Volume 20 No. 6 April 1987 TheJournal of Gemmology

GEMMOLOGICAL ASSOCIATION OF GREAT BRITAIN OFFICERS AND COUNCIL

President: *Sir Frank Claringbull Ph.D., F.Inst.P., FGS Vice-Presidents: J. R. H. Chisholm, MA, FGA R. K. Mitchell, FGA Chairman: *D. J. Callaghan, FGA Vice-Chairman: *N. W. Decks, FGA Honorary Treasurer: *N. B. Israel, FGA

Fellows elected to Council: *A. J. Allnutt, M.Sc., J. A. W. Hodgkinson *J. B. Nelson, Ph.D., Ph.D. D. Inkersole FRMS, F.Inst.P., *E. M. Bruton B. Jackson W. Nowak, C.Eng., *C. R. Cavey *E. A. Jobbins, B.Sc., C.Eng., F.R.Ae.S. L. F. Cole FIMM M. J. Q'Donoghue, P. J. E. Daly, B.Sc. C. B. Jones MA, FGS *A. E. Farn *G. H. Jones, B.Sc., Ph.D. *P. G. Read, C.Eng., A. J. French D. G. Kent MIEE, MIERE *R. R. Harding, B.Sc., D. M. Larcher *K. Scarratt D.Phil. D. Morgan E. Stern S. E. Hiscox *C. H. Winter

* Members of the Executive Committee

Branch Chairmen: Midlands Branch: P. West, FGA North-West Branch: S. Hill, FGA South Yorkshire & District Branch: J. I. Reynolds, FGA

Examiners: A. J. Allnutt,M.Sc., Ph.D., FGA D.G.Kent,FGA E. M. Bruton, FGA P. Sadler, B.Sc., FGS, FGA A. E. Farn, FGA K. Scarratt, FGA 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 G. H. Jones, B.Sc., Ph.D., FGA

Editor: E. A. Jobbins, B.Sc., C.Eng., FIMM, FGA Consultant Editor: J. R. H. Chisholm, MA, FGA Editorial Assistant: Mary A. Burland Curator: C. R. Cavey, FGA Secretary: Jonathan P. Brown, FGA, Barrister

Saint Dunstan's House, Carey Lane, London EC2V SAB (By Goldsmith's Hall) Telephone: 01-726 4374 TheJournal of Gemmology

VOLUME 20 NUMBER SIX APRIL 1987

Cover Picture An unusually translucent jadeite figurine and other jadeite carvings showing colour variation (see 'Some colour variation in jadeite', p. 376). Photograph byE.A. Jobbins.

ISSN: 0022-1252 338 J. Gemm., 1987, 20, 6 Amajor new initiative in gemmological education

Photograph couttesy of K. Blakemore The Gemmological Association has collaborated with the Gem Testing Laboratory of Great Britain to launch a programme of one-day courses.

The courses have been designed for the Association by Ken Scarratt and will be held at the Gem Testing Laboratory in London. The aim is to give practical instruction and experience to students studying gemmology, particularly those preparing to take the FGA examination by home study, and updates specialized courses for all gemmologists. Various courses are being offered, the dates of which are: 1 and 29 May Practical gemstone identification - General 3 July Practical identification - Pearls 17 July Practical identification - Jade, amber and their simulants 31 July Practical identification - Synthetic ruby and sapphire 28 August Practical identification - Synthetic emerald and amethyst 2 October Introduction to diamond grading (of particular interest to students preparing to take the Gem Diamond examination.) Each course is limited to 12 participants and is offeree at the especially low charge of £55 plus VAT (including lunch). The courses are open to all students and members of the Association who would like to take a short refresher course. Further information from Paula Jennings on 01-7264374. To book for the courses please use the coupon given on page 397 and enclose the necessary remittance. J. Gemm., 1987, 20, 6 339

Damage to cut diamonds

Dr H.A. Hänni, FGA, and G. Bosshart, GG

Swiss Foundation for the Research of Gemstones (SSEF)*, Zurich, Switzerland

Abstract serious burn marks at 600°C, if the mounted Diamonds are generally considered as extremely resistant diamond has not, or not entirely, been coated by a gems. Thermal or mechanical damage is, nevertheless, borate (boric acid, Liquobor, borax, etc.). The possible during various stages of working (cutting, function of the borate melt is to coat the diamond in setting, soldering) or wearing the stones. Thus many cut order to prevent oxygen from reaching the surface diamonds reach the jeweller's counter with minor to distinct damage. Only a relatively small proportion of the of the stone. However, if the diamond has not been observed injuries result from wearing. Minor blemishes degreased, openings may form in the borate can be removed with minimal weight loss by a specially coating. Then corrosion of the diamond can start trained cutter. (Figure 10). A borate melt is able to corrode corundums but Chemical resistance not diamonds. The latter can be attacked only by A diamond's high resistance to chemical attack the hot melts of metals like platinum, iron, derives from the strong covalent bonding between tungsten, or by some strongly oxidizing compounds the carbon atoms in the diamond lattice. At low (De Beers Industrial Diamond Division: Properties temperature and pressure conditions, it effects a of Diamond, special publication). Yet under all strong inertia against all standard acids, caustics normal chemical conditions, diamonds do not and solvents. However, at high temperatures, and react. in the presence of certain melts or gases, the diamonds do not comport themselves with such Mechanical Resistance invulnerability any longer. The hardness of a diamond, or more precisely its In our laboratory, several experiments were extremely high resistance to abrasion, is the carried out on cut diamonds (Bosshart, in preparation) prominent physical property which makes a diamond to shed light on their thermal behaviour. Exposed to be for ever. It is seldom that blemishes can be to air, the stones were heated in an electric recognized by eye, even after decades of wearing the laboratory furnace without any coating. Already stone as a solitaire. A diamond occupies the during an annealing cycle of 30 minutes at 650°C, or uppermost level of the Mohs' scale of scratch after two hours at 600°C? a whitish turbidity hardness. This means that it is not scratched by any appeared on the faceted surfaces. No transformation other mineral except by its own kind. The hardness to (black) graphite or amorphous carbon was depends on the direction of scratching on the crystal observed. Obviously alteration of the diamonds' (hardness anisotropy). There are harder and outermost layers of carbon atoms by the oxygen in slightly softer directions. This fact is taken into the air takes place as low as 600°C. During this account during cutting because diamond surfaces oxidation process, the diamonds transform directly can be worked successfully only in the softer into gaseous carbon dioxide (C02). Whitish, shallow directions. but rough burn marks are left behind. Considerably The longevity of a diamond is limited by its deeper burn pits are produced at higher temperatures tendency to split along very definite atomic layers and longer annealing. when struck precisely parallel to them. This quality In comparison with our static annealing experi­ of developing flat separation planes is termed ments in the electric laboratory furnace, the cleavage. Diamond possesses a perfect cleavage turbulent supply of oxygen under the soldering parallel to the eight octahedral crystal faces and less torch of the goldsmith certainly leads to more pronounced ones parallel to some other faces. Another limitation is its sensitivity to knocks in any other direction, on facet edges and corners ^Schweizerische Stiftung für Edelstein-Forschung (SSEF). especially; bruises and percussion cracks are liable 340 J. Gemm., 1987, 20, 6 to form. Their size depends on the force of impact. scratches when it is contaminated with diamond Inversely, static pressure on surfaces does not harm paste (Figure 4). a diamond at all. If diamonds are heated too much during the Large inclusions represent yet another hazard for cutting operation, rough burn marks are incurred, diamonds. However, it is a fairly rare accident when especially on lower girdle facets, star facets and on a piqué diamond with extended cleavages, or the table. A build up of heat in the metal of the dop incorporating foreign mineral inclusions surrounded is responsible for this. As mentioned earlier, the by tension haloes, breaks into pieces under mechanical superficial corrosion of the diamond already starts or thermal stress. at 600°C with the formation of roundish to annular burn marks. The view that fissures across facet edges are generated on diamonds as they are pressed against Damage during cutting and polishing each other in a stone paper may be correct in certain Industrial cutting of diamonds cannot always be cases. Stones in lots of considerable weight are carried out with sufficient care, probably for particularly endangered. As a rule, however, the reasons of time. Many a diamond cutter is entirely cause of the damage lies in the too strongly aware neither of the brittleness of all diamonds and tightened dop. In order to form pressure cracks on of the internal strain inherent in many diamonds, diamonds in a stone paper, a greater force is nor of the corresponding vulnerability of the goods required than that applied to such wrappings in he is cutting. Consequently, many diamonds leave general. the cutting works with minor blemishes. The most On the other hand, large diamonds merit frequent of these negative characteristics are small individual packing because blemishes, like scratches cleavages, pressure and percussion cracks, as well and abraded facet edges can happen relatively as burn marks. easily. An excessively strong pressure during the bruting The unpopular large culet of old-cut diamonds process creates groups of tiny fissures parallel to the today has an equally extreme analogue in the cleavage direction (Figure 1). They traverse the pointed culet of the modern brilliant-cut (a pointed girdle and often appear at four different positions pavilion without any facet). The danger to this type around the circumference, separated from each of culet can be deduced from the fact that, during other by 90° (in the normal case of a 4-point grading, we encounter less than ten undamaged brilliant). Finely bruted girdles show these tiny pavilion pyramids for every one hundred diamonds cleavages in a much less conspicuous manner than originally with pointed culets. Usually the exact coarsely bruted girdles. In earlier days, these time of damage cannot be determined. fissures were harmlessly designated bearding and wrongly considered external characteristics. Usually they can be removed; in these instances, the removal is easier and more complete by faceting of Damage during setting the girdle rather than by polishing it. Thus internal Prominent parts of a cut diamond, i.e. not only blemishes are eliminated and this results in an the pointed culet but also the girdle, are especially improvement of the clarity. sensitive to injuries. A girdle of medium thickness A further injury of the first hour, which is shows little tendency to cleave under the normal encountered quite frequently, consists of pressure forces of impact during setting. However, the cracks. They probably stem from the use of the thinner the girdle, the easier it can chip under the dop, the tool which holds the diamond tight during influence of knocks, pressure or scratching. Thereby cutting (Figures 2 and 4). The blemishes occur as cleavage is stimulated if the direction of the small cracks, roughly on the same level of the destructive stress acts roughly parallel to it. pavilion, running across facet edges. They are Actually, irregularly formed fracture surfaces are caused by a too strongly tightened dop or by encountered more frequently. Off to the sides, they knocking vibrations (Figure 5). We also sometimes readily change into short cleavage fissures. observe more or less circular fissures, mainly on Greater damage is occasionally caused by slipped pavilion facets, the origin of which we cannot yet punches, or by the stone-setter's electric hammer, explain. Possibly, however, there is a connection and has a characteristic appearance. Mostly they are with the dop as well (Figure 3). cataract fractures extending into the pavilion and When a diamond is turned in the dop, scratches are situated close to a prong (claw). In the central in the form of concentric arcs may occur on the table part of the depression, they have a conchoidal form (Figure 6). The finger-like piece of metal pressing and continue in cleavage steps towards the edge of the pavilion of the brilliant into the dop causes these the fracture (Figure 7). J. Gemm., 1987, 20, 6 341

Fig. 1. Fine cleavage fissures running across the slightly polished Fig. 2. Diamond fixed in a cutter's dop. Burn marks may appear girdle of a brilliant-cut diamond. Darkfield illumination, at both points of contact on the pavilion. llx.

Fig. 3. Roundish cracks caused by percussion or pressure on a Fig. 4. Brilliant-cut diamond of 2 ct tightly mounted in the dop. lower girdle facet. Darkfield illumination. 28x. Heat accumulation in the finger-like piece of metal sometimes leads to burn marks on the table.

Fig. 5. Pressure crack across a pavilion facet edge of a brilliant-cut Fig. 6. Arc-shaped scratches on the table of a brilliant-cut diamond. Darkfield illumination. 34x. diamond viewed from the pavilion side. Darkfield illumination. 17x. 342342 J.J. Gemm.,Gemm., 1987,20,61987, 20, 6

Fig.Fig. 7. ComplexComplex cataractcataract breakagebreakage inin ththee pavilionpavilion of a brilliantbrilliant-cu-cutt Fig. 8. WearWear marks inin thethe formform ofof smallsmall shallow bruisesbruises onon thethe diamond,diamond, generatedgenerated byby shockshock impactimpact fromfrom thethe crowncrown sideside ededgeges andand cornerscorners ofof a starstar facetfacet andand a fine sscratccratchh onon anan oonn ttoo ththee girdlegirdle zone.zone. DarkfieldDarkfield illumination.illumination. l7x.17x. adjacentadjacent mainmain facet.facet. DarkfieldDarkfield illumination.illumination. 22x.

DamageDamage duringduring wearwear rotate,rotate, itit usuallusuallyy scratchesscratches thethe solitairesolitaire diamonddiamond atat SeveralSeveral typestypes ofof blemisheblemishess areare observedobserved onon twotwo oppositeopposite placeplacess accordingaccording toto howhow thethe ringring hashas mountemountedd diamonds.diamonds. TheThe mostmost widespreadwidespread damagedamage beenbeen placedplaced onon thethe finger.finger. Rough,Rough, whitishwhitish abrasionabrasion originatesoriginates frofromm knockinknockingg ththee setset diamonddiamond againstagainst markmarkss resultresult fromfrom thisthis.. TheTheyy areare alsoalso occasionallyoccasionally ofof otherother objects.objects. TheyThey consistconsist ofof small,small, bubutt loupe­loupe- fissure-like character.character. visible,visible, bruisesbruises andand percussiopercussionn cracks.cracks. TheyThey appearappear BruisesBruises andand percussionpercussion crackscracks onon ththee pavilionpavilion onon edgesedges andand cornerscorners aroundaround ththee tabletable andand thethe sideside ofof setset diamondsdiamonds areare probablprobablyy notnot ththee resultresult ooff crowncrown facets.. TheseThese weawearr marksmarks demonstratedemonstrate wearinwearingg jewelleryjewellery.. ThThee paviliopavilionn iiss protecteprotectedd bbyy thethe clearldearlyy thathatt diamonddiamondss araree slightlyslightly sensitivesensitive ttoo thethe mountinmountingg anandd ththee finger. TheseThese blemisheblemishess araree notnot influencinfluencee ooff shocksshocks (Figures(Figures 8 anandd 9)9).. recenrecentt anandd usuallusuallyy havhavee beebeenn produceproducedd iinn thethe LargeLargerr breakagebreakagess iinn ththee girdlgirdlee regioregionn alsoal!\o occur,occur, diamondiamondd factory,factory, aass mentionementionedd earlierearlier.. ScratchesScratches particularlparticularlyy oonn bibigg diamonddiamondss witwithh a ververyy thithinn girdlegirdle mamayy occuoccurr whenevewheneverr diamonddiamondss touchtouch,, nonott onlonlyy onon (e.g(e.g. oonn old-cuold-cutt diamonds)diamonds).. ThesThesee casescases,, however,however, stonestoness iinn a lolott bubutt alsalsoo iinn ththee mountemountedd statestate,, forfor araree leslesss frequenfrequentt thathann generallgenerallyy assumeassumedd iinn thethe examplexamplee iinn ththee jewellerjewelleryy box.box. jewellerjewelleryy tradetrade.. StonStonee settingsettingss witwithh widelwidelyy separatedseparated prongprongss favoufavourr ththee formatioformationn ooff sucsuchh fractures.fractures. DamagDamagee iinn repairinrepairingg anandd transformintransformingg diamonddiamond WhilWhilee ordinarordinaryy percussiopercussionn crackcrackss effeceffectt a reductionreduction jewellerjewelleryy ooff ththee claritclarityy gradgradee ooff loupe-clealoupe-cleann stonestoness only,only, AccordinAccordingg ttoo ththee introductorintroductoryy statementsstatements,, super­super­ largelargerr fracturefracturess mamayy easileasilyy lowelowerr a VVSS anandd eveevenn aann ficial burnburn marks marks are are produced produced under under the the goldsmith goldsmith''ss SISI claritclarityy gradegrade.. torctorchh ifif ththee mountemountedd diamondiamondd hahass nonott beebeenn FurtheFurtherr damagdamagee developdevelopss whewhenn a solitairsolitairee rinringg iiss sufficientlsufficientlyy degreased.. ThThee boratboratee coatincoatingg thethenn worwornn nexnextt ttoo a diamond-studdediamond-studdedd eterniteternityy ringring.. cannocannott offeofferr completcompletee protectioprotectionn anandd burburnn markmarkss SincSincee ththee rinringg oonn ththee neighbourinneighbouringg finger mamayy araree ththee consequenceconsequencess (Figur(Figuree 10)10)..

FigFig.. 99.. BruisBruisee oonn a tabltablee edgedgee accompanieaccompaniedd bbyy fairlfairlyy deedeepp Fig. 10. Brilliant-cut diamond with whitish surface due to percussiopercussionn crackscracks,, radiatinradiatingg ououtt ttoo botbothh sidesidess ooff ththee facefacett extensivee burningburning.. BrilliancBrilliancee grosslgrosslyy reducedreduced.. DarkfieldDarkfield edgeedge.. DarkfielDarkfieldd illuminationillumination.. 34x34x.. illuminationillumination.. 13x13x.. J. Gemm., 1987, 20, 6 343

Repair of damaged diamonds had from the beginning or which they once Most of the blemishes listed here can be removed possessed. with minor weight loss by a carefully executed If, apart from the clarity, the cut can be repolishing operation. Damages of considerable ameliorated in the same operation, the recommenda­ depth demand a more complete recutting of the tion for repolishing includes a comment for the stone and cost more than just a few points of weight. cutter with respect to symmetry, polish, girdle or Buying loupe-clean diamonds with weights like culet. 1.00 ct is not recommended, for the simple reason that even a slight touch up of such a stone will Conclusion decrease its weight below the critical limit. It can be stated that a precise microscopic The skills of a specialized diamond cutter are examination of damage on cut diamonds in certain needed for a successful repolishing operation. He cases enables the recognition of the causes. The does not treat diamonds like the hardest material in SSEF Laboratory has been in a position to carry out the world but works gently and cautiously as if this type of analysis for many years. Insurance handling raw eggs. If this approach would take hold companies and other interested parties have regularly and prevail in all diamond workshops, a much made use of this service. larger portion of loupe-clean diamonds would reach the market. Acknowledgements In the damaged state, diamonds are mainly We wish to extend our gratitude for technical graded between VVS 1 and SI 2 if they do not comments and suggestions to the following pro­ contain any internal characteristics other than new fessionals in Zurich: Messrs B. Christen, A. cracks. SSEF clarity grading always assesses the Guichon, F. Loosli, D. Roux, and P. Widmer. possibility of improving the stone and a corresponding Figures 2 and 4 were kindly placed at our disposal recommendation for repolishing, plus a precise by Mr Guichon. sketch for the specialized cutter are provided. Thus, the repolishing operation finally raises such [Manuscript received 30 December 1986, revised 26 January stones up to the clarity level which they could have 1987.]

