Volume 20 No. 2 April 1986 GAGTL EDU Set 3 ^eJournal of Gemmology

GEMMOLOGICAL ASSOCIATION OF GREAT BRITAIN OFFICERS AND COUNCIL

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

Fellows 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.Eng., P. J. E. Daly, B.Sc. D. Morgan M.I.E.E., M.LE.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.Eng., F.R.Ac.S.

Branch Chairmen: Midlands Branch: C. L. Hundy, F.G.A. North-West Branch: S. Hill, F.G.A. Sowh Yorkshire & Distria Branch: J. I. Reynolds, F.G.A.

Examiners: E. A. Jobbins,B.Sc., F.I.M.M., F.G.A. A. J. Allnutt, M.Se.,Ph.D., F.G.A. R. R. Harding, B.Sc., D.Phil., F.G.A. G. H. Jones, B.Se., 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. Woodward, B.Se., F.G.A. A.E. Farn, F.G.A. M. Font-Altaba, D.Se. J. M. Bosch-Figueroa, D.Se. M. Virkkunen, M.Phil., F.G.A.

Instructors: 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.Se., F.G.A.

Editor: E. A. Jobbins, B.Se., 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 Lenan, F.G.A. Deputy Secretary: Jonathan Brown, Barrister-at-Law, F.G.A.

Saint Dunstan's House, Carey Lane, London EC2V SAB (By Goldsmith's Hall) TeJephone:Ol~726 4374 J.Gemm., 1986,20,2 73

TheJournalof Gemmology

VOLUME 20 NUMBER TWO APRIL 1986

Cover Picture Amerindian named 'Joseph' collecting jasper in the Ireng River at one of the Orinduik falls in Guyana, South America - see page 91. Photograph byJ.G. Gosling,F.G.A.

ISSN: 0022-1252 7744 J.Gemm.,1986,20,J. Gemm., 1986,20,22

GEMMOLOGICAL INSTRUMENTS LIMITED GEMMOLOGICAA wholly owned subsidiaryL of theINSTRUMENT Gemmological Association ofS Great LIMITE Britain D A Saintwholly Dunstan'sowned subsidiar House,y of the CareyGemmologica Lane,l Associatio Londonn oEC2Vf Great 8ABBritai n SainTelephone:t Dunstan' 01-7264374s House, CareCables:y Lane Geminst,, Londo nLondon EC2V 8AEC2B Telephone: 01-726 4374 Cables: Geminst, London EC2 THTHEE RETAIRETAILL JEWELLER'JEWELLER'SS GEM TESTING SET y assembled t Dialdex Refractometer,GEM fluid and TESTIN case GStone SE tongs T Polarizing increasin yfilter gassemble pressur yed assemblett d t increasin4-prongy gassemble pressurstone holder y LEDassemble increasin idealighty assemble l sourcedfog t increasinrpressur ytrad assemblede ttestineg tpressurd t e t increasin ideaRaynery assemblel fog increasinrDiamondpressur ytrad assemblede ttestin eTesterg tpressurd increasing pressure t pressure t increasinOPL Spectroscopeidea increasingn l pressurfothre tradpremises ideag epressure tltestin for trade t e testin increasin ideaMoe increasingn l Diamond pressurfothre tradpremises ideag epressur e Gauge tltestin for trade ideal XIOfor tradZeisse lenstestin n the premises tradChelseae testin Colour nFilter the premises 'Gem idea Testingl fon ridea 'thtrad byel B.Wpremisesefo testinr trad. Andersone testin ideaRaynerl fon ridea thtrad Polariscopeel premisesefo testinr trad e testin n the premisesn the premisesn the premises e premisesn the premisesn the premises

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TheThe RetailerRetailer SetSet hashas beenbeen especiallyespecially assembledassembled ttoo meemeett thethe needsneeds ofof thethe highighh streetstreet jewellejewellerr whowho isis undeunderr increasingincreasing pressurepressure ttoo identifyidentify gemstonesgemstones rapidly.rapidly. CompetitivelyCompetitively priced,priced, thethe SetSet isis idealideal forfor tradetrade testingtesting oorr satisfyingsatisfying customercustomer enquiriesenquiries onon thethe premises.premises. ToTo complementcomplement thethe Set,Set, a rangrangee ofof gemmologicalgemmological microscopemicroscopess andand gemstonegemstone specimensspecimens areare availableavailable fromfrom GemmologicalGemmological InstrumentsInstruments Limited.Limited. TheThe RetailerRetailer SetSet (Cat.(Cat. NoNo.. RjSl)RJS1) PricePrice £519.95£519.95 + pP & P + VATVAT JJ.. Gemm.,Gemm., 1986,20,21986, 20, 2 7575

NewNew developmentsdevelopments inin spectroscopicspectroscopic methodmethodss forfor detectingdetecting artificiallyartificially colouredcoloured diamondsdiamonds

G.S. Woods* and A.T. CollinsCollinst†

* CSOCSO ValuationsValuations Ltd,Ltd, 1717 CharterhouseCharterhouse Street,Street, London,London, ECINEC1N 6RA6RA t† WheatstoneWheatstone PhysicsPhysics Laboratory,Laboratory, King'sKing's College,College, London,London, WC2RWC2R 2LS2LS

IntroductionIntroduction FouFourr parameterparameterss ('th('thee fourfour Cs'Cs')) normallynormally deter­deter­ minminee thethe valuevalue ofof a polishepolishedd diamondiamondd gemstone:gemstone: thethe caratcarat weight,weight, ththee cutcut,, ththee clarityclarity anandd thethe colourcolour.. ForFor Colourless a diamonddiamond ofof a givengiven weight,weight, withwith a well-propor­well-propor­ tionedtioned cucutt anandd a highighh claritclarityy grade,grade, ththee coloucolourr hashas a profounprofoundd influenceinfluence oonn ththee valuvaluee ofof ththee stone.stone. DiamondDiamondss whicwhichh appearappear completelycompletely colourlesscolourless araree ververyy rarraree andand commancommandd ththee higheshighestt prices.prices. HoweverHowever,, a larglargee proportioproportionn ooff gegemm qualityquality diamonds,diamonds, belonginbelongingg ttoo ththee so-calledso-called CapeCape Series,Series, exhibitexhibit variouvariouss degreedegreess ofof yellownessyellowness dowdownn ttoo a palepale w strawstraw colourcolour.. EvenEven a hinhintt ofof thisthis yelloyelloww colorationcoloration :::> Colourless - soso faintfaint thatthat a laymanlayman wouldwould notnot noticenotice itit -- ....J« significantlysignificantly reducesreduces thethe valuevalue ooff ththee diamond.diamond. AsAs > thethe yelloyelloww coloucolourr becomebecomess moremore andand mormoree propro­­ nouncednounced,, soso thathatt iitt becomebecomess obviousobvious eveneven toto thethe untraineuntrainedd eye,eye, thethe valuvaluee ofof ththee diamondiamondd fallsfalls furtherfurther.. Occasionally,Occasionally, howeverhowever,, diamonddiamondss areare foundfound inin naturnaturee whichwhich areare ooff excellenexcellentt gemgem qualityquality andand whichwhich havehave a full-bodiedfull-bodied yellow,yellow, goldegoldenn oorr amberamber colourcolour.. SuchSuch stonesstones araree termetermedd 'fancies''fancies'.. TheseThese DEPTH OF COLORATION diamondsdiamonds,, whewhenn properlproperlyy cutcut andand polishedpolished,, areare onon groundsgrounds ofof botbothh rarityrarity anandd attractivenesattractivenesss generallygenerally moremore valuablvaluablee thathann thosthosee withwith ththee lessless definitedefinite palepale FigFig.. 11.. ThiThiss diagramdiagram illustratesillustrates,, inin a schematischematicc way,way, howhow ththee yellowyellow colourcolourss ofof ththee loweslowestt categoriescategories ooff thethe CapeCape valuevalue ofof a cutcut andand polishedpolished diamonddiamond variesvaries with with the the depth depth SeriesSeries.. InIn FigFig.. 1 wewe represenrepresentt iinn a schematicschematic wayway ofof yellowyellow colorationcoloration.. hohoww marketmarket forceforcess determindeterminee ththee valuevalue ofof diamondsdiamonds havinhavingg differendifferentt depthsdepths ofof yelloyelloww coloration.coloration. WeWe propertiepropertiess ofof diamonddiamond,, includingincluding investigationsinvestigations ofof noticnoticee thatthat,, althougalthoughh thethe strongly-colouredstrongly-coloured yellowyellow ththee poinpointt defectdefectss whicwhichh araree ththee originsorigins ofof colour,colour, fancyfancy diamonddiamondss areare nowhernowheree nearnear asas valuablevaluable asas andand thisthis iiss stillstill aann activactivee field ofof investigatioinvestigationn inin otherwiseotherwise comparablcomparablee colourlesscolourless stones,stones, the theyy cancan manmanyy laboratories.laboratories. commandcommand a pricpricee welwelll aboveabove somesome ofof ththee diamondsdiamonds ThThee colourcolour produceproducedd bbyy irradiatioirradiationn andand heatingheating nearnear thethe middlmiddlee ooff ththee distribution.distribution. (called(called 'treatment'treatment'' inin thethe gegemm tradetrade)) addsadds ttoo thatthat ResearchResearch worworkk onon diamondiamondd durinduringg ththee 1950s,1950s, alreadyalready presenpresentt inin thethe diamond.diamond. HenceHence,, consideringconsidering notablnotablyy bbyy Dugdale(I)Dugdale(1) andand ClarkClark anandd co-workers(2,3),co-workers(23), diamondsdiamonds frofromm neanearr ththee minimuminimumm poinpointt inin FigFig.. 1,1, showedshowed thathatt iitt was possiblpossiblee artificiallyartificially ttoo colourcolour thethe effecteffect ofof treatmenttreatment iiss toto intensifintensifyy theirtheir colour,colour, diamonddiamondss yelloyelloww oorr goldegoldenn bbyy subjectingsubjecting themthem toto anandd thusthus potentiallpotentiallyy ttoo enhanceenhance theirtheir value.value. AlthoughAlthough radiatioradiationn damagedamage inin a nuclearnuclear reactorreactor,, oror iinn a vavann dede manmanyy customercustomerss wouldwould bbee unablunablee toto tell,tell, bbyy eye,eye, GraafGraafff accelerator,accelerator, oror byby usinusingg ververyy intenseintense 'Y-ray7-ray whethewhetherr a fancfancyy yelloyelloww diamonddiamond was naturallnaturallyy oror sources,sources, andand thethenn heatingheating thethe specimensspecimens toto aboutabout artificiallartificiallyy colouredcoloured,, marketmarket forceforcess decreedecree thatthat thethe 800°C.800°C. ThisThis pioneerinpioneeringg worworkk ledled toto threthreee veryvery naturanaturall productproduct iiss moremore valuablevaluable thanthan ththee artificialartificial fruitfulfruitful decadesdecades ooff fundamentafundamentall researchresearch oonn physicalphysical oneone.. (Indeed,(Indeed, thithiss iiss truetrue forfor mostmost gegemm materials.materials.)) A

© CopyrightCopyright thethe GemmologicalGemmological AssociationAssociation ISSNISSN:: 0022-12520022-1252 7676 J.J.Gemm.,1986,20, Gemm., 1986,20,22 furtherfurther advantageadvantage ofof treatmenttreatment inin increasingincreasing thethe valuevalue ofof a stonestone isis thatthat thethe deeperdeeper colourcolour cancan hidehide ( 0 ) smallsmall crackscracks andand inclusions,inclusions, andand soso diamondsdiamonds withwith a relativelyrelatively lowlow clarityclarity gradegrade cancan bebe selectedselected inin thethe first instance.instance. TheseThese pointspoints were,were, ofof course,course, allall appreciatedappreciated atat anan earlyearly stagestage byby thethe gemgem industry:industry: consequentlyconsequently gem­gem- testingtesting laboratorieslaboratories world-wideworld-wide nownow oftenoften havehave thethe responsibilityresponsibility ofof decidingdeciding whetherwhether a particularparticular diamonddiamond hashas beenbeen treated.treated. ItIt shouldshould bebe notednoted thatthat ( b ) manymany treatedtreated diamondsdiamonds areare inin factfact legitimatelylegitimately soldsold asas such,such, withwith certificatescertificates statingstating thatthat thethe colourcolour isis UJ artificial.artificial. However,However, problemsproblems arisearise whenwhen attemptsattempts U areare mademade toto passpass offoff treatedtreated stonesstones asas naturalnatural yellowyellow Z fancyfancy diamonds.diamonds. < (II 0:: SpectroscopicSpectroscopic techniquestechniques a ( c ) AlthoughAlthough manymany diamondsdiamonds maymay appearappear toto havehave a III similarsimilar yellowyellow colour,colour, thethe wayway inin whichwhich theythey (II absorbabsorb lightlight maymay bbee veryvery different.different. TheseThese differ­differ­ < encesences cancan bebe partiallypartially revealedrevealed usingusing a simplesimple hand-heldhand-held spectroscope,spectroscope, andand veryvery considerableconsiderable advancesadvances inin examiningexamining diamondsdiamonds werewere mademade byby AndersonAnderson(4)(4) withwith suchsuch anan instrument.instrument. AbsorptionAbsorption linesfines inin diamonddiamond becombecomee muchmuch sharpersharper iiff thethe ( d ) diamonddiamond isis coolecooledd toto abouaboutt -150°C-150°C oorr lowerlower,, andand Scarratt(5)Scarratt(5) obtaineobtainedd farfar greatergreater sensitivitysensitivity withwith a hanhandd spectroscopespectroscope whe whenn thethe diamondsdiamonds werweree atat loloww temperaturetemperature.. ThThee handhand spectroscope,spectroscope, how­how­ everever,, hahass manmanyy limitations,limitations, anandd ththee majomajorr gem­gem- testintestingg laboratorielaboratoriess nownow useuse spectrophotometersspectrophotometers whicwhichh providprovidee a plotplot,, oorr spectrum,spectrum, showinshowingg howhow 404000 500500 600600 707000 stronglstronglyy ththee diamondiamondd iiss absorbinabsorbingg oveoverr a widewide rangrangee ooff wavelengthswavelengths.. ItIt iiss ofteoftenn advantageouadvantageouss toto WAVELENGTWAVELENGTHH (nm)(nm) recorrecordd a spectruspectrumm witwithh ththee diamondiamondd coolecooledd toto liquiliquidd nitrogenitrogenn temperaturtemperaturee (—196°C(-196°C)) oorr slightlyslightly FigFig.. 22.. AbsorptioAbsorptionn spectrspectraa ooff foufourr yelloyelloww diamondsdiamonds,, recordedrecorded aboveabove.. witwithh ththee samplesampless aatt rooroomm temperaturetemperature., (a(a)) iiss a typtypee Iblb diamondiamondd classifieclassifiedd aass canarcanaryy yellowyellow,, (b(b)) iiss a CapCapee serieseriess IInn FigFig.. 2 wwee shoshoww absorptioabsorptionn spectraspectra,, recordedrecorded diamonddiamond,, (c(c)) iiss aann ambeamberr diamondiamondd anandd (d(d)) iiss a treatedtreated aatt rooroomm temperaturetemperature,, ooff foufourr differendifferentt yellowyellow diamonddiamond.. diamonddiamondss - a canarcanaryy yellowyellow,, a deedeepp CapCapee yellow,yellow, aann ambeamberr yelloyelloww anandd a treatetreatedd yellowyellow.. AAtt firstfirst sighsightt twtwoo thingthingss mamayy seeseemm surprisingsurprising.. ThThee first iiss A precisprecisee assessmenassessmentt ooff ththee coloucolourr cacann bbee thathatt ththee diamonddiamondss havhavee a similasimilarr huehue;; anandd thethe obtaineobtainedd bbyy takintakingg ththee datdataa ooff FigFig.. 2 anandd calculat­calculat­ seconsecondd iiss thathatt thertheree shoulshouldd bbee ananyy probleproblemm imn iningg ththee chromaticitchromaticityy coordinatescoordinates(6)(6) .. ThesThesee araree detectindetectingg ththee treatetreatedd stonestone.. numbernumberss whicwhichh locatlocatee ththee coloucolourr iinn a twotwo­- ThThee reasoreasonn foforr ththee similaritsimilarityy ooff coloucolourr iiss dimensionadimensionall coloucolourr spacespace,, anandd whicwhichh araree aann relaterelatedd ttoo ththee responsresponsee ooff ththee humahumann eyeeye,, whicwhichh objectivobjectivee measuremenmeasurementt ooff ththee coloucolourr ooff aann articlearticle,, hahass ititss maximumaximumm sensitivitsensitivityy aatt abouaboutt 555500 nnmm andand aass woulwouldd bbee recorderecordedd bbyy a standarstandardd observerobserver cacann detecdetectt virtuallvirtuallyy nothinnothingg aatt wavelengthwavelengthss belobeloww undeunderr standardizestandardizedd conditionconditionss ooff illumination.illumination. 383800 nnmm oorr abovabovee 757500 nmnm.. MoreoverMoreover,, ththee coloucolourr (Th(Thee interesteinterestedd readereaderr iiss referrereferredd ttoo bookbookss bbyy receptorreceptorss iinn ththee eyeyee responrespondd onlonlyy ttoo ththee averagaveragee BillmeyeBillmeyerr anandd SaltzmanSaltzman(7),(7), GrahamGraham(8)(8) oorr WyszeckWyszeckii lighlightt levelevell anandd cannocannott senssensee sharsharpp absorptionabsorption anandd StilesStiles(9)(9) foforr a mormoree thorougthoroughh discussiodiscussionn ooff thithiss lineliness oorr subtlsubtlee variationvariationss iinn ththee lighlightt levellevel.. AAss farfar topitopicc thathann cacann bbee givegivenn here.here.)) ThThee chromaticitychromaticity aass ththee eyeyee iiss concernedconcerned,, thereforetherefore,, alalll fourfour coordinatecoordinatess woulwouldd agaiagainn shoshoww ththee similaritysimilarity diamonddiamondss araree simplsimplyy absorbinabsorbingg lighlightt aatt ththee betweebetweenn ththee colourcolourss ooff ththee foufourr diamondsdiamonds,, blue/violeblue/violett enendd ooff ththee visiblvisiblee spectruspectrumm anandd ssoo placinplacingg thethemm iinn fairlfairlyy closclosee proximitproximityy iinn coloucolourr appeaappearr yellowyellow.. spacespace.. J. Gemm., 1986, 20, 2 77

81 H3 ( a )

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«-t E 4 /A.J \J

11V 0 1 II II

8 ( b ) COEFFICIEN T

4 - ABSORPTIO N

595 nm n UI_I 400 450 500 550 600 WAVELENGTH (nm)

Fig. 3. Absorption spectra, recorded with the samples at liquid nitrogen temperature, of (a) a natural fancy yellow diamond and (b) a treated yellow diamond.

As noted above, the differences between the by Crowningshield(U) in 1957 on a large number of spectra shown in Fig. 2 should make it very easy treated and untreated diamonds indicated that to identify a treated diamond. The problem which the presence or absence of this absorption line arises is that the dominant absorption band could be used to indicate whether the colour of a produced in some diamonds by treatment is also cut and polished diamond was artificial or natural. found to occur naturally in certain stones(10). In However, in 1978, high temperature annealing Fig. 3 we show absorption spectra, recorded at studies by Collinsa2) showed that the 595 nm liquid nitrogen temperature, of a natural fancy absorption line can be destroyed (by heating yellow diamond and an artificially coloured treated diamonds to about 1000°C) without diamond. In both cases the colour is caused by significantly changing the colour. It is possible the H3 absorption band which has a sharp line at that this phenomenon has been known for many 503 nm. It is diamonds containing this absorption years by those operators who colour diamonds band which can pose the greatest problem to gem- artificially and try to sell them as natural fancy testing laboratories. Inspection of Fig. 3 shows stones. The fact that the 595 nm absorption line that there is an absorption line at 595 nm in the is not a reliable indicator of the history of a spectrum of the treated diamond that is not diamond has caused considerable anxiety, since present in the naturally coloured stone. Studies 1978, in the gem-testing centres. 78 J. Gemm., 1986, 20, 2

Research work on treated diamonds has con­ in the GR1 band(14), due to the vacancy. As the tinued in our laboratories, and as a result of this diamonds are heated at progressively higher work we can now set out a series of spectroscopic temperatures for a standard time interval (typically measurements which will indicate with a very one hour) the following behaviour of certain high degree of reliability whether a yellow or absorption bands is noted: brown fancy coloured diamond is naturally or a. At about 275°C the 595 nm line is first detected. artificially coloured. In the rest of this paper we So, too, is an absorption line at 1450 cm1 deal with the relevant point defects in diamond, (6897 nm) in the infrared spectral region. The summarizing previous work and incorporating interstitial atom produced by the irradiation is our present results at the appropriate points. believed to be involved in the formation of both Useful background reading may be found in of these centres. As the temperature is raised the articles by Anderson(13), Collins(14) and Woods(15). 595 nm line reaches its maximum intensity by about 800°C, and is reduced to zero after heating Point defects in diamond to about 1000°C(12). The 1450 cm1 line reaches In this section we shall be concerned with its maximum intensity at about 400°C and the nitrogen impurity which is present in most remains at this strength until about 1300°C. diamonds, with the vacancies and interstitials Prolonged heating at temperatures around which result from irradiation and with the effects of 1400°C is necessary to eliminate this absorption(15). heat treatment. It is believed that nitrogen is first b. At about 500°C the vacancies begin to move and incorporated in the diamond crystal, as it grows, in the GR1 absorption begins to decrease, finally the form of single nitrogen atoms on substitutional disappearing after heating at about 800°C. As the lattice sites (i.e. at those points in the diamond intensity of GR1 decreases, so, in a complemen­ lattice normally occupied by carbon atoms). For a tary fashion, do the intensities of the H3 small proportion of natural diamonds most of the (503 nm) and H4 (496 nm) lines increase. nitrogen is still present in this form, and the crystals Spectra of diamonds containing the H3 and H4 have a characteristic yellow colour. These are bands have been shown previously in reference classified as type lb diamonds and in some cases the 14, and it was emphasised there that it is colour may be described as a canary yellow06). The necessary to make measurements at high resolu­ absorption spectrum in the visible region for type lb tion with the diamond at low temperature if the diamonds is typified by that shown in Fig. 2a. H4 line is to be distinguished from the side-band For most diamonds the high temperatures of the H3 absorption system. The H3 centre is a (around 1000-1200°C) experienced over geological vacancy trapped at a nitrogen A-centre and the time-scales result in the nitrogen atoms moving H4 centre is a vacancy trapped at the nitrogen B- around in the crystal, ultimately forming small centre, and, for diamonds heated at temperatures aggregates. The first stage of aggregation produces up to 1200°C, the ratio of the H3:H4 line A-centres, which are made up of two nearest- strengths is proportional to the ratio of the A:B neighbour nitrogen atoms. The next dominant nitrogen concentrations. It has been reported stage of aggregation is the formation of B-centres, previously, and confirmed in the present investi­ which are believed to contain four nitrogen atoms. gation, that the relative strength of the H4 line Neither the A-aggregates nor the B-aggregates may be substantially reduced by heating the produce absorption in the visible region, so neither diamond at temperatures above about 1200°C. contributes to colour; however the conditions that Four hours heating at 1400°C can completely result in the formation of B-centres also produce N3 eliminate the H4 band in some diamonds. centres. It is the N3 centre, believed to contain c. The most important finding to emerge from our three nitrogen atoms, which, when present in research(17), as far as gem-testing laboratories are different concentrations, produces the yellow concerned, follows on from the preliminary colours of the Cape Series stones. The spectrum of work of Woods(15) on the Hlb and Hlc lines in the N3 centre is that shown in Fig. 2b. irradiated and annealed diamonds. These From this brief summary, we can make an absorption lines in the near infrared spectral important generalization: pale yellow diamonds region, at 2024 and 1936 nm respectively, are selected for treatment almost certainly have some shown in Fig. 4. The value of these lines in the nitrogen present in the B form. examination of treated diamonds stems from their annealing behaviour. Fig. 5a shows the Radiation damage decay of the GR1 and the growth of the H3 band Immediately after damage by high energy as the diamond is heated at temperatures electrons or fast neutrons, diamonds have a blue or between 400°C and 800°C, and we see that the green colour, primarily associated with absorption intensities of these bands behave in a comple- J. Gemm.,Gemm., 1986,1986,20,220, 2 7799

r...... 4 I E u HIb '-J 3 I- HIe z w ...... u ...... u... 2 u... w 0 u z 0 ...... 1 I- CL n::: 0 If) CD < 0 - 1900 1950 2000 2050 2100

WAVELENGTH (nm)

FigFig.. 4.4. AbsorptioAbsorptionn spectrum,spectrum, recorderecordedd witwithh thethe samplesample aatt liquidliquid nitrogenitrogenn temperature,temperature, showingshowing thethe HlHlbb andand HlHiec lineliness inin a treatedtreated diamonddiamond.. mentarmentaryy fashionfashion.. ThThee HH44 band,band, althougalthoughh notnot becausebecause ooff aann absorptioabsorptionn ofteoftenn produceproducedd aatt ththee reredd shownshown foforr ththee sakesake ofof clarityclarity,, behavebehavess likelike ththee H3H3 endend ofof ththee spectrumspectrum (illustrated(illustrated iinn FigFig.. 6)6) whichwhich bandband.. FigFig.. 5b5b showsshows that,that, aatt a somewhatsomewhat higherhigher impartsimparts a drabdrab,, unappealingunappealing greegreenn colourcolour;; andand alsoalso rangrangee ofof temperatures,temperatures, exactlexactlyy ththee samesame comple­comple­ becausbecausee ofof internainternall graphitizationgraphitization oftenoften occurrinoccurringg aatt mentarmentaryy effeceffectt isis observedobserved foforr ththee decadecayy ofof ththee micro-inclusions.micro-inclusions. Moreover,Moreover, iitt iiss veryvery difficultdifficult ttoo 595595 runmn banbandd anandd ththee growtgrowthh ooff thethe HibHlb linlinee (the(the prevenpreventt thethe polishepolishedd facetfacetss onon thethe stonestone fromfrom HicHlc linlinee behavebehavess identically)identically).. IInn particulaparticularr wewe becominbecomingg frostedfrosted.. Thus,Thus, althougalthoughh iitt iiss possible,possible, notenote thathatt foforr annealingannealing temperaturestemperatures uupp ttoo withwith carecare,, toto heatheat a treatedtreated diamonddiamond ttoo 1000°C1000°C ttoo 1325°C1325°C iitt iiss notnot possiblpossiblee ttoo producproducee a treatedtreated 'destroy*destroy ththee 595595 nmnm lineline,, itit isis notnot possiblpossiblee toto destroydestroy yelloyelloww oorr brownbrown diamondiamondd thatthat hahass nonott presentpresent ththee HibHlb oorr HlHicc lineslines withouwithoutt ruiningruining ththee diamonddiamond eitheeitherr ththee 595595 nmnm linlinee onon thethe ononee hand,hand, oror,, onon aass a gem.gem. ththee otherother,, ththee HlHibb and/oand/orr HlHicc lines.lines. OuOurr workwork(17)(17) showsshows thathatt ththee ratioratio ofof ththee HIb:HIcHlb:Hlc lineline strengthsstrengths iiss proportionaproportionall ttoo ththee ratioratio ooff ththee Natural fancy diamonds H3:HH3 :H4line4 line strengths.strengths. HoweveHoweverr therethere isis nono relationrelation­­ WWee havehave examineexaminedd a largelarge numbenumberr ofof diamondsdiamonds shipship betweebetweenn ththee intensitieintensitiess ofHIbof Hlb andand H3,H3, nonorr ofof inin whichwhich thethe HH33 banbandd occursoccurs naturallynaturally andand,, aparapartt HicHlc andand H4H4.. TheseThese resultresultss indicatindicatee thatthat HlHibb anandd fromfrom ononee diamondiamondd whicwhichh wewe discusdiscusss laterlater,, wwee find HicHlc centrecentress areare formedformed whenwhen somesome oorr alalll ooff thethe thethe following:following: constituentsconstituents ooff thethe 595595 nmnm centrecentre becomebecome trappedtrapped aa.. TherTheree iiss littllittlee evidencevidencee foforr anan absorptioabsorptionn linlinee aatt 1 atat thethe A-forA-formm oror B-forB-formm ooff nitrogennitrogen,, respectively.respectively. 14501450 cm-cm 1 inin ananyy ofof thethe diamonds;diamonds; ProlongedProlonged heatinheatingg aatt 1400°I400°CC substantiallysubstantially reduces,reduces, bb.. NonNonee ofof ththee diamonddiamondss showedshowed anan H4H4 line,line, oorr eliminates,eUminates, thethe HibHlb andand HlHIec lines.lines. HoweverHowever,, wewe regardlessregardless ofof thethe A ttoo B nitrogenitrogenn ratioratio;; havhavee founfoundd thathatt thisthis drasticdrastic treatmentreatmentt resultresultss inin aann c.c. NonNonee ofof thethe diamondsdiamonds hadhad a 595595 nnmm line;line; unattractivunattractivee appearancappearancee ooff ththee diamond,diamond, partlypartly d.d. NonNonee ofof ththee diamonddiamondss hahadd aann HlHIb b oorr HicHlc lineline.. 8800 J. Gemm., 1986,1986,20,2 20, 2

o 0 n ^ * - • • 100 • • • o0 • • • • • \ /H3

0~ (% ) >- •Y f-- (/) z (a(0)) w y^ \GRI f-- Z 0 INTENSIT Y 100o (b) w0 (/) \595 nm --.J o « ^o \/ ~ cc: ft 0 z NORMALISE D •/ \595 nm

oo V — A04000 606000 808000 10001000 12012000 1400uoo ANNEALINANNEALINGG TEMPERATURTEMPERATUREE (°C(OC))

Fig.Fig. 55.. AnnealingAnnealing curvescurves showingshowing (a(a)) ththee decaydecay ofof ththee GRGRI1 absorptionabsorption andand ththee growtgrowthh ofof ththee H3H3 (503(503 run)nm) absorption,absorption, andand (b)(b) thethe decaydecay ofof ththee 595955 nnmm absorptioabsorptionn anandd ththee growthgrowth ofof ththee HlbHlb lineline.. TheThe diamondsdiamonds werweree heateheatedd foforr ononee houhourr aatt eacheach temperature.temperature.

