Volume 22 No. 7. July 1991 The Journal 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 Dr. 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

Members3 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 SEVEN JULY 1991

Cover Picture Plate 1 from Bauer's Edelsteinkunde published in German in 1896 (translated into English by L.J. Spencer in 1904 as Precious Stones). The specimens are diamond (1-4), ruby (5-6). sapphire (7-8). spinel(9-10) and zircon (11-13). (See Two types of historical traps: on 'Diamond Softening' and the'Antiquity of Emerald Oiling' by Kurt Nassau p.399-403.)

ISSN: 0022-1252 394 J. Gemm., 1991,22.

THE FIRST ANNUAL CONFERENCE OF THE GEMMOLOGICAL ASSOCIATION AND GEM TESTING LABORATORY OF GREAT BRITAIN

On the 3rd and 4th of November 1991 the Gemmological Association and Gem Testing Laboratory of Great Britain will hold its first Annual Conference in the delightful setting of the Tower Thistle Hotel - next to the Tower of London, Tower Bridge and St. Katherines Dock.

The Days will be filled with gemmological activity, lectures, videos and hands-on workshops. You will be invited to dine the evening away during what can only be described os the gemmological social event of the year.

The Conference will be crowned on the evening of the 4th with the Presentation of Awards Ceremony held at Goldsmiths' Hall where students from all over the World will be present to receive their Diplomas and Awards.

Be with us on the 3rd and 4th November, meet old friends but most of all come to enjoy the gemstones.

Pre-registration is required so do not delay! For further information please contact:

Mrs. Melanie Martin

Gemmological Association and Gem Testing Laboratory of Great Britain

• 27 GREVILLE STREET, (SAFFRON HILL ENTRANCE), LONDON EC1N 8SU •

Tel: (071) 404 3334 Fax:(071)404 8843

— A Conference sponsored by T.H. March & Co. Ltd. - Insurance Brokers to the Jewellery Industry — J. Gemm., 1991,22, 7 395

Two strongly pleochroic chatoyant gems Robert C. Kammerling and John I. Koivula

Gemological Institute of America, Santa Monica, California 90404, USA

Abstract gem itself, cat's-eye actinolite being a prime exam­ This article describes the gemmological features of ple. In such gems, the effect will only be seen when two rare, strongly pleochroic cat's-eye gems: iolite and the stone is cut en cabochon and oriented so that the tanzanite. planes of the acicular inclusions/structure are para­ llel to the base of the stone (Liddicoat, 1989). Chatoyancy is seen with varying frequency in a number of gem species. In addition to those Introduction mentioned above are apatite, enstatite, korneru- Gemstones exhibit a number of visual character­ pine, scapolite, sillimanite and zircon (Liddicoat, istics which are used by the trained gemmologist to 1989). Recently the authors have had the opportun­ identify them. These include such features as the ity to examine a number of unusual chatoyant gems. gem's colour, colour distribution, diaphaneity, bril­ Two of these in particular, cat's-eye iolites and a liance and lustre; virtually every gem can be cat's-eye tanzanite, are exceptional for both their described in terms of these factors which, in turn, great rarity and the fact that they are highly relate to their optical properties. pleochroic gems. In addition, a limited number of gems display additional unusual optical effects, which gemmo- logists refer to as optical 'phenomena'. One broad category of these includes a number of effects Cat's-eye iolites caused by the interference of light, such as opal's The gem material iolite, known to mineralogists play-of-colour, fire agate's iridescence, pearl's as cordierite, is usually fashioned into gems which orient, and labradorite feldspar's 'labradorescence' exhibit a blue to violet face-up body colour and no (or 'schiller') (Webster, 1983). optical phenomena. Some material from Sri Lanka Another general class of optical phenomena and India, however, contains small metallic magne­ results from reflections of light from internal struc­ tite, hematite and/or lepidocrocite platelets which tures or inclusions within the host gem. These produce a silvery (magnetite) or reddish (hematite/ include the glittery aventurescence or spangled lepidocrocite), glittery effect; as mentioned above, effect seen in such natural gems as aventurine material with reddish aventurescence has been quartz, sunstone feldspar and 'bloodshot' iolite, as called 'blood-shot' iolite. well as in the man-made 'goldstone' glass; the On two separate occasions recently the authors asterism or 'star effect' exhibited by some rubies, had the opportunity to examine iolite cabochons sapphires, garnets, rose quartzes and other gems; which exhibited distinct chatoyancy. The first and the chatoyancy or 'cat's-eye effect' exhibited by stone, a 23.65 carat gem, was shown to us at the 1990 several gems (Webster, 1983; Gubelin and Koivula, Tucson Gem and Mineral Show. The gem had a 1986). fairly light blue body colour, an overall 'cloudy' This last phenomenon, chatoyancy, is most often appearance, and exhibited a sharp chatoyant band caused by reflections of light from fine, parallel, (Koivula and Kammerling, 1990). This was the first elongated inclusions contained within the gem. such phenomenal iolite that either author had seen, These may be either solid, acicular crystals of such although apparently similar gems have been re­ minerals as rutile or goethite, as for example in some ported infrequently in the gemmological literature cat's-eye chrysoberyl or diopside, or they may be (see, for example, Brown et al, 1982; Fryer el al., hollow growth tubes as is the case of some cat's-eye 1982). tourmaline and beryl. Less commonly, chatoyancy The second stone, an attractive oval double results from a fine, parallel acicular structure of the cabochon weighing 8.25 carats and measuring 14.84

© Copyright the Gemmological Association ISSN: 0022-1252 396 J. Gemm., 1991,22,7

Fig. 3. Magnification reveals the cause of the chatoyancy in the cat's-eye iolite to be minute, whitish-appearing parallel fibres. Photomicrograph by John I. Koivula, Gemological Institute of America. Magnified 30x.

x 11.78 x 7.58 mm, reportedly originated in South India. The stone appears semi-transparent when viewed from above but would be almost transparent were it not for the fact that the base had been roughly ground. In surface-reflected incident light it exhibits an exceptionally strong chatoyant band; this is even quite evident under diffused overhead fluorescent lighting. When examined face-up it shows a light bluish-grey body colour on either side Fig. 1. When examined face-up, this 8.25 ct cat's-eye iolite of the chatoyant band (Figure 1) while the shows a light bluish-grey body colour on either side of periphery of the base shows a medium dark violet the sharp chatoyant band. Photo by Robert Weldon, colour due to the stone's strong pleochroism (Figure Gemological Institute of America. 2). Gemmological properties determined for the second stone were as follows: Refractive Index: 1.53, determined by the distant vision ('spot') method on the apex of the cabochon with a Duplex II refractometer and white light source. Optic Character: Biaxial, determined by resolution of an optical interference figure between crossed polaroids. During the polariscope examination the investigators noted that the chatoyant band appeared to bisect the 2V angle. Pleochroism: Very strong, in dark violet, light bluish-grey, and light brownish-yellow, as observed with a calcite dichroscope. Chelsea Filter reaction: Inert (appeared green). LWUV fluorescence: Inert; no phosphorescence. SWUV fluorescence: Inert; no phosphorescence. Absorption spectrum: No distinct features observed. Specific gravity: 2.60, estimated using the sink-float method with heavy liquids. ^«ag Magnification: Microscopic investigation revealed the cause of the chatoyancy to be minute, whitish- Fig. 2. When examined from the side, the cat's-eye iolite shown in Figure 1 appears a dark violet colour due to appearing parallel fibres (Figure 3). Also noted were strong pleochroism. Photo by Robert Weldon, Gemolo­ small, low-relief, colourless crystals of undeter­ gical Institute of America. mined identity. J. Gemm., 1991,22,7 397

Cat's-eye tanzanite Another chatoyant gem mentioned in the litera­ ture but very rarely seen is cat's-eye tanzanite. It thus came as a pleasant surprise when we were shown the stone pictured in Figure 4. This semi- transparent, high-domed oval cabochon with a slightly convex base weighs 2.69 carats and mea­ sures 8.21 x 6.81 x 5.51mm. When examined from above it exhibits an attractive medium dark greyish violet-blue body colour and a sharp chatoyant band. Gemmological properties determined for the chatoyant tanzanite were as follows: Refractive Index: 1.69, determined by the distant vision ('spot') method on the apex of the cabochon with white light source. Optic Character: Biaxial, determined by resolution of an optical interference figure between crossed polaroids. Fig. 4. This 2.69 ct tanzanite also exhibits distinct chatoyancy. Photo by Robert Weldon, Gemological Institute of Pleochroism: Very strong, in blue, purple and America. greyish green, as observed with a calcite dichro- scope. It was interesting to note that, as with the cat's-eye iolite described above, a deeper colour was noted when the stone was viewed down the sides in both the long (Figure 5) and narrow directions. Chelsea Filter reaction: Inert (appeared green) in most directions with a slight orangy overtone when viewed down the length of the cabochon. LWUVfluorescence: Inert; no phosphorescence. SWUV fluorescence: Inert; no phosphorescence. Absorption spectrum: No distinct features observed. Specific gravity: 3.38, estimated using the sink-float method with heavy liquids. Magnification: Microscopic investigation revealed the cause of the chatoyancy to be numerous parallel whitish channels running perpendicular to the 'eye' Fig. 5. As with the cat's-eye iolite, due to its strong pleochro­ (Figure 6). Spike-shaped 2-phase inclusions were ism the chatoyant tanzanite pictured here displayed a deeper colour when viewed down the sides. Note also also noted. When looking down the length of the the ends of the chatoyancy-causing parallel channels. channels a light transmission effect similar to that Photomicrograph by John I. Koivula, Gemological Insti­ shown by the mineral ulexite (so-called 'television tute of America. Magnified 25x. stone') was also noted.

Discussion and conclusion As is the case with cat's-eye alexandrite and some other strongly pleochroic chatoyant gems, orienting the iolite and tanzanite described herein so as to centre the chatoyant band across the dome of the cabochon resulted in less than the best face-up colour. It is also possible that light reflections off the chatoyancy-producing inclusions in these two gems 'whitened out' the true body colour and contributed to less than ideal colour appearance when viewed from above. This would be similar to the case of some silky Australian sapphires, in which masses of Fig. 6. Magnification shows the cause of the chatoyancy in the tanzanite to be numerous light reflecting parallel fine acicular inclusions reflect and scatter the two whitish channels running perpendicular to the 'eye'. polarized rays as they pass through the stone, Photomicrograph by John I., Koivula, Gemological Insti­ resulting in the blue and blue-green dichroic col- tute of America. Magnified 30x. 393988 JJ.. Gemm.Gemm.,, 1991,22,1991,22,77 ourourss merginmergingg intintoo ononee undesirablundesirablee greenisgreenishh blubluee ReferenceReferencess huehue.. ThThee effeceffectt iinn sucsuchh sapphiresapphiress mamayy bbee ssoo Coldham, T., T., 1985. 1985. Sapphires Sapphires from from Australia. Australia. Gems Gems &Gemology & Gemolo­, completcompletee thathatt ththee stonstonee appearappearss ththee samsamee iinn ananyy 21, 3,gy, 130-46. 21, 3, 130-46. direction of observation (Coldham, 1985). BrownBrown,, G.G.,, KellyKelly,, S.M.B.S.M.B.,, MainMain,, A.A.,, 19821982.. ExaminatioExaminationn ooff aa direction of observation (Coldham, 1985). Cat's-EyCat's-Eyee IoliteIolite.. The Australian GemmologistGemmologist,, 1414,10,264-65., 10, 264-65. FryerFryer,, C.W.C.w.,, CrowningshieldCrowningshield,, R.R.,, HurwitHurwit,, K.N.K.N.,, KaneKane,, R.E.R.E.,, AcknowledgementAcknowledgementss 19821982.. GeGemm TradTradee LaLabb NotesNotes:: IoliteIolite,, AAnn unusuaunusuall cat's-eyecat's-eye.. ThThee authorauthorss woulwouldd liklikee ttoo thankthank MrMr KimKim D.D. BarrBarr Gems & GemologyGemology,, 1818,, 33,, 171171.. GübelinGiibelin,, E.J.E.].,, KoivulaKoivula,, J.I.J.I.,, 19861986.. Photoatlas of InclusionsInclusions in ooff Inter-GemInter-Gemss iinn ShermanSherman,, TexasTexas,, foforr bringinbringingg ththee Gems. ABABCC editionedition,, Zurich.Zurich. 23.623.655 cctt cat's-eycat's-eyee iolitiolitee ttoo ouourr attentionattention;; MMrr YiannYiannii KoivulaKoivula,, J.I.J.I.,, KammerlingKammerling,, R.C.R.C.,, 19901990.. GeGemm NewsNews:: AttractiveAttractive MelasMelas,, aann instructoinstructorr aatt ththee GemologicaGemologicall InstitutInstitutee ooff Cat's-eyCat's-eyee IoliteIolite.. GemsGems& & GemologyGemology,, 2626,, 11,, 101101.. AmericAmericaa iinn SantSantaa MonicaMonica,, CaliforniaCalifornia,, whwhoo firstfirst LiddicoatLiddicoat,, R.T.R.T.,, 19891989.. Handbook of Gem Identification.Identification. 12t12thh brought to our attention the 8.25 ct chatoyant iolite editionedition,, 2n2ndd reviserevisedd printingprinting,, GemologicaGemologicall InstitutInstitutee ooff brought to our attention the 8.25 ct chatoyant iolite AmericaAmerica,, SantSantaa MonicaMonica.. anandd MMrr ManManuu NichanNichanii ooff Templ Templee TradinTradingg CompanCompanyy Webster, R.,R., 1983. 1983. Gems, Gems, Their Their Sources, Sources, Descriptions Descriptions and and Identification. Identi­ iinn EncinitasEncinitas,, CaliforniaCalifornia,, whwhoo subsequentlsubsequentlyy loaneloanedd 4th Editionfication. revised 4th Editionby B.W. Anderson,revised by Butterworth B. W. Anderson, Butter­ ththee stonstonee foforr gemmologicagemmologicall examinationexamination;; anandd PetePeterr & Co.worth (Publishers) & Co. (Publishers) Ltd., London. Ltd., London. and Bobbi Flusser of Overland Gems in Los and Bobbi Flusser of Overland Gems in Los [[ManuscriptManuscript received 5 5October October /990.] 1990. ] AngelesAngeles,, CaliforniaCalifornia,, foforr ththee loaloann ooff ththee cat's-eycat's-eyee tanzanitetanzanite.. J.J. Gemm.,Gemm., 1991,22,71991,22,7 399399

TwoTwo typestypes ofof historicalhistorical traps:traps: onon 'Diamond'Diamond Softening'Softening' andand thethe 'Antiquity'Antiquity of of EmeraldEmerald Oiling'Oiling' Kurt Nassau, Ph.D.Ph.D.

Lebanon,Lebanon, NJNJ 08833,08833, USUSAA

IntroductionIntroduction a stepstep whichwhich PlinyPliny andand laterlater recipesrecipes omit,omit, thethe stepstep ofof TheThe interpretationinterpretation ofof ancientancient textstexts isis alwaysalways a heatingheating thethe quartzquartz beforebefore droppingdropping itit intointo thethe hazardoushazardous undertaking.undertaking. ItIt isis easyeasy toto fallfall intointo twotwo liquid;liquid; forfor thethe wholewhole processprocess was intendedintended toto typestypes ofof traps:traps: scoffingscoffing atat apparentlyapparently ridiculousridiculous cracklecrackle thethe quartzquartz forfor subsequentsubsequent dyeing.dyeing. statementsstatements atat oneone extreme;extreme; acceptingaccepting apparentlyapparently ExerptsExerpts fromfrom a newnew translationtranslation (Nassau(Nassau andand reasonablereasonable statementsstatements atat faceface valuevalue withoutwithout carefulcareful Hansen,Hansen, unpublished)unpublished) ofof jusjustt threethree ooff ththee manymany analysisanalysis atat ththee otherother extreme.extreme. recipesrecipes inin ththee 'Papyrus'Papyrus GraecuGraecuss Holmiensis'Holmiensis' wilwilll AnAn exampleexample ofof thethe firstfirst typetype ofof trap,trap, onon whichwhich I illustrateillustrate ththee procesprocesss asas iitt was useusedd oveoverr twotwo waswas ableable toto shedshed somesome light,light, isis thethe 'softening'softening ofof thousandthousand yearyearss agoago:: diamond'diamond' withwith warmwarm goat'sgoat's bloodblood asas mentionedmentioned inin thethe 'Natural'Natural History'History' ofof PlinyPliny (Gaius(Gaius PliniusPlinius Secun­Secun- No.No. 2929.. MordantinMordantingg [or[or Softening]Softening] ooff Stones.Stones. dus,dus, RomanRoman historian,historian, 2323 ADAD toto 7979 AD).AD). A traptrap ofof thethe ...... hidhidee themthem [the[the stones]stones] iinn a drieddried fifigg oror [in][in] secondsecond typetype intointo whichwhich I myselfmyself fellfell previously,previously, isis plumpplump datesdates.. ThesThesee shoulshouldd bbee workeworkedd overover involvedinvolved withwith Pliny'sPliny's descriptiondescription ofof emeraldemerald oiling,oiling, charcoalcharcoal andand blowblownn witwithh bellowbellowss untiuntill thetheyy [the[the thethe apparentapparent antiquityantiquity ofof whichwhich isis sometimessometimes citedcited figfig oror datesdates]] burburnn andand becombecomee charred.charred. AnAndd taketake asas justificatiojustificationn forfor currentcurrent practice.practice. outout [the[the stones]stones] withwith tongtongss notnot witwithh youryour handhand [implying[implying thathatt thetheyy areare tootoo hohott ttoo touch]touch],, andand Pliny'sPliny's 'Diamond'Diamond Softening'Softening' thereuponthereupon plungplungee whilwhilee warmwarm intintoo ththee dyedye AAnn examplexamplee ofof ththee firstfirst typetype ooff tratrapp iiss Pliny'sPliny's solutionsolution anandd lelett coocooll therethere...... statementstatement onon diamonddiamond:: "Adama''Adamass ...... cancan bbee brokenbroken uupp bbyy goat'goat'ss bloodblood.. BuButt iitt musmustt bbee steepesteepedd inin bloodblood NoNo.. 3636.. SofteninSofteningg ooff Crystal.Crystal. thatthat iiss fresfreshh anandd stillstill warwarmm ... " (Eichholz(Eichholz,, 19621962,, ToTo softesoftenn crystacrystall taktakee goat'goat'ss bloodblood,, heaheatt thethe pp.. 209).209). IInn hihiss commentarcommentaryy oonn thisthis passagpassagee BalBalll crystacrystall oveoverr a gentlgentlee firfiree anandd didipp iitt iinn untiuntill iitt (1950,(1950, pp.. 252252)) callcallss thisthis a mythmyth anandd citecitess derivativederivative pleasepleasess youyou.. statementsstatements bbyy latelaterr writers.writers. ThesThesee frequentlfrequentlyy dede­­ scribescribe thisthis procesprocesss aass a techniqutechniquee foforr 'softening''softening' NoNo.. 4646.. DippinDippingg foforr LychniLychniss [[aa reredd stonestone,, diamondiamondd foforr easiereasier cutting,cutting, somsomee statinstatingg thathatt iitt diddid possiblpossiblyy tourmalintourmalinee oorr ruby].ruby]. nonott workwork,, witwithh otherotherss claiminclaimingg thathatt thetheyy hahadd useusedd itit BegiBeginn bbyy mordantinmordantingg [o[orr softeningsoftening]] aass aboveabove.. successfullysuccessfully!! TakeTake orchiorchill anandd alkanealkanett [bot[bothh reredd substances]substances] WheWhenn I originallyoriginally camecame acrosacrosss thithiss passagepassage,, I waswas anandd vinegarvinegar.. DroDropp ththee stonstonee intintoo thithiss untiuntill iitt greatlgreatlyy amusedamused,, jusjustt aass everyoneveryonee elseelse.. IItt wawass onlonlyy pleasepleasess youyou.. whilwhilee studyinstudyingg ththee eveevenn oldeolderr 'Papyru'Papyruss GraecusGraecus Holmiensis'Holmiensis;, aann EgyptiaEgyptiann manuscripmanuscriptt titletitledd BaphikaBaphika IInn 202000 BBeC anandd latelaterr ththee firsfirstt parpartt ooff thithiss two-stetwo-stepp (o(onn dyeingdyeing)) writtewrittenn bbyy BoloBoloss ooff MendeMendess abouaboutt 202000 procesprocesss was callecalledd 'mordanting'mordanting'' oorr 'softening'softening'' bbyy BBCC (e.g(e.g.. seseee NassaNassauu anandd HansenHansen,, 1985)1985) thathatt I analoganalogyy witwithh ththee 'softening'softening'' ooff woowooll bbyy a mordant­mordant­ realiserealisedd thithiss 'mythical'mythical'' reciprecipee actuallactuallyy worksworks!! ForFor iningg procesprocesss whicwhichh was iinn ususee frofromm ancienancientt timetimess ththee papyrupapyruss describedescribess iinn severaseverall reciperecipess iinn varyingvarying untiuntill quitquitee recentlrecentlyy ttoo makmakee ththee woowooll mormoree receptivreceptivee detailsdetails,, a procesprocesss whicwhichh iiss stilstilll iinn ususee todaytoday,, althoughalthough ttoo dyedyess (Nassau(Nassau,, "1984,1984, pppp."9. 9 anandd 158)158).. HoweverHowever;, iitt iiss givegivenn bbyy PlinPlinyy iinn a ratheratherr garblegarbledd form.form. classicistclassicistss preparinpreparingg ththee previoupreviouss translationtranslationss ooff thithiss ThiThiss procesprocesss applieappliess nonott ttoo diamondiamondd bubutt ttoo papyrupapyruss hahadd missemissedd ththee essentiaessentiall poinpointt frofromm nonott quartzquartz,, foforr ththee tertermm 'adamas'adamas'' thethenn includeincludedd botbothh knowinknowingg enougenoughh gemmologygemmology.. IItt requirerequiredd a neneww materialsmaterials.. IItt useusess goat'goat'ss bloobloodd - todatodayy wwee ususee waterwater translatiotranslationn involvininvolvingg mmyy interactiointeractionn witwithh ProfessorProfessor whicwhichh workworkss jusjustt aass wellwell!! AnAndd ththee papyrupapyruss includeincludess A.EA.E.. HanseHansenn ooff ththee ClassicClassicss DepartmenDepartmentt ooff PrincePrince-- 400 J. Gemm., 1991,22,7

Fig. 1. A page from Papyrus Graecus Holmiensis, the first gemstone treatment text, about 2000 years old, copied about 300 AD. J. Gemm., 1991, 22, 7 401 O PLIN0 • SECVNDI Ht%, , S'TORI AE M VN' 1 DI L1RRI TRI" 1 K T 5 .- m