GIA INSTRUMENTS The Gemmological Association now stocks a range of superb quality gem-testing instruments manufactured by the Gemological Institute of America. DiamondLite Minilab Included in the range is a diamond light which Another very useful piece of equipment is the is designed to provide a constant, uniform, Minilab-your travelling companion. A colour-corrected light source in an instrument lightweight, portable minilab for the travelling that facilitates the rapid, accurate colour professional, perfect for off-site valuations and grading of diamonds. This DiamondLite also on-the-spot gem testing. The case contains a incorporates an ultraviolet light source to whole range of equipment including: Duplex III detect fluorescence in diamonds. pocket ref ractometer; polariscope; prism The cost of this unit is £395.00 including spectroscope; GEM dichroscope; Chelsea postage and packing plus £59.25 VAT (UK colour filter; SG liquid set; lens and filters; only). penlight; 10x loupe; GEM cloth; six function calculator; light cube; stainless steel locking type tweezers; power pack and recharger (adapts to 110V and 220V). Exceedingly good value at £895.00 including postage and packing plus £134.25 VAT (UK only). These are just two items selected from the range and to place your order for either, telephone Doreen Walker on 01 -726 4374 with your credit card details or send your payment to the Association. Overseas customers may pay by credit/charge card or alternatively a pro forma invoice will be sent. Gemmological Association of Great Britain, Saint Dunstan's House, Carey Lane, London EC2V 8AB Telephone: 01-726 4374 Cables: Geminst, London EC2 344344 J.J. Gemm.,Gemm., 1987,20,61987, 20, 6

ConfusingConfusing colourlesscolourless stonesstones

David Kent, FGAFGA

LondonLondon

BeforeBefore retirementretirement I waswas employedemployed byby a LondonLondon I was impressedimpressed byby thethe apparentapparent goodgood qualityquality ofof firmfirm ofof jewellersjewellers asas anan appraiserappraiser andand buyerbuyer ofof thethe stones,stones, whichwhich I roughlyroughly estimatedestimated asas weighingweighing second-handsecond-hand jewellery.jewellery. OneOne dayday inin 19761976 a clientclient 0.500.50 ctct forthefor the centrecentre andand 0.250.25 ctct forfor eacheach oftheof the twotwo offeredoffered forfor salesale a gentleman'sgentleman's flush-setflush-set 1818 ctct goldgold sideside stones.stones. UsingUsing mymy lenslens andand MoeMoe gauge,gauge, I gypsygypsy ring,ring, setset withwith threethree brilliant-cutbrilliant-cut colourlesscolourless inspectedinspected thethe ringring inin ourour veryvery good,good, north-facing,north-facing, stones.stones. TheThe ringring carriedcarried thethe LondonLondon hallmarkhallmark forfor 'buying''buying' daylight.daylight. I suddenlysuddenly realizedrealized thatthat thethe 1975.1975. AdditionallyAdditionally therethere waswas a valuation,valuation, alsoalso dateddated stonesstones showedshowed tootoo muchmuch dispersion, andand beingbeing 1975,1975, fromfrom a HattonHatton GardenGarden firm forfor a threethree stonestone takentaken aback,aback, refusedrefused toto offer,offer, andand handedhanded thethe ringring flush-set diamonddiamond gypsgypsyy ring,ring, statingstating thatthat itit shouldshould backback ttoo thethe client.client. bebe insuredinsured forfor £980.£980. TheThe clientclient intimatedintimated thatthat hehe BeingBeing alreadyalready familiarfamiliar withwith simulantssimulants suchsuch asas woulwouldd bbee preparepreparedd toto sellsell thethe ringring forfor aboutabout halfhalf thatthat YYAAG G andand GGG,GGG, I waswas puzzledpuzzled andand immediatelyimmediately sentsent amount.amount. a messagemessage aroundaround thethe branchesbranches warningwarning thethe staffstaff thatthat a newnew simulantsimulant appearedappeared toto bbee ttoo hand.. TwoTwo oror threthreee weeks latelaterr I learnelearnedd thathatt a numbenumberr ooff jewellerjewellerss hahadd beebeenn defraudedefraudedd ooff considerablconsiderablee sumssums bbyy ththee ususee ooff a neneww diamondiamondd simulansimulantt - cubiccubic zirconiazirconia!! HavinHavingg quitquitee a googoodd privatprivatee collectiocollectionn ooff gemstonesgemstones,, I resolveresolvedd ttoo displaydisplay aass manmanyy colourlesscolourless stonesstones asas possiblpossiblee iinn ononee cascasee foforr comparisocomparisonn purposespurposes.. SinceSince thithiss timtimee I havhavee beebeenn ablablee ttoo adaddd ttoo ththee originaloriginal displaydisplay,, somsomee stonestoness beinbeingg kindlkindlyy presentepresentedd bbyy googoodd friends.friends. ThThee collectiocollectionn iiss househousedd iinn a purpose-madepurpose-made displadisplayy boboxx constructeconstructedd bbyy ththee authoauthorr (Figur(Figuree 1)1). AA piecpiecee ooff hardwoohardwoodd (a(ann ololdd breadboard!)) was cucutt ttoo sizsizee (20(2044 x 181844 x 1177 mm)) anandd smoothesmoothedd witwithh abrasivabrasivee paperpaper.. ThThee positionpositionss ooff ththee holeholess ttoo locatlocatee ththee stonestoness werweree carefullcarefullyy measuremeasuredd ououtt anandd thethenn markemarkedd witwithh a centrcentree puncpunchh anandd a hammerhammer.. ThThee smalsmalll holeholess ssoo formeformedd werweree thethenn enlargeenlargedd usinusingg twistwistt drilldrillss ooff suitablsuitablee sizsizee ttoo forformm shalloshalloww cupscups.. AA chisechisell wawass useusedd ttoo makmakee rectangularectangularr holesholes.. AfterAfter smoothinsmoothingg ththee woowoodd wawass stainestainedd usinusingg blacblackk leatheleatherr dyedye,, oorr iitt coulcouldd bbee sprayesprayedd witwithh gregreyy primeprimerr followefollowedd bbyy matmattt blackblack,, botbothh paintpaintss beinbeingg availablavailablee iinn aerosoaerosoll forformm fro fromm painpaintt shopshopss oorr cacarr accessoraccessoryy storesstores.. ThThee self-adhesivself-adhesivee numbernumberss araree availablavailablee frofromm ananyy googoodd stationerstationer.. AA hingehingedd lilidd ooff cleaclearr PerspePerspexx wawass provideprovidedd ttoo keekeepp ththee stonestoriess iinn positionposition.. AA fefeww yearyearss agagoo A.DA.D.. MorganMorgan,, FGAFGA,, madmadee foforr FigFig.. 11.. BoBoxx constructeconstructedd bbyy ththee authoauthorr ttoo displadisplayy anandd houshousee hihiss mmee aann efficienefficientt infrareinfraredd reflereflectometer,c tome ter, anandd iitt mamayy collectiocollectionn ooff colourlescolourlesss stonesstones.. interesinterestt fellofelloww gemmologistgemmologistss ttoo seseee hohoww closelcloselyy ththee J. Gemm., 1987, 20, 6 345

Table 1. Infrared reflectometer readings on colourless gemstones in the David Kent collection. Diamond calibrated at 70.

Meter Mean Weight Meter Mean Weight Speciec s SG Species SG reading RT (ct) reading RI (ct)

17 1.434 Fluorite 2.91 3.18 29 1.65 Smithsonite 044 4.19 17 1.438 Opal 1.96 2.00 vague (approx) 19 1.505 Paste 1.15 2.44 29 1.678 Diopside 0.51 3.22 20 1.506 Petalite 2.06 2.39 30 1.712 Spinel 0.96 3.61 22 1.549 Quartz 2.67 2.65 30 1.725 Synthetic spinel 1.68 3.65 22 1.549 Synthetic quartz 4.67 2.65 31 1.736 Grossular 1.27 3.60 23 1.540 lohte 1.19 2.58 32 1.782 Benitoite 0.44 3.65 23 1.555 Beryllonite 0.84 2.82 33 1.764 Sapphire 2.73 4.00 23 1.560 Scapolite 0.39 2.60 33 1.764 Synthetic sapphire 3.93 4.00 23 1.561 Labradorite 1.25 2.68 38 1.830 YAG 2.90 4.57 23 1.583 Beryl 1.48 2.74 39 1.764 Synthetic sapphire/ 1.12 4.66 25 1.615 Topaz 3.95 3.56 strontium titanate 25 1.622 Amblygonite 2.58 3.03 doublet 25 1.629 Tourmaline 0.60 3.00 42 1.95 Zircon 2.52 4.66 (approx) 42 2.03 GGG 1.67 7.10 25 1.640 Baryte 8.01 4.49 56 2.17 Cubic zirconia 1.51 5.80 25 1.647 Datolite 0.96 2.90 62 2.25 Lithium niobate 0.64 4.70 26 1.633 Danburite 1.58 2.98 64 2.41 Strontium titanate 1.21 5.14 27 1.655 Jadeite 1.77 3.34 70 2.42 Diamond 0.48 3.52 27 1.660 Enstatite 1.03 3.22 76 2.42 Diamond/synthetic 1.68 3.82 27 1.662 Euclase 0.43 3.10 sapphire doublet 28 1.660 Phenakite 0.85 2.98 80 2.62 Synthetic rutile 1.55 4.20 meter readings follow the refractive indices, shown in the Table 1. The RI values above 1.81 are approximate, having been determined by the real and apparent depth method. The specific gravities were determined by the hydrostatic method using water.

[Manuscript received 13 February 1986, revised 9 January 1987.] 346 J. Gemm., 1987, 20, 6

Investigation of a sapphire cat's-eye from Burma

Dr K. Schmetzer and L. Kiefert

Institute of Mineralogy and Petrography, University of Heidelberg, West Germany and Deutsche Stiftung Edelsteinforschung, Idar-Oberstein, West Germany

Abstract Microscopic investigations A sapphire cat's-eye from Burma is described and the The blue sapphire from Burma was cut as an oval cause of chatoyancy was investigated. The sample does cabochon of 4.0 x 5.5 mm in size and weighed not show needle- to rod-like inclusions, which are in 0.53 ct. The sample disclosed a chatoyancy-like general responsible for chatoyancy of gemstones. The effect on the curved surface: the direction of the Burmese sapphire is not a single crystal but consists of two sectors which are slightly inclined against each other: the reflected ray is orientated parallel to the long inclination angle equals 11°. In both sectors, growth 5.5 mm axis of the oval stone. Microscopic investi­ planes parallel to the hexagonal dipyramid (2241) as well gation in methylene iodide disclosed that the as glide planes parallel to the basal pinacoid (0001) are sapphire consists of two parts which are separated observed. Chatoyancy is caused by total internal reflection by an irregular step-like surface looking like a at irregular patch-like fissures on basal glide planes. landscape with a dense distribution of hillocks (Figure 1). In each part of the sample, one set of straight parallel planes is observable, the two sets of planes are slightly inclined against each other forming an angle of ~ 169° (Figure 2). The orientations of the two sets of planes are determined Introduction to be parallel to the basal planes of the two parts of Rubies and sapphires from certain occurrences, the sapphire crystal. Consequently, the sample is e.g. Burma and Sri Lanka, frequently show not a corundum single crystal but consists of two asterism when the crystals are cut in the cabochon sectors, the c-axes of which are slightly inclined to form. The most common six-rayed stars are caused each other: the inclination angle equals 11°. Under by needle- to rod-like inclusions of rutile or other crossed polarizers, interference striations and inter­ iron-titanium oxides. The needle axes of these ference colours are observable at the irregular inclusions are lying in the basal plane (0001) in three boundary between both parts of the corundum different orientations parallel to traces of the prism crystal (Figure 3). This optical effect is due to the faces of the host crystal. If only one set of parallel different crystallographical orientations of these orientated needle-like inclusions is present in sectors. In each part of the corundum crystal, a corundum, a cat's-eye is produced. This condition, second type of sets of straight parallel planes is however, is extremely rare if existing at all in observed forming angles of 100° with the first type natural corundum. On the other hand, corundum of straight parallel planes described above (Figure cabochons revealing less than six rays on the curved 4). By rotation of the corundum crystal about surface exhibit needle-like inclusions in three orienta­ various axes, especially about the short 4.0 mm axis tions but are not cut in the appropriate direction, of the oval stone, only the first type of structural i.e. with the base of the cabochon at right angles to plane reveals irregular spots or patches, which the c-axis of the crystal. display total internal reflection when the angles of The present paper describes a small blue sapphire the incident ray with the normal are greater than 35° cat's-eye from Burma. A preliminary microscopic (Figure 5). Transparency is observed at smaller investigation disclosed that a light effect resembling inclinations of the face normal versus the microscope chatoyancy is not due to needle-like inclusions axis, i.e. when the angle of the incident ray with parallel to one direction in this extraordinary the primary ray of light is smaller than 35°. This sample. Therefore, a detailed study of the stone was critical angle of ~ 35° corresponds with the critical undertaken in order to clarify the cause of the angle of corundum in contact with air or vacuum, optical properties of the sapphire. which equals 34.4° (cf. Schmetzer, 1986). J. Gemm., 1987, 20, 6 347

fii* m

7: J: Fig. 1. General survey of sapphire cat's-eye from Burma; the sample consists of two parts which are separated by an irregular surface, each part reveals glide planes parallel to the basal pinacoid (0001). In the upper part two sets of growth planes parallel to the hexagonal dipyramids (2241) are present. 36x.

Discussion past. This sample from Sri Lanka, however, was In general, untwinned natural ruby and sapphire only available for a limited time and thus was not crystals are single crystals without different crystal- studied in detail. lographical orientations of different parts of the On the other hand, in synthetic corundum crystals. Natural corundum of the particular type, crystals which were produced by the Verneuil which is described in the present paper, is extremely technique, slight inclinations of different growth rare. In the experience of the authors, only one non- sectors against each other are common. The single crystal of corundum has been observed in the irregularly curved surfaces between these sectors,

Fig. 2. Sapphire cat's-eye from Burma; the two parts of the stone, Fig. 3. Sapphire cat's-eye from Burma; interference striations which are separated by an irregular surface, reveal glide and interference colours are observable at the irregular planes parallel to (0001). The glide planes are inclined boundary between the two parts of the crystal. Crossed against each other forming angles of ~ 169°. 50x. polarizers. 20x. 348348 J.J .Gemrn., Gemm. ,1987,20,6 1987, 20, 6

Fig.Fig. 4.4 . SapphireSapphire cat's-eyecat's-eye fromfrom Burma;Burma; twotwo sets...Qfsetsof growthgrowth planesplanes Fig.Fig . S.5 . SapphireSapphire cat's-eyecat's-eye fromfrom Burma;Burma; irregularirregular spot·spot- andand patch­patch­ parallelparallel toto thethe hexagonalhexagonal dipyramidsdipyramids (2241)(2241) intersectintersect withwith likelike fissuresfissures onon basalbasal glideglide planesplanes showingshowing totaltotal inrernalinternal glideglide planesplanes parallelparallel toto thethe basalbasal pinacoidpinacoid (0001(0001)).. 4Ox.40x . reflectionreflection atat distinctdistinct angles.angles . 70x70x..

whichwhich areare calledcalled small-anglesmall-angle graingrain boundaries,boundaries, limitedlimited toto naturalnatural corundumcorundum withwith intercalatedintercalated displaydisplay interferenceinterference striationsstriations andand interferenceinterference lamellaelamellae ofof boehmiteboehmite alongalong thesethese so-calledso-called partingparting colourscolours underunder crossedcrossed polarizerspolarizers (cf.(cf. Schmetzer,Schmetzer, planesplanes (White,(White, 1979;1979; cf.cf. alsoalso thethe paperpaper ofof Judd,Judd, 1986).1986). A secondsecond characteristiccharacteristic propertyproperty ofof Verneuil­Verneuil- 1895).1895). growngrown corundumcorundum isis thethe presencepresence ofof intersectingintersecting TheThe microscopicmicroscopic observationsobservations ofof twotwo typestypes ofof glideglide planesplanes parallelparallel toto thethe second-ordersecond-order hexagonalhexagonal intersectingintersecting structuralstructural planesplanes inin thethe non-singlenon-single prismprism (1110).(1120). TheseThese prismaticprismatic glideglide planesplanes areare crystalcrystal sapphiresapphire fromfrom Burma,Burma, whichwhich isis describeddescribed inin formedformed atat extremelyextremely highhigh temperaturestemperatures [above[above thisthis paper,paper, suggestsuggest thatthat atat leastleast oneone setset ofof thesethese 2000°C]2000°C] (Scheuplein(Scheuplein andand Gibbs,Gibbs, 1960;1960; StephensStephens planesplanes areare notnot growthgrowth structures.structures. GrowthGrowth structuresstructures andand Alford,Alford, 1964).1964). iinn naturalnatural corundumcorundum areare commonlcommonlyy observableobservable InIn naturanaturall oror syntheticsynthetic corundum,corundum, glidglidee planesplanes paralleparallell ttoo ththee basabasall pinacoipinacoidd (0001)(0001) aass welwelll aass paralleparallell ttoo basabasall facefacess araree produceproducedd bbyy externalexternal paralleparallell ttoo ththee second-ordesecond-orderr hexagonahexagonall prismprism stressstress aatt temperaturetemperaturess abovabovee 900°900°CC (Kronberg,(Kronberg, (1120)(1120),, paralleparallell ttoo ththee rhombohedrorhombohedronn (lOTl)(lOll),, anandd 19571957;; ScheupleiScheupleinn anandd GibbsGibbs,, 19601960)) oorr eveevenn aatt rooroomm paralleparallell ttoo differendifferentt hexagonahexagonall dipyramiddipyrarnidss (hh2El)(hhL1iI).. temperaturtemperaturee (Johnsen(Johnsen,, 19171917;; VeitVeit,, 1922)1922).. BotBothh GrowtGrowthh planesplanes,, howeverhowever,, ddoo nonott displadisplayy irregulairregularr typetypess ooff basabasall anandd prismatiprismaticc glidglidee planeplaness araree showshownn patchepatchess witwithh totatotall reflectioreflectionn aatt distincdistinctt anglesangles.. iinn FigurFiguree 66.. AA thirthirdd typtypee ooff structurastructurall separatioseparationn ThesThesee factfactss supporsupportt aann interpretatiointerpretationn ooff botbothh typetypess planplanee paralleparallell ttoo ththee rhombohedrarhombohedrall facfacee (lOTl(1011)) iiss ooff structurastructurall planeplaness iinn ththee cat's-eycat's-eyee sapphirsapphiree fromfrom

c c

(0001)

(1010> (1120)

FigFig.. 6 6. . SchematiSchematicc drawin drawingg o off basa basall an andd prismati prismaticc glid glidee plane planess an andd glid glidee direction directionss i nin corundu corundumm (afte (afterr Scheuplei Scheupleinn an andd Gibbs Gibbs,, 1960) 1%0). . J. Gemm., 1987, 20, 6 349

Burma as growth planes parallel to the hexagonal References dipyramid z (2241) and glide planes parallel to the Johnsen, A., 1917. Die einfachsten Bahnen der Atome während basal pinacoid c (0001). The different crystal- der Schiebungen im Eisenglanz und Korund. Centralblatt für lographical orientation in both parts of the crystal is Mineralogie, 1917, 433-45. Judd, J.W., 1895. On the structure-planes of corundum. caused by an inclination of structural planes, which Mineralogical Magazine, 11, 49-55. is presumably generated during the glide process. Kronberg, M.L., 1957. Plastic deformation of single crystals of Details of the mechanism of formation of the sapphire: basal slip and twinning. Acta Metallurgica, 5, irregular boundary between both parts of the 507-24. Scheuplein, R., and Gibbs, P., 1960. Surface structure in crystal, however, are unknown at present. A corundum: I, Etching of dislocations. Journal of the American possible explanation of the formation of this Ceramic Society, 43, 458-72. structural feature is a combination of basal Scheuplein, R., and Gibbs, P., 1962. Surface structure in and prismatic gliding, which was artificially pro­ corundum: II, Dislocation structure and fracture of deformed single crystals. Journal of the American Ceramic Society, 45, duced in synthetic Verneuil-grown corundum by 439-52. Scheuplein and Gibbs (1962). Schmetzer, K., 1986. Natürliche und synthetische Rubine - The presence of irregular patch-like fissures with Eigenschaften und Bestimmung. Schweizerbart, Stuttgart. total reflection at distinct angles is responsible for Stephens, D.L., and Alford, W.J., 1964. Dislocation structures in single-crystal Al2O3. Journal of the American Ceramic Society, the optical effect of the cabochon-cut stone, which 47, 81-6. is similar to a cat's-eye in other well known gem- Veit, K., 1922. Künstliche Schiebungen und Translationen in stones such as chrysoberyl and tourmaline. These Mineralien. Neues Jahrbuch für Mineralogie, 45, Beilagebände, irregular fissures are presumably formed on the 121-48. White, J.S., 1979. Boehmite exsolution in corundum. American basal glide planes during the slip process. Mineralogist, 64, 1300-2. Acknowledgements [Manuscript received 21 June 1986.] The authors are grateful to Mr M.P. Steinbach, Idar-Oberstein, who supplied the sapphire cat's- eye from Burma for investigation. Financial support was given by grants of the Wirtschaftsministerium des Landes Rheinland-Pfalz, FRG.