1 1 AsAs wwee havehave notednoted aboveabove,, ththee 14501450 cmcm-',, H4,H4 , understoodunderstood.. However,However, a clearlclearlyy definedefinedd 14501450 cm-cmI 595595 nm,nm, HlHlbb andand HlHlcc lineliness cacann bbee virtuallyvirtually linlinee wouldwould stronglystrongly suggestsuggest thathatt a diamonddiamond hahadd eliminateeliminatedd iinn a treatedtreated diamon diamondd bbyy heatinheatingg foforr beebeenn artificiallartificiallyy coloured.coloured. aboutabout foufourr hourhourss aatt 1400°C,1400°C, althoughalthough onlonlyy atat thethe ThThee absencabsencee ofof ththee H4H4 lineline doedoess notnot unambig­unambig­ costcost ooff spoilingspoiling ththee diamonddiamond aass a gemgem.. IInn naturenature thethe uouslyuously meameann thathatt a diamonddiamond hahass notnot beenbeen treated.treated. IItt lowerlower temperaturetemperaturess actinactingg forfor millionsmillions ofof yearsyears,, onon isis perfectlyperfectly possiblepossible,, startingstarting witwithh a diamonddiamond whichwhich stonesstones iinn whichwhich vacancievacanciess havhavee beebeenn produceproducedd bbyy doesdoes nonott contaicontainn B-centresB-centres,, toto produceproduce anan artificialartificial naturalnatural processes,processes, alsalsoo resulresultt inin diamondsdiamonds showingshowing colourcolour witwithh nnoo HH44 absorptionabsorption present.present. (See(See Fig.Fig. 3b3b onlyonly ththee HH33 absorptioabsorptionn bandband:: inin thisthis case,case, however,however, forfor example.)example.) HoweverHowever,, aass wwee havhavee notenotedd earlier,earlier, ththee stonestoness willwill notnot havhavee sufferedsuffered ththee deleteriousdeleterious diamonddiamondss selectedselected foforr treatmenttreatment generallgenerallyy havhavee aatt effectseffects whicwhichh wwee havhavee describedescribedd aass beinbeingg a resulresultt ooff leasleastt somesome nitrogenitrogenn presenpresentt iinn thethe B-formB-form,, anandd thethe thethe highehigherr temperaturetemperaturess useusedd inin ththee laboratory.laboratory. H4H4 linlinee willwill thereforthereforee bbee presenpresentt afterafter treatment.treatment. ThThee presencpresencee ooff thisthis lineline woulwouldd agaiagainn stronglystrongly SpectroscopicSpectroscopic assessmenassessmentt ofof diamondsdiamonds suggest that the diamond has been artificially 1 suggest that the diamond has been artificially TheThe presencepresence oror absencabsencee ofof ththee 14501450 cm-cmI coloured.coloured. infrareinfraredd line,line, taketakenn onon ititss own,own, iiss nonott a satisfactorysatisfactory ThThee mosmostt reliablreliablee indicatoindicatorr ooff thethe lacklack ooff indicatoindicatorr ooff thethe origioriginn ooff ththee colourcolour ooff a diamond.diamond. authenticityauthenticity ofof thethe colourcolour ooff a diamonddiamond turnsturns outout toto SomeSome diamonddiamondss whicwhichh havhavee nonott beebeenn irradiatedirradiated bbee thethe 595595 nnmm linlinee useusedd untiuntill 1978,1978 , taken inin have an absorption which may be confused with the conjunction with the Hlb and/or Hlc lines. Fig. 5 have an absorption which may1 be confused with the conjunction with the Hlb and/or Hlc lines. Fig. 5 radiation-induced 1450 cmI line. Furthermore, shows that for an annealing temperature around radiation-induced(15) 1450 cm- line. Furthermore, shows that for an annealing temperature around Woods(15)Woods founfoundd thatthat thisthis linlinee waswas not presenpresentt iinn oneone 700°C700°C,, thethe 595955 nnmm linlinee wouldwould bbee neanearr itsits maximummaximum ooff hihiss treatetreatedd stones,stones, foforr reasonsreasons nonott yetyet fullyfully strength,strength, bubutt ththee HlbHlb and/oand/orr HlcHlc lineslines woulwouldd bbee J.J.Gemm.,1986,20,2 Gemm., 1986, 20, 2 8181

...... I E u

z~ w 10 u- LL LL W 0 U z 5 0 ~ 0.... 0:: 0 if) en « 400 500 600 700 800 WAVELENGTH (nm)

Fig.Fig. 66.. AbsorptionAbsorption spectrum,spectrum, recorderecordedd withwith ththee samplesample aatt liquiliquidd nitrogennitrogen temperaturetemperature,, ooff a treatetreatedd diamonddiamond thathatt hahass beenbeen heateheatedd atat 1400°C1400°C foforr fourfour hourhourss ttoo destroydestroy thethe HlbHlb anandd HlHiec absorptionabsorption lines.lines. NotNotee thethe absorptioabsorptionn atat ththee redred endend ofof ththee spectrumspectrum (wavelength(wavelengthss aboveabove 636300 nm)nm) whicwhichh givegivess ththee diamonddiamond a drabdrab,, unattractivunattractivee appearance.appearance. barelybarely detectabledetectable;; whereawhereass forfor anan annealingannealing tem­tem­ WWee musmustt assumassumee thathatt thethe naturalnatural annealingannealing peraturperaturee greategreaterr thanthan 1000°C1000°C ththee 595595 nnmm linlinee wouldwould receivedreceived byby thithiss diamonddiamond wawass relativelrelativelyy mildmild bbee completelcompletelyy absent,absent, butbut ththee HlHlbb and/oand/orr HlcHlc lineslines comparecomparedd withwith thatthat receivedreceived bbyy alalll ththee othersothers wewe wouldwould bebe relativelyrelatively strong.strong. AAnn intermediateintermediate situationsituation havhavee examineexaminedd (i(inn mucmuchh ththee samesame wayway aass typtypee Iblb iiss observedobserved foforr temperaturestemperatures betweebetweenn 700700 andand diamondsdiamonds havhavee experiencedexperienced a mildemilderr degredegreee ooff 1000°C.1000°C. heatingheating andand nitrogenitrogenn aggregatioaggregationn thanthan thethe vastvast majoritmajorityy ofof typtypee lIaa diamonds).diamonds). DiamondDiamondss likelike An exception Anderson'sAnderson's araree howeverhowever extremelextremelyy rarerare andand wwee A diamonddiamond ownedowned bbyy thethe latelate BasiBasill AndersoAndersonn hashas believbelievee ouourr methomethodd ofof assessingassessing ththee origioriginn ofof thethe beebeenn referrereferredd toto previouslpreviouslyy iinn thisthis journaljournal(14).(14). colourcolour ooff diamondsdiamonds wilwilll bbee correctcorrect inin 99%99% ooff casescases BecauseBecause iitt wawass purchasedpurchased beforbeforee 19501950 AndersonAnderson examined.examined. NNoo treatedtreated diamondsdiamonds shouldshould bebe mistakenmistaken wawass certaincertain thathatt ththee colourcolour wawass naturalnamral.. However,However, asas naturallynaturally colouredcoloured,, bubutt iitt iiss possiblpossiblee thatthat veryvery thethe diamonddiamond hahass bothboth H3H3 andand H4H4 absorptionabsorption bandsbands occasionalloccasionallyy a naturallnaturallyy colourecolouredd diamondiamondd maymay bebe witwithh thethe H3:H4H3:H4 ratiratioo proportionalproportional toto thethe A:BA:B classifiedclassified aass treated.treated. nitrogennitrogen ratio,ratio, andand a well-definewell-definedd 595955 nmnm line.line. InIn ourour presentpresent measurementsmeasurements wwee havehave shownshown that,that, forfor ConclusionsConclusions thithiss stone,stone, ththee HlbHlb anandd HlHIec lineslines araree veryvery weak.weak LatestLatest developmentsdevelopments inin researcresearchh oonn artificiallyartificially indeedindeed,, anandd thethe spectraspectra are,are, atat facfacee value,value, allall colouredcoloured yelloyelloww anandd browbrownn diamonddiamondss havhavee beenbeen characteristiccharacteristic ooff a treatedtreated diamonddiamond thatthat hahass beenbeen described.described. WWee havhavee shownshown thatthat itit isis nonott possiblepossible toto annealeannealedd aatt abouaboutt 750°C750°C.. colourcolour a diamonddiamond artificiallyartificially usingusing radiationradiation damagedamage 82 J. Gemm., 1986, 20, 2

and heat treatment, without producing at least one References of the absorption lines at 595 nm, 1936 nm (Hlc) 1. Dugdale, R.A. 1953. Brit. J. Appl. Phys., 4, 334-7. or 2024 nm (Hlb). When all three are absent the 2. Clark, C.D., Ditchburn, R.W. and Dyer, H.B. 1956. Proc. diamond may safely be categorized as 'naturally R. Soc., A234, 363-81. 3. Clark, C.D., Ditchburn, R.W. and Dyer, H.B. 1956. Proc. coloured'. It is desirable to measure the spectra in R. Soc., A237, 75-89. the visible region with the sample cooled with liquid 4. Anderson, B.W. 1943. Gemmologist, XII, 138, 21-2. nitrogen. The Hlb and Hlc lines, however, are 5. Scarratt, K. 1979. J. Gemm., XVI, 7, 433-47. reasonably sharp at room temperature, and in many 6. Woods, G.S. and Welbourn, C.M. 1980. The assessment of colour in diamonds and other gems. UK Patent Application GB cases cooling will not be necessary to record the near 2036360 A. infrared spectrum. 7. Billmeyer, F.W. and Saltzman, M. 1966. Principles of color Very occasionally one or more of the above lines technology. New York: Interscience. may be present in a naturally coloured stone. In any 8. Graham, C.H. 1965. Vision and visual perception. New York: John Wiley and Sons. diamond in which the 595 nm band is absent, but 9. Wyszecki, G. and Stiles, W.S. 1967. Color science. New York: the Hlb and Hlc lines are present, the strengths of John Wiley and Sons. the latter should therefore be compared with those 10. Anderson, B.W. 1963. J. Gemm., IX, 2, 1-11. of a known treated diamond which has an H3 band 11. Crowningshield, G.R. 1958. Gems Gemol., 9, 99-104. 12. Collins, A.T. 1978. Nature, 273, 654-5. of similar intensity to that of the stone being 13. Anderson, B.W. 1980. Gem Testing, London: Butterworths. investigated. If the Hlb and Hlc lines are very 14. Collins, A.T. 1982. J. Gemm., XVIII, 1, 37-75. weak compared with the standard stone, then the 15. Woods. G.S. 1984. Phil. Mag., B50, 673-88. colour of the diamond under test is probably of 16. Collins, A.T. 1980. J. Gemm., XVII, 4, 213-22. 17. Collins A.T. Davies, G. and Woods, G.S. 1986. J. Phys. C. natural origin. This conclusion could be firmer if (to be published). the H4 line is absent or very weak. Even after completing a detailed series of tests [Manuscript received 21 November 1985.] there may be very rare occasions when a naturally coloured diamond is wrongly classified, but it should not in future be possible fraudulently to obtain a 'naturally coloured' certification for a treated diamond that has been heated at 1000°C to destroy the 595 nm line. J. Gemm., 1986, 20,2 83

Green aventurine quartz: mineralogical characterization

E.A. Monroe, Ph.D.

New York State College of Ceramics, Alfred University, Alfred, N.Y. 14802-1296, USA

Introduction of a green chromium-bearing muscovite mica, Quartzite, a metamorphic rock conslstmg of fuchsite(1 ). It is commonly used for beads or set in interlocking grains of quartz, may contain small rings, brooches and other articles of jewellery as crystals of mica or other minerals. When these well as being used in making bowls, vases and other accessory minerals impart an appealing colour, ornamental objects. Most of the green aventurine sheen or glitter to the quartzite, then it is known comes from India; hence the misnomer, Indian as aventurine quartz. Green aventurine quartz is jade. Some localities where it occurs are Be1vadi in one variety reportedly containing platey crystals the Hassan district of Mysore and the Coimbatore,

Fig. 1. Transmission light micrograph of a thin-section of green aventurine showing the various mineral components. lao Normal light. lb. Crossed-polarized light. lc. Normal light. f=fuchsite, g=garnet, r=rutile. Id. Normal light.

© Copyright the Gemmological Association ISSN: 0022-1252 84 J. Gemm., 1986, 20, 2

Bellary and Nellore districts of Madras. Other bundles in some areas. Small dark red crystals of sources are Siberia, Tanzania, China, and Rutland garnet, less than 0.1 mm, occur with less frequency. County, Vermont, USA.(U) At the higher magnification of Fig. lc some of these Previous studies on the mineral description of minerals are marked with identifying labels. The green aventurine were not found to be reported in subparallel texture of the rutile fibres and fibre the literature. However, Webster(1) states that this bundles as well as the platey fuchsite mica crystals material gives a chromium-type optical absorption imparts a schistosity to this metamorphic rock spectrum, but with the lines in the red rather vague which is readily observed in Fig. Id. and the broad absorption in the yellow-green region not pronounced. Electron microscopy Green aventurine from the Bellary district, India, Transmission and scanning electron microscopes was studied in order to determine the mineral were used to examine fracture surfaces of the constituents present and their microstructural aventurine. These instruments revealed the granular arrangement. These analyses were conducted by texture of the quartz along with the accessory means of petrographic microscopy, scanning and crystals of mica. The rutile and garnet crystals were transmission electron microscopy, X-ray diffrac­ not identified by these methods. tion and electron microprobe spectroscopy. Fig. 2a shows the granular texture of the quartz on a fracture surface of the aventurine observed by Petrographic microscopy scanning microscopy. A fracture crevice travelling Thin sections showed the aventurine to be com­ through the quartz contains fuchsite mica. posed of a complex array of four crystalline minerals. Transmission electron microscopy using the Interlocking, irregularly-shaped grains of quartz, replication method also revealed the granular Si02, formed the bulk of the specimen. Associated nature of the specimen. Fig. 2b shows one region at with the quartz were three accessory minerals, high magnification where a small crystal of fuchsite fuchsite mica, K(A1, Cr)2(AlSi3Oio)(OH)2; rutile, mica is located at the grain boundaries of three Ti02; and almandine garnet, Fe3Al2(Si04)3. relatively large grains of quartz. The mica crystal Figs, la and lb show this microstructure using displays a parallel step-like topography reflecting normal light transmission and the same field using the perfect cleavage inherent in this mineral. cross-polarized light. The relatively large polyhedral quartz grains can be seen best in Fig. lb where X-ray diffraction some of these grains up to about 1.0 mm in size are The powder X-ray diffraction pattern of aven­ at partial or complete extinction (black). The turine obtained using a diffractometer showed smaller 0.1-0.2 mm transparent green euhedral peaks assignable to quartz and mica. Although crystals of fuchsite are in abundance as are the grey almandine garnet and rutile were indicated by hair-like fibres of rutile which are aggregated into light microscopy, their volume percentage in the

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Fig. 2a. Scanning electron micrograph of the surface of green Fig. 2b. Transmission electron micrograph of the surface of aventurine. Etched with NaOH. The grains of quartz are green aventurine. Replication. Crystals of quartz and clearly discernible. Fuchsite (labelled f) occurs in a fuchsite mica are present in this field. q=quartz; fracture crevice. f= fuchsite. J. Gemm., 1986, 20, 2 85

C9 1 M AUENTURINE. GR. ^ .* Ui

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Fig. 3. X-ray diffraction pattern of green aventurine. CuKOf radiation. Diffraction maximas identified by q=quartz and f—fuchsite mica.

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Fig. 4. X-ray spectrum emitted from green aventurine during electron microprobe analysis. Elements corresponding to the X-ray peaks are given by chemical symbols. 86 J. Gemm., 1986, 20, 2

aventurine was too low to be detected by X-ray almandine garnet, Fe3Al2(Si04)3, and in fuchsite diffraction. These X-ray results are presented in mica, K(A1, Cr)2 (AlSi301o)(OH)2. Silicon occurs Fig. 3. in quartz, Si02, as well as in the garnet and mica. Potassium is found in the mica, titanium occurs in Electron microprobe spectroscopy rutile, Ti02, chromium occurs in the mica and iron Chemical analysis of the elements present in the occurs in the garnet. aventurine was carried out by identifying the X-rays emitted from the sample when bombarded Acknowledgement by an electron beam. The US National Museum, Division of Miner­ Fig. 4 shows the X-ray spectrum which was alogy, supplied the mineral specimens used in obtained. The various X-ray peaks are identified as this study. to their corresponding chemical element. With the exception of the elements of gold (Au) and References palladium (Pd), which were derived from the 1. Webster, R. 1975. Gems, 3rd edn. Butterworths, London. 187. electron-conductive metal coating that was applied 2. Frondel, C. 1962. Dana's system of mineralogy, Vol. 3, Silica to the aventurine surface, all the elements detected minerals. John Wiley, New York. corresponded to the various mineral species present. [Manuscript received 29 August 1985.] Taking the elements in the order they appear on the graph in Fig. 4, aluminium (Al) occurs in JJ.. Gemm.Gemm.,, 19861986,20,2, 20, 2 8877

LocatinLocatingg gegemm depositdepositss bbyy computercomputer

Michael O'Donoghue,0'Donoghue, M.A., F.F.G.A. G.A.

CuratorCurator,, EartEarthh SciencesSciences,, ThThee BritisBritishh LibraryLibrary,, LondonLondon,, WC2WC2BB 4A4ATT

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SourcesSources ofof informationinformation ThThee readershipreadership ofof suchsuch anan institutioninstitution asas thethe MapsMaps ScienceScience ReferencReferencee LibraryLibrary (part(part ofof ththee BritishBritish FurtherFurther usefuluseful informationinformation cacann bbee founfoundd inin LibraryLibrary)) hahass changechangedd sincesince ititss physicalphysical separationseparation geologicageologicall mapmapss anandd inin ththee mapsmaps produceproducedd forfor a fromfrom ththee BritisBritishh MuseuMuseumm inin ththee earlyearly 1970's.1970's. limitelimitedd andand specificspecific purposepurpose.. AgainAgain,, accessaccess toto mapsmaps ReadersReaders eveneven inin thosethose daysdays wouldwould havehave beebeenn contentcontent isis a specializedspecialized skillskill andand findingfinding outout whowho actuallyactually toto checkcheck gemmologicalgemmological pointspoints inin thethe standardstandard text­text­ holdsholds a particularparticular mapmap isis notnot alwaysalways easy.easy. MajorMajor bookbookss ofof thethe timetime andand thoughthough therethere werewere inin factfact librarieslibraries holdhold standardstandard surveys,surveys, includingincluding geologicalgeological manymany otherother sourcessources toto whichwhich theythey couldcould turnturn eveneven ones,ones, butbut manymany gemgem locationslocations areare notnot shown,shown, eithereither then,then, fewfew werewere awareaware thatthat muchmuch usefuluseful datadata couldcould becausebecause theythey areare tootoo insignificantinsignificant asas placesplaces oror thethe bbee foundfound inin physicalphysical andand chemicalchemical textstexts anandd journalsjournals namename usedused byby minersminers iiss tootoo locallocal toto getget furtherfurther thanthan asas wellwell asas inin mineralogicalmineralogical andand geologicalgeological ones.ones. thethe immediateimmediate area.area. ManyMany gemgem locationslocations areare knownknown ThereThere seemsseems toto havehave beenbeen anan unwillingnessunwillingness onon thethe byby moremore thanthan oneone namename andand whenwhen a namename isis usedused itit partpart ofof writerswriters onon gemmologicalgemmological topicstopics toto referrefer toto maymay referrefer toto thethe nearestnearest placeplace ofof significancesignificance whichwhich outsideoutside sources,sources, soso thatthat untiluntil veryvery recentlyrecently eveneven maymay bebe somesome milesmiles awayaway fromfrom thethe actualactual minemine (e.g.(e.g. thethe betterbetter monographsmonographs providedprovided inadequateinadequate bibli­bibli­ Sandawana).Sandawana). WhereWhere a namename isis usedused onon a mapmap andand ographiesographies withwith fewfew citationscitations ofof piecespieces otherother thanthan thethe depositdeposit isis describeddescribed inin thethe literatureliterature itit oughtought toto thosethose whichwhich mostmost readersreaders wouldwould alreadyalready havehave bebe possiblepossible toto locatelocate bothboth eveneven whenwhen thethe twotwo namesnames knownknown about.about. EvenEven todaytoday almostalmost allall thethe gemmo­gemmo­ usedused areare different.different. HowHow thisthis cancan bebe donedone willwill bebe logicallogical textstexts areare foundfound wantingwanting inin thisthis area.area. ThisThis seenseen later.later. maymay partlypartly bebe duedue toto thethe readershipreadership aimedaimed at,at, sincesince InIn thethe absenceabsence ofof definitedefinite detaildetail aboutabout existingexisting ifif a bookbook cancan bebe addressedaddressed toto thethe beginnerbeginner,, timetime andand gemgem locations,locations, possiblepossible onesones cancan alsoalso bebe predictedpredicted ifif scholarshipscholarship dodo notnot needneed toto bebe spentspent onon extensiveextensive thethe rightright mapmap isis toto hand.hand. ThisThis willwill inin allall casescases bebe a literatureliterature searching.searching. AnotherAnother explanationexplanation maymay bebe geologicalgeological mapmap sincesince thesethese areare thethe onlyonly onesones uponupon thatthat manymany writerswriters areare themselvesthemselves unfamiliarunfamiliar withwith whichwhich elementselements areare shown.shown. IfIf berylliumberyllium isis seenseen onon a