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Fig. 2. Title page of 1548 edition of Natural History by Pliny, written in the first century AD, the first book containing extensive gemmological information. 402 J. Gemm., 1991,22,7 ton University to achieve understanding of the Ill: "Such stones [Median smaragdi], in spite of subtleties involved and this also resulted in an their varied colours, seem to be green by nature, understanding of Pliny's 'myth', which almost cer­ since they may be improved by being steeped in tainly was based on the papyrus recipe No. 36 cited oil" and footnote: "Pliny probably means that above. green seems to be the natural colour, because this colour is the one 'restored' by steeping the stones Pliny's 'Emerald Oiling' in oil" (Eichholz, 1962, p. 221). The routine oiling of emerald without disclosure is sometimes considered to be justified on the claim There is general agreement that Median smarag­ that it has been in use for at least two thousand dus is not emerald: it is either malachite (Eichholz, years. We are here speaking of the use of a colourless 1962, p. 220), turquoise or intergrown malachite oil to fill open cracks and fissures in emerald to and azurite (Ball, 1950, p. 144). If it is malachite, make these defects invisible or at least less obvious then a poor chalky grade could have its colour to the naked eye. The claimed antiquity of this improved by oiling. A much more likely candidate process is based on a passage in Pliny. I myself is turquoise, a material that does occur in 'varied accepted the conventional interpretation of this colours' - both blue and green - and can be readily source in one of my books (Nassau, 1984, pp. 7, changed from blue to the then-preferred green 100) and elsewhere, but have now investigated this colour by acid, acidic perspiration, and undoubted­ matter in detail, reaching a very different conclu­ ly by oil, especially if it is mixed with acid wine or is sion. acidic from rancidity. Here again, it is absolutely vital to establish If it means anything at all, Pliny's 'oiling of exactly what the words used meant. First of all, the smaragdus' can thus be interpreted as the turning word 'smaragdus' is stated by Pliny to include green by oiling of blue turquoise or of poor quality twelve varieties. These are now recognised to malachite! encompass not only emerald but also other green to Essentially all the occasional references to emer­ bluish-green materials such as green sapphire, ald oiling in the centuries that followed are clearly turquoise, malachite, amazonite, lapis lazuli, green based on the usual misinterpretation of Pliny's alabaster, green jasper, and so on (Eichholz, 1962, smaragdus oiling. As one example (King, 1860), the p.213; Ball, 1950, pp. 140 ff, 256 ff). Pliny himself Abbot Mar bod, writing in France about 1070 AD, states that all smaragdi except the Scythian, Egyp­ also cites twelve varieties of smaragdus, as did Pliny, tian, and Attic ones are found in copper mines. and again paraphrases Pliny: Eichholz (1962, p. 214) concludes that only the Scythian and Egyptian smaragdi of Pliny were true "If steeped in verdant oil or bathed in wine emeralds. It's deepened hues with perfect lustre shine." Another critically relevant fact is that green gemstones were preferred to blue ones at that time. There is also mention of the use of oil on As one example, Pliny says: "... of all colours, green gemstones in the much earlier papyrus discussed is the most pleasing to the eye" (Ball, 1950, p. 140). above, but there the oil is the medium that carries Again, Pliny states (Ball, 1950, p. 143) with respect dyes and pigments into crackled stones to produce to Persian smaragdus (probably turquoise): "... imitations. There seems to be no hint of the use of a they have this fault that they have the colour either colourless oil merely to hide defects. of gall or the sky... but are still not green". In summary, there are no convincing ancient With these two considerations in mind, let us reports of emerald oiling. This is not to say that examine what Pliny actually does say about the some may not have tried these instructions in the oiling of smaragdus in Chapter 18 of Book 37. Here conventionally misinterpreted form throughout the are the three authoritative translations of the pas­ centuries and obtained an improvement in appear­ sage: ance from the filling with oil of the cracks in the emerald. But we do not have any persuasive I: "Such smaragdi [of Media] as are not naturally documentary evidence of it. Therefore we cannot green may be improved and reach their full attribute the emerald oiling process to antiquity. beauty by being washed in wine and oil" (Ball, 1950, p. 144, based on Philemon Holland's Modern emerald oiling translation of 1601). When we examine more recent sources, such as II: "... [Median smaragdi] appear naturally of a the writings of the great gemmologists of the green colour, but become improved by the nineteenth and twentieth centuries, we find an even addition of oil" (Bostock and Riley, 1898, more surprising situation. None of these refers to p. 412). emerald oiling before the 1960s! This is most J. Gemm., 1991, 22, 7 403 astonishing in the case of Max Bauer, whose tially all green aquamarine to the currently more Precious Stones of 1904 is one of the most detailed desired blue colour (blue is rare for aquamarine as gemmological treatises ever written. In his text he mined). Here again there is no mention of this mentions many treatments, but for emerald only process in Bauer; Liddicoat first refers to it in 1981 green foil backings for pale stones and closed black in the eleventh edition of his Handbook of Gem settings for fissured stones. Equally astonishing is Identification; Anderson mentions it only in the the absence of emerald oiling in early editions of ninth edition of his Gem Testing in 1980; but a Webster's authoritative Gems, where only in the description does occur as early as 1962 in Webster's fourth edition of 1983 (Webster and Anderson, first edition of Gems. There is thus an earlier 1983) does an account finally appear. (The 'oiling' complete absence of mention of this process and with kerosene by Brazilians mentioned on p. 91 of subsequently only rarely a reference to it. It is Webster's third edition of 1975 is clearly not the usually accepted that the reason for this derives modern oiling process). There is also no mention of from the widespread use of aquamarine heating emerald oiling in early editions of Liddicoat's being known by all, with everyone recognizing it as Handbook of Gem Identification or Anderson's Gem obvious and indeed to be expected. Perhaps this Testing. type of explanation applies equally well to trade The first reference to modern emerald oiling that emerald oiling in the twentieth century. There is, of I have been able to locate is in Liddicoat's 6th course, one significant difference between these two edition (1962, p. 2 80), where it is referred to as a products: the colour of heat-treated aquamarine is 'longstanding' process. The process itself is out­ stable in normal use, but the oil in oiled emerald lined for the first time in an unsigned article in 1981 may dry out or be washed out by detergent. in the Retail Jeweller (Anon., 1981), soon followed by a detailed description by Ringsrud in 1983. I References should like to hear if any reader knows of earlier Anderson, B.W., Gem Testing, various edns., Butterworths, references to the modern oiling process which I London. have overlooked. (Anon) 1981. Secrets of Emerald Oiling. Retail Jeweller, 20, No. Unable to locate older convincing documentary 488, April 9, 1981, 2. Ball, S.H., 1950. A Roman Book on Precious Stones, Gemological mention of the modern oiling process, I finally Institute of America, Santa Monica. turned to the memory of the master gemmologists Bauer, M., 1904. Precious Stones. Reprinted 1968, Dover, New Richard T Liddicoat and Robert Crowningshield of York, Vol. 2, 310. the Gemological Institute of America, to both of Bostock, J., Riley, H.T., 1898. The Natural History of Pliny, Vol. 6, G. Bell, London. whom and their associates I am grateful for help. Eichholz, D.E., 1962. Pliny Natural History, Vol. 10, Harvard They also checked with several octogenarian University Press, Cambridge. sources accessible to them. The earliest any of these King, C.W., 1860. Antique Gems, J. Murray, London, p. 397. sources could definitely locate trade emerald oiling Liddicoat, R.T., Jr. Handbook of Gem Identification, various edns., Gemological Institute of America, Santa Monica. was about 1910. There was also some feeling, but Nassau, K., 1984. Gemstone Enhancement, Butterworths, certainly no proof, that trade emerald oiling may not London. have existed before 1910. Nassau, K., Hansen, A.E., 1985. The Pearl in the Chicken, Gems If we then assume that trade emerald oiling began and Gemology, 21, 224. Ringsrud, R., 1983. The Oil Treatment of Emeralds in Bogota, soon after the turn of the century, how to explain the Colombia, Gems and Gemology, 20, No. 3, pp. 149-56. 'conspiracy of silence' that existed among gemmo­ Webster, R., 1962, 1970, and 1975. Gems, edns. 1, 2, and 3, logists for some half a century, with but a minimal Newnes-Butterworths, London. mention over the next 30 years? An examination of Webster, R., Anderson B.W., 1983. Gems, 4th edn., Butterworths, London, p. 116. the aquamarine heating process may be relevant: this enhancement has been used to convert essen­ [Manuscript received 28 March 1991.] 404404 J.. GemmGemm..,, 11991991,, 2222,7, 7

STUDENT SPECIMENS We are pleased to offer an excellent range of student gemstone specimens to members. Amongst those on offer are these interesting natural emeralds from two localities, the USSR and Brazil

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AnomalousAnomalous behaviourbehaviour ofof certaincertain geudageuda corundumscorundums duringduring heatheat treatmenttreatment S.I. Perera, B.Sc.(Sri Lanka), M.Phil.(Hong Kort,,/>Kong), A.S. Pannila, B.Sc.(Sri Lanka),Lanka), MM.Phil.(Sri .Phil.(Sri Lanka), H.P.N.J.Gunasekera, BB.Sc.(Sri .Sc.(Sri Lanka), M.Sc.(Tohoku), and R.N.R.N. Ediriweera, B.Sc.(Ceylon), M,Sc.(London),M.Sc.(London), DIC, Ph.D.(London).Ph.D.(London).

CeylonCeylon InstituteInstitute ofof ScientificScientific andand IndustrialIndustrial Research,Research, PPOO BoBoxx 787,787, Colombo,Colombo, SriSri LankaLanka

AbstractAbstract ofof blubluee colourcolour.. NNoo changchangee wawass observedobserved inin typetype (c(c)) A geudageuda varietyvariety knownknown asas 'ottu''ottu' withwith darkdark blueblue stones.stones. ThisThis whitwhitee coatingcoating coulcouldd nonott bbee removedremoved patchespatches onon thethe outerouter surfacesurface whenwhen heatheat treatedtreated atat eveneven afterafter heatinheatingg aatt highehigherr temperaturestemperatures.. HenceHence anan (l800-1850)"C(1800-1850)°C underunder reducingreducing conditionsconditions producedproduced investigationinvestigation wawass initiateinitiatedd usinusingg ththee ElectroElectronn probeprobe threethree typestypes ofof samples.samples. TheyThey showedshowed (a)(a) goodgood blubluee micro-analysermicro-analyser (EPMA(EPMA)) toto studstudyy ththee causcausee ofof thesethese colourcolour andand clarityclarity (b)(b) insufficientinsufficient blueblue colourcolour butbut goodgood changes.changes. clarityclarity (c)(c) formationformation ofof a thickthick whitewhite precipitateprecipitate ('dead('dead milk')milk') onon thethe outerouter surface.surface. InIn orderorder toto understandunderstand thethe causecause ofof thesethese changeschanges EPMAEPMA resultsresults werewere studied.studied. TheThe results, whilewhile confirmingconfirming thatthat FeFe andand TiTi areare ExperimentalExperimental detailsdetails necessarynecessary forfor producingproducing a goodgood blubluee colour,colour, indicateindicate AroundAround 5500 stonestoness ofof thethe 'ottu''ottu' varietvarietyy alalll withwith thatthat thethe presencpresencee ofof otherother minorminor impuritiesimpurities hindershinders thisthis darkdark blueblue patchepatchess onon thethe outerouter surfacessurfaces werewere heatheat process. TheThe resultsresults alsoalso indicate indicate that that a ahigh high concentra· concentration treatedtreated iinn ththee temperaturetemperature rangerange 1800-18S0°C1800-1850°C forfor 1 tion ofof FeFe andand Ti,Ti, togethertogether withwith V andand somesome otherother impuritiesimpurities givesgives riserise toto thethe formationformation ofof thethe thickthick whitewhite hourhour underunder reducinreducingg conditionsconditions.. ThThee typetypess (a)(a),, (b)(b) precipitate onon thethe outerouter surfacesurface during during heat heat treatment. treatment. andand (c)(c) obtainedobtained afteafterr heaheatt treatmentreatmentt werweree selectedselected andand analysedanalysed usinusingg ththee EPMEPMAA (Schimadzu(Schimadzu - ModelModel 8705).8705). ThisThis isis a uniunitt witwithh multiplmultiplee wavelengthwavelength dispersivedispersive X-raX-rayy spectrometerspectrometerss (WDX)(WDX) toto enableenable IntroductionIntroduction elementselements frofromm 44BeBe ttoo 9292UU ttoo bbee detecteddetected.. ThThee 33 SriSri LankaLanka hashas a largelarge reservereserve ofof thethe lowlow qualityquality channelchannel spectrometerspectrometer wawass useusedd witwithh ththee spectralspectral gemgem varietyvariety calledcalled 'geuda~'geuda'. GeudaGeuda isis thethe termterm usedused toto crystalscrystals RAPRAp,, PETPET anandd LIELIE AcceleratingAccelerating voltagevoltage describedescribe thethe whitishwhitish oror palepale blueblue corundumcorundum ofof poorpoor andand specimenspecimen currentcurrent werweree setset aatt 15klskVV andand 0.00.055 /xp,AA colourcolour andand clarity.clarity. HeatingHeating atat temperaturestemperatures inin thethe respectivelyrespectively throughoutthroughout ththee analysis.analysis. ConstantConstant rangerange (l600-1900tC(1600-1900)°C couldcould transformtransform thesethese intointo beambeam widthwidth ooff lOOp,m100/mi wawass alwayalwayss employedemployed toto goodgood qualityquality blubluee sapphires.sapphires. DependingDepending onon thethe analyseanalyse ththee samples.samples. visualvisual character,character, termsterms suchsuch asas blueblue geuda,geuda, dieseldiesel TheThe samplessamples werweree scannescannedd aatt a ververyy loloww scanningscanning geuda,geuda, silkysilky geuda,geuda, ottuottu etc.etc. areare usedused inin thethe tradetrade toto speedspeed ofof O.lA/miO.lA/minn toto carrcarryy ououtt qualitativequalitative identi­identi­ describedescribe differentdifferent varieties.varieties. ficationfication ooff thethe tractracee elements.elements. ExacExactt peapeakk positionspositions LightLight blueblue oror colourlesscolourless stonesstones withwith darkdark blueblue werewere searchedsearched foforr elementselements ofof interestinterest anandd cumula­cumula­ patchespatches onon outerouter surfacessurfaces - varietiesvarieties ofof 'ottu' -- whenwhen tivetive countscounts werewere recorderecordedd atat thethe peapeakk positionpositionss andand heatheat treatedtreated underunder reducingreducing conditionsconditions inin thethe backgroundbackground foforr 1010 secondsecond intervals.intervals. temperaturetemperature rangerange 1800-18S0°C1800-1850°C producedproduced threethree SinceSince thithiss analysianalysiss wawass concentratedconcentrated mainlmainlyy onon typestypes ofof results.results. TheyThey were:were: colour-causingcolour-causing impuritiesimpurities suchsuch asas FFee andand TiTi similarsimilar (a)(a) ClearClear blubluee stonesstones procedureprocedure was repeaterepeatedd ttoo analyseanalyse standarstandardd solidsolid (b)(b) ClearClear stonesstones thatthat diddid notnot attainattain a satisfactorysatisfactory samplessamples witwithh varyinvaryingg concentratioconcentrationn ooff FeFe andand TTii inin colourcolour A1Alz0203 (Fe,Ti(Fe,Ti rangerange:: 0.01%-0.5%).0.01%-0.5%). CalibrationCalibration (c)(c) StonesStones withwith a non-transparentnon-transparent whitewhite coatingcoating curvescurves werewere useusedd ttoo estimateestimate tractracee elementselements semi­semi- ('dead('dead milk').milk'). quantitatively.quantitatively. OverOver 50%50% ofof thethe resultsresults belonbelongg toto thethe (c)(c) group.group. TheThe selectedselected areaareass oonn ththee samplessamples werweree flattenedflattened WhenWhen thethe initiallyinitially heatedheated stonesstones werewere re-heatedre-heated andand mirrormirror polishedpolished.. CrossCross sectionsectionss ooff ththee stonesstones ooff underunder oxidisingoxidising conditionsconditions inin thethe temperaturetemperature rangerange typetype (c)(c) werweree taketakenn ttoo analysanalysee ththee blubluee (centre)(centre) andand 1600-1800°C,1600-1800°C, typestypes (a)(a) andand (b)(b) showedshowed a reductionreduction deaddead milkmilk areaareass (edge)(edge)..

© CopyrightCopyright thethe GemmologicalGemmological AssociationAssociation ISSN:ISSN: 0022-1250022·12522 406 J. Gemm., 1991,22,7

Results and discussion When the 'dead milk' areas in type (c) stones were The samples were scanned at very low scanning analysed, relatively higher concentration levels of speeds under the same experimental conditions Fe and Ti were detected than in clear areas. In all using the EPMA, and the results were analysed and these type (c) samples the Ti level was noticeably averaged. The lowest detecting limit of Fe and Ti higher than Fe (Table 1). Among other minor was 0.03%. The concentration levels were classified impurities V was always present in all the type (c) as: low - 0.03% to 0.15%; medium- 0.15% to 0.3%; samples analysed. In 'dead milk'-free areas the Fe high - above 0.3% (see Table 1). and Ti levels were much lower than in the 'dead milk' areas and the number of minor impurities were also low. Table 1: EPMA results of heat treated 'geuda' However the reported minor trace impurities corundums were identified during the qualitative analysis. Since presence of V was possibly more significant Samples Fe Ti V Minor than the other minor impurities, those results were Trace tabulated separately, but no quantitative estimates Level are available for V. Impuri­ The possibility of contamination due to sample ties preparation was ruled out by analysing similar types of samples without employing the special prepara­ (a) Good blue stones * X ND Na, K, Mn tion method. Further detection of similar impuri­ (b) Very pale blue/ * • ND Na, K, Ca, ties in natural corundums have been reported by colourless Si, Zn Schmetzer and Bank (1980,1981), Bosshart (1982), stones Schmetzer and Bosshart (1983) and Schrader (1986). (c) Stones with 'dead milk' *** Conclusion (i) "dead milk'area Y Na, K, Ca, This study suggests that whilst the presence of Fe Mg, Ga, and Ti is necessary to give a blue colour to Mn, Si, Cr * * corundum, the presence of other minor impurities (ii) blue area Y Na,K, could prevent the formation of the required bi- Mg,Si particle and hence not produce an acceptable blue colour. This confirms the hypothesis of Schmetzer * -low (0.03-0.15%) and Bank (1980) in the explanation of different ** -medium (0.15-0.3%) behaviour of heat treated corundums due to other *** - high (above 0.3%) additional impurities. X - average value below lowest detecting limit The formation of the thick white precipitate Y - significant minor impurities ('dead milk') on the outer surface was apparent in ND -Not detected stones with high impurity concentration levels especially Fe and Ti. It is possible that V and some of the other impurities present in the sample may It is generally accepted that the blue colour of have helped this process. sapphires was caused by the formation of the (Fe.Ti)6+ bi-particle (Nassau, 1984; Eigenmann Acknowledgements and Gunthard, 1972; Harder & Schneider, 1986; Authors gratefully acknowledge Mr W Weera- Ediriweera & Perera, 1989). singhe for the assistance given in heat treatment and The average results (Table 1) show that the the Institute of Fundamental Studies (IFS) for concentration level of Fe in types (a) and (b) were facilitating the use of the EPMA and also Dr M similar, whilst the concentration level of Ti seemed Rupasinghe, Mr Deepal Subasinghe and Mr L to be lower in type (a) than in (b). The majority of Liyanage of IFS who helped us in the analyses. the type (a) samples showed Ti up to about trace impurity level and a few samples showed a slightly higher level similar to Fe. The only detected References additional impurities in (a) were Na, K and Mn. Bosshart, G., 1982. Distinction of Natural and Synthetic Rubies Some type (a) specimens did not even show traces of by Ultraviolet Spectrophotometry, Journal of Gemmology, XVIII, 2, 145-60. any of the minor impurities. However in type (b) Ediriweera, R.N., Perera, S.I., 1989. Heat Treatment of Geuda stones, the presence of a number of minor impuri­ Stones - Spectral Investigation. Journal of Gemmology, 21, 7, ties were clearly noticeable (Na, K, Ca, Zn, Si). 403-4. J.J. Gemm.,Gemm., 1991,22,71991, 22, 7 407

Eigenmann,Eigenmann, K.,K., Gunthard,Gunthard, Hs.H.,Hs.H., 1972.1972. ValenceValence States,States, RedoxRedox ReactionsReactions andand BiparticIeBiparticle formationformation ofof FeFe andand TiTi DopedDoped Sapphires.Sapphires. Chemical Physics Letters,Letters, 13(1),58-61.13(1), 58-61. Harder,Harder, H.,H., Schneider,Schneider, A.,A., 1986.1986. SolidSolid SolutionSolution ofof IronIron andand TitaniumTitanium forfor ExplainingExplaining thethe BlueBlue ColourColour ofof RutileRutile andand Spinel ContainingContaining Silky-Milky Silky-Milky Corundum Corundum after after Heat Heat Treatment, Treat­ ment, Neues Jahrbuch fur Mineralogie,Mineralogie, Montschefte,Montschefte, No.5,No. 5, 209-18. Nassau,Nassau, K.,K., 1984.1984. Gemstone Enhancement,Enhancement, Butterworths.Butterworths. Schmetzer, K., K., and and Bank, Bank, H., H., 1980. 1980. Explanation Explanation of the of Absorption the Absorp­ tion SpectraSpectra ofof NaturalNatural andand SyntheticSynthetic FeFe andand TiTi containingcontaining Corundums,Corundums, Neues Jahrbuch fur Mineralogie Abhandlungen,Abhandlungen, 139,2,216-25.139, 2, 216-25. Schmetzer, K., K., Bank, Bank, H., H., 1981. 1981. The The Colour Colour of Natural of Natural Corundums, Corun­ dums, Neues Jahrbuch fur Mineralogie,Mineralogie, Montschefte,Montschefte, 2,2, 59-68. Schmetzer,Schmetzer, K.,K., Bosshart,Bosshart, G.,G., 1983.1983. NaturallyNaturally ColouredColoured andand TreatedTreated YellowYellow andand Orange-BrownOrange-Brown Sapphires,Sapphires, Journal of Gemmology,Gemmology, XVIII,XVIII, 7,7, 607-21.607-21. Schrader,Schrader, Hans-Werner,Hans-Werner, 1986.1986. OnOn thethe ProblemProblem ofof UsingUsing thethe GalliumGallium ContentContent asas a MeansMeans ofof DistinctionDistinction betweenbetween NaturalNatural andand SyntheticSynthetic Gemstones,Gemstones, Journal of Gemmology,Gemmology, 20,20, 2,2, 108-13.108-13.