NEW GEMMOLOGY COURSE The Gemmological Association of Great Britain is proud to announce that it has introduced a new home study course in gemmology. This prepares students for the examinations leading to the ^ward of the Association's Fellowship Diploma. The new course is radically different from other gemmological courses, and presents a new, friendly, step- by-step approach to learning that should be welcomed by students all over the world.

F or further details, contact the Education Department, Gemmological Association of Great Britain, Saint Dunstan's House, Carey Lane, London EC2V 8AB. Tel: 01-7264374. Cables: GEMINST. 353500 JJ.. Gemm.Gemm.,, 1987,20,61987, 20, 6

OnOn thethe colourcolour ofof gemstonesgemstones andand Nelson'sNelson's 'body'body colour'colour'

Kurt Nassau, Ph.D.Ph.D.

BernardsvilleBernardsville,, NNJJ 0792407924,, USUSAA

DDrr Nelson'Nelson'ss articlearticle oonn ththee measurementmeasurement ooff colourcolour whichwhich hehe doesdoes notnot definedefine.. PartPart ooff hihiss FigureFigure 9,9, iinn gemstonesgemstones (Nelson,(Nelson, 1986)1986) coverscovers manymany ofof thethe shownshown herheree asas FigureFigure 1,1, appearsappears ttoo givgivee thethe answer.answer. complexitiescomplexities involveinvolvedd iinn thithiss perplexinperplexingg problemproblem IfIf a beabeamm ooff whitewhite lightlight entersenters ththee tabltablee facetfacet nearnear itsits anandd givegivess hihiss viewviewss ofof a solutionsolution fofor'r ' ...... takintakingg thethe centrecentre atat a smallsmall angleangle anandd isis returnedreturned alongalong thethe firstfirst stepssteps towardstowards establishinestablishingg internationalinternational samesame pathpath bbyy frustratedfrustrated reflectionreflection fromfrom a diffusingdiffusing standardsstandards forfor ththee quantitativquantitativee descriptiodescriptionn ooff gem­gem- whitewhite rubber*rubber* iinn contactcontact withwith ththee backback ooff thethe stone,stone, stonestone bodbodyy colour'.colour'. InIn hihiss articlarticlee a numbernumber ooff thethenn ththee coloucolourr carriedcarried bbyy thithiss beabeamm emergingemerging fromfrom importanimportantt aspectaspectss ooff coloucolourr measurementmeasurementss areare thethe tabletable isis Nelson'Nelson'ss 'bod'bodyy colour'.colour'. PresumablyPresumably thisthis discusseddiscussed.. I ddoo notnot agreeagree witwithh alalll ththee statementsstatements hehe tertermm iiss intendeintendedd ttoo distinguishdistinguish ththee coloucolourr seenseen nearnear makesmakes andand feefeell thatthat somesome significantsignificant mattersmatters havehave thethe centrecentre ofof thethe tabletable facetfacet fromfrom thathatt perceiveperceivedd nearnear beebeenn omittedomitted,, bubutt I wiswishh ttoo commencommentt herehere onlonlyy onon thethe edgesedges oorr ririmm ooff ththee stone.stone. TherTheree areare threethree ononee specificspecific aspecaspectt ofof hishis approach.approach. separateseparate problemproblemss withwith thithiss approach,approach, anyoneany one ooff ItIt appearsappears ttoo meme thathatt NelsoNelsonn hahass fallefallenn intintoo a traptrap whicwhichh iiss fatalfatal ttoo thethe validityvalidity ofof thisthis model.model. toto whicwhichh wwee scientistsscientists unfortunatelyunfortunately areare ratherrather First,First, 'what we see' whenwhen lookinlookingg atat a gemstonegems tone proneprone.. LeLett usus callcall itit thethe irrelevant model trap andand doedoess includeinclude thethe edgeedge oror ririmm region;region; iiff thisthis isis clarifyclarify thithiss asas follows.follows. FrequentlyFrequently,, iinn scientificscientific andand differentdifferent iinn huhuee oror inin intensityintensity fromfrom ththee centralcentral technologicatechnologicall research,research, ononee proposeproposess a 'model''model',, anan regioregionn ofof thethe gemgem,, aass itit usuallusuallyy is,is, itit wilwilll clearlyclearly idealizedidealized approachapproach ttoo whawhatt ononee isis tryingtrying ttoo achieve.achieve. influencinfluencee thethe overalloverall coloucolourr perceptioperceptionn ouourr brainbrain SuchSuch a modemodell isis usuallusuallyy aann interpretatiointerpretationn ooff whatwhat receivereceivess frofromm ouourr eyeeyess anandd thuthuss cacann hardlhardlyy bebe oneone feelfeelss araree ththee mostmost importantimportant aspectaspectss ooff thethe ignored.ignored. TwoTwo stonesstones coulcouldd easilyeasily havhavee thethe samesame probleproblemm anandd includesincludes thethe relationshiprelationship ofof thesethese 'bod'bodyy colour'colour' witwithh significantlysignificantly differentdifferent edgeedge aspectsaspects ttoo characteristiccharacteristicss thatthat cacann bbee measuredmeasured.. TheThe colourcolourss anandd thereforetherefore givegive quitequite differendifferentt overalloverall nextnext stepstep involvesinvolves a studystudy onon hohoww toto perforperformm thesethese coloucolourr impressions.impressions. measurementmeasurementss andand fromfrom thesthesee measurementmeasurementss toto Second,Second, ththee 'bod'bodyy colour'colour' approachapproach asas useusedd bbyy deducededuce thethe naturenature ofof ththee importanimportantt aspects.aspects. NelsoNelsonn excludesexcludes ththee effecteffectss ooff dispersiodispersionn anandd ooff AAtt thisthis poinpointt ththee modemodell isis completecomplete.. ThThee tastaskk isis,, pleochroispleochroismm (Nassau(Nassau,, 1983).1983). TheseThese areare,, howeverhowever,, a however,however, nonott yeyett finished,finished, forfor iitt remainsremains toto bebe parpartt ofof 'what we see\see'. AAss ononee example,example, thethe demonstratedemonstratedd thathatt thethe modelmodel doedoess indeeindeedd correspondcorrespond pleochroispleochroismm isis presenpresentt asas dichroisdichroismm inin ththee casecase ooff ttoo ththee realitrealityy iitt waswas intendeintendedd toto represent.represent. ThisThis lastlast ruby;ruby; a piecpiecee ooff rubyruby roughrough showsshows itsits besbestt colourcolour stepstep hahass nonott beenbeen performedperformed bbyy NelsoNelsonn andand iitt iiss easyeasy whewhenn ththee cutcut iiss orientedoriented soso thathatt ththee purple-repurple-redd ofof thethe ttoo showshow thathatt therethere areare fatalfatal flaws inin attemptinattemptingg toto ordinarordinaryy rarayy iiss dominandominantt ratherrather thathann ththee orange-redorange-red movmovee frofromm hihiss modelmodel bacbackk ttoo reality.reality. ThesThesee flaws ofof ththee extraordinarextraordinaryy ray.ray. ThiThiss aspectaspect alsalsoo makesmakes anyany involvinvolvee oneone conceptconcept discusseddiscussed bbyy NelsoNelsonn atat lengthlength suchsuch measurementmeasurement techniquetechnique notnot particularlparticularlyy usefuluseful andand ononee otherother whichwhich isis nevernever specificallyspecifically discussed,discussed, foforr rough,rough, aass suggestedsuggested bbyy NelsonNelson,, sincesince a rangrangee ooff althoughalthough itit isis aatt ththee centrcentree ofof hihiss approach.approach. colourscolours couldcould bbee obtaineobtainedd dependingdepending oonn thethe NelsoNelsonn clearlyclearly recognizerecognizess thathatt 'Colour'Colour iiss what we orientatioorientationn ooff ththee windowwindowss oonn ththee roughrough withwith see' (his(his emphasis).emphasis). ItIt iiss curioucuriouss thereforthereforee thathatt hehe respecrespectt ttoo ththee opticoptic axesaxes.. doedoess nonott explainexplain whwhyy ththee coloucolourr thatthat iiss measuremeasuredd inin hishis modemodell isis thethe 'body'body colour'.colour'. AnAndd herheree iiss thethe problem:problem: whewhenn wwee loolookk atat a facetefacetedd gemgemstone,s tone, wwee *Even*Even iiff thethe whitewhite rubberubberr werewere ttoo actact asas anan integratinintegratingg spherspheree doesdoes see much more than just a body colour. (possibl(possiblyy impliedimplied bbyy Nelson'Nelson'ss ususee ofof ththee wordword multiple inin see much more than just a body colour. 'frustrated'frustrated multiplmultiplee internainternall reflectionreflection'' butbut apparentlyapparently negatenegatedd byby BeforBeforee goingoingg anyany further,further, wewe needneed toto knowknow subsequensubsequentt statements)statements),, thethe remarkremarkss followinfollowingg wouldwould stillstill apply,apply, exactlyexactly whatwhat NelsoNelsonn meansmeans bbyy 'body'body colour',colour', a termterm althoughalthough witwithh minominorr modifications.modifications. J.J. Gemm.,Gemm., 1987,20,61987, 20, 6 351351

\ I \ f \ J •\

FIG. I FIG. 2

Fig.Fig. I.1. TheThe pathpath throughthrough a gemgem inin Nelson'sNelson's 'body'body colour'colour' Fig.Fig. 2.2. TypicalTypical viewinviewingg pathspaths inin a gem,gem, illustratedillustrated forfor a diamond;diamond; technique.technique. bothboth pathspaths cancan bebe traversedtraversed iinn eithereither direction.direction.

TheThe thirdthird vitiatingvitiating aspectaspect isis thethe questionquestion ofof thethe TheseThese areare thethe reasonsreasons whywhy I believebelieve itit toto bebe opticaloptical patpathh withinwithin ththee gemstone.gemstone. ThisThis mightmight notnot obviousobvious thatthat itit willwill alwaysalways bebe necessarynecessary ttoo useuse thethe mattermatter ifif jusjustt a singlesingle opticaloptical pathpath werewere involved,involved, eyeeye toto comparecompare thethe overalloverall colourcolour impressionimpression bubutt itit isis not.not. TheThe exacexactt returningreturning patpathh ofof FigureFigure 1 asas producedproduced bbyy a gemstonegemstone viewedviewed as a whole withwith usedused byby NelsonNelson isis notnot presentpresent underunder normanormall viewingviewing somesome otherother kindkind ofof referencereference material,material, bebe itit a light­light- conditionsconditions becausebecause (a)(a) thethe headhead ofof thethe viewerviewer blocksblocks producedproduced image,image, a setset ofof mastermaster stones,stones, oror anan thatthat lightlight whichwhich couldcould producproducee a precisprecisee returningreturning opaqueopaque oror transparenttransparent pigmentedpigmented chartchart ofof somesome pathpath andand (b)(b) frustratedfrustrated reflectionreflection isis notnot present.present. type.type. ThereThere are,are, admittedly,admittedly, problemproblemss iinn eacheach ofof ThereThere isis a widewide rangerange ofof actualactual pathpathss contributingcontributing toto thesethese approaches,approaches, andand a ververyy specializedspecialized trainingtraining ththee perceivedperceived colour,colour, onlyonly twotwo ofof whichwhich areare shownshown willwill bbee requiredrequired soso thatthat centrcentree colour,colour, edgeedge colour,colour, schematicallyschematically inin FigureFigure 2.2. ThisThis involvesinvolves notnot onlyonly pleochroism,pleochroism, refractiverefractive index,index, dispersion,dispersion, andand allall pathspaths approximatt;lyapproximately perpendicularperpendicular toto thethe table,table, butbut otherother opticaloptical effectseffects presentpresent cancan bebe incorporatedincorporated alsoalso pathspaths atat leastleast partiallpartiallyy nearnear paralleparallell ttoo thethe table,table, intointo a singlesingle visually-perceivedvisually-perceived colourcolour on which thusthus samplingsampling differentdifferent partpartss ofof thethe pleochroism.pleochroism. different observers cancan agree. agree. The The colourcolour measure­measure­ NotNotee thatthat pathspaths emergingemerging fromfrom thethe tabletable maymay havehave mentment problemproblem hahass beenbeen satisfactorilysatisfactorily solvedsolved inin enteredentered ththee gemstonegemstone nearnear thethe edgeedge andand vicevice Versaversa.. manymany otherother systems,systems, asas mentionedmentioned byby NelsonNelson;; hehe AlsoAlso notenote thatthat pleochroismpleochroism doesdoes produceproduce significantsignificant should,should, however,however, notnot permipermitt himselfhimself toto bbee takentaken inin colourcolour variation,variation, eveneven thoughthough thethe lighlightt isis notnot bbyy thethe deceptivelydeceptively simplesimple gemstonegemstone whichwhich posesposes polarized.polarized. problemsproblems farfar moremore complexcomplex thanthan dodo anyany ofof thesethese ExceptExcept inin rarerare andand unusualunusual circumstances,circumstances, thethe otherother systems.systems. resultresult ofof thesethese threethree effectseffects willwill bebe thatthat thethe 'body'body colour'colour' determineddetermined byby followingfollowing Nelson'Nelson'ss procedureprocedure willwill notnot bebe thethe samesame asas thethe overalloverall colourcolour impressionimpression ReferencesReferences producedproduced bbyy thethe gemstonegemstone underunder ordinaryordinary viewingviewing NelsonNelson,, J.B.J.B. 1986.1986. TheThe colourcolour barbar inin thethe gemstonegemstone industry.industry. Journal of Gemmology, 20,20, 4,4, 217-37.217-37. conditions.conditions. Yes,Yes, itit wouldwould indeedindeed bebe convenientconvenient ifif Nassau,Nassau, K.K. 1983.1983. The physics and chemistry ofof color.color. Wiley, Wiley ,New New colourcolour measurementmeasurement couldcould bbee takentaken overover byby whatwhat York.York. NelsoNelsonn callscalls a 'dispassionate'dispassionate machine',machine', butbut thisthis wouldwould bebe usefuluseful onlyonly ifif itit gavegave anan answeranswer relevanrelevantt toto thethe questioquestionn beingbeing askedasked:: 'what'what colour dodo wewe see?'see}' [Manuscript[Manuscript receivedreceived 4 March 1987.]1987.] 352 J. Gemm., 1987, 20, 6

The two-colour beryl from Orissa, India

Dr R. Aliprandi, GG, FGA,* and G. Guidi†

*Italian Gemmological Institute, Rome, Italy †National Committee for Nuclear Energy, Rome, Italy

Introduction Orissian deposits furnish gem beryls which occur Numerous gemstones show different colours in in colourless and yellow, and occasionally the the same crystal, sometimes differing from end to crystals show lighter hued yellow colour zones, end, at other times in concentric layers as witness to parallel to the basal plane. the varying chemical-physical processes involved in their formation. 'Water melon' tourmaline is a well- Experimental known example of a gemstone showing different The origin of colour in beryl has recently been chromatic zones, colours ranging from red to pink revised by Goldman et al. (1978), supporting the and green in many different shades. conclusion that iron is responsible for different The corundum group sometimes produces speci­ colours in beryls when located primarily in the mens of different colours of yellow, blue and pink, aluminium site, though the colour is derived mainly occasionally mixed by the reflection of the facets in from the amount of ions located in the channels the faceted stones. Recently two-coloured quartzes formed by the silicon ions. Less often specimens of have made their appearance in the trade, their natural origin showing sectored variation in colour colour being correlated with different oxidation and properties like the two samples from the Orissa states of iron. As in quartz, iron and its oxidation State are reported. state is responsible for the colour of beryl, a mineral The two beryls examined occurred in pegmatite incapable of possessing any colour in its pure state. bodies in the Pulbani mining area and are associated The occurrence of beryl in the Pulbani district of with cordierite, corundum, garnets, quartz and Orissa State was limited to a few localities in the chrysoberyl (cafs-eye and alexandrite). The investi­ Eastern Ghats region, and the particular samples gated specimens (Figure 1) weighing respectively were mined in the Gopalbur and Lukapara area. 4.13 and 3.97 ct, were cut with an octagonal outline The region is characterized by a complex of with long parallel facets (step cut) clearly showed metamorphic rocks such as charnockite-khondalite- the two-colour separation line running across the leptynite associated with rocks rich in hydrous middle of table (Figure 2). minerals. The charnockite shows intrusive relation­ With the intent of a preliminary checking of the ship towards the khondalite and has itself undergone greatest variation between the yellow and colourless post-magmatic changes such as albitization and areas of each sample, the refractive indices were myrmekitization (Crookshank, 1938). The char- evaluated using oriented laminae cut parallel to the nockites have also formed hybrid gneisses with optical axis of the crystals. Preliminary optical khondalites and sometimes with other ancient observations led to recognition of elongated fibrous gneisses. In this region crystalline limestones, inclusions, strictly following the direction of the c- cordierite gneisses, sapphirine bearing rocks, and axis, referable to growth-tubes which are spread nepheline-syenite are also found. through the entire volume of the beryl, and are The beryl-bearing and mica pegmatite bodies of filled by biréfringent material. variable size are probably localized along the Cavities of different sizes with prismatic habit fracture planes of the metamorphic rocks. Green orientated with elongation direction parallel to shales and medium to coarse-grained yellowish c-axis of the beryl matrix are also present. It seemed sandstones, having pebbles and conglomerates of appropriate to conduct the present study to deter­ Gondwana group of rocks, also occur in the basin mine the mineralogical characteristics of these two- with faulted boundaries on east and west (Krishnan, colour beryls to define their formational conditions. 1982).

© Copyright the Gemmological Association ISSN: 0022-1252 J. Gemm., 1987, 20, 6 353

Figs. 1 (a) and (b). Two-coioured beryls from Orissa.