© CopyrightCopyright thethe GemmologicalGemmological AssociationAssociation ISSN:ISSN: 0022-12520022-1252 88 J.Gemm.,1986,20,2

map (usually as Be) then the possibility of the material loaded into the system may be in different presence of one of the beryl gemstones is there. languages: if we expect a paper in German about The overall picture then is one of a mass of emerald to include the word EMERALD rather information, much of it fairly easily predictable than SMARAGD we may lose that paper. One way and obtainable but with an underlying mass of data to bear this in mind is to reflect on the history of the which is at once both valuable and unsuspected. country in which we are interested: former French The value of this type of information is that it is colonies will be more likely to have papers written usually more specific and first-hand, being taken about them in French (EMERAUD). Again, the from workers in the field. computer is literal and if you ask it for references As anyone who has used Chemical Abstracts will including the word RUBY it will ignore RUBIES. know to their cost, the fear that something The two main databases are loaded (stored) with important may be overlooked through inadequate material in the form of abstracts so that the searching technique can be considerable and it is searcher's hits will include not only the title of now unreasonable to expect anyone to search an relevant papers but abstracts of them. The most increasingly large footage of small-type paperwork. economic way to check whether or not a paper will To be sure of finding all there is on a particular topic be worth printing out is to get the system to type the at least a dozen journals need to be consulted and title or the paper in precis form; only after this need although Mineralogical Abstracts covers the earth the searcher opt for the full abstract (which is more science side well, many searchers for details of gem expensive). It is hoped that Mineralogical Abstracts deposits may need to look in mining or economic will be loaded on to GEOARCHIVE during 1986. sources or even in general science journals such as It is relatively easy to locate a paper on a Nature. particular gemstone; the name of the species can be Clearly some form of mechanized retrieval keyed in accompanied by country name where system is as necessary in the location of gem deposit known or by the name of the author (be careful with information as it is in subjects with a wider spelling) in addition: background. RUBY AND MOGOK AND IYER will give any paper whose keywords include the Databases three (not any other paper and not any which Fortunately today we have at least two databases contain only two or one keywords out of the three). concerning themselves with geology, mineralogy For less certain searches it would be preferable to and allied topics. The databases GEOREF and key GEOARCHIVE (American and British-based RUBY OR MOGOK respectively) can be accessed through the Lockheed so that the system would look for papers with either DIALOG host which itself is easily obtainable by keyword. Should the searcher already know about subscribers to British networks with access to PSS the Iyer paper and therefore not want to spend (Packet Stream Switching). The technique of money on it he would key searching is not hard to master, but the real skill RUBY OR MOGOK AND NOT IYER comes in avoiding unnecessary expense, since a lot The use of AND, OR and AND NOT is known of time can be spent pondering the next move while as Boolean logic and is familiar to all computer the system is actually live. There are ways of getting users: without this conditioning searches would be round this, as will be seen below. For greater ease of hugely unwieldy, producing vast amounts of understanding, search qualifiers are not included in repetitive information. the descriptions below. Intending searchers will If we wish to range in our search for ruby a little need to learn the qualifiers appropriate to the more widely we can key database host they select. RUB? - this device is known as a truncation and will give Searching hits for ruby, rubis (French) and rubies. A similar Searching for a topic means that the computer strategy for diamond might be will look for given words, phrases, map coordinates DIAMON? or the names of authors and present them to the user but this would lead to an oversize response, since in the form of "hits". A large number of hits is not the terms diamond, diamondiferous and even necessarily helpful since the word GEOLOGY will Diamonair would be retrieved. In the latter case the appear so often in a geological database that to ask use of AND NOT is indicated. In the same way for it is a waste of time. We need to know how to PERIDOT? would give both the gem of that name avoid this waste by giving the system more specific and peridotite. words and combinations so that it will be able to For more general concepts we need to be able to narrow the search, remembering also that the use the term that a system prefers. What these J. Gemm., 1986, 20, 2 89 terms are can be found in a dictionary-like work material can be found by searching on produced by the originators of the database and Lat. 15° to 25° 8' S and Long. 22° to 28° E known as a thesaurus. Here we can find whether the and adding the term MANGAN? (for both English database recognizes the term 'synthetic' in the sense and German spellings of manganese). The deposit is that gemmologists give to it or whether 'man-made' the Kalahari manganese orefield from which is preferred. All thesauri are large because they magnificent orange-pink rhodochrosite has been contain so many cross-references and in addition recovered. As the ore is likely to be of more some may carry numerical codes for geographical importance than the gem material it may be areas as well as for some general concepts. worthwhile using a metals database rather than a Many papers are written for the more popular geological one. Since this deposit was located partly journals and in such cases may have rather fanciful at least by the use of remote sensing using the titles. The searcher will not be able to guess that a LAND SAT satellites, a look at the 16 mm browse paper on peridot has the title Green gems from the film produced from their orbits will show useful Red Sea but RED SEA is acceptable as a phrase, as areas with coordinates worth inputting. is MAFIC ROCKS. Keying in RED SEA OR For those interested in getting the most up-to- MAFIC ROCKS OR GEM? would give us the date information on a prospect the date of publi­ Gubelin paper on Zabargad, the spelling of which is cation of particular papers can be significant, and romanized in different ways, this making it an when the subject is a popular one a cut-off date can uncertain search term on its own. eliminate large quantities of paper. In most databases this is done by keying in PY= 1960-1980, Searching coordinates for example, so that any paper with a publication There is no detailed map of world gemstone date not falling in that range is not brought up. deposits apart from that produced in the 1960s by Likely prospects for gemstones can be checked the French Bureau de Recherches Geologiques et by inputting the names of features which have been Minieres. This uses an equiareal projection and a found to be common accessories to known deposits scale of 1:40000000. This does not allow for much of the desired species. For a deposit similar to that distinction between rock types, and in fact eight in the Pala area of southern California we could different types of gem deposit are distinguished: try coordinates plus GRAPHIC GRANITE OR deposits enclosed in volcanic rocks and their SCHORL OR MUSCOVITE to see if these have vents been reported as occurring together (it would be decay deposits of volcanic rocks surprising if they did not). We could add lithium as pegmatite deposits a concept by typing Li? or the full word. lode deposits metamorphic deposits Chemical data endomorphic deposits Chemical formulae can in fact be entered in decomposition deposits addition to the terms already mentioned, providing other types. that they are mentioned in the papers abstracted. A careful study of the deposits as shown on the Normally chemical searches would take place in map will show where they fit into the map Chemical Abstracts (which contains a good deal of coordinates (latitude and longitude). The two main geological information), but this is a very large databases will accept map coordinates as search database which needs skilful handling. We know terms and these can be combined with country that there are 2331890 possible quaternary com­ names, deposit type names as listed above (consult pounds (i.e. having four elements) and 109736 the thesaurus to see if these are acceptable phrases ternary ones. As the total number of known mineral for your database) and species names: species is only about 3000 some kind of selection is Lat. 22° 50' 45" N to 23° 5' 15" N and Long. 96° clearly operating and possible compounds can 19' to 96° 35' E would give us the Mogok Stone easily be found by using the computer. A paper Tract in Burma: they should be combined with describing calcium and oxygen will not normally GEM? or RUB? or SAPH? or CORUND? or mention that no CaO forms naturally on earth since KORUND Ca and O combine more efficiently with C02 to to give one search. Results of this (the number of form CaC03 but once such sources as Chemical hits) could be combined with shifts in the coordin­ Index to Minerals, Glossary of Mineral Species and ates to see if further corundum gems were reported lists of new and discredited minerals are loaded into from neighbouring areas. On the whole these areas a database it will be possible to search on various are well reported and stones from them have been elements and their compounds to see which the subject of papers for many years. A deposit of combine. significance for strategic elements as well as for gem In a similar way optical and physical constants 9090 J. Gemm., 1986,20,2

willwill bbee ablablee toto bbee searchedsearched inin conjunctioconjunctionn withwith speciesspecies namesnames,, placplacee namenamess andand chemicalchemical termsterms toto seesee whethewhetherr thertheree cancan bbee a reredd tourmalintourmalinee withwith abnormallyabnormally highighh refractiverefractive index;index; whethewhetherr therethere cacann bbee gegemm materialsmaterials whichwhich includincludee boroboronn andand whetherwhether thisthis iiss linkelinkedd witwithh ananyy particularparticular typtypee ooff rocrockk formation.formation. lI shouldshould likelike toto encourageencourage gemmologistsgemmologists toto visitvisit ththee ScienceScience ReferencReferencee LibraryLibrary ttoo seesee whawhatt wwee cancan alreadyalready provideprovide andand toto conceiveconceive whatwhat maymay bebe possiblpossiblee inin futurefuture.. AnyoneAnyone whowho hahass regularlyregularly scouredscoured thethe tintinyy prinprintt ofof thethe hard-copyhard-copy Chemical Abstracts oorr Index Medicus wilwilll knoknoww hohoww muchmuch easiereasier iitt iiss toto ususee ththee computercomputer,, anandd iitt doesdoes provideprovide opportunitieopportunitiess foforr bringingbringing togethertogether conceptconceptss whichwhich nnoo hard-covehard-coverr worworkk coulcouldd afforaffordd ttoo do.do.

[[ManuscriptManuscript receivedreceived 18 18 September September 1985.] 1985 .] J. Gemm., 1986, 20, 2 91

A description of the jasper found at the Orinduik Falls in Guyana, South America (Cover photograph)

J.G. Gosling, F.G.A.

Pattingham, Staffordshire, WV6 7BU

In the north-east of South America between This consists of a great thickness of current- Venezuela and Surinam and to the north of Brazil bedded, pink and red ferruginous sandstones and lies Guyana. The name comes from an Amerindian arkroses together with shales and conglomerates. word which means 'Land of Waters', and this is an Mount Roraima is not too far from Orinduik and apt description since great rivers dominate the rising sheer out of the jungle gave Sir Arthur Conan country. Doyle the geological basis for his popular classic One of these is the river Ireng which is the natural The Lost World'. boundary between Guyana and Brazil. On this river lies the tiny community of Orinduik with its air strip, two stores and Amerindian settlement where guides and helpers may be hired. On these settlements live Wapisianas and Macusi Indians, who are a sturdy, small built people with a tremendous capacity for hard work and fun. From the early days of geological exploration it has been recorded that certain areas of Guyana had a wide range of ornamental stones. Among these was a very handsome red jasper that was found in large quantities around Orinduik in the Pakaraima Mountains. In the early 1970s both the quantity and quality found encouraged the Ministry of Energy and Natural Resources to set up a new industry based on the utilization of these materials. This project was assisted by British Technical Aid arranged by the Ministry of Overseas Development and the author was privileged to carry out the scheme for the people and Government of Guyana. To reach Orinduik from Georgetown could take about two weeks by river and land since much of the journey would be through miles of the most beautiful jungle scenery, which is still largely unexplored. Normal access with Georgetown is by Guyana Airways, which takes only a few hours, and once there overland communications are good. The area is the habitat of a small fly called locally Kaboura, which produces a maddeningly itchy bite - fortunately it yields to insect repellents. Orinduik lies in the south-western part of the Pakaraima Mountains, which are underlain by the Fig. 1. Falls at Orinduik showing red jasper and blocky sand­ geological unit known as the Roraima Formation. stone outcrop. Photograph by J.G. Gosling.

© Copyright the Gemmological Association ISSN: 0022-1252 92 J. Gemm., 1986, 20, 2

At first sight from Orinduik the Falls appear as a insects in the area, but the fireflies, or candleflies as series of vast steps at the head of the valley, but from they are called locally, leave a lasting impression the air one is aware of three major falls and about a because of the brilliance of their blue-green light dozen minor drops. The overall effect is one of emission at night. breath-taking beauty, since all the rock faces of the Farther away from the Ireng river and out on the falls are formed of dusky red quartzitic sandstone savannas another interesting jasper formation is to and interbedded jaspers. These quartzitic sand­ be found. Here strange forms are created by wind stones are fine to very fine grained and often break erosion. In this type of erosion sand is whipped up with conchoidal fractures but are fairly easily by the wind and cutting its way into the jasper distinguished from the true micro- to crypto- produces weird shapes and strange angular castles crystalline jasper used as an ornamental stone. of all sizes. Large boulders are also found rolled along in the In other areas of the Roraima Formation many

Fig. 2. Searching for red jasper pebbles by a brownish-red sandstone outcrop, Orinduik Falls. Photograph byJ.G. Gosling.

Ireng river and were particularly fine above the last varieties of jasper have been found including grey, major fall, and it was discovered that the best jasper purple, brown, green, spotted and banded forms. for tumbling or cutting was found just below the After these materials had been collected and last major fall. (Photograph on front cover.) sorted, they were transported back to the small This seemingly idyllic spot can hide a few industrial unit in Georgetown and fashioned into dangers, as just above the Falls are beautiful clockfaces, paperweights, jewellery units and a host sheltered pools but one must be aware of the deep of other objects for sale locally and for export. holes there, since these may host a very powerful This project continues to flourish and has been electric eel, which has a sting sufficiently powerful expanded to other areas in the interior. to stun a man and allow him to drift over the edge of the Falls. There are many interesting animals, birds and [Manuscript received 16 February 1986.] J. Gemm., 1986, 20, 2 93

Notes from the Laboratory - 6

K. Scarratt

The Gem Testing Laboratory of Great Britain, 27 Greville Street, London, EC1N 8SU

On occasions, because of his cunning and been made up from several parts of old rings and artistry, the perpetrator of an attempt at gemmo- one section included part of a hallmark with a date logical skulduggery might be thought of as a person letter similar to that used for the period 1916-17 deserving a little of our admiration. This should be (Fig. 3) - many years before the production of far from the case. Any intended dishonesty must be synthetic opal! looked upon in the light of the knowledge that the

Fig. 1. A synthetic opal in a ring made up from several parts of old Fig. 2. A synthetic opal in a ring made up from several parts of old rings. rings (side view). person involved is attempting to sully the reputation of the gemmologist and others who handle jewellery. An example of this cunning and artistry was seen when we were asked to examine the marquise- shaped opal set in the ring seen in Figs 1 and 2. The stone was clearly a synthetic showing the typical 'lizard skin' structure and columns of colour. In fact there cannot be a gemmologist who would have been in any doubt as to its identity. On this occasion the attempted deceit was, we believe, aimed at the 'antique' dealer/collector who perhaps has only a limited knowledge of gemstones, rather than the pure gemmologist who might not have Fig. 3. The hallmark in the shank of the ring seen in Figs 1 much knowledge of old jewellery. The ring had and 2.

© Copyright the Gemmological Association ISSN: 0022-1252 94 J. Gemm.,1986, 20, 2

Fig. 4. Natural opal 11.49x8.31x2.11 mm (see Figs 5, 6 and 8 for structure).

Fig. 5. 'Chicken wire' type structures in the natural opal seen in Fig. 6. A closer view of the 'chicken wire' type structures seen in Fig. 4. Fig. 5 in a natural opal.

Fig. 7. 'Chicken wire' structures in Gilson synthetic opal. Fig. 8. Dark matrix veins in the natural opal in Fig. 4 giving an appearance similar to an opal that has been sugar-acid treated. J. Gemm., 1986, 20, 2 95

Some years ago when the first papers were published detailing the diagnostic structures of synthetic opal(1'2), an eminent British gemmologist stated that he had seen similar structures in natural opals. In the intervening period we have noted a number of peculiar structures in natural opals. Many of these have resembled the structures seen in sugar-acid treated opals but have revealed them­ selves to be, for example, oolitic opal. We have never seen a natural opal in which the structures are identical to those seen in the Gilson material. Amongst those which we have examined the closest we have come to a synthetic-like structure in a natural opal was seen towards the end of 1985. The structure was seen in the 1.50 ct stone depicted Fig. 10. Radiograph of a large hollow pearl in which the void appears to have been filled with a resin-like substance. in Fig. 4. The stone measured 11.49x8.31x2.11 mm and was backed by its matrix. The matrix travelled The second example weighed 28.58 ct and as through the opal in veins and these were arranged in can be seen in Fig. 10 it also had a large internal a pattern (Figs. 5 and 6) which was similar in some cavity. The pearl had been drilled in one place and ways to the 'chicken wire' structure seen in this time the cavity had been filled with a soft transmitted light in some synthetic opals (Fig. 7). substance similar in appearance to a dry resin. The In reflected light (Fig. 8) the dark colour of the substance was heated with a hot point and the odour matrix in the veins gives the impression that the produced was similar to a burning plastic when stone has been sugar-acid treated, which it has not. smelt in close proximity, but at a greater distance • • • the smell was similar to frying bacon.

In 1984(3) details of a large hollow baroque pearl • • • were reported upon in which the cavity had been If one looks back through the gemmological 'filled' with a number of beads. The beads had 'an journals of recent years it will be realized that quite opacity to X-rays comparable with that of the a number of manufacturers are either producing or setting'. have the capability of producing synthetic rubies. Two further examples of large hollow pearls with Mostly if these manufacturers market their stones their cavities filled with artificial materials have they do so openly and make various announcements been examined recently. The first pearl measured about them. It is quite unusual to have placed approximately 18x15 mm and, as can be seen in before you a number of obviously synthetic ruby Fig. 9, had a very large internal cavity. The pearl crystals, the manufacturer of which nobody seems had been drilled in one place and through the drill to know. hole the cavity had been filled with what appears on This happened recently when we were shown the the radiograph to be wire. Upon looking into the crystals depicted in Figs 11 and 12. The crystals in drill hole some form of adhesive substance could Fig. 11 had a lot of included orange flux and those also be seen in the cavity. in Fig. 12 had platinum wire protruding from them.

• • * An interesting and effective amber 'treatment' was brought to our attention during the latter part of 1985. A dealer who purchased an 'amber' drop with a view to repolishing it was surprised to find that the colour of the material was located in the surface area only and that beneath the surface it was colourless (Fig. 13). The colour penetrates the colourless material along flaws (Fig. 14) and these when viewed side on (Fig. 15) bore a close resemblance to the stress figures seen in much clarifiethamber(4). Fig. 9. Radiograph of a large hollow pearl in which the void The material has an SG of 1.04 and an approxi­ appears to have been filled with wire. mate RI of 1.55-1.56. There are numerous included 96 J.Gemm.,1986,20,2

Fig. 11. A group of synthetic ruby crystals with included orange Fig. 12. Two synthetic ruby crystals with platinum wire pro- flux, truding.

Fig. 13. Amber in which part of the surface yellow colour has Fig. 14. Amber in which the surface coloration (see Figs 13 and been polished away revealing the colourless material 15) also penetrates the colourless underlying material beneath. along flaws.

Fig. 15. A flaw in the amber of Figs 13 and 14 which resembles Fig. 16. A 4 mm broken natural pearl, the stress figures seen in much clarified amber. JJ.. Gemm.Gemm.,, 19861986,20,2, 20, 2 9977

bubblesbubbles,, ththee greategreaterr numbenumberr ooff whic whichh araree jusjustt undeunderr ReferenceReferencess ththee surfacsurfacee (se(seee FigFigss 1133 anandd 15)15).. ThThee coloucolourr iiss nonott aa 1I.. LiddicoatLiddicoat,, R.TR.T.. 19741974.. DevelopmentDevelopmentss anandd HighlightHighlightss aatt discretdiscretee coatincoatingg oonn ththee surfacesurface,, sucsuchh aass a painpaintt oorr aa GIA'GINss LaLabb iinn LoLoss AngelesAngeles,, Gems Gemol. XIVXIV,, 1010,, 309-310309--310.. varnishvarnish,, bubutt appearappearss ttoo havhavee beebeenn diffusediffusedd intintoo ththee 22.. JobbinsJobbins,, E.A.E.A.,, StathamStatham,, P.MP.M.. anandd ScarrattScarratt,, KK.. 19761976.. InternaInternall structurestructuress anandd identificatioidentificationn ooff GilsoGilsonn synthetisyntheticc opalsopals.. J.J. surfacsurfacee ooff ththee materiamateriall bbyy gentlgentlee heatingheating.. TheThe Gemm., XVXV,, 22,, 66-7566-75.. colourlescolourlesss areareaa iinn FigFig.. 1133 fluorescefluorescess a brighbrightt lighlightt 33.. ScarrattScarratt,, KK.. 19841984.. NoteNotess frofromm ththee Laboratory,Laboratory ,J.J. Gemm., XIXXIX,, blubluee undeunderr ultravioleultraviolett lighlightt whilswhilstt ththee yelloyelloww areareaa 22,, 113113.. fluorescefluorescess a mustard-yellow/greenmustard-yellow/green.. ThThee materiamateriall iiss 44.. WebsterWebster,, RR.. (Revise(Revisedd bbvy AndersonAnderson,, B.W.B.W.)) 19831983.. Gems, theirtheir sources, descriptionsdescriptions and and identification, identification, 4th 4t hedn, edn ,p. p .575. 575 Butter­. Butter- ververyy softsoft,, sesectile,c tile, andand whewhenn heateheatedd witwithh a hohott pointpoint worthsworths,, London.London. produceproducess a smelsmelll similasimilarr ttoo thathatt produceproducedd bbyy amber.amber. AdditionaAdditionall piecepiecess ooff thithiss materiamateriall araree nonoww beinbeingg [[ManuscriptManuscript received 14 January 1986.]1986.] examineexaminedd anandd mormoree detaildetailss wilwilll bbee publishepublishedd iinn a futurfuturee number.number. •* •* *• ThThee 4 mromm brokebrokenn pearpearll iinn FigFig.. 1166 was strunstrungg iinn a necklacnecklacee ooff naturanaturall pearlspearls.. TheThe ownerowner ooff thethe necklacnecklacee assumeassumedd thathatt ththee apparenapparentt 'bead'bead'' revealerevealedd bbyy ththee breabreakk indicateindicatedd thathatt iitt was a cultureculturedd pearl.pearl. IInn facfactt radiographradiographss ooff ththee pearpearll proveprovedd iitt ttoo bebe naturalnatural.. 98 J. Gemm., 1986,20,2

An unusual needle-like inclusion in gem sinhalite from Elahera, Sri Lanka

Mahinda Gunawardene, F.G.A., D.Gem.G. and Marion Gunawardene, D.Gem.G.

Gem Testing Laboratory, 1m Sierling 2, 6581 Hettenrodt, West Germany

Elahera, the north-east gem field of Sri Lanka is portions transparent enough to show the enclosed well known for the occurrence of near colourless, iron oxide concentrations (Fig. 3). This is not the yellowish, brownish or greenish -brown sinhalites of case in rutile inclusions seen in many other gem quality. The internal paragenesis of these gemstones. Further, immersion microscopy re­ sinhalites often exhibit mineral inclusions such as vealed the clear transparent nature of the needles. zircon, apatite and mica, and liquid feathers A suitable optical flat was available on one of the including two-phase cavities. However, to date rear facets with an exposed portion of the sinhalite with rutile or similar needle-like inclusions inclusion. Under these conditions the electron is not known. While collecting sinhalites from this gem locality it was evident that one sample contained needle-like inclusions which are orien­ tated in certain crystallographical directions of the host gem (Fig. 1). Since it was the opinion of some gemmologists that the inclusion was rutile, further investigations were needed to confirm the nature of these needle inclusions. The gem microscope provided noteworthy infor­ mation during the investigations. It revealed the orientation of the needles parallel to the three main rhombic crystal axes. Under cross-section examina­ tion the needles were of tetragonal symmetry (Fig. 2). However, the distinct surface lustre of rutile was absent when observed under reflected Fig. 2. Apparent tetragonal symmetry of the needle-like inclu­ light. Along the length of these needles there were sion under cross-section examination. Dark field 40x.

Fig. I. Gem sinhalite of 8.43 ct from Elahera, Sri Lanka, with Fig. 3. Transparent areas ofthe needles clearly showing the iron­ orientated needle-like inclusions. oxide concentrations. Dark field 55x.

© Copyright the Gemmological Association ISSN: 0022-1252 J.J. Gemm.,Gemm., 1986,20,21986, 20, 2 99

beambeam ooff ththee microprobmicroprobee signalledsignalled ththee FeFe andand SSii peakspeaks.. However,However, thesthesee chemicachemicall componentscomponents diddid nonott showshow ananyy crystallinecrystalline naturnaturee nonorr ananyy X-rayX-ray diffractiodiffractionn patterns.patterns. BothBoth thethe gemmologicagemmologicall andand chemicachemicall investiga­investiga­ tionstions havhavee contributecontributedd inin recognizingrecognizing ththee needle­needle­ likelike inclusionsinclusions iinn ElaheraElahera gegemm sinhalite.sinhalite. NeitheNeitherr thethe microscopmicroscopee nonorr thethe microprobmicroprobee provideprovidedd anyany clueclue thatthat thethe inclusioninclusion was rutilerutile.. FurthermoreFurthermore,, thethe chemicachemicall componencomponentt withouwithoutt ananyy crystallinecrystalline naturenature suggestedsuggested thathatt thethe inclusioinclusionn was a secondarysecondary cavitycavity filledfilled witwithh iroironn oxide.oxide. ThesThesee hollowehollowedd needlesneedles probablprobablyy formeformedd inin ththee gemgem sinhalitesinhalite duringduring growthgrowth anandd werewere relatedrelated ttoo thethe mainmain crystallographicalcrystallographical directiondirectionss ofof ththee hosthost.. TheTheyy werweree thenthen filledfilled withwith ironiron oxidoxidee anandd otheotherr chemicalchemical componentscomponents fromfrom thethe neighbourinneighbouringg rocks.rocks.

[[ManuscriptManuscript received 1414 December 1985.]1985.] 101000 JJ.. Gemm.Gemm.,, 19861986,20,2, 20, 2

GeGemm hornblendhornblendee frofromm BaffiBaffinn IslandIsland,, NWTNWT,, CanadCanadaa

Willow Wight, B.A.,B.A., F.G.A.,F.G.A., F.C.Gm.A.F.C.Gm.A.

NationaNationall MuseuMuseumm ooff NaturaNaturall SciencesSciences,, MineraMinerall ScienceSciencess DivisionDivision,, OttawaOttawa,, OntarioOntario,, CanadaCanada,, K1KIAA OMOM88

IntroductioIntroductionn (Eskimos(Eskimos)) foforr decadesdecades,, anandd araree presentlpresentlyy underunder BaffiBaffinn IslanIslandd iiss situatesituatedd nortnorthh ooff ththee provincprovincee ooff claiclaimm witwithh themthem,, bubutt thertheree hahass beebeenn nnoo developmentdevelopment QuebecQuebec,, oonn ththee southersouthernn fringfringee oofthef the ArctiArcticc region,region, ooff ththee propertyproperty.. ThThee papepaper'r 'Lapi Lapiss LazulLazulii frofromm LakeLake iinn ththee DistricDistrictt ooff FranklinFranklin,, NorthwesNorthwestt TerritoriesTerritories,, HarbourHarbour,, BaffiBaffinn IslandIsland,, CanadaCanada'' (Gric(Gricee anandd Gault,Gault, CanadaCanada.. FielFieldd partiepartiess frofromm ththee NationaNationall MuseuMuseumm ooff 19831983)) givegivess a googoodd overvieovervieww ooff ththee situationsituation NaturaNaturall ScienceSciencess anandd ththee UniversitUniversityy ooff OttawOttawaa havehave regardinregardingg travetravell anandd collectincollectingg iinn ththee areaarea,, andand investigateinvestigatedd mineraminerall depositdepositss oonn southernsouthern BaffinBaffin describedescribess somsomee ooff ththee mineralmineralss thathatt havhavee beenbeen IslanIslandd witwithh aann emphasiemphasiss oonn lapilapiss lazulilazuli.. D.D.D.D. collectedcollected.. TraveTravell iiss difficuldifficultt becausbecausee iitt iiss aann isolatedisolated HogartHogarthh (1971(1971)) studiedstudied ththee lapilapiss lazullazulii depositdepositss inin areareaa witwithh onlonlyy a shorshortt ice-freice-freee perioperiodd (Jul(Julyy andand detaidetaill aass a potentiapotentiall sourcesource ooff gegemm materialmaterial.. TheseThese August)August),, anandd variablvariablee weatheweatherr includinincludingg erratierraticc fogfog depositdepositss havhavee beebeenn knowknownn ttoo ththee localocall InuitInuit banksbanks..

eA

• M,ru"ral IOl..alily

QUEBEC

'----' 100km

Fig.Fig. laola. LocationLocation mapmap forfor southernsouthern BaffinBaffin Island.Island.

Fig.Fig. lb.lb. SoperSoper RiverRiver mineralmineral localities:localities: B - northnorth lapislapis lazulilazuli deposit;deposit; C - southsouth lapislapis lazulilazuli depositdeposit andand hornblendes.hornblendes.

© CopyrightCopyright thethe GemmologicalGemmological AssociationAssociation ISSN:ISSN: 0022-12520022-1252 J.Gemm.,1986,20,2 101

Ijgpp^

Fig. 2. Camp at Soper River, Baffin Island, NWT, looking north to the lapis lazuli deposits (in white marble).

Fig 3. Phlogopite mica pit near the south lapis lazuli occurrence where facetable hornblende was found in 1980. 102 J. Gemm., 1986, 20, 2

Geology Table 1. Composition of Baffin Isalnd The lapis lazuli of southern Baffin Island lies Hornblendes within a series of highly metamorphosed sedimen­ tary rocks, the most abundant being garnet-biotite Pargasitic Pargasitic Edenitic gneiss and marble. The dolomitic marble, which Hornblende Hornblende Hornblende is coarse grained and almost white in colour, 46664 46677 46608 commonly contains diopside, amphiboles, phlogo- Si0 45.0 43.8 46.5 pite and clinohumite, as well as lazurite deposits. 2 0.73 0.45 1.1 Other minerals such as meionite, uvite, spinel, Ti02 0.11 0.0 0.0 graphite, forsterite and titanite occur more rarely in v2o5 14.1 11.7 the marble. A1203 14.7 Cr203 0.10 0.08 0.0 FeO* 0.62 1.3 0.31 MnO 0.0 0.0 0.0 Hornblende occurrence MgO 20.1 19.3 20.7 One of the areas visited by Grice and Gault in ZnO 0.0 0.0 0.0 1980 was along the Soper River some 15km north of CaO 12.1 12.7 12.1 Lake Harbour (see Figs. 1 and 2), near the Na20 3.0 2.3 3.4 previously known 'south lapis occurrence' and K20 1.3 1.6 0.50 'north lapis occurrence'. Hornblende is common F 1.4 1.6 1.1 there in the marbles as stubby, prismatic, greenish- CI 0.07 0.12 0.01 brown crystals averaging 2-3 cm long. Fragments H20** 2.0 2.6 3.0 of large crystals were found in a phlogopite mica pit a short distance from the south lapis occurrence 100.00 100.00 100.00 (Fig. 3). Some of these fragments were transparent *total iron expressed as FeO enough to facet. **by difference A simplified chemical formula derived from analysis of 46664 is (Na, K)(Ca, Na)2(Mg, Al)5(Si, Al)8022(OH, F)2. Gem hornblende 3 Hornblende is a monoclinic, calcium magnesium Calculated density 3.09 g/cm . aluminium silicate in the amphibole group. Chemi­ cal analysis is essential to determine the identity of a particular member of the amphibole group since there is much overlap in values of physical and with considerable experience in handling unusual optical properties; even X-ray data are incon­ gem materials. He used silicon carbide laps for clusive. See the 'Amphiboles-GeneraP section of cutting, and chromium oxide on an ultralap for this article for an explanation of this most compli­ polishing. The pavilion main facet was placed at cated group of minerals. 41°; the crown main angle was 42° with 5° splits Chemical analyses on specimens from several when possible. Some difficulty arose when cutting locations on Baffin Island (Grice and Gault, 1983) across the cleavages, as fraying tended to occur. showed minor variations in composition, but all The material chipped easily during polishing. were within the edenitic to pargasitic hornblende Orientation of the rough required careful considera­ range, using Leake's (1978) amphibole classification. tion of the cleavage planes and the pleochroism. Mr The faceting-grade fragments are pargasitic horn­ Grant's opinion is that faceting this material is 'not blende (NMNS 46664). Analyses are given in terribly difficult'. The four stones are fashioned in Table 1. Note that the facetable hornblende con­ various styles and weigh between 1.62 and 3.03 ct: tains traces of vanadium and chromium. The presence of vanadium was unexpected, as it was NMNS 20896 emerald step cut 3.00 ct absent in analyses of other minerals from the 10.4x6.8x6.3 mm same area. Vanadium is not usually reported in NMNS 20897 marquise step cut 1.62 ct amphiboles (Deer,. Howie and Zussman, 1963; 16.9x4.1x3.9 mm Hawthorne, 1983). In this case, the vanadium NMNS 20900 octagonal step cut 1.91 ct and chromium (along with low iron content) are 12.2x5.0x4.0 mm likely to contribute to the pleasing greenish-brown NMNS 22129 pear-shaped brilliant 3.03 ct colour, since most hornblendes are very dark and 12.5x7.5x5.4 mm unattractive. One (NMNS 20897) appears a more greenish- Four gems were faceted for the National Gem brown than the others, because of pleochroism. See Collection by Mr Arthur T. Grant, a noted faceter Figs 5 and 6. J. Gemm., 1986,20,2 103

minerals make the precise correlation of their chemical composition and optical properties prac­ tically impossible.

