gem market: Ramaura synthetic ruby and yttrium quartz deposits.) Boletin del Instituto Gemolôgico gallium aluminate.) Revue de Gemmologie, 86,15, Espanol, 26, 27-40, 18 figs (12 in colour). 8 figs in colour. The main Spanish quartz deposits of gem­ Second part of a paper translated from the mological importance are listed and described. German and covering characteristic inclusions in Some examples are analysed. M.O'D. the materials concerned, which are illustrated. M.O'D. J. Gemm., 1986, 20, 3 189

GUILLEN, P. 1986. El coral. (Coral.) Boletin del LANDAIS, E. 1981. Assorbimento del berillo nell- Instituto Gemolôgico Espanol, 27, 6-15, 14 figs in infrarosso: suo contributo alia distinzione fra colour. smeraldi naturali e sintetici. (Absorption of beryl An attractively illustrated account of the use of in the infrared: its role in distinguishing between coral as an ornamental material. M.O'D. natural and synthetic emerald.) La Gemmologia, 7, 3/4, 5-14, 6 figs. HOFMEISTER, A.M., ROSSMAN, G.R. 1985. A model Details of the IR absorption spectra for a number for the irradiative coloration of smoky feldspar of natural and synthetic emeralds are given. It is and the inhibiting influence of water. Physics and possible to distinguish the natural and hydro- Chemistry of Minerals, 12, 324-32, 6 figs. thermal product from that grown by the flux-melt Radiation induced smoky colour and associated method, since the latter shows no water IR EPR signals were found to develop in potassium spectrum, whereas the other two show the charac­ feldspar when free from structurally bound water. teristic bands. M.O'D. Fluid inclusion water does not affect coloration. M.O'D. LEGUEY, S., MORANTE, M., MEDINA, J.A. 1982. HOFMEISTER, A.M., ROSSMAN, G.R. 1986. A Inclusiones piramidales en berilos relacionades spectroscopic study of blue radiation coloring in con fenomenos de corrosion. (Pyramidal in­ plagioclase. American Mineralogist, 71, 95-8, clusions in beryl related to corrosion phenomena.) 4 figs. Boletin del Instituto Gemolôgico Espanol, 23, Blue in sodic plagioclase arises from electronic 17-27, 14 figs (6 in colour). transitions of Pb: a similar transition gives the Inclusions in a beryl crystal from Minas Gérais, colour in amazonite. Both types of feldspar have Brazil, show pseudo-pyramidal form. Some also elevated Pb concentrations, structurally in­ display zoning and others a differing coloration and corporated hydrogen, similar response of the colour degree of transparency. The differences observed to heating and irradiation and similar features in the are related to the degree of corrosion encountered absorption spectrum, including band shape, position during formation. M.O'D. and polarization. M.O'D. LIND, T., SCHMETZER, K., BANK, H. 1985. HUANG, Z.H., GANDAIS, M. 1985. Some physical Methods for the distinction of natural and properties of a labradorite single crystal from synthetic amethyst. Australian Gemmologist, 15, Mexico. Bulletin de Mineralogie, 108, 829-33, 12, 463-70, 7 figs in colour. 3 figs. Several methods are discussed: conoscopic ex- A gem-quality labradorite crystal was shown to imination for complete uniaxial centre cross; have a plagioclase structure and refractive indices of angular colour zones; poly synthetic twinning; 7 1.5689, ß 1.563 and a 1.5598. These values fluid, two-phase and ripple-fracture inclusions; correspond to a composition of An62 which was sharp lamellar and angular colour zoning; finger­ confirmed by the electron microprobe. Some albite print pattern on lightly polished surfaces - all twin lamellae were seen but otherwise the crystal denote natural amethyst. Synthetics are untwinned was transparent with no compositional zoning or and show none of these features. Infrared spectro­ inclusions. The size was 2x2x1 cm. M.O'D. scopy shows that absorption line in region of 3500cm_1 occurs only in the synthetic amethyst. Further methods of discrimination are being KANKA, A. 1986. Achate von Waldhambach. sought. R.K.M. (Agate from Waldhambach.) Lapis, 11, 4, 25-7, 7 figs (6 in colour). Fine agate, with some amethyst, is found at MANGIAGALLI, G., ROSEO, 1.1985. Una rodingite a Waldhambach, north-west of Karlsruhe, West vesuviana della Valtournenche (Aosta) come Germany. M.O'D. materiale di interesse gemmologico. (A vesuvianite rodingite from Valtournenche (Aosta) as a KOURIMSKY, J. 1980. Piètre preziose della Ceco- material of gemmological interest.) La Gem­ slovacchia. (Precious stones of Czechoslovakia.) mologia, 10 (sole issue of 1985, 19-23, 8 figs in La Gemmologia, 6, 3/4, 5-13, 11 figs. colour. The different geological areas of Czechoslovakia A vesuvianite rodingite resembling jade is re­ are reviewed: amethyst, rose quartz and agate, ported from Valtournenche (Aosta). RI is about aquamarine and golden beryl, are found as well as 1.700; SG ranges from 3.07 to 3.32 and there is an moldavite which is probably the best-known absorption line near 460nm. The colour is light to ornamental material. M.O'D. dark green. M.O'D. 190 J. Gemm., 1986, 20, 3