Table 1 summarizes the gemmological properties of the colours gave the values of 1.570, 1.573 and of one of the two samples probably cut from the 1.580. Microscopic examination of the specimens same crystal. The density measured by the hydro­ immersed in benzyl benzoate revealed a barrier of static method gave a value of 2.699±0.002 g/cm3 acicular growth-tubes all oriented parallel to the while the RI reading taken with a hemisphere main growth axis. They seem to originate from the refractometer using monochromatic sodium light, same plane parallel to the (0001) pinacoid protruding turned out to show different values corresponding from a layer of blocking guest microlites. Further to the different regions of the specimen. The electron microprobe analysis (EPMA) investigation shadow edge gave indices for extraordinary ray ne at confirmed the presence of acicular parallel growth 1.574 and for the ordinary ray nw at 1.580 on the tubes, some of them breaking the surface of the yellow portion, ne 1.570 and nw 1.575 on the specimen, having the same composition as the host colourless portion. crystal. A section of a tube-like inclusion breaking An additional reading taken across the interface the surface of the beryl is shown in Figure 3.

Fig. 2. Photomicrograph of some acicular inclusions reaching the middle of table and forming the border-line between yellow and colourless areas. 45x. 354 J. Gemm., 1987, 20, 6

Table 2. Chemical analyses of two-coloured beryl from Orissa

Colourless Yellow Si02 64.16 64.53 TiOz tr. tr. A1203 19.90 19.32 Cr203 — — FeOf 0.13 0.67 BeO* 12.96 12.94 MnO — — MgO 0.10 0.11 CaO 0.12 0.09 Fig. 3. Section of an acicular inclusion protruding through the Na20 0.13 0.12 (0001) plane. SEM photograph, lOOOx. K20 0.16 0.12 EPMA quantitative analysis performed on both Li20 nd nd colourless and yellow sectors has shown different Cs20 nd nd chemical compositions. The yellow area reveals a higher concentration of iron, 0.67 wt.%, against Numbers of ions on the basis of 36 (0}I 0.13 wt.% in the colourless area, while a higher percentage of aluminium is reported in the colour­ Si 11.571 11.594 less, 19.90 wt.%, against 19.32 wt.% in the yellow Ti — — area (Table 2). Figure 4 shows a quantitative Al 4.225 4.102 Cr — — elemental distribution of A1203 and FeO through the two different coloured areas. Fe 0.022 0.097 Be 5.612 5.581 Mn — — Mg 0.022 0.032 Table 1. Gemmological properties of Ca 0.022 0.022 two-coloured beryl from Orissa Na 0.022 0.022 K 0.022 0.011 Crystal system Hexagonal 1 Li — — Hardness 7 /2(Mohs) Cs — — Toughness Strong but brittle 2 9.947 9.867 Cleavage Poor S = sum of metal ions other than Si Fracture Conchoidal 3 Density 2.699±0.002 g/cm ttotal iron as FeO Transparency Good *dosed with pyrophosphate Optical character Uniaxal negative Pleochroism Absent Long-wave ultraviolet Inert Conclusion (365 nm) The pair of unusual gemstones reported in this Short-wave ultraviolet Inert paper have been cut in order to place the interface, (253.7 nm) where the colours turn from colourless to yellow, Visible spectrum 540nm(Fe) exactly in the middle of the table facet producing a Optical observation Elongated fibrous pleasant chromatic effect. Such interface proved to inclusions, minute be formed by a barrier of included crystals pre­ unidentified inclusions, existing at the start of growth of the beryl crystal, some K-feldspar some of them identified as K-feldspar. Such barrier Colourless area 0.005 of guest microlites produced a blocking effect in the Birefringence Yellow area 0.006 growing beryl causing crystallization of growth n 1.570±0.002 tubes within the embedding crystal. Colourless area e 1^1.57510.003 RI Acknowledgements n 1.574±0.004 The constructive suggestions of Prof. G. Graziani, Yellow area e na)1.580±0.002 Dept of Earth Sciences, University of Rome, are gratefully acknowledged. J. Gemm., 1987, 20, 6 355

FeO wt.% 1 0.60

0.50

0.4 0

0.3 0 colourless I yellow

0.2 0

20.0 _

19.8

19.6 100/Xm Al - P3 19.4 1i — — distance

Fig. 4. Diagram showing the increased concentration of FeO in the yellow portion of the bi-coloured beryl compared with the colourless part, and the greater concentration of A1203 in the colourless compared with the yellow part.

References Crookshank, H., 1963. Geology of Southern Bastar and Jeypore from Bailadila Range to the Eastern Ghats. Memoirs of the Geological Survey of India, 87, 1-150. Krishnan, M.S., 1982. Geology of India and Burma. CBS Publisher, New Delhi. Goldman, D., et al., 1978. Channel constituents in beryls. Physics and Chemistry of Minerals, 3, 225-35.

[Manuscript received 4 February 1986.] 353566 JJ.. Gemm.Gemm.,, 1987,20,61987, 20, 6

NoteNotess frofromm ththee LaboratorLaboratoryy - 1100

Kenneth ScarrattScarratt,, FGAFGA

ThThee GeGemm TestinTestingg LaboratoryLaboratory ooff GreatGreat Britain,Britain, 2277 GrevilleGreville Street,Street, LondonLondon,, ECINEC1N 8S8SUU

Saussurite,Saussurite, a rockrock composedcomposed essentiallyessentially ofof albitealbite anandd thathatt itit isis notnot regardedregarded asas a materiamateriall ttoo bebe anandd zoisitzoisitee anandd whicwhichh cacann closelyclosely resemblresemblee jadeitejadeite considereconsideredd iinn ititss ownown rightright.. HoweverHowever,, a descriptiondescription anandd nephrite,nephrite, iiss usuallyusually describeddescribed onlonlyy iinn briefbrief ooff saussuritesaussurite iinn 19741974 (Jobbin(Jobbinss anandd RutlandRutland,, 1974)1974) termtermss inin ththee sectionssections ooff textbookstextbooks whicwhichh dealdeal withwith whicwhichh includeincludess coloucolourr photographsphotographs,, adequatelyadequately ththee jadejades.s ratheratherr thanthan underunder itsits owownn headingheading,, saysay inin fulfilfulfilss ththee neeneedd foforr moremore detailedetailedd informationinformation ooff thisthis ththee sectionssections dealindealingg withwith 'unusua'unusuall minerals'minerals' (e.g.,(e.g., materialmaterial.. WebsterWebster,, 1983;1983; G.F.G.F. HerbertHerbert Smith,Smith, 1972).1972). SausSaus­­ JobbinJobbinss andand RutlandRutland examinedexamined sixsix carvingcarvingss iinn anan surite'ssurite's representatiorepresentationn iinn thesthesee workworkss tendtendss firstlyfirstly attractivattractivee greegreenn materiamateriall overover a periodperiod ooff twtwoo yearsyears toto indicatindicatee thatthat itit willwill onlyonly bbee metmet witwithh rarelyrarely,, andand atat ththee InstitutInstitutee ooff GeologicaGeologicall Sciences,Sciences, London.London. secondlysecondly thathatt ththee positionposition itit holdholdss iinn ththee gem­gem- SomeSome ooff thesethese hadhad beebeenn soldsold iinn HongHong KonKongg oror ChinaChina mologicalmological worlworldd isis ononee ooff a substitutesubstitute foforr thethe jadejadess aass jadjadee oorr 'ne'neww jade'jade',, bubutt a detaileddetailed examinationexamination proveprovedd thatthat theythey werweree composedcomposed ooff eitheeitherr dominantdominant oorr veryvery significantsignificant proportionproportionss ofof saussurite.saussurite. TheirTheir reportreport oonn ththee propertiepropertiess ooff thesthesee sixsix itemitemss anandd twotwo standarstandardd specimensspecimens frofromm thethe collections,collections, aass welwelll aass onon ththee propertiepropertiess revealerevealedd bbyy manmanyy analyseanalysess ooff saussuritsaussuritee sincsincee iitt wawass describeddescribed bbyy H.B.H.B. dede SaussureSaussure inin 1780,1780, emphasiseemphasisess thethe possiblpossiblee variationsvariations iinn thethe compositioncomposition ofof thithiss material,material, SG,SG, RI,RI, hardnesshardness,, absorptioabsorptionn spectrumspectrum anandd generagenerall apap­­ pearancepearance.. UsinUsingg X-raX-rayy diffractiodiffractionn theitheirr examinationexamination revealerevealedd compositionscompositions whicwhichh includedincluded thethe presencepresence ofof zoisite,zoisite, Ca-richCa-rich plagioclaseplagioclase,, clino-enstatite,clino-enstatite, diopdiop­- sidsidee andand chloritechlorite,, whilswhilstt theitheirr normanormall gemmologicalgemmological examinatioexaminationn revealerevealedd SGsSGs ranginrangingg fromfrom 2.85-3.22,2.85-3.22, FigFig.. 1.1. A strinstringg ooff ononee hundrehundredd saussuritesaussurite beadbeadss showinshowingg thethe RIsRIs ranginrangingg frofromm 1.55-1.561.55-1.56 forfor ththee whitwhitee areaareass toto variationsvariations iinn colour.colour. 1.68-1.701.68-1.70 forfor ththee darkerdarker areaareass (although(although thethe latterlatter

FigFig.. 22.. A saussuritesaussurite carvingcarving ofof a seateseatedd ladylady,, mostlmostlyy whitwhitee inin Fig.Fig. 3.3. ThThee bacbackk ofof ththee carvincarvingg iinn FigurFiguree 2.2. coloucolourr butbut withwith severalseveral areasareas ooff greegreenn varyingvarying inin shadeshade fromfrom lightlight ttoo veryvery dark.dark.

© CopyrightCopyright thethe GemmologicalGemmological AssociationAssociation ISSN:ISSN: 0022-12520022-1252 J. Gemm., 1987, 20, 6 357

'» 41

Fig. 4. A saussurite carving of two birds in a tree showing the variations in colour, cf. Figures 1, 2 and 3. results were not felt to be reliable), a hardness of X-ray powder diffraction analyses, were identified between 5 and 7, and absorption spectra varying as saussurite. The first, which was submitted by a from being 'not distinctive', to 'Cr lines in red' with different client to the other two, was a string of one 'absorption of blue/violet', to a 'line in deep violet'. hundred round drilled beads with a total weight of It is clear then that saussurite, unlike the majority 422.74 ct (Figure 1). The second was a carving of a of materials handled by gemmologists, does not seated lady (Figures 2 and 3) with a weight of have convenient constants by which it may be 445 gm and dimensions of 12 cm height, 14 cm identified; indeed it is its variable properties width, and 5 cm depth. The third was a carving coupled with its mottled green and white appearance depicting two birds in a tree (Figures 4 and 5) which that first give hints towards its identity. However, weighed 380 gm and had dimensions of 15 cm these are only hints and as stated by Jobbins and height, 17 cm width and 10 cm depth. Rutland thirteen years ago in remarking about the specialized equipment needed to identify their specimens, 'The material will create problems in the future for many gemmologists and dealers'. A mottled green and white rock which had some properties similar to those of saussurite was examined by Robert E. Kane in 1985 (Fryer et al., 1985). In this case X-ray diffraction revealed the major constituents to be a white plagioclase feldspar and a green muscovite mica and the material was therefore only reported upon as being a rock consisting of two or more minerals. After not having examined any examples for some time, we were recently asked to examine three mottled green and white items which, following Fig 5. A close view of the saussurite carving in Figure 4. 358 J. Gemm., 1987, 20, 6

The general appearance and colour distribution as a series of bright lines extending towards the red of the three items examined recently, are adequately end, and in diminishing strength from the end displayed in Figures 1 to 5. Whilst zoisite was member of the series. He recorded the wavelength proved to be present by X-ray diffraction, several of this main line as 5750Ä. Our observations were distant vision RI readings failed to produce a value similar for the 4.75 ct stone. The spectrum which greater than 1.60. The approximate RIs for the we obtained by bathing the stone in white light three items varied between 1.57 and 1.60. The filtered through copper sulphate solution may be absorption spectrum as seen with the hand spectro­ described as a clear and sharp bright line at 575 nm scope varied greatly, not only between the items but and a bright 'patch' between 590 and 650 nm. also between areas on each item. The absorption Anderson stated that it was possible that the spectrum of the beads in Figure 1 revealed only a larger of his stones came from the old Golconda vague band in the blue and this was also true of mines of India and that experiments had revealed some areas of the carving in Figures 4 and 5, but in the stone to have the ultraviolet transparency other areas of this same carving the spectrum characteristics of a type II diamond. It is said that typical of chromium could be observed in the red. this new crystal was also found in India, and, as In the absorption spectrum of some of the areas in with Anderson's stone, ultraviolet transparency the carving in Figures 2 and 3 a strong band could tests revealed type II diamond characteristics. be seen centred at 442.1 nm. As always the Laboratory's main interest with coloured diamonds is in the area of colour origin - is • • • the diamond coloured naturally or artificially? It is particularly interesting to be able to observe any During 1986 we were fortunate to be shown a coloured diamond both before and after cutting and rather large rough diamond, which appeared to be a even more so when the original rough shows clear light brownish colour. The crystal which weighed signs of having been naturally in the presence of 73.50 ct can be seen in Figure 6. Upon examination radioactivity as some stage in its history. it was found that the surface was spotted with When a type lb diamond is irradiated and brown radiation marks, and the degree of influence annealed, depending upon the strength of the these had on the actual colour of the crystal was not original yellow body colour and how heavy an fully understood until after the crystal had been cut. irradiation is used, either a pink or a mauve The first finished stone to be cut from the crystal artificially coloured diamond will be produced. was a 4.75 ct pear shape (Figure 7) and when this Such treated pink diamonds are easily identified was graded for colour and clarity it was found to be a because the irradiation and annealing changes the Taney Light Pink', and Internally Flawless'. typical lb absorption spectra and induces a strong None of the brown radiation marks were left on the sharp line at 637 nm and further lines at 595, 575 cut stone and the 'light pink' was in fact the true and 503 nm, the last three of which sit on a broad body colour of the diamond and not the light absorption band centred near 560 nm. The 637 line brownish colour of the uncut crystal. is reported to be associated with isolated substitutional In following our routine testing procedures for nitrogen (Collins, 1982). coloured diamonds we noted that the fluorescence On many occasions over the last ten years, both and absorption characteristics of this stone were with the hand spectroscope and the spectrophoto­ similar to those of two pink diamonds described by meter, we have recorded the 637 nm line in many Anderson twenty seven years ago (Anderson, naturally coloured yellow and brown type lb 1960). They were similar also to those often natural diamonds when they have been held at low pink stones examined in the Laboratory over the temperatures. Even at 120K, though, the 637 line past ten years, but these were by no means in such stones is generally very weak (Scarratt, characteristic of pink diamonds in general. This 1984, pi 10). Until now, only on one occasion have new stone fluoresced a very strong orange under we observed a naturally occurring 637 line in other short-wave ultraviolet light and a medium strength than a yellow or brown stone and in that case it was a orange under long-wave ultraviolet. The first of the 'green' stone, in which the colour was due to two stones described by Anderson in 1960 weighed included material. However, when the 4.75 ct light 34.64 ct and he stated the fluorescence to be 'a pink stone was examined at low temperatures on the strong orange-yellow or "apricot" '; the second spectrophotometer, despite it appearing to have stone was smaller at only 2.83 ct but had similar type II diamond characteristics in its ultraviolet fluorescence characteristics. When Anderson ex­ transparency and in general terms also in its visible amined the fluorescence of his stones with a hand spectrum, this naturally coloured pink diamond spectroscope interesting and similar emission spectra recorded peaks, if only very weakly, at 637, 575, were revealed for both. He described the spectrum and 503 nm (Figure 8). J. Gemm., 1987,20,6 359

1·15

Pink Diamond

~ U =~

-eQ rJ'l ~

750I

(}99::t1::;:------=---J... 390 Nanometres 750I

Fig. 8. The absorption curve of the 'Fancy Light Pink' pear-shaped diamond in Figure 7. The curve was obtained using a Pye Unicam PU8800/03 UV/visible spectrophotometer (Basil Anderson model) with a speed of 0.5 nm/s and a bandwidth of 0.5 om at approximately l20K. The path length was approximately 9 rnm. 363600 J.J. Gemm.Gemm.,, 1987 1987,20,6, 20, 6

FigFig.. 6.6. A 73.573.533 cctt roughrough 'ligh'lightt pinkpink'' diamonddiamond witwithh browbrownn naturanaturall radiatioradiationn markmarkss oonn ththee surfacesurface.. Photograph by Mr M.M . Gould of M. Vainer Ltd.Ltd.

Fig.Fig .7. 7 . AA pla plastistic cmodel mode lof o fthe the diamond diamond in in Figure Figure 6 6 from from which which the the three three unfinished unfinished stones stone sand and the the 4.75 4.7 5ct c tpear-shaped pear-shaped diamond diamond in in from fron t were cut. J. Gemm., 1987, 20, 6 361

Fig. 9. Brown natural radiation marks on the 'skin' of one of the Fig. 10. A 'red' beryl-on-beryl composite stone seen here partly polished diamonds in Figure 7. immersed in benzyl benzoate. The rich red junction can be seen following the girdle.