[Manuscript[Manuscript receivedreceived 1414 DecemberDecember 1990,1990, revisedrevised 1515 AprilApril 1991.]1991.] F.G.A. your key to the fascinating world of Gemmology

The Gemmological The Gemmological Association and Gem Association's course Testing Laboratory of has been specially Great Britain has been compiled into a series actively involved in of teaching modules the very beginning of that are both readable Gemmology as an and lavishly independent science. illustrated. Today, the Together they Association takes provide a pride in its I comprehensive step- international by-step guide to the reputation as a learned fascinating world of society dedicated to gemmology and an the promotion of opportunity to earn gemmological the coveted initials education and the FGA - Fellow of the spread of Gemmological gemmological Association. knowledge. To find out more The Association's Gemmological Association complete the coupon coveted Fellowship is below and we will a mark of excellence and Gem Testing Laboratory immediately forward only bestowed upon Of Great Britain the Association's individuals who 1991 prospectus successfully undertake the Association's giving full details of this unique course written and practical examinations covering all aspects of gemmology as a science. [please complete and return to the Gemmological Association Training Scheme. * 27 Greville Street, London EC1N 8SU England Tel: (071) 404 3334. Fax (071) 404 8843

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EmeraldsEmeralds fromfrom ColombiaColombia (Part(Part 2)*2)* George Bosshart Bosshart Switzerland Switzerland

AbstractAbstract berylberyl latticelattice (Cr(Cr = V,V, withwith thethe CrlVCr/V ratioratio foundfound toto bebe IntroductionIntroduction (Part(Part I)1) rangingranging fromfrom 4.54.5 toto 0.5,0.5, inin extremeextreme casescases fromfrom aboutabout 1010 AI.Al. TheThe historyhistory ofof thethe ColombianColombian emeraldemerald minesmines toto 0.1).0.1). Iron,Iron, however,however, hashas barelbarelyy beenbeen detecteddetected inin thethe A2.A2. TheThe geographicalgeographical locationlocation ofof thethe emeraldemerald UVIVISUV/VIS absorptionabsorption spectraspectra ofof ColombianColombian emeralds.emeralds. ThoughThough generallygenerally presentpresent inin slightlyslightly largerlarger amountsamounts occurrencesoccurrences 3+ thanthan Cr3+Cr ironiron doesdoes notnot recognizablyrecognizably influenceinfluence thethe colourcolour (little(little Fe22+ anandd possiblpossiblyy somsomee FeFe3+3+ positionepositionedd inin BI.Bl. TheThe emeraldemerald depositsdeposits andand theirtheir geologicalgeological thethe axialaxial channelschannels ooff thethe ring-silicatring-silicatee structure).structure). environmentenvironment A detailed presentation presentation of ofthe the currently currently known known internal inter­ B2.B2. HypothesesHypotheses ofof emeraldemerald genesisgenesis nal characteristicscharacteristics (inclusions(inclusions anandd growtgrowthh structuresstructures)) isis B3.B3. TheThe minemine workingsworkings supplemented by by a discussiona discussion of identification of identification problems prob­ lems withwith treatedtreated emeraldemeraldss andand ththee disclosurdisclosuree ooff thethe GemmologicalGemmological propertiesproperties (Part(Part 2)2) treatmenttreatment duringduring transactiontransactionss inin ththee wholesalwholesalee anandd retailretail CI.CI. Morphology,Morphology, qualityquality andand sizesize ofof thethe emeraldemerald trade. AllocationAllocation ofof thethe emeraldemeraldss toto individuaindividuall ColombianColombian crystalscrystals minesmines onon ththee basibasiss ooff inclusioinclusionn patternpatternss doesdoes nonott appearappear C2.C2. ChemicalChemical composition,composition, chromophorechromophore andand tracetrace possiblpossiblee inin mosmostt instances.instances. However,However, ththee differentiationdifferentiation elementelement contentscontents ofof ColombianColombian emeraldemeraldss fromfrom otheotherr naturanaturall emeraldsemeralds C3.C3. LightLight absorption,absorption, colourcolour andand fluorescencefluorescence (such(such asas thosthosee frofromm ththee PanjshePanjsherr ValleValleyy exhibitinexhibitingg veryvery C4.C4. OpticalOptical valuesvalues andand densitydensity similarsimilar (s,l,g(s,l,g)) three-phasthree-phasee inclusions)inclusions) oorr fromfrom difficult,difficult, CS.C5. InclusionInclusionss anandd growthgrowth characteristicscharacteristics modernmodern hydrothermahydrothermall anandd flufluxx syntheticsyntheticss iiss showshownn ttoo bbee feasiblefeasible bbyy a combinatiocombinationn ooff microscopymicroscopy,, refractometry,refractometry, TreatmentsTreatments (Part(Part 3)3) andand absorptionabsorption spectrometrspectrometryy (UV/VI(UVIVISS anandd NIR/MIR),NIR/MIR), D.D. OilOil,, ultrasoniultrasonicc anandd heaheatt treatmentstreatments assistedassisted bbyy chemicachemicall analysianalysiss onlonlyy iinn ththee mosmostt difficultdifficult cases.cases. SafeSafe identificatioidentificationn ooff authenticityauthenticity,, treatmenttreatment,, andand origioriginn ofof emeraldsemeralds,, howeverhowever,, iiss increasinglincreasinglyy becomingbecoming DiscussioDiscussionn ththee tastaskk ooff ththee expertexpertss iinn ththee specializespecializedd laboratory.laboratory. E.E. DifferentiationDifferentiation ofof ththee ColombiaColombiann emeraldsemeralds fromfrom ThThee mineralogicamineralogicall definitiodefinitionn ooff emeralemeraldd aass a yellowishyellowish naturanaturall emeraldsemeralds ofof otherother originsorigins,, syntheticsynthetic toto bluish-greebluish-greenn varietvarietyy ooff naturanaturall beryberyll iiss showshownn ttoo bebe emeraldsemeralds anandd emeraldemerald imitationsimitations valid forfor any any Cr Cr and and V-containing V-containing variety variety except except possibly poss­ ibly ththee rarerare,, absolutelabsolutelyy chromium-frechromium-freee (V,Fe)-beryls(V,Fe)-beryls AcknowledgementAcknowledgementss (modification of of the the former former definition definition of type of typeII emerald): II emer­ BibliographyBibliography ald): iinn manmanyy ooff ththee preferrepreferredd ColombiaColombiann emeralds,emeralds, chromiuchromiumm iiss clearlclearlyy dominatedominatedd bbyy vanadiuvanadium~CrlVm (Cr/V ratiratioo < 1).1). HoweverHowever,, chromiuchromiumm hahass a highehigherr efficiencefficiencyy ooff Abstract Abstract coloratiocolorationn thathann vanadiuvanadiumm anandd a mucmuchh highehigherr ononee thathann A condensecondensedd historicahistoricall anandd mininminingg survesurveyy iiss followedfollowed iroironn ionionss iinn ththee variouvariouss substitutionasubstitutionall anandd interstitialinterstitial by aa compilation compilation of theof themost most notable notable crystals crystals of Colombian of Col­ latticlatticee sitesitess ooff berylberyl.. CCrr influenceinfluencess coloucolourr eveevenn aatt ververyy ombian emeraldemeraldss eveeverr founfoundd anandd ooff ththee detaildetailss ooff theirtheir low tracetrace levels. levels. chemicachemicall compositioncomposition.. A summarsummaryy ooff ththee elementalelemental AAnn extensivextensivee anandd up-dateup-datedd selectioselectionn ooff literatureliterature,, substitutionsubstitutionss anandd theitheirr effecteffectss oonn ththee outlineoutlinedd rangrangee ooff coverincoveringg alalll aspectaspectss citedcited,, completecompletess ththee synopsissynopsis.. gemmological data data is is given. given. SpeciaSpeciall emphasiemphasiss iiss placeplacedd oonn ththee causcausee ooff ththee famous,famous, ThThee introductiointroductionn ttoo thithiss revierevieww iiss basebasedd oonn ththee studstudyy ooff a fractiofractionn ooff ththee vividlvividlyy greegreenn colorationcoloration,, i.ei.e.. oonn ththee selectivselectivee absorptionabsorption extraordinarilextraordinarilyy extensivextensivee literaturliteraturee oonn ColombiaColombiann emeraldsemeralds.. of orange-redorange-red and and violet violet light, light, dictated dictated by minor by minorcontents con­ ThThee maimainn parpartt ooff ththee papepaperr (Par(Partt 22)) containcontainss datdataa collectecollectedd anandd findingsfindings tentsof the of thechromophoric chromophoric elements elements Cr and Cr V andsubstituting V substitut­ achieveachievedd oveoverr manmanyy yearyearss iinn ththee SSESSEFF LaboratorLaboratoryy iinn ZurichZurich.. 3+ ParPartt 3 wilwilll deadeall witwithh ththee difficultiedifficultiess encountereencounteredd iinn identifyinidentifyingg treatetreatedd ingfor for Al AI3+ in octahedrally in octahedrally coordinated coordinated sites of thesites of the emeraldemeraldss anandd witwithh ththee disclosurdisclosuree necessarnecessaryy whewhenn sellinsellingg thethemm anandd wilwilll *Thi*Thiss iiss aa papepaperr whicwhichh wilwilll bbee publishepublishedd iinn TheTheJournal Journal iinn threthreee partsparts.. ThThee discusdiscusss ththee possibilitiepossibilitiess ooff differentiatiodifferentiationn betweebetweenn ColombiaColombiann anandd otheotherr completcompletee bibliographbibliographyy iiss presentepresentedd witwithh ParPartt 11.. naturanaturall emeraldemeraldss anandd ththee synthetisyntheticc emeraldsemeralds..

© CopyrightCopyright ththee GemmologicalGemmological AssociationAssociation ISSNISSN:: 0022-1250022-12522 410410 J.J. Gernrn.,Gemm., 1991,1991, 2222,, 77

TableTable 1.1. SomeSome ofof thethe largestlargest knownknown ColombianColombian emeraldemerald crystalscrystals ofof specialspecial quality,quality, iinn thethe chronologicalchronological orderorder ofof theirtheir discoverydiscovery

(1831)(1831) MuzoMuzo (Devonshire(Devonshire Emerald)Emerald) 1384ct1384 ct unknowunknownn (onc(oncee BritBrit.. Mus.Mus.,, London)London) 19201920 ChivorChivor (Patricia(Patricia Emerald)Emerald) 632632 ctct Amer.Amer. Mus.Mus. Nat.Nat. Hist.,Hist., NewNew YorkYork (1950)(1950) MuzoMuzo (five(five crystals,crystals, 220-1796220-1796 ct)ct) 17591759 ctct BancoBanco dede lala Republica,Republica, BogotaBogota 19671967 VegaVega dede SanSan JuanJuan (Gachahi)(Gachala) 858858 ctct Smithson.Smithson. Inst.Inst.,, WashingtonWashington DDCC 19691969 LasLas Cruces,Cruces, GachahiGachala (Emilia)(Emilia) 70257025 ctct privatprivatee ColombiaColombiann collectioncollection

GemmologicalGemmological propertiesproperties inin Prague.Prague. ItIt weighweighss 26802680 ctct andand cacann bbee admireadmiredd iinn Cl.CI. Morphology, quality and size of the emeraldemerald thethe TreasuryTreasury ooff ththee HofburHofburgg inin Vienna.Vienna. 'Patricia~'Patricia', crystals thethe unofficiallyunofficially mosmostt beautifubeautifull emeraldemerald wawass rere­­ TheThe crystalcrystal formsforms mostmost commonlycommonly observedobserved inin portedported ttoo havhavee beebeenn dethroneddethroned bbyy twtwoo single ColombianColombian emeraldsemeralds areare thethe firstfirst andand second-ordersecond-order crystalscrystals dugdug ououtt iinn MuzMuzoo iinn 1988,1988, measuringmeasuring 5.85.8 andand hexagonalhexagonal prismsprisms withwith flat endend facesfaces (basal(basal pina­pina- 5 cmcm inin prismprism length.length. coid)coid) andand theirtheir modificationmodification withwith smallsmall pyramidalpyramidal faces.faces. ItIt isis definitelydefinitely rarerrarer toto findfind thethe dihexagonaldihexagonal C2.C2. Chemical composition, chromophorechromophore and and trace trace prism,prism, thethe dihexagonaldihexagonal bipyramidbipyramid andand combina­combina­ element contents contents tionstions ofof crystalcrystal formsforms withwith stillstill moremore faces.faces. Elon­Elon­ InIn naturalnatural emeralemeraldd thethe majomajorr constituentsconstituents ofof berylberyl gatedgated crystalscrystals oftenoften growgrow parallelparallel toto eacheach otherother oorr - BeO,BeO, AlA1z2003,, andand SiOzSi02 - areare commonlycommonly accompa­accompa­ formform fan-shapedfan-shaped oror radiatingradiating aggregates.aggregates. SuchSuch niednied byby minominorr constituentsconstituents anandd tracetrace elementselements,, ththee growthgrowth typestypes maymay containcontain cavities.cavities. individualindividual amountamountss ooff whichwhich varvaryy considerably.considerably. MostMost ColombianColombian occurrencesoccurrences produceproduce a widewide ThreeThree kindskinds ooff minominorr constituentconstituentss cancan bbee differen­differen­ rangerange ofof emeraldemerald qualitiesqualities withwith respectrespect toto colourcolour andand tiated:tiated: transparency.transparency. TheThe opaqueopaque materialmaterial calledcalled 'moralla''moralla' - waterwater moleculesmolecules (in(in thethe openopen Si60wringSi60i8-ring chan­chan­ presentspresents thethe poorestpoorest qualityquality grade.grade. GoodGood qualities,qualities, nels),nels), however,however, areare veryvery saleablesaleable inin EuropeEurope and,and, accordingaccording - alkalisalkalis (mainly(mainly NazONa20 andand MgO)MgO) anandd toto statistics,statistics, eveneven moremore soso inin Japan,Japan, forfor instanceinstance aass - chromophoreschromophores (mostly(mostly CrZ03Cr203 andand Fez03,Fe203, butbut centrecentre stonesstones inin finerfiner jewellery.jewellery. alsoalso FeFeOO andand VZ03)' 203). TheThe showyshowy Trapiche emeraldsemeralds from from Muzo,Muzo , Cos­Cos- InIn hihiss revierevieww Esmeraldas, SchwarzSchwarz (1987)(1987) com­com­ cuezcuez andand PeftasPefias BlancasBlancas onon thethe otherother handhand appearappear ttoo piledpiled a significansignificantt numbenumberr ofof publishepublishedd chemicalchemical bebe collectors'collectors' itemsitems moremore thanthan jewellerjewelleryy compo­compo­ compositionscompositions ofof emeralds. 3a33 TheThe datadata varvaryy inin partpart nents.nents. TheThe namename 'Trapiche'Trapiche' isis derivedderived fromfrom ththee widelywidely frofromm authoauthorr ttoo author.author. hexagonal·hexagonal cog:·wheelcog-wheel barrelbarrel usedused inin ColombianColombian FromFrom thethe compiledcompiled compositioncompositionss iitt cacann bbee dede­­ sugarsugar mills.mills. TheThe growthgrowth formsforms ofof TrapicheTrapiche emeraldsemeralds ducedduced thatthat ththee water content ofof ththee ColombianColombian areare fairlyfairly variablevariable looking.looking. TheyThey consistconsist ofof sisixx sectorssectors respectivelyrespectively sixsix radialradial emeraldemerald crystals,crystals, regularlregularlyy arrangedarranged aroundaround a steeplysteeply taperingtapering hex­hex­ 3a agonalagonal pyramidpyramid andand separatedseparated fromfrom eacheach otherother bbyy 3a TheThe formulformulaa ooff ththee cyclosilicatcyclosilicatee structurstructuree ofof emeralemeraldd iiss Be3(Al,Fe,Cr,Vh[Si0316.xHzO,Be3(Al,Fe,Cr,V)2[Si03]6.xH20, witwithh x < 1.1. AccordinAccordingg ttoo literature,literature, whitewhite albitealbite oror darkdark carbonaceouscarbonaceous shaleshale particlesparticles syntheticsynthetic emeraldemeraldss produceproducedd bbyy flufluxx oorr hydrothermahydrothermall proceduresprocedures (cf.(cf. specialspecial literature).literature). VeryVery rarelyrarely cars-eyecafs-eye emeralds showshow minimalminimal contentscontents ofof ththee majomajorr constituentsconstituents BeOBeO,, AI2OAlz0 3 andand SiOlSi02 ofof 13,13, 1717 andand 64.564.5 weighweightt % respectivelyrespectively,. ThThee correspondincorrespondingg valuevaluess ooff havehave beenbeen reportedreported alsoalso (a(a specimenspecimen ofof 4.64.6 ctct isis mosmostt naturalnatural emeraldsemeralds areare belobeloww thesthesee limitslimits,, whilwhilee thosthosee ofof Col­Col­ housedhoused inin thethe SmithsonianSmithsonian Institution,Institution, WashingtonWashington ombian,ombian, AfghanAfghanii andand NigeriaNigeriann oneoness araree slightlslightlyy above.above. NumerousNumerous natural,natural, manmanyy ColombiaColombiann anandd somsomee AfghanAfghanii emeraldemeraldss shoshoww a higherhigher DC).DC). contentcontent ooff MgMgOO andand Na2NazO0 thathann ththee syntheticsyntheticss (maximu(maximumm valuevaluess ofof thethe OutstandingOutstanding emeraldemerald crystalscrystals havehave growngrown toto syntheticssynthetics ssoo fafarr areare 0.0.66 anandd 0.0.33 wt. % respectively).respectively). ApartApart fromfrom that,that, thethe Colombian,Colombian, likelike all otheotherr naturanaturall emeraldsemeralds,, contaicontainn zeolitizeoliticc waterwater prismprism lengthslengths ofof 1010 cmcm (and(and more)more) andand toto diametersdiameters ofof typetype I andand IIII (while(while ththee flufluxx syntheticssynthetics ddoo not)not).. ConverselyConversely,, ththee ofof 6 cm,cm, correspondingcorresponding toto weightsweights ofof thethe orderorder ooff ColombianColombian emeraldemeraldss areare freefree frofromm chlorinechlorine (C 1I cancan bbee founfoundd inin ththee 40004000 carats.carats. ThisThis isis phenomenalphenomenal forfor emeralds,emeralds, yeyett hydrothermalhydrothermal syntheticssynthetics ofof LindLindee anandd Biron/PoolBiron/Pool,, asas welwelll asas iinn ththee fluidfluid inclusionsinclusions ofof ColombianColombian emeralds,emeralds, ooff course)course).. TheTheyy ddoo nonott notnot unusualunusual forfor otherother berylberyl varieties,varieties, withwith berylsberyls ooff containcontain nickelnickel (Ni(NiH)3+) andand onlonlyy tracetracess ooff lithiulithiumm anandd moderatmoderatee ironiron industrialindustrial qualityquality reachingreaching weightsweights ofof severalseveral tons.tons. (unlike(unlike ththee recenrecerttt hydrothermahydrothermall syntheticssynthetics ooff RussiaRussiann manufacture,manufacture, SchmetzerSchmetzer 1988)\988).. ProbablyProbably thethe largestlargest emeraldemerald crystalcrystal ofof goodgood 3b3b SchwarzSchwarz (1990a(1990a)) foundfound ththee followingfollowing subdivisionsubdivision usefuusefull forfor ththee qualityquality everever foundfound weighedweighed 32043204 g (16,020(16,020 ct)ct) anandd characterizationcharacterization ooff minominorr constituentconstituent contentcontentss iinn emeralds:emeralds: waswas baptisedbaptised 'Muzo''Muzo' afterafter itsits placeplace ofof origin.origin. ThThee low medium high largestlargest polishedpolished emeraldemerald alsoalso camecame fromfrom MuzoMuzo anandd <<1. 1.55 1.5-2.1.5 - 2.55 >Z.5>2.5 wt%MgO isis a perfumeperfume bottle,bottle, 10.910.9 cmcm inin height,height, whichwhich wawass <<1. 1.00 1.0-Z.01.0-2.0 >2.> Z.O0 wt%NazO 0.4>0.4 wt% CrZ03 engravedengraved inin thethe yearyear ofof 16411641 byby DyonisioDyonisio MiseroniMiseroni <<0. 0.55 0.5-1.00.5-1.0 >>1. 1.00 wt%FeO J. Gemm., 1991, 22, 7 411

emeralds (0.5 to 1.9 weight% H20) is below or equal C3. Light absorption, colour and fluorescence to the average of natural emeralds of other origins. Chromophores causing green colour in beryls (and The infrared spectra of Colombian emeralds other silicates) by means of selective absorption of usually indicate a slight predominance of type II light are the transition metals Cr,V,Fe,(Mn),Ni,Co water over the free type I water. This is mainly due and(Cu).4 to the presence of Na+: As electric dipoles, water Cobalt and copper appear to be absent in Col­ molecules are orientated and bonded in the ring ombian emeralds. Their iron contents and traces of channels by neighbouring alkali and other cations manganese and nickel have no colouring effect in and thus called type II water. Type I water is not the presence of chromium and vanadium as will be alkali-bonded (Wood & Nassau 1968). shown in the evaluation of the spectra. A coupled atomic substitution by alkalis regularly If (Cr,Fe)-emeralds are designated 'normal' or takes place in natural emerald: Mg2+ mainly re­ type I emeralds and the yellowish-green (V, places Al3+ on the lattice sites of beryl while the Fe,Ni,Mn,Cr)-beryls as type II (Taylor 1977), the larger-sized Na+ ion is built into the ring channels Colombian emeralds with their Cr/V ratio averag­ of the crystal structure for electric charge com­ ing about 3 may be classified as the last representa­ pensation. tives of the more frequent type I. This type shows The magnesium and sodium oxide contents3*'3* of Cr/V ratios from 1.0 to 40 (in extreme cases to over Colombian emeralds (averaging 0.7 and 0.6 wt% 100). Thus the Colombian emerald population is respectively) are definitely lower than the corres­ bordering the rarer type II which has Cr/V ratios ponding values of natural emeralds of metamorphic below 1 (normally far below parity). Therefore and other provenance, excepting the very low Mg they could also be considered as an intermediate and Na contents of the recent emerald finds from emerald type. Jos, Nigeria. Most other natural type I emeralds are lower in Colombian emeralds take up a central position vanadium (V-free to V-poor) but higher in Fe3+ with regard to the substitution of aluminium in the and Fe2+ (ferriferous to Fe-rich). They display a beryl structure by the colouring transition ele­ bluish-green to blue-green colour, most obvious in ments, the chromophores Cr3+ and V3+ (in company the border-cases between emeralds and aquamar­ with some Fe3+ and Fe2+). Often they contain a ines like in certain stones from Miku, Zambia. little more Cr than V and relatively little total Fe The other extreme is represented by the (V,Fe)- (averaging about 0.3, 0.1 and 0.3 oxide%3b respec­ beryls, e.g. by those from Salininha (Bahia). They tively and a Cr/V ratio of approximately 3). In the are nearly free from chromium (Cr/V < 0.1) and next chapter, the effects on absorption and colour are still green, yet more yellow-green than the will be compared to those of natural emeralds with Colombian emeralds. On average, their absorption higher iron or vanadium contents. minima are shifted only 10-15 nm towards the In addition to these minor constituents, the yellow (in Figures 2a and 3 from approximately following trace elements (and molecules) foreign to 502 to 513 nm for the mean value of the o and e the beryl formula have been reported in Colombian spectra). Usually Biron synthetics also show a emeralds: higher content of V than of Cr (Cr/V ratios from 2+ + Ca,Sr,Ba,Mg / K,Rb,Cs / C02(?), F2 and about 0.2 to 0.7). radiogenic He in the structural ring channels Li+ (and vacancies) on the tetrahedrally coor­ Evaluation of the absorption spectra dinated Be2+ lattice sites (i.e. each beryllium ion The absorption diagrams of emeralds do not is surrounded by four oxygen ions located in the allow a quantitative analysis of the colouring agents corners of a slightly distorted tetrahedron) Cr,V,Fe,etc: Ti4+,Sc3+ / Mn,Ni,Fe2+ / Li+ (and vacancies) on In the visible (VIS) region of the electromagnetic the octahedrally coordinated Al3+ lattice sites spectrum, chromium efficiently masks medium (A106 octahedra) and iron and vanadium contents (Figures 2a,b,c) due to Al3+ on the tetrahedrally coordinated Si4+ lat­ its very high absorption coefficient (a beryl plate of 10 mm thickness is.discernibly coloured by as little tice sites (Si04 tetrahedra). All the properties discussed below are the results of the fluctuating supply of chemical elements 4 According to the mineralogical definition, emerald is the yellow-green to during emerald growth and of the imperfect struc­ blue-green variety of beryl. Every gemmological attempt to sharply separate Cr-emeralds from other green beryls must fail regardless of ture of these crystals. This so-called real structure whether the criterion is the absolute chromophore content (i.e. colour has been considerably disturbed by the incorpora­ saturation) or the ratio of the individual chromophore contents (i.e. tion of foreign chemical elements and by in- colour hue). Delimitations of the emerald term for the needs of the gem trade as proposed by Superchi & Rolandi (1980) suggesting the use of the homogeneous growth conditions (rapid pressure/ DIN 6164 Colour charts are remarkable but lack the international temperature changes, geotectonic stress, etc.). approval and a generally accepted, simple usage. ~ Cl -0 -0 N ..... ? N ..... S ':-< 412 J. Gemm., 1991,22,S" 7 density , ct filter 72 1.8 ambient at polarizer ). d 'B e Weight rald · . ) HNP record 1.5 eme = axis, Polaroid CrN a Colombian optical here a ( with I ) , the for ~ to 1982 tio high ( a r hart s pectively CrN s a content Bos re ( to mium due o I parallel hr c ype t and

W -rt "2 f"! Medium spectrophotometer Emerald VIS mm. / perpendicular 6 UV emerald. nearly SP8-IOO ngth polarization lombian e l Co with path Unicarn green Pye spectra a optical of , ray s aturated ) s e ( a 1.585 y locu of ." nil focal detector. 78, spectra 5 traordinar . first 1 ufthe ex < . t the l) n on and in orption r s ) f ', e b 0 ( a in cm lUr d / g ze 2.713 tempera mounted Polari Ordinary Fig.2a...... N ~ \.J.J N 8 o ...., 13 " 'C) 'C) J. Gemm., 1991- , 22, 7 o ':­ 413