MARENSI DE MOURA, O.J., GARCIA GUINEA J. 1984 which included heating in various fluids. At 100°C, Pegmatitas espanolas con berilo y otras similares held for four hours, no cracking occurred. At 200°C de Minas Gerais (Brasil). (Beryl-bearing Spanish cracking occurred quickly in all specimens, the pegmatites and other similarities with Minas more so in that from the Coober Pedy Eleven Mile Gerais, Brazil.) Boletin del Instituto Gemolôgico mine. Unresolved anomalies were found and the Espanol, 25, 9-28, 6 figs. experiments do not appear to have contributed Spanish beryl-bearing pegmatites are related to answers as to why some opals crack at ambient the Centro Iberica and Ossa-Morena structural temperatures. R.K.M. units. Beryl occurs in the intermediate zones associated with microcline-perthite, quartz and POIROT, J.-P. 1986. Pierres précieuses. (Precious muscovite, or in metasomatic phases. Similarities stones.) Monde et Minéraux, 71, 28^1, 12 figs in with beryl-bearing pegmatites in Minas Gérais, colour. Brazil, are recorded. M.O'D. First part of a very general though beautifully- illustrated guide to the gem varieties of minerals. MOLINE SALA, A. 1985. Aparato para la observation M.O'D. de fluorescencias en materiales gemolögicos. (Apparatus for the observation of fluorescence in POUGH, F.H, 1986. Ammolite: grandmother of gem materials.) Gemologia, 23, 67/68, 5-13, pearl. Lapidary Journal, 39, 10, 35-41, 9 figs in 7 figs. colour. A device operating with intermittent production Fossilized ammonite shell from a location near of long-wave and short-wave ultraviolet light and of Lethbridge, Alberta, Canada, shows an attractive white light is used for gem testing. Construction play of colour and has been used ornamentally. The and results are described. M.O'D. play of colour is more directional than that shown by opal and the spectral succession is less pro­ NASSAU, K. 1982. Quarzo ametista-citrino naturale, nounced. Stones have been capped with synthetic trattato e sintetico. (Natural amethyst-citrine spinel. M.O'D. quartz, treated and synthetic.) La Gemmologia, 8, 3/4, 17-28, 9 figs (7 in colour). A translation into Italian and adaptation of PRING, A., DIN, V.K., JEFFERSON, D. A., THOMAS, papers by the author in Lapidary Journal, 1981, 35, J.M. 1986. The crystal chemistry of rhodizite: a 1,52-60*. M.O'D. re-examination. Mineralogical Magazine, 50, 355, 163-72, 6 figs. O'DONOGHUE, M. 1986. Gems and gemmology. An analysis of rhodizite using high-resolution Watchmaker, Jeweller and Silversmith, March electron microscopy, magic angle spinning nuclear 1986, pp. 54-7, 3 figs in colour. magnetic resonance, single crystal X-ray structure The first of a new series, this column includes refinement and fresh chemical investigation has notes on jade and its simulants, the gem minerals of given the formula (Ko.40Cso.36Rbo.06Nao.02) 2 0.90 Pakistan, impregnated opal and some new synthetic Al3.99Be4(B11.35Beo.55Lio.o2)028- M.O'D. materials. (Author's abstract.) M.O'D. PROUT, B.A.W. 1986. Jet. WahroongaiNews, 20,1, O'DONOGHUE, M. 1986. Gems and gemmology. 6-7. Watchmaker, Jeweller and Silversmith, April A brief account of the history and rise and fall in 1986, pp. 46-8. fashion of this rather gloomy mourning gem. The The gemstones of Pakistan, methods of gems tone introduction of the cheaper black glass, vulcanite weighing, notes on new synthetic materials and on and ebonite contributed to its decline as much as freshwater pearls from China, are included in this did changes in fashion. R.K.M. month's column. (Author's abstract. ) M. O' D. SAMUELS, S.K. 1986. Burma's jade. Lapidary PEARSON, G. 1985. The role of water in cracking of Journal, 39, 12, 20-5, 1 fig. opal. Australian Gemmologist, 15, 12, 435-45, Short account of Burmese history as it affects jade 3 figs. recovery and use. M.O'D. In an attempt to assess cracking potential in Australian opal the author used samples from SARMIENTO CARPINTERO, L. 1985. La importancia Coober Pedy (3 areas), Mintabie, Lightning Ridge dç las inclusiones en la gemologia. (The importance and White Cliffs (2 areas) in a series of experiments of inclusions in gemmology.) Boletin del instituto Gemolôgico Espanol, 26, 41-9, 11 figs in colour. A well-illustrated survey of the more important * Abstracted inJ.Gemm., 1981, XVII, 8, 638. inclusions in gemstones. M.O'D. J.J. Gemm.,Gemm., 1986,20,31986, 20, 3 191191

SAVASCIN,SAVASCIN, Y.Y. 1986.1986. AnatoliaAnatolia.. LapidaryLapidaryJournal, Journal, 3939,, TALAVERATALAVERA ESCUDERO,ESCUDERO, AA.. 1981.1981. PerlaPerlass cultivadascultivadas dede 12,12, 42-4,42-4, 5 figs inin colour.colour. aguaagua dulce.dulce. (Freshwater(Freshwater culturedcultured pearls.)pearls.) Boletin GemGem materialsmaterials foundfound inin AnatoliaAnatolia (Turkey)(Turkey) del Instituto GemologicoGemolôgico EspartOl, Espanol, 21,21 ,9-10, 9-10 , 44 figs figs includeinclude firefire opalopal fromfrom SimawSimaw andand chalcedonychalcedony fromfrom inin colour.colour. Eskisehir-Saricakaya.Eskisehir-Saricakaya. ObsidianObsidian isis alsoalso found.found. A briebrieff descriptiondescription ofof freshwaterfreshwater culturedcultured pearlspearls M.O'D.M.O'D. withwith a notenote onon SpanishSpanish occurrences.occurrences. M.O'D.M.O'D.