To our knowledge this is the first time that a line at 637 nm has been observed in a naturally coloured pink diamond: in all other cases of pink diamonds where a line has been recorded at this wavelength the coloration has been due to man-induced irradiation and annealing. For the record we asked if we could examine the remaining pieces of the crystal before they became finished stones, these can be seen in Figure 7 with a plastic model of the crystal in the background. Brownish radiation marks could still be seen on the uncut surfaces of the three unfinished stones (Figure 9): all behaved in the same way as the 4.75 ct stone when bathed in ultraviolet light, and similar emission spectra were also produced. Fig. 11. The crown of the composite stone in Figure 10 is relatively free of inclusions whereas the pavilion, as seen here, contains innumerable two-phase inclusions. The edge of the junction can be seen as a curved red line at An interesting and quite effective ruby imitation the top of the figure, and the pinkish coloration below this is in the plane of the junction. The stone is was given to the Laboratory collection recently. It photographed immersed in benzyl benzoate. was a composite stone in which both the crown and pavilion were made from near colourless beryl (Figure 10) and these were joined at the girdle with a rich red adhesive. The refractive indices were 1.580-1.586 for the crown and 1.584-1.590 for the pavilion. Internally the crown was comparatively free from inclusions, whereas included in the References pavilion were innumerable two-phase inclusions Anderson, B.W., 1960. Luminescence of a large pink diamond. (Figure 11). Journal of Gemmology, VII, 6, 216-20. Collins, A.T., 1982. Colour centres in diamond. Journal of Gemmology, XVIII, 1, 37-75. Acknowledgements Fryer, C.W., Crowningshield, R., Hurwit, K.N. and Kane, Thanks are due to Mr S.J. Kennedy for the R.E., 1985. Gem Trade Lab Notes. Gems and Gemology, production of the absorption curve of the 4.75 ct XXI, 3, 173. Jobbins, E.A. and Rutland, E.H., 1974. Saussurite as a jade pink diamond and to Mr I. Shenker for the simulant. Journal of Gemmology, XIV, 1, 1-7. production of the X-ray powder diffraction details Scarratt, K. 1984. Notes from the Laboratory. Journal of of the saussurite. Figure 6 was taken by Mr M. Gemmology, XIX, 2, 110. Gould of M. Vainer Ltd. We are also indebted to Smith, Herbert G.F., 1972. Gemstones, 14th edn, Chapman and Hall, London. the firms of M. Vainer Ltd for allowing us to Webster, R., 1983. Gems, their sources, descriptions and identification, examine the large pink diamond and to E.A. 4th edn, Butterworths, London. Thomson Ltd for the gift of the beryl composite stone. [Manuscript received 14 January 1987.] 362362 J.J. Gemm.,Gemm., 1987,20,61987, 20, 6

ColourColour andand irradiation-inducedirradiation-induced defectsdefects inin topaztopaz treatedtreated withwith high-energyhigh-energy electronselectrons

Dr Karl SchmetzerSchmelzer

InstituteInstitute ofof MineralogyMineralogy andand Petrography,Petrography, UniversityUniversity ofof Heidelberg,Heidelberg, WestWest GermanyGermany andand DeutscheDeutsche StiftungStiftung Edelsteinforschung,Edelsteinforschung, Idar-Oberstein,Idar-Oberstein, WestWest GermanyGermany

AbstractAbstract In topaz irradiatedirradiated with with electrons electrons in inthe the 10 10to 20to mega­20 megaelectronvolttoto producproducee lighterlighter shadesshades ofof blueblue (cf.(cf. alsoalso NassauNassau electronvolt rangerange differentdifferent colourcolour centrescentres areare presenpresentt iinn andand Prescott,Prescott, 1975;1975; Nassau,Nassau, 1985).1985). variablvariablee concentrations.concentrations. DueDue toto theirtheir strongstrong polarizationpolarization TheThe absorptionabsorption spectraspectra ofof naturalnatural andand artificiallyartificially dependencydependency thethe colourcolour centrescentres areare designated designated asas X-and X- and Y­ Y- irradiatedirradiated blubluee topaztopaz crystalscrystals inin thethe visiblevisible areaarea werewere centres,centres, thethe colourcolour ofof whichwhich iiss blueblue andand bluish-violetbluish-violet studiedstudied byby differentdifferent authorsauthors (Nassau(Nassau andand Prescott,Prescott, respectively. respectively. 1975;1975; Petrov,Petrov, 1977).1977). AccordingAccording toto thesethese papers,papers, thethe TheThe electronelectron irradiatedirradiated samplessamples revealreveal crackscracks anandd partingparting planeplaness parallelparallel toto thethe basabasall pinacoidpinacoid c (001).(001). IInn colorationcoloration ofof allall differentdifferent typestypes ofof naturanaturall andand addition, a shell-like structure is observed consisting of a artificiallyartificially inducedinduced blueblue topaztopaz isis causedcaused byby a broadbroad addition, a shell-like structure is observed consisting of a -1l blubluee rim,rim, a colourlesscolourless intermediateintermediate zone,zone, whichwhich iiss absorptionabsorption bandband aatt aboutabout 1515 200200 - 1616 100100 cm-cm ,:= characterizedcharacterized byby a highhigh concentrationconcentration ofof irradiation­irradiation- 658658 - 620620 nmnm (cf.(cf. alsoalso Nassau,Nassau, 1984,1984, 1985).1985). induceinducedd defects,defects, andand a colourlesscolourless core.core. ThisThis shell-likeshell-like ByBy thethe useuse ofof low-energylow-energy gammagamma radiation,radiation, e.g.e.g. structurestructure isis explainedexplained byby a temperaturetemperature gradientgradient fromfrom thethe withwith thethe gammagamma radiationradiation ofof C0-60Co-60 havinghaving energiesenergies surfacesurface ttoo thethe centrecentre ofof ththee topatopazz crystalscrystals.. ThiThiss temperaturtemperaturee ofof 1.331.33 andand 1.171.17 MeV,MeV, neitherneither radioactivityradioactivity nornor gradientgradient isis formedformed duringduring thethe irradiationirradiation processprocess ofof thethe radiationradiation defectsdefects areare induced.induced. TheThe disadvantagedisadvantage ofof samplessamples whichwhich areare cooledcooled all-aroundall-around withwith runningrunning water.water. Colour,Colour, spectroscopicspectroscopic propertiesproperties andand colourcolour causescauses ooff neutronneutron irradiationirradiation inin nuclearnuclear reactorsreactors isis thethe naturalnatural blueblue topaztopaz areare comparedcompared witwithh featuresfeatures ofof topatopazz generationgeneration ofof radioactiveradioactive nuclidesnuclides bbyy neutronneutron crystalscrystals whichwhich werewere artificiallyartificially irradiatedirradiated withwith gammgammaa activation,activation, partlpartlyy withwith longlong half-lifeshalf-lifes (in(in topaztopaz rays,rays, electronselectrons andand neutronsneutrons.. mainlymainly Sc-46Sc-46 andand Ta-182Ta-182 areare producedproduced,, subordinatesubordinate amountsamounts ofof C0-60Co-60 andand Cs-134Cs-134 areare alsoalso observedobserved afterafter irradiation).irradiation). TheseThese radioactiveradioactive nuclidesnuclides causecause anan irradiation-induceirradiation-inducedd radioactivity,radioactivity, whichwhich isis notnot IntroductionIntroduction acceptableacceptable toto thethe tradetrade.. Therefore,Therefore, accordingaccording toto thethe ColourlesColourlesss topaztopaz hashas beenbeen irradiation-treatedirradiation-treated individualindividual conditionsconditions ofof treatmenttreatment asas wellwell asas toto thethe commerciallycommercially forfor aboutabout tenten yearsyears inin differentdifferent tracetrace elementelement contentscontents ofof anan individualindividual crystal,crystal, a proceduresprocedures inin orderorder toto produceproduce a moremore oror lessless coolingcooling offoff periodperiod betweenbetween oneone andand fourfour yearsyears isis intenseintense blueblue coloration.coloration. UnderUnder exposureexposure toto gammagamma necessarynecessary forfor thethe decaydecay ofof radioactivity.radioactivity. AfterAfter thisthis rays,rays, e.g.e.g. onon irradiationirradiation toto gammagamma raysrays producedproduced byby time,time, thethe inducedinduced radioactivityradioactivity hashas almostalmost com­com­ Co-60Co-60 withinwithin a gammagamma cell,cell, inin generalgeneral onlyonly a blueblue pletelypletely disappeared,disappeared, thethe remainingremaining activityactivity beingbeing inin colorationcoloration oflowof low intensityintensity isis acquired.acquired. TheThe treatmenttreatment thethe rangerange ofof thethe naturalnatural background.background. ByBy treatmenttreatment ofof topaztopaz withwith high-energyhigh-energy electronselectrons byby thethe useuse ooff withwith electronselectrons ofof energiesenergies betweenbetween 1010 andand 2020 mega­mega- linearlinear acceleratorsaccelerators oror withwith neutronsneutrons inin nuclearnuclear electronvolts,electron volts, whicwhichh araree commonlcommonlyy useusedd foforr thethe reactorsreactors causescauses a moremore intenseintense blubluee colour.colour. ByBy thethe irradiationirradiation ofof topaz,topaz, certaincertain typestypes ofof radiationradiation useuse ofof gammagamma raysrays oror electrons,electrons, thethe irradiation­irradiation- defectsdefects areare occasionallyoccasionally produced.produced. ThisThis irradiation­irradiation- treatetreatedd topaztopaz turnsturns a moremore intensintensee brownbrown oror inducedinduced crackingcracking andand damagedamage maymay diminishdiminish thethe greenish-browngreenish-brown colour.colour. TheThe desireddesired blueblue colorationcoloration qualityquality ofof thethe treatedtreated crystalcrystal oror makemake thethe topaztopaz isis produceproducedd byby subsequentsubsequent heatingheating atat aboutabout 200°C200°C completelycompletely uselessuseless forfor jewellerjewelleryy purposes.purposes. forfor a fewfew hourshours inin orderorder toto bleachbleach ththee brownbrown TheThe aimaim ofof thethe presentpresent paperpaper isis a detaileddetailed unstableunstable colourcolour centrescentres inin topaz.topaz. , descriptiondescription ofof thethe colorationcoloration andand differentdifferent typestypes ofof Neutron-irradiatedNeutron-irradiated stonesstones inin generalgeneral revealreveal anan electron-inducedelectron-induced defectsdefects inin irradiatedirradiated topaz.topaz. InIn intenseintense blueblue colorationcoloration withoutwithout heatheat treatment.treatment. addition,addition, thethe studystudy presentspresents thethe first descriptiondescription ofof However,However, heatingheating ofof neutron·irradiatedneutron^irradiated stonesstones isis differentdifferent typestypes ofof blueblue colourcolour centrescentres inin topaz,topaz, appliedapplied toto removeremove anan inkyinky oror steelysteely hue,hue, i.e.i.e. inin orderorder whichwhich werewere discovereddiscovered duringduring thisthis researchresearch project.project.

© CopyrightCopyright thethe GemmologicalGemmological AssociationAssociation ISSN:ISSN: 0022-12520022-1252 J. Gemm., 1987, 20, 6 363

Fig. 1. Topaz from Nigeria irradiated with high-energy electrons; Fig. 2. Topaz from Nigeria irradiated with high-energy electrons the sample reveals parting parallel to the basal pinacoid (identical stone to that in Figure 1); all-around shell-like (above): in addition, parallel cracks are developed. At a structure consisting of a light blue rim (about 3 mm distance of about 3 mm from the surface, an intermediate broad), a colourless intermediate zone, which is characterized zone with a high defect concentration is formed. View by a high concentration of defects, and a colourless core; perpendicular to the c-axis. 12x. growth planes parallel to the prism faces m (110) and / (120) are developed. View parallel to the c-axis. 14x.

Experimental details very uniform and measures about 3 mm. This For the present study, two parcels of hardly uniform and all-round light blue coloration in the damaged topaz crystals were available. According rim of the samples is superimposed by an irregular to the information given by the supplier, both and spot-like bluish-violet colour, which is generally parcels of stones were recently treated by different developed only in one side or in one area of the rim linear accelerators in the USA. All samples were (Figures 3, 4). The irregular and patch-like distri­ pre-shaped topazes, which had been mined in bution of the bluish-violet coloration is comparable various (?) localities in Nigeria. For comparisons with the irregular zoning of the brown colour of sake, different parcels of topaz from various Nigerian topaz samples, which were irradiated in localities which were treated by the author by the the gamma cell with Co—60 or in a linear accelerator use of gamma rays and high-energy electrons and with high-energy electrons before the stones are converted to blue after subsequent heating, neutron- heat treated. In both types of samples, i.e. in heat irradiated samples from different occurrences as treated and non-heat treated irradiated stones, the well as naturally blue coloured topaz from Brazil, irregular and patchy bluish-violet or brown coloration Nigeria and Zimbabwe, were spectroscopically of topaz in most cases does not follow crystal faces investigated. and varies even among crystallographical zones. In some samples growth planes parallel to the prism Results faces m (110) and / (120) were observable in The topaz crystals from Nigeria irradiated with immersion liquids. However, only in a few cases high-energy electrons exhibit a blue coloration of was the colour zoning found to follow this clearly variable intensity. By examination with the naked developed growth zoning (Figures 2, 4). The eye, most of the stones reveal plane parallel cracks, pleochroism of the intensely coloured zones or and part of the samples were broken parallel to one patches is different from the pleochroism of the or even two of these planes (Figure 1). The light blue uniformly coloured zones (Table 1). The orientation of these parting planes is parallel to the pleochroism of these light blue zones is identical known cleavage of topaz, i.e. parallel to the basal with the normal pleochroism of natural blue topaz pinacoid c (001). as well as identical with that of topaz which was All topaz crystals of both parcels exhibit a shell­ irradiated in a gamma cell and heated subsequently like zoning, which was found to be independent (Table 1, cf. also Petrov, 1977). In topaz from from the crystallographical orientation of the different localities which was irradiated in nuclear individual sample (Figures 2, 3). This shell-like reactors with neutrons, the pleochroic colours are structure was observable in all samples however, somewhat different (Table 1). Colour zoning was the best investigations were possible in cracked never observed in samples which had been treated samples with one or two parting planes parallel to in this manner. c (001). The rim of the stones reveals a uniform blue The absorption spectra of natural (untreated) coloration beginning directly at the surface of the blue topaz as well as the spectra of topaz irradiated pre-shaped stones. The depth of this zone is also by neutrons, electrons or gamma rays, reveal ~ 00 f N a- W 0\ +>- v"" ':-' 364 J. Gemm., 1987, 20,? 6

* >< 420 420

nuclear A ~ ~ N in o o 3 o o A x bluish-black**** 00 observed 23800 o (N (NI23800

to X (NI

3 ^

grey O * VO irradiated ~ zoning ~ I 8 J0a §g A bluish topaz O «O vë colour 15200 658-625**** A S o M reactor. 15200-16000 blue reactors no very light colourless, > o a X X~Z~Y X~Z~Y the in * ill * rs * rays * 0 1 602 irregularly

yellowish v-ï vO zone

blue** N 625** 3« gamma *->

0 vo16600 O ^ and evel o arke r NO M linear :3 fi O 16000 darker colourless, developed distinctly -O T3 intense X=Y~Z X thickness. in

-a in G 3 em

SoH neutrons

TO 2 i> * * heat-treated

_i< to

g to yellowish grey irradiated "cdall-around Ä bo >> o zone

X blue** „ „

A ~ 43 "ö3 \M O O o be zones. 16000 blue x developed light distinctly colourless, colourless, subsequently

'-=3 T3 X samples localities. exposure for both in cell, various different heat­ 3 h ü * * grey yellowish to irradiated Ä bß >> zoning

-o blue „ „ 625

topaz •^ OS 03 from Q (/) C/2 confirmable identical

OJ O 3 -a ~ gamma N (Z,Y)

topaz y "E 'S rv e not blue S 3 3 are

A ~ colour

the g u <0u3 stones

in JD ^00 according x o 16000 X treated blue no in colourless, colourless, observed distinctly subsequently o

Ö O was bands * * maxima variable different 420 in maximum

~ N (Z,Y) topaz, absorption rarely

A ~

* xi ' the X x maximum 23800 blue variable absorption Zimbabwe of zoning absorption * * ~

and •3 J-I u an yellowish o .3 bûgrey >> "o w -o blue « « O ' of colour

untreated <-> 3 P*> 03 C/5 s© vç Nigeria, o ! absorption N maximum (Z,Y) S-i s 3 3 intensities

a 658-625***

A ~ and Ö O O él or ist i bs e • -3 O O 15200--16000 x colourless, distinctly colourless, natural Brazil, distinct T3 observable X

o presence Pleochroism T3 U U ö o 1. 8 •0 < the colour absorption colour

u bUT U o •S ft I nm] * cm~1 **

lo u 05 g _, -T3 _«_.o__o_ , *** **** [in Yllb maxIma Xlla ratios Zllc absorption intensity o o and Yllb Zllc pleochro­ Xlla zoning ism colour Table "ft.ïï X >H N 'S S â § X^N" I J. Gemm., 1987, 20, 6 365

different absorption bands with maxima in the area developed only in one side or region of a pre-shaped between 15 000 and 17 000 cm"1 (« 667 - 590 nm), sample, a distinct absorption band in the the intensities of all absorption bands being Y-spectrum is observed. This band of high intensity distinctly dependent on the polarization of the is not observable in natural or gamma-irradiated electric vector E (parallel to the three indicatrix axes stones, and is found in neutron-irradiated samples X, Y, and Z). These spectroscopic investigations only with low intensity. The intensity of the confirm that the absorption scheme of natural blue absorption band in the X-spectra of electron- topaz is almost identical with that of topaz treated irradiated topaz is identical in different areas of with gamma rays as well as with the absorption these crystals, i.e. in light blue and intense bluish- scheme of the uniformly coloured and all-round violet regions. These results of spectroscopic light blue area of electron-irradiated topaz. In measurements confirm the visible observations, neutron-irradiated stones, this absorption scheme which show a homogeneous colour distribution and is strongly intensified. In these dark blue samples, intensity in electron-irradiated topaz for polarized absorption bands in the Y- and Z-spectra are light with an electric vector E parallel to X. Strong observed, which cannot be measured with certainty colour zoning, however, is observable for polarized in the light blue coloured samples mentioned light with an electric vector E parallel to Y. above. Furthermore, additional absorption maxima Inwards from the blue rim of the topaz crystals, in the violet area of the visible region are observed in which were recently irradiated by linear accelerators neutron-irradiated topaz (Table 1). These maxima in the USA, a colourless zone of about 1 mm in were also present in the spectra of the darkest blue depth is observed. This colourless zone is characterized samples of natural blue topaz crystals from different by a high concentration of structural defects localities, which were available for the present (Figures 1-5). Following this second intermediate study. shell (fissure zone) a colourless core is observed, In the irregular and spot-like bluish-violet areas which is almost free of structural defects (Figure of electron-irradiated topaz, which are, in general, 2). Independently from the three concentrically

Fig. 3. Topaz crystals from Nigeria irradiated with high-energy electrons; the samples reveal parting planes parallel to the basal pinacoid (001). An all-around shell-like structure consists of a light blue rim, a colourless intermediate zone, which is characterized by a high concentration of defects, and a colourless core. The uniform light blue colour of the rim is superimposed by an irregular and spot-like bluish-violet coloration. Size of the left sample approx. 17.5 x 13 mm. (Photo by O. Medenbach, Bochum.) 366 J. Gemm., 1987, 20, 6

Fig. 4. Topaz from Nigeria irradiated with high-energy electrons; Fig 5. Topaz from Nigeria irradiated with high-energy electrons; irregular bluish-violet coloration developed at one side of intermediate zone with high concentration of needle-like the rim of the sample, intermediate zone with high defect defect structures, the orientation of the needle axes is concentration; growth planes are parallel to the prism parallel to the a-axis of the crystal. View parallel to the faces m (110). View parallel to the c-axis: polarized light c-axis. 30x. with E parallel to Y. 20x.

Fig. 6. Topaz from Nigeria irradiated with high-energy electrons; intersecting needle-like defect structures orientated with the needle axes parallel to the a- and c-axes of the crystal; isolated patches of cracks parallel to the basal pinacoid c (001). 55x.

