Volume 22 No. 8. October 1991 TheJournal of Gemmology THE GEMMOLOGICAL ASSOCIATION AND GEM TESTING LABORATORY OF GREAT BRITAIN OFFICERS AND COUNCIL Past Presidents: Sir Henry Miers, MA, D.Sc, FRS Sir William Bragg, OM, KBE, FRS ijjr. G.F. Herbert Smith, CBE, MA, D.Sc. Sir Lawrence Bragg, CH, OBE, MC, B.Sc, FRS Sir Frank Claringbull, Ph.D., F.Inst.P., FGS Vice-President: R. K. Mitchell, FGA Council of Management D.J. Callaghan, FGA N.W. Deeks, FGA N.B. Israel, FGA E.A. Jobbins, B.Sc, C.Eng., FIMM, FGA I. Thomson, FGA V.P. Watson, FGA K. Scarratt, FGA: Chief Executive R.R. Harding, B.Sc., D.Phil., FGA: Director of Gemmology Members' Council A. J. Allnutt, M.Sc, D. Inkersole, FGA PG. Read, C.Eng., Ph.D., FGA B. Jackson, FGA MIEE, MIERE, FGA C. R. Cavey, FGA G.H. Jones, B.Sc, Ph.D., FGA I. Roberts, FGA P. J. E. Daly, B.Sc, FGA H. Levy, M.Sc, BA, FGA E.A. Thomson, T. Davidson, FGA J. Kessler Hon. FGA R. Fuller, FGA G. Monnickendam R. Velden J.A.W. Hodgkinson, L. Music D. Warren FGA J.B. Nelson, Ph.D., FGS, CH. Winter, FGA F. Inst. P., C.Phys., FGA Branch Chairmen: Midlands Branch: D.M. Larcher, FBHI, FGA North-West Branch: W. Franks, FGA Examiners: A. J. Allnutt, M.Sc, Ph.D., FGA G. H. Jones, B.Sc, Ph.D., FGA L. Bartlett, B.Sc, M.Phil., FGA D. G. Kent, FGA E. M. Bruton, FGA P. Sadler, B.Sc, FGS, FGA C. R. Cavey, FGA K. Scarratt, FGA A.T. Collins, B.Sc, Ph.D E. Stern, FGA A. E. Farn, FGA Prof. I.Sunagawa,D.Sc R. R. Harding, B.Sc, D.Phil., FGA M. Virkkunen, M.Phil., FGA E. A. Jobbins, B.Sc, C. Eng., FIMM, 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 The Gemmological Association and Gem Testing Laboratory of Great Britain 27 Greville Street, London EON 8SU Telephone: 071-404 3334 Fax: 071-404 8843 ^Journal of Gemmology VOLUME 22 NUMBER EIGHT OCTOBER 1991 Cover Picture Cross section of ruby crystal with massive rutile inclusion. (Plate 5, 'The growth of rubies in south-east Kenya'by R.M. Key and J.O. Ochieng, p.484). ISSN: 0022-1252 458 J. Gemm., 1991,22,8 THE GEM DIAMOND DIPLOMA GAGTL have brought together the finest minds in the world of diamonds to produce the most comprehensive Gem Diamond home study course available. The course acknowledges the professionalism of the international diamond market and includes every aspect of gem diamond you will ever need to know. Following an examination in theoretical knowledge and practical application - including grading of polished and rough, you may gain the Gem Diamond Diploma and be entitled to the special Diamond Membership of GAGTL With DGA after your name your professionalism will be obvious for all to see For further information please contact Louise Macdougall on 071-404 3334, or complete the reply form below. Please complete and return to GAGTL Education Department, 27 Greville Street, London EC1N 8SU Name: Address: Telephone: JG 10/91 J.J. Gemm.,Gemm., 1991,22,81991, 22, 8 459459 AnAn unusualunusual assembledassembled inclusioninclusion specimenspecimen Robert C. Kammerling and John I. KoivulaKoivula GemologicalGemological InstituteInstitute ofof America,America, SantaSanta Monica,Monica, CaliforniaCalifornia 90404,90404, USAUSA Fig.Fig. I.1. ThisThis assembledassembled agateagate specimenspecimen weighsweighs 61.3961.39 caratscarats andand measuresmeasures 39.0039.00 x 30.4530.45 x 6.42mm.6.42mm. PhotograpPhotographh byby RobertRobert Weldon,Weldon, GemologicalGemological InstituteInstitute ofof America.America. AbstractAbstract Additionally,Additionally, featuresfeatures detecteddetected underunder magnifica­magnifica­ ThisThis articlearticle reportsreports onon anan assembledassembled stonestone consistingconsisting tiontion areare ofof concernconcern inin gemgem identification.identification. WithWith thethe ofof glassglass andand dendriticdendritic agateagate components.components. proliferationproliferation ofof newnew syntheticssynthetics andand thethe growinggrowing IntroductionIntroduction availabilityavailability ofof so-calledso-called 'sophisticated''sophisticated' man-mademan-made InclusionsInclusions areare anan importantimportant featurefeature inin gemstonesgemstones gems,gems, inclusioninclusionss areare usuallyusually thethe mosmostt reliablereliable -- forfor a numbernumber ofof reasonsreasons.. ForFor thethe diamonddiamond grader,grader, sometimessometimes thethe onlyonly - meansmeans ofof determiningdetermining thethe thethe presencepresence ofof a minuteminute inclusion,inclusion, jusjustt visiblevisible withwith naturenature ofof a gem.gem. NoNo longerlonger isis itit jusjustt a questionquestion ofof lOxlOx magnification,magnification, cancan setset thethe clarityclarity gradegrade andand naturalnatural vs.vs. VerneuilVerneuil syntheticsynthetic rubyruby.. TodayToday wewe faceface greatlygreatly