SCHMETZER,SCHMETZER, K. ,, BANK,BANK, H.H. 1984.1984. CrystalCrystal chemistrychemistry THEMELISTHEMELIS T.T. 1986.1986. OvenOven freshfresh sapphires.sapphires. Lapidary ofof tsilaisitetsilaisite (manganese(manganese tourmaline)tourmaline) fromfrom Zambia.Zambia. Journal, 39,39, 11,49-53,11, 49-53, 3 figs inin colour.colour. N.N.Jb. Jb. Miner. Mh., 2,2,61-9 61-9.. TheThe authorauthor describesdescribes thethe heatingheating ofof colourlesscolourless Chemical,Chemical, opticaloptical andand X-rayX-ray datadata ofof manganese­manganese- corundumcorundum toto produceproduce blubluee sapphiresapphire inin SriSri Lanka.Lanka. bearinbearingg tourmalinetourmaline fromfrom ZambiaZambia areare given.given. ThThee M.O'D.M.O'D. tourmalinetourmaliness havehave manganesemanganese contentscontents ooff approxi­approxi­ matelymately 6-7%6-7% MnOMnO andand ironiron contentscontents 0.1%0.1% FeO,FeO , TOMBS,TOMBS, G.G. 1985.1985 . Jade:Jade: thethe gemstonegemstone materialmaterial andand theythey representrepresent intermediateintermediate membersmembers {)fof a solidsolid enigma.enigma. Australian Gemmologist, 15,15, 12,445-7.12, 445-7. solutionsolution seriesseries betweebetweenn thethe idealizedidealized endend membersmembers TheThe authorauthor describesdescribes thisthis aass anan appreciationappreciation elbaite,elbaite, NNaa (Li1.5AI1.5)AI6-(B03)3Si6018(OH,F)4,(Ulm5All.5)Al6-(fi03)3S\6Ols(PH9F)49 exercise.exercise. ItIt isis littlelittle more.more. R.K.M.R.K.M. andand tsilaisite,tsilaisite, Na(Mn1.5AI1.5)AI6(B03)3Si601801.5Na(Mni.5Ali.5)Al6(B03)3Si6Oi8Oi.5 + (OH,F)z.s.(OH,F)2.5. AnAn isomorphicisomorphic replacementreplacement ofof Li+Li + TURREL,TURREL, M.M. 1986.1986 . DecouverteDécouverte dede l'Autriche.l'Autriche. (OH)-(OH)~ —--->» Mnz+Mn2+ + Oz-02~ isis foundfound toto bbee dominantdominant inin (Discovered(Discovered inin Austria.)Austria.) Revue de Gemmologie, naturalnatural manganesemanganese tourmalinestourmalines overover a secondsecond typetype 86,86, 16,16, 1 fig. inin colour.colour. ofof coupledcoupled substitutionsubstitution A1Al33+ + Oz-02~ --->—> Mnz+Mn2+ + A shortshort revierevieww ofof AustrianAustrian mineralsminerals whichwhich (OH)-,(OH)~, whichwhich isis presentpresent onlyonly inin a minorminor amount.amount. includeinclude emeraldemerald fromfrom thethe Habachtal.Habachtal. M.O'D.M.O'D. TourmalineTourmaline fromfrom ZambiaZambia hashas a compositioncomposition ooff aboutabout 70%70% ooff ththee tsilaisittsilaisitee endend member,member, andand ththee physicalphysical propertiesproperties ofof thisthis intermediateintermediate tourmalinetourmaline (ao0 15.915,15.915, Coc0 7.1237.123 A;Â; nene l.623,1.623, non0 l.647;1.647; D VINK,VINK, B.W.B.W. 1986.1986. StabilityStability relationsrelations ofof malachitemalachite 3.133.13 g/g/cmcm3)3) areare closeclose toto thethe datadata publishedpublished foforr andand azurite.azurite. Mineralogical Magazine, 50,50, 355355,, membersmembers ofof thethe elbaite-schorlelbaite-schorl solidsolid solutionsolution series.series. 41-7,41-7, 4 figs. Author'sAuthor's abstract.abstract. K.S.K.S. AzuriteAzurite isis formedformed onlyonly underunder relativelyrelatively acidacid conditionsconditions aatt fairlyfairly highhigh carbonatecarbonate activities,activities, thesethese STELLER,STELLER, E.T.E.T. 1985.1985 . Angles.Angles. Australian Gem­ takingtaking placplacee underunder basibasicc conditions.'conditions.*Malachit Malachitee iiss mologist, 15,15, 12,12, 450-3,450-3, 1 fig.fig. thusthus thethe commonercommoner formform ofof coppercopper carbonate.carbonate. CriticismCriticism ofof thethe AustralianAustralian IdealIdeal DesignDesign foforr SmallSmall changeschanges inin carbonate/bicarbonatecarbonate/bicarbonate activitiesactivities roundround BrilliantBrilliant forfor diamonddiamond (Australian Gemmologist, Gemmologist, explainexplain thethe commoncommon alterationalteration ofof azuritazuritee ttoo 1984,1984, 15,15, 7,7, 219-26,219-26, 243-6*)243-6*) whichwhich presentepresentedd ththee malachite.malachite. Eh-pEh-pHH diagramsdiagrams showshow stabilitystability relationsrelations peculiapeculiarr ideideaa ofof sixteesixteenn paviliopavilionn facets.facets. DrDr Steller,Steller, a ofthetwominerals.of the two minerals. M.O'D.M.O'D. retiredretired UniversityUniversity mathematician,mathematician, alsoalso criticisescriticises a paperpaper byby DrDr SuzukiSuzuki (Australian Gemmologist, 1970).1970). tf R.K.M.R.K.M. WALTERS,WALTERS, J.J. 1986.1986. Agate,Agate, factfact andand fantasy.fantasy. Lapidary Journal, 39,39, 11,11, 38-9.38-9 . SUNAGAWA,SUNAGAWA, I.I. 1983.1983. Diamanti,Diamanti, naturalinaturali e sintetici.sintetici. A briefbrief introductionintroduction toto agateagate lore.lore. M.M.O'D O'D.. (Natural(Natural andand syntheticsynthetic diamond.)diamond.) La Gem-Gem­ mologia, 9,9, 3/4,3/4, 10-19,10-19, 3 figs. A generalgeneral revierevieww ofof naturalnatural andand syntheticsynthetic WOODRUFF,R.E.WOODRUFF, R.E. 1986.1986. Larimar.Larimar. LapidaryJournal,Lapidary Journal, diamondsdiamonds withwith discussiondiscussion ofof theirtheir formation.formation. 39,39, 10,10, 26-32,26-32, 8 figs (4(4 inin colour).colour). M.O'D.M.O'D. TheThe namename isis givengiven toto a blubluee mineralmineral ofof volcanicvolcanic originorigin tentativelytentatively identifiedidentified asas a varietyvariety ofof pectolite.pectolite. SWOBODA,SWOBODA, E.R.E.R. 1986.1986. GreeGreenn phantoms.phantoms. Lapidary ItIt iiss founfoundd inin ththee DominicanDominican RepublicRepublic aboutabout 10km10km Journal, 39,39, 11,11 , 19-24,419-24, 4 figs (1(1 inin colour).colour). northnorth ofof thethe roadroad fromfrom BarahonaBarahona toto Bahoruco.Bahoruco. PhantomPhantom inclusionsinclusions inin variousvarious typestypes ofof quartzquartz areare M.O'D.M.O'D. describeddescribed withwith anecdotesanecdotes ofof thethe author'sauthor's field tripstrips inin Brazil.Brazil. M.O'D.M.O'D. YAMAMOTO,YAMAMOTO, T.T. 1982.1982 . OstrasOstras perliferasperliferas Akoya.Akoya. (Akoya(Akoya pearlpearl oysters.)oysters.) Boletin del Instituto Gemo16gicoGemolôgico Espanol, Espanol, 23,23 ,8-16 8-16 6 6 figs figs in in colour. colour . * AbstractedAbstracted inJ.Gemm.,in J.Gemm., 1985,1985, XIX,S,XIX, 5, 438.438 . A usefuluseful reviewreview ofof thethe variousvarious activitiesactivities ooff tf AbstractedAbstracted inJ.Gemm.,in J.Gemm., 1971,1971, XII,S,XII, 5, 180-1.180-1. JapaneseJapanese culturedcultured pearpearll manufacturers.manufacturers. M.M.O'D O'D.. 192 J. Gemm., 1986, 20, 3