Fig. 7. Topaz from Nigeria irradiated with high-energy electrons; Fig. 8. Topaz from Nigeria irradiated with high-energy electrons; isolated patches of cracks parallel to the basal pinacoid intersecting needle-like defect structures orientated with c (001). 80x. the needle axes parallel to the a- and c-axes of the crystal. 65x. J. Gemrn., 1987, 20, 6 367

arranged shells or zones, the samples often revealed The concentrations of the X-centres in neutron- sets of parting planes parallel to the cleavage of irradiated samples strongly exceed the con­ topaz (Figure 1), which is parallel to the basal centrations of the X-centres in all other types of pinacoid c (001). In some areas, these cracks are not blue topaz. Only in the dark bluish-violet patchy developed in the form of continuous planes, but in areas of electron-irradiated topaz, is the intensity of the form of isolated patches (Figures 6,7), i.e. they the absorption band of the Y-centre with a enclose only parts of a continuous plane parallel to polarization of Y > (X, Z) comparable with the the basal pinacoid c (001). intensity of the absorption band of the X-centres The fine structure of the second intermediate (Figure 9). The presence of both X- and Y-colour shell of electron-irradiated topaz, which is charac­ centres in this type of irradiated topaz, however, is terized by a high defect concentration, is formed by absolutely necessary to bring the intensity of the two systems of linear fissures, which are arranged blue coloration to a commercially usable level. In parallel to two crystallographic directions in topaz. neutron-irradiated topaz, the presence of small The orientations of the needle-like defect structures concentrations of the bluish-violet Y-centre was were determined to be parallel to the crystallographic confirmed by spectroscopic investigations a- and c-axes of the samples (Figures 3, 6, 8). In (cf. Table 1, Figure 9). some areas, the two dominant systems of needle­ Due to the similar position of their absorption like defect structures intersecting at right angles maxima, the distinction of X- and Y-centres in (Figures 6, 8) are connected by a third subordinate irradiated blue topaz has to be conducted with system of irregular fissures. polarized absorption spectroscopy. In the paper of Nassau and Prescott (1975), an absorption maxi­ Discussion mum at 620 nm in stones irradiated with Co-60 was In some recently published papers dealing measured; no information about the polarized comprehensively with colour and colour causes of spectra of these samples was published. Presumably, natural (untreated) and irradiated brown and blue these stones mainly contained small concentrations topaz (Nassau, 1984, 1985), only one blue colour of X-centres. The only polarized spectra of natural centre is mentioned for all types of blue topaz. The blue coloured topaz crystals were published by experimental results described in this paper as well Petrov (1977). This paper contains adequate data as further investigations (Schmetzer, 1987), how­ on the X-centres. A connection between the ever, confirm the development of several different concentration of part of the X-centres in dark blue, blue colour centres, or more precisely, the develop­ naturally coloured as well as in neutron irradiated ment of at least two blue X-centres and one topaz and the intensity of the new absorption band bluish-violet Y-centre in topaz. The relative con­ in the bluish-violet area is conceivable (Table 1). centration of these colour centres is mainly This connection, however, needs further experi­ dependent on the type of irradiation used for the mental confirmation. coloration of the stone (cf. Figure 9). The blue Presumably, the irregularly distributed and X-centres with a polarization of X > (Z, Y) are patchy bluish-violet coloration in electron-irradiated predominant in natural blue topaz, in gamma-and and subsequently heat-treated topaz from Nigeria, neutron-irradiated topaz, and in the uniform all- i.e. the irregular concentration of Y-centres after round light blue area of electron-irradiated topaz. treatment, is caused by an irregular distribution of

colourless colourless gamma cell colourless brown heat treatment ~ 200°C blue X-centres 1

linear accelerator brown or heat treatment ~ 200°C ,. X- and colourless blue greenish-brown Y-centrev s

nuclear reactor colourless blue X-centres

Fig. 9. The development of blue and bluish-violet X- and Y-centres in topaz by irradiation processes and subsequent heat treatment. 368 J. Gemm., 1987, 20, 6

one or several trace elements in different areas of cause the generation of heat. Therefore, the topaz those crystals. Unfortunately, the colour causes of crystals have to be cooled continuously with the X-centres and the newly described Y-centre in running water during the irradiation process. These topaz as well as the different mechanisms of facts can help to explain the all-around shell-like stabilization of colour centres, i.e. the reaction structure of the crystals with radiation induced mechanisms by irradiation and heat treatment defect structures. Due to the contact of the surface (Figure 9), are almost unknown. A first attempt to of the irradiated topaz crystals with running water clarify some of these problems was made by Petrov an all-around temperature gradient from the rim to (1983). Thus, the most probable connection between the core of the topaz is generated. Presumably, the irregular colour distribution and one or several shell-like zones having different temperatures and trace elements has still to be confirmed analytically. thus zones with different thermal expansion are Most probably, the irregular distribution of the formed. The anisotropic heat conduction of ortho- brown coloration in gamma- or electron-irradiated, rhombic topaz as well as the anisotropic thermal non-heat treated samples from Nigeria is also due to expansion, which is also zoned from the surface variable trace element concentrations in those to the centre, probably causes stress in the topaz crystals, and a connection with the irregular structure. As a result, the characteristic systems of concentration of bluish-violet Y-centres after heat defect structures described above are formed. treatment of electron-irradiated samples is also The absence of blue or bluish-violet colour conceivable. centres in the intermediate zone and in the core of Due to the more regular distribution of X-centres the topaz crystals is also explainable by increased in gamma- and electron-irradiated and subsequently temperatures in these areas. In general, the blue heat treated as well as in neutron irradiated non- coloration of natural untreated as well as that of heat treated topaz (Figure 9), the concentration of irradiated topaz is removed at temperatures between X-centres is less dependent on various trace element 200 and 500°C. The exact temperature is dependent concentrations in the individual topaz crystal. Most on the unknown conditions of colour causes and probably, the precursor elements or precursor stabilization mechanisms in an individual sample. centres for the generation of blue X-centres in topaz Therefore, the temperatures in the intermediate are found in uniform distributions within the fissure zone and in the core of the crystals are crystals or are not present at all (referring to topaz assumed to exceed 200°C during the irradiation crystals which are uniformly coloured in X polari­ process. Obviously, the all-around cooling by zation by irradiation with gamma rays or high- running water was inadequate to protect the whole energy electrons and to topaz crystals which are samples. Under the experimental conditions of the colourless in X polarization after irradiation and irradiation process, which are unknown in detail, heat treatment; (Figure 9). By neutron irradiation, the cooling was only sufficient in a rim zone of an extremely high concentration and uniform 3 mm in depth for the generation and stabilization distribution of X-centres is developed, and the of the blue and bluish-violet X- and Y-colour concentration exceeds that in gamma ray and centres. electron-irradiated samples (among several thousands of neutron-irradiated topaz crystals, no Acknowledgements sample was observed which remained colourless). Both parcels of electron-irradiated topaz from the In order to explain the radiation induced defects USA were kindly submitted by Dr H. Krupp of in topaz two mechanisms have to be discussed. For Heidelberg, FRG. Financial support was given by the development of a commercially usable blue grants of the Wirtschaftsministerium des Landes coloration in topaz an electron beam with particles Rheinland-Pfalz, FRG. in the 10 to 20 mega-electronvolt range is applied. These high-energy electrons interact in a different References manner with the atoms of the topaz structure. One Nassau, K., 1984. Gemstone enhancement. Butterworths, London. of these interactions is the build-up of electrical Nassau, K., 1985. Altering the colour of topaz. Gems & Gemology, 21, 26-34. charge in topaz, causing the formation of parting Nassau, K., and Prescott, B.E., 1975. Blue and brown topaz planes parallel to the basal pinacoid c (001), which is produced by gamma irradiation. American Mineralogist, 60, the ordinary cleavage plane of this mineral. This 705-9. process is caused by the limited penetration of Petrov, I., 1977. Farbuntersuchungen an Topas. Neues Jahrbach für Mineralogie, Abhandlangen, 130, 288-302. electrons in topaz, which is approximately calculated Petrov, I., 1983. Paramagnetische Zentren in Topas - kristallchemische for electrons with an energy of 15 MeV to Klassifikation natürlicher Topase durch Korrelation ihrer optischen ~ 2.27 cm for the maximum range of penetration Absorptions-, EPR- und TL-Spektren. Dissertation, Heidelberg. and to ~ 0.69 cm for the half-thickness. In addition, Schmetzer, K., 1987. Irradiation-induced blue color in topaz. Die the high-energy electrons, which are slowed down Natur Wissenschaften, (in press). by interaction with the atoms of the topaz structure, [Manuscript received 24 May 1986.] JJ.. Gemm.Gemm.,, 19871987,20,6, 20, 6 363699

SapphirinSapphirinee (no(nott sapphiresapphire)) iinn a rubrubyy frofromm BBoo RaiRai,, ThailandThailand

John I.I. Koivula and C.W.C. W. FryerFryer

ResearcResearchh DepartmentDepartment,, GemologicaGemologicall InstitutInstitutee ooff AmericaAmerica,, SantSantaa MonicaMonica,, CaliforniaCalifornia,, USAUSA..

AbstracAbstractt AAss showshownn iinn FigurFiguree 11,, ththee inclusioninclusionss werweree ThiThiss notnotee describedescribess inclusioninclusionss ooff ththee magnesiumagnesiumm anhedral roundedrounded grains. grains. This This suggested suggested a protogenetic a proto­ aluminiualuminiumm silicatesilicate,, sapphirine,sapphirine, discovereddiscovered inin a ThaiThai ruby.ruby. genetic origioriginn iinn relatiorelationn ttoo theitheirr hosthost.. AAnn 80-watt80-watt ThThee inclusioninclusionss werewere identifiedidentified byby X-ray X-ray powder powder diffraction. diffraction . pinpoinpinpointt fibre-optic illuminatoilluminatorr wawass needeneededd ttoo gegett ThiThiss iiss thethe firstfirst reportreport ofof sapphirinesapphirine asas anan inclusioninclusion inin anyany enougenoughh lighlightt througthroughh ththee exposeexposedd inclusioinclusionn (Figure(Figure gegemm materialmaterial.. 22)) ttoo examinexaminee foforr pleochroismpleochroism.. ThThee inclusioninclusion A smalsmalll brokebrokenn rougroughh rubrubyy crystacrystall containincontainingg threthreee proveprovedd ttoo bbee birefringenbirefringentt anandd ththee greegreenn anandd deepdeep dardarkk greenish-blugreenish-bluee crystalline-appearincrystalline-appearingg inclusioninclusionss wawass givegivenn ttoo ththee authorauthorss foforr examination.. ThThee hoshostt rubrubyy wawass a blubluee pleochroipleochroicc colourcolourss thathatt werweree observeobservedd suggestedsuggested purplish-repurplish-redd tabulatabularr etcheetchedd crystacrystall thathatt weigheweighedd 0.910.91 that thethe inclusions inclusions might might be besapphire. sapphire. carats. IItt wawass collectecollectedd bbyy DDrr PetePeterr C.. KelleKellerr whilwhilee ThThee inclusioinclusionn wawass thethenn scrapescrapedd usinusingg a fine-pointfine-point studyinstudyingg ththee BBoo RaRaii rubrubyy mineminess iinn ththee TraTratt ProvincProvincee ooff diamond-tippediamond-tippedd scraperscraper untiuntill a minutminutee amountamount ooff ThailanThailandd (Keller(Keller,, 1982)1982)..

Fig. I.1. DarkDark greenish-bluegreenish-blue sapphirinesapphirine incluinclusiosionn exposedexposed atat thethe Fig.Fig. 2. A pinpointpinpoint illuminatorilluminator highlightshighlights thethe sapphirinesapphirine inclusioninclusion surfacesurface ofof a brokenbroken ThaiThai ruby.ruby. Dark-fieldDark-field illumination.illumination. forfor opticaloptical examination.examination. lOx.lOx. 30x.

TheThe rubyruby hadhad beenbeen brokenbroken acrossacross itsits centre,centre, exposingexposing powderpowder was obtainedobtained toto makemake a spindlespindle forfor X-rayX-ray thethe largestlargest ofof thethe threethree inclusionsinclusions toto thethe surfacesurface forfor easeasyy powderpowder diffraction.diffraction. X-rayX-ray powderpowder diffractiondiffraction analysisanalysis (Figure(Figure 1).. SinceSince TheThe spindlespindle waswas mountedmounted andand centredcentred inin a inclusionsinclusions ofof thisthis appearanceappearance hadhad nevernever beforebefore beenbeen reportedreported inin ruby,ruby, itit waswas decideddecided thatthat identificationidentification wouldwould Debye-ScherrerDebye-Scherrer powderpowder cameracamera andand exposedexposed toto bebe attempted. X-raysX-rays generatedgenerated atat 4646 kVkV andand 2626 rnAmA fromfrom a nickel-filterednickel-filtered coppercopper targettarget tubetube forfor a timetime ofof 4.54.5 TestingTesting hours.hours. AfterAfter gemmologicalgemmological verificationverification thatthat thethe hosthost TheThe resultingresulting patternpattern waswas comparedcompared withwith ourour crystalcrystal was ruby,ruby, thethe inclusionsinclusions themselvesthemselves werewere sapphiresapphire (corundum)(corundum) standardstandard pattern.pattern. ItIt waswas examinedexamined opticallyoptically toto seesee whatwhat couldcould bebe learnedlearned immediatelyimmediately obviousobvious thatthat thethe inclusioninclusion waswas notnot beforebefore X-rayX-ray analysisanalysis waswas performed.performed. sapphire.sapphire. TheThe unknown'sunknown's patternpattern waswas thenthen measuredmeasured

© CopyrightCopyright thethe GemmologicalGemmological AssociationAssociation ISSN:ISSN: 0022-12520022-1252 370370 J.J. Gemm.Gemm.,, 1987,20,61987, 20, 6

forfor d spacingspacing usinusingg a NieNiess overlayoverlay scalescale correctecorrectedd forfor logical,logical, iiff givengiven thethe choice,choice, toto pickpick ththee muchmuch filmfilm shrinkage,shrinkage, whilewhile thethe lineline intensitieintensitiess werewere commonercommoner sapphiresapphire overover thethe rarerrarer ooff ththee two,two, visuallvisuallyy estimated.estimated. sapphirine.sapphirine. UUsin singg ourour MineraMinerall PowderPowder DiffractioDiffractionn FileFile SearchSearch ManualManual (JCPDS(JCPDS,, 1980),1980), wewe founfoundd aann exactexact patterpatternn matchmatch witwithh ththee monoclinimonoclinicc mineraminerall sapphirinesapphirine AcknowledgementsAcknowledgements (ASTM(ASTM FilFilee NumbeNumberr 21-549)21-549),, chemicachemicall formulaformula TheThe authorsauthors wouldwould liklikee toto thanthankk PeterPeter CC.. Keller,Keller, (Mg,(Mg, Al)Al)s8 (AI,(Al, Si)6Si)6 O0 2200 (Fleischer,(Fleischer, 1980).1980). Ph.D.Ph.D.,, GGGG,, AssociateAssociate DirectoDirectorr ofof thethe LoLoss AngelesAngeles ThiThiss camcamee asas a completecomplete surprisesurprise becausebecause CountyCounty MuseumMuseum ooff NaturaNaturall History,History, foforr ththee giftgift ooff althougalthoughh sapphirinesapphirine hadhad beebeenn reportereportedd aass a cutcut thethe rubyruby witwithh sapphirinesapphirine inclusions.inclusions. ThankThankss areare stonestone (Fryer(Fryer,, 1985),1985), itit hahadd notnot beenbeen reportedreported aass anan alsalsoo givengiven toto RutRuthh PatchickPatchick foforr typintypingg thisthis inclusioninclusion.. SoSo iinn thisthis respecrespectt iitt iiss a firsfirstt observation.observation. manuscriptmanuscript..

ConclusionConclusion ReferencesReferences BecauseBecause ooff theirtheir colour,colour, pleochroispleochroismm anandd closeclose KellerKeller,, PeterPeter C.C.,, 1982.1982. TheThe Chanth~buri-TratChanthaburi-Trat GemGem FieldField,, proximitproximityy ttoo ruby,ruby, thesethese inclusioninclusionss werweree aatt firstfirst Thailand,Thailand, Gems & Gemology,Gemology , 18,18, 4,4, 186-96.186-96. JCPDSJCPDS:: JoinJointt CommitteCommitteee oonn PowdePowderr DiffractionDiffraction Standards,Standards, 19801980.. thoughtthought ttoo bebe sapphire.sapphire. WherWheree sapphiresapphire vsvs.. Mineral Powder Diffraction Manual. InternationaInternationall CentreCentre forfor sapphirinesapphirine iiss concerned,concerned, thithiss isis a commoncommon mistake.mistake. DiffractionDiffraction Data,Data, Swarthmore,Swarthmore, Pennsylvania.Pennsylvania . SapphirineSapphirine getsgets ititss namename frofromm sapphiresapphire becausebecause Fleischer, Michael, Michael, 1980. 1980. Glossary Glossary onon MMineral ineral Species.Species. Mineralogi­Mineralogical smallsmall graingrainss ooff ththee twtwoo mineralsminerals looklook veryvery muchmuch Record,cal Record, Tucson, Tucson,Arizona. Arizona. FryerFryer,, C.W.C.W.,, 1985.1985. GeGemm TradTradee LabLab NotesNotes.. Gems & GemologyGemology,, alike.alike. EveEvenn thougthoughh thetheyy areare completelcompletelyy differentdifferent 2121,, 3,3, 171-77.171-77. mineralmineralss chemicallychemically anandd physicallyphysically,, thetheyy areare stillstill easileasilyy confused.confused. So,So, onon thethe basibasiss ofof lookslooks,, itit isis [[ManuscriptManuscript receivedreceived 2 October 1986.]1956.]

ARAREE YOYOUU ADEQUATELADEQUATELYY EQUIPPEDEQUIPPED?? NowNow isis ththee timtimee ttoo extendextend youyourr collectioncollection ofof gemgem testintestingg instruments.instruments. ThThee GemmologicalGemmological AssociatioAssociationn isis ablablee toto offeroffer membersmembers thethe opportunityopportunity ofof acquiringacquiring aatt speciallyspecially reducedreduced pricesprices a rangerange ofof gemmologicalgemmological equipmentequipment whichwhich hashas beenbeen specificallspecificallyy selectedselected frofromm ourour currencurrentt cataloguecatalogue andand manufacturedmanufactured byby ththee RaynerRayner OpticalOptical Company.Company. StockStockss araree limitedlimited soso membermemberss wishingwishing ttoo purchasepurchase araree urgedurged ttoo placeplace theirtheir orderorderss quickly.quickly. Cat.Cat. No.No. ListList PricePrice SpecialSpecial OffeOfferr TotalTotal coscostt inc.inc. VAVATT & postagepostage (UK(UK onlyonly)) 11591159 Multi-slitMulti-slit prismprism spectroscopespectroscope £113.9£113.955 £ 89.5089.50 £105.22£105.22 10701070 SmallSmall VersaliteVersalite stereostereo microscopemicroscope 3030xx mag.mag. £156.50£156.50 £125.0£125.000 £147.20£147.20 11641164 HardnessHardness pencilpencil setset (7(7 mineralsminerals rangingranging frofromm 4-10onMohs'scal4-10 on Mohs' scalee individuallyindividually mounted).mounted). £ 28.328.355 £ 23.5023.50 £ 28.128.188 11291129 GemmologyGemmologySGuni SG unitt £163.2£163.200 £115.00£115.00 £138.00£138.00 11411141 SGtestingsetSG testing set £152.65£152.65 £109.5 £109.500 £133.9£133.988 GemmologicalGemmological PublicationsPublications Internal worldworld of ofgemstones gemstones bybyDrE.Gübeli Dr E. Gubelinn £ 80.0080.00 £ 65.0065.00 £ 68.0068.00 TToo placeplace youyourr orderorder telephontelephonee NarinNarin VakurVakur oonn 01-7201-72643746 4374 withwith youryour credicreditt cardcard details,details, oorr sensendd youryour paymentpayment ttoo ththee AssociationAssociation.. OverseasOverseas customerscustomers maymay paypay byby credit/chargcredit/chargee cardcard oror alternativelalternativelyy a propro formaforma invoiceinvoice wilwilll bebe sent.sent. GemmologicalGemmological AssociatioAssociationn ooff GreatGreat Britain,Britain, SaintSaint Dunstan'sDunstan's HouseHouse,, CareyCarey Lane,Lane, LondonLondon EC2VEC2V 8AB·8AB TelephoneTelephone:: 01-726437401-726 4374 Cables:Cables: Geminst,Geminst, LondonLondon EC2EC2 J. Gemm., 1987, 20, 6 371

Diaspore, a rare faceted gem

J.M. Duroc-Danner, FGA, GG

Geneva, Switzerland

Abstract elongated canal-like inclusions running in parallel In recent years, a number of gemmological laboratories bands, and the faceted stone cut from this rough have reported the appearance of gem quality diaspore*. crystal attained a weight of only 7.632 g (38.16 et). The writer has had the opportunity to examine some According to the lapidary who cut the six stones rough crystals, and six faceted stones cut from them, the from six different crystals, no particular difficulties measurements, weights and properties of which are described below. were noticed in relation to the perfect (010) cleavage, or for fashioning and polishing the Appearance different gems which take a very good polish with a The rough diaspores examined by the writer were vitreous lustre. found in two different forms: A remarkable characteristic of these faceted 1) Long, flattened, prismatic crystals, occasionally diaspores is their colour change (Figure 4), com­ twinned (Figure 1), characterized by deep parable with that observed in alexandrite. Their vertical striations on (001) (similar to those seen colour is brownish-green in daylight, Colormaster in spodumene), most often showing fractured notations BD-11/100/45 for the majority, but one terminations, or more rarely terminated at one stone of a deeper green colour gave ED-15/100/21. end by faces (110) and (111), and at the other end In tungsten light, the majority showed a moderate a flat or fractured base (Figure 2). change of colour which could best be described as 2) Tabular crystals with mica-like cleavage, con­ pinkish-brown, with Colormaster notations BD- sisting of a number of thin plates superimposed 22/100/34. The deeper green stone showed a very on each other. Although the cleavage (010) is distinct colour change to pinkish-red, Colormaster perfect, it is much less facile than that of micas notations ED-33/100/21. which it resembles. The large emerald-cut diaspore was cut from a similar tabular crystal to the one described above, Hardness which measured approximately 77.40 x 75.50 x The hardness on Moris' scale, taken on rough 43.30 mm, for a total depth of 26.80 mm, and a crystals with hardness points and plates, revealed weight of 210 g (Figure 3). that face (010) is not scratched by 6V2, but slightly As can be seen from Figure 3, the stone was scratched by 7. Against polished plates, the same rather heavily flawed by a number of oriented face was found to scratch easily GGG (gadolinium Shape, measurements and weight

Stone No. Shape Approximate Measurements Weight

1 Emerald-cut 23.76 x 16.01 x 11.13 mm 38.16 ct 2 Oval cabochon 14.65 x 10.34 x 8.22 mm 12.55 ct 3 Rectangular step-cut 12.86 x 11.23 x 7.43 mm 8.89 ct 4 Emerald-cut 11.62 x 7.68 x 5.34 mm 4.32 ct 5 Brilliant-cut 7.06 x 5.75 mm 1.87 ct 6 Round cabochon 5.92 x 4.11 mm 1.18 ct

* Diaspore is hydrogen aluminium oxide, HA102, which crystallizes in the orthorhombic system.