Identification If gem hornblende is encountered unexpectedly, it is quite likely to be mistaken for brown tourmaline (dravite or uvite). The refractive indices, birefringence and specific gravity are very similar, and they both show strong pleochroism. However, tourmaline is uniaxial, not biaxial, and shows only two dichroic colours. O,ther gems that may appear in shades of brown have either lower refractive indices e.g. quartz, or much higher indices. Grossular (hessonite) garnet, sphalerite, and diamond are singly refractive. Cassiterite, scheelite, titanite (sphene), and zircon are all over the limits of a standard refractometer, and are not likely to be mistaken for hornblende. A number of other brown gemstones with which hornblende could be confused are listed in Table 2.

Description of gem hornblende Crystal system: Monoclinic. Habit: Stubby, prismatic. Inclusions: Veils of healing feathers; colourless crystal inclusions. Colour: Greenish-brown. Lustre: Vitreous. Fluorescence: Moderate - yellow m shortwave ultraviolet; inert in longwave. Hardness: 51/2-6. Tenacity: Brittle. Cleavage: Two good, {lIO} at 56°; {100} {001} parting. Twinning: {100} simple, lamellar, common. Specific gravity: 3.09 ±0.01. Optical properties Refractive index: a 1.625-1.627 (sodium light, {:t 1.632-1.633 Rayner Dialdex Y 1.644-1.647 Fig. S. Hornblende gem: 3.00 ct, emerald cut (NMNS 20896) refractometer) from Baffin Island, NWT, Canada. average 1.626-1.645 Birefringence: 0.020 Biaxial positive. Pleochroism: Strong; green/orange/brownish- orange. ~ . Absorption spectrum: Weak; a line in the blue. '1; - . Note the wide range of values listed for common . .,.,.. - • . " r_ ~~ hornblendes in Deer, Howie and Zussman (1963): I ~ . • a1.615-1. 705; {:t1.618-1. 714; 'Y 1.632-1. 730; birefringence 0.014-0.026; optic sign positive or negative; SG 3.02-3.45. Generally, refractive indices of amphiboles are increased by the substitutions of ferrous iron for Fig. 6. Hornblende gems: 3.00 ct, emerald cut (NMNS 20896) magnesium, and aluminium for silicon. The varied and 3.03 ct, pear-shaped brilliant cut (NMNS 22129), and extensive substitutions in the hornblende from Baffin Island, NWT, Canada. 104 J. Gemm., 1986, 20, 2

Table 2. Identification of Gem Hornblende

Gemstone RI DR SG Pleochroism Other Pargasitic 1.625-1.645 0.020 B(+) 3.09 S: G/O/Br-O low dispersion Hornblende Very similar, and likely to be confused with hornblende Tourmaline 1.62-1.64 0.020 U(-) 3.06 S: Y-Br/dk Br (Dravite or Uvite) Vesuvianite 1.70-1.71 0.005 U(-) 3.3-3.5 S: G/O-Br abs. spectrum Similar, but less likely to be confused Topaz, brown 1.630-1.638 0.008 B(+) 3.53 D: Br-Y/Y/O-Y Andalusite 1.63-1.65 0.016 B(-) 3.15 S: Y/G/R Barite 1.636-1.648 0.012 B(+) 4.3-4.6 Wk: Y/Y/V Danburite 1.630-1.636 0.006 B(-) 3.00 None Siderite 1.633-1.873 0.240 U(-) 3.8-3.9 Enstatite- 1.65-1.66 0.008 B(+) 3.25 D: G/Y-G/Br-G abs. spectrum Hypersthene 1.69-1.70 0.012 B(-) 3.4 Pink to G Series to to to 1.76-1.77 0.021 3.5 Peridot, brown 1.65-1.69 0.036 B(+) 3.4 Weak abs. spectrum Diopside- 1.664-1.694 0.024 B(+) 3.29 Weak or none Hedenbergite to to to Series 1.72-1.75 0.031 3.56 It G/G-Br Sinhalite 1.67-1.71 0.038 B(-) 3.48 D: It Br/G-Br/dk Br abs. spectrum Axinite 1.678-1.680 0.01 B(-) 3.29 S: Br/V/G high dispersion Epidote 1.736-1.770 0.034 B(-) 3.4 S: G/Br/Y abs. spectrum Chrysoberyl, 1.75-1.76 0.01 B(+) 3.72 D: Y/Br abs. spectrum brown D distinct; It imperceptible; S strong; Wk weak. Colours by initial letters. Data extracted from Webster, 1983 , and Arem, 1977.

Vesuvianite (idocrase) from Laurel, Quebec has a The pargasitic hornblende from Baffin Island, similar golden-brown colour, but its refractive when properly cut to take advantage of its indices are significantly higher. Topaz has an RI in pleochroism, is an attractive gemstone with its the same region, but it has a higher SG and a lower warm brown colour showing glints of green and birefringence. Andalusite might be tricky, but it is orange. Additional material may very well be usually more greenish or reddish in appearance. obtained on future field trips to look specifically for faceting material. It was simply a lucky chance that Conclusions and future prospects some of the small amount brought back in 1980 was The number of Canadian gemstones in the suitable for faceting. National Gem Collection of Canada has been Although faceted hornblende will never be a augmented significantly in recent years by arranging commercial success with its relative softness and to have suitable pieces of field-collected minerals limited supply, it is definitely a mineralogical faceted into gems. This increase has been both in rarity, a desirable collector's stone, and another number and, more importantly, in the number of contribution to Canada's mineral and gemstone species. The Mineral Sciences Division of the heritage. National Museum of Natural Sciences has continued a long tradition of collecting in the field - one that Amphiboles - General was begun by the Geological Survey of Canada in The amphibole group consists of extremely the 1880s at the beginning of the development of important rock-forming minerals, occurring in a Canada. Very few mineral museums today have wide variety of igneous and metamorphic rocks personnel who actually go out to collect mineral throughout the world. Because they are so common, specimens. these silicate minerals are present in most mineral J. Gemm., 1986, 20, 2 105

collections, and have been rigorously investigated by mineralogists. The name 'amphibole' is derived from the Greek, amphibolos=ambiguous. It was used first by Haiiy in 1801, referring to the great variety in composition and appearance of these minerals. Many of the amphiboles share common physical properties and appear alike externally, but internally there is great diversity in chemical composition, with many atomic substitutions possible giving rise to extensive solid solution series. Many amphiboles are, there­ Fig. 7a. Each silica tetrahedron (Si04) may share two oxygen fore, often misidentified, since a visual identification atoms to form a chain. This single chain (Si03)n is found based on the usual characteristics of colour, crystal in pyroxenes. habit, specific gravity etc. is invalid. Even optical and X-ray data may be inconclusive because of overlapping values between various members of the group. Amphiboles are one of the most complicated groups of minerals, and are a challenge to all who encounter them. The advent in the 1960s of the electron micro- probe enabling rapid, accurate chemical analysis of small samples of minerals did much to promote understanding of the amphiboles, because know­ ledge of their chemistry is essential. A general classification of the amphiboles, based on crystal chemistry, was compiled by Leake (1978), after Fig. 7b. A double chain (Si4On)n occurs in amphiboles. Two years of work by a committee of the International parallel single chains may form a double chain by sharing Mineralogical Association. A precis of this highly oxygen atoms between alternate tetrahedra. technical work was presented by Robinson (1981) for mineral collectors, with particular reference to a number of well-known amphibole localities in some of the silicon in the SUQn chain, the net Ontario and New York. General background charge balance is usually maintained by substitu­ information on amphiboles is given by Deer, Howie tion of the type Mg2+Si4+ ±^ AP+A13+. and Zussman (1963). The general formula of an amphibole is given in VI IV Until now, gemmologists have not had much Leake (1978) as A0_iB2C5 T8 O22 (OH, F, Cl)2. reason to be concerned about the amphibole We are concerned here with hornblendes, which are group. The only group members commonly monoclinic, and in the calcic amphibole sub-group known in gemmological circles are tremolite and (one of four), which contains substantial calcium in actinolite, mostly because nephrite jade is a variety the B position. Then, most commonly, of them. Tremolite-actinolite-ferroactinolite form A is sodium or potassium a solid solution series varying from tremolite C is magnesium, with some ferrous iron, etc. in (Ca2Mg5Si8022 (OH, F)2), with increasing amounts six-fold co-ordination. of ferrous iron substituting for magnesium, to T is silicon, aluminium, ferric iron, etc. in four­ ferroactinolite (Ca2Fe5Si8022 (OH, F)2). These are fold co-ordination. simple amphiboles. The classification is made on the basis of which The essential feature of the structure of amphi­ elements are in B, the number of silicon atoms boles is the presence of (Si, A1)04 tetrahedra linked (silicon/aluminium ration), the magnesium/iron to form double chains with the composition ratio, and other chemical considerations, resulting (Si40n)n. These double chains are oriented in 57 recognized end-members. parallel to the c-axis, and run 'lengthwise' in A simplified version of Leake's classification of most amphibole crystals (see Fig. 7). This helps calcic amphiboles is shown in Fig. 8. Note that explain the prismatic crystal habit and the splintery common usage of the term hornblende includes 56° and 124° cleavage commonly found in amphi­ calcium-rich amphiboles having a wide range boles. The chains are separated and bonded in proportions of magnesium/iron and silicon/ laterally by planes of cations plus hydroxy 1 radicals. aluminium. The formula of our Baffin Island The crystal system may be either monoclinic or amphibole was determined from its chemical orthorhombic. When aluminium substitutes for analysis to be (Nao.65Ko.23) (Cai.8iNao.i6) 106 J. Gemm., 1986, 20, 2

A: low alkali [v.v.v.1.1.1.1.1.1 F?W,K!v!\v!v!vW mmmmmmmmm Mg rich Tremolite Kvf'XvXvXw^^ Tscherma- Actinolite ^^^^^^^^^^^M lllli kites gjS!| liuillUleildeS [Sgff!l&<$$$$ Ferro- K§^^^^:§^^S§:§J:S^^^S iililS actinolite

Fe rich [££££££££ I'iviviyjyiVi B: high alkali; low ferric iron pargasitic hornblende Mg rich V

liuillUleildePargasitesS [Sgff! j liuillUleildeS [Sgff! liuillUleildeHornblendeS [Sgff!s

Fe rich fmmmmm&ims^m C: high alkali; high ferric iron Mg rich mmmmmmmm.^'•"vlv.vjj.y.viv.v. 1.'.!'! mmmmmmmm 1 ^i^j^^'jj'fi^^ft* ] MUMMM liuillUleildeU HastingsiteS [Sgff!s liuillUleildeS [Sgff! Hornblendes ""^•^•••••'t;?vvTv? lOXfojifoXi

Fe rich

silicon rich Si/Al aluminium rich

Fig. 8. Classification of calcic amphiboles (after Leake, 1978).

(Mg4.i7Feo.07Alo.58Tio.ogCro.01Vo.01) (Si6.27Al1.73) the pargasitic hornblende region, as shown by the O21.52 (OH1.g4Fo.62Clo.02)- Because its water con­ + in Fig. 8, since it contains very little iron, and tent was determined only by difference, the value moderately high aluminium versus silicon. Because for OH is probably too high. Vanadium was such complicated calculations are necessary to arbitrarily assigned to position C based on its ionic pinpoint the exact identity of an amphibole, there radius. The calculated density for this formula will still be many occasions when a broader is 3.09, compared to the observed density of terminology will have to be used. 3.088 g/cm3. This formula places our amphibole in J. Gemm., 1986, 20, 2 107

Acknowledgements References The author wishes to thank her colleagues at the Arem, J.E. 1977. Color Encyclopedia of Gemstones, Van Nostrand National Museum of Natural Sciences, Ottawa, Reinhold, New York, 147. Canada, for their support during this project: Deer, W.A., Howie, R.A. and Zussman, J. 1963. Rock-Forming Minerals, Vol. 2. Longmans, Green, London, 379 R.A. Gault, for bringing the material to her Grice, J.D. and Gault, R.A. 1983. Lapis lazuli from Baffin Island, attention after his field work on Baffin Island, and Canada, Rocks and Minerals, 58, 12-19. for providing photographs and descriptions of the Hawthorne, F.C. 1983. The Crystal Chemistry of the Amphiboles. locality; Drs J.D. Grice and G. Robinson, for many Cana. Mineral., 21, 2, 173-480. Leake, B.E. 1978. Nomenclature of Amphiboles, Cana. Mineral., helpful discussions, and critical reading of the 16, 4, 501-20. manuscript. Special thanks are due to Mr Arthur Robinson, G. 1981. Amphiboles: A Closer Look, Rocks and T. Grant, of Hannibal, N.Y., for his careful skill in Minerals, 56, 6, 240-6. faceting the hornblende gems. Webster, R. 1983. Gems, 4th edn, Butterworth, London, p. 1006. [Manuscript received 17 September 1985.] 108108 JJ.. Gemm.Gemm.,, 19861986,20,2, 20, 2

OnOn ththee problemsproblems ofof usingusing ththee galliumgallium contentcontent asas a meansmeans ofof distinctiondistinction betweenbetween naturalnatural andand syntheticsynthetic gemstonesgemstones

Hans-Werner Schrader, Dip.Min., F.G.A. and Ulrich Henn, Dip.Min.Dip.Min.

InstituInstitutt füfurr Ede1steinforschung,Edelsteinforschung, UniversityUniversity ooff MainzMainz,, WesWestt GermanyGermany

AbstracAbstractt IInn ththee pastpast Ga-contentsGa-contents havehave beenbeen usedused toto amounamountt ooff galliumgallium iinn ththee earth'searth's cruscrustt iiss veryvery smallsmall distinguisdistinguishh naturalnatural andand syntheticsynthetic gemstonesgemstones.. TheThe comparecomparedd witwithh aluminium,aluminium, andand RosIerRosier anandd LangeLange GGaa contentscontents ooff 3232 emeralds,emeralds, 1818 corundumscorundums andand 1166 (1976)(1976) givegive a proportioproportionn ooff AI:Al: Ga=4235: 11 foforr anan chrysoberylschrysoberyls havehave beebeenn analysedanalysed bbyy neutroneutronn activa­activa­ averagaveragee compositioncomposition ofof ththee Earth'Earth'ss crust.crust. ThiThiss ratioratio tiotionn analysianalysiss (NAA).(NAA). ItIt iiss shownshown thathatt a distinctiodistinctionn ooff differdifferss inin somesome rockrockss becausbecausee galliumgallium cancan bebe naturalnatural anandd syntheticsynthetic gemstonegemstoness onon ththee basisbasis ooff enricheenrichedd atat thethe endend ooff a magmatimagmaticc cyclecycle.. TablTablee 1 theitheirr GaGa contentscontents isis nonott possible.possible. showsshows ththee theoreticatheoreticall galliumgallium contentscontents ofof somesome gemstones.gemstones. IntroductionIntroduction CertainCertain investigationsinvestigations (Ottemann(Ottemann et al. 19781978,, ThThee titletitle ofof thithiss papepaperr mamayy alreadyalready implyimply ththee kindkind HoriuchHoriuchii 1979,1979, OhguchOhguchii 1981,1981, HanniHanni andand SternStern ooff equipmenequipmentt whichwhich isis currentlycurrently usedused toto distinguishdistinguish 1982,1982, SchmetzerSchmetzer 1985)1985) oonn syntheticsynthetic anandd naturalnatural naturanaturall andand syntheticsynthetic gemstonesgemstones.. ThThee continuouscontinuous gemstonegemstoness yieldedyielded ththee followinfollowingg 'rules','rules', whosewhose developmentdevelopment ooff techniquestechniques andand thethe methodsmethods ooff accuracyaccuracy shouldshould bebe tested:tested: productioproductionn ooff syntheticsynthetic gemstonesgemstones necessitatnecessitatee newnew - corundum:corundum: galliumgallium contentscontents greatergreater thanthan 50--50- methodsmethods ooff distinctiondistinction.. InIn particulaparticularr gemstonesgemstones 200200 ppppmm proveprove a naturanaturall origin,origin, neeneedd specialspecial treatment,treatment, inin thatthat methodsmethods transferredtransferred galliugalliumm contentcontentss smallersmaller thathann 50--20050-200 ppppmm indiindi­­ frofromm geochemistrgeochemistryy havhavee ttoo workwork withoutwithout destroyingdestroying catecate a syntheticsynthetic origin,origin, thethe stone.stone. IInn spitespite ooff thithiss limitatiolimitationn thethe tracetrace - alexandrite:alexandrite: 'measurable''measurable' galliumgallium contentscontents signifysignify elemenelementt analysisanalysis,, forfor exampleexample,, cancan bbee extremelyextremely a naturalnatural origin.origin. usefuluseful.. ThiThiss kindkind ooff analysisanalysis isis ableable ttoo indicateindicate thethe environmenenvironmentt ofof ththee originorigin ofof a gemstonegemstone,, whetherwhether itit MethoMethodd bebe naturanaturall oror synthetic.synthetic. TheThe crystacrystall growthgrowth inin a RequirementsRequirements ooff methodsmethods useusedd toto investigateinvestigate cruciblcruciblee ofof platinumplatinum meansmeans thathatt inin manmanyy casescases veryvery gemstonesgemstones include:include: smallsmall tracetracess ofof thithiss elementelement (Pt(Pt)) areare incorporateincorporatedd inin - thethe methodmethod hashas toto workwork withoutwithout destruction;destruction; ththee syntheticsynthetic crystal,crystal, andand,, inin fewfew favourablefavourable casescases,, - thethe methodmethod mustmust notnot causecause anyany alterationsalterations suchsuch asas microscopicallmicroscopicallyy smallsmall platesplates ooff platinum.platinum. discoloration.discoloration. InvestigatioInvestigationn byby tractracee elementelement analysianalysiss ofof gem­gem­ NormallNormallyy ththee followinfollowingg methodsmethods araree applicable:applicable: stonesstones containingcontaining aluminiumaluminium indicateindicate variouvariouss con­con­ - X-ray-fluorescence-analysisX-ray-fluorescence-analysis (XF(XFAA) ) withwith wave­wave­ tenttentss ooff galliumgallium.. ThiThiss factfact isis notnot surprising,surprising, foforr itit length-dispersivelength-dispersive andand energy-dispersive measure­measure­ hahass beebeenn knownknown forfor somsomee yearsyears thathatt inin naturenature mentsments;; galliugalliumm iiss camouflagecamouflagedd bbyy aluminium.aluminium. ThThee similarsimilar - electronelectron microprobemicroprobe analysisanalysis (EPMA)(EPMA) withwith ionicionic radiradiii andand ththee samesame statestate ofof valencvalencee ooff wavelength-dispersivewavelength-dispersive andand energy-dispersiveenergy-dispersive aluminiualuminiumm anandd galliumgallium explainexplain thithiss behaviourbehaviour.. TheThe measurementsmeasurements;;

TablTablee 1:1: GalliumGallium contentscontents ofof somesome gemstonesgemstones theoreticallytheoretically calculatecalculatedd oonn thethe geochemicalgeochemical proportionproportion ofof AlAI:: GaGa ofof thethe Earth'sEarth's crust:crust:

EmeralEmeraldd Be3Alz(Si601s)Be3Al2(Si6018) 10.2%10.2% AlAl 2424 ppmppm GaGa CorunduCorundumm Alz0A1203 52.9%52.9% AlAl 124124 ppmppm GaGa ChrysoberyChrysoberyll BeAlBeAlz0204 42.542.5%% AAll 100100 ppmppm GaGa

© CopyrightCopyright thethe GemmologicalGemmological AssociationAssociation ISSN:ISSN: 0022-12520022-1252 J. Gemm.,Gemm., 1986,1986,20,220, 2 109109

ppmppm 4040- -1

3535- H-

30- -

25 -

20- -

15 H-

10H10 -

5 H-

o I N - N <«-N- C\J ..., r- MN h>-- XX >• HH •-• UuuU t *- Ifi a:I:: «....* <*> *- — a:>m iU")_n *- •—• ...... C"I a::: >- -- .... - CX)_::X:U).....J...J....J V> Ul Ul Ul >- t-:E:~L.i.J oU o00 o <«- ^ «a....- Q£ *3" C'"O _...J| a:> a:> a:> Ul tnv>V)l1... Ca:>O I/Ul) I/Ul) Ca:>uQ U u U ""« « « « Ul :I: ~ '" '" CD O O O l/) naturanaturall ~• synthetic---'synthetic• EmeraldEmeraldss

FigFig.. 1 : GalliuGalliumm contentcontentss ooff naturanaturall anandd synthetisyntheticc emeraldsemeralds 110110 J. Gemm.,Gemm., 1986,1986,20,2 20, 2

ppmppm 400400 -J

350350 -J

300300 -J

250250 -J

200200 -J

150150 J

100100 -—I I II

5050 J

o J I1 I I II I I I I 1 , i I , l • i I I --' -Vl a M «f 2 2 v o !r w CVJ ui rs M o o:::_::::lo:::::r::cCUJ c:cU)~~~a..::::ExCQCOhCCU')I-~~o.::Ex- »— i^QLSX i^i^ UUOUUUI/)I-H

L-~•—natura natural--'natural-----'l • '---~• synthetic----'synthetic------'synthetic • CorundumsCorundums

Fig.Fig. 2 : GalliumGallium contentscontents ofof naturanaturall anandd syntheticsynthetic corundumscorundums J. Gemm., 1986,1986,20,2 20,2 111111

ppm

2000 -

1500

1000

500 -

o C

--'J --'J £ECD::e:::1.I1O 1— =3 co SE: to « c^V)""o C~O V)CO C~O C~~O CO C~~O CO «

FigFig.. 3 : GalliuGalliumm contentcontentss ooff naturanaturall anandd synthetisyntheticc chrysoberylschrysoberyls 112 J. Gemm., 1986,20,2

Table 2: Samples investigated by NAA gallium contents from Figs 1 to 3:

BSI Emerald, Salininha, Brazil 20 ppm BS2 Emerald, Salininha, Brazil 15 ppm BSTl2 Emerald, Sta Terezinha de Goias, Brazil 28 ppm STX Emerald, Sta Terezinha de Goias, Brazil 30 ppm STY Emerald, Sta Terezinha de Goias, Brazil 20 ppm SMIl Emerald, Sta Maria de Itabira, Brazil 13 ppm SMI2 Emerald, Sta Maria de Itabira, Brazil 13 ppm FE Emerald, Ferros, Brazil 12 ppm BC Emerald, Carnaiba, Brazil 18 ppm SOCI Emerald, Socoto, Brazil 20 ppm SOC2 Emerald, Socoto, Brazil 17 ppm B14 Emerald, Brazil 19 ppm C41 Emerald, Chivor, Colombia 10 ppm C45 Emerald, Chivor, Colombia 17 ppm ARH Emerald, Zimbabwe 21 ppm A44 Emerald, Cobra Mine, Transvaal, South Africa 16 ppm A33 Emerald, Cobra Mine, Transvaal, South Africa 16 ppm ALl Emerald, Leydsdorpdistrict, South Africa 39 ppm Sl1 Emerald, Zambia 14 ppm HAB Emerald, Afghanistan 14 ppm P2 Emerald, Pakistan 14 ppm Rl Emerald, Takowaja, Siberia, USSR 11 ppm Gl Synthetic emerald, flux-method, Gilson 14 ppm G8 Synthetic emerald, flux-method, Gilson 15 ppm GIS Synthetic emerald, flux-method, Gilson 9 ppm CHI Synthetic emerald, flux-method, Chatham 13 ppm SSIJ Synthetic emerald, flux-method, Inamori 11 ppm LL Synthetic emerald, hydroth.-l1}ethod, Lechleitner 2 ppm LLl Synthetic emerald, hydroth.-method, Lechleitner 12 ppm LL9 Synthetic emerald, hydroth.-method, Lechleitner 9 ppm L Synthetic emerald, hydroth.-method, Linde o SSR Synthetic emerald, hydroth.-method, USSR 20 ppm BUR Corundum, ruby, Burma 23 ppm* SRIL Corundum, ruby, Sri Lanka 107 ppm* THAI Corundum, ruby, Thailand 28 ppm* TANS Corundum, ruby, Longido, Tanzania 22 ppm* KEN Corundum, ruby, Kenya 295 ppm* PAK Corundum, ruby, Pakistan 144 ppm* MAD Corundum, ruby, Madagascar 71 ppm* XY Corundum, ruby, unknown origin 39 ppm KA Synthetic ruby, Kashan 5 ppm KRUB Synthetic ruby, Kashan o CHR25 Synthetic ruby, Chatham 4ppm* CHR27 Synthetic ruby, Chatham 20 ppm* CHR5 Synthetic ruby, Chatham 0.6 ppm* CHR7 Synthetic ruby, Chatham 5 ppm* CHR2 Synthetic ruby, Chatham 1 ppm* CHS Synthetic sapphire, Chatham 4ppm* SPAD Synthetic sapphire, Chatham 7 ppm INA Synthetic ruby, Inamori 112 ppm ASNC Alexandrite, Novello Claims, Zimbabwe 330 ppm ATLM Alexandrite, Lake Manyara, Tanzania 210 ppm AUT Alexandrite, Takowaja, USSR 250 ppm

* after Schneider (1979) J. Gemm., 1986, 20, 2 113

ABMMG Alexandrite, Malacacheta, MG, Brazil 310 ppm AM Alexandrite, Madagascar 260 ppm AS Alexandrite, Zambia 320 ppm SACC Synthetic alexandrite, (flux) Creative Crystals 5 ppm SACZ Synthetic alexandrite, Czochralski 480 ppm CSK Chrysoberyl, Kapoi, Zimbabwe 1970 ppm CBCES Chrysoberyl, Colatina, Espirito Santo, Brazil 740 ppm CSL Chrysoberyl, Sri Lanka 790 ppm CBLFMG Chrysoberyl, Lonego de Fogo, MG, Brazil 1450 ppm CBMMG Chrysoberyl, Malacacheta, MG, Brazil 930 ppm CBAFB Chrysoberyl, Agua Fria, Bahia, Brazil 750 ppm CBJB Chrysoberyl Jaqueto, Bahia, MG, Brazil 540 ppm CBTBMG Chrysoberyl, Tres Barras, Brazil 2 ppm

- scanning electron microscope (SEM) with energy- The results are given in Table 2 and displayed in dispersive measurements; Figs. 1-3. Four natural corundums were found - neutron activation analysis (NAA) with energy- with Ga <50 ppm, and only one with >200 ppm. dispersive measurements. One synthetic alexandrite with high Ga and one Investigation of gemstones by wavelength-disper­ natural chrysoberyl with only 2 ppm Ga were sive XFA is risky because the high excitation energy found. In the emerald analyses the range of Ga may cause irreversible discoloration of gemstones contents is similar for both natural and synthetic (Bank, 1982). stones. Energy-dispersive measurements by SEM and These results indicate that the proposals concern­ EPMA have a relatively high detection limit of ing use of Ga content for distinguishing between about 2wt.% for Ga and are not sensitive enough to natural and synthetic gemstones, put forward by measure the Ga contents of gemstones. Energy- authors listed above, must be treated with caution, dispersive XFA and wavelength-dispersive EPMA and any conclusions indicated by Ga contents may detect the levels of Ga present in some should be corroborated by further tests. gemstones (EDS-XFA: ±200 ppm, WDS-EPMA: ±100 ppm). However, these values are close to the Acknowledgements detection limits, so inaccurate figures must be Thanks are due to the Max-Planck-Institute accepted. Besides this, in both methods only the Mainz, Dept. of Cosmochemistry, for providing surface of the sample can be analysed and so NAA facilities. possible variation in content caused by the structure or zoning in the material are not detected. Currently References the best method for measuring Ga is NAA as its Bank, H. 1982. Aus der Untersuchungspraxis. Z. Dt. Gemmol. detection limit is 0.5 ppm and accuracy is 3-10% of Ges., 31, 1/2, 97-8. the Ga value. However, this kind of analysis is not Hänni, H.A. and Stern, W.B. 1982. Über die Bedeutung des suitable for a large number of investigations Gallium-Nachweises in Korunden. Z. Dt. Gemmol. Ges., 31, because radioactivity decreases slowly, and a lot of 4, 255-9. Horiuchi, N. 1979. Application of multi-purpose spectrophoto­ time is needed for the whole investigation and thus meter and X-ray fluorescence analysis to distinguish natural the costs are consequently high. and synthetic alexandrites. J. Gemmol. Soc. Jap., 6, 77-80. Ohguchi, H. 1981. Application to gem identification of fluores­ cence X-ray analysis. J. Gemmol. Soc. Jap., 8, 145-9. Ottemann, J., Schmetzer, K. and Bank, H. 1978. Neue Daten zur Results Anreicherung des Elementes Gallium in Alexandriten. N.Jb. Gallium contents have been obtained by the Miner. Mh., 1978, 172-5. authors and Schneider (1979) using NAA for: Rösler, H.J. and Lange, H. 1976. Geochemische Tabellen. Enke, Stuttgart. 32 emeralds (22 natural, 10 synthetic); Schmetzer, K. 1985. Farbloser Chrysoberyll - natürlich oder 18 corundums (8 natural, 10 synthetic); and synthetisch? Z. Dt. Gemmol. Ges., 34, 1/2, 6-12. 16 chrysoberyls (6 natural alexandrites, 2 Schneider, W.L. 1979. Zur Untersuchung von natürlichen und synthetic alexandrites, and 8 natural chrysoberyls). synthetischen Kordunden mit Hilfe der Neutronenaktivierungs- analyse. Diploma thesis, Univ. Mainz. Schrader, H.W. 1981. Zur Unterscheidung von natürlichen und synthetischen Smaragden. Diploma thesis, Univ. Mainz.