affectaffect ththee stone'sstone's value.value. AlthoughAlthough oftenoften lessless thethe possibilitpossibilityy ofof havinghaving toto identifidentifyy fluxflux syntheticsynthetic closelyclosely scrutinizedscrutinized fromfrom anan evaluationevaluation standpoint,standpoint, rubies;rubies; fluxflux blueblue,, pinkpink andand orangeorange sapphires;sapphires; 'eye-visible''eye-visible' inclusioninclusionss cancan alsoalso havehave a significantsignificant syntheticsynthetic opalopal inin a varietyvariety ofof bodbodyy colourscolours andand effecteffect on·on thethe valuvaluee ofof a colouredcoloured stonestone (in(in thisthis patternspatterns ttoo theitheirr play-of-colour;play-of-colour; syntheticsynthetic alexan­alexan­ regard,regard, 'blemishes''blemishes' onon pearlspearls areare alsoalso anan importantimportant dritedrite andand eveneven cat's-eyecat's-eye alexandrite;alexandrite; andand thethe listlist goesgoes consideration).consideration). on.on. Furthermore,Furthermore, eveneven whenwhen wwee dodo determine,determine, forfor © CopyrightCopyright thethe GemmologicalGemmological AssociationAssociation ISSN:ISSN: 0022-12520022-1252 460 J. Gemm., 1991,22,8 example, that a ruby is natural, we may then have to substance (Nassau, 1983). Equally germane to this determine whether or not it has been heat-treated to discussion are 'most agate doublets'. These are modify colour and/or clarity, or had surface cavities produced by precipitating out manganese oxide filled with a glass to improve appearance and add dendrites within gelatine on a glass plate and then weight. gently heating to remove excess water; another glass Inclusions (and related structural features) are plate is then cemented on top and assembled stones also important in that they are responsible for some fashioned from the composite piece (Webster, of the most intriguing gems, those which display 1983). optical phenomena. Were it not for fine, parallel acicular crystal inclusions in chrysoberyl, there Description of specimen under investigation would be no cat's-eye stones; but for intersecting, In the spring of 1990, a resident gemmology oriented rutile 'needles' there would be no star student at the Gemological Institute of America in rubies and star sapphires. There would be no Santa Monica donated a most interesting assembled sunstone or aventurine feldspars had not minute stone for examination. The specimen, a very shal­ hematite or copper crystals precipitated out in these low-domed oval single cabochon (Figure 1), had gem materials. been purchased at the Tucson Gem and Mineral Show in February, where it was represented as a Altered inclusion specimens dendritic agate; there was no indication from the Occasionally we also come across gem materials vendor that the piece was assembled or in any other that have been treated with the apparent purpose of way altered. The stone, which weighs 61.39 carats fabricating or altering inclusions. Two such fabri­ and measures 39.00 x 30.45 x 6.42mm, is essential­ cated specimens the authors have examined were ly colourless and almost transparent where inclu­ colourless quartz crystals with man-made 'three- sions are not present. It exhibits an attractive phase' inclusions. Thin, tubular columns had been pattern of dark reddish to greenish brown dendrites drilled in from their bases and had been partially in the type of general pattern which in the US trade filled with a liquid. The final touch - 'phase three'- is referred to as 'plume' structure (Figure 2). One was a minute faceted gem; in one specimen this small, irregular area has a dark yellowish brown 'solid phase' was a blue gem, in the other, a bright colour with wavy, agate-like banding. red stone. Each stone had its base sealed with what When examined from the side, the assembled appeared to be a mixture of epoxy resin and quartz nature of the piece becomes obvious (Figure 3). The fragments (Koivula and Kammerling, 1989). top consists of a very transparent, colourless convex In 1986 the authors first saw faceted colourless as cap joined to a flat, light grey, semi-transparent to well as blue topaz containing brownish yellow translucent base. acicular inclusions. First described as 'rutilated' topaz, it was later shown that the inclusions were limonite-stained etched dislocation channels Magnification (Koivula, 1987). Late in 1988 one of the authors was When examined under magnification the cap shown similar material in which the inclusions were appears virtually inclusion-free. Between the cap a dark red-brown and which reportedly had been and base there is a fairly thick (approximately altered by heat treatment. Subsequent investigation 0.5mm) transparent, colourless layer containing showed that the heating