© Copyright the Gemmological Association ISSN: 0022-1252 372 J. Gemm., 1987, 20, 6

Fig. 1. Diaspore crystal showing twinning. Approximate measure­ Fig. 2. Gem-quality, flattened, prismatic crystal of diaspore ments of crystal: height 68.40 mm, width 32.20 x deeply striated parallel to its length, with one end 27.00 mm, weight 92.34 g. terminated by a flattened pyramid and the other end by a fractured base. Approximate measurements of the crystal: 64.92 x 34.48 x 17.06 mm, weight 64.14 g.

Fig. 3 (a) The rough crystal of diaspore weighing 210 g from Fig. 3(b). Sketch of the rough crystal, showing its measurements which the 38.16 ct emerald-cut stone was faceted. and cleavage direction. J. Gemm., 1987, 20, 6 373

m

Figs. 4 (a) and (b). The six cut diaspores studied, as they appeared under (a) fluorescent light, and (b) tungsten light 374 J. Gemm., 1987, 20, 6 gallium garnet), but could hardly scratch quartz. At Pleochroism 90° to this plane, the same hardness was found, The pleochroism of the stones, observed through giving a hardness of 6Vz-7 for this mineral. the pavilion with a Rayner calcite dichroscope, was distinct; medium pinkish-brown, light greenish- brown and light brown. Chemical testing Under the action of hydrochloric and sulphuric Absorption spectra acids, the surfaces of the stones were not etched, The absorption spectra seen through a Gem Beck and their colour was unaltered. Spectroscope Unit, showed lines in the blue portion of the visible spectrum, not dissimilar to those seen in Australian sapphires. Density The densities were obtained by hydrostatic weighing of the stones in distilled water using a Mettler PL 300c balance (accuracy ± 0.001 carat), Stone No. Absorption spectra and gave the following results corrected to 4°C for the six different stones: 1 Very strong band, 438-465 nm 2 Strong broad lines, 445,450,458,465 nm Stone Nos. Density 3 Strong broad band, 440-468 nm 4 Strong broad band, 440-465 nm 1,5 and 6 3.382 g/cm3 5 Strong broad band, 445-468 nm 2 3.402 g/cm3 6 Strong broad band, 445-460 nm 3 3.404 g/cm3 4 3.415 g/cm3 Ultraviolet fluorescence The stones, examined with a Multispec combined Refractive Indices LW/SW unit, revealed only a moderate green glow The refractive index determinations were carried under the radiation of 253 nm. out using a Rayner Dialdex refractometer and monochromatic sodium light. Only the table facets Colour filter were tested and it was only possible to get a value for The stones remained green when viewed through the intermediate ß index on stone No. 4. In this case a Chelsea colour filter. the upper and lower shadow edges obtained on the refractometer reached the same 1.723 value as the Microscopic examination stone was rotated indicating that this was the value The inclusions were examined under a Bausch & for ß. In the other cases the upper and lower shadow Lomb Mark V Gemolite binocular microscope edges did not reach a common value. using dark field illumination or overhead lighting, The author has observed that many faceted depending on whether internal or external features biaxial stones have their table facets cut parallel to were to be examined. critical directions, such as the table cut parallel to an Five types of inclusions have been observed in optic axis or to optic axial planes or cut parallel to an the six diaspores examined: acute or obtuse bisectrix. These orientations do not 1) Disc-shaped fingerprint-like inclusions consisting facilitate the determination of the ß value using the of a multitude of very small, oriented, squarish, table facet alone. two-phase inclusions. In many cases it is not possible to obtain readings 2) Isolated small, squarish, two-phase inclusions, from other facets, e.g. when the stone is set or reminiscent of those seen by the writer in where the style of faceting does not allow the stone emeralds from Mozambique. to sit properly on the refractometer. For such stones 3) Long oriented canals filled with two-phase cut according to critical directions, it is always a inclusions (Figure 5). good idea to obtain an interference figure whilst the 4) A mobile bubble was seen in a negative crystal. stone is being observed under the polariscope with At room temperature the bubble, which was the aid of a conoscope. spherical, rested in one corner of the negative The indices obtained from the six stones are: a = crystal (Figure 6). After a few seconds, the heat 1.702, ß = 1.723,7 = 1.750, giving a birefringence from the 30W, 115-125V light bulb used for of 0.048, with optic sign (+). Stone 6, the round examination of the stone, made the bubble move double cabochon, gave only one reading: 1.70 (spot slowly from one corner to the other (Figure 7). A reading). few seconds after the light was turned off the J. Gemm., 1987, 20, 6 375

Figs. 5 (a) and (b). Long, two-phase inclusions, one of the most characteristic features, seen under high magnification (125x), (a) in transmitted light, and (b) with dark-field illumination.

Fig. 6. A negative crystal with a gas bubble resting at one end. Fig. 7. After a few seconds, the heat from the 30W light bulb of the microscope makes the bubble shown in Figure 6 move slowly to the other end of the negative crystal. 125x.

bubble returned to its original position. The one carat. If this is the true situation, the stones phenomenon can be reproduced under the same analysed in this article should be considered in view conditions as many times as one wishes. of their size and beauty as exceptional. 5) Internal fractures, cleavages and tension cracks. References Conclusion 1. Scarratt, K., 1980. Faceted diaspore, Journal of Gemmology, As can be seen from this article, gem diaspore XVII, 3, 145-8. 2. Fryer, C.W. (Ed.), 1983 Gem Trade Lab Notes. Diaspore, a would have all the characteristics to qualify as a rare gem material. Gems & Gemology, XIX, 172-3. highly valuable and desirable stone. Unfortunately, 3. Schiffmann, C.A., 1984. Editorial Forum. Diaspore. Gems and only very few crystals of sufficient transparency, Gemology, XX, 113. clarity and colour have so far been reported. Some 4. Koivula, J.I., 1985. Gem News. World's largest diaspore? occasionally show terminations or are twinned, and Gems & Gemology, XXI, 58. these should not be cut; others are so small that they [Manuscript received 26 March 1986. Revised 13 January would probably only produce faceted stones under 1987.] 376 J. Gemm., 1987, 20, 6

Some colour variation in jadeite

C.R. Cavey, FGA

London EC1N 8NX

Jadeite is a material which is often encountered brownish-orange. In the cover illustration two during the normal course of commerce by the trade interesting examples of colour variation are seen. gemmologist. Variations of the same colour in one The brush pot is in the shape of a bamboo stem object are not uncommon, but two distinct colours with a margin of good emerald green colour; the in adjoining zones are not so often seen. This latter bulk of the pot consists of whitish to pale lavender type of variation is most often encountered in jadeite with a little green interspersed. The di­ material where the outer skin of a rough boulder has mensions are 10 X 3 x 2 cm. The pot was probably been subjected to weathering. These colour carved during the early nineteenth century, and the variations are commonly from greens to browns and surface polish was achieved without the use of diamond powder. The carved desk seal shows colours varying from medium green, through a whitish zone to a fine lavender. This item is typical of material carved in China for export to Europe during the latter part of the nineteenth century. The base of the seal is engraved with a European armorial crest. The dimensions are 6 x 1.2 x 1.1 cm. Refractive index measurements were easily made on the flat surface of the lavender coloured base. The third object (see cover picture and Figure 1) is a very unusual type of jadeite of a pale blue/grey/green colour, depending upon the type of illumination in which it is viewed. In daylight it is an icy bluish-grey colour and is much the same colour in tungsten light, but in fluorescent light it appears a pale celadon (pale green) colour. The material is of exceptional translucency and is virtually transparent around the fingers and on the thinner edges. Normal fibrous, granular jadeite structure is visible but only when searched for carefully and then only evident in small areas. The carving is of the Goddess Kuan Yin and is thought to be of modern workmanship. The polish is mirror-like and no 'orange-peel' effect is visible, which would indicate that it has been achieved using diamond powder. Refractive index and birefringence measurements were easily taken from the base, and it shows a remarkably strong absorption band at 437.4 nm. The dimensions are 14.5 x 3 X 2.3 cm. Fig. 1. Upper part of a jadeite figurine (Kuan Yin) showing unusual translucency and mirror-like polish, achieved by the use of diamond. Photograph by E.A. Jobbins. [Manuscript received 5 February 1987.]

© Copyright the Gemmological Association ISSN: 0022-1252 JJ.. Gemm.Gemm.,, 19871987,20,6, 20, 6 373777

OOnn ththee inclusioninclusionss iinn emeraldemeraldss frofromm SantSantaa TerezinhTerezinhaa ddee GoiásGoias,, BraziBrazill

TakéshiTakishi Miyata,Miyala, Ph.D.,Ph.D., F.G.A.*,F.G.A.*, MasahiroMasahiro Hosaka,Hosaka, Ph.D.,Ph.D., F.G.A.*F.G.A.* andand AkiraAkira Chikayama,Chikayama, F.G.A.,F.G.A., C.G.fC.G.†

*Institut*Institutee ooff GemmologGemmologyy anandd JewellerJewelleryy ArtArtss ooff YamanashiYamanashi,, TokojichoTokojicho,, 1955-11955-1,, KofuKofu,, 400400,, JapanJapan..

†A.tAo Chikayam Chikayamaa GeGemm LaboratoryLaboratory,, OgikuboOgikubo,, 1-36-161-36-16,, TokyoTokyo,, 167167,, JapanJapan..

AbstracAbstractt IntroductioIntroductionn InclusionInclusionss iinn emeraldemeraldss frofromm SantSamaa TerezinhTerezinhaa ddee GoiásGoi:is,, ThThee SantSantaa TerezinhTerezinhaa emeralemeraldd hahass beebeenn reportereportedd BrazilBrazil,, araree investigateinvestigatedd bbyy electroelectronn microprobmicroprobee analysianalysiss firstlfirstlyy bbyy LiddicoaLiddicoatt (1983)(1983),, anandd comprehensivelcomprehensivelyy bbyy (EPMA)(EPMA).. ThThee inclusioninclusionss araree determinedeterminedd aass pyritepyrite,, CassedannCassedannee anandd SaueSauerr (1984)(1984).. TheTheyy reportereportedd oonn magnesioferritmagnesioferritee anandd micmicaa (possibl(possiblyy biotite)biotite).. localitylocality,, historyhistory,, geologgeologyy anandd gemmologicagemmologicall properproper­­ tietiess includinincludingg inclusionsinclusions.. OOnn inclusionsinclusions,, thetheyy listelistedd chromitechromite,, pyritepyrite,, biotitebiotite,, calcitcalcitee anandd two-phastwo-phasee inclusionsinclusions.. SpeciaSpeciall regarregardd musmustt bbee paipaidd ttoo pyritpyritee anandd chromitechromite.. FoForr pyritepyrite,, ththee localitlocalityy iiss ththee onlonlyy ononee excepexceptt ColombiColombiaa whoswhosee emeraldemeraldss includincludee pyritespyrites.. FoForr chromitechromite,, ththee basibasiss ooff theitheirr identificatioidentificationn reliesrelies oonn ththee presencpresencee ooff chromiuchromiumm detectedetectedd bbyy X-rayX-ray fluorescence. ThereThere maymay bbee somesome doubtdoubt asas toto whetherwhether chromiumchromium was duedue toto ththee inclusioninclusion oror thethe hosthost crystal,crystal, becausebecause ofof thethe ratherrather broadbroad analysinganalysing areaarea ofof thethe method.method. Fortunately,Fortunately, wewe obtainedobtained somesome cutcut samplessamples inin whichwhich a fewfew inclusionsinclusions appearedappeared onon facetsfacets andand werewere ableable toto investigateinvestigate thethe inclusionsinclusions withoutwithout damagedamage toto thethe facetedfaceted stones.stones. Fig.Fig. I.1. PyritePyrite inclusioitinclusion inin emerald;emerald; diameterdiameter ofof pyritepyrite approxi­approxi­ matelymately O.2mm.0.2mm.

Fig.Fig .2b. 2b . CharacteristicCharacteristic ;X-ray X-ray image image (sulphur). (sulphur) . TheThe same same position position Fig. 2a. SEM photograph of the pyrite appearing on a facet. Fig. 2a. SEM photograph of the pyrite appearing on a facet. asas FigureFigure 2a2a. .

©© CopyrightCopyright the the Gemmological Gemmologica lAssociation Association ISSN:ISSN :0022-1252 0022-1252 378 J. Gemm., 1987, 20, 6

facet edge. We detected iron and sulphur, but cannot detect zinc by EPMA. Figures 2a and 2b show a scanning electron microscope (SEM) image and a characteristic X-ray image (for sulphur) of the inclusion. Further semi­ quantitative analysis of the inclusion revealed that the ratio or iron to sulphur was Vz and the inclusion can be concluded to be pyrite. Figure 3 shows typical inclusions in Stanta Terezinha emerald which we describe as 'coal-like'. They are present as rounded crystals and distributed as clouds. Each individual crystal is 50~100//,m in size. A few of them occasionally appeared on the table facet (Figure 4); one shows a rod-like shape on Fig. 3. 'Coal-like' inclusions in emerald. Each crystal is about the facet. An SEM photograph is shown in Figure 50/z,m~100ju,m. 5. Compositions were analysed at three points on the included crystal. Elements Mg, Fe. Cr and traces of Ni, Cu were detected. Chromium was also Results detected by EPMA which has an analysing area Two specimens of emerald were examined by much smaller than X-ray fluorescence analysis. microprobe EPMA (JEOL - 733). Experimental Figures 6a and 6b show the concentration of conditions were: acceleration voltage 25 kV; absorp­ magnesium and lack of aluminium in the included -8 tion current 1.0 x 10 amperes. crystal. These results suggest that the inclusion is Figure 1 shows inclusions in the Santa Terezinha magnesioferrite [Mg(Fe,Cr)204] or magnesio- emerald. They occur as well-formed or slightly chromite [(Mg,Fe) (Al5Cr)204] rather than chromite rounded cubes with metallic lustre. Their diameters [FeCr204]. All belong to the spinel series. are about 0.2mm and one (lower left) appears on a

Fig. 4. One of the 'coal-like' inclusions on a facet which shows Fig. 5. SEM photograph of the rod-like crystal. The white bar rod-like shape (arrow indicates). White bar represents represents IO/AHI. 1000/xm. J. Gemm., 1987, 20, 6 379

Fig. 6a. and 6b. Characteristic X-ray images (Mg and Al) of the same crystal as in Figure 5. These photographs reveal the concentration of Mg and the lack of Al in the crystal. White bar represents 10/um.

biotite) by the high concentration of potassium together with aluminium and magnesium.

Conclusion In emeralds from Santa Terezinha, three types of inclusion minerals can be identified by EPMA. They are pyrite, mica and magnesioferrite. The existence of pyrite in these emeralds is very important, since no other locality except Colombia has provided emeralds with pyrite inclusions. Hereafter we cannot conclude that an emerald must come from Colombia simply because it contains pyrite as an inclusion.