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« absorption «> density ct, 'C 00 CO 00 1.188 <2Polarized 2 . 3

00 .1lo Fig. 416 J. Gemm., 1991, 22, 7

as 0.0025 % = 25 ppm Cr203, Wood & Nassau Their slightly yellowish or bluish-green hue is 1968). highly valued. Hue and saturation are not caused by In addition, the vanadium spectrum in the VIS a particularly high Cr content as in the emeralds (Figure 3) is very similar to that of chromium Fe3+ from Sandawana (Zimbabwe), Santa Terezinha and Fe2+ may be positioned in various lattice and (Goias) or the Swat Valley (Pakistan) (in the latter channel sites and then absorb in variable hues and two combined with high iron). Hue and saturation mostly in low intensities. of the Colombian emeralds rather are generated by a subtle combination of low to medium amounts of a. The positions of both colour-decisive4 absorption the colour inducing elements Cr and V with compa­ bands in the violet and orange-red spectral region are ratively little Fe. nearly identical for Cr and V: The dichroism (o-ray yellowish-green, e-ray polarization perpendicular to the c-axis (ordinary- bluish-green) is weak in the majority of these ray vibration, o) stones, thus generally less distinct than in the Cr bands near 430 and 593 nm, ferriferous emeralds from metamorphic occurr­ V bands near 434 and 618 nm ences with their definitely aquamarine-blue e-ray component. polarization parallel to the oaxis (extraordinary-ray The colour saturation can vary considerably from vibration, e) one Colombian emerald to another. Apart from that, Cr bands near 416 and 628/644 nm, the colour distribution within a single crystal can be V bands near 426 and 630 nm. extreme to such an extent that a colourless zone is adjacent to a saturated green one. As a rule, the While Al-substitution by chromium causes the well colourless zone is the older prismatic nucleus known absorption lines at enveloped by a younger green skin, or there are 476, 637 nm (0), 660 nm (e) and paler zonal lamellae intercalated between saturated 680.5/683.4 nm (doublet, e»o). green basal growth layers. Conversely, even large in addition to the bands cited above, absorption emeralds can show an homogeneous and strong lines in the V spectrum are looked for in vain (they green saturation. are situated in the near infrared region, according to Colourwise, emeralds from the various Col­ personal communication with K. Schmetzer, 1989). ombian mines cannot be distinguished, perhaps Thus vanadium is optically masked in the VIS by with the exception of those from Gachala. They the presence of chromium. tend to be paler and a little more bluish-green than Nevertheless, well polarized, low-iron spectra en­ other Colombian emeralds (Figure 2b). Chemical able a rough estimate of the Cr/V ratio by evaluating data of Gachala emeralds are scarce. The most the position of the absorption bands. Overlapping 5 recent analysis demonstrates that this colour is not of the Cr and V spectra produces intermediate caused by a higher iron content but by lower Cr and positions of the absorption maxima, with laboratory V concentrations. Fe is also much lower than'the recordings for Colombian emeralds averaging Colombian average (0.3 wt%), and an aquamarine approximately 2+ component in the e-ray absorption (due to Fe / 431 and 600 nm for the o-ray and Fe3+ charge transfer) is not present. 419 and 628 nm for the e-ray. On this basis the average Cr/V ratio amounts to about c. UV/VIS absorption spectra of emeralds permit 2.5 (variation from 0.5 to 4.5). statements to be made with respect to chromophore However, the most recent microprobe analyses ratios and colour, as well as differentiations between (Schwarz 1990b, 1991), prove that V may be distinctly superior to Cr and in individual cases even 5 Partial chemical analysis of eight Gachala emerald crystals much superior (or inferior). The variation of the Microprobe data, in weight % (Schwarz 1991) Cr/V ratio of Colombian emeralds thus is wider, Variation Mean Si02 66.77-67.55 67.22 ranging from approximately 0.1 to 10. A120, 16.69-17.48 17.15 The unexpected but incontestable fact is that the most Cr203 0.02-0.43 0.10 cherished Colombian emeralds frequently are type II V2O3 0.02-0.15 0.09 FeO(Fetot) 0.03-0.12 0.07 (vanadium) and not type I (chromium) emeralds. Ti02 n.d.-0.02 0.01 MnO n.d.-0.03 0.02 MgO 0.15-0.48 0.34 Na20 0.14-0.29 0.25 b. Superposition of the Cr and V spectra intensifies CaO n.d.-0.02 0.01 K20 n.d.-O.Ol 0.01 the VIS absorption bands and increases the steep­ Sum 85.27 ness of their slopes, thus creating the brilliant and pleasingly pure colour of the Colombian emeralds. BeO and H20 not analysed Cr/V-1.1 P Cl :3 " \0 \0 '" " - - ';-< "'" ~ -..,J J. Gemm., 1991, 22, 7 41.... 7 on 1.5. )) w =

« C/5 losses > -2 Cr/V I, u £light JJ ">> OH 173 type >> ~stray

2 >»by

•s s mm. e .... nm 4 ~< 682

_0." sf| 1 valley, _" length > C 1) .. doublet path - H «•§ . Panjsher line J?hI=gr:~1 «-a

•Sthe O,JS the optical »( S °£of from ~

^ ^ cand 1.588, ~7 nm - g Cno,o o emerald 630 S vn -O

U, ~* 03and 1;$1A nD" •S B°5430 , 3 bluish-green near

03a \ g/cm 0 of - fi 03 «N 03 is ^ * bands d !r! ^ 2.721 c in spectra

C C •"• apattern.

.2 udensity S c absorption 131-ct, i the inclusion Oabsorption U w J3 of c •S °°0.789 £ 03 r^. u-, .-. s

1) ~' 03 £ dense •a ^ s § the Polarized Weight 03 .SP'XMaxima •« 4. Fig. 418 J. Gemm., 1991,22,7

certain origins and synthetic productions. For the Cr than V, or even no V (examples Figure 2c and latter, evaluation of the absorption features is Biron synthetics). carried out in the UV, similarly to that pertaining to The UV-fluorescence under long-wave radiation the natural and synthetic rubies (Bosshart 1982), as varies in Colombian emeralds from inert to medium well as in the very near infrared (see special weak red. The reaction to short-wave UV rays is literature for near and mid-IR analysis). nearly always inert. This, as also the behaviour The average position of the absorption minima in the observed with a Chelsea filter, is undiagnostic and ultraviolet region for Colombian emeralds is at not suited for the discrimination of emeralds from 340 (±5) nm for the 0-ray and at many synthetic emeralds. 346 (±5) nm for the £-ray. A typically turbid, red VIS-fluorescence may be Transition from the absorption edge to the general excited in many Colombian emeralds with strong, absorption, on average, is at UV-poor lateral illumination from a fibre-optic 298 (±15) nm for the 0-ray and at beam (Figure 10). 304 (± 10) nm for the e-ray. These UV minima and absorption edge positions C4. Optical values and density have been found to be at lower wavelengths than The values given in Table 2 are low to average, those of natural emeralds from other deposits, compared to those of other natural emeralds. They including Jos, Nigeria, and Panjsher, Afghanistan relate to the numerous and largely independent (Figure 4), as well as those of synthetics containing substitutions by water, alkalis and chromophores iron or iron, nickel and copper (certain Gilsons, which can be small to medium in amount. Accor­ Inamori; Vasar USSR, etc.). Moreover, the UV dingly there is no strictly linear correlation ofn andD. minima of the Colombian emeralds are more deeply This irregularity can be explained by the variable developed. addition of zeolitic water (H20 type I and II in the On the other hand, the low-iron synthetic emer­ channels) which appears to influence density more alds (Chatham, Biron etc.) can be differentiated by than the optical values. their absorption edges at lower wavelengths and by The sets of data taken from the literature and the their broader UV minima. values collected at the Laboratory largely agree. Absorption bands in the very near infra-red caused Table 2 does not include data for Trapiche emeralds 2+ by Fe (near 820 nm) have hardly been detected in nor moralla, but only for mediocre to excellent Colombian emeralds nor in low-iron synthetics. In quality grade. The n (RI) and D values of Col­ most natural emeralds (Figure 4) and in Fe- ombian gem-quality material are unlikely to lie containing synthetics (Vasar), however, they can be outside the given ranges, yet slightly higher figures 2+ observed. The structural position of Fe is dis­ are to be expected for the rare specimens with 3+ puted (Al octahedral, Be tetrahedral or structu­ abnormally high chromophore (or alkali) contents. 3 ral channels?). Abnormally low density values such as 2.646 g/cm 3+ The moderate Fe content of Colombian emeralds (laboratory minimum 2.676) relate to enclosed usually does not make its appearance in their cavities or artificial resin-like organic fillers (ap­ 3+ absorption spectra: the substitution of Al oct. and plied in new, permanent treatments). 4+ Si tetr. is very subordinate and the aquamarine While refractive indices may very occasionally be 2+ 3+ component from Fe /Fe charge transfers on Al found to vary on strongly (colour-)zoned emerald lattice sites is absent. Therefore the colour- individuals, the hydrostatic determination of the 3+ inefficient positioning of Fe might be suspected density in all cases results in one value only, the to take place in the structural channels. bulk density. Two minor absorption lines at 733.8 and 833.4 nm (e^>o) are virtually always observed in Colombian C5. Inclusions and growth characteristics stones, but have also been noticed in a Panjsher Solid and (primary and secondary) fluid inclu­ emerald and a synthetic Biron individual. The cause sions, as well as growth inhomogeneities, are known of these absorption lines is not evident. as the main internal characteristics of Colombian emeralds. They permit conclusions to be drawn as d. Marginal notes for the practising gemmologist: to crystal growth and growth conditions. Character­ Cr absorption (and emission) lines can be seen istic features of Colombian emeralds are three- and through the spectroscope in type I but not neces­ multi-phase inclusions (Eppler 1973, Gubelin 1973, sarily in type II emerald (see Figures 2 and 3). Roedder 1982, Gubelin & Koivula 1986, Kozlowski However, because of the V masking discussed etal. 1988). above, the observation of Cr lines in the hand spectroscope does not infallibly mean that the a. Primary fluid inclusions appear in crystallographi- examined stone is a type I emerald containing more cally orientated, shallow cavities. Pseudo- J. Gemm., 1991, 22, 7 419

Table 2. Optical values and density of Colombian emeralds

Extraordinary nDe 1.565 to 1.578 Literature refractive index 1.566 to 1.581 Laboratory

Ordinary nDo 1.571 to 1.584 Literature refractive index 1.572 to 1.588 Laboratory

Maximum ne-n0 -0.005 to-0.007 Literature birefringence -0.005 to-0.008 Laboratory

Anomalous double frequently present, strong 'moire' extinction pattern refraction (due to strain in the optic axis direction)

Optic axis figure axial cross, mostly open (abnormal, slight biaxiality)

Dichroism often weak (0-ray ^ e-ray) 0 yellowish-green, e bluish-green

3 Density (ing/cm ) D 2.646to2.730 Literature D2o°/4°c 2.682 to 2.727 Laboratory 3 Accuracy of Lab. data(estim.)nD ± 0.002, D2o74°c ± 0.005 g/cm . secondary fluid inclusions are usually smaller and (s, for solid phases, also called daughter minerals), not orientated as the primary ones are. In larger embedded in the saturated residual liquid (phase /). numbers, the secondary inclusions are connected to The gas bubbles take up 10 to 11%, the crystals 12 each other. They indicate slightly to strongly to 15% and the brine about 75% of the cavity vaulted, ancient tension cracks (now healed fis­ volumes. The gas bubbles contain carbon dioxide sures). In their entirety these healing fissures mostly under variable pressure and can be surrounded by a 6 produce but a slight turbidity. The gem trade thin crescent of liquid carbon dioxide (^ 3% C02). sometimes calls the eye-visible veil in its green This can be detected only in shallow cavities surroundings a 'jardin' (Figure 5). (Figure 8). In the thicker ones the bubbles appear The individual, more or less shallow primary too dark because of the strong optical relief. cavities parallel to the main growth axis c are Methane (CH4) and nitrogen gas (N2) have also typically pointed or tapering into thin tubes. They been reported. form jagged peaks like regular fine palisades or The square to rectangular daughter crystals have coarse stockades (Figures 6,7,8). In basal directions been identified as halite (NaCl, cubic). It is assumed they present more roundish, shape-less or angular that there is also some subordinate sylvine (KC1, contours. A peculiarity which the author until now cubic). These 'flattened' cubic crystals are more has only observed in Colombian emeralds, is fluid often found than crystal forms resembling rhom- inclusions bending off from the prismatic to the bohedra. Considering their anisotropic nature, the basal direction (or vice versa). The widespread latter are assigned to a carbonate. It seems most interpretation as to the formation of the spiky- probable that they are calcite or dolomite crystals prismatic voids prior to the basal ones is very (Figure 8). doubtful in this light. Their dissimilar shape does Hexagonal, small-grained anisotropic crystals ex- not point to a chronological succession but to solved from the fluid fillings have been pictured as growth conditions depending from directional dif­ well. A single emerald crystal and even a single ferences within the crystals. cavity can house cubic, lozenge and other daughter The cavities were originally filled with a crystals. Combinations of several types of daughter homogeneous, single-phase brine at a temperature crystals and a gas bubble in the saturated residual of over 470°C. This was an aqueous solution with a salt content of approximately 40 wt% CI and Na 6 The longitudinal extension of fluid inclusions may have been epigeneti- cally constricted or even cut off. This event, called 'necking down' or ±(Ca,Si,Al,(C),K etc.). At room temperature and 'necking', modified the cavity fillings with respect to the relative with magnification, this fluid filling is seen to be volumes of the individual, segregated phases as opposed to the normal undisturbed (s,l,g) state. For instance, one very large gas bubble may mostly exsolved into three phases: an immobile gas have built up in one and a daughter crystal may have been cut off in the bubble (phase g) and one or several similar crystals neighbouring, separated cavity. 420 J. Gemm., 1991,22,7

Fig. 5. Dense inclusion array in an octagonal emerald from Fig. 6. Predatory octopus and his protegee with full stomachs Colombia. Width of photograph represents approx­ in a green sea. Three-phase inclusions of variable imately 6 mm. appearance, the largest one being a 0.4 mm long and unusually thick cavity, spiky on one side and filled with a gas bubble and a salt crystal (also containing an inclusion).

Fig. 7. Exceptionally thin cavities filled with residual brine, Fig. 8. Primary axial healing fissure with flat cavities contain­ slightly brighter gas bubbles (almost without any ing different exsolution components of constant relief) and two exsolved, zoned halite daughter crys­ volume proportions of s/l/g. Largest gas bubble with a tals. Jagging of these primary growth voids running delicate crescent seam of liquid carbon dioxide (C02), parallel to c, the main axis [0001] of the emerald largest daughter crystal with a rhombohedral habit and crystal. Width of photomicrograph represents approx­ zonal structure (a carbonate), smaller daughter crys­ imately 1.2mm. tals with a cubic habit (halite). Long diagonal of the rhombohedron circa 0.25 mm.

Fig. 9. Plane (pseudo?)secondary gas and fluid network in a Fig. 10. Yellow and dark brown primary cavity fillings of Colombian emerald. Width of photomicrograph repre­ segregated organic liquids (presumably light carbohy­ sents approximately 2.4 mm. drates): Length of drop about 70 /xm (0.07 mm). J. Gemm., 1991,22, 7 421

Fig. 11. Distorted polyhedral pyrite crystal with fine tension Fig. 12. Rhombohedral, colourless syngenetic mineral inclu­ fissures along its edges, enclosed in a structurally sion (calcite?) in a very transparent emerald. Smaller disturbed emerald. Length of pyrite crystal approx­ grains with less euhedral shapes (albite, quartz, pari- imately 0.85 mm. site?). Long diagonal of largest rhombohedron about 0.4 mm.

Fig. 13. Loose group of larger, brownish and smaller, yellowish Fig. 14. Aggregate of transparent crystals and small opaque parisite crystals included in the emerald displayed in grains (albite or carbonate and carbonaceous shale). Figure 5. Barrel-shaped, short-columnar and pyramid­ Width of largest cluster about 0.3 mm. al habits. Iridescent tension crack (not 'Opticon'- treated). Width of largest crystal approximately 0.35

Fig. 15. Small syngenetic pyrite crystals of different shape and Fig. 16. Red fluorescence (682 nm chromium emission) strong­ size, distributed on a basal plane. Width of photo­ ly excited by a 100 watt fibre-optic side illumination in micrograph represents circa 8 mm. a particularly transparent emerald octagon displaying long axial growth tubes and slightly vaulted pseudo- secondary healing fissures. Tiny mineral inclusions having acted as starting points for the slender acicular crystallization disturbances. Width of emerald appro­ ximately 9.2 mm. N it Cl '" ~ 'C 'C N " J. Gemm., 1991,22,- - 7 ':-' 422 ,!'J et mm. the , bands 3 and Weight slight less on 5.5 d. the the multiple a s e onlythe under- visible browmsh or crystal gicm spectru~ , , of Bosshart ( of *!-SlfiJiM||J|1^°l£*t play absorption The effect the about s orption 34 . s . dI 4 more towards in ab numerou Colombia. cause IS panslte

|aia;|1g!|lil§fils|l^effect l earth colourthan lesser but length a the region mcrease the absorption rare density is spaced body path have ct, Muzo(?)~ absorption strong spectrum multiplets) semJ-transpare~lt a ually behaVIOur: very 4.735 Polarized of from eq pan~Jte orange-yellow optical (line Classical regio~ VIOlet-blue contmuous I~ing absorpuoncentredal580nm, however, colour-change aI1982)seeninsomeparisites. e-ray Forthesakeof.c1a~ity . l3a . Fig ;: t "1 t ~ ~ ~ ~ If l t1 It lIE i . j i a ~ : ~ : H1 j ~~ 4Tf tWHI Jut {W itlt I ~ ~ r I~ l II l I \ . " t ITI~lili' HrITl]~ tlfHtjlt ~;l rtt ~UI~: m . I \ i I I Itb ~ , 1 mm ~ . . I I I, :1 .t 1 ~,' ~ =Fij ttl I· H Ilrl11' , ,., t,' i ~ ti nm t U' ~J I . : I~ .. I eli.; . f ' t, ~~, I:f II It, M lJ un?! ]JIlm ~I ~' t t t f IB, .' 1-. '. I I I 'I] t '~ t 8tJO ... ~ ~ i: j J l! ~ ! 'll II II rl . .. 11 1. " '1 t! 11 • .I i t I 1 . ~ ~: I!: J . III 1 .: . ... " : t ~ 1 . II~II~ 1,1/ I::: nt", " l . ' I 't· t t t I : 1m I I 'It · '1+ i!i J l!. ~. ~ tt l . I It It ,11 .: I~ ! • J t ~ f ij ~. '.:" I r l W I I ~ 111 , r ' ' ~ i i ' . 1 JI ' lit Ii j : "l 1 ! I I 11 . Ii If '. . , J~. ' t,. 1;;. ~ lill liT 1 . . J I I I!' n t 700 ~ ' . . II If t: I n III. ~~ I ::~I :li 'II flll 1m · .' l' ~1 ... :I II m II n fh III I' t ; I 4 .. ~ ~ rm I.m ': . [ . ::. I it . N ,~, m im IlTI Ittt ' . . i ti I , : I \ -j a ,: ~n § ~ U IlII n ~", U i ~1 1 ItII J I tI111 • 1 .. 11 [It L Ii 1 l i" I iJ I u~ t I ~ 1 . ~ .. . r · ~ttt! ~~ r [ r tt F. I' I I Ii ill ~r.r-::: U.· IHff t v: f v:. ' I I ~~A' '1 ~ I I : I I J 1 ~ u. U If ": '1 itt III m rn _ ...... =- r,_I". . I~ . . t'l . ml I t ~" lIB iJ ~ ~ I . ,I t t '? . -L HI . !~ t H , . -t:··. n ' . . . . . +Hi ... I ~ L ill11llTH IT1 l1ill I :' \ !~t #:. lj "7. )7'l,;a., 11. . .-. : .1:, ' I ... " lill!!ti! 1m L 1 'Hi : ~ V I\, !J hi» • '11 ' Jf IH ~ , ::' ~9 _I_~ I I 1 ff±! ,t ;' . '. Ii i. : .. : ~ \ ""'-'20 ~. , t1 It I H I I t l It III I - w il ~ ~n ~ 1m: ~ I . r I ~,::~. ' I 1 . . H ~4'J)/.T'J"1'- :j., fitl 2D ~ Ill: . ;1 H H H ~ = ~1 t m; :: ! ~' I ti ! r f ttl V r~, I~ I I ..IU..H? I LPn J , R ;i . If. "'1_' I " m " Ii J ] I. U . In \ . I t I H,l C7T i.! uI Itih 1 . I ~ il.-, ~ ,l I ~ r 1Icl? I ~ I \I~I ~_ lIU W 1It~ .~ . . . H . mT: .. ). -:="''2A Ii r~ tI, ~ ff U>'-A" I ,. ' t.. I _ tH rrHttHtii' m J. Gemm., 1991, 22, 7 423

solution are known as multi-phase fillings. Another Another, more frequent feature of Colombian kind of multi-phase inclusion can be made up of a emeralds are aggregates of tiny, dark grey grains. fluid, some liquid carbon dioxide, a gas bubble and They are thought to be particles of the wall rocks, solid rock salt. that is traces of carbonaceous shale such as those Two-phase fillings in the cavities are noticed less found in Trapiche emeralds (Figure 14). Pyrite, as frequently than three- or multi-phase inclusions. In well as albite, quartz, calcite and parisite, can occur healed fissures these (l,g) inclusions are small and in free crystal groups or grainy aggregates. Accu­ delicate. As autonomous basal networks of liquid mulation of a single mineral species on a growth and gas, they can show spectacular relief (Figure 9). plane has also been seen (Figure 15). Bands of fine This is yet another proof that the original chemical dust || c are occasionally observed also. composition of the fillings had not to be identical in From time to time rusty to yellow-brown goethite every single cavity or healing fissure of an emerald. turns up as a crust on fissures or as grainy aggre­ The observed phenomena point to a complex gates in cavities. This list of crystal inclusions may 7 geological history of the emeralds, marked by not be absolutely complete. syngenetic infiltration of fluid phases into the Microscopically and spectroscopically the listed primary growth voids and by secondary formation mineral inclusions are not readily identifiable, with and filling of tension cracks. the exception of parisite and the ore mineral pyrite. Occasionally the brine was heterogeneously en­ Statistically speaking, pyrite crystals appear most closed together with an immiscible constituent of commonly in Chivor emeralds and calcite and some dark brown liquid which could well be a parisite in Muzo emeralds. However, pyrite and cracked mineral oil. Brownish-yellow to dark calcite are found in emeralds of both districts and brown liquids sometimes are also found as single- parisite also in those from Coscuez. Thus in the phase fillingso f cavities (to present without a surface individual testing case, determination of origin by contact, i.e. sealed in). They are rare and presum­ mineral inclusions is not feasible. ably also primary formations. In Figure 10 two So far Gachala emeralds alone seemed to be types of organic liquids can be distinguished, the recognizable to some extent. They exhibit a better darker hydrocarbon having segregated in several transparency (fewer healing fissures), a paler and instances as droplets from the lighter variety. more greenish-blue colour, more mineral inclusions (albite), more and longer growth tubes and a b. Proto- and syngenetic mineral inclusions are not stronger VIS-fluorescence (Figure 16) than other particularly frequent in Colombian emeralds. They Colombian emeralds. These properties, however, consist of pyrite crystals displaying a bright yellow are said to be virtually identical to those of emeralds metallic lustre (Figure 11) and the following colour­ from the 'new' Yacopi mine in the Muzo district less minerals: tabular albite, rhombohedral calcite (personal communication by D. Schwarz, 1989). or dolomite (Figure 12, sometimes whitish) and rarely also prismatic quartz. c. Internal growth characteristics of five different Small reddish to yellowish-brown spear-shaped kinds have been noted in cut Colombian emeralds: crystals of the decidedly rare, trigonal parisite as colour zoning, colour spindles, growth zoning, Ca(Ce,La,Nd,Pr)[(C03)3/F2] may be noted in Col­ growth spirals, and growth tubes. On the other ombian emeralds. hand, twinning has not been observed in a single The most prominent parisite inclusions encoun­ instance (twinning in beryl is extremely rare). tered were fairly large, brownish-yellow barrel- As a rule, colour zoning as well as straightforward shaped to pyramidal crystals (maximum length 0.7 growth zoning (i.e. zoning without colour contrast, mm, maximum diameter 0.35 mm, Figure 13). Figure 17) occur as series of prismatic and/or basal Parisite (Ca(Ce,REE)-carbonate) was successfully planes. Pyramidal zoning is less widespread. identified by the main lines and bands of the rare Prismatic colour zoning classically consists of a earth absorption spectrum at 442, 460, 512, 520, sharply defined, colourless, yellowish or pale green 534, 574/579/584 and 678 nm. The spectrum was prismatic core, surrounded by a saturated green observed through a hand spectroscope held into the shell. Colour distribution can also be inverse. Hosts ocular tube of a stereo-microscope and compared to of colourless 'holes' are met with much less fre­ the absorption spectrum of a crystal specimen from quently. These are essentially colourless prism-like Colombia recorded on a spectrophotometer (Figure 13a). Recent chemical investigations by ED-XFA and electron microscope analyses of these inclu­ 7 Fujisaki (1976) identified several ore minerals in a Colombian emerald sions and other Colombian parisite samples con­ individual: pyrite, pyrrhotine, pentlandite and rutile. The formation of firmed the elements Ca,Ce,La,Nd+Pr and a very the last three minerals is difficult to explain in the postulated hydrother- mal growth environment (especially pentlandite (Fe,Ni)9Sg, cubic) good cleavage. In addition, traces of Y and Th were except, if some connection from a remote (ultra)basic source to the found to be present. deposit had been in existence. 424 J. Gemm., 1991,22,7

Fig. 17. Lamellar to slightly wedge-shaped basal growth struc­ Fig. 18. Host of nearly colourless, axial columns in an emerald tures with palisades of short spindles on individual cabochon. Largest diameter of the columns approx­ growth planes. Photomicrograph height represents imately 1.5 mm. 1.50 mm.