ZANCANELLA, R. 1981. Nuovi metodi di analisi ZEITNER, J.C. 1986. Quartz, the lapidary favorite. degli elementi qualitativi del diamante. (New Lapidary Journal, 39, 11, 26-32, 5 figs in colour. methods of analysis of qualitative elements in A brief introduction to the quartz minerals with diamond.) La Gemmologia, 7, 3/4, 18-24, 1 fig. special reference to their ornamental usage. M.O'D. A method of plotting and assessing the role of inclusions in the clarity of diamond is suggested. ZEITNER, J.C. 1986. Rare among rare. Lapidary Micron-sized inclusions are noted using appropriate Journal, 39, 12, 26-34, 4 figs in colour. microscopic techniques and are placed in arbitrary A short illustrated survey of some of the less shapes (circle, rectangle, square, rhombus) to form common gemstones to be found in Asia. Stones a basis for clarity assessment. M.O'D. discussed include painite, manganotantalite, kornerupine, sinhalite, cymophane, zircon, jadeite, ZAPATERO RAMOS, L. 1981. Diapositivos que sapphirine, demantoid garnet, iolite, cassiterite and aumentan el contraste microscopico y su spodumene. M.O'D. utilizaciön en gemologia. (The use of diapositives to augment microscopic contrast and its utilization Gem Bulletinen. 1986. 1. Published by Stockholms in gemmology.) Boletin del Institute Gemolôgico Gemmologiska Förening, Stockholm, Sweden. Espanol, 21, 13-19, 11 figs in colour. This new journal is reproduced from typescript An explanation of the use of phase contrast and contains papers on turquoise and andalusite, microscopy for the study of gemstones. M.O'D. with shorter notes. M.O'D. J. Gemm., 1986, 20, 3 193

Book Reviews

BRICE, J.C. 1986. Crystal growth processes. Blackie, the book which is highly recommended for anyone Glasgow: Halsted Press, New York, pp. x, 298. with an abiding interest in the formation of Illus. in black-and-white. £29.00. crystals. The text is not too rigorous for general Before this book was published there was no consumption. M.O'D. single place in which the student could look for detailed accounts of crystal growth processes; the BURCH,C.R. 1986. Gemstone inclusions. Sunderland literature contains many such descriptions but they Polytechnic, Sunderland. Unpaginated. Price on are nearly always in expensive journals which are application. hard to locate or in even more elusive conference This is a short descriptive catalogue of an proceedings. Many descriptions assume some degree exhibition of photographs of gemstone inclusions, of prior knowledge on the part of the reader and the display being held at the Geological Museum, most are concerned with specific materials. London, from 25 March to 31 May 1986. Exhibits In this book the processes themselves are were 100mm x 120mm on Kodak Ektachrome 50 examined after an introductory section dealing with Professional EPY 135 transparency film. M.O'D. the need for single-crystal materials and with the basic concepts of crystallization. Up to 15 000 DIETRICH, R.V. 1985 The tourmaline group. Van tonnes of single crystals are produced world-wide Nostrand Reinhold, New York. pp. xiii, 300. each year for electronics and similar applications as Illus. in black-and white and in colour. £38.45. well as for ornament in jewellery. There is thought There has been no separate monograph on the to be an annual increase in the rate of demand for tourmaline group of minerals since the two books these substances in the order of 7%. The chapter on by A.C. Hamlin, The History of Mount Mica and The basic concepts explains the nature of crystals, their tourmaline, both published in the last century and structures and imperfections, and gives particularly now highly desirable collectors' pieces. Both were valuable notes on phase relations, growth kinetics enthusiastic reports'by a collector and as the state of and transport processes. mineralogy at the time did not allow for the Descriptions of the different growth processes grouping of the tourmaline group minerals into the come next and deal with the Bridgman and related classes which we know today the present book is processes first, followed by the Czochralski and particularly welcome. With all the techniques of other melt growth techniques. Apparently overall modern laboratories at his disposal, the author 80% of melt-grown crystals are available from briefly reviews nomenclature and then outlines the Bridgman and Czochralski methods of growth, but different species comprising the tourmaline group. the other 20% can only be obtained by other Gemmologists may be surprised to learn that there methods (flux-melt growth, skull-melting, Verneuil, are eight species with distinct compositions and chemical vapour transport, hydrothermal, growth many more names which have been assigned to from solid phases). All these methods are described colour varieties and hypothetical end-member and each section has its own bibliography. compositions. The author feels that some old- A useful and interesting concluding chapter established names, particularly the colour-based explains why particular methods of growth are ones, should now be abandoned in the interests of chosen and a postscript suggests that while the clarity. demand for single crystal materials is likely to Crystal form and habit are treated next and some increase, automation of much of the growth process interesting diagrams have been taken from several will mean that there will not be a corresponding early authorities. Structure and chemical com­ increase in the number of workers in the field. position are then discussed with a most useful Those already in it will be concerned with account of solid solutions - a topic still not furthering study on the complex interactions of completely understood. Inclusions and the inter- growth parameters on the characteristics of the growth of tourmaline with other minerals have a crystal that they grow. These topics are treated in chapter of their own, which is followed by a 194 J. Gemm., 1986, 20, 3 discussion of colour. In this and the following MAI, P. 1983. La connaissance des gemmes et de leurs sections on physical and optical properties a subsituts. Part 1. (The knowledge of gems and number of useful tables and diagrams are provided; their substitutes.) Published by the author at in particular those of absorption spectra should be Anvers, pp. 158. Price on application. consulted when the question of colour alteration This work forms part of a course on gemmology arises. The remainder of the book deals with the and is unexceptional. M. O ' D. occurrence of tourmaline; there are appendices, one of them listing localities which have yielded notable specimens or gem quality material, and a fine SINKANKAS, J. (READ, P., ed.) 1986. Beryl. bibliography of nearly 1,000 general and cited Butterworths, London, pp. xiii, 225. Illus. in references. A more complete bibliography, of some black-and-white and in colour. £24.00. 2,500 entries, can be consulted on cards at the This is an abridgement of the author's Emerald Department of Mineral Sciences at the National and other beryls*, 1981, Chilton Book Co., Radnor, Museum of Natural History, Washington, DC. Pa., USA. The material has been up-dated in some This is a book which I hope will be the forerunner places and the over-all emphasis is on the gem- of others dealing in this kind of depth with mological aspects of the beryl minerals. The individual gem species. The quality of production is abridgement has been very successful and the high and the colour pictures, though few in presentation and price are very good. M.O'D. number, quite magnificent. M. O ' D.