[Manuscript received 6 June 1985.] 114114 JJ.. Gemm.Gemm.,, 1986,20,21986, 20, 2

PossibilitiesPossibilities andand limitationlimitationss iinn radiographicradiographic determinationdetermination ofof pearlspearls

IrmtrudI rmtrud Lorenz and Dr Karl SSchmetzer chmetzer

InstituteInstitute ooff MineralogMineralogyy andand Petrography,Petrography, UniversitUniversityy ooff HeidelbergHeidelberg,, WesWestt GermanGermanyy anandd DeutscheDeutsche StiftungStiftung EdelsteinforschungEdelsteinforschung,, Idar-Oberstein,Idar-Oberstein, WesWestt GermanGermanyy

AbstractAbstract ooff pearlpearlss witwithh radiographiradiographicc techniquestechniques werweree recentlyrecently ThThee mainmain typestypes ooff pearlpearlss availableavailable aatt presenpresentt inin publishepublishedd byby HanniHanni (1982,1983)(1982,1983) anandd BrowBrownn (1979(1979,, thethe tradtradee araree characterizecharacterizedd byby radiographicradiographic features.features. 1983).1983). HannHannii (1982(1982,1983), 1983) investigateinvestigatedd ththee diffrac­diffrac­ SystematicSystematic investigationinvestigationss ofof pearlpearlss werweree conductedconducted tiotionn patternpatternss ofof naturanaturall anandd bead-nucleatebead-nucleatedd culturedcultured usinusingg direcdirectt radiographyradiography aass welwelll aass X-rayX-ray diffractiondiffraction pearlspearls,, anandd studiedstudied thethe influencinfluencee ooff ththee externalexternal techniques.techniques. InIn additioadditionn ththee luminescencluminescencee undeunderr X­X- shapeshape ooff non-sphericanon-sphericall pearlpearlss oonn ththee diffractiondiffraction rayray excitatioexcitationn wawass examined.examined. A simplesimple diffractiondiffraction patternspatterns ofof thethe pearlspearls,, especiallespeciallyy thethe relationshiprelationship camercameraa was developedevelopedd whicwhichh enablesenables thethe investi­investi­ betweenbetween thethe directiondirection ooff ththee primarprimaryy X-raX-rayy beambeam gatiogationn ooff diffractiodiffractionn patternpatternss ooff pearlspearls inin exactlyexactly witwithh respecrespectt toto ththee externalexternal shapeshape ofof ththee pearl,pearl, i.e.i.e. definedefinedd anglesangles toto eacheach otherother.. ByBy ususee ooff aann additionaladditional thethe directiondirection inin whicwhichh a non-sphericanon-sphericall pearpearll isis samplesample holdeholderr thethe productioproductionn ofof diffractiodiffractionn patternspatterns placeplacedd iinn thethe X-rayX-ray beabeamm (cf(cf.. alsalsoo WebsterWebster,, 1957;1957; ooff ononee singlesingle pearlpearl fromfrom a necklacnecklacee isis possible.possible. Schiffman,Schiffman, 1971;1971; Duroc-DannerDuroc-Danner anandd YvonYvon,, 1983).1983). DurinDuringg ththee investigationinvestigation ofof freshwatefreshwaterr pearlspearls BrowBrownn (1979(1979,, 1983)1983) gavgavee a systematicallysystematically arrangedarranged (natural(natural andand cultureculturedd freshwaterfreshwater pearlspearls)) witwithh X-rayX-ray compilationcompilation ofof directdirect radiographsradiographs ooff naturanaturall pearls,pearls, diffractiodiffractionn techniquetechniquess a darkdark spotspot iiss generategeneratedd onon culturedcultured pearlspearls anandd imitationimitation pearlpearlss (cf(cf.. alsoalso thethe pearl'spearl's surfacesurface byby radiatioradiationn defects.defects. Webster,Webster, 1957;1957; Brown,Brown, 1980,1980,1981a 1981a,, 1981b;Brown1981b; Brown UsinUsingg a combinationcombination ooff alalll threthreee radiographicradiographic andand Mendis,Mendis, 1984).1984). techniquetechniquess availablavailablee atat presentpresent,, anan unambiguousunambiguous IInn ththee literaturliteraturee dealindealingg withwith identificatioidentificationn ofof identificatioidentificationn ofof almosalmostt evereveryy typetype ooff pearpearll foundfound inin pearlpearlss bbyy radiographiradiographicc techniquetechniquess - includingincluding ththee tradtradee iiss possible.possible. DueDue toto overlappinoverlappingg ofof theirtheir gemmologicagemmologicall textbookstextbooks - oneone finds onlyonly fefeww hintshints characteristiccharacteristic radiographiradiographicc featurefeaturess iitt iiss difficultdifficult toto onon possiblpossiblee ambiguitieambiguitiess inin radiographiradiographicc resultsresults ooff distinguisdistinguishh somesome KeshKeshii culturedcultured pearlspearls fromfrom pearlpearl investigationinvestigation,, i.e.i.e. oonn possiblpossiblee overlappingsoverlappings ooff naturalnatural seawaterseawater pearlpearlss anandd somesome non-bead-nucleatednon-bead-nucleated diagnosticdiagnostic featurefeaturess ofof pearlspearls ooff differendifferentt origin.origin. TheThe culturedcultured freshwaterfreshwater pearlpearlss fromfrom naturalnatural freshwaterfreshwater aiaimm ofof ththee presentpresent papepaperr isis ttoo makemake a contributioncontribution toto pearlspearls.. thisthis importanimportantt anandd stillstill problematiproblematicc field ooff pearlpearl SchematicSchematic diagramsdiagrams foforr determiningdetermining pearlpearlss ooff identification.identification. TheThe applicabilityapplicability ofof differendifferentt radio­radio­ unknownunknown originorigin usinusingg ththee threthreee radiographicradiographic graphicgraphic techniquetechniquess oonn ththee characterizationcharacterization ofof pearlspearls methodsmethods araree presented.presented. ooff unknownunknown origioriginn isis discusseddiscussed iinn regarregardd toto overlappingoverlapping diagnostidiagnosticc featuresfeatures ofof differendifferentt typetypess ooff IntroductionIntroduction pearlpearl whichwhich araree availablavailablee onon ththee internationalinternational SinceSince thethe middlmiddlee ofof thethe 1920s1920s radiographicradiographic marketmarket.. techniquetechniquess havehave beenbeen useusedd extensivelyextensively forfor thethe ThThee compositioncomposition andand internainternall structurestructure ofof pearlspearls distinctiondistinction ooff naturanaturall anandd cultureculturedd pearls.pearls. ByBy useuse ooff isis describedescribedd iinn detaidetaill bbyy differentdifferent authorsauthors,, e.g.e.g. ththee X-rayX-ray diffractiondiffraction method,method, whichwhich iiss alsalsoo knownknown WadaWada (1970),(1970), KoragKoragoo et al.ai. (1976),(1976), GottinGottingg (1979)(1979) asas ththee Laue-technique,Laue-technique, naturanaturall pearlpearlss areare distin­distin­ andand SimkissSimkiss andand WadaWada (1980)(1980).. OnlOnlyy thosthosee typestypes ooff guishablguishablee fromfrom bead-nucleatedbead-nucleated cultureculturedd pearls.pearls. pearlpearlss whicwhichh mainlmainlyy consisconsistt ooff smallsmall tubulatubularr crystalscrystals UsingUsing directdirect radiographradiographyy internainternall structuresstructures ooff ooff aragonitaragonitee (nacre(nacre)) exhibiexhibitt thosthosee opticaopticall propertiesproperties pearlpearlss mamayy becombecomee visiblvisiblee oonn thethe X-rayX-ray filmfilm whichwhich whicwhichh areare thethe preconditiopreconditionn ttoo ususee thethe pearlspearls forfor leadlead ttoo a conclusiveconclusive identificatioidentificationn ooff ththee pearl'spearl's jewelleryjewellery,, i.e.i.e. forfor necklacenecklacess oror rings.rings. PearlsPearls whichwhich origin.origin. ThThee luminescenceluminescence ooff pearlspearls underunder X-rayX-ray mainlmainlyy consisconsistt ofof organiorganicc mattematterr (conchiolin)(conchiolin) oorr ooff excitatioexcitationn dependsdepends oonn thethe growthgrowth environmenenvironmentt ooff prismatiprismaticc crystalcrystalss ofof aragonitaragonitee oorr calcitecalcite areare notnot ththee pearpearll (freshwater(freshwater oorr seawater).seawater). usefuusefull foforr jewellerjewelleryy anandd araree thereforetherefore ofof nono DetaileDetailedd descriptionsdescriptions ofof systematicsystematic investigationsinvestigations commerciacommerciall value.value.

© CopyrightCopyright thethe GemmologicalGemmological AssociationAssociation ISSNISSN:: 0022-12520022-1252 J.Gemm.,1986,20,2 115

Experimental details b) non-tissue-implanted cultured pearls At present the types of pearls given in the ('second crop' Biwa cultured pearls) (cf. also summary below are found on the international Farn, 1975; Brown, 1981a, 1981b). market: For the present paper several necklaces and Natural pearls single pearls (not mounted in jewellery) of each type 1. spherical, pear-shaped, button-shaped or mentioned above were examined: baroque-shaped from seawater The following numbers indicate (a) necklaces 2. spherical, pear-shaped, button-shaped or used for direct radiography and luminescence tests baroque-shaped from freshwater (pearls from necklaces used for X-ray diffraction), 3. blister pearls (removed from the shell of the (b) single pearls used for direct radiography and oyster, with or without shell fragments) from luminescence tests (single pearls used for X-ray seawater diffraction). Cultured pearls from seawater 1. bead-nucleated cultured pearls 2. cultured blister pearls (e.g. Mabe composite Natural pearls (a) (b) cultured pearls) from seawater 12(10), 90 (8) 3. non-bead-nucleated, non-tissue-implanted cul­ from freshwater - -,24 (4) tured pearls (Keshi cultured pearls); pearls of blister pearls from seawater - -, 2 - this type (adventitious pearls) are accidentally formed in bead-nucleated oysters (cf. Brown, Cultured pearls, seawater 1980). bead-nucleated pearls 25(15), 55(10) Cultured pearls from freshwater blister pearls - -, 2 - 1. bead-nucleated cultured pearls Keshi pearls 2 -, 30 (8) 2. cultured blister pearls 3. non-bead-nucleated cultured pearls Cultured pearls, freshwater a) tissue-implanted cultured pearls ('first crop' bead-nucleated pearls - -, 2 (2) Biwa cultured pearls, Chinese cultured fresh­ blister pearls water pearls) non-bead-nucleated pearls 30 (5)^ 20 (8)

Fig. 1. X-ray diffraction camera (Laue-camera) for pearls; (a) collimator, (b) vertical rotation axis with a dial having 360° subdivisions, (c) horizontal rotation axis with a dial having 360° subdivisions, (d) pearl, (e) film cassette, (f) camera box covered inside with lead sheet; length of the camera approximately 25 cm. 116 J. Gemm., 1986, 20, 2

Direct radiography was performed according to the collimator of the X-ray beam. By using this the experimental conditions already described in sample holder X-ray diffraction photographs of detail by Webster (1957) using immersion liquids. single pearls in necklaces are possible in all These experimental conditions (Webster, 1957) are directions which are adjustable by a rotation of the principally different from the method of Brown pearl with the string of the necklace as a rotation (1983), who investigated pearls and pearl necklaces axis. by direct radiography without using immersion Experimental conditions: two different tubes liquids. Mainly carbon tetrachloride and tetra- were used for diffraction experiments, copper chloroethylene were used. Direct radiography with target, 40 kV, 20 mA or iron target, 36 kV, 26 mA; immersion liquids, in general, gave better results in pearl to target distance 12 cm, pearl to collimator pearl testing than without. and distances 0.5, 1.5 or 2.5 cm) three different The luminescence of pearls under X-ray excitation collimators), pearl to film distances 8, 12 or 16 cm; was investigated before the pearls were placed in the exposure times 2-16 h; film type Agfa OSRAY M3. immersion liquid for direct radiography. The reaction of the pearl under the primary X-ray beam Results was observed in an absolutely darkened room Generally, the results of our experimental investi­ through a window of lead-bearing glass in the gations confirm the data widely scattered in the camera used for direct radiography. In this time- literature as well as the results of the most recent saving procedure both methods were performed in systematic examinations by Hanni (1982,1983) and one single working step. Brown (1979, 1983). Some results complete the Experimental conditions: copper target, 35 kV, data available in the literature, especially the data of 24 mA; pearl to target distance variable 20-80 cm certain types of pearls which were not previously (mainly a distance of 20 cm was used); exposure investigated by a combination of all three experi­ time 30 seconds. mental methods used in our study. The X-ray diffraction patterns of pearls were Imitation pearls and cultured blister pearls are photographed in a specially developed diffraction often recognizable without the application of camera (Fig. 1). The camera works according to the radiographic techniques (Webster, 1973). Imitation principle of a two-circle goniometer. The pearl is pearls are distinguishable from natural and cultured placed at various exactly defined angles with pearls by examination of the surface structure reference to the primary X-ray beam using both a and/or by their different density. Cultured blister horizontal and a vertical rotation axis. For the pearls (e.g. Mabe composite cultured pearls) are investigation of single pearls in necklaces an identifiable due to their characteristic external form additional sample holder is used (Fig. 2), which and due to their artificial supplement on the enables the attachment of the necklace in front of backside of the sample. Therefore these two types of material are not discussed in further detail. The characteristic properties of natural pearls and cultured pearls which are determinable by radiographic techniques are summarized in Table 1. a a Direct radiography The diagnostic features in direct radiographs of \ I"MV DllTLb pearls are due to the different X-ray transparency of calcium carbonate (mainly aragonite with low X-ray transparency) and organic matter (conchiolin with high X-ray transparency). The not absorbed fractions of the primary beam cause the blackening of the X- ray film. In order to recognize unambiguously p characteristic structures of pearls, several X-ray pictures in various orientations generally have to be c taken. The best method to hold pearls steady is to use small patches of paper tissue. The direct radiographs of a fraction of natural pearls (seawater and freshwater pearls) and of some Keshi cultured pearls reveal circles, arcs or regular Fig. 2. Additional sample holder for X-ray diffraction photo­ cavities close to the centre of the pearls. These graphs of single pearls from necklaces; (a) forks to support the necklace, (b) necklace, (c) movable fork with diagnostic structures in the X-ray film are caused by screw set adjustable according to the diameter of the pearl; conchiolin in the centre or between the concentric length approximately 8 cm. layers of aragonite crystals. J. Gemm.,Gemm., 1986,1986,20,2 20, 2 117 117

TablTablee 1.1. ThThee differendifferentt typestypes ofof pearlpearl andand theirtheir radiographiradiographicc propertiesproperties ofof diagnostidiagnosticc valuevalue

TypTypee ooff pearlpearl DirectDirect LuminescencLuminescencee underunder X-rayX-ray diffractiondiffraction RadiationRadiation radiographs*radiographs* X-raX-rayy excitationexcitation patterns*patterns*** defectsdefects

naturanaturall freshwaterfreshwater variablevariable:: weakweak toto mediummedium toto pearlspearls strongstrong strongstrong naturanaturall seawaterseawater finefine circlescircles oorr arcsarcs identicalidentical atat pearlpearlss closclosee ttoo thethe centrecentre differendifferentt anglesangles ttoo eacheach other,other, notnot KeshKeshii culturedcultured nonott observedobserved consistingconsisting ooff a observeobservedd pearlpearlss systemsystem ofof descretedescrete non-bead-non-bead- spotsspots havinhavingg a six-six­ nucleatenucleatedd foldfold symmetrysymmetry oorr ooff larglargee irregularirregular culturedcultured freshwaterfreshwater a diffusediffuse halohalo patchepatchess ooff variablevariable variablevariable:: mediummedium pearlpearlss radiolucencyradiolucency toto strongstrong mediummedium toto strongstrong bead-nucleatedbead-nucleated differentdifferent aatt rightright cultureculturedd strongstrong anglesangles ttoo eacheach freshwatefreshwaterr pearlspearls externalexternal circlecircless oror otherother,, consistinconsistingg ooff a arcsarcs,, radio-opaqueradio-opaque systemsystem ofof discretediscrete bead-nucleatedbead-nucleated variablevariable:: notnot beadbead inin thethe centrecentre spotsspots havinhavingg a twotwo-­ culturedcultured observedobserved toto foldfold symmetrysymmetry (first(first seawaterseawater pearlspearls mediumediumm nonott direction)direction) oror ofof a observeobservedd systemsystem ooff discretediscrete spotsspots havinhavingg a six-six­ Ifolfold d symmetrysymmetry oorr ooff a diffusediffuse halohalo 1(second(secon d direction)direction) * diagnosticdiagnostic featuresfeatures areare notnot observableobservable forfor allall pearlspearls **** forfor sphericalspherical oror almostalmost sphericalspherical pearlspearls

CultureCulturedd pearlpearlss withwith mother-of-pearmother-of-pearll nucleinuclei similarsimilar structuresstructures iiss thoughtthought ttoo bbee duduee ttoo irregularirregular (bead-nucleated(bead-nucleated cultureculturedd seawaterseawater anandd freshwaterfreshwater concentrationconcentrationss ofof organiorganicc mattematterr occasionallyoccasionally pearlspearls)) araree recognizablerecognizable onon thethe direcdirectt X-rayX-ray picturepicture associateassociatedd withwith shellshell fragmentfragmentss (cf.(cf. BrownBrown,, 1980,1980, bbyy aann almostalmost circularcircular structurestructure closecloserr ttoo ththee ririmm ofof 1981a,1981a, 1981b).1981b). ththee pearlpearl.. InIn general,general, thithiss circularcircular structurestructure isis interruptedinterrupted anandd sometimessometimes onlonlyy shortshort partpartss areare Luminescence under under X X-ray-ray excitation excitation visible.visible. ThThee diagnosticdiagnostic featurefeaturess ofof bead-nucleatedbead-nucleated TheThe differendifferentt reactionreaction ooff pearlpearlss undeunderr X-rayX-ray cultureculturedd pearlpearlss araree causecausedd bbyy a layelayerr ooff conchiolinconchiolin excitatioexcitationn iiss explaineexplainedd bbyy theitheirr differendifferentt manganesemanganese coatincoatingg thethe mother-of-pearmother-of-pearll beabeadd iinn a first stepstep ooff contentcontentss assumedassumed toto bbee causedcaused bbyy differentdifferent growtgrowthh afterafter ththee seedseed isis insertedinserted intintoo thethe oyster.oyster. manganesemanganese concentrationconcentrationss iinn seawateseawaterr anandd fresh­fresh­ ThereforThereforee aann outlineoutline ooff thethe beadbead whicwhichh mamayy bebe waterwater (Waldeck(Waldeck anandd BaierBaier,, 1970;1970; WebsterWebster,, 1975).1975). coatecoatedd bbyy a conchiolinconchiolin layerlayer ooff irregularirregular thicknessthickness UnderUnder thethe experimentalexperimental conditionconditionss usedused inin thisthis becomebecomess visiblvisiblee onon thethe X-rayX-ray picture.picture. study,study, naturalnatural pearlpearlss growngrown iinn a seawaterseawater environ­environ­ ThThee directdirect radiographradiographss ofof non-bead-nucleatednon-bead-nucleated menmentt dodo nonott showshow luminescencluminescencee undeunderr X-rayX-ray tissue-implantetissue-implantedd freshwatefreshwaterr pearlpearlss (Biwa(Biwa culturedcultured excitation.excitation. ThThee luminescenceluminescence behavioubehaviourr ooff thethe pearlpearlss andand ChinesChinesee freshwaterfreshwater cultureculturedd pearlspearls)) andand bead-nucleatebead-nucleatedd cultureculturedd seawaterseawater pearlpearlss isis different.different. mosmostt ofof KeshKeshii cultureculturedd pearlpearlss yieldyield irregularlyirregularly DependentDependent onon ththee thicknesthicknesss ooff theitheirr skinskin (layer(layer ofof formeformedd structuresstructures ooff variablvariablee X-raX-rayy transparencytransparency inin nacre)nacre) aroundaround thethe mother-of-pearlmother-of-pearl nucleunucleuss (which(which thethe centrcentree ofof ththee pearls.pearls. InIn thethe cascasee ooff freshwaterfreshwater iiss artificiallartificiallyy produceproducedd frofromm shellsshells growgrownn inin cultureculturedd pearlspearls,, thesthesee structuresstructures araree causedcaused byby freshwater),freshwater), a weaweakk luminescenceluminescence iiss observeobservedd inin cavitiescavities anandd irregularlirregularlyy depositedepositedd conchioliconchiolinn layers.layers. thin-skinnedthin-skinned pearlspearls.. InIn pearlspearls witwithh a greagreatt thicknessthickness InIn ththee cascasee ofof KeshiKeshi culturedcultured pearlspearls,, thethe reasoreasonn forfor ofof ththee layerlayer ooff nacrenacre growngrown iinn seawater,seawater, nono reactionreaction 118 J. Gemm., 1986, 20, 2

under X-ray excitation was observed. On the Therefore, in general, at least two or even more contrary, pearls grown in freshwater - natural diffraction photographs have to be taken at exactly freshwater pearls and cultured freshwater pearls - defined angles to each other. This procedure is reveal a distinct reaction under X-ray excitation. easily practicable using the diffraction camera This greenish luminescence of freshwater pearls is described in this paper (Fig. 1), which enables of variable intensity (weak, medium or strong) and different discrete orientations of the pearl without is thought to be dependent on growth conditions, the necessity of removing the pearl from the i.e. the trace element content of the growth camera. environment. A strong luminescence under X-ray The diffraction patterns of non-spherical pearls excitation was observed from Biwa cultured pearls are extremely complex depending on the orientation as well as from natural freshwater pearls from of the pearl in the X-ray beam (cf. Hanni, 1982, Scotland. 1983). In such cases an identification of a pearl of unknown origin with the Laue-method only may X-ray diffraction become very difficult or even impossible. The application of the Laue-method for pearls is The Laue-pattern of a thick-skinned cultured based on the different arrangements of small pearl with a relatively small mother-of-pearl nucleus calcium carbonate crystals (mainly aragonite) in the consists of a pattern with a six-fold symmetry layers of natural pearls and bead-nucleated cultured (caused by the skin) which is superimposed on a pearls, respectively. The symmetry of the diffraction pattern with a two-fold symmetry (caused by the pattern is dependent on the symmetrical relationship nucleus). The pattern of the nucleus, however, was in the pearl parallel to the primary X-ray beam. In clearly visible in the diffraction patterns of all almost spherical natural pearls with a concentric samples investigated in our laboratory. layered structure of aragonite platelets, identical relationships are found in different orientations of Radiation defects the pearl with respect to the X-ray beam. In Having investigated the diffraction pattern of contrast, the symmetrical relationships in bead- freshwater pearls (natural and cultured freshwater nucleated cultured pearls are different in directions pearls of all types) under the experimental conditions parallel and perpendicular to the orientation of the mentioned above a dark circular spot was inciden­ nearly straight parallel aragonite layers of the tally observed on the surface of the pearl. Radiation nucleus. defects were never observed during the investigation A concentric layered structure is found in all of luminescence under X-ray excitation or after natural pearls (natural seawater and freshwater direct radiography of freshwater pearls. After the pearls), in non-bead-nucleated cultured freshwater investigation of seawater pearls by X-ray diffraction pearls and in Keshi cultured pearls. In these techniques no radiation defects were observed. groups, assuming the X-ray beam passes through Similar radiation defects were also produced on the the centre of an almost spherical pearl, the surface of a bead-nucleus (grown in freshwater!) diffraction pattern consists of a system of discrete from which the skin of nacre had been removed. spots having a six-fold symmetry or of a nearly The radiation defects were found to be reversible. concentric halo. Every transition between both They disappeared after exposing the pearl to direct basic types of pattern is observable. sunlight for several weeks, e.g. on a window The diffraction pattern of bead-nucleated cultured seat. Nevertheless, the application of the X-ray pearls (seawater or freshwater) is identical with the diffraction method for the determination of fresh­ diffraction pattern of pearls with a concentric water pearls should be avoided if possible. The layered structure under the precondition that the identification of freshwater pearls can be made from direction of the primary X-ray beam is perpen­ observations of luminescence under X-ray excitation. dicular to the aragonite layers of the nucleus. However, in other directions, especially parallel to Possibilities of radiographic determination of pearls of the aragonite layers of the nucleus, the diffraction unknown origin pattern of bead-nucleated cultured pearls, in The most important result of our systematic general, consists of a system of discrete spots having investigations is the fact that most pearls available a two-fold symmetry. in the trade are adequately characterizable and Under the precondition that the first diffraction sufficiently identifiable by a combination of the pattern of a pearl of unknown origin shows a six­ three radiographic techniques described in this fold symmetry (as described above), a second Laue- paper (Table 1). The application of only one of the pattern in a direction perpendicular to the first methods mentioned above allows the unambiguous orientation of the pearl has to be conducted in order determination of only a minor part of the pearls to determine the possible presence of a nucleus. found on the market. J. Gemm., 1986, 20, 2 119