Fig. 19. Steep, saturated green pyramids with axes parallel to Fig. 20. Axial growth tube with a spiral passing from a fissure the main growth direction c of the emerald. Height of into a healing fissure. Next to it a more delicate helix in pyramids up to about 0.5 mm. reverse sense of rotation. Width of photomicrograph represents approximately 2 mm.

Fig. 21. Axial view onto a basal plane covered with corrosion Fig. 22. Faceted Colombian emerald with characteristic, cells. Shallow etch pits structured with modified or strongly reflective tension cracks, in the de-oiled state. hinted hexagonal contours. Width of photomicrograph Length of brightest crack approximately 1.25 mm. about 9 mm. J. Gemm., 1991, 22, 7 425 columns of small diameter parallel to the c-axis in growth direction (Figure 16), occasionally also otherwise green crystals (Figure 18). vertical to the c-axis. These tubes are very fine and Basal colour zoning can be a sequence of colour­ long and can show two-phase (l,g), three-phase less and green, flat and well defined lamellae. As (s,l,g) or multi-phase fillings (si,s2,lbl25g)- cutters usually orient the emerald with the c-axis Starting point for the growth tubes are sometimes almost parallel to the table, the basal zoning can be the mineral inclusions described above because quite obvious as a colour striation traversing the these solids have formed intrinsic obstacles facing crown of the stone. Similarly, in the case of the fluid the growth front. Tubes are growth gaps compara­ inclusions, transitions can be seen between the ble to very long negative crystals (often measuring prismatic and the basal zoning which, in reality, are several millimetres). combinations of both directions with small pyra­ Actual negative crystals have not frequently been midal growth zones in between. encountered among gem quality material, the The pyramidal colour zoning normally starts on largest one according to laboratory notes having basal planes. These pyramids may show very strong been a lathe-like cavity measuring about 1.6 x 0.8 green colour saturation and steeply sloped arches x 0.45 mm. tapering in the growth direction (Figure 19). Pyra­ mids may also be pale in colour and have formed d. Flat primary cavities, colour zoning, growth prior to the growth of green zones. Well-defined spirals and tubes are all indicators of emerald crystal zigzag formations towards the outside of the crys­ build-up. The contrary, decomposition, is much tals do not necessarily stem from irregular pyramid­ rarer, making its appearance in the form of flat, al growth of variable inclination but rather from cellular etch pits on basal planes (Figure 21, as growth planes separating the older core and the occasionally also seen on the base of emerald younger shell. crystals). These etch marks have been overgrown Closely related with the growth pyramids, on the again, subsequent to the corrosion phase. Under other side, are palisades of flame-like spindles crossed polars they show strain birefringence in­ which also originate on basal planes (Figure 17). stead of straight extinction and low optical relief. Neither colourless nor coloured spindles are very Although Figure 21 can also be interpreted as flat common but they can reach lengths of up to 2 mm. hillocks (truncated pyramids) as a consequence of Small hillocks on basal planes reminiscent of the spiral or polygonal beryl growth (cf. Sinkankas shallow growth pyramids of Linde synthetics have 1981, Figures 9-26), this interpretation is less also been detected. probable than corrosion in view of the irregularity Under the microscope, basal, prismatic and pyra­ of their contours. midal growth zoning can easily be recognized and Similar or identical cellular phenomena have also differentiated. According to Kiefert & Schmetzer been described as thin, basal layers of calcite (1990), combinations of zonal structures enable crystals. identification of authenticity of Colombian emer­ alds but not of their exact provenance. e. The least desirable properties of many Col­ Growth spirals are attractive but sporadic phe­ ombian emeralds are undoubtedly their numerous nomena in Colombian emeralds. They prove two tension cracks. They have formed either during or facts: that an emerald crystal does not have to be after growth (and could have been healed out) and built up by planar growth fronts and that healing of some could have formed during mining. Since the spirals by fluid brines can set in and be white light is reflected back from these fractures to terminated at any stage of growth (Figure 20). The the outside after a short light path through the same phenomena can be observed in the hydrother- emerald, the cracks are very obvious and look white mal synthetics after Biron (today Pool, Australia), rather than green (Figure 22). however, without a central growth tube. Other subtle and quite common characteristics are the growth tubes. They run parallel to the main [Manuscript received 19 March 1990.] 426 J. Gemm., 1991,22,7 GEMDATA - UPDATE 3 A computer program for gem identification * Now available in 3.5-inch disk version *

Now available in its third updated version, GEMDATA is compiled in QuickBASIC and will run directly from MS-DOS on any IBM PC-compatible computer. It is designed to help with both appraisal identifications and gemmological studies. An optional update of GEMDATA is available each year. GEMDATA is supplied on either a SV^-inch double-sided, double- density disk, or a 3y2-inch disk, and contains the following two sections:- Gem 1. Gem and Crystal Identification from a databank of over 220 gems (now with additional data on inclusions, spectra, pleochroism and luminescence) Gem 2. Gem Comparisons (side-by-side display of the constants and crystal systems of selected gems). Tables of RI and SG values (with additional data on inclusions, etc), Gem Calculations (SG, reflectivity, critical angle, Brewster angle and gem weight/diameter estimation) The GEMDATA package, complete with disk, operating notes and gem index, costs £96.00 + VAT, postage and packing. To order your package please use the coupon provided on p. 454 GEMMOLOGICAL INSTRUMENTS LTD A division of The Gemmological Association and Gem Testing Laboratory of Great Britain 27 Greville Street, London EClN 8SU. Telephone: 071-404 3334 Fax: 071-404 8843 J. Gemm., 1991,22, 7 427

The microscopic determination of structural properties for the characterization of optical uniaxial natural and synthetic gemstones Part 2: Examples for the applicability of structural features for the distinction of natural emerald from flux-grown and hydrothermally-grown synthetic emerald

Dipl.-Min. Lore Kiefert1 and Dr Karl Schmelzer2

1 Griffith University, Queensland, Australia 2Marbacher Str. 22b, D-8067 Petershausen, Germany

Abstract Resumen The application of diagnostic growth structures for Se, discute la aplicación de marcas de crecimiento the distinction of natural and synthetic emeralds is diagnósticas para identificar las esmeraldas naturales y discussed. Typical examples for the characterization of sintéticas. Se facilitan ejemplos tipicos para la natural emeralds from distinct sources as well as of their caracterizacion de esmeraldas naturales de yacimientos synthetic counterparts of some producers are given. determinados. Se subrayan criterios que son útiles para Criteria which are useful for the recognition of faceted reconocer gemas talladas como naturales o sintéticas. gemstones as natural or synthetic are underlined. Gem Las gemas descritas con detalle son esmeraldas materials described in detail are natural emeralds from naturales de Colombia y Nigeria, esmeraldas sinteticas Colombia and Nigeria, flux-grown synthetic emeralds Chatham, rusas y Gilson obtenidas por el from Chatham, Russia and Gilson as well as different procedimiento "melt" al igual que otras esmeraldas hydrothermally-grown synthetic emeralds (Linde, Regency,obtenida s por el procedimiento hidrotermal (Linde, Lechleitner, Biron, Pool, and Russian synthetic Regency, Lechleitner, Biron, Pool y esmeraldas emeralds). sintéticas de origen ruso). I. Introduction In the first part of this publication (Kiefert & Zusammenfassung Schmetzer, 1991) a detailed description of methods Die Anwendung von Wachstumsstrukturen zur for the determination of characteristic crystal faces Unterscheidung natürlicher und synthetischer Smaragdse wird beschrieben. in faceted optical uniaxial gemstones by use of two Nicht nur typische Beispiele zur Charakterisierung simple auxiliary means is presented. These means von natürlichen Smaragden verschiedener Herkunft are a two-axial sample holder (cf. Schmetzer, 1986) werden erwähnt, sondern auch von synthetischen and a rotatable measuring ocular with cross hairs Gegenstücke. attached to the lens, both with attached 360° dials Nützliche Kriterien zur Erkennung geschliffener and fixable indicators. The best obtainable results, Edelsteine als natürlich oder synthetisch werden i.e. a complete determination of the structural betont. characteristics present in one sample, are available Die ausführlichst beschriebene Edelsteine sind by a combination of both methods. natürliche Smaragde aus Kolumbien und Nigeria This second part of the publication will reveal sowohl nach dem Flußmittelverfahren gezüchtete Smaragde (Chatham, Gilson, Rußland) als auch some examples for the practical applicability of the verschiedene nach dem Hydrothermalverfahren methods described in the first part in detail. The gezüchtete synthetische Smaragde (Linde, Regency, characterization of natural emeralds from two im­ Lechleitner, Biron, Pool und russische synthetische portant sources (Colombia and Nigeria) as well as of Smaragde). some of their commercially available flux-grown

© Copyright the Gemmological Association ISSN: 0022-1252 428 J. Gerhm., 1991, 22, 7

Fig. 16. Growth structures in natural emerald from Colombia; Fig. 17. Growth structures in natural emerald from Colombia; planes parallel to the hexagonal prism m and m' {1010} planes parallel to the hexagonal prism faces m {1010} form an angle of 120°, smaller planes parallel to the and a {1120} form angles of 150°. View parallel to the prism a (1120) are also present. View parallel to the c-axis. Crossed polarizers. 25x. c-axis. Crossed polarizers. 18x. and hydrothermally-grown synthetic counterparts sodium and magnesium and, using only this fea­ by means of growth structures is selected as one of ture, are hardly distinguishable from synthetic the typical and important problems of determina­ emeralds. Absorption spectra of Colombian emer­ tive gemmology. alds also -disclose no characteristic iron absorption Figures 1-15 as well as Tables 1-3, which are bands, which are very often useful as diagnostic occasionally referred to in this second part of the features for natural emeralds from metamorphic publication, are presented in the first part (Kiefert source rocks. Consequently, high quality emerald & Schmetzer, 1991). samples from Colombia or Nigeria sometimes cre­ ate problems in determinative gemmology. In order II. Natural emeralds from Colombia and Nigeria to determine additional characteristic properties for Natural emerald is mainly found in metamorphic these two types of emeralds, more than 200 rough deposits. Emeralds from these sources are recogniz­ and cut Colombian emeralds from different mines, able by the presence of many different mineral and more than 100 rough and cut Nigerian emeralds inclusions such as mica and actinolite. Further were made available for a detailed investigation. diagnostic properties of emeralds from metamor­ In general, the internal growth structures of phic deposits are characteristic sodium- and magne­ Colombian cut emeralds correspond to the mor­ sium-contents, which are generally higher than phology of rough samples. The most significant those of synthetic stones. Absorption spectroscopy, growth planes in all Colombian emeralds are the which can, besides microscopic investigations, also first-order hexagonal prism m (1010) [Figure 16] be used as a non-destructive method, frequently and the basal pinacoid c (0001). Part of Colombian reveals distinct iron absorption bands as well as a samples additionally reveal the second-order hex­ characteristic aquamarine component (Schmetzer, agonal prism a (1120), most frequently in a size 1988). The emeralds from metamorphic source rocks, however, in many cases do not disclose characteristic growth structures of diagnostic value. Fig. 18. Growth structures in natural emerald from Colombia; On the contrary, emeralds from deposits with a planes parallel to c (0001), p (1012), u (1011) and m temperature of formation lower than that of samples (1010). View perpendicular to the c-axis, the c-axis from metamorphic deposits, reveal characteristic runs vertically. 80x. growth features useful for diagnostic purposes. Fig. 19. Growth structures in natural emerald from Colombia; planes parallel to c (0001), s (1122) and a (1120). View Typical examples for these types of emeralds occur perpendicular to the c-axis, the c-axis runs vertically. in different deposits in Colombia, in Nigeria, and, 85x. Figs. 18 and 19 are related by a rotation of 30° occasionally, are also found in material from Afgha­ about the c-axis. nistan. Larger quantities of emeralds from Afgha­ Fig. 20. Growth structures in natural emerald from Colombia; planes parallel to c (0001), p (1012) and m (1010). View nistan are very difficult to obtain and, therefore, perpendicular to the c-axis, the c-axis runs vertically. samples from this particular source will not be 80x. considered in this publication. Fig. 21. Growth structures in natural emerald from Colombia; Colombian and Nigerian emeralds, in contrast to planes parallel to c (000 lj, s (1122) and a (1120). View perpendicular to the c-axis, the c-axis runs vertically. emeralds from metamorphic source rocks, in most 70x. Figs. 20 and 21 are related by a rotation of 30° cases do not reveal any diagnostic contents of about the c-axis. J.. Gemm.Gemm.,, 19911991,22,7, 22, 7 424299

Fig. 18

Fig. 2020 Fig. 21 430430 J.J. Gemm.,Gemm., 1991,22,71991, 22, 7

Fig. 23

Fig.Fig. 2424 Fig.Fig. 2525 J. Gemm., 1991, 22, 7 431 smaller than the prism m as shown in Figures 4c and general, do not occur in synthetic emeralds pro­ 16. Occasionally, this face also can reach the same duced by the flux method (see section III). Howev­ size as the first-order hexagonal prism m (10Ï0) er, the crystal faces c (0001), m (1010) and a (1120) [Figure 17]. Additional growth planes are the can also be present in synthetic emeralds and, first-order hexagonal dipyramids u (1011) and p therefore, in samples in which only these crystal (10J.2) and the second-order hexagonal dipyramid s faces are determined, no definite characterization of (1122) [Figures 4a, 4c, 18, 19]. These dipyramids the emerald by means of growth structures is were found to occur all together in some samples, possible. other samples revealed only the first-order hexagon­ al dipyramid p (1012)_and the second-order hex­ III. Some important types of flux-grown synthetic agonal dipyramid s (1122) [Figures 4b, 20, 21], and emeralds others disclosed, additionally to the above men­ The results of some experiments, in which spher­ tioned basal and prism faces, only the second-order ical seeds of natural beryl crystals were prepared hexagonal dipyramid s (1122). So far, it has not yet and subsequently used for growing synthetic emer­ been possible to distinguish between emeralds of alds in a flux of V2Os were published by Ushio the two major mining districts Chivor and Muzo, (1977). During these experiments Ushio observed because part of the material available to the authors, in the first state of crystal growth the crystal forms c most presumably, was already mixed up in Col­ {0001}, m {ÎOTO} and a {1120} as well as different ombia. first- and second-order hexagonal dipyramids. Af­ The morphology as well as the internal growth ter some days, however, all hexagonal dipyramids structures of the investigated emeralds from Niger­ disappeared, and the final morphology of the ia are identical with growth structures of aquamar­ synthetic emeralds produced by this flux method ines from the same mining districts (cf. Lind et al, resulted in dominant basal pinacoids c {0001} and 1986). Beryls from this source always disclose the first-order hexagonal prism faces m {1010}, occa­ first-order hexagonal prism m (1010) [Figure _27] sionally with a subordinate small second-order and the second-order hexagonal dipyramid s (1122), hexagonal prism a {1120}. as well as the basal pinacoid c (0001) in different This morphology corresponds to the morphology sizes [Figures 4b, 23, 25]. Besides these crystal of flux-grown synthetic emeralds produced by faces, Nigerian emeralds very rarelyshow a small Chatham as well as to Russian flux-grown synthetic second-order hexagonal prism a (1120) or a small emeralds as described in the literature. According to first-order hexagonal dipyramid p (1012) [Figures Schrader (1987), crystal growth of Chatham flux- 4b, 22,24,26]. The first-order hexagonal dipyramid grown synthetic emeralds is performed by the use of u (1011), which is quite common in Colombian small seed crystals. Russian flux-grown synthetic emeralds, has not yet been observed in Nigerian emeralds are produced by means of seeded growth samples. as well as by spontaneous crystallization (Bukin In comparison to synthetic emeralds produced by et a/., 1980, 1986), which is also mentioned for the flux method, a characteristic feature of emeralds Chatham flux-grown synthetic emeralds (e.g. from the two groups of deposits discussed above is Nassau 1976,1980). the presence of the first-order hexagonal dipyr­ Consistent with literature data dealing with the amids u (10Ï1) and p (10Ï2) as wellas the second- morphology of both types of flux-grown synthetic order hexagonal dipyramid s (1122), which, in emeralds, faceted samples of Chatham and Russian flux-grown synthetic emeralds examined by the authors disclose, as internal growth structures, only Fig. 22. Growth structures in natural emerald fromNigeria; planes parallel to c (0001), p (1012) and m (1010). View a combination of c (0001), m (1010) and a (1120) perpendicular to the c-axis, the c-axis runs vertically. [Figures 28, 29, 31, 32, 33]. Other growth planes, Crossed polarizers. 20x. for example in natural emeralds frequently Fig. 23. Growth structures in natural emerald from Nigeria; observed hexagonal dipyramids u (1010), planes parallel to c (0001) and s (1122). View perpen­ dicular to the c-axis, the c-axis runs vertically. 20x. p (1012) and s (1122) were not found in these Figs. 22 and 23 are related by a rotation of 30° about the flux-grown synthetic emeralds, and residual seeds c-axis. were not observed. In addition to growth struc­ Fig. 24. Growth structures in naturalberyl from Nigeria; tures, another common feature of flux-grown planes parallel to c (0001), p (1012) and m (1010). View synthetic emeralds is the zoning of residual flux perpendicular to the c-axis, the c-axis runs vertically. 30x. parallel to dominant growth planes [Figures 30,32], Fig. 25. Growth structures in natural beryl from Nigeria; which does not arise in natural stones in this planes parallel to c (0001) and s (1122). View perpen­ particular form. dicular to the c-axis, the c-axis runs vertically. 30x. Figs. 24 and 25 are related by a rotation of 30° about the As an example for flux-grown synthetic emeralds c-axis. often containing residual seed plates, properties of 432 J. Gemm., 1991, 22, 7

Fig. 26. Growth structures in natural emerald fromNigeria; Fig. 27. Growth structures in natural beryl from Nigeria; planes parallel to c (0001), p (1012) and m (1010). View planes parallel to the hexagonal prism m and m' {1010} perpendicular to the c-axis, the c-axis runs almost form an angle of 120°. View parallel to the c-axis. 30x. vertically. Crossed polarizers. 12x.

Fig. 28. Growth structures in Chatham flux-grown synthetic Fig. 29. Growth structures in Russian flux-grown synthetic emerald; planes parallel to the hexagonal prism faces m emerald; planes parallel to the hexagonal prism faces m {1010} and a {1120} form angles of 150°. View parallel {1010} and a {1120} form angles of 150°. View parallel to the c-axis. Crossed polarizers. 35x. to the c-axis. Crossed polarizers. 20x. J. Gemm., 1991,22,7 433

Fig. 32. Growth structures in Chatham flux-grown synthetic Fig. 33. Growth structures in Russian flux-grown synthetic emerald; planes and zoning of residual flux parallel to emerald; planes parallel to the basal pinacoid c (0001) the basal pinacoid c (0001). View perpendicular to the and parallel to one of the prism faces (m or a) form an c-axis, the c-axis runs vertically. 40x. angle of 90°; an intense colour zoning is also visible, growth zones confined to the prism are intense green, growth zones confined to the basal pinacoid are light green. View perpendicular to the c-axis, the c-axis runs vertically. 25x.