* Reviewed in J.Gemm., 1982, XVIII, 3, 252-3. J. Gemm., 1986, 20, 3 195

Proceedings of the Gemmological Association of Great Britain and Association Notices

OBITUARY FRANCIS SIDNEY HOPE TISDALL was born on 10 August, 1899, and died on 23 January, 1986. To his colleagues and friends he was known as Sid, and will be well remembered by that name. He was born in England, but his family emigrated shortly after his birth to New Zealand where he lived until he was 14 years old. During this time he attended Wellington College where 'mens sana in corpore sano' (as he would have said) was the rule. His father being in the sports outfitting business, Sid needed no encouragement to become the keen cyclist and walker that characterized him during the whole of his life. He also showed considerable scholastic ability. Just before the First World War he returned to England where he attended Four Oaks College, near Sutton Coldfield, Warwicks. Although a good academic scholar, he was attracted to a more adventurous life, and giving his age as 16, in 1914 he enlisted in the Forces so that he could join an Army Band and enjoy his pursuits of drum, piccolo and flute playing. He was on active service for four years and may have remained longer in the army, but his grandfather, the jeweller Samuel Hope, wrote to his Commanding Officer telling him that a job for young Sidney was awaiting him in the family Sid Tisdall business. Sid duly joined the family company, but to quote athlete winning awards for ice dancing, acrobatic from a personal letter, he says ' . . when Works diving and walking 50 miles on his 60th birthday, in Manager, Gem Ring Department Manager, common with many others denied the luxury of a Designer and Gemmologist (yes the lot!) at my late university education, he continued to pursue his grandfather's firm ... I preferred to be a "back­ studies with great diligence and concentration. He room" boy'. obtained the Fellowship Diploma with Distinction In 1939 he left the company to start his own in 1935, and the Diamond Diploma in 1966. In business buying and selling second-hand jewellery 1938 he was awarded the Certificate of Merit for in Manchester and Liverpool. At the end of the Jewellery Design at the then Vittoria Street School Second World War he moved to Rhos-on-Sea which for Jewellers and Silversmiths, Birmingham. enabled him to be nearer to his beloved mountain His keen interest in gemmology enabled him to scenery, but after an unsuccessful business venture obtain the post of Lecturer in Gemmology at this returned to Walmley. Here he worked as a jewellery College and he began teaching in 1938. This designer and consultant, retiring from the firm of activity, although to be his main interest for the rest Deakin and Francis at the age of 67. of his life, did not prevent him from teaching Sid was a man of many parts. Although a fine classical Greek, taking vigorous exercise hill walk- 196 J. Gemm., 1986, 20, 3 ing, pursuing his keen interest in photography and the increase and improvement of the specimen forming the North Birmingham Cycling Glub. collection and the instrumentation in the He was a prolific writer. Many of his old students department. will recall his beautifully written RI and SG tables Jean was the principal organizer for the South and his 'full answers to questions likely to appear in Yorkshire Branch and a diplomatic co-ordinator. the next examinations'. The latter would sometimes Her quiet efficiency and gentle manner will be occupy three pages of meticulous handwriting. As greatly missed by all the members. would be expected, bad spelling was an anathema to him and he was much troubled by the decline in the • • • writing ability of his students. As gemmological correspondent of the British It is with great regret that we announce the death Jewellery and Watch Buyer, he contributed many of Mr Harry Wheeler, F.G.A., former Secretary of useful and interesting articles and published many the Association, on 5 June, 1986. A full obituary papers in The Gemmologist, The Journal of Gem- notice will appear in the October issue of the mology and Gems. He was a thorough gemmologist Journal. of the old practical school, being a great advocate of the X10 lens and down-to-earth commonsense. In GIFTS TO THE ASSOCIATION some circles in London he was known as the The Council of the Association is indebted to Mr 'Robert Webster of the Midlands'. R. Holt, London, for the following gifts: an agate In 1977 on the 25th Anniversary of the formation engraved with the head of a queen; a specimen of of the Birmingham Branch of the Gemmological rough African emerald of 103.5 ct; an andradite Association, he was given the Sir James Walton variety melanite garnet crystal group on matrix Memorial Library Award 'in sincere recognition of from Italy; a cleavage piece of chrome fluorite from many years hard work for gemmology in Zambia; garnet and tourmaline rough from Africa. Birmingham'. His wife Violet died in 1979 after a long period of NEWS OF FELLOWS decline during which time Sid attended devotedly Mr Alan Hodgkinson, F.G.A., toured Hong to her needs. He was a religious, God-fearing man, Kong and Bangkok in March 1986. He organized who knew his Bible well and did his best to live by two two-day practical gemmology courses, as well its teaching. as giving several lectures to the Hong Kong Those of us who knew him closely will remember Gemmological Association and the Asian Institute his intense interest in and dedication to his subject, of Gemmology. his enthusiasm for teaching, his forthright manner and his kindness. On 9 May, 1986, Dr J.B. Nelson, Ph.D., An attack of shingles in later life dealt a severe F.G.S., C.Phys., F.Inst.P., F.G.A., gave a lecture blow since his eyesight became impaired. This was with demonstrations using large scale atomic followed shortly by a severe stroke. He struggled to structure models on 'The structure and chemistry continue with an active life for three years, but died of gemstone minerals' to the Sussex Mineral and peacefully from heart failure. Lapidary Society at Hay wards Heath. He leaves two sons, Neil and David, and a On 4 June, 1986, Dr Nelson gave a talk to the daughter Barbara. Sid was buried on 30 January at Brent Geological Society, Brent, entitled 'Diagnostic Sutton Coldfield Cemetary. He will be missed by inclusions in faceted gemstones'. He employed a his many friends, but he will not be forgotten. gemstone immersion microscope of his own design to project images of the internal microstructures of A.D.M. some thirty stones directly on to a screen. Its most valuable feature proved to be its ability to isolate a • • • particular image from the general 'optical noise' by making controlled movements of the stone while Miss Jean Isobel Platts, F.G.A. (D.1970), immersed in the matching liquid. Sheffield, died in hospital on 25 February, 1986. On 28 May, 1986, at the Annual Conference of Jean was a founder member of the South the National Association of Goldsmiths held at the Yorkshire and District Branch of the Gemmological Hythe Imperial Hotel, Hythe, Mr Kenneth Scarratt, Association which was formed in 1977. She gave F.G.A., gave an illustrated lecture entitled 'Con­ continuing and devoted service as a committee trasting gem mining techniques'. member, Secretary and Chairman. She was formerly a teacher of Gemmology and Diamond Diploma courses at the Sheffield City Polytechnic, where she was directly responsible for J. Gemm., 1986, 20, 3 197