As already described, diagnostic internal struc­ tissue implantation (cf. Brown, 1981a, 1981b; 'first tures of a pearl may become visible on the X-ray crop' and 'second crop' Biwa cultured pearls). Both film by the application of direct radiographic types of non-bead-nucleated cultured pearls, how­ techniques. However, structures which are suitable ever, are recognizable due to an intense and for an unambiguous determination of the sample diagnostic luminescence under X-ray excitation. were recognized in only 10-20% of natural pearls. The luminescent behaviour of pearls under X- About 60% of direct radiographs of bead-nucleated ray excitation was examined in one single working cultured pearls (seawater and freshwater) revealed step together with the direct radiographic exposure. diagnostic structures on the X-ray film, i.e. the The information obtainable from this test alone is characteristic circle close to the rim of the pearl (or not sufficient to characterize a pearl of unknown at least part of it) became visible. The percentage of origin. However, the luminescence under X-ray pearls which showed diagnostic structures on their excitation is suitable to give important clues which X-ray photograph, however, was extremely variable are useful to complete the information from the between different necklaces, e.g. the percentage of direct radiograph and, if necessary, the diffraction diagnostic structures was found to vary between 16 pattern. In addition, the investigation of lumines­ and 94%. In baroque-shaped or non-spherical bead- cence under X-ray excitation is important for the nucleated cultured pearls, the mother-of-pearl recognition of freshwater pearls in order to avoid nucleus was recognizable on the X-ray photograph radiation damage caused by the Laue-method. in almost 100% of all pearls investigated. These The investigation of the diffraction patterns can results indicate that the application of the diffraction prove the presence or absence of a mother-of-pearl method to non-spherical pearls is rarely required. nucleus in pearls of unknown origin (seawater and In thin-skinned spherical pearls, however, the freshwater pearls). The Laue-method is not able to outline of the mother-of-pearl nucleus was seldom distinguish between natural pearls, non-bead- recognizable. The best experimental condition was nucleated cultured pearls and Keshi cultured a horizontal orientation of the drill hole; under this pearls. However, it is very useful to characterize precondition, the outline of the nucleus became pearls without diagnostic properties in the direct visible close to the drill hole. Therefore, the radiograph, e.g. thin-skinned bead-nucleated investigation of the diffraction pattern is of great cultured pearls as well as extremely thick-skinned importance for the determination of thin-skinned bead-nucleated cultured pearls. bead-nucleated pearls. In our study the direct radiographs of Keshi Determinative procedure for the characterization of cultured pearls yielded, in about 80% of the samples pearls of unknown origin investigated, diagnostic structures which are similar In general, only those pearls which are not to those of non-bead-nucleated tissue-implanted determinable according to their external features, cultured pearls. In about 10% of the X-ray pictures e.g. surface properties or external shape, are diagnostic structures were recognized which are submitted for radiographic examination. Without close to those only seen in the radiographs of natural application of radiographic procedures the following pearls. types of pearl are often recognizable: cultured Non-bead-nucleated cultured freshwater pearls blister pearls (e.g. Mabe composite cultured pearls), from China are, in general, recognizable due to most non-bead-nucleated cultured freshwater pearls their external shape as well as to their characteristic from China, a fraction of non-bead-nucleated surface structures. A large proportion of non-bead- cultured freshwater pearls from Japan (Biwa nucleated cultured freshwater pearls from Japan cultured pearls), and imitation pearls. (Biwa cultured pearls) is easily recognizable by their It is suggested that the determination of pearls of external shape. In addition, both types of cultured unknown origin begins with several direct radio­ pearls reveal typical radiographic features in the X- graphs in various orientations of the pearl. In the ray photograph. Spherical or nearly spherical non- same step the luminescence of pearls under X-ray bead-nucleated cultured freshwater pearls (Biwa excitation is investigated. Assuming that the direct cultured pearls), however, are easily mistaken for radiographs reveal structures of diagnostic value, natural pearls or bead-nucleated cultured pearls. i.e. structures which unambiguously indicate the The direct radiographs of this type of Biwa cultured internal structure of the pearl, an unequivocal pearls revealed in only 20% of the samples the identification of most of those samples is possible by diagnostic blacking of irregular formed structures combining direct radiography with luminescence. of high X-ray transparency. These results indicate A schematic diagram for determinative purposes of that this second type of non-bead-nucleated Biwa pearls with diagnostic structures in the direct cultured pearls without characteristic properties in radiograph is given in Fig. 3. For those pearls the direct X-ray photograph was grown without mentioned above, diffraction photographs can be ...... o N 00 "-' "-' :£i Cl .... 3 ? p P' 120 J.';-' Gemm., 1986,20,1986,20,2

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Fig. 4. Schematic diagram for determining pearls of unknown origin using X-ray diffraction radiography. The direct radiographs of about 10% revealed structures similar to and luminescence under X-ray excitation (for pearls without diagnostic structures in natural seawater pearls, and those of about 10% were of no diagnostic value. the direct radiograph). *** Natural freshwater pearls were often distinguishable by visual appearance from * Pearls with the properties indicated are supposedly 'second crop' Biwa cultured cultured freshwater pearls; natural freshwater pearls without diagnostic N pearls. properties in the direct radiograph and having the strong luminescence of Biwa - ** About 80% of Keshi cultured pearls in this study were recognizable by direct cultured pearls are extremely rare. - 122 J. Gemm., 1986, 20, 2 taken as a supplementary test although in those necklace can solve this problem (diffraction photo­ cases the application of this method is not necessary. graphs of pearls from necklaces can be done by use Difficulties arise in the determination of some of the sample holder pictured in Fig. 2). Only those Keshi cultured pearls which reveal no structures in pearls of the necklace having a diameter of at least the X-ray photograph or show diagnostic structures 3 mm can be investigated by X-ray diffraction indicating a natural pearl. The application of the photography. Laue-method in addition does not solve these In conclusion it can be stated that necklaces of determinative problems. uniform composition, i.e. necklaces consisting of In addition to the luminescence under X-ray one type of pearl only, are easily determinable by a excitation, diffraction photographs are necessary combination of all three methods discussed in this for those pearls without determinative features in paper. On the contrary, the determination of mixed direct radiographs. The investigation of freshwater necklaces, i.e. necklaces consisting of pearls of pearls by the diffraction technique can cause different origins, may be extremely complicated radiation damage. Thus, the diffraction method and time consuming. should be avoided for those pearls which are In general, single pearls of distinct size are also recognized by luminescence as freshwater-grown. determinable by a combination of all three X-ray Without positive results of direct radiography an techniques, though difficulties may arise from unequivocal identification by the combination of certain types of pearls. The determination of small luminescence and diffraction radiography is possible pearls by radiographic methods, however, may only for a fraction of the pearls. A schematic become difficult or even impossible. diagram for this situation is given in Fig. 4. By the application of luminescence investigation and Acknowledgements diffraction radiography only, natural seawater The authors are grateful to Mr H. Hahn and Mr pearls are not distinguishable from Keshi cultured E. Hahn, of Idar-Oberstein, West Germany, for pearls. Also a fraction of natural freshwater pearls information about the pearl market and for a critical cannot be distinguished from non-bead-nucleated discussion of the experimental results presented in tissue or non-tissue-implanted cultured freshwater this paper. The firms of Ph. Becker & Co., J. Graef pearls by this approach. According to the results of & Co. and A. Hahn, of Idar-Oberstein, and E. this study, about 80% of Keshi cultured pearls are Eugster, of Zurich, Switzerland, submitted pearls recognizable by direct radiography. For the remain­ and necklaces. ing 20%, the three types of radiographic techniques are not suitable for an unambiguous distinction from natural seawater pearls. Natural freshwater pearls without diagnostic features in the direct radiograph but with a strong luminescence are easily mistaken for spherical or nearly spherical References Biwa cultured pearls without diagnostic structures Brown, G. 1979. The diagnostic radiographic structure of pearls. (non-bead-nucleated non-tissue-implantated cul­ J. Gemm., 16, 501-11. tured freshwater pearls). However, natural pearls Brown, G. 1980. Gemmology study club report: The radiographic having these properties are extremely rare. features of Keshi-pearls. Aust. Gemmol., 14, 28-9. Brown, G. 1981a. The Biwa pearl. Aust. Gemmol, 14, 153-6. Brown, G. 1981b. The Biwa pearl. Part 2. Aust. Gemmol., 14, Additional remarks 186-93. During this study it became evident that necklaces Brown, G. 1983. Direct X-radiography of pearls. Aust. Gemmol., 15, 105-21. found in the trade may consist of both natural Brown, G. and Mendis, H. 1984. An unusual cultured pearl pearls and bead-nucleated cultured pearls, which necklace. Aust. Gemmol., 15, 155-7. are often thin-skinned cultured pearls. It is self- Duroc-Danner, J.M. and Yvon, K. 1983. On the identification of evident that an unequivocal characterization of pearls by X-ray diffraction. J. Gemm., 18, 715-22. Farn, A.E. 1975. Pearls. J. Gemm., 14, 382-5. necklaces composed of natural and cultured pearls Gotting, K. J. 1979. X-ray microanalysis in pearls of Mytilus edulis. is extremely difficult. If a necklace of unknown L. (Bivalvia). Experienta, 35, 756. origin consists, e.g. of 100 pearls, and if furthermore Hanni, H.A. 1982. Perlendiagnose mit Laue-Aufnahmen. Z. Dt. by direct radiography about 10% of the pearls were Gemmol. Ges., 31, 131-42. recognized as natural and about 10% of the pearls Hanni, H.A. 1983. The influence of the internal structure of pearls on Lauegrams. J. Gemm., 18, 386-400. were recognized as cultured pearls, the determination Korago, A.A., Golubev, B.F., Kesarev, O.V., Muratov, I.G. and of the remaining 80% of the pearls without Shitov, V.A. 1976. The composition and structure of pearls diagnostic structures in the direct radiograph will from the northwestern USSR. Dokl. Akad. Nauk SSSR, be extremely time consuming although X-ray Earth Science Sections, 228, 122-5. Schiffmann, C.A. 1971. Pearl identification. J. Gemm., 12, diffraction photographs of every pearl of the 284-96. J.J. Gemm. Gemm.,, 1986 1986,20,2, 20, 2 123

SimkissSimkiss,, K K.. an andd Wada Wada,, K K.. 1980 1980.. Culture Culturedd pearl pearlss - -commercializecommercializedd biomineralisationbiomineralisation.. Endeavour, Endeavour, 4 ,4, 32-7 32-7.. StrackStrack,, EE.. 19821982.. Perlenfibel.Perlenfibel. p.168.p.168. Rühle-DiebeneRiihle-Diebenerr Verl.VerI.,, StuttgartStuttgart.. WadaWada,, K K.. 1970 1970.. Structure Structure and and formation formation of of pearls. pearls. Profile Profiless o fof Jap Jap.. SciencSciencee an andd Scientists Scientists,, 227-224 227-224.. WaldeckWaldeck,, H H.. an andd Baier Baier,, E E.. 1970 1970.. Manganverteilun Manganverteilungg in in Zuchtperlen Zuchtperlen.. ZZ.. Dt. Dt. Gemmol. Gemmol. Ges., Ges., 19 19,, 99-102 99-102.. WebsterWebster,, R R.. 19571957.. ThThee pearl pearl.. Gemmologist, Gemmologist, 26 26,, 79-879-855 102-9102-9,, 126-32126-32,, 147-52 147-52,, 158-63 158--63,, 178-84 178-84,200-7,213-17., 200-7, 213-17. WebsterWebster,, R R.. 1973 1973.. A A moder modernn surve surveyy o off imitatio imitationn pearls pearls.].. J. Gemm., 1313,, 209-19 209-19.. WebsterWebster,, R R.. 1975 1975.. Gems. Gems. Their Their sources, sources, descriptions and and identification. identification. 3r3rdd edn edn.. p.938 p.938.. Butterworths Butterworths,, London London..

[Manuscrip[Manuscriptt received received 2525 JanuaryJanuary 19861986.].] 124 J. Gemm., 1986, 20, 2

Gemmological Abstracts

ALEXANDER, P.O. 1985. Looking for diamonds? BANK H. 1985. Farbloser Skolezit aus Indien. Try geobotany. Wahroongai News, 19, 7, 18-20. (Colourless scolecite from India.) Z. Dt. Gemmol. The strongly mineralized ultramafic rocks of Ges.y 34, 3/4, 167-8, bibl. kimberlite have been found to promote vegetation The transparent colourless crystals were offered so that it stands out in contrast to the sparse cover of as natrolite, but were shown to be scolecite, the surrounding rock, which is also ultramafic but SG2.21,RI nx1.512,ny 1.518.nz 1.523. E.S. less rich in phosphorus and potassium. Geobotanical studies of the Hinota kimberlite BANK, H., KNIEWALD, G. 1985. Farbloser pipe have shown that the vegetation in the form of Hyalophan von Busovaca, Jugoslawien. (Colour­ large and healthy trees is in such marked contrast as less hyalophane from Busovaca, Yugoslavia.) Z. to be discernible from a distance or from the air. It is Dt. Gemmol. Ges., 34, 3/4, 169-70. suggested that these differences in vegetation may The material comes from Busovaca in central be useful in locating buried kimberlite pipes in Bosnia, about 50 km north-west of Sarajevo. It is 3 areas of known potential, with particular reference colourless, transparent, density 2.89 g/cm , RI nx to the Panna diamond belt of Central India. R.K.M. 1.541-1.543, ny 1.546-1.549, nz 1.549-1.551, DR 0.007-0.008, and was found to be hyalophane .E.S. BAGUENA RUIZ, C. 1985. Estudio comparativo de tres tipos de 'hematites'. (Comparative study BOUSKA, V., FRYDRYCH, M., TURNOVEC, of three types of 'hematites'.) Gemologia, 22, I. 1985. Moldavites as precious stones. Z. Dt. 65/66, 48-59, 9 figs (6 in colour). Gemmol. Ges., 34,3/4,83-91,8 figs (3 in colour). Three types of material which have been given Prehistoric man was already attracted by molda­ the name hematite are examined. X-ray diffraction vites, found near Willendorf in Austria and Oslavany is used to determine crystal structure and electrical in Czechoslovakia. There are no medieval reports conductivity studies establish the identity of the on moldavites. They were used as decorative stones specimens conclusively. M.O'D. from the 18th century. Examples of cut moldavites set in gold were shown at the National Exhibition in BALFOUR, I. 1985. Famous diamonds of the Prague in 1891. Two of the authors work in the world, XXIV. The 'Nassak' diamond. Indiaqua, co-operative 'Granat' in Czechoslovakia which 42, 3, 133-5, illus. produces modern moldavite jewellery, mainly set The diamond known as 'Nassak' was named after with uncut stones, but moldavite is also cut the town of Nasil situated 110 miles north of and two artists are mentioned as specializing in Bombay. It was 'liberated' in 1818 by British forces engraving moldavites. E.S. as part of the booty in the last of the Mahratta Wars, and was handed over to the East India Company. Its BOWERSOX, G.W. 1985. A status report on shape then was triangular, and it weighed around gemstones from Afghanistan. Gems Gemol., 89 carats. After passing through many hands it was XXI, 4, 192-204, 14 figs in colour. purchased by Harry Winston who had it re-cut to Report on production of emerald, tourmaline, its present shape as an emerald-cut weighing kunzite and ruby, at the western end of the 43.38 carats. It was finally acquired by the King of Himalayas in NE Afghanistan, which has increased Saudi Arabia in 1977. P.G.R. dramatically since the Russian invasion greatly increased the need for foreign currency. Fine BANCROFT, P. 1985. The story behind the book. emerald from the Panjshir Valley (bombs sometimes Lapidary J., 39, 9, 26-37, 8 figs (3 in colour). reveal new localities), RI and SG are high comparable The book is Gem and Crystal Treasures* and the with those for South African stones. Nuristan article gives some of the anecdotes amassed by the region produces fine aquamarine, tourmaline in author while preparing the book. M.O'D. pink, blue, green and multi-coloured. Some of the finest kunzite comes from this region. Fine rubies * Reviewed in J. Gemm., 1985, XIX, 8, 733. occur in marble in Sorobi District at Jegdalek, but J. Gemm., 1986, 20, 2 125 war precludes serious mining. Considerable quanti­ the smoky colour is not developed. Amethyst ties of fine lapis lazuli are also coming across the colour is produced by an absorption band of the border to Pakistan. The gems are back-packed out, Fe4+. In nature Fe3+ only predominates over Fe4+ the miners often walking hundreds of miles through in quartz formed under shallow-growth conditions remote and difficult country. The need for foreign such as cavities or geodes. Amethyst coloration is exchange is great. R. K. M. found in these conditions only. M.O'D.

CARUBA, R., BAUMER, A., GANTEAUME, COHEN, A.J., MAKAR, L.N. 1985. Dynamic M., IACCONI, P. 1985. An experimental study biaxial absorption spectra of Ti3+ and Fe2+ in a of hydroxyl groups and water in synthetic and natural rose quartz crystal. Mineralogical Maga­ natural zircons: a model of the metamict state. zine, 49, 354, 709-15, 4 figs. American Mineralogist, 70, 1224-31, 8 figs. The absorption spectrum of Ti3+ in quartz is Zircon has been synthesized between 200 and characteristic for Ti in an octahedral site. However, 800°C at 1 kbar in a fluorinated environment. It is a the high oscillator strength of the band indicates solid solution in which the (OH,F)4 group takes the intensive charge transfer, and this is most likely to 4+ place of a Si04 tetrahedron and is of the type take place between a substitutional Ti and an 3+ Zr(Si04)i_x(OH,F)4x with 0.2Sapphires from Australia. cutting tool. It is concluded that many of the Gems GemoL, XXI, 3, 130-46, 21 figs in colour. previously unexplained differences in mechanical A good account of the sapphire fields at Inverell, properties of diamond can now be explained by the NSW, and at Anakie in Queensland, including presence of inclusions which are invisible even geology, mining methods, processing, sorting and under a microscope. P. G. R. grading. Almost all the output is sold to Thai merchants skilled in heat treatment to improve COHEN, A.J. 1985. Amethyst colour in quartz, colour and remove silk. Blues and yellows pre­ the result of radiation protection involving iron. dominate, while pinks, purple and mauve stones American Mineralogist, 70, 1180-5, 3 figs. are rare. Colour zoning is common, often alternating Fe3+ in interstitial positions in the growth loci blue and yellow. These two fields are showing signs of the major rhombohedron in quartz crystals will of exhaustion, but the vast area of basalts in eastern prevent the development of smokiness if the Australia probably hides other potential mining amount of Fe is larger than the Al3+ impurity areas of considerable significance. R. K. M. content. The Al impurity is responsible for the smoky colour through the operation of a trapped DONTENVILLE, S., CALAS, G., CERVELLE, hole centre when ionizing radiation is used. Growth B. 1985. Etude spectroscopique des turquoises loci of the minor rhombohedra may be smoky even naturelles et traitees. (Spectroscopic study of 3+ when there is an excess of substitutional Fe over natural and treated turquoise.) Revue de Gem- 3+ 3+ 4+ Al . When interstitial Fe is oxidized to Fe an mologie, 85, 8-10, 6 figs. First part. electron becomes available for quenching the Spectra for natural turquoise from the United trapped hole centres on oxygens adjoining substitu­ States, plastic impregnated turquoise with added 3+ tional Al sites as they form. In these circumstances colour, plastic-impregnated turquoise with no 126 J. Gemm., 1986, 20, 2 added colour, Gilson synthetic turquoise and GUBELIN, E. 1985. La identification de los 'turquoise morte' (material whose colour has been nuevos zafiros sinteticos y tratados. (Identification lost through exposure to sunlight) are described and of the new synthetic and heat-treated sapphires.) illustrated. M.O'D. Gemologia, 22, 65/66, 5-34, 49 figs (44 in colour). FRUITMAN, C. 1985. The ultima cut. Lapidary Translation into Spanish of a paper first published J., 39, 8, 25-32, 9 figs (1 in colour). inj. Gemm., 1983, XVIII, 8,677-706. M.O'D. A cut designed to increase dispersion in a variety of coloured stones is described. Loss of weight is avoided as far as possible. M.O'D. HENN, U., SCHRAMM, M. 1985. Unter- FRYER, C.W. (Ed.), CROWNINGSHIELD, R., suchungen an braunen Turmalinen von Elahera, HURWITT, K.N., KANE, R.E. 1985. Gem Sri Lanka. (Investigation of brown tourmalines Trade Lab notes. Gems GemoL, XXI, 3, 171-7, from Elahera, Sri Lanka.) Z. Dt. Gemmol. Ges., 19 figs in colour. 34, 3/4, 98-100, 1 fig. in colour. Black star sapphire doublets and two corundums The brown tourmalines from Elahera were with surface-induced stars, one natural, the other a classified as uvites and dravites. Photomicrograph flux-grown synthetic, are described. A gambling shows rounded zircon crystals in a brown tour­ dice cut from an industrial diamond; strontium maline. E.S. titanate and cubic zirconia mistaken for diamonds, were totally destroyed by heat in repairs; an apparently new low grade synthetic emerald with considerable inclusions of parallel needles HOFER, S.C. 1985. Pink diamonds from Australia. (RI 1.555-1.560, SG 2.67); a green and white Gems GemoL, XXI, 3, 147-55, 12 figs in colour. carved bell with plagioclase and green muscovite Pink diamonds have been regarded as among the mica as major constituents; a demantoid cat's-eye rarest of the colour varieties and it is considered identified by its single refraction and absorption unusual to encounter actual parcels of natural pink spectrum; a fine jadeite with unidentified hair-like diamonds. But a surprisingly large number of these inclusions; another with a large white single jadeite stones have come in to the New York Gem Trade crystal as an inclusion; plastic imitations of lapis Lab this year, all originating from material pro­ lazuli and a purplish-pink faceted sapphirine are duced in the newly discovered Argyle deposits in all described and illustrated. R. K. M. NW Australia. Most stones are heavily included. 138 were examined in detail by this author. FRYER, C.W. (Ed.), CROWINGSHIELD, R., Colour was an unusual smoky purplish-pink, HURWITT, K.N., KANE, R.E. 1985. Gem deeper than most pink diamonds. Nuances of Trade Lab notes. Gems GemoL, XXI, 4, 232-8, brown and other colours were found. The spectrum 18 figs in colour. showed the Cape absorption line at 415 nm and the Reports on bi-colour aquamarine/goshenite; weak band at 520-580 nm, markedly different from diamond turned yellow-brown by heat of laser the spectra of known irradiated pinks. UV fluores­ sawing; diamond with internal natural radiation cence was blue but varied in strength. Colour is staining; and the composite (piggy-back) setting of thought to be due to plastic deformation of crystal two yellow diamonds. Off-colour yellow diamonds lattice and is unevenly distributed in the form of are being re-cut as modified octagonals to enhance 'brush stroke' grain lines throughout the stone, best the colour; and a cubic zirconia was similary cut. seen under low power magnification. 'Frosted' Garnet/glass doublet, mistaken for ruby, melted cleavage cracks and a pitted, sugary crystal surface under heat of repair work (low temperature soft seem to be characteristic of these Australian glass). A fine jet urn is illustrated. Lapis lazuli diamonds. It is thought that 'etching' is due to the beads had been oiled to improve colour. An crystal surfaces being dissolved by heat. [The interesting collection of rare pink conch 'pearls' author does not say whether the observed pitting described. A large collection of three-quarter blister was in reverse to the octahedral edge or parallel to it. pearls from Hong Kong were shown to be plastic. A In abstracter's experience the latter is always the pinkish-purple natural spinel had colour change to case when a diamond has been burnt.] Solid purplish-pink. Synthetic alexandritic type spinels inclusions had mostly assumed shapes which are accorded with the morphology of the diamond. It is rarely seen. Synthetic zincite described and illus­ considered that the features described would be trated. Another oddity was identified as the boiled sufficient to identify the provenance of these lens of a fish's eye. R.K.M. Australian pinks with fair certainity. R.K.M. J.Gemm.,1986,20,2 127

KANE, R.E., LIDDICOAT, R.T., Jun. 1985. another valuable final proof for such laboratories as The Biron hydro thermal synthetic emerald. have facilities to test for this. Gems Gemol.y XXI, 3, 156-70, 18 figs in colour. The manufacturer claims to be able to control the New hydrothermal synthetic emeralds grown in clarity and is concentrating on 'clean' material. Western Australia were subjected to careful gem- R.K.M. mological tests. Colour varied from green to slightly bluish-green with good saturation and high trans­ KOIVULA, J.I., MISIOROWSKI, E. 1985. Gem parency, often apparently free from inclusions. news. Gems Gemot., XXI, 3, 185-7, 1 fig. in Dichroism and absorption were as expected for colour. synthetic emeralds and fine natural stones. Red News of diamond mining in Australia, Botswana, transmission was observed under suitable lighting, Ghana, Namibia, Sierra Leone (three diamonds but this again is seen in some of the finer Colombian over 100 carats found) and United States (kimber- stones. A strong red was seen through the Chelsea lites under glacial deposits in northern Michigan are colour filter. being explored). SG varied slightly around 2.70 so that they A new amethyst area in Para, Brazil, is now overlapped the values for natural emeralds, confirm­ producing significantly. Aquamarine from the Jos ing these are hydro thermally produced stones. region of Nigeria continues to reach Idar-Oberstein. None of the stones examined exhibited any fluores­ Other supplies are coming from various African cence under either type of UV light. Iron was not localities and Brazil. Phantom quartz with 'ghost' found in these stones and the quenching in this outlines apparently due to green chlorite inclusions instance must be due to the high concentration of is being mined at Buenopolis in Minas Gerais. vanadium, which exceeded the chromium content Triangular growth markings on the basal by more than two to one. RIs of 1.569 and 1.573 pinacoids of a very thin Yogo Gulch, Montana, were obtained giving a birefringence figure of sapphire were in the expected reverse orientation 0.004-0.005, low values which suggest the synthetic and so close together as to give a perfect Star of origin, and rather more like those of a flux-grown David formation when viewed along the c axis. stone than a hydrothermal synthetic. R.K.M. The authors concentrate on inclusions, which are the identifying features in most synthetic emeralds. KOIVULA, J.I. 1985. Gem news. Gems GemoL, Healed fissures of the fingerprint and veil type are XXI, 4, 247-9, 2 figs in colour. typical, and often consist of two-phase inclusions of Reports on diamond mines in Shandong Province, bubble and liquid. Inclusions are by no means China; on high potential of Indian alluvial deposits; prolific, and careful illumination is often needed to and on UK Diamond Futures market which is bring out the tell-tale features. A variety of other mooted. Two rare 'pineapples' of opal, replacing inclusion forms is described and illustrated, glauberite crystals, found at White Cliffs. A new including nail-head spicules stemming from phen- Pakistan source of emerald at Sassi in the Haramosh akite crystals, or gold crystals which have come Mountains gives clean light-coloured stones. Alan from the lining of the steel autoclave, both proving Macnow reports that all cultured pearls are treated the synthetic origin of the stones. with mild oxidizing agent to prevent discoloration, Dark-field illumination shows growth irregulari­ some dyed pink or other colours. Smuggling of ties and 'flows' of colour which would not otherwise gems from Burma to Thailand continues. Kenyan be obvious. Some of these consisted of 'comet tails' rubies are sent to Bangkok for heat treatment to of minute white particles. White specks were clarify them. almost the only inclusions to be seen in the cleanest Pailin mines in Cambodia closed by military stones. A few stones showed what appeared to be activity, miners cross to similar deposits in Thailand. seed-plates. Sapphire-bearing regions in Fujian, China, are Chemically the presence of chlorine in these being explored. An aquamarine crystal from Yogo synthetics can be regarded as proof of synthesis. Gulch, Montana, had growth pattern on basal This element does not occur in flux-grown syn­ pinacoid forming a six-pointed 'Star of David'. thetics or in natural emeralds. R.K.M. The authors suggest that the characteristic inclusions and the low refractive indices and LIND, Th., SCHMETZER, K. 1985. Neue birefringence provide principal identifying clues to Untersuchungen an in Japan hergestellten these stones. Identification is not considered to be synthetischen Amethysten. (New investigations difficult provided the gemmologist is familiar with of the Japanese synthetic amethysts.) Z. Dt. the inclusions to be expected, and uses that Gemmol. Ges., 34, 3/4, 160-4, 6 figs in colour, knowledge to the full. The presence of chlorine is bibl. 128 J. Gemm., 1986, 20, 2