Fig. 30. Growth structures in Chatham flux-grown synthetic Fig. 31. Growth structures in Russian flux-grown synthetic emerald; zoning of residual flux parallel to the basal emerald; planes parallel to the hexagonal prism m and pinacoid c (0001). View perpendicular to the c-axis, the m' {1010} form anangle of 120°, smaller planes parallel c-axis runs vertically. 20x. to the prism a (1120) are also present. View parallel to the c-axis. Crossed polarizers. 20x. 434 J. Gemm.,1991,22,7

Fig. 34. Growth structures in Gilson flux-grown synthetic Fig. 35. Growth structures in Gilson flux-grown synthetic emerald; planes parallel to the basal pinacoid c (0001). emerald; planes parallel to the hexagonal prism faces m View perpendicular to the c-axis, the c-axis runs {1010} and a {1120} form angles of 150°. View parallel vertically. 40x. to the c-axis. Crossed polarizers. 34x. Gilson synthetic emeralds will be discussed in some emeralds with part of the seed plate and stones details. In an earlier state of the production of without residuals of the seed could be distin­ Gilson synthetic emeralds, most presumably seed guished. Consistent with the more recent literature plates cut parallel to the basal pinacoid c (0001) were cited above, the samples examined by the authors used (Sinkankas, 1981; Schrader, 1987), which is contained only seed plates of flux-grown synthetic recognizable in cut samples by growth structures emerald. Depending on the position from which the parallel to this dominant growth plane (cf. Schmet- stone was cut out of the synthetic emerald crystal, zer, 1989). different possibilities of growth structures are Obviously, the orientation of seed plates in Gilson observable in cut samples. synthetic emeralds was changed for the more recent In those without part of the seed plate a number commercial production. According to Diehl (1977), of stones revealed only a distinct zoning parallel to a tabular seed plate of natural colourless beryl cut the basal pinacoid c (0001) as growth structure parallel to the second-order hexagonal prism a [Figure 34], others showed onlystructures parallel (1120) was observed in a rough crystal of Gilson to one of the prism faces m (1010) or a (1120). In synthetic emerald. Later on, seed plates of synthetic another part of this type of cut stones growth emerald were cut in the same orientation from the structures were observed, which revealed two sets of synthetic overgrowth of the colourless beryl seed prism faces m and m' or m and a [Figure 35]. In and used instead of that (Nassau, 1976, 1980). other examples, the basal pinacoid c (0001) in During crystal growth, a morphology is developed, combination with one of the two prism faces m which, in addition to the basal pinacoid c {0001}, (lOTO) or a (1120) was found [Figure 36]. consists of two largersecond-order hexagonal prism In natural emeralds, no growth structures re­ faces a and a' {1120} on opposite sides of an sembling those mentioned above were observed octagonally shaped crystal, as well as of six crystal because of the size of natural emeralds. In other faces built by the first-order hexagonal prism m words, no natural samples with growth structures {1010}. This information is based on the investiga­ parallel to only one single basal or prism face in the tions of rough crystals of Gilson synthetic emeralds whole cut sample or parallel to one prism face and by Diehl (1977,1982) and Schrader (1987), and part the basal pinacoid were observed by the authors. of it is also found in the publication of Schwarz For natural stones, it is not customary to cut only a (1987). small section out of a crystal with more or less The information given in the above mentioned prismatic natural habit. Faceted natural emeralds, publications corresponds to the observations made in general, reveal growth structures of the whole by the present authors. However, it has to be rough crystals, e.g. the basal pinacoid c (0001^in underlined that the material available for this combination with six larger prism faces m {1010} investigation only consisted of faceted Gilson flux- and six smaller prism faces a {1120} as well as grown synthetic emeralds weighing up to about 5 different hexagonal dipyramids. cts. This means that only structures were observ­ In Gilson flux-grown synthetic emeralds, in able, which are characteristic for parts of the whole which part of the seed plate was still observable in rough crystal plates of Gilson synthetic emerald. the cut samples, the following different kinds of During the investigation of faceted samples, which growth structures were examined: some of the were cut out of the crystal plates described above, stones could be determined, which showed growth J. Gemm., 1991, 22, 7 435

Fig. 36 Fig. 37

Fig. 36. Growth structures in Gilson flux-grown synthetic emerald; planes parallel to the basal pinacoid c (0001) and parallel to one of the prism faces (m or a) form an angle of 90°. View perpendicular to the c-axis, the c-axis runs vertically. 30x. Fig. 37. Growth structures in Gilson flux-grown synthetic emerald; planes parallel to one of the hexagonal prism faces (m or a) are found in the seed and the overgrowth. View perpendicular to the c-axis, the c-axis runs vertically. 30x. Fig. 38. Growth structures in Gilson flux-grown synthetic emerald; planes parallel to the basal pinacoid c (0001) are found in the seed, planes parallel to one of the prism faces (m or a) are found in the overgrowth. View perpendicular to the c-axis, the c-axis runs vertically. 40x. Fig. 38 436 J. Gemm., 1991, 22, 7

planes parallel to one of the prism faces, both in the synthetic emerald seed and in the emerald over­ growth [Figure 37]. In other samples the growth structures of the seed were orientated parallel to the basal pinacoid c (0001), whereas the overgrown areas showed growth planes parallel to one of the prism faces [Figure 38]. In others, growth planes parallel to the basal pinacoid c (0001) and parallel to one of the prism faces were observed in the seed, and the additionally grown synthetic emerald showed structures parallel to one prism face [Figure 39]. In the remaining stones examined, the seed revealed one of the growth structures mentioned above, whereas in the overgrown areas both the Fig. 39. Growth structures in Gilson flux-grown synthetic emerald; planes parallel to the basal pinacoid c (0001) basal pinacoid (c) and one of the prism faces (m or a) and parallel to one of the prism faces (m or a) are found were found as growth structures. in the seed, planes parallel to one of the prism faces (m All these types of growth structures were never or a) are found in the overgrowth. View perpendicular observed in any natural emerald. Furthermore, the to the c-axis, the c-axis runs vertically. 65x. pyramidal faces M, />, and s, which are characteristic for part of natural emeralds, e.g. from Colombia or Nigeria (cf. section II), do not occur in synthetic flux-grown emeralds. An additional feature of Gil- son flux-grown synthetic emeralds are residues of flux materials which occur in zones confined to growth structures. This phenomenon is caused by growth intervals, which lead to a varying incorpora­ tion of flux in different areas of the crystal. This kind of structure is also a feature of synthetic emeralds and does not occur in natural stones.

IV. Hydrothermally-grown synthetic emeralds The most characteristic feature of hydrothermal­ ly-grown synthetic emerald is the orientation of the seed plate. According to the patents of Flanigen Fig. 40. Growth structures in Russian hydrothermally-grown synthetic emerald; residue of the seed at the culet, (1971) and Flanigen & Mumbach (1971), crystal step-like growth lines and colour zoning parallel to the growth is most efficient if seed plates are cut in an boundary colourless seed/synthetic emerald, irregular­ angle of 45° to the c-axis of the beryl. Satisfactory ly changing sub-grain boundaries. View 31° inclined to the c-axis. 34x. results were also obtained by using seed plates with angles between 30 and 60° (Flanigen, 1971) or between 10 and 60° to the c-axis (Flanigen & Mumbach, 1971). Poor crystal growth was observed when the seed plate was cut parallel to the basal pinacoid c (0001) or parallel to one of the prism faces. The orientation of the seed plate parallel to one of the prism faces was used in the experiments by Swarovski, Austria. These synthetic emeralds, however, were never produced commercially. All other commercially produced hydrothermally- grown synthetic emeralds available to the authors are made by using seed plates cut oblique to the c-axis. In faceted stones, due to this kind of orientation Fig. 41. Growth structures in Russian hydrothermally-grown of the seed plate, either residues of the seed plate synthetic emerald; step-like growth lines and colour with a distinct boundary of a seed plate versus the zoning, irregularly changing sub-grain boundaries overgrowth, or, in the hydrothermally-grown part almost perpendicular to the colour zoning. View 31° itself, dominant growth structures parallel to the inclined to the c-axis. 25x. J. Gemm., 1991,22, 7 437

Fig. 42. Growth structures in Biron hydrothermally-grown Fig. 43. Growth structures in Biron hydrothermally-grown synthetic emerald; residue of the seed [right], domi­ synthetic emerald; step-like growth line and colour nant growth line parallel to the boundary colourless zoning, irregularly changing sub-grain boundaries seed/synthetic emerald [left]. View 23° inclined to the almost perpendicular to the growth line. View 23° c-axis. Crossed polarizers. 20x. inclined to the c-axis. 5 Ox. orientation of the seed plate were detected. In Linde hydrothermally-grown synthetic emer­ alds, which were produced according to the patents mentioned above, the angles between the c-axis and dominant growth structures were measured by the present authors between 36 and 38°, which is quite a constant factor (cf. Galia, 1972). Regency hydro­ thermally-grown synthetic emeralds, which are manufactured by use of the same patents as applied for the growth of Linde synthetic emeralds (O'Donoghue, 1983), revealed angles of 38° be­ tween dominant growth structures and the c-axis [Figure 45]. A number of samples of Lechleitner hydrothermally-grown synthetic emeralds showed a variation of angles between 32 and 40° (cf. Schmetzer, 1990). Biron synthetic emeralds, on the Fig. 44. Growth structures in Pool hydrothermally-grown other hand, with angles of 22 to 23° [Figures 42,43] synthetic emerald; dominant growth line and colour as well as Pool synthetic emeralds, which are zoning. View 24° inclined to the c-axis. 22x. supposedly grown by the same hydrothermal pro­ cess (Brown & Snow, 1988; Scarratt, 1989), with angles of 22 to 24° [Figure 44], reveal a certain constancy, too. So do Russian hydrothermally- grown synthetic emeralds with quite constant angles between 30 and 32° [Figures 40, 41] (cf. Schmetzer, 1988). As a general rule, in faceted synthetic samples of all these producers or types, one dominant set of growth structures parallel to the orientation of the seed plate can be determined, which are most frequently connected with a distinct colour zoning. In addition, the oblique orientation of the seed plate is responsible for the formation of sub-grain bound­ aries (cellular structures), which have already been discussed in detail for Russian hydrothermally- grown synthetic emeralds (Schmetzer, 1988). In Fig. 45. Growth structures in Regency hydrothermally-grown general, similar or almost identical growth struc­ synthetic emerald; growth lines and colour zoning, irregularly changing sub-grain boundaries almost per­ tures were found in each commercial type of pendicular to the colour zoning. View 38° inclined to hydrothermally-grown synthetic emerald. the c-axis. 35x. 434388 JJ.. Gemm.Gemm.,, 19911991,22,7, 22, 7

DominanDominantt growtgrowthh structurestructuress iinn orientationorientationss DiehlDiehl,, R.R.,, 19821982.. MöglichkeiteMiiglichkeitenn dederr EdelsteindiagnosEdelsteindiagnosee mimitt HilfeHilfe comparablcomparablee ttoo thosthosee presenpresentt iinn hydrothermallyhydrothermally­- derder Röntgentopographie. Riintgentopographie. Zeitschrift Zeilschrift der der Deutschen Deulschen Gemmologischen Gemmolo­ grown synthetic emeralds, i.e. growth structures Gesellschaftgischen ,Gesellschaft, 31, 3-22. 31, 3-22. grown synthetic emeralds, i.e. growth structures FlanigenFlanigen,, E.E.,, 19711971.. HydrothermaHydrothermall procesprocesss foforr growingrowingg crystalcrystalss forminformingg angleangless betweebetweenn 2222 anandd 4040°° witwithh ththee optiopticc havinhavingg ththee structurstructuree ooff beryberyll iinn aann alkalinalkalinee halidhalidee mediummedium.. axisaxis,, ddoo nonott occuoccurr iinn naturanaturall emeraldemeraldss (cf(cf.. sectiosectionn United States Patent 3,567,6423,567,642.. II)II).. IInn additionaddition,, ththee growtgrowthh featurefeaturess causecausedd bbyy ththee FlanigenFlanigen,, E.E.,, MumbachMumbach,, N.R.N.R.,, 19711971.. HydrothermaHydrothermall procesprocesss foforr orientation of the seed plate are typical for these growingrowingg crystalcrystalss havinhavingg ththee structurstructuree ooff beryberyll iinn aann aciacidd orientation of the seed plate are typical for these halidhalidee mediummedium.. United States Patent 3,567,6433,567,643.. varietievarietiess ooff synthetisyntheticc emeraldemeraldss anandd cancan,, thereforetherefore,, Galia, W.,w., 1972.1972. Diagnostische Diagnostische Merkmale Merkmale synthetischer synthetischer Smaragde Smar­ bbee considereconsideredd aass a characteristiccharacteristic featurefeature ofof diagnos­diagnos­ agde vovonn LindeLinde.. Zeitschrift der Deutschen GemmologischenGemmologischen titicc value.value. GesellschaftGesellschaft,, 2121-,, 112-7.112-7. Kiefert, L., L., Schmetzer, Schmetzer, K., K.,1991. 1991. The Themicroscopic microscopic determination determina­ tion ooff structurastructurall propertiepropertiess foforr ththee characterizatiocharacterizationn ooff VV.. ConclusionConclusionss opticaopticall uniaxiauniaxiall naturanaturall anandd synthetisyntheticc gemstonegemstoness ParPartt 1I:: FrequentlyFrequently,, ththee recognitiorecognitionn ooff emeraldemeraldss ooff unun­­ GeneraGenerall considerationconsiderationss anandd descriptiodescriptionn ooff ththee methodsmethods.. knowknownn origioriginn aass naturanaturall oorr synthetisyntheticc iiss possiblpossiblee bbyy Journal of of Gemmology Gemmology,, 22 22,, 344-54. 344-54. use of characteristic growth structures. In some LindLind,, T.T.,, SchmetzerSchmetzer,, K.K.,, BankBank,, H.H.,, 19861986.. BluBluee anandd greegreenn berylberylss use of characteristic growth structures. In some (aquamarine(aquamariness anandd emeraldsemeralds)) ooff gegemm qualitqualityy frofromm Nigeria.Nigeria. casescases,, eveevenn ththee sourcsourcee ooff a naturanaturall emeralemeraldd oorr ththee Journal of Gemmology Gemmology,, 2020,, 40-840-8.. produceproducerr ooff a flux-grownflux-grown or or hydrothermally-grownhydrothermally-grown NassauNassau,, K.K.,, 19761976.. SynthetiSyntheticc emeraldemerald:: ththee confusinconfusingg historhistoryy andand synthetisyntheticc emeralemeraldd iiss unequivocallunequivocallyy determinedeterminedd ththee currencurrentt technologiestechnologies.. Journal of Crystal GrowthGrowth,, 3535,, accordinaccordingg ttoo ththee presencpresencee ooff characteristicharacteristicc growtgrowthh 211-22211-22.. NassauNassau,, K.K.,, 19801980.. Gems Made by Man. ChiltoChiltonn BookBook Company,Company, structures.structures. HoweverHowever,, thertheree araree alsalsoo distincdistinctt typetypess ofof RadnorRadnor,, Pennsylvania.Pennsylvania. growtgrowthh facesfaces,, whicwhichh araree founfoundd iinn bothboth,, naturanaturall anandd O'DonoghueO'Donoghue,, M.M.,, 1983.1983. Identifying Man-made Gems. N.A.G.N.A.G. syntheticsynthetic emeraldsemeralds.. IInn thosthosee casescases,, nnoo unequivocaunequivocall PressPress,, J.-ondon.London. determinatiodeterminationn ooff aann unknowunknownn samplsamplee bbyy meanmeanss ooff ScarrattScarratl,, 1<..,K., 1989.1989. ThThee Too'Pooll emerald'emerald:. Journal of Gemmology, 2121,297-9., 297-9. growtgrowthh structurestructuress iiss possiblepossible.. BuButt eveevenn iinn thosthosee SchmetzerSchmetzer,, K.K.,, 19861986.. AAnn improveimprovedd samplsamplee holdeholderr anandd ititss ususee inin particulaparticularr casescases,, growtgrowthh structurestructuress cacann bbee usefuusefull ttoo ththee distinctiodistinctionn ooff naturanaturall anandd synthetisyntheticc rubrubyy aass welwelll aass excludexcludee somsomee possibilitiepossibilitiess foforr naturanaturall oorr synthetisyntheticc naturanaturall anandd synthetisyntheticc amethystamethyst.. Journal of GemmologyGemmology,, 2020,, 20-3320-33.. emeraldemerald,, i.ei.e.. ttoo reducreducee ththee possibilitiepossibilitiess ttoo a limitelimitedd Schmetzer, K. K. 1988. 1988. Characterization Characterization of ofRussian Russian hydrothermally-grown hydrothermal­ numbenumberr ooff naturanaturall sourcesourcess oorr producerproducerss ooff syntheticsynthetic ly-grown synthetisyntheticc emeraldsemeralds.. Journal of Gemmology, 2121,, emeraldsemeralds.. 145-64. SchmetzerSchmetzer,, K.K.,, 1989.1989. Yellowish-greeYellowish-greenn GilsoGilsonn synthetisyntheticc emerald.emerald. Journal of Gemmology,Gemmology, 2121,, 305-7305-7.. SchmetzerSchmetzer,, K.K.,, 19901990.. TwTwoo remarkablremarkablee LechleitneLechleitnerr syntheticsynthetic emeralds.emeralds. Journal of Gemmology,Gemmology, 22,22, 20-32.20-32. Schrader,Schrader, H.-w.,H.-W., 1987.1987. NatürlicheNatiirliche und synthetische Smaragde.Smaragde. ReferencesReferences Ein Beitrag zur Kristallchemie der Beryl/e.Berylle. Dissertation,Dissertation, Brown,Brown, G.,G., Snow,Snow, J.,J., 1988.1988. TheThe PoolPool Emerald.Emerald. AustralianAustralian MainzMainz 1987.1987. Gemmologist,Gemmologist, 16,443-9.16, 443-9. Schwarz,Schwarz, D.,D., 1987.1987. EsmeraldasEsmeraldas-Inclusiies - Inclusões em Gemas. ImprensaImprensa Bukin,Bukin, G.V.,G.V., Godovikov,Godovikov, A.A.A.A.,, Klyakhin,Klyakhin, V.A.,V.A., Sobolev,Sobolev, V.S.V.S.,, UniversitáriaUniversitaria,, UniversidadUniversidadee FederalFederal dede OuroOuro Preto,Preto, OuroOuro 1980.1980. SyntheticSynthetic emerald.emerald. In:In: Gem minerals. Proceedings of Preto,Preto, Brazil.Brazil. the XI general meeting of IMA Novosibirsk 1978, publ.publ. Sinkankas,Sinkankas, J.,J., 1981.1981. Emerald and other beryls. ChiltonChilton BookBook Leningrad 1980,1980, pp.pp. 36-4436-44 [in[in Russian]Russian].. Company,Company, Radnor,Radnor, Pennsylvania.Pennsylvania. Bukin,Bukin, G.V.,G.V., Godovikov,Godovikov, A.A.A.A.,, Klyakhin,Klyakhin, V.A.,V.A., Sobolev,Sobolev, V.S.,V.S., Ushio,Ushio, M.,M., 1977.1977. AppearanceAppearance andand disappearancedisappearance ofof CrystalCrystal 1986.1986. GrowthGrowth ofof emeraldemerald singlesingle crystals.crystals. Growth of Crystals FacesFaces ofof EmeraldEmerald duringduring CrystalCrystal GrowthGrowth byby VV,O,2O5 FluxFlux 13,251-60.13,251-60. Method.Method. Journal of Gemmological Society of Japan, 4,4, 51-951-9 Diehl,Diehl, R.,R., 1977.1977. NeuesNeues zumzum ThemaThema "Synthetischer"Synthetischer Smaragd":Smaragd": [in[in Japanese].Japanese]. Besuch bei bei Pierre Pierre Gilson. Gilson. Zeitschrift Zeilschrifl der der Deutschen Deulschen Gemmologischen Gemmolo­ gischenGesellschaft Gesellschafl,, 26, 61-75. 26, 61-75. [Manuscript[Manuscript receivedreceived 3 3 May May 1989.]1989.] J. Gemm., 1991, 22, 7 439

Gemmological Abstracts

ALLEN, R.M., 1991. The Yogo sapphire There is a short bibliography. M.O'D. deposit. Gemmological Digest, 3, 2, 9-16. 13 photographs in colour, 2 maps, 1 fig. BLANKENSHIP, D.T., 1989. Orange peel. Bulletin Recent work on the Yogo sapphire deposit in of the Friends of Jade, 6, 81-3. Montana, USA, may make the various colours of The surface of nephrite is discussed from the corundum more available on the market. Short Point of view of the lapidary. The 'orange peel' notes on the geology and mining history are given. effect was not apparently a feature of the nephrite Rutile is one of the reported inclusions and the from eastern Turkestan. M.O'D. best stones rank with some of the finest from other sources. M.O'D. BOGDANOVIC, K.I., 1989. Nephrite deposits in the Kuen-Lun mountains. Bulletin of the Friends ATHINEOS, D., 1991. The orchid of the mineral of Jade, 6, 74-80. kingdom. Christie's International Magazine, 8, 3, Nephrite deposits in eastern Turkestan are 20-2, 5 figs in colour. described. All in situ deposits are situated in high A short but well-illustrated and accurate mountain areas which are difficult to reach. account of coloured diamonds, many of which M.O'D. have passed through the saleroom. Up-to-date information on colour alteration is given. M.O'D. BOSSHART, G., 1990. Il verde di Dresda*. La Gemmologia, 15,1/2, 7-21, 6 photographs in BARNES, L.C., BECK, R.J., LEAMING, S.F., TAN, colour, 1 fig. L.-P., 1988. World review of nephrite jade - The Dresden Green diamond is investigated geology, production and reserves. Bulletin of the and found to weigh approximately 41 ct and to Friends of Jade, 5, 14-69, 6 maps. belong to Type Ha. Some areas display anomalous Nephrite is produced in at least 46 countries birefringence and the stone is well cut to ideal pro­ but commercial output is restricted to Canada, portions. M.O'D. Taiwan, New Zealand, Australia, China, USA and Korea. World production of nephrite, exclu­ BOSSHART, G., 1991. Les emeraudes de sive of China, amounts to an average of 780 Colombie. Revue de Gemmologie, 106, 19-24, tonnes a year since 1962. China may produce as 12 photographs in colour, 4 figs. much as 500 tonnes a year; Taiwan production This part of the paper describes absorption, has ceased. A shortage of nephrite is expected to colour and fluorescence, optical constants, den­ be relieved by production from the Cowell field in sity, inclusions and growth features. Some char­ Australia or by increased use of simulants. acteristic inclusions are illustrated. M.O'D. Commercial deposits are surveyed with a view to estimating future production. Considerable geo­ BRACEWELL, H., 1991. Gems around Australia. logical detail is given. There is a most useful bib­ Australian Gemmologist, 17, 9, 377-8, 6 figs. liography. M.O'D. Mrs Bracewell continues her account describ­ ing further scenes, finds and adventures in the BECK, R.J., 1988. Jade of the Pacific. Bulletin of the Bracewell circumtouring of that Continent early Friends of Jade, 5, 75-8. in the 1980s. She describes Northern Australia, The article describes a visit to China and to the finding ribbonstone, prehnite and amethyst. Uygur Autonomous Region, Taiwan and South R.K.M. Korea. M.O'D. BROWN, G., 1990. A rare baler shell pearl. BLANKENSHIP, D.T., 1988. The sawing of jade. Australian Gemmologist, 17, 8, 307-8, 5 figs. Bulletin of the Friends of Jade, 5, 70-4. The various methods used for jade sawing are ^Translation of a paper first published in Schweizer Uhren-und described with notes on the Chinese terms used. Schmuck, 1989,2,513-19. 440 J. Gemm., 1991, 22, 7

Found in the large melo amphora shell, which chrome spectrum and is green through the can reach 50cm in length, this rare 68.97 ct non- Chelsea filter; sunstone quartz from Tingha near nacreous pearl is pinkish-orange in colour with a Inverell, NSW, thought to be due to included flame pattern reminiscent of that seen in pink hematite plates, is described. [The figures in this conch pearls, SG 2.83, DV/RI value 1.67, inert to paper are again numbered in separate groups and UV and no visible absorption. R.K.M. there is misuse of the word 'including'. An inclu­ sion should not be said to be 'including' the host BROWN, G., 1991. Some Australian turquoise mineral.] R.K.M. deposits. Australian Gemmologist, 17, 9, 369-73, 4 figs. BROWN, G., KELLY, S.M.B., BEATTIE, R., 1991. Turquoise occurs in almost every state, but lit­ Gemmological Study Club Lab reports. tle of it is of finequality . R.K.M. Australian Gemmologist, 17, 9, 363-7, 13 figs. Deals with Hong Kong dyed and waxed BROWN, G., BEATTIE, R., SNOW, J., 1991. jadeite; a coated (heated) sapphire; cerussite; Verneuil synthetic red spinel. Australian prawn-claws as earrings; pipi blister pearls from Gemmologist, 17, 9, 344-7, 6 figs. Cook Island; carved bone from India and red Hitherto a difficult synthetic to find, this is now Kauri gum. [The idiosyncratic numbering of fig­ apparently in circulation in fragmented form in ures in these reports is confusing. In this one there Australia and USA. RI 1.720, SG 3.59 and strain are seven with the number 1. Can editor not do free between crossed polars, fluorescing like natu­ something to rationalize this.] R.K.M. ral stone and with identical absorption/emission spectra, these stones need close examination under magnification to reveal characteristic inclu­ BROWN, G., KELLY, S.M.B., SNEYD, R., 1990. sions of curved growth banding, tadpole and pro- Russian flux-grown synthetic spinel. filated bubbles [these writers persist in calling Australian Gemmologist, 17, 8, 315-17, 10 figs. these 'proliferated', a term which has quite a dif­ A specimen of this fairly new synthetic red ferent meaning from that intended by Anderson spinel was purchased in Hong Kong and con­ when he coined the new word]. It is not known formed very closely in constants with similar octa­ whether these are old stock or a new production. hedral crystals described elsewhere. Etch (growth?) marks and triangular dissolution edges R.K.M. and marks on the octahedral faces, adhérant octa- hedra, dark flux, platinum flakes, air-filled curved BROWN, G., CHAPMAN, J., 1991. Argyle cham­ fractures and dendrites were seen. Authors con­ pagne and cognac diamonds. Australian clude that if a visually clean stone could be cut Gemmologist, 17, 9, 350-1, 1 fig. from such material, it would be identical with nat­ A brief résumé of occurrence, colours and qual­ ural red spinel, undetectable by normal tests. ities. R.K.M. R.K.M. BROWN, G., KELLY, S.M.B., BEATTIE, R., BRACEWELL, H., 1990. Gemmology Study BROWN, G., KELLY, S.M.B., SUTHERLAND, C, Club report. Australian Gemmologist, 17, 8, CALLAWAY, P., 1990. Imitation chicken-blood 325-32, 20 figs badly numbered. stone. Australian Gemmologist, 17, 8, 311-13, 5 A ruby/sapphire combined in one crystal; mas­ figs. sive stichtite, a rare ornamental material from A visually effective imitation of this Chinese Tasmania, are described. A mounted suite of 10 valued material was detected by warmth to touch, large orange sapphires was found to be yellow syn­ bubbles in cinnabar imitation and coating, and thetic corundum diffusion treated with synthetic strong fluorescence to LUV. The grey base mate­ ruby; bought for US$35 in Srinagar, Kashmir, one rial is described as soapy to the touch, while the wonders at the economics of the deal [and even coloured coating had a waxy feel; both peeled more that the purchaser should need them val­ readily. R.K.M. ued]; diffusion-treated synthetic blue sapphire with curved colour zones has been seen. A glass BROWN, G., LINTON, T., 1991. An inexpensive imitation of aquamarine spalled after cutting, conversion unit. Australian Gemmologist 17, 9, while another was made from photo-sensitive glass 355, 1 fig. of the type used for sun-glasses. Emerald from A metal base which allows a Kiowa microscope 'Harry's Mine' near Torrington, NSW, is shown to be turned through 90° for horizontal examination to be green beryl rather than emerald, it has no of immersed stones. R.K.M. J. Gemm., 1991, 22, 7 441