MEMBERS' MEETINGS method. He also illustrated the optical ray paths London followed within a polished perspex model of the On 22 April, 1986, at the Flett Theatre, profile of a brilliant-cut gemstone. Geological Museum, Exhibition Road, South On 15 May, 1986, at Church House, Mr Alec Kensington, London S.W.7, Dr Charles E.S. Farn, F.G.A., gave a talk entitled 'Gemmological Arps, F.G. A., of the National Museum of Geology recollections'. and Mineralogy, Leiden, The Netherlands, gave an illustrated talk entitled 'Gemstones from Indonesia'. On 13 May, 1986, at the Flett Theatre, South Yorkshire and District Branch following the Annual General Meeting (see p. 198), On 22 May, 1986, at the Sheffield City a Gemmological Forum was held, chaired by Mr Polytechnic, Pond Street, Sheffield, Mr G.A. David J. Callaghan, F.G.A., Chairman of the Massie gave a practical demonstration of his Association. The panel consisted of the following: lapidary skills. There was also a range of gemstones Mr Alan Jobbins, B.Sc, F.I.M.M., F.G.A., Dr available for identification. Roger Harding, B.Sc, D.Phil., F.G.A., Mr Mrs Susan E. Payne, B.A., F.G.A., has succeeded Kenneth Scarratt, F.G.A., Dr George Harrison- Miss Jean Platts (see Obituary p. 196) as Hon. Jones, B.Sc, Ph.D., F.G.A., Ms Diana Foley and Secretary of the Branch. Mr Christopher R. Cavey, F.G. A. Subjects covered included the following: how to identify jade in the shop; the glass infilling of rubies and sapphires; COUNCIL MEETING understanding the relationship between the various At the meeting of the Council held on 22 April, ways of presenting absorption spectra; faceting 1986, at the Royal Automobile Club, 89 Pall Mall, easily cleavable material; eighteenth and nineteenth London S.W.I, the business transacted included century cut steel jewellery as a substitute for gold the election of the following: and diamonds; and how one might attempt to date carved intaglios. Fellowship On 27 May, 1986, at the Flett Theatre, Abbot, Anita M., Phoenix, Ariz., USA. 1985 Mr Gunnar Raade, Curator of Minerals at the Arroyo Llorens, Maria C, Madrid, Spain. 1985 Mineralogisk-Geologisk Museum, Oslo, Norway, Coleman, Walter D., Valley Falls, Kan., USA. gave an illustrated talk entitled 'Gemstones of 1968 Norway'. Ellis, John R., Norwich. 1961 Gascon Cuello, Fernando, Zaragoza, Spain. 1985 Midlands Branch Kai, Kock M., Kowloon, Hong Kong. 1985 On 21 March, 1986, at Dr Johnson House, Bull Little, Derek, Dundee, Scotland. 1981 Street, Birmingham, Mr Alec Farn, F.G.A., gave Liyanaarachchi, Tudor P., Colombo, Sri Lanka. an illustrated talk entitled 'Jade and its simulants'. 1985 On 25 April, 1986, at Dr Johnson House, the Spreckley, Vaughan G.M., London. 1985 Annual General Meeting was held, at which Mr P. West, F.G.A., was elected Chairman and Mr D.M. Transfers from Ordinary Membership Larcher, F.G.A., re-elected Secretary. Following to Fellowship the Annual General Meeting, Mr Owen Smyth, of Niklewicz, Danusia, Santa Monica, Calif., USA. Town Talk Polish, gave an illustrated talk entitled 1985 'The scientific approach to cleaning metals and Perera, G.H. A.P., Mount Lavinia, Sri Lanka. 1979 gemstones'. Waddington, Clive, Harrogate. 1985 Ordinary Membership North West Branch Amemiya, Tamami, Saitama Pref., Japan. On 17 April, 1986, at Church House, Hanover Asano, Kimiko, Bromley. Street, Liverpool 1, Dr J.B. Nelson, Ph.D., Barber, Roxey L., Encinitas, Calif., USA. F.G.S., C.Phys., F.Inst.P., F.G.A., gave a talk Bateman, Linda D., Vancouver, BC, Canada. entitled 'How can I identify this transparent Becker, Thomas, Berlin, Germany. euhedral crystal?'. Using a vertical optical gonio­ Bee ver, Richard H., Orpington. meter, he was able to demonstrate the practical Beizer, Sameul, New York, NY, USA. 1985 measurement of all the interfacial angles of a Blake-Eckstein, Adrienne, Indianapolis, Ind., crystal, thus leading to its identification by the USA. Barker Method. The same device was used to show Bonds, Bobbye F., Magnolia, Ariz., USA. how the RIs and dispersions of faceted stones could Bramsden, Manny, Maidenhead. be determined by means of the minimum deviation Canty, Jess, London. 198 J. Gemm., 1986, 20, 3

