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Volume 22 / No. 3 / 1990 Volume 22 No. 3. July 1990 The Journal of Gemmology GEMMOLOGICAL ASSOCIATION OF GREAT BRITAIN OFFICERS AND COUNCIL President: *Sir Frank Claringbull, Ph.D., F.Inst.P., FGS Vice-President: R. K. Mitchell, FGA Chairman: *D. J. Callaghan, FGA Vice-chairman: *N. W Deeks, FGA Honorary Treasurer: *N. B. Israel, FGA Members elected to Council: *A. J. Allnutt, M.Sc, J. W Harris, B.Sc, *J. B. Nelson, Ph.D., Ph.D., FGA M.Sc, Ph.D. FRMS, F.InstP, FGA C.R.Burch,B.Sc, J. A. W Hodgkinson, FGA W Nowak, CEng., FGS D. Inkersole, FGA FR.Ae.S., FGA *C R. Cavey, FGA B. Jackson, FGA M. J. O'Donoghue, P J. E. Daly, B.Sc, *E. A. Jobbins, B.Sc, CEng., MA, FGS, FGA FGA FIMM, FGA R.J. Peace, B.Sc, *A. E. Farn, FGA *G. H.Jones, B.Sc, Ph.D., CChem., FRSC, FGA A. J. French, FGA FGA *P G. Read, CEng., G. Green, FGA D. G. Kent, FGA MIEE, MIERE, FGA *R. R. Harding, B.Sc, D. M. Larcher, FBHI, FGA *K. Scarratt, FGA D.Phil, FGA A. D. Morgan, FIBF, FGA E. Stern, FGA *C H. Winter, FGA ^Members of the Executive Committee Branch Chairmen: Midlands Branch: D.M. Larcher, FBHI, FGA North-West Branch: W Franks, FGA Examiners: A. J. Allnutt, M.Sc, Ph.D., FGA D. G. Kent, FGA E. M. Bruton, FGA R Sadler, B.Sc, FGS, FGA A. E. Farn, FGA K. Scarratt, FGA R. R. Harding, B.Sc, D.Phil., FGA E. Stern, FGA E. A. Jobbins, B.Sc, C. Eng., FIMM, FGA M. Virkkunen, M.Phil., FGA G. H. Jones, B.Sc, Ph.D., FGA C. Woodward, B.Sc, FGA Editor: E. A. Jobbins, B.Sc, C.Eng., FIMM, FGA Editorial Assistant: Mary A. Burland Curator: C. R. Cavey, FGA 27 Greville Street, London EC1N 8SU Telephone: 071-404 3344 The Journal of Gemmology VOLUME 22 NUMBER THREE JULY 1990 Cover Picture The gemstone exhibition in the Geological Museum, London (now designated part of the Earth Sciences Galleries of the Natural History Museum). This comprehensive display is threatened with closure, and all readers are urged to take the opportunity to view it again before it is dismantled. The celebrated Mineral Gallery in the Natural History Museum is also scheduled to share the same fate. It is planned to combine the two exhibitions in a very considerably contracted area on one side of an upper gallery of the Geological Museum. Seel The case of the disappearing gemstones' on page 130. ISSN: 0022-1252 130 J. Gemm., 1990,22, 3 The case of the disappearing gemstones Many of our readers will be familiar with both the Museum. The drastically reduced area will inevit­ magnificent mineral and gemstone display in the ably mean that the vast majority of the collections Mineral Gallery of the Natural History Museum, will go into storage, never to be seen again. This will and the remarkable gemstone exhibition on the be made worse by the intention that the new ground floor of the Geological Museum (see front exhibition will be a 'theme' rather than a 'reference' cover illustration). display. This apparently means that only a very few These two displays together probably constitute items will be displayed, so that the least intelligent the world's finest reference display of gemstones visitor to the Museum will not get confused. and minerals, and attract visitors to London from all over the world. We understand that the 'management' of the We urge our readers to visit the current displays Museums (the Geological Museum was 'given' by before the Museums' management perpetrate what the British Geological Survey to the Natural His­ is likely to be the greatest jewel robbery ever tory Museum in April 1985) intend shortly to inflicted on the unsuspecting public who are, after combine these two displays onto part of one side of all, the actual owners of the National Museums and one of the upper galleries of the Geological their collections. STOP PRESS MURDER MOST FOUL STOP PRESS Since writing the above, we have learnt that the identify gemstones, including those in the Museum management, as part of its plan to perpe­ Museums' own magnificent collections. trate the jewel robbery, has literally killedgemmology Whilst by no means ameliorating the current within the Museums. situation, it is worth mentioning here that the Gem The Director, Dr Neil Chalmers, has announced Testing Laboratory of Great Britain (the oldest such a new corporate plan. This involves a major reduc­ laboratory in the world) is ready and able to provide tion in the scientific staff, and the complete with­ any gemmological testing services previously sup­ drawal from several scientific areas, including all plied by the Museums. gemstone related services and research. The post of It is hoped that the Laboratory will, later this Curator of Gemstones is to be abolished. The posts year, merge with the Gemmological Association of of the only other qualified gemmologists (two in Great Britain (the world's oldest gemmological 'exhibition design') are also to be