Synthetic Japanese amethysts are now available PIZANI, P.S., TERRILE, M.C., FARACH, in the gem trade. Certain diagnostic properties such H.A., POOLE, C.P. 1985. Color centers in as inclusions, growth structures, twinning and sodalite. American Mineralogist, 70, 1186-92, 9 infrared spectra are discussed. The gemstones figs. frequently have feathers consisting of liquid-filled Natural sodalite subjected to various radiation and two-phase inclusions, sharp growth zoning and heat treatments is studied with ESR, NMR, parallel to one rhombohedral face as well as twin optical absorption spectroscopy, ionic thermal structures, which can easily be distinguished from currents and electrical conductivity. It is proposed the polysynthetic lamellar twinning in natural that the colour centres which are involved in amethysts. E.S. coloration and bleaching are associated with inter­ stitial oxygen. M.O'D. MULLENMEISTER, H.J. 1985. Zirkon- Katzenauge aus Sir Lanka. (Zircon cat's-eye PONAHLO, J., KOROSCHETZ, T. 1985. from Sri Lanka.) Z. Dt. Gemmol. Ges., 34, 3/4. Quantitative Kathodolumineszenz - ein neues 165-6, 1 fig. in colour, bibl. Verfahren zur Unterscheidung echter von The stone described is a yellowish zircon cat's- synthetischen Smaragden und Rubinen. (Quanti­ eye with blue adularescence, cut as cabochon tative cathodoluminescence - a new method of weighing 5.52 ct with strong chatoyancy. It is from differentiating between natural and synthetic Sri Lanka and was originally offered as moonstone. emerald and ruby). Z. Dt. Gemmol. Ges., 34,3/4, SG 4.62. The chatoyancy is caused by layered 132-42, 9 figs (7 in colour), bibl. inclusions of needles; the nature of these inclusions Quantitative cathodoluminescence is the method was not determined. E.S. of microphotometric measuring of luminescence- intensities emitted during bombardment with fast NASSAU, K., HANSON, A.E. 1985. The pearl in travelling electrons (cathodorays). Natural rubies the chicken: pearl recipes in Papyrus Holmiensis. from Thailand show one tenth of CL intensities Gems Gemot., XXI, 4, 224-31, 7 figs, in colour. compared with synthetic rubies. E.S. Authors have found and tried ancient recipes for repolishing and/or cleaning pearls by feeding them to a chicken. Pearls remain in the bird's crop for an ROSENBERG, P.E., FOIT, F.F. 1985. Tour­ hour or so only and are then abstracted by killing maline solid solutions in the system MgO-Al203- the chicken. Some experiments failed, other suc­ Si02-B203-H20. American Mineralogist, 70, ceeded. [From the chicken's viewpoint they all 1217-23, 3 figs. failed miserably. ] R. K. M. A narrow range of tourmaline solid solutions in this system has been synthesized in the presence of NUBER, B., SCHMETZER, K. 1984. Struc­ excess silica, B203 and H20 in the temperature tural refinement of tsilaisite (manganese tour­ range 400-800°C at a pressure of 1 kbar. In nature maline). N. Jb. Miner. Mh., 7, 301^. tourmalines approaching the alkali-free composition The crystal structure of the Na-(Al,Mn,Li)- are rare, most not coming even close to it. The tourmaline tsilaisite was refined to a R-value of synthesis shows that the narrow range can exist and 2.9%. The structure is closely related to the crystal the principal substitutions are identified. M.O'D. structures of elbaite and schorl, and manganese was found to occupy exclusively Y sites in the tsilaisite structure. Author's abstract. B.N. ROTTLANDER, R.C.A. 1985. Der chemische Abbau des Bernsteins bei seiner Aufbewahrung an der Luft. (The chemical decomposition of O'DONOGHUE, M. 1985. Crystals as ornament. amber when exposed to air.) Z. Dt. Gemmol. Gems and Mineral Realm, 16, 4, 11-23. Ges., 34, 3/4, 143-51, 7 figs, bibl. An exhaustive outline of the progress of gemstone Amber is of interest to gemmologists as well as synthesis since the middle of the last century, with a archaeologists. It is known that when exposed to air bibliography. Author's abstract. M.O'D. and fight amber decomposes with an uptake of oxygen. This was quantitatively tested over 14 O'DONOGHUE, M. 1985. Pakistan. Gems and years, during that time solubility increased up to Mineral Realm, 16, 4, 35-7. 40% (among the soluble substances 65% terpenes). An account of the author's trip to Pakistan as It was calculated that there were about 25% resin adviser to the State Gem Corporation. The geology acids of the abietic acid type present as parent of the major gem deposits is outlined. substances. The infrared spectra reflect oxidation Author's abstract. M.O'D. of amber. E.S. J. Gemm., 1986, 20, 2 129

SCHMETZER, K. 1985. Distinction of natural to light in colour. Heating to 550°C changed colour and synthetic rubies by ultraviolet absorption to a citrine orange. R. K. M. spectroscopy - possibilities and limitations of the method. Z. Dt. GemmoL Ges., 34, 3/4, 101-29, SOLANS, J., DOMENECH, M.V. 1985. Los 45 figs, bibl. materiales gemologicos de Asturias. (Gemmo- The article discusses possibilities and limitations logical materials from Asturias.) Gemologia, 22, of UV absorption spectroscopy for the differentiation 65/66, 35-43, 3 figs. between natural and synthetic rubies. For deter­ Among the ornamental minerals found in the mination of rubies of unknown origin a direct Spanish province of Asturias are chiastolite, beryl, comparison of the spectra of unknown samples with fluorite, jasper, amber and quartz with some standard spectra of natural samples of known jet. M.O'D. origins and of synthetic samples of known producers is necessary. For a great number of unknown SOMAN, K., NAIR, N.G.K. 1985. Genesis of samples, UV spectroscopy gives unambiguous chrysoberyl in the pegmatites of southern Kerala, information about locality of natural or producer of India. Mineralogical Magazine, 49, 354, 733-8,2 synthetic rubies. It may also reduce possible figs. options regarding locality or producer. It does not Chrysoberyl had been found in association with provide definite information for determining each quartz in alkali feldspar in granitic pegmatites in possible unknown ruby, but it is helpful when southern Kerala, India. It is thought to crystallize combined with microscopy and trace element earlier than beryl and sillimanite. A model explained analysis. E.S. in detail in the paper may serve to explain the genesis of chrysoberyl in Sri Lanka. M.O'D. SCHMETZER, K., BANK, H. 1985. Gahnospinelle aus Sri Lanka. (Gahnospinel from Sri Lanka.) Z. STOCKTON, CM., MANSON, D.V. 1985. A Dt. GemmoL Ges., 34, 3/4, 92-7, 8 figs (1 in proposed new classification for gem-quality colour), bibl. garnets. Gems GemoL, XXI, 4, 205-18, 8 figs (4 The examined samples of zincian spinels in colour). (gahnospinels) from Sri Lanka were found to Published work by these authors suggests a represent intermediate members of the spinel- redefining of the garnet group into categories of gahnite series with minor components of hercynite. grossular, andradite, pyrope, pyrope-almandine, The investigations confirmed results published by almandine, almandine-spessartine, spessartine, Anderson in 1937. E.S. and pyrope-spessartine. Varietal categories (e.g. tsavorite, chrome pyrope, rhodolite and malaia) are SCHRADER, H.W. 1985. 'Dreiphaseneinschluss' defined. These suggestions are argued convincingly in einem Smaragd aus Siidafrika. (A three-phase and backed by gemmological data and electron- inclusion in an emerald from South Africa.) Z. probe chemical analyses. The result is a paper on Dt. GemmoL Ges., 34, 3/4,130-1,1 fig in colour. vexed questions of definition which must give An English version of this article was published grounds for further discussion. R.K.M. in J. Gemm., 1985, XIX, 6,484-5. E.S. ZEITNER, J.C. 1985. Facet a stone from home. SCHRADER, H.-W., HENN, U. 1985. Uber die Lapidary J., 39, 8, 42-51, 4 figs in colour. Problematik der Galliumgehalte als Hilfsmittel Describes some classic gemstones from North zur Unterscheidurig von naturlichen Edelsteinen American localities and gives brief information on and synthetischen Steinen. (About the problems the gemstone market. M. O'D. of using the gallium content to differentiate between natural and synthetic stones.) Z. Dt. ZEITNER, J.C. 1985. Merry Christmas gems. GemmoL Ges., 34. 3/4, 152-9, bibl. Lapidary J., 39, 9, 19-24, 4 figs in colour. An English version of this article appears on Describes red and green gemstones, including p. 108 above. E.S. alexandrite, iris agate, unakite, tourmaline, blood­ stone, ruby in zoisite and others. M.O'D. SHIGLEY, J.E., KOIVULA, J.I. 1985. Amethys­ tine chalcedony. Gems GemoL, XXI, 4,219-23,7 figs (6 in colour). A new amethystine chalcedony from Arizona, offered as 'damsonite', has normal constants for crypotocrystalline quartz, occurs in greyish, slightly reddish-purple, opaque masses varying from dark 130 J. Gemm., 1986, 20, 2

Book Reviews

BARDET, M.G. 1974. Geologie du diamant. the art of the goldsmith. The seventh in a series, it Deuxieme partie: gisements de diamant d'Afrique. contains several hundred entries giving short (Geology of diamonds. Second part: deposits of bibliographical details of each item but no descrip­ diamond in Africa.) BRGM, Paris. Pagination tion of the text. M.O'D. irregular. Illus. in black-and-white. Price on application. Forming Memoire No. 83 of the Bureau de FORTHUBER, W. 1978. Diamant, die hdrteste Recherches Geologiques et Mineres, this book Wahrung der Welt. (Diamond, the hardest cur­ discusses the diamond occurrences in Africa giving rency in the world.) Verlag Atelier Oehri, Vaduz, simplified geological maps of each of the major sites pp. 131. Illus. in black-and-white. Price on and covering the Kimberley area in some detail. application. Each of the major mines is discussed and its A pleasantly presented text on diamond with production and features described in tables. Each particular reference to diamond grading. Propor­ major area (South, West, East and Central Africa) is tions and clarity grading are illustrated as are a provided with its own bibliography. This is one of number of instruments. M.O'D. the few books on diamond to cover the geological and mineralogical aspects of its occurrence and is KALDIS, E. (Ed.). 1985. Current topics in materials essential for the mineralogist. M. O' D. science. Vol. 11. North-Holland Physics Publish­ ing, Amsterdam, pp. 453. Price on application. BERRY, F.J., VAUGHAN, D.J., (Eds.) 1985. Garnets grown as thin layers and as crystals Chemical bonding and spectroscopy in mineral grown from high temperature solutions are discussed chemistry. Chapman & Hall, London, pp. x, 325. in the first chapter of this valuable book. Details of £35.00. growth methods and the composition of melts are Chapters in this book are: quantum mechanical given. Special attention is paid to interfacial models and methods in mineralogy; X-ray spectro­ kinetics and to the correlation between growth scopy and chemical bonding in minerals; electronic kinetics and growth-induced magnetic anisotropy. spectra of minerals; mineralogical applications of Considerable detail on the growth of YAG, GGG luminescence techniques; Mossbauer spectroscopy and their analogues is given. The second chapter in mineral chemistry; electron spin resonance and deals with substrates for epitaxial garnet layers and nuclear magnetic resonance applied to minerals; discusses dislocations. spectroscopy and chemical bonding in the opaque minerals and mineral surfaces and the chemical The growth of iron borate, FeB03, is described bond. Almost all the chapters have something of in the third chapter and the growth and properties interest for the gemmologist but I would particularly of lanthanum hexaboride in the fourth and last recommend the one dealing with the electronic chapter. Readers are advised to consult this series spectra of minerals, since it contains a good deal of where it can be found (for example in the Science information on mineral coloration. Although this Reference Library). Details of crystal formation topic has long been prominent in the appropriate and growth appear here long before reaching journals it is here updated and presented lucidly mineralogical or gemmological texts. M.O'D. with a useful reference section (all the chapters have one). Luminescence techniques are also valuable KALDIS, E. (Ed.). 1985. Current topics in materials and the section on the opaque minerals should also science. Vol. 12. North-Holland Physics Publish­ be consulted when needed. M.O'D. ing, Amsterdam, pp. 483. Price on application. Four topics are covered by the latest volume in CONTENT, DJ. 1985. Glyptic arts - ancient this useful series. The first is metallic, ionic and jewelry: an annotated bibliography. Crow Hill, Van der Waals clusters, the second covers metastable Houlton, Maine 04730, USA. pp. 158. Price on phases in the bulk and on substrates, the third application. describes vapour pressure investigation of P-T-X This is the comprehensive catalogue of a book­ phase equilibria and non-stoichiometry in binary seller specializing in engraved gems, jewellery and systems. The final paper covers the mechanical J. Gemm., 1986, 20, 2 131 properties of brittle materials, with modern theories SANCHEZ CABELLO, A. 1978. El interes por las and experimental evidence. piedras preciosas. (Interest in precious stones.) Readers who wish to find out more about the Artes Graficas Vicent, Paterna, Valencia, pp. metastable phases of such materials as diamond will 167. Illus. in black-and-white and in colour. find the second paper of particular interest. R. Price on application. Kern of CNRS (France) makes the point that a A well illustrated book on diamond with some of metastable phase of a substance means that it is the major gemstones, probably written (from the quenched and transforms at so slow a rate that style and the date) for the prospective investor. The nobody sees any tendency to transform during a illustrations are of very variable quality, some being lifetime. Diamond, silica glass and amorphous excellent, others less so. There is a short biblio­ semiconductors are strongly metastable rather graphy. M.O'D. than unstable. The thesis is developed in the paper. M.O'D. TABURIAUX, J. 1985. Pearls, their origin, treat­ ment and identification. NAG Press, Ipswich, pp. 247. Illus. in black-and-white and in colour. KOSKOFF, D.E. 1981. The diamond world. £14.95. Harper & Row, New York. pp. viii, 356. Illus. in Translated from the French La perle-et ses secrets black-and-white. Price on application. this is one of the very few books to appear on pearl This covers very similar ground to Timothy in the past few years. The author is professionally Green's The world of diamonds (Weidenfeld & concerned with pearls and has visited a number of Nicolson, 1981) but is longer and more anecdotal. the more important areas of pearl recovery. The history of the stone from mine to piece of Much of the book is taken up by anecdotes, jewellery is well outlined with useful and interesting charming and instructive in themselves but still side-lights on aspects of the diamond trade, without the cited basis in fact that this type of book particularly that of New York. There are some very should provide. Since no references are given and welcome bibliographical notes and the whole book there is no bibliography, the reader has to take is conceived in a scholarly fashion. M.O'D. much on trust and with the lack of serious literature on pearl for so long, it is a pity that the publishers did not try to get a more solid book. The details on METZ, R. 1985. Antlitz edler Steine. (The faith of the different pearl fisheries are interesting but we precious stones.) Prisma Verlag, Guterslch. pp. have no way in which to establish their accuracy or 188. Illus. in colour. DM 39.00. topicality without citations. The author is scarcely This most beautifully illustrated book first came happier when describing the structure of pearls and out in 1964, but this is a new printing with greatly is clearly not at home with the scientific basis of enhanced colour reproduction. It is very competi­ pearl testing. Proof-reading by the publishers, if tively priced and can be highly recommended. It there was any, should have picked up the description gives a simple introduction to the science of of aragonite crystals as triclinic. In this section the minerals with notes on the crystal systems with choice and size of chapters is capricious to say the form and habit and valuable notes on how mineral least (if this were a stronger book and citations crystals are formed. Various types of formation are appropriate, such lack of arrangement would be a described, including Alpine clefts, pegmatites and major drawback to the abstracter. A set of hydrothermal deposits. All through the book questions, useful in conception, suffers because the appropriate full-page-sized colour photographs by answers are so terse that students (who have no Arnold E. Fanck accompany the text; particularly other book on which to draw) will take them as noteworthy for me are those of blue salt crystals gospel; readers looking at the description of orient, from the classic locality of Stassfurt and chalcanthite in which light is said to be 'distorted' will be from Coquimbo. excused for feeling apprehensive about the rest of The book ends with an exciting reproduction of the book. the yellow Tiffany diamond and with a bibliography. All this is a pity as the idea behind the book was Diagrams illustrating the basic symmetry of the good and the illustrations adequate (though some crystal systems are provided. Although in German appear to have been reproduced from xerox). The the text should present little difficulty and in any lack of bibliography completely vitiates the use of case the pictures are the main reason for buying the the book as a serious text though the general reader book. M.O'D. will find it interesting. M.O'D. 132 J. Gemm., 1986, 20, 2

Proceedings of the Gemmological Association of Great Britain and Association Notices

OBITUARY held, at which Mr J.I. Reynolds, F.G.A., and Miss Mr J.G. Shenton, F.G.A. (D.1934), Cheltenham, J.I. Platts, F.G.A., were re-elected Chairman and died on 30th September, 1985. Secretary respectively. Mr F.S.H. Tisdall, F.G.A. (D.1936 with Dis­ On 13th February, 1986, at Sheffield City tinction), Birmingham, died on 23rd January, Polytechnic, Mr David Wilkins, F.G.A., gave an 1986. illustrated talk entitled 'Rescued from the scrap box'. On 18th March, 1986, at Sheffield City Poly­ technic, Mrs M.S. Carson, Deputy Assay Master at GIFTS TO THE ASSOCIATION the Sheffield Assay Office, gave an illustrated talk The Council of the Association is indebted to the entitled 'The history and work of the Sheffield following for their gifts: Assay Office'. The talk was followed by a demon­ Mr John S. Burda, Unionville, Conn., USA, for a stration of the testing of gold, silver and platinum. piece of peridot and green Transvaal garnet. Mr R. Holt, London, for an oval emerald. COUNCIL MEETING At the meeting of the Council held on 22nd MEMBERS' MEETINGS January, 1986, at the Royal Automobile Club, 89 London Pall Mall, London S.W.I, the business transacted On 4th March, 1986, at the Flett Theatre, included the election of the following: Geological Museum, Exhibition Road, South Ken­ sington, London S.W.7, Prof. Pieter C. Zwaan, Fellowship F.G.A., gave an illustrated talk entitled 'Gemstones Allen, Vivien, Toronto, Ont., Canada. 1985 from the Kataragama area in Sri Lanka'. Bloodworth, Roy N., Wakefield. 1985 Georgopoulou Kyriaki, Marianna, Athens, Greece. Midlands Branch 1985 On 31st January, 1986, at Dr Johnson House, Halton, Elizabeth M., Huddersfield. 1985. Bull Street, Birmingham, Mrs H. Muller, M.Sc, Higham, Joyce R., Southport. 1973 F.G.A., gave a talk entitled 'Jet and its simulants'. Kittel, Gerhilde A., Toronto, Ont., Canada. 1985 On 28th February, 1986, at Dr Johnson House, Kothari, Rekha Y., Bombay, India. 1985 Mr Christopher Cavey, F.G.A., gave a talk entitled Kotila, Brian W., Don Mills, Ont., Canada. 1984 'Some historical aspects of gemstones'. Major, Christine B., St. Ives, NSW, Australia. 1985 North West Branch Pickrell, Rupert J., Turramurra, NSW, Australia. On 16th January, 1986, at Church House, 1985 Hanover Street, Liverpool 1, Dr G. Durant gave a Roser, Emilio Ruiz, Valencia, Spain. 1985 talked entitled 'Lapidaries, leechcraft and lore'. Tarn, Man Wai, Kowloon, Hong Kong. 1985 On 20th February, 1986, at Church House, Mr Rex Bingham gave a talk entided 'Gold prospecting'. Ordinary Membership Averbrook, Jeffrey I., Everett, Mass., USA. South Yorkshire and District Branch Chase, Moya, Hong Kong. On 24th January, 1986, at the Montgomery Clark, Berenice, Hobart, Tas., Australia. Hotel, Sheffield, the Annual General Meeting was Grange, Margaret D.J., Hong Kong. J. Gemm.,Gernm., 1986,1986,20,2 20, 2 133133

HulmHulm,, ValeriValeriee A.,A., HongHong Kong.Kong. McArthurMcArthur,, NiveNivenn R.R.,, Gore,Gore, NeNeww Zealand.Zealand. LetterLetterss ttoo thethe EditorEditor McCullochMcCulloch,, GeorginGeorginaa K.K.,, London.London. McSporran-Wirepa,McSporran-Wirepa, MargaretMargaret,, Gisborne,Gisborne, NeNeww Zealand.Zealand. FromFromJ.R.H. J.R.H. Chisholm, M.A., F.G.A.F.G.A. Manning,Manning, GeraldGerald E.,E., MiddletownMiddletown,, OhioOhio,, USA.USA. MeisterMeister,, AdrianAdrian,, ZollikonZollikon,, Switzerland.Switzerland. DearDear Sir,Sir, MoreauMoreau,, JeaJeann M.,M., ToulonToulon,, France.France. IInn hishis LetteLetterr toto thethe EditoEditorr (J.(J. Gemm., 1986,1986, RichRich,, Elizabeth,Elizabeth, London.London. 20(1)20(1),70-1), 70-1) DrDr CrowcrofCrowcroftt hadhad evidentlyevidently misunder­misunder­ Streit-Stalder,Streit-Stalder, MarthaMartha V.V.,, SaoSao Paulo,Paulo, Brazil.Brazil. stoodstood whawhatt I wrotwrotee inin reviewingreviewing thethe 4th4th editioeditionn ooff Sullivan,Sullivan, MaeveMaeve D.D.,, KowloonKowloon,, HonHongg Kong.Kong. Webster'sWebster's Gems asas indicatingindicating thathatt I believbelievee thatthat dede Trobec,Trobec, MartinMartin B.B.,, Calgary,Calgary, Alta.Alta.,, Canada.Canada. BoismenuBoismenu (and(and presumablpresumablyy HannayHannay tootoo)) hadhad succeededsucceeded inin makingmaking syntheticsynthetic diamondsdiamonds,, which,which, ooff course,course, I don'tdon't.. WhaWhatt I foundfound (and(and stillstill find)find) surprisingsurprising waswas thatthat,, aatt a timetime whewhenn Hannay'sHannay's (then(then EDUCATIONEDUCATION ADMINISTRATORADMINISTRATOR apparentlyapparently successful)successful) attemptattemptss toto makmakee diamondsdiamonds DESIGNATEDESIGNATE madmadee a considerablconsiderablee stir,stir, dede Boismenu'sBoismenu's attemptsattempts OOnn 10th10th FebruaryFebruary,, 1986,1986, MMrr DavidDavid EagleEagle joinejoinedd (then(then apparentlyapparently equallyequally successful)successful) appearedappeared toto ththee GemmologicalGemmological AssociatioAssociationn ofof GreatGreat BritainBritain andand havhavee passepassedd practicallpracticallyy unnoticedunnoticed.. IInn thethe lighlightt ooff ththee NationaNationall AssociatioAssociationn ofof GoldsmithsGoldsmiths toto taktakee upup subsequentsubsequent developmentdevelopmentss wewe alalll nownow knowknow thatthat ththee positionposition ooff EducatioEducationn AdministratoAdministratorr DesignateDesignate neitheneitherr Hannay'sHannay's nornor ddee Boismenu'Boismenu'ss attemptsattempts toto toto taktakee oveoverr responsibilitieresponsibilitiess forfor educatioeducationn andand makmakee diamonddiamondss werewere (or(or couldcould havehave beenbeen)) success­success­ trainingtraining oonn ththee retiremenretirementt ofof MMrr LesliLesliee Fitzgerald,Fitzgerald, ful.ful. F.G.AF.G.A.. I thinkthink thatthat inin consideringconsidering suchsuch a workwork asas FoForr twenttwentyy yearyearss MrMr EaglEaglee helheldd seniorsenior positionspositions Webster'sWebster's Gems DDrr CrowcroftCrowcroft shouldshould beabearr iinn mindmind witwithh ththee CharteredChartered AssociatioAssociationn ofof CertifiedCertified thethe readerreaderss forfor whomwhom iitt waswas writtewrittenn - mainlymainly AccountantsAccountants,, mainlmainlyy inin relationrelation ttoo theitheirr examina­examina­ membermemberss ooff thethe trade,trade, ttoo farfar totooo manmanyy ofof whomwhom tionstions,, andand waswas responsibleresponsible foforr thethe establishment,establishment, 'scientific''scientific' andand 'academic''academic' araree dirtydirty words.words. ThereThere developmendevelopmentt andand maintenancmaintenancee ooff aann accountancyaccountancy musmustt bbee a lotlot mormoree educationaleducational worworkk carriecarriedd outout diplomdiplomaa schemescheme forfor non-accountants.non-accountants. beforbeforee somesome membersmembers ofof thethe tradtradee araree readreadyy toto acceptaccept ththee rigourrigourss ofof scientificscientific method.method. TurningTurning ttoo somethingsomething quitquitee differentdifferent,, I feefeell thatthat apologieapologiess areare duduee botbothh toto thethe authorsauthors anandd ttoo theirtheir POOLPOOL OOFF SPEAKERSSPEAKERS readerreaderss foforr twotwo particularlyparticularly unfortunatunfortunatee piecepiecess ooff ThThee AssociationAssociation hashas formedformed a 'pool'pool ofof speakers'speakers' printingprinting inin ththee Journal ofof OctoberOctober last.last. (1)(1) TheThe frofromm gemmologistgemmologistss arounaroundd ththee worlworldd whwhoo havehave arrowsarrows indicatinindicatingg ththee positiopositionn ofof thethe 'hillock''hillock' inin indicateindicatedd theitheirr willingneswillingnesss toto traveltravel toto LondonLondon toto FiguresFigures 2 anandd 3 onon pagepage 665665 araree misplacedmisplaced (they(they hadhad givegive aann eveningevening presentationpresentation toto membersmembers ofof thethe beebeenn correctlcorrectlyy shownshown oonn ththee originalsoriginals andand werewere Association.Association. againagain correctlycorrectly placeplacedd byby thethe authorauthor onon thethe final ThisThis poopooll containscontains a larglargee varietyvariety ooff speakersspeakers butbut colourcolour proof):proof): ttoo placplacee thethemm correctly,correctly, thethe arrowarrow atat thethe ProgrammeProgramme Secretary,Secretary, TonTonyy French,French, F.G.A.,isF.G.A., is ththee totopp ofof FigurFiguree 2 shouldshould bbee movemovedd 3.5m3.5mmm ttoo thethe keenkeen ttoo expandexpand itit.. WouldWould anyany gemmologistgemmologistss whowho left,left, withwith thethe arroarroww atat thethe sideside movemovedd uupp 7mm,7mm, andand havehave hadhad experienceexperience ooff speakingspeaking beforbeforee larglargee groupsgroups thethe arrowarrow atat thethe toptop ofof FigurFiguree 3 shouldshould bebe movedmoved ofof people,people, anandd woulwouldd likelike theitheirr namesnames includeincludedd inin 5.5mm5.5mm ttoo ththee rightright,, witwithh ththee arroarroww aatt ththee sideside thethe pool,pool, pleaspleasee contaccontactt ththee SecretarySecretary aatt SaintSaint movedmoved uupp 6mm.6mm. (2)(2) TheThe veryvery poorpoor qualityquality ofof thethe Dunstan'sDunstan's HousHousee givinggiving fullfull detaildetailss ofof theitheirr topic(topic(s s)) MapMap oonn pagepage 677,677, iinn whicwhichh thethe coastlincoastlinee togethertogether andand thethe timestimes ofof thethe yearyear whenwhen thetheyy wouldwould bebe withwith muchmuch otherother detaildetail hahass disappeared,disappeared, iiss mostmost availableavailable ttoo speak.speak. regrettable,regrettable, ththee authorauthor havinhavingg suppliedsupplied aann excel­excel- lentllentlyy cleaclearr colourecolouredd originaoriginall aass wellwell asas aann equallyequally cleaclearr black-and-whitblack-and-whitee copy.copy. THETHE JOURNALJOURNAL OOFF GEMMOLOGYGEMMOLOGY BACBACKK NUMBERSNUMBERS YoursYours etc.,etc., ThThee AssociatioAssociationn hahass a numbenumberr ooff back-datedback-dated JJ.R.H .R.H.. ChisholmChisholm issueissuess ofof the Journal forfor sale.sale. ForFor a completcompletee listlist ofof thosethose availablavailablee pleaseplease writwritee ttoo thethe GemmologicalGemmological 10th10th March,March, 19861986 AssociationAssociation,, SaintSaint Dunstan'sDunstan's House,House, CareCareyy Lane,Lane, ThThee AthenaeumAthenaeum,, LondonLondon,, S.W.I.S.W.I. LondonLondon EC2VEC2V 8AB8AB.. 131344 J.J. Gemm.,Gemm., 1986, 1986,20,2 20, 2