Chapman, Janet E., Poole. Ushio, Tsutae, Fukuoka Pref., Japan. Collin, Alan A., Billingshurst. Ushio, Yoshiko, Tokyo, Japan. Cooper, Malcolm D., Standon. Wackerlig, Marc O., Winterthur, Switzerland. Davoudi, Vivien, Troinex, Switzerland. Yaku, Mihoko, Osaka, Japan. Doland, Gregory S., Farnham. Yamasa, Toshiko, Tokyo, Japan. Edwards, Charlton T.K., Harpenden. Yoshimoto, Misako, Munakata-gun, Japan. Eguchi, Yukio, Osaka City, Japan. Ekman, Anders, Malmoe, Sweden. ANNUAL GENERAL MEETING 1986 Epa, Widanagamage, Mount Lavinia, Sri Lanka. The 55 th Annual General Meeting of the Fatalas Papadopoulos, Costas, Athens, Greece. Association was held on Tuesday, 13 May, 1986, Furukawa, Junko, Kyoto City, Japan. at the Flett Theatre, Geological Museum, Exhibition Genot, Luc, Brussels, Belgium. Road, South Kensington, London S.W.7. Goddard, John D., Hastings. Mr David J. Callaghan, F.G.A., the Chairman of Gordon, Don D., Warwick, WA, Australia. the Association, presided over the meeting. He Hagnas, Lloyd, San Diego, Calif., USA. referred to some of the items mentioned in the Hagon, Clive L., London. Annual Report, and announced that the Basil Hallinan, John W., Crecora, Co. Limerick, Ireland. Anderson Appeal launched in November 1984 for Harrison, Rouer F.J., Kings Langley. the purchase of the Basil Anderson Spectrophoto­ Head, Judy E., Newdigate. meter had reached its target figure of £25 000. Hirai, Junko, Tokyo, Japan. Referring to the examinations, Mr Callaghan said Hirama, Katsunori, Tokyo, Japan. that he was pleased to report that the Tully Medal Hirose, Sairi, Nagasaka Pref., Japan. had been awarded two years consecutively. In 1985 Holmes, Christopher W., Stockport. this Medal was awarded to Mrs Gwyneth Green, Ishimoto, Kazuko, Hyogo Pref., Japan. who is the first student to be awarded both the Kato, Kuniako, Osaka City, Japan. Anderson and Tully medals. The awards had been Kenna, Sean N., Leixlip, Co. Kildare, Ireland. presented by Mr Richard T. Liddicoat, Jr., Hon. Kent, Jeni, Hyde Park, SA, Australia. F.G.A., Chairman of the Board of the Gemological Kinder, Lawrence V., Bangor, Co. Down, Institute of America. N. Ireland. The Chairman paid tribute to the work of Mr Kunishima, Ikuko, Osaka City, Japan. J.R.H. Chisholm for his years of editorship of the Logan, Joan A., Hounslow. Journal, who retired at the end of the year. He then Masuoka, Yoshima, Matsubara City, Japan. thanked Mr Alan Jobbins who had succeeded John Matsubara, Yoshiko, Hirakata City, Japan. Chisholm as Editor, and referred to the new format Matsuyama, Yasuo, Osaka City, Japan. of the Journal, which had been well received by Mellor, Karen, Pinner. members. Miyabayashi, Yuki, Kawachi-negano City, Japan. Continuing, Mr Callaghan reported that the Mochinaga, Schoichi, Aira-gun, Japan. Preliminary section of the new home study course Morrison, Laurence, Upminster. in gemmology would be commencing in September Murata, Fumiko, Osaka, Japan. 1986. He thanked Mr Jonathan Brown for his Nakagawa, Kyoko, Kobe City, Japan. tremendous achievement in obtaining a grant of Nonaka, Chikako, Kuki City, Japan. £30 000 for the course from the Distributive Ono, Takahiro, Tokyo, Japan. Industry Training Board Trust. Ozaki, Keiko, Kawanishi City, Japan. During the year a new Executive Committee had Pay, Duncan L., Fife, Scotland. been formed, and the Chairman thanked all Penfold, Edward,, Jeddah, Saudi Arabia. members of the Council, Examiners and Instructors, Perkins, Sarah, London. for their help and support during the year. Pitre, Judith M., Imperial Beach, Calif., USA. Mr Nigel Israel, the Honorary Treasurer, pre­ Rockwell, Alan M., Southfield, Mich., USA. sented the audited accounts for the year ended Rubilotta, Michel, Rousset, France. 31 December, 1985, illustrated by coloured charts. Sano, Jun, Hiroshima Pref., Japan. The adoption of the Report and Accounts was duly Shaw, Patricia V., Leeds. proposed, seconded by Mr Alan Jobbins and Silvestre, Jean-Claude, Nimes, France. carried. Skinner, Graham D., Worthing. Sir Frank Claringbull, Mr David Callaghan, Mr Spuida, Bernhard, Pfronten, W. Germany. Noel Deeks and Mr Nigel Israel were then re­ Takizawa, Toshiko, Tokyo, Japan. elected as President, Chairman, Vice-Chairman Tohyama, Masuo, Osaka, Japan. and Honorary Treasurer respectively. Mrs S. Twigg, Fiona, Mount Kennedy, Co. Wicklow, Hiscox and Messrs. D. Inkersole, B. Jackson, M. Ireland. J. Gemm., 1986, 20, 3 199