BROWN, G., TOMBS, G., 1991. An introductory CHANCERED C., 1991. Bloody opals ...! Revue de note on the manmade products of Dominique Gemmologie, 106, 3-7, 20 figs (6 in colour). Robert. Australian Gemmologist, 17, 9, 381-2, 5 A brief account of mining and cutting opera­ figs in colour. tions at the Australian field of Lightning Ridge, Emeraldolite is a synthetic druse of emerald New South Wales. Some personal cutting experi­ coated onto a large crystal or other base of natural ences are described. M.O'D. beryl. Heat whitens and opacifies the seed mate­ rial. Oulongite is another synthetic 'garnet', for­ CLUNAS, C., 1989. Jade carvers and their cus­ mula unspecified; colours so far white, blue, tomers in Ming China. Bulletin of the Friends of green, pink. H about 7.5, SG 6.9, RI 1.93-1.99, Jade, 6, 33-52, 7 figs. Disp. 0.030. R.K.M. Jade carving in China between Han dynasty and the eighteenth century is examined. There is CAIRNCROSS, B., 1991. The Messina mining dis­ a useful bibliography. It is interesting that the con­ trict, South Africa. Minerahgical Record, 22, 3, noisseurs of the Ming period did not appear to 187-99, 12 photographs (8 in colour), 11 maps regard jade as highly for its tactile qualities as has and plans. been thought. M.O'D. Quartz crystals coloured sky blue by inclusions of ajoite and measuring up to 5cm in length are DYAR, M.D., PERRY, C.L., REBBERT, CR., reported from the Messina mining area, northern DUTROW, B.L., HOLDAWAY, M.J., LANG, Transvaal, South Africa. M.O'D. H.M., 1991. Mossbauer spectroscopy of syn­ thetic and naturally occurring staurolite. American Mineralogist, 76, 27-41, 7 figs. CAMPBELL, I.C.C., 1991. A report on one of a Room temperature Mossbauer spectroscopy of number of emeralds from Madagascar. South 23 natural and 12 synthetic staurolites showed African Gemmologist, 5, 1, 8-15, 7 figs in colour. that the majority of the Fe in all samples is Fe2*. Large emeralds from Madagascar have been This occupies the Fel, Fe2 and Fe3 subsites of seen in the South African gem market. SG is the tetrahedral Fe site in an average ratio of reported as 2.73-2.74, RI 1.585, 1.591, 1.593 43/12/27. M.O'D. [sic] (a previous study gives 1.589-1.591 for the ordinary ray and 1.581-1.585 for the extraordi­ FREY, R., 1989. Satellite scans: technical notes nary ray). Birefringence is reported by the earlier and gazetteer. Bulletin of the Friends of Jade, 6, study as 0.006-0.008. Stones are inert to UV and 60-1, 1 fig. show strong yellowish-green and strong greenish- A satellite photograph shows the nephrite blue dichroism. The cabochon examined con­ source of the Karakash River. A short gazetteer tained goethite, limonite, hematite and colour gives some of the places shown. M.O'D. zoning, as the previous report stated. In addition phlogopite was identified and the stone may have been oiled. Biotite, muscovite, apatite, quartz, FRYER, C.W., Ed., CROWNINGSHIELD, R., HUR- tourmaline and two-phase inclusions could not be WIT, K.N., KANE, R.E., HARGETT, D., 1990. identified with the limited equipment available, Gem Trade Lab notes. Gems & Gemology, 26, though they featured in the previous report. The 4,294-9, 17 figs.. strongest absorption was in the region of 680nm Collection quality mineral specimens of azurite and diffuse bands were noted in the region from were examined including exceptional ones from 650-640nm. There was moderately strong absorp­ Chessy, France and Bisbee, Arizona; the latter tion of the orange-yellow from approximately 630- with rosettes of azurite on a back-ground of mala­ 570nm. No absorption was noted in the blue chite [most beautiful!]. A yellow zirconia was region. Under the colour filter the stone gave a found matched with a yellow diamond in a ring, slightly reddish colour with a dull and dark and had absorption lines at about 453 and 478nm, appearance. M.O'D. normally belonging to Cape diamonds. Intense yellow marquise diamonds in a brooch were prob­ ably proved by fluorescence and absorption to be CAMPBELL, I.C.C., 1991. Fine quality large cut natural, but were very like Sumitomo synthetics in opal. South African Gemmologist, 5, 1, 22, 1 fig. appearance. Another diamond shown to be irradi­ in colour. ated green by the 'umbrella' around the culet, but A fine quality white opal measuring 28.62 x had additional dark zoning. 21.92 x 9.74mm and weighing 35.16 ct is Dyed black cultured pearls fluoresced a distinct described and illustrated. M.O'D. yellow under LUV and a tellurium dye was sus- 442442 JJ.. Gemm.Gemm.,, 1991,22,71991, 22, 7

pected.pected. BoutonBouton culturedcultured pearlspearls hadhad lentillentil shapedshaped Diffusion-treatedDiffusion-treated corunducorundumm iiss discussediscussedd withwith nu~lei,nuclei, 110tnot usedused muchmuch becausebecause tendtend toto killkill thethe oys­oys­ illustrationsillustrations ooff treatedtreated stonesstones anandd notenotess oonn identi­identi­ ter.ter. fication. TheThe historhistoryy andand somesome ooff thethe politicpoliticss ooff A rubyruby withwith a glassglass infillinfill hadhad notnot beenbeen firedfired ttoo thethe methodmethod araree alsalsoo discusseddiscussed.. M.O'D.M.O'D. a highhigh temperature.temperature. TheThe glassglass fluorescedfluoresced chalkychalky yellowyellow inin LUVLUV andand containedcontained bubbles.bubbles. A syntheticsynthetic HUGHES,HUGHES, RW.,R.W., SERSEN,SERSEN, W.J.W.J.,, 1991.1991. VietnameseVietnamese rubyruby cabochoncabochon hadhad alsoalso beenbeen glass-filledglass-filled wherewhere ruby.ruby. Gemmological Digest, Digest, 3,3 ,2, 2 , 68-70,68-70, 77 pho­ pho­ damageddamaged andand wewe areare warnedwarned toto looklook outout forfor bub­bub­ tographstographs inin colour,colour, 1 mapmap.. blesbles inin thethe glassglass andand curvedcurved striaestriae inin the the ruby.ruby. A FineFine qualitqualityy rubrubyy iiss reportereportedd frofromm LucLuc Yen,Yen, syntheticsynthetic sapphiresapphire containedcontained prominentprominent lineslines ooff Vietnam,Vietnam, a sitesite abouaboutt 150km150km north-wesnorth-westt ooff Hanoi.Hanoi. tinytiny bubblesbubbles whichwhich lookedlooked likelike needlesneedles [illustration[illustration StonesStones resemblresemblee BurmeseBurmese materiamateriall iinn coloucolourr andand showsshows thatthat thesethese werewere notnot atat thethe requiredrequired inclina­inclina­ strongstrong fluorescence.fluorescence. M.O'D.M.O'D. tiontion ofof 120°];120°]; striaestriae andand curvedcurved colourcolour zoneszones werewere lessless obvious.obvious. RobertRobert KaneKane sayssays a darkdark blueblue filter HUTTON,HUTTON, D.R.D.R,, TROUPTROUP,, G.J.,G J., 19901990.. ESESRR specspec­­ overover a transmittedtransmitted lightlight sourcesource makesmakes curvedcurved striaestriae trumtrum ooff AustraliaAustraliann synthetisyntheticc BironBiron emerald.emerald. andand bubblesbubbles easiereasier toto seesee inin yellowyellow andand orangeorange Australian Gemmologist, 17,17 ,8, 8 ,299-301, 299-301 , 55 dia­ dia­ syntheticsynthetic sapphires,sapphires, normallynormally quitequite difficultdifficult stonesstones grams.grams. toto identify.identify. A largelarge piecepiece ofof blueblue materialmaterial hadhad RRII Electron-spinElectron-spin resonancresonancee ofof thisthis neneww syntheticsynthetic 1.56,1.56, H aboutabout 2¥2,2V2, SGSG belowbelow 2.57,2.57, eliminatingeliminating isis demonstrateddemonstrated inin diagramdiagramss ooff spectrspectraa [Figure[Figure 3 turquoiseturquoise whichwhich itit waswas apparentlyapparently intendedintended ttoo hashas thethe wronwrongg captioncaption]] anandd suggestsuggestss thatthat ththee resemble.resemble. AcidAcid revealedrevealed carbonatecarbonate plusplus a plasticplastic materialmaterial iiss ooflaserf laser quality.quality. [Interpretation[Interpretation isis notnot binder.binder. RK.M.R.K.M. easyeasy forfor thethe uninitiated.uninitiated.]] RK.M.R.K.M.

HOCHLEITNER,HÖCHLEITNER, R,R., WEISS,WEISS, S.,S., 1991.1991. NeueNeue miner­miner- KAMMERUNG,KAMMERLING, R.C.RC.,, KANE,KANE, RE.,R.E., KOIVULAKOIVULA,, J.I.J.I.,, alfundealfunde ausaus PakistanPakistan undund Mghanistan.Afghanistan. Lapis, MCCLURE,MCCLURE, S.F.,S.F., 1990.1990. AAnn investigationinvestigation ofof a 16,3,16, 3, 15-16,315-16, 3 figsfigs (2(2 inin colour).colour). suitesuite ofof blacblackk diamondsdiamonds.. Gems & Gemology, 26,26 , StibiotantaliteStibiotantalite andand tremolitetremolite areare describeddescribed from 4,74, 7 figs.figs. $tak-NalaStak-Nala inin PakistanPakistan andand fromfrom Nuristan,Nuristan, SixSix quitequite larglargee mountedmounted blacblackk diamonddiamondss werewere Mghanistan,Afghanistan, respectively.respectively. FromFrom thethe illustrationsillustrations examinedexamined forfor transparentransparentt dardarkk greengreen areaareass whichwhich thethe qualityquality approachesapproaches thethe ornamental.ornamental. ThThee wouldwould indicateindicate artificialartificial irradiation.irradiation. MinutMinutee transtrans­­ stibiotantalitestibiotantalite isis yellowyellow andand occursoccurs withwith tourma­tourma­ parentparent areaareass inin thesthesee stonesstones werweree whitwhitee oror blue.blue. lineline andand albite.albite. TheThe tremolitetremolite isis whitewhite andand resem­resem­ FacetsFacets werweree pittepittedd anandd polishinpolishingg dragdrag lineliness werewere blesbles AlpineAlpine adularia.adularia. M.O'D.M.O'D. prominent,prominent, aass witwithh mosmostt blacblackk diamonds.diamonds. ColourColour waswas duedue ttoo graphitegraphite.. NNoo distincdistinctt absorptionabsorption lineslines HODGKINSON,HODGKINSON, A.,A., 1991.1991. PadparadschaPadparadscha - whatwhat iiss oror bandsbands werweree seenseen.. TwTwoo stonestoness showingshowing blueblue meantmeant byby thisthis term?term? Australian Gemmologist, transparenttransparent areasareas fluorescedfluoresced stronstrongg blubluee underunder 17,9,378-80,317, 9, 378-80, 3 figs.figs. LVVLUV andand greengreen iinn SVVSUV anotheanotherr stonestone gavgavee aa DiscussesDiscusses variousvarious versionsversions ofof orange/pinkorange/pink chalkychalky mottlemottledd yellowish-greenyellowish-green.. AlAlll thethe blackblack corundumcorundum soldsold underunder thisthis andand similarsimilar names,names, andand stonesstones hahadd beebeenn cementedcemented intointo theitheirr settings.settings, thethe ruby/pinkruby/pink sapphiresapphire question,question, goinggoing onon toto probablyprobably iinn deferencedeference toto ththee manymany cleavagescleavages whichwhich includeinclude syntheticsynthetic padparadschas,padparadschas, whichwhich areare byby farfar mademade thethe stonestoness vulnerablvulnerablee ttoo settinsettingg pressures.pressures. thethe commonestcommonest ofof thisthis name.name. RK.M.R.K.M. ThermalThermal conductivityconductivity wawass normanormall forfor diamond.diamond. A detaileddetailed listlist ooff possiblpossiblee simulantsimulantss isis givengiven.. HUANG,HUANG, V.T.,U.T., AUNG,AUNG, Z.,Z., HTEIN,HTEIN, W.,W., 1991.1991. RK.M.R.K.M. RadioactivityRadioactivity inin somesome mineralsminerals inin thethe MogokMogok area.area. Australian Gemmologist, 17,17, 9,9, 356-9,356-9, 2 KAMMERLING,KAMMERLING, R.C.,R.C., KOIVULA,KOIVULA, J.I.,J.I., 1991.1991. figs. ExaminationExamination ooff a plastiplasticc coatedcoated 'suga'sugarr treatedtreated'' ResearchersResearchers foundfound moremore uraniumuranium inin zircon,zircon, opal.opal. Australian Gemmologist, 17,9,352-5,417, 9, 352-5, 4 andand moremore thoriumthorium inin sphene,sphene, thanthan inin apatite.apatite. AAnn figs. eruditeerudite scientificscientific paperpaper havinghaving littlelittle toto dodo withwith thethe SubmittedSubmitted foforr investigationinvestigation byby JohnJohn FuhrbachFuhrbach gemgem potentialpotential ofof thesethese stones.stones. RK.M.R.K.M. ofof Amarillo,Amarillo, thisthis stonestone hahadd beebeenn boughboughtt aass blackblack opalopal atat highhigh cost.cost. ItIt isis aa dyeddyed (sugar/acid(sugar/acid treated)·treated) HUGHES,HUGHES, RW.,R.W., 1991.1991. There'sThere's a rumblerumble inin thethe stonestone whichwhich hahadd alsalsoo beebeenn coatedcoated witwithh plastic,plastic, junglejungle - the'the1 sapphiresapphire face-liftface-lift face-offface-off saga.saga. causingcausing anomalouanomalouss fluorescencefluorescence andand manymany Gemmological Digest, 3,3, 2,2, 17-28,17-28, 1111 figsfigs iinn includedincluded bubblesbubbles.. RK.M.R.K.M. colour.colour. J. Gemm., 1991, 22, 7 443

KAMMERLING, R.C., KOIVULA, J.I., 1991. Opals is usually described as apple green; the team call it displaying cat's-eye effects.South African 'fancy green', photographs of the actual stone Gemmologist, 5, 1, 23-7, 3 figs in colour. published here suggest lightish yellow-green. A number of natural opals show chatoyancy. Graining was seen in three directions and polar- Idaho opal mounted as composites show chatoy­ iscope revealed considerable cross-hatched strain; ancy and in this case the phenomenon is a powerful source of UV revealed weak green flu­ attributed to planar faults in the stacking of the sil­ orescence. Natural radiation damage was evi­ ica spheres. An opal whose chatoyancy is denced by small green or brown stains at three attributed to light reflection from parallel acicular places near the girdle, but do not cause the body inclusions is described. Since the stone showed a colour. No distinct spectrum at normal tempera­ weak pleochroism its origin may have been as a tures but low temperature spectroscopy revealed a pseudomorph after a biréfringent fibrous mineral general radiation pattern, with absorption lines at such as goethite. M.O'D. 594, 495, 470, 310, 393, and a cut-off at 225nm. There are similarities with a known radiation- KAMMERLING, R.C., KOIVULA, J.I., FRTTSCH, E., treated stone. Further details are given, but 1990. An examination of Chrysoprase from 594nm is considered to indicate a treated stone, Goias, Brazil. Australian Gemmologist, 17, 8, yet the Dresden was known long before such treat­ 313-15, 2 figs. ment was available. Infrared absorption spectra The pale yellowish green to dark vivid green is suggest the stone is a Type Ha diamond, and this probably due to nickel in the form of bunsenite. leaves the question of separating natural from arti­ RI 1.539, SG 2.64. Rather strangely a quite ficially treated green Type Ha diamonds wide marked greenish-blue fluorescence in LUV, and open. R.K.M. fainter in SUV, have apparently not been previ­ ously noted. R.K.M. KEVERNE, R., 1988. Worldwide view of the jade market, 1986. Bulletin of the Friends of Jade, 5, KANE, R.E., MCCLURE, S.F., MENZHAUSEN, J., 7-13. 1990. The legendary Dresden Green diamond. Details of jade pieces sold at auction are given Gems & Gemology, 26, 4, 248-66, 16 figs. (hammer prices excluding the 10% commission A very full investigation of this historic 41 ct levied on the buyer). Sales conducted by Christie's diamond by a team which visited Dresden espe­ and Sotheby's are covered worldwide. Jadeite ves­ cially for the purpose. Photographs reproduced sels were strong performers over the year and good show the stone in a recently drawn reconstruction qualities did well while sub-standard pieces failed as part of the order of the Golden Fleece, which is to attract buyers. Jewellery of the best colours did also used as the front cover of this issue of the well. M.O'D. journal. Others show a glass copy and the stone itself, which registers as paler than either the copy KEVERNE, R., 1989. Worldwide view of the jade or the drawing. market 1987 (1988). Bulletin of the Friends of The history of the stone is researched with care Jade, 6, 8-19 (20-32). and it seems certain that the rough came from Considerable enthusiasm exists, on the basis of India, since Brazilian diamonds were discovered the Christie's and Sotheby's sales in the two years only a year or so earlier. It was cut, probably in reviewed, for high quality jade artefacts. The 1988 London, shortly afterwards and in 1742 was season in particular was the most successful since incorporated in the Fleece badge only to be bro­ the early 1970's. Fine jewellery and good white ken up four years later, when it was used in a sec­ carvings were in strong demand. M.O'D ond version which also included the 49.71 metric carat Saxon White diamond. [Two weights are KOIVULA, J.I., 1990. Snail shells in amber. given for this stone, the first being in pre-metric Australian Gemmohgist> 17, 8, 309-10, 2 figs. carats.] The badge was again dismantled in 1768 In common with other animals and plants in and Dissbach commissioned to fashion the centre amber from the Dominican Republic, these lern part into a shoulder knot and a hat ornament, spiral (pulmonata) snail shells are remarkably well both of which exist today, the Dresden Green preserved for forty million years old. Author says being transferable. that one area of Panama has an estimated snail The present team investigated the stone very population today of over seven million snails per thoroughly, and report on shape, cut, proportions, acre, mostly of sizes suitable for such entrapment. finish, clarity and colour. Finish and symmetry are [He also says that most snails serve as scavengers very good and transparency is exceptional. Colour of dead plant and animal matter. The million or 444 J. Gemm., 1991, 22, 7

so in my garden are much braver and tackle living Aqua Aura treatment of quartz can also use silver plants with considerable appetite!] These two are or platinum which do not colour the crystal but small, the larger about 1cm in length. R.K.M. leave the surface iridescent; synthetic sapphire cabochons are being 'improved' by matt surfacing KOIVULA, J.I., KAMMERLING, R.C., 1990. Gem the backs to reduce transparency; Thailand is now news. Gems & Gemology, 26, 4, 300-9, 16 figs. cutting CZ for the US; glass imitations of Imperial Diamonds jadeite are described and illustrated; pectolite is De Beers have grown a 14.2 ct good quality imitated by blue Imori stone (glass); dyed quartz industrial yellow stone thought to be the largest sold as purple onyx in Indian jewellery in the yet, but not commercially viable; only industrials States seems to be a micro-version of crackled are aimed at in such experiments. Nearly half the quartz with a strong resemblance to sugilite. China-cut diamonds offered in Singapore were R.K.M. sold; development and exploration of diamond mining in Guyana has been agreed. KROSCH, N.J., 1990. Queensland Chrysoprase. Coloured stones Australian Gemmologist, 17, 8, 303-6, 2 figs, 2 Vast gold reserves found in Afghanistan, with maps. gem mining, this is expected to attract foreign The exceptionally fine Marlborough Chryso­ investment; cat's-eye opal triplets, synthetic prase, sometimes incorrectly called Queensland corundum stars and quartz cabochons backed jade, has been known for more than thirty years. with computer chips are among new assembled Mined by open-cast method from nickel-ferrous stones; black coral is being exploited in the serpentines. Gemmological details are not quoted. Mexican Caribbean; heavy excavating equipment R.K.M. is being used in Kanchanaburi sapphire mines; a peace pact has been signed between warring fac­ LEAMING, S., 1989. From the mines in the moun­ tions in the Colombia emerald area, and produc­ tains to the rocks in the river. The development tion is expected to increase; an unusual African of alluvial jade deposits from jade lodes. grossular garnet was parti-coloured yellowish Bulletin of the Friends ofJade> 6, 63-8, 1 fig. brown and orange with different RI (1.38, light, The movement of nephrite from in situ and 1.4 darker area). deposits to alluvial finds is discussed. The equa­ Australian research is investigating use of safe tion heavy organic water-soluble compounds for min­ r eral separation; a black cat's-eye opal from Mexico EdxR is described and illustrated; a 14 x 10 cm gem quality opal found at Boi Morto Mine, Brazil, was where T is the time in years taken for a block to brownish white in colour with pinfire on all sur­ travel, D the distance between two locations, W faces; a 16.39 ct cobalt spinel of violet-blue colour the weight of the block, E^ the difference in ele­ in fluorescent light, turned purple under incan­ vation between the two locations, C a constant descent light, RI 1.714, red through Chelsea filter, specific to nephrite, R the roundness of the block chalky-red in LUV, strong fluorescent line at and Ur the rate of uplift is postulated. The case in 686nm weaker one at 552 and broad diffuse question covers the distance between the mines at absorption at 454-46lnm; a large light bluish- Shahidulla to the oasis of Khotan. M.O'D. green topaz sculpture weighing about 35000 ct has been cut from part of a 79 lb crystal bought by LlNTNEk, B., 1988. Along Burma's jade trail. Edward Swoboda in the 1950s, polishing large Bulletin of the Friends ofJade3 5, 81. facets gave a lot of trouble in the final stages; cat's- A reprint of an article in The Far Easatern eye red/blue tourmaline had tubular inclusions in Review in 1987 describing the difficulties of work­ the blue section only, skilled cutting retained the ing the Jade Tracts in Myitkina, Burma. M.O'D. 'eye' at the junction of the two colours; a Welsh firm has exclusive agreement with USSR geology LINTON, T., BROWN, G., 1990. Presidium ministries to attract foreign interest in gem min­ MiniMate. Australian Gemmobgist3 17, 8, 318- ing; waxing of jades was described and illustrated 20, 3 figs. in a Hong Kong magazine. Another well-designed and reliable heat-probe Enhancements for testing mounted diamonds. Usual precautions Robert Crowningshield showed that techniques must be taken in use. R.K.M. to detect colour diffusion treatment in loose sap­ phires can work equally with mounted stones; LINTON, T., BROWN, G., 1990. Presidium J. Gemm., 1991,22,7 445