From Peter G. Read, C.Eng, M.l.E.E.,M.I.E.E., From Dr Erik G. LundbladLundblad M.I.E.R.E.,M.l.E.R.E., F.G.A.F.G.A. DeaDearr SirSir,, DeaDearr SirSir,, IInn hihiss articlarticlee ''AA notnotee oonn ththee historhistoryy ooff diamondiamondd (1) I refereferr ttoo PetePeterr Crowcroft'Crowcroft'ss recenrecentt letteletterr iinn ththee synthesis' (I),, DDrr NassaNassauu describedescribess whwhyy hhee anandd somsomee Journal}ournal(l)1} iinn whicwhichh hhee claimclaimss thertheree iiss ''aa reluctancreluctancee otheotherr authorauthorss ddoo nonott attributattributee ththee prioritpriorityy ooff bbyy traditionatraditionall gemmologistgemmologistss ttoo accepacceptt scientificscientific diamondiamondd synthesisynthesiss ttoo ASEASEAA iinn 19519533 anandd whwhyy thetheyy resultresultss whewhenn iitt doedoess nonott suisuitt them'.them'. ddoo nonott consideconsiderr ththee ASEA worworkk ttoo bbee a significantsignificant I aamm neitheneitherr ononee ooff ththee oldeolderr generatiogenerationn ooff stestepp iinn ththee progresprogresss towardtowardss a successfusuccessfull synthetisyntheticc traditionatraditionall gemmologistgemmologistss thathatt CrowcrofCrowcroftt implieimpliess iinn diamondiamondd industryindustry.. ThThee maimainn reasoreasonn iiss thathatt ASEASEAA hihiss letterletter,, nonorr ddoo I havhavee aann 'emotional'emotional'' attachmentattachment dididd nonott publispublishh aatt ththee timtimee claimeclaimedd ananyy descriptionsdescriptions ttoo ththee BeilbBeilbyy theortheoryy ooff polishingpolishing.. HoweverHowever,, aass witwithh ooff ththee technologtechnologyy ttoo permipermitt independenindependentt experiexperi­­ mmyy owownn disciplinediscipline,, I aamm reluctanreluctantt ttoo abandoabandonn ononee mentermenterss ttoo duplicatduplicatee ththee processprocess.. ThiThiss iiss truetrue.. theortheoryy beforbeforee aann alternativalternativee hahass beebeenn formulated.formulated. WWee aatt ASEASEAA madmadee nnoo publipublicc announcemenannouncementt iinn ThThee statemenstatementt iinn ththee CrowcrofCrowcroftt articlearticle(2)(2) thatthat 19531953,, mainlmainlyy becausbecausee wwee wantewantedd ttoo improvimprovee oonn ththee TherTheree iiss nnoo reasoreasonn ttoo believbelievee thathatt thesthesee mechanismsmechanisms sizsizee anandd qualitqualityy ooff ththee diamonddiamondss anandd alsalsoo ttoo gaigainn (relevan(relevantt ttoo ththee polishinpolishingg ooff glasglasss anandd metalmetal mormoree detailedetailedd knowledgknowledgee ooff ththee conditionconditionss ooff surfacessurfaces)) ddoo nonott alsalsoo applapplyy ttoo ththee polishinpolishingg ooff alalll diamondiamondd formationformation.. WWee alsalsoo hahadd evidencevidencee ttoo gemmologicagemmologicall material'material',, anandd ththee followinfollowingg commentcomment believbelievee thathatt nnoo otheotherr teamteamss werweree engageengagedd iinn thathatt 'i'itt stilstilll remainremainss foforr a comprehensivcomprehensivee theortheoryy ttoo synthesisynthesiss attemptattemptss anandd thathatt wwee thereforthereforee hahadd timtimee ttoo bbee puputt forwardforward'' ddoo nonott seeseemm ttoo mmee ttoo bbee googoodd waitwait.. TherTheree wwee werweree apparentlapparentlyy misled.misled. enougenoughh reasonreasonss ttoo disregardisregardd ththee BeilbBeilbyy theorytheory.. TheThe AlthougAlthoughh wwee recognizerecognizedd ththee scientifiscientificc valuvaluee ooff crucruxx ooff ththee argumenargumentt seemseemss ttoo liliee witwithh ththee conflicconflictt ooff ththee first diamondiamondd synthesisynthesiss wwee basicallbasicallyy consideredconsidered viewviewss oonn ththee confirmatorconfirmatoryy worworkk dondonee bbyy BowdenBowden ththee commerciacommerciall prospectprospectss ttoo bbee ooff greategreaterr importance.importance. iinn 19519544 anandd 19581958.. IndeedIndeed,, CrowcrofCrowcroftt himselhimselff seemsseems HoHoww coulcouldd wwee nonoww besbestt protecprotectt ouourr know-how?know-how? guiltguiltyy ooff ignorinignoringg factfactss whicwhichh ddoo nonott suitsuit hishis WWee arrivearrivedd aatt ththee conclusioconclusionn thathatt onlonlyy thethe argumenargumentt (NB(NB,, ththee absencabsencee undeunderr NomarskiNomarski equipmenequipmentt coulcouldd bbee patentepatentedd bubutt nonott ththee processprocess interferencinterferencee contrascontrastt microscopmicroscopyy ooff crystallographiccrystallographic duduee ttoo a numbenumberr ooff priopriorr publicationspublications.. TToo keekeepp ourour featurefeaturess oonn ththee polishepolishedd surfacesurfacess ooff non-diamondnon-diamond know-hoknow-howw iinn househouse,, ververyy tightightt securitsecurityy measuresmeasures gegemm materials).materials). werweree applieappliedd whilwhilee worworkk continuecontinuedd oonn ththee developdevelop­­ I alsoalso thinthinkk itit isis expectingexpecting ratheratherr tootoo muchmuch forfor thethe menmentt ooff suitablsuitablee productioproductionn facilities.facilities. averagaveragee gemmologisgemmologistt (wh(whoo isis usuallusuallyy a busybusy ItIt waswas tootoo latlatee toto changechange thisthis policypolicy,, whenwhen somesome practisingpractising jewellerjeweller)) ttoo 'searc'searchh ououtt ththee referencereference atat sevenseven yearsyears laterlater wwee realizerealizedd thathatt GEGE contrarycontrary ttoo ourour theitheirr nearesnearestt UniversitUniversityy librarylibrary'' inin ordeorderr ttoo convinceconvince expectationsexpectations,, hadhad filed a patenpatentt applicationapplication ofof thethe themselvethemselvess ofof thethe argumentargumentss iinn Crowcroft'Crowcroft'ss article.article. processprocess,, whicwhichh alsoalso wawass granted,granted, despitedespite heavyheavy VerVeryy fewfew gemmologistgemmologistss areare physicistsphysicists,, anandd iinn thethe oppositionopposition,, inin somesome importanimportantt countries.countries. relativelyrelatively newnew sciencescience ofof gemmologgemmologyy thetheyy havehave toto ThThee 19531953 synthesissynthesis was madmadee inin a complexcomplex relyrely onon well-reasonedwell-reasoned articlesarticles printedprinted inin thethe journalsjournals sphericalspherical high-pressurehigh-pressure apparatusapparatus usinusingg a thermitethermite ofof ththee variousvarious gemmologicalgemmological associationsassociations toto keepkeep mixturemixture forfor heatingheating thethe carbon-ironcarbon-iron matrix.matrix. DrDr themselvesthemselves informedinformed ofof newnew techniquestechniques andand theories.theories. NassaNassauu isis quitequite rightright inin describingdescribing thisthis procesprocesss asas MyMy callcall forfor experimentalexperimental evidenceevidence ofof thethe polishingpolishing beingbeing soso destructivedestructive toto thethe high-pressurehigh-pressure equipmentequipment processprocess inin gemstones is i stherefore therefore not no tunreasonable unreasonable in in thatthat itit waswas notnot worthworth pursuing.pursuing. ThermiteThermite waswas usedused thisthis context.context. WhenWhen a comprehensivecomprehensive theorytheory ofof notnot onlyonly forfor heatingheating butbut alsoalso basicallbasicallyy toto provideprovide a gemmologicalgemmological polishingpolishing isis eventuallyeventually proposed,proposed, I goodgood isostaticisostatic pressurepressure inin thethe veryvery largelarge high­high- 3 amam suresure thatthat despitedespite Crowcroft'sCrowcroft's pessimismpessimism itit willwill pressurepressure reactionreaction chamberchamber (800(800 cm3).). InIn laterlater runsruns bebe acceptedaccepted byby eveneven thethe olderolder generationgeneration ofof tradi­tradi­ thethe matrixmatrix waswas alsoalso heatedheated byby electricalelectrical means.means. tionaltional gemmologists.gemmologists. TheThe 'sphere''sphere' was patentedpatented butbut nevernever usedused inin production.production. AsAs earlyearly asas 19551955 a piston-and-cylinderpiston-and-cyfinder YoursYours etc.,etc., apparatusapparatus hadhad beenbeen developed.developed. AlthoughAlthough thethe 3 PeterPeter G.G. ReadRead reactionreaction chamberchamber waswas nownow muchmuch smallersmaller (5(5 cm3) thethe apparatusapparatus was moremore practicalpractical forfor developmentdevelopment 4th4th March,March, 19861986 work.work. A versionversion ofof thisthis apparatusapparatus developeddeveloped inin stepssteps 6868 ForestForest House,House, Russell-CotesRussell-Cotes Road,Road, Bournemouth,Bournemouth, waswas subsequentlysubsequently usedused inin thethe diamonddiamond production.production. Dorset.Dorset. TheThe confirmationconfirmation ofof thethe 19531953 synthesissynthesis andand somesome ofof thethe followingfollowing onesones werewere mademade atat thethe InstituteInstitute ofof (I)(1) J. Gemm., 1986,20,1986, 20, 1,70.1, 70. InorganicInorganic Chemistry,Chemistry, UniversityUniversity ofof Stockholm,Stockholm, (2)(2) J. Gemm., 1981,1981, XVII,XVII, 7,459.7, 459. underunder thethe supervisionsupervision ofof thethe latelate ProfessorProfessor ArneArne J. Gemm., 1986,1986,20,2 20, 2 135135

Olander,Olander, DeaDeann ofof ththee ChemicalChemical FacultFacultyy andand alsoalso a From Tony French, F.G.A.F.G.A. membermember ofof ththee RoyalRoyal SwedishSwedish AcademAcademyy ooff Sciences.Sciences. ProfessoProfessorr OlandeOlanderr was ththee onlonlyy independentindependent con­con­ DeaDearr Sir,Sir, sultantsultant thathatt hadhad hadhad a fullfull insightinsight ooff thethe workwork sincesince I amam pleasedpleased toto bebe ableable toto clarifyclarify a smallsmall doubtdoubt ththee 1940s.1940s. TheThe X-raX-rayy analyseanalysess werewere madmadee andand expresseexpressedd bbyy MrMr S.JS.J.A .A.. CurrieCurrie iinn ththee firstfirst editioeditionn ofof confirmedconfirmed bbyy twotwo ooff hishis assistants.assistants. HoweverHowever,, onlyonly youyourr superbsuperb newnew journaljournal,, regardingregarding ththee starstar ProfessoProfessorr OlandeOlanderr was informeinformedd aboutabout thethe origioriginn ofof diamonddiamond(l).(1). ththee diamonds.diamonds. AlanAlan FlemingFleming willedwilled hihiss personapersonall collectiocollectionn ooff ItIt isis notnot forfor mmee ttoo judgjudgee whawhatt influencinfluencee ouourr earlyearly gemsgems,, mineralmineralss anandd carvingscarvings toto ththee AucklandAuckland workwork hadhad onon thethe subsequentsubsequent developmendevelopmentt ooff MuseuMuseumm iinn NeNeww Zealand.Zealand. TheThe starstar diamonddiamond was diamondiamondd synthesis.synthesis. CommerciaCommerciall productionproduction startedstarted notnot,, howeverhowever,, parpartt ooff hishis collection.collection. iinn thethe earlearlyy 1960s1960s andand sincesince thenthen ththee planplantt hashas beenbeen AsAs ththee persopersonn responsiblresponsiblee toto hihiss executorexecutorss inin NewNew oneone ofof thethe world'sworld's leadingleading producersproducers ooff high-gradehigh-grade ZealanZealandd forfor thethe disposadisposall ofof hishis estatestatee inin thisthis country,country, industriaindustriall diamonddiamondss andand otherother sophisticatedsophisticated super­super- I knewknew AlanAlan wantedwanted thisthis crystalcrystal toto gogo toto a museum.museum. high-pressurehigh-pressure products.products. HavingHaving checkedchecked thathatt ththee crystacrystall was stillstill iinn hihiss NewNew IInn 19651965 a separateseparate companycompany was founded,founded, ZealandZealand stock,stock, I askedasked hihiss executorsexecutors whetherwhether theythey ScandiamantScandiamant ABAB,, jointljointlyy ownedowned bbyy ASEAASEA andand DeDe wouldwould agreeagree ttoo iitt beinbeingg addedadded toto hihiss collectiocollectionn inin Beers,Beers, andand inin 19751975 ththee operationoperationss werweree completelycompletely thethe Museum.Museum. TheTheyy havhavee sip.cesince writtenwritten toto meme takentaken overover bbyy DDee BeersBeers.. ASEAASEA hahass notnot beenbeen confirmingconfirming thatthat thisthis hahass beebeenn done.done. engagedengaged iinn diamondiamondd synthesissynthesis sincesince then,then, butbut I amam suresure AlanAlan wouldwould havehave beenbeen delighteddelighted toto whatevewhateverr historianshistorians mamayy saysay wewe werewere certainlycertainly knoknoww thathatt MMrr Currie'sCurrie's photograpphotographh ooff thithiss crystalcrystal involvedinvolved iinn 19531953.. adorneadornedd ththee covecoverr ooff ththee firstfirst editioeditionn ooff ththee newnew journaljournal.. YourYourss etc.,etc., ErikErik GG.. LundbaldLundbald YoursYours etc.,etc., VicVicee PresidentPresident,, ASEASEAA AABB TonTonyy FrenchFrench (former(former membermember ofof thethe diamondiamondd developmentdevelopment teamteam iinn 1953).1953). 10th10th FebruaryFebruary,, 1986.1986. 20t20thh February,February, 1986.1986. 8282 BrookleBrookleyy RoadRoad,, Brockenhurst,Brockenhurst, Hants.Hants. S04S04 ASEAASEA ABAB,, S-72S-7211 8833 VasterasVlisteras,, Sweden.Sweden. 7RA7RA..

(I)J,(1) J, Gemm., 1985,1985, XIX,XIX, 8,8, 660.660. (I)(1) J. Gemm., 20,20 , 1,1 ,52. 52 .

From Mrs E. Stern, F.G.A.F.G.A. From Dr A. Banerjee and Dip. Min.,Min., DearDear Sir,Sir, H.-W. Schrader, F.G.A.F.G.A. I readread withwith amazementamazement thethe articlearticle 'An'An unusualunusual starstar diamonddiamond'' (J. Gemm., 1986,20,1,52)1986, 20, 1, 52) iinn whichwhich DearDear Sir,Sir, S.JS.J.A .A.. CurrieCurrie statesstates thatthat thethe starstar diamondiamondd describeddescribed WWee areare concernedconcerned aatt thethe leslesss thathann objectivobjectivee stylestyle iiss thoughtthought toto bebe oneone ooff onlonlyy foufourr knowknownn specimens.specimens. ofof ththee letteletterr fromfrom G.G. BossharBosshartt anandd K.K. Schmetzer,Schmetzer, ItIt iiss quitequite truetrue thatthat ththee phenomenophenomenonn isis rare,rare, butbut I publishepublishedd inin ththee JanuarJanuaryy 19861986 numbenumberr ofof thisthis knowknow ofof a collectioncollection iinn GermanGermanyy belonginbelongingg ttoo DDrr U.U. Journal.JournaZO). AAss a responsresponsee ttoo ouourr papepaperr 'Spectro­'Spectro- Kurz-TescKurz-Teschh comprisincomprisingg 5656 stones,stones, totatotall weightweight photometriphotometricc measurementmeasurementss ooff facetefacetedd rubies'rubies,(2)(2) wewe 46.55ct;46.55ct; thethe smallestsmallest weighinweighingg 0.19ct,0.19ct, thethe largestlargest shouldshould havehave expecteexpectedd andand hopehopedd foforr a mormoree criticalcritical 2.14ct2.14ct.. TheyThey araree allall transparentransparentt withwith a slightslight oliveolive­- discussion.discussion. beigbeigee huehue (raincoat(raincoat colour)colour),, somesome lighterlighter,, somesome a IInn thethe articlearticless quotequotedd bbyy uuss (Schmetze(Schmetzerr andand littlelittle darker.darker. ThThee qualitqualityy ofof thethe starsstars alsalsoo variesvaries Bank,Bank, 1980(3)1980(3) anandd BosshartBosshart,, 1982(4»)1982(4)) ththee authorsauthors somewhat,somewhat, bubutt alalll showshow distincdistinctt asterism.asterism. AllAll thethe onlyonly describedescribe thathatt theythey havhavee investigatedinvestigated '154'154 stonesstones areare octahedra,octahedra, somesome withoutwithout 'points'.'points'. ItIt isis naturalnatural sapphiresapphire crystals'crystals' andand 'ninety-four'ninety-four rubies'rubies' presumedpresumed thathatt ththee originorigin iiss Venezuela.Venezuela. respectively.respectively. NNoo specificspecific informatioinformationn wawass givegivenn thatthat theythey usedused facetefacetedd gemstones.gemstones. ThereforThereforee wewe wrote:wrote: YourYourss etc.,etc., 'a'ass mosmostt ooff ththee spectralspectral measurementmeasurementss areare carriedcarried EvelyneEvelyne SternStern outout oonn thinthin polishedpolished plateletsplatelets,, ththee resultsresults achievedachieved cannotcannot bbee easileasilyy reproducedreproduced iinn ththee casecase ooff facetedfaceted 3rd3rd March,March, 1986.1986. gemstones'.gemstones'. WWee trietriedd ttoo introduceintroduce a generalgeneral 9900 CarltoCarltonn AvenuAvenuee East,East, WembleWembleyy ParkPark,, Middlesex,Middlesex, additionaladditional technique.technique. ItIt wawass neitheneitherr ouourr intentiointentionn toto HA98LY.HA9 8LY. describedescribe hohoww ttoo solvesolve minominorr problemproblemss oonn orientationorientation 136136 J. Gemm., 1986,1986,20,2 20, 2

oorr polarizatiopolarizationn ooff ththee samplessamples,, nonorr ttoo finfindd a methodmethod From Mr D.J.D.]. Callaghan, F.G.A.F.G.A. ooff disctinctiodisctinctionn betweebetweenn naturanaturall anandd syntheticsynthetic Gemmological Association of Great BritainBritain rubiesrubies.. WWee recognizrecognizee ththee 'disadvantages''disadvantages' ofof methylenemethylene DearDear Sir,Sir, iodidiodidee anandd woulwouldd refereferr MMrr BossharBosshartt anandd DrDr THTHEE BASIBASILL ANDERSOANDERSONN SPECTROPHOTOMETESPECfROPHOTOMETERR APPEALApPEAL.. SchmetzerSchmetzer ttoo ththee GemsGems anandd GemologGemologyy abstract(S)abstract(5) I amam happyhappy toto adviseadvise yoyouu thatthat thethe targettarget figure ofof wherwheree CMC.M.. StocktonStockton commentcommentss 'As'As thethe authorsauthors £25,00£25,0000 foforr ththee SpectrophotometerSpectrophotometer AppeaAppeall launchedlaunched poinpointt outout,, methylenmethylenee iodidiodidee absorbabsorbss virtuallvirtuallyy alalll iinn ththee namnamee ooff ththee latlatee BasiBasill AndersoAndersonn iinn NovemberNovember lighlightt belobeloww abouaboutt 440nm440nm,, bubutt ververyy cleanclean spectralspectral 1984,1984, hahass nonoww beebeenn achievedachieved.. I shallshall bbee gratefugratefull iiff diagramdiagramss araree obtaineobtainedd anandd illustratedillustrated forfor ththee resrestt ooff yoyouu wilwilll allowallow mmee ttoo expressexpress mmyy thankthankss onon behalbehalff ooff ththee visiblvisiblee rangerange.. Thus,Thus, ththee immersioimmersionn methomethodd iiss ththee CounciCouncill ooff ththee GemmologicaGemmologicall AssociatioAssociationn ooff shownshown ttoo havhavee distinctdistinct advantages'.advantages'. GreatGreat BritainBritain toto allall thosthosee peoplpeoplee throughouthroughoutt thethe WWee wiswishh ttoo expressexpress thankthankss ttoo ththee EditorEditor ooff thethe worlworldd whwhoo havhavee contributecontributedd ttoo thethe Appeal.Appeal. Journal of Gemmology foforr allowinallowingg uuss spacspacee toto A supplementarsupplementaryy listlist toto thatthat issueissuedd iinJ.n J. Gemm.;,Gemm., publispublishh ouourr ideas.ideas. XIX(8)XIX(8),, 739-42739-42,, isis beinbeingg compiled,compiled, andand I woulwouldd bebe pleasepleasedd ifif itit couldcould bbee publishepublishedd inin a futurfuturee issuissuee ooff YourYourss etc.,etc., ththee Journal.Journal. AruArunn BanerjeeBanerjee Hans-WernerHans-Werner SchraderSchrader YourYourss etc.,etc., D.JD. J.. CallaghanCallaghan 20t20thh FebruaryFebruary,, 19861986.. ChairmanChairman.. InstituInstitutt fufUrr Edelsteinforschung,Edelsteinforschung, InstitutInstitut fiirfur GeowissenschaftenGeowissenschaften,, JohanneJohanness Gutenburg-Univer­Gutenburg-Univer- 19th19th MarchMarch,, 19861986.. sitatsitat,, MainzMainz,, WesWestt Germany.Germany. London.London.

(1(1)) J.J. Gemm., 1986,20,7,1986,20,7,71 7l. . (2(2)) J. Gemm., 1985,1985, XIXXIX,, 66,, 489-93.489-93. CORRIGENDUCORRIGENDUMM (3(3)) Neues Jahrbuch furfiir Mineralogie,Mineralogie, 139,139, 2,2, 216-25.216-25. (4(4)) J. Gemm., XVIIIXVIII,, 22,, 145-60145--<>0.. IInn J. Gemm., 2020,, 1,1, p.35p.35,, ththee radiographradiographss forfor (5(5)) Gems Gemol.,GemoL, 1985,1985, XXIXXI,, 33,, 182182.. FiguresFigures 1 anandd 2 werweree transposed.transposed. GEMMOLOGICAL ASSOCIATION OF GREAT BRITAIN

The Arms and Crest of the 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 escarbuncle, 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 escarbuncle 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 Educa rion Commi nee of the National Gemmological Association of Hong Kong, the Association of Goldsmiths and reconstituted Gemmological Association of Sou th Africa in 1931 as the Gemmological Association . Its and the Singapore Gemologist Society. name was extended to Gemmological TheJournal ofGemmology was first Association of Grea t Bri tain in 1938, and pu blished by the Association in 1947. I t 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 Mem bers of the Association. no. 433063). Opinions expressed by authors arc not Affiliated Associations are the necessarily endorsed by the Association. Gemmological Association of Australia, the

Notes for Contributors The Edi tors are glad to consider original is consistent with dear indication of the articles shedding new light on subjects of con ten t of the paper. I t should be followed by gemmological interest for publication in the the names (with ini tials) of the au thors and by Journal. Articles are not normally accepted their addresses. A short abstract of 50-100 which have already been published 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 tha t (I) full information as 10 000 words (unless capa ble of division into to any previous publication (whether in parts or of exceptional importance) are 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 pu blication. elsewhere withou t the consent of the Editors. Twenty five copies of individual papers are Papers should be submitted in duplicate on provided on reques t 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 Volume 20 No. 2 April 1986

1 lK Journal of Gemmology

Contents

New developments in spectroscopic methods for detecting artificially coloured diamonds G. $. Woods and A. T. Collins 75

Green aventurine quartz: mineralogical characterization E.A.Monroe 83

Locating gem deposits by computer M. O'Donoghue 87

A description of the jasper found at the

Orinduik Falls in Guyana, South America J. G. Gosling 91

Notes from the Laboratory -6 K. Scarratt 93

An unusual needle-like inclusion in gem sinhalite from Elahera, Sri Lanka M. Gunawardene andM. Gunawardene 98 Gem hornblende from Baffin Island, NWT, Canada W. Wight 100 On the problems of using the gallium content as a means of distinction between natural and synthetic gemstones H.-W. Schraderand U. Henn 108

Possibilities and limitations in radiographic determination of pearls L Lorenz and K. Schmelzer 114

Gemmological Abstracts 124 Hi -.y~ BookReviews 130 z: 2: \£ <_> Proceedings of the Gemmological Association and <£ Association Notices 132