O'Donoghue, P. Read and C. Winter were re­ 'window' and drying a specimen on paper a vivid elected to the Council. yellow stain was noted and an acidic liquid oozed Messrs. Ernst and Whinney were reappointed from the crystal. Washing the specimen with dilute Auditors, and the proceedings then terminated. detergent caused it to come apart, revealing a green dye on flat pieces of quartz(?) which had been GEMSTONES UNDER THE MICROSCOPE gummed together to form the fake. Readers should An exhibition of photographs by Mr C.R. Burch, beware of such imitations. B.Sc, F.G.S., was held at the Geological Museum, Exhibition Road, South Kensington, London CORRIGENDA S.W.7, from 25 March to 31 May, 1986. Charac­ On p. 52 above, the caption to the photograph teristic inclusions occurring in both natural and uses the term 'etch pits'. In fact, they are raised man-made gemstones were illustrated in 30 full- tetrahexahedral formations sometimes known as colour enlargements. 'quadrons'. On p. 103 above, the caption to the photograph at GEMMOLOGICAL COURSES the top of the left-hand column has been omitted. It Retail Jeweller should read: 'Fig. 4. Paragasitic hornblende crystal The Retail Jeweller continues its residential (NMNS 46661) from Soper River, Baffin Island, courses on gem identification this autumn at Upton NWT, Canada, with facetable rough and 3.00 ct Hall, Newark, Notts. Mr Alan Hodgkinson, emerald cut hornblende (NMNS 20896)'. F.G.A., is the course leader, assisted by Mr Patrick On p. 116 above, right-hand column, line 11, for Daly, F.G.A. The dates are as follows: 'and' read 'end'. 29-30 September, 1986. Two-day introduction to practical gem identification. 1-3 October, 1986. Three-day practical gem identi­ fication for second year students and refresher course for Diploma holders. Full details from the Retail Jeweller, 100 Avenue Road, London NW3 3TP.

Genesis Courses for overseas students or those home students wishing to complete the full course for the Gemmological Association's Diploma examination in one year are offered by Genesis. Courses start in mid-September and continue to the following June. Tuition occupies two full days per week and is intensive. Courses are limited to eight students and include visits to gem centres such as Idar-Oberstein and Antwerp. Full details from Colin Winter, F.G.A., Genesis Design Jewellery Ltd, 21 West Street, Epsom, Surrey, KT 18 7RL.

INDIA GEMS AND JEWELLERY FAIR The 1986 Fair is to be held from 4 to 8 September at the Taj Mahal Hotel, Bombay, India. For details contact IG J Fair 1986, c/o Hindustan Diamond Co. Ltd, 15 Atlanta, Nariman Point, Bombay 400 021, India. Telex 011-4710 HDCL IN.

FAKED EMERALD CRYSTALS FROM AMERICA Three 'emerald' crystals weighing 52, 33 and 20 grams were offered to Bernice Backler, a jeweller in Pinetown, South Africa. The locality was given as Chitanti District, Zambia. The crystals appeared to have a coating of mica-schist and on cutting a GESTRUSTRUOLOGleATS LTD.TS LTD.STRUSTRU TS LTD.TS LTD. 1101101Gre I 1\ n

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The Arms and Crest ofthe octahedra and the gem-set ring Association, conferred by a grant indicates the use of gems in of Arms made by the Kings of ornamentation. The lynx of the Arms under royal authority. crest at the top was credited, in The cross is a variation of that ancient times, with being able to in the Arms of the National see through opaque substances. Association of Goldsmiths of He represents the lapidary and Great Britain and Ireland. In the student scrutinizing every the middle is a gold jewelled aspect of gemmology. In the book representing the study of paws is one of the oldest heraldic gemmology and the emblems, an escarbuncIe, to examination work of the represent a very brilliant jewel, Association. Above it is a top usually a ruby. The radiating arms plan of a rose-cut diamond inside suggest light diffused by the a ring, suggesting the scrutiny of escarbuncIe and their tips are shown gems by magnification under a lens. as jewels representing the colours of The lozenges represent uncut the spectrum.

Historical Note The Gemmological Association of Great Canadian Gemmological Association, the Gem Britain was originally founded in 1908 as the and Mineral Society of Zimbabwe, the Education Committee of the National Gemmological Association of Hong Kong, the Association of Goldsmiths and reconsti tuted Gemmological Association of South Africa in 1931 as the Gemmological Associa tion. Its and the Singapore Gemologist Society. name was extended to Gemmological The]ournal ofGemmology was first Association of Great Britain in 1938, and pu blished by the Association in 1947. It is a finally in 1944 it was incorporated in that name quarterly, published in January, April, July, under the Companies Acts as a company and October each year, and is issued free to limited by guarantee (registered in England, F eHows and Members of the Association. no. 433063). Opinions expressed by authors are not Affiliated Associations are the necessarily endorsed by the Association. Gemmological Association of Australia, the

Notes for Contributors The Editors arc glad to consider original is consistent with clear indication of the articles shedding new ligh ron subj ects of content of the paper. It should be followed by gemmological interest for publica rion in the the names (wi th initials) of the au thors and by Journal. Articles are not normally accepted their addresses. A short abstract of 50-100 which have already been pu blished elsewhere words should be provided. Papers may be of in English, and an article is accepted only on any length, but long papers of more than the understanding that (1) full information as 10 000 words (unless capable of division in to to any previous publication (whether in parts or of exceptional importance) arc English or another language) has been given, unlikely to be acceptable, whereas a short (2) it is not under consideration for publication paper of 400-500 words may achieve early elsewhere and (3) it will not be published publication. elsewhere without the consen t of the Editors. Twenty five copies of individual papers are Papers should be submitted in duplicate on provided on request free of charge; additional A4 paper. They should be typed with double copies may be supplied, but they must be line spacing with ample margins of at least ordered at first proof stage or earlier. 25mm all round. The title should be as brief as Vol. 20 No. 3 July 1986

TheJournal of Gemmology

Contents

Inclusions in opal E. Gübelin and J.I. Koivula 139

Notes from the Laboratory - 7 K. Scarratt 145

Some observations on brown tourmalines from Elahera, Sri Lanka U. Henn andM. Schramm 154 A re-investigation of gahnospinels from Sri Lanka K. Schmelzer and H. Bank 157

Some unusual cat's-eyes Y.Ito 161

A peculiar inclusion in a yellow corundum from Malawi O. GrubessiandR. Marcon 163

The very sphinx of diamonds A. E. Farn 166

A treatment procedure for improving colour and quality of zircons M.S. Rupasinghe and A. Senaratne 168 The brilliant cut - analysis of weight by calculation SJ.A.Cume 171

Light, heavy and rare minerals in the washed gem gravels of Sri Lanka M.S. Rupasinghe, A: Senaratne and C.B. Dissanayake 111

Gemmological abstracts 185

Book reviews 193

Proceedings of the Gemmological Association of Great Britain and Association Notices 195

Copyright © 1986 Gemmological Association of Great Britain Registered Office: Saint Dunstan's House, Carey Lane, London EC2V 8AB

ISSN: 0022-1252

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