DiaMeter - System Berger. Australian West Sri Lanka. Australian Gemmologist, 17, 9, Gemmologist, 17, 8, 301-6, 3 figs. 347-9 and 351, 4 figs. A slide rule for diameter/weight calculations for A gneissic region with rich sources of alluvial well-made round diamonds, combined with an gems including chrysoberyl cat's-eyes, alexandrite, electronic version of the Leveridge gauge. rose quartz, hessonite and other gem species. Combination works well for stones of good make. Yield increases as the Singharaja Hills are R.K.M. approached suggesting that these are the primary source. R.K.M. LINTON, T., BROWN, G., 1991. The gold-meter. Australian Gemmologist, 17, 9, 360-2, 2 figs. ROBERT, D., 1991. Emeraldolite (letter). An assessment of a new electro-chemical meter Australian Gemmologist, 17, 9, 381-2. for testing gold which proved accurate for quali­ An answer to A. Taylor's letter, claiming that ties up to 18ct, but did not specify quality above colourless beryl is an excellent foil for the artificial that. Needs to be used with care. [An obsolete druse of synthetic emerald. R.K.M. address of Gemmological Instruments Ltd is quoted.] R.K.M. ROBERT, D., FRITSCH, E., KOIVULA, J.I., 1990. Emeraldolite: a new synthetic overgrowth on MAAS, H.H., 1991. Museen in Westdeutschland. natural beryl. Gems & Gemology, 26, 4, 288-93, (Museums in West Germany.) Aufschlüsse 42, 7 figs. 2, 29-40. A product rather similar to Lechleitner coated A useful list of museums in West Germany with emeralds, but opaque in this case, and different in geological, mineralogical or fossil collections technique from the Lennix process, since fluorine arranged in alphabetical order of place. The name is used as the transport agent. Emerald layer grows of the director is given together with hours of open­ in conformity with the substrate crystal, giving ing, telephone number, postal address and main even coloration. Spot RI 1.56, SG 2.66. No UV theme of the collections. M.O'D. fluorescence or phosphorescence. There were numerous surface specks of white which were MONTGOMERY, R.S., 1991. In the dark: separat­ thought to be lithium feldspar. Intense red ing synthetic and natural gems by ultraviolet through Chelsea filter, no surface cracking. spectroscopy. Gemmological Digest, 3, 2, 45-53, Unique appearance makes identifying easy. 18 figs (17 in colour). Generally used unpolished, but can be polished or The Krüss UVS 2000 is evaluated. Significant carved. R.K.M. differences were noted between the spectra of the following pairs: natural and synthetic ruby, heated SCHLUESSEL, R., 1991. Des saphirs étoiles syn­ and unheated rubies, natural and synthetic blue thétiques ... pas comme les autres. Revue de sapphires, heated and unheated blue sapphires Gemmologie, 106, 10-12, 12 figs in colour. and natural and synthetic red spinels. M.O'D. Several methods of distinguishing natural from synthetic star sapphires are outlined. Inclusions characteristic of the synthetic material are illus­ PEARSON, G., 1990. Multiple chatoyancy in trated. M.O'D. Australian sapphire. Australian Gemmologist, 17, 8, 296-8, 8 figs. SCHUHBAUER, E., 1991. Bemerkenswerte An interesting account of 12-ray asterism in a Neufunde von Roten Beryllen in den Wah- cabochon sapphire from Rubyvale in Queensland, Wah Mountains, Utah. Lapis, 16, 6, 38,4 pho­ thought to be due to rutile (diffuse white star) and tographs in colour. ilmenite (intersecting bronze coloured star show­ Fine red beryl crystals are reported from the ing additional reflective centres). [This is asterism southern Wah-Wah Mountains in Beaver County, not chatoyancy.] R.K.M. Utah, USA. The find of particularly good crystals was made in August 1990 at the Violet Claims. PEILE, J., 1988. Trouble at the mines. Bulletin of M.O'D. the Friends of Jade, 5, 81. A reprint of an article in The Times of London SCHWIEGER, R., 1990. Diagnostic features and in 1893 describing the difficulties of working the heat treatment of Kashmir sapphires. Gems & Jade Tracts in Myitkina, Burma. M.O'D. Gemology, 26, 4, 267-80, 24 figs. A well-researched paper which serves to distin­ PEMADASA, T.G., 1991. Gem deposits of South guish the rare and very lovely Kashmir sapphire 446 J. Gemm., 1991, 22, 7

from those fine stones from Burma or Sri Lanka, TANG, S.M., TANG, S.H., MOK, K.F., RETTY, which are often called 'Kashmir' in ignorance. A.T., TAY, T.S., 1991. A study of natural and Typical silk and other inclusions are illustrated, synthetic rubies by PDŒ. Gemmobgical Digest, and the unique absorption recorded by spec­ 3, 2, 63-7, 2 photographs in colour, 2 figs. trophotometer is compared with those of stones Proton-induced X-ray emission is used to from other sources. Kashmir sapphires are examine 160 natural and synthetic rubies. markedly different in the blue-violet region, while Vanadium and iron are found in the natural stones comparison with heated Sri Lankan stones Was rather than in the synthetic ones. M.O'D. even more marked. But a Kashmir sapphire, sim­ ilarly heated, became lighter in colour, some TANG, S.M., TANG, S.H., TAY, T.S., RETTY, 'snowflake' inclusions dissolved and some areas A.T., 1991. Analysis of Burmese and Thai became colourless. The spectrum also changed rubies by PDŒ. Gemmobgical Digest, 3, 2, 57- and became much more like that of a Sri Lankan 62, 2 photographs (in colour), 2 figs. sapphire. Unheated Kashmir stones can probably Proton-induced X-ray emission techniques are be identified with some certainty, but once heated used to identify trace elements in 60 Burmese and they may lose colour and identifying characteris­ Thai rubies. Burmese stones were found to con­ tics. R.K.M. tain higher concentrations of all impurities except iron. They also show a higher concentration of SERSEN, W.J., 1991. Gemstones and early Arabic vanadium than Thai stones, which contain on writers. Gemmobgical Digest, 3, 2, 34-9, 4 pho­ average four times the amount of iron. M. O'D. tographs (3 in colour), 1 fig. Several Arabic writers of the thirteenth century TAYLOR, A., 1991. Emeraldolite (letter). onwards have commented on aspects of gem- Australian Gemmologist, 17, 9, 381-2. stones. Some of these are illustrated with com­ Queries loss of water and colour when seed ments on old mines and nomenclature. M.O'D. beryl is heated. R.K.M.

SHAW, R., 1989. Visits to High Tartary, Tarkand and Kashgsar 1868/69. Bulletin of the Friends of TAYLOR, W.R.,VJACQUES, A.L., RIDD, M., 1990. Jade, 6, 69-70. Nitrogen-defect aggregation characteristics of A nineteenth century account of jade mining in some Australasian diamonds: time-tempera­ Khotan. M.O'D. ture constraints on the source regions of pipe and alluvial diamonds. American Mineralogist, SHEAF, C, 1989. Jade around the clock. 75,1290-1310, 11 figs. Reflections on jade sales at Christie's, Hong Fourier transform infrared microscopy is used Kong. Bulletin of the Friends of Jade, 6, 53-9. to make a quantitative determination of the pro­ An account of the organization of jade auctions portions of aggregated N substitutional defects in Hong Kong in which both jadeite and nephrite platelet intensities and bulk N contents in Type la are discussed. M.O'D. diamonds from the Argyle and Ellendale olivine lamproite pipes in the Kimberley block of north­ STEIN, M.A., 1939. Sand-buried ruins of Khotan. west Australia and from alluvial deposits in west­ Bulletin of the Friends of Jade, 6, 71-3. ern and central Kalimantan (Indonesia) and An account of a visit to the jade diggings of Copeton in eastern Australia. M.O'D. Khotan in 1900. M.O'D. TOMBS, G.A., 1990. Argyle diamonds. Australian SUNG, W.-H., LIEN, C.-M., 1989. A study of zoo- Gemmobgist, 17, 8, 321-4, 6 figs. anthropomorphic jade earrings of prehistoric An account of the typical rough surfaced dia­ Taiwan. Bulletin of the Friends of Jade, 6, 87-91, monds found in the Argyle area of W. Australia. 1 map. Mines operate continuously year round, alternat­ A type of earring, hitherto unrecorded, has ing staff commute from Perth fortnightly. The been found in Taiwan in sites dating from the mines are open-pit and lamproite matrix is Neolithic period. The material is either tremolitic crushed and separated by gravity processes on site, nephrite or compact serpentine. [Paper repro­ computer controlled. Extreme roughness of sur­ duced from Bulletin No. 44 of the Department of faces is explained; crystals usually badly strained Anthropology. National Taiwan University, making polishing difficult; about 5% are gem 1984.] M.O'D. quality. Strong pinks and purples are known but are extremely rare and fetch exceptionally high J. Gemm., 1991, 22, 7 447

prices; it is not known whether more of these may gem zircon samples from Sri Lanka. XRD and be found. [Two captions to figures have been chemical analysis were also used. The degree of transposed.] R.K.M. metamictization increases systematically with U- Th content up to the point of total metamictiza­ WARD, F., 1988. The search for jade. Bulletin of tion. The amount of metamictization is deter­ the Friends of Jade, 5, 86-92. mined by examination of unit cell parameters. In The author describes his work in preparing an the IR spectrum band widths increase and inten­ article on jade for the National Geographic sities decrease with increasing U-Th content. Magazine. He was able to visit some of the jade- Bands related to Si-O bonds persist and bands producing areas of the world. M. O'D. related to Zr-O bonds disappear thus indicating that the structure of metamict zircon consists of WEISS, S., 1991. Eisenhaltiger gelber Orthoklas - distorted and disoriented isolated silica tetrahedra ein wiederentdeckter Edelstein aus with few if any displaced Zr cations. M.O'D. Madagaskar. (Iron-bearing yellow orthoclase - a rediscovered gemstone from Madagascar.) YEUNG, I., 1989. Treasures of Peinan culture Lapis, 16, 3, 13-14, 3 figs (1 in colour). found in Taiwan dig. Bulletin of the Friends of Fe-bearing yellow orthoclase from Madagascar Jade, 6, 8-6. is described with notes on the location and on the Archaeological examination of sites in the cen­ crystal forms encountered. The mineral is of gem tral mountain range of Taiwan has revealed quality and is found in pegmatites in the general nephrite artefacts in burial sites dating from 2025- region of Itrongay. M.O'D. 1025 BC. Many of the objects are a fine green. M.OT). WILKE, H.-J., POPOVA, E.E., 1991. Das Mineralogische Museum des Leningrader What's new in minerals? 1991. Mineralogical Bergbau-Institute. Lapis, 16, 6, 24-37, 13 Record, 22, 3, 213-20, 22 photographs (20 in photographs in colour. colour). The museum of the Leningrad Mining Gem quality minerals seen at the 1991 Tucson Institute contains a fine collection of mineral spec­ Gem and Mineral show included copper-coloured imens from the USSR and elsewhere. Exceptional blue tourmaline from the Batalha mine, Paraiba, crystals of brazilianite and uvarovite are among Brazil; green diopside crystals from Kaflu (?), those of gemmological interest. M.O'D. Pakistan; aquamarine crystals from the Jaqueto mine, Bahia, Brazil; vesuvianite crystals from the WOODHEAD, J.A., ROSSMAN, G.R., SILVER, L.T., Jeffrey mine, Asbestos, Quebec; pink apatite crys­ 1991. The metamictization of zircon: radiation tals from Nagar, Pakistan, and fine multi-coloured dose dependent structural characteristics. tourmaline crystals from the Cruzeiro district, American Mineralogist, 76, 74-82, 9 figs. Minas Gérais, Brazil. M.O'D. IR spectroscopy was used to examine a suite of J. Gemm., 1991,22,7 448

Book reviews

FLEISCHER, M., MANDARINO, J.A., 1991. Glossary logical texts this book includes basic details of of mineral species 1991. The Mineralogical fashioning. Record Inc., Tucson, pp.256. Price on appli­ The book is well-produced and very suitable cation. for students and the academic background of the This is the sixth edition of the invaluable authors ensures a balanced presentation of mate­ Glossary. Since the printing of the previous edition rial. M.O'D. in 1987 about 200 new mineral names have been added and about 900 previous entries have had to KERRICK, D.M., 1990. The Ah SiOspoly­ be revised. Six new mineral groups have been morphs. The Mineralogical Society of added. As before the listing is alphabetical with America. Washington DC. pp. xii, 406. Illus. chemical composition, crystal system, colour in black-and-white. US $20.00. [Reviews in where necessary, allocation to groups which are mineralogy Vol. 22.] themselves listed at the back of the book, Gemmologists will be interested in ALSiOs dimorphs and polymorphs and particulars of ref­ since andalusite, kyanite and sillimanite are mem­ erences, mostly in The American Mineralogist but bers of the group. The book opens with an intro­ also in other journals where appropriate. Where ductory section in which faciès series and baric there appears to be a close relationship between regimes are discussed together with tectonic meta- minerals without the entire series of compositions morphic analysis of metamorphic belts and between them being known the words 'compare geothermometry as applied to the aluminium sili­ with' are used. 'Isostructural with' is used to cates. The next section covers crystal structures, denote two crystal structures of the same type with optical and physical properties and is followed by different chemical compositions, as with grossular a lengthy section on phase equilibria, an important and berzeliite. There are also boxes which can be feature in minerals displaying polymorphism. completed by the reader to denote what species Later sections cover non-stoichiometry lattice are found in his collection. M.O'D. defects, Al/Si disorder, problems with fibrolite (here the name is distinguished from sillimanite), HURLBUT, CS., KAMMERLING, R.C., 1991. metamorphic reactions, reaction kinetics and crys­ Gemology. 2nd edition. John Wiley, New York. tal growth mechanisms, aluminium metasomatism pp. xiv, 336. Illus. in black-and-white and in and a final section dealing with aluminium sili­ colour. £43.70. cates in anatectic migmatites and peraluminous Since the first edition appeared several years granitoids. There is a general list of references at ago there have been a number of developments in the end of the book. Gemmologists will find the gemstone synthesis and enhancement. A new greatest interest in the section discussing colour chapter has been added for this reason and the and chemical composition. M.O'D. coloured illustrations are more numerous and of good quality. Additional species have been added NlEDERMAYR, G., 1990. Fluorit Mineral des to the descriptive section and in this edition the Regenbogens. Bode, Haltern, pp. 80. Illus. in more important species are listed first. Both sec­ colour. DM 14.80. tions are in alphabetical order. Details of impor­ The book covers nine major European fluorite tant synthetic materials are also given in the sec­ locations, each section being contributed by a dif­ tions on their natural counterparts. ferent author. British and other world locations The details of instruments and of gem testing are briefly described in a final chapter. Each sec­ are clearly given and the simple diagrams will be tion has its own valuable list of references and the useful for students. Refractive index is well first chapter deals with the mineral itself with explained and the description and details of the notes on its common modes of occurrence. Maps use of interference figures are particularly suc­ are provided for major sites and the colour pic­ cessful. In contrast to many other simple gemmo- tures are superb. M.O'D. J. Gemm., 1991, 22, 7 449

Proceedings of The Gemmological Association and Gem Testing Laboratory of Great Britain and Notices

OBITUARY held on 21 March 1991 at 100 Hatton Garden, Mr Rodney F. Parcel, Jr, FGA (D.1981), London EC1, the business transacted included Perris, California, USA, died recently. the election to membership of the following:

NEWS OF FELLOWS Gold Laboratory Membership On 8 May 1991 Michael O'Donoghue gave a Raymond Bloch, 74 Rue la Fayette,75009, Paris, talk entitled 'Improved gemstones' to the France. Snodland Parish Circle. Carlo Jewellers Ltd, 25a Hatton Garden, London On 20 May 1991 Michael O'Donoghue lec­ EC1N8BN. tured on gemstones at Sotheby's 'Looking at jew­ ellery' course. Ordinary Laboratory Membership Chatila Jewellers, 22 Old Bond Street, London MEMBERS' MEETINGS W1X 3DA. London Floralake Ltd t/a Bao Bijoux, 59 Beauchamp On 21 May 1991 at the City Conference Place, London SW3 1NZ. Centre, 76 Mark Lane, London EC3R 7JN, an Mozaffarian Jewellers Ltd, 66 Knightsbridge, Emerald Evening was held. The ICA video enti­ London SW1Y 7LA. tled 'Colombia emeralds' was shown. Following Palladian Diamond Co. Ltd, 100 Hatton Garden, the video, Ken Scarratt, Harry Levy and John London EC1N8NX. Kessler discussed various aspects concerning Michael Rose Jewellers, 3 Burlington Arcade, emeralds, including localities, synthetics and treat­ London Wl. ments. Lionel J. Wiffen Ltd, 88-90 Hatton Garden, London EC IN 8PN. Midlands Branch On 19 April at Dr Johnson House, Bull Street, MEETINGS OF THE COUNCIL OF MAN­ Birmingham, the Annual General Meeting was AGEMENT held at which Mr David Larcher, FBHI, FGA, At a meeting of the Council of Management and Mr John Bugg, FGA, were re-elected held on 17 April 1991 at 27 Greville Street, Chairman and Secretary respectively The AGM London EC IN 85U, the business transacted was followed by a showing of the Snowman video included the election to membership of the fol­ 'The wonders of Fabergé'. lowing:

North West Branch Fellowship On 17 April 1991 at Church House, Hanover Argirakou, Ioulia, Volos, Greece. D.1990. Street, Liverpool 1, Carol Gibbs gave a talk enti­ Farkas, Susan, Vancouver, Canada. D.1990. tled 'Tortoiseshell of the Gilbert Islands'. On 15 May 1991 at Church House Gordon Brohier gave Ordinary Membership a talk entitled 'The gems of Sri Lanka'. Blanch, Gloria, London. Hull, Munira F., Harrow. MEETING OF THE TRADE LIAISON Mansfield, James G. London. COMMITTEE Mizuno, Kayoko, London. At a meeting of the Trade Liaison Committee Pirkl, Stephen V„ Glendale, Calif., USA. 450 J. Gemm., 1991, 22, 7

Schupp, Frank J., Pforzheim, Germany. Ordinary Shah, Fatehchand J., London. Ashton, Donald, Beckenham. Windwick, William, Moray. Michels, Hans-Joachim, Dinslaken, Germany. Newton, Beverly A., Alhambra, Calif., USA Niblock, Simon G., Ebop, New Zealand. At a meeting of the Council of Management Nodznaia, Dikran, Southall. held on 22 May 1991 at E.A. Thomson (Gems) Smith, Penelope A., Cirencester. Ltd, Chapel House, Hatton Place, London EC IN Tamada, Tomohide, Kobe, Japan. 8RX, the business transacted included the election Yoshimoto, Yoshihiro, London. to membership of the following: CORRIGENDA Fellowship On p.382 above, 2nd column, line 18 from Berlioz, Roger F.B., Kandy, Sri Lanka. D.1990. foot, for 'Minerals of Larousse' read 'Larousse of Sinclair, Lesley, Stenhousemuir. D.1990. minerals'

FORTHCOMING MEETINGS

London

3-4 November 1991 Conference and Presentation of Awards (see p. 394)

Midlands Branch Meetings held at Dr Johnson House, Bull Street Birmingham. Further details from David Larcher on 021 554 3871.

13-15 September 1991 The Branch will participate, with an exhibition of gem testing, in the National Exhibition of Time to be held at The British Horological Institute, Upton Hall, Nr Newark, Notts.

20 September 1991 Mr F. Deitsch of Mikimoto Pearls. 'Pearls' 18 October 1991 Mr Alan Hodgkinson. 'A taste of Scottish gemmology'

15 November 1991 Mr J. Gosling. 'The Guyana lapidary project'

North West Branch Meetings held at Church House, Hanover Street, Liverpool 1. Full details from William Franks on 061-928 1520.

18 September 1991 Mr Matthew Girling of Bonhams. 'The selling of jewellery at auction' 16 October 1991 Mr Alan Hodgkinson. 'A gemmological bonanza' 20 November 1991 Annual General Meeting. J. Gemm., 1991, 22, 7 451

Letter to the Editor

From A.E. Farn, FGA very human touch and a great sense of humour. He gave names to his favourite gemmological Dear Sir, tools, such as Henry and Henrietta respectively It is always a pleasure to read a 'Letter to the for two much used pearl scoops. He also had Editor', particularly when penned by our Vice names for his spectroscopes which may well be President, R.K. Mitchell. I refer to his letter upon mentioned in the forthcoming treatise of Eric the name changes of methylene iodide and mono- Bruton and Keith Mitchell on Anderson's bromo-naphthalene (The Journal of Gemmology, research and work with the spectroscope. 1991, 22, 6, 387-8). In B.W. Anderson's day at 55 May I take this opportunity to draw attention Hatton Garden I feel sure we termed it alpha- to a short notice on page 386 of volume 22, no.6, mono-bromo-naphthalene. 'Alpha' was also adjoining Keith Mitchell's letter. It is headed used by Basil Anderson when referring to the 'Verbal Testing at the Laboratory' and then pro­ 4155Â line in diamond. That of course was in the ceeds to describe the method of sending articles days before the dwarfing effect of nanometres. for verbal testing by post - this puzzles me. I can Keith Mitchell admits to a somewhat tongue- understand 'mono' in monocular and 'di' in in-cheek frame of mind in his comments. He dichroscope, but fail to relate 'verbal', by post. attributes this to a surfeit of years and a dislike of change. I am completely in accord with his senti­ Yours in retrospect. ments. This of course, is hardly surprising as we A.E. Farn are both elderly trade products and share a great regard for the memory and name of Basil 6 June 1991 Anderson. Anderson, despite his erudition, had a Seaford, Sussex. 452 J. Gemm., 1991,22,

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ThcJournal of Gemmology

Contents

Two strongly pleochroic chatoyant gems R.C. Kammerling and J.L Koivula 395

Two types of historical traps: on 'Diamond Softening5 and the 'Antiquity of Emerald Oiling5 K. Nassau 399

Anomalous behaviour of certain geuda corundums during heat treatment S.Z. Perera> A.S. Pannila, H.P.N.J. Gunasekera and R.N. Ediriweera 405

Emeralds from Colombia (Part 2) G. Bosshart 409

The microscopic determination of structural properties for the characterization of optical uniaxial natural and synthetic gemstones. Part 2: Examples for the applicability of structural features for the distinction of natural emerald from flux-grown and hydrothermally- grown synthetic emerald L. Kief en and K. Schmelzer 427

Gemmological abstracts 439

Book reviews 448

Proceedings of The Gemmological Association and Gem Testing Laboratory of Great Britain and Notices 449

Letter to the Editor 451

Copyright© 1991 The Gemmological Association and Gem Testing Laboratory of Great Britain Registered Office: Palladium House, 1-4 Argyll Street, London W1V IAD

ISSN: 0022-1252

Produced by Green Belt Studios: Printed by Quadrant Offset, Hertford, England.