axed. association), ensuring that the United Kingdom This means that there will soon be nobody retains at least one strong gemmological organiza­ employed by the Museums who will be qualified to tion. © Copyright the Gemmological Association ISSN: 0022-1252 JJ.. Gemm.Gemm.,, 1990,22,31990,22, 3 131131 A blackblack jadjadee dilemmadilemma John I. Koivula, C. W. Fryer, Robert E. Kane and Robert C. KammerlingKammerling GemologicalGemological InstituteInstitute ofof America,America, California,California, USAUSA AbstracAbstractt noted.noted. TheThe smallersmaller ovaloval cabochoncabochon andand thethe twotwo ThreeThree ofof fourfour opaqueopaque blacblackk gemgemss beingbeing representedrepresented inin rectangularectangularr tabletable cutscuts (Figure(Figure 1)1) possessepossessedd a goodgood thethe tradtradee asas thethe pyroxenpyroxenee jadeitjadeitee werewere identifiedidentified bbyy polispolishh withwith a vitreousvitreous lustre.lustre. TheyThey alsoalso appearedappeared toto X-ray diffraction as rocks containing a major componentcompo­ bebe mottledmottled withwith tinytiny whitishwhitish spotsspots thatthat stoodstood outout nent ofof amphibole,amphibole, probablprobablyy kaersutitekaersutite.. TheThe fourthfourth stonestone showedshowed thethe diffractiondiffraction patternpattern forfor jadeitejadeite.. SincSincee againstagainst thethe blacblackk background.background. AlthoughAlthough thethe largerlarger thethe basibasicc gemmologicalgemmological propertiepropertiess ofof somesome amphibolesamphiboles ovaloval cabochoncabochon (Figure(Figure 1)1) alsoalso hadhad a goodgood toto veryvery like kaersutitekaersutite overlapoverlap those those of of jadeite, jadeite, routine routine gemmo­ gemmologicalgoodgood polishpolish witwithh a vitreousvitreous lustre,lustre, itit lackedlacked thethe tinytiny logical testingtesting cannotcannot separateseparate thethe two.two. MoreMore advancedadvanced whitiswhitishh spotsspots andand hahadd a veryvery darkdark greygrey,, ratheratherr thanthan testing techniques,techniques, suchsuch asas X-ray diffraction and chemicalche­ blackblack, , bodbodyy colourcolour whenwhen viewedviewed withwith strongstrong fibre­fibre- micalanalysis, analysis, are areneeded needed to maketo make this this separation. separation. opticoptic incidentincident light.light. Refractive Index IntroductionIntroduction TheThe cabochonscabochons hadhad polishepolishedd basebasess whicwhichh mademade FourFour opaque,opaque, blacblackk stonesstones (Figure(Figure 1)1) werweree sub­sub­ themthem mucmuchh easiereasier toto testtest forfor refractiverefractive index.index. UsingUsing mittedmitted forfor identificationidentification toto thethe GIAGIA GemGem TradeTrade a GIAGIA GEMGEM InstrumentsInstruments DuplexDuplex IIII refractometerrefractometer Laboratory,Laboratory, Inc.Inc. ItIt was reportereportedd thatthat thesethese andand and,and, inin turn,turn, botbothh sodiumsodium vapourvapour andand whitewhite lightlight similarsimilar stonesstones werweree beinbeingg soldsold inin thethe tradetrade asas blackblack sources,sources, a refractiverefractive indexindex ofof 1.671.67 was obtainedobtained fromfrom jadeitjadeitee jadejade.. TheThe sourcesource ofof thesethese stonesstones waswas rere­­ a flat,flat, well-polishedwell-polished surfacesurface onon eacheach ofof thethe fourfour porteportedd toto bebe Guatemala;Guatemala; blackblack jadeitjadeitee isis knownknown toto stones.stones. NNoo birefringencebirefringence wawass notenotedd onon anyany ofof thethe comecome fromfrom GuatemalaGuatemala inin significantsignificant amountsamounts specimens.specimens. (David(David Hargett,Hargett, PersonalPersonal Communication).Communication). TheThe valuesvalues obtainedobtained forfor refractivrefractivee index,index, specificspecific Specific GravityGravity gravitygravity andand hardness,hardness, andand thethe lacklack ofof eithereither ultra­ultra­ SpecificSpecific gravitygravity was first estimatedestimated usinusingg thethe violeviolett luminescenceluminescence oror anan absorptionabsorption spectrum,spectrum, sink-floatsink-float method.method. BothBoth ofof thethe tabletable cutcut stonesstones aass indicatedindicated thatthat thethe stonesstones couldcould bbee jadeitjadeitee jadejade.. wellwell asas thethe largerlarger ovaloval cabochoncabochon sanksank ververyy slowlyslowly inin However,However, thethe veryvery naturnaturee ofof opaqueopaque blacblackk jade-likejade-like purpuree methylenmethylenee iodideiodide (specific(specific gravitgravityy 3.32),3.32), atat thethe materialsmaterials isis suchsuch thatthat theythey areare notnot conduciveconducive toto samesame ratratee asas a knowknownn jadeitjadeitee indicator.indicator. ThThee smallersmaller identificationidentification byby routineroutine gemmologicalgemmological
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