References Fig. 7. SEM photograph and the line profile of K concentration on the other included crystal. This crystal may be biotite. Liddicoat, R.T., jr, 1983. New emerald mines at Santa Terezinha White bar represents 10/otm. de Goiás, Brazil. Proc. of the 19th International Gemmological Conference, Sri Lanka. Figure 7 shows a SEM image and line profile of Cassedanne, I.P. and Sauer, D.A. 1984. The Santa Terezinha de the potassium content of another included crystal. Goiás emerald deposit. Gems Gemol., 20, 1-13. The crystal was determined as mica (possibly [Manuscript received 5 June 1986] 380 J. Gemm., 1987, 20, 6

Gemmological Abstracts

BALFOUR, I. 1986. Famous diamonds of the world, was visiting Brazil in I860, the Emperor Maximilian XXVI. La Belle Helene. Indiaqua, 44 (1986/2), was a cushion-cut stone weighing 41.94 ct, and was 125-7. so named after the Archduke became Emperor of Found early in 1951 in one of the Consolidated Brazil in 1864. The diamond survived Maximilian's Diamond Mine's southernmost workings along the execution in 1867, and after being bought by a inhospitable Namibia coast, La Belle Helene was a Chicago diamond dealer in 1919, was eventually perfect blue-white stone weighing 160 ct. It was sold by him to a private collector in New York in bought by Mr Romi Goldmuntz and cut in his New 1946. P.G.R. York premises to yield three gems: two pear-shaped stones of 30.38 and 29.71 ct, and a marquise of BANK, H., 1986. Gemmologische Kurzinform­ 10.50 ct, all of which were sold through Carrier's to ationen. (Short gemmological notes.) Zeitschrift private buyers. P.G.R. der Deutschen Gemmologischen Gesellschaft, 35, 3/4, 185-9. BALFOUR, I. 1986. Famous diamonds of the world, Four short articles, each with its own bibliography. XXVII. The Vainer Briolette. Indiaqua, 44 The first note deals with an olivine from the Eifel, (1986/2), 129-30. between Mayen and Gerolstein, from the volcanic Although the origin of the 202.58 ct rough limestones present there. These local stones are of diamond that yielded the 116.60 Vainer Briolette is interest only to collectors as they are too small to be not known, it is believed to be a South African cut. An olivine of brownish-olive colour was stone. In its rough state, the diamond was discussed that had an exceptionally high RI, nx yellowish, lightly spotted, and of an almost perfect 1.670, ny 1.688, nz 1.706, SG 3.43. Dr Bank then octahedral shape. It was cut in London in 1985/6 by discusses Brazilian scheelite (yellowish-white, or the firm of M. Vainer Ltd. to produce a principal grey to brown and colourless), H 4.5-5, and stone (which has the distinction of being the largest senarmontite. The other two notes have been diamond briolette in the world) plus five other gems worked on by Dr Bank with Th. Lind and U. Henn weighing a total of 14.93 ct. The Vainer Briolette and deal with emeralds from S ta Terezinha de was purchased by the Sultan of Brunei. P.G.R. Goias, Brazil, with relatively high RI, and with synthetic emeralds produced hydrothermally in the USSR, showing growth irregularities and 'nail­ BALFOUR, I. 1986. Famous diamonds of the world, like' inclusions. E. S. XXVIII. Matan. Indiaqua, 45 (1986/3), 123-4. The Matan (or 'Mattam') takes its name from a town in West Borneo. The diamond was discovered BRIGHTMAN, R., SANDEMAN, D., 1986. Boulder there in the local diamond mines in the early 1800s, opal triplet imitating natural solid boulder opal. and was said to weigh 367 ct. When cut, the stone Australian Gemmologist, 16, 4, 151-2, 4 figs in was described as being about the size of a walnut colour. and drop-shaped. The present whereabouts of the Several opals were found to be triplets made by gem is unknown, but it may have been part of cementing a layer of fine crystal opal, with a mixture the cargo of diamonds shipped out of Borneo by of powdered ironstone and resin, to a genuine the Japanese during World War II. The cruiser boulder opal base. These are convincing imitations carrying the shipment was sunk off the coast of but may show bubbles in the cement layer, which Eastern Sumatra. P.G.R. will soften under a hot needle. They originate from Hong Kong. R.K.M. BALFOUR, I. 1986. Famous diamonds of the world, XXIX. Emperor Maximilian. Indiaqua, 45 BROWN, G., 1986. An unusual keshi pearl. Australian (1986/3), 126-8. Gemmologist, 16, 4, 139-40, 2 figs. Describes a large adventitious bouton pearl with Acquired by Archduke Maximilian (younger a non-nacreous back. Thought to be tissue brother of Joseph I, Emperor of Austria) when he nucleated. R.K.M. J. Gemm., 1987, 20, 6 381

BROWN, G., 1986. The gemmology of the shell in unpolarized light. A synthetic amethyst had a cameo. Australian Gemmologist, 16, 4, 153-61, 'nailhead' hydrothermal-type inclusion. A natural 19 figs in colour. andalusite with curved growth lines was seen. An excellent account of various shell cameos. Faceted orange clinohumite, cut and rough R.K.M. (RI 1.631-1.668, biaxial positive, SG 3.18) were donated to the GIA. A diamond with a heart-shaped BROWN, G. 1986. Benitoite. Wahroongai News, 20, cloud inclusion was seen. 12, 4-7, 4 figs. Synthetic spinel soudé stones with sintered glass A good summary of the known facts of this rare coloured layers investigated and one found which gemstone. Normally blue, a 'reddish' variety is gave an RI of 1.682 for the glass, as well as the mentioned. expected 1.724 for the spinel crown. A white This may stem from a report of a pink benitoite 'breadcrumb' inclusion was seen in a hydrothermal mentioned by Anderson in the fourth edition of synthetic emerald. 'Lapis' beads were proved to be Webster's Gems. Abstracter believes that the pink surface-dyed dolomite. Natural pearl was badly stone was reported from one of the West Indian eroded by skin acid. 'Coques de perle' imitations islands and that nothing more was heard of it. were found to have been worked from nautilus R.K.M. shell. A large weakly chatoyant pink cabochon represented as analcime was identified as petalite. A CASSEDANNE, J. 1986. L'améthyste de Pau d'Arco necklace of dark beads was found to be quartz (Para-Brésil). (Amethyst from Pau d'Arco (Para, heavily included with pyrite crystals. All items are Brazil). Revue de Gemmologie, 89, 12-15, 9 figs illustrated. R.K.M. (8 in colour). Two new locations for amethyst have been GAUTHIER, J.-P. 1986. Synthese et imitation de discovered in the Amazonian forest in the state of l'opale noble. (Synthesis and imitation of precious Para, Brazil. The locations are known as Pau d'Arco opal.) Revue de Gemmologie, 89, 16-23, 12 figs. and Maraba. Colour banding, goethite crystals A useful review of the known facts about the and fibres are all prominent inclusions. SG is 2.66 synthesis of opal and the nature and manufacture of and RI 1.544 and 1.553 with a DR of 0.009. An its various imitations. Electron microscopy of opal absorption band exists between 560 and 520 nm. structure is described and illustrated. M.O'D. There is no luminescence and stones will lose colour when heated to 450°C, passing through a grey-violet GÜBELIN, E. 1986. Die diagnostischen Eigenschaften colour at 350°C. M.O'D der neuesten Synthesen. (Diagnostic features of the latest synthetics.) Goldschmiede Zeitung, 81, ELLIOTT, J. 1986. Contemporary intarsia: the 11, 69-76, 47 figs in colour. Medvedev approach to gem inlay. Gems & Characteristic inclusions are described and Gemology, XXII, 4, 229-34, 6 figs in colour. illustrated for emerald (Lennix, Biron, Russian A revival, by a Russian artist lapidary, of skilled hydrothermal and fluxan d Seiko), ruby (Lechleitner) inlay of stone in contrasting colours. Nicolai and sapphire (Seiko and Lechleitner). A yellowish Medvedev now works in the United States, and an alexandrite-like Lechleitner product are also producing remarkably fine, high quality work in illustrated. M.O'D. thin veneers of opaque stone such as malachite, lapis lazuli, sugilite, opal and rhodochrosite, each GÜBELIN, E. J., 1986. The distinguishing criteria of piece selected, sawn, cut and polished to an exact fit the garnet family with special emphasis on in a highly intricate design, whether for boxes or for inclusions. Indian Gemmologist, 1,1,5-14,16 figs in colour. flat pendant pieces. A remarkable skill reminiscent of earlier times. R.K.M. A full account of the characteristic inclusions to be found in gem species of garnet with high-class FITZGERALD, S., RHEINGOLD, A.L., LEAVENS, P.B. colour illustrations. M.O'D. 1986. Crystal structure of a Cu-bearing vesu- vianite. American Mineralogist, 71, 1011-14. GÜBELIN, E., KOIVULA, J.I., 1986. Inklusen im A blue Cu-bearing vesuvianite from Franklin, Bernstein. (Inclusions in amber.) Zeitschrift der New Jersey, was determined and the formula given. Deutschen Gemmologischen Gesellschaft, 35, 3/4, M.O'D. 73-86, 45 figs in colour. The article consists of a short introduction and 45 FRYER, C.W. (Ed.), CROWNINGSHIELD, R., HURWIT, beautiful photographs of plant and animal inclusions K.N., KANE, R.E. 1986. Gem Trade Lab Notes. in mainly Dominican and Baltic amber (a couple of Gems & Gemology, XXII, 4, 235-40, 19 figs in illustrations are of copal resin from Colombia and colour. Africa), including a photograph of a rare scorpion A natural amethyst showed Brazil twinning even inclusion. E.S. 382382 JJ.. Gemm.Gemrn.,, 1987,20,61987, 20, 6

HANNI,HÄNNI, H.A.H.A.,, 1986.1986. BehandeltBehandeltee KorundeKorunde mimitt KIEFERTKIEFERT,, L.,L., SCHMETZER,SCHMETZER, K.K.,, 1986.1986. RosafarbeneRosafarbene glasartigeglasartigenn FüllungenFtillungen.. (Treated(Treated corundumscorundums withwith undund violetteviolette SapphireSapphire auauss NepalNepal.. (Pink(Pink andand violetviolet glassyglassy fillings.) Zeitschrift der Deutschen Gem­Gem- sapphiressapphires fromfrom Nepal)Nepal).. Zeitschrift der Deutschen mologischen Gesellschaft, 35,35, 3/4,3/4, 87-96,87-96, 8 figs Gemmologischen Gesellschaft, Gesellschaft, 35, 35 ,3/4, 3/4 ,113-25, 113-25 ,16 1 6 (5(5 iinn colour).colour). figs ((66 inin colour).colour). DurinDuringg thermathermall treatmenttreatment ooff corundums,corundums, ThThee exacexactt occurrenceoccurrence ooff thesethese sapphiressapphires fromfrom chemicalchemicalss areare appliedapplied whichwhich mamayy forformm glassyglassy NepaNepall iiss unknown.unknown. ThThee coloucolourr iiss causedcaused bbyy coatingscoatings oror fillingsfillings ooff cavitiecavitiess andand fissures. ThisThis iiss chromiumchromium (pink)(pink) anandd a combinatiocombinationn ooff chromium,chromium, practisepractisedd iinn increasingincreasing measurmeasuree mainlmainlyy iinn Thailand.Thailand. ironiron anandd titaniutitaniumm (violet).(violet). AssociateAssociatedd mineralsminerals TheThe applieappliedd glasseglassess varyvary inin theirtheir Si,Si, AIAI,, MgMg,, Ca,Ca, NaNa founfoundd werewere calcite,calcite, phlogopitephlogopite,, margaritemargarite anandd andand K content.content. TheThe introductiointroductionn ofof thesthesee glassesglasses rutilerutile.. ThThee samplessamples showshow intercalatedintercalated lamellaelamellae ooff intintoo crackscracks cacann improvimprovee ththee transparencytransparency ooff thethe corundumcorundum inin twitwinn positiopositionn andand straightstraight parallelparallel stonestone significantly,significantly, but,but, iiff thethe coolincoolingg raterate iiss low,low, growthgrowth planesplanes.. SmallSmall plateletplateletss ofof micamica seemseem toto bbee partiapartiall recrystallizatiorecrystallizationn ofof thethe glasglasss maymay occur,occur, thethe mostmost characteristiccharacteristic inclusioninclusion ofof thithiss neneww leadinleadingg toto aann opaqueopaque filling. filling. EE.. S.S. locality.locality. TheThe sapphiressapphires alsalsoo showshow healehealedd anandd unhealedunhealed fracturesfractures,, makingmaking thethemm somewhatsomewhat unun­­ suitablesuitable forfor jjewellery e wellery purposes.purposes. E.S.E. S. HAZEN,HAZEN, R.M.R.M.,, AuAu,, AA.Y.,. Y., FINGER,FINGER, L.W.L.W. 1986.1986. High-pressurHigh-pressuree crystalcrystal chemistrchemistryy ooff berylberyl (Be3AlzSi601s)(Be3Al2Si60i8) andand euclaseeuclase (BeAlSi0440H).OH). KOlVULA,KOIVULA, J.I.J.I., , 1986.1986. Three-phasThree-phasee inclusioninclusionss iinn American Mineralogist, 7171,977-84,, 977-84, 2 figs. 'Regency''Regency' syntheticsynthetic hydrothermalhydrothermal emerald.emerald. ObjectivesObjectives ooff ththee studystudy werewere toto determinedetermine Zeitschrift der Deutschen Gemmologischen Gesell­Gesell­ pressure-volumpressure-volumee equation-of-stateequation-of-state parameterparameterss andand schaft, 35,35, 3/4,3/4, 97-997-9,, 2 figs inin colour.colour. compressioncompression anisotropicanisotropiess bbyy measurinmeasuringg ththee prespres­­ ThThee papepaperr describesdescribes thethe discoverdiscoveryy ofof trutruee three­three- sursuree variatiovariationn ofof uniunitt cellcell dimensions;dimensions; toto calculatecalculate phasephase inclusionsinclusions iinn VacuumVacuum VentureVenturess 'Regency­'Regency- polyhedrapolyhedrall bulbulkk modulmodulii fromfrom high-pressurhigh-pressuree struc­struc­ created'created' hydrothermahydrothermall syntheticsynthetic emeraldsemeralds.. ThThee turturee data,data, ttoo testestt ththee effectseffects ooff structurestructure onon thethe threethree separateseparate phasesphases comprisingcomprising thesthesee inclusionsinclusions modulmodulii andand toto identifyidentify geometricalgeometrical changeschanges iinn thethe araree containedcontained withiwithinn thethe spike-shapedspike-shaped voidsvoids beryberyll anandd euclaseeuclase structures.structures . FindingsFindings arear egiven given commonlycommonly associatedassociated witwithh hydrothermalhydrothermal syntheticsynthetic inin tabulatabularr formform.. MM.. O'D.O ' D. emeralds.emeralds. TheThe solidsolid daughterdaughter crystalcrystalss displadisplayy thethe habithabit ofphenakiteof phenakite anandd areare biréfringentbirefringent.. EE.S.. S.

hER,IYER, J.P.J.P.,, 1986.1986. PannaPanna diamonddiamondss iinn ththee worldworld KOIVULAKOlVULA,, J.I.J.I.,, FRYERFRYER,, C.W.C.W.,, 1986.1986. HollanditHollanditee inin contextcontext.. Indian Gemmologist, 1,1, 1,1, 31-5,31-5, 5 figs.figs. quartz:quartz: a firstfirst observation. observation. Australian Gemmologist,Gemmologist, PannPannaa diamondsdiamonds araree generallgenerallyy ooff a highhigh standardstandard 16,16, 44,, 141-2,141-2, 3 figs.figs. ooff qualityquality,, sizesize anandd crystalcrystal perfectionperfection.. DiagramsDiagrams ooff A rarerare blackblack sub-metallicsub-metallic barium-iron-manganesebarium-iron-manganese thethe commonecommonerr formformss araree providedprovided.. M.O'D.M.O'D. oxidoxidee wawass founfoundd asas radialradial formationformationss iinn a largelarge facetedfaceted rock-crystalrock-crystal fromfrom MinasMinas GéraisGerais.. RR.K.M.. K. M. JHAVERIJHAVERI,, K.,K., 1986.1986. DiamonDiamondd gradinggrading.. IndianIndian Gemmologist, 1,1, 1,1, 19-25,19-25, 1010 figs.figs. KOlVULA,KOIVULA, J.I.,J.I., FRYERFRYER,, C.W.C.W.,, 1986.1986. Blue-greenBlue-green TheThe first parpartt ooff a promisedpromised seriesseries ofof paperspapers,, thisthis zircozirconn iinn PakistaniPakistani berylberyl.. Zeitschrift der Deutschen oneone dealdealss withwith ththee patpathh oflightof light inin a cutcut diamonddiamond andand Gemmologischen Gesellschaft, 35,35 , 3/43/4, , 101-3,101-3, withwith stylesstyles ofof cuttingcutting.. M.O'D.M.O'D. 1 fig inin colour.colour. IdiomorphouIdiomorphouss crystalscrystals ooff translucentranslucentt blue-greenblue-green KIEFERT,KIEFERT, L.,L., SCHMETZERSCHMETZER,, K.K.,, 1986.1986. MorphologieMorphologie zirconszircons werweree identifieidentifiedd foforr ththee first timtimee aass inclusionsinclusions undund ZwillingsbildunZwillingsbildungg bebeii synthetischensynthetischen blauenblauen iinn a palpalee blubluee aquamarinaquamarinee crystacrystall derivedderived frofromm aa SapphirenSapphiren vovonn Chatham.Chatham. (Morphology(Morphology anandd pegmatitpegmatitee inin northernorthernn Pakistan,Pakistan, situatedsituated neanearr thethe formationformation ooff twinningtwinning iinn ChathamChatham syntheticsynthetic blueblue Afghanistan,Afghanistan, RussiaRussiann andand ChineseChinese borders.borders. ThThee sapphires.)sapphires.) Zeitschrift der Deutschen Gem-Gem­ crystalwas2cmlong.crystal was 2cm long. EE.S.. S. mologischen Gesellschaft, Gesellschaft, 35, 35 ,3/4 3/4 127-38,127-38 , 101 0figs figs (2(2 inin colour).colour). KOIVULAKOlVULA,, J.I.,J.I., MISIOROWSKIMISIOROWSKI,, E.E. 1986.1986. GeGemm newsnews.. TheThe articlarticlee discussesdiscusses morphologicamorphologicall andand crystal­crystal- Gems & Gemology, XXII,XXII, 44,, 246-8246--8,, 4 figs iinn lographilographicc propertiesproperties ooff ChathaChathamm blubluee syntheticsynthetic colour.colour. sapphires.sapphires. MostMost crystalcrystalss showshow contactcontact twinning.twinning. .... IrradiateIrradiatedd greegreenn amblygonitamblygonitee seen.seen. BicolourBicolour InternaInternall structuralstructural propertiepropertiess suchsuch asas straightstraight green/oranggreen/orangee beryberyll frofromm MinasMinas GeraisGérais heatheatss ttoo parallelparallel growthgrowth planeplaness anandd twitwinn boundarieboundariess appliedapplied blue/pinkblue/pink.. ChalcedonChalcedonyy stainedstained blubluee withwith coppercopper ttoo ththee differentiationdifferentiation betweebetweenn naturalnatural anandd syntheticsynthetic saltssalts developsdevelops coppecopperr dendritesdendrites whenwhen treatedtreated corunducorundumm areare discussed.discussed. EE.S.. S. electrically.electrically. Chrome-greenChrome-green sphenesphene frofromm Baja,Baja, J. Gemm., 1987, 20, 6 383

California, is being marketed as Mexican emerald. Indian gem minerals, this section outlines the Green amazonite crystals found in Teller Co., geology of the beryl deposits with special reference Colorado. Pink/green West African tourmalines to aquamarine. M.O'D. used in carvings for Intergem '86 exhibition in Idar- Oberstein. Kenyan rubies are exported to Thailand PATTANI, H. 1986. The precious metal gold. Indian for heating to improve their transparency: results Gemmologist, 1, 1, 27-30. are said to be 'dramatic'. A green jade-like A short account of some of the uses for jewellery cabochon was shown to be meta-variscite. A new during the last 6000 years of gold and its various find of elbaite tourmaline reported from Minas standards/alloys - also of rolled gold and gold Gerais. R.K.M. plating. J.R.H.C

MISIOROWSKI, E.B., DIRLAM, D.M. 1986. Art PEARSON, G., 1986. Opal pineapples from White nouveau: jewels and jewelers. Gems& Gemology, Cliffs. Australian Gemmologist, 16, 4, 143-50, XXII, 4, 209-28, 22 figs in colour. 13 figs in colour. A beautifully illustrated paper on a fantasy art A detailed account of a new finding of these style which was largely killed by the grim realities of pseudomorphs of glauberite, usually described as the 1914—18 war. The paper deals briefly with a 'pineapples' and here referred to also as 'fruit'. number of the leading designers and makers of Difficult hand mining conditions are described. jewellery which was often characterized by whip­ Better specimens found in powdery white clay. lash lines and somewhat distorted naturalistic forms Cleaning of specimens presented difficulties. Some very skilfully executed in gems, precious metals and 'pineapples' are available for sale. R.K.M. enamels. Today these pieces are eminently collect­ able. R.K.M. POUGH, F.H., 1986. Gem treatment: opal. Lapidary Journal, 40, 7, 16-18. MOON, A.R., PHILLIPS, M.R., 1986. Inclusions in Brief summary of the various treatments applied sapphire and heat treatment. Australian Gem­ to opal and notes on some imitations. M.O'D. mologist, 16, 4, 163-6, 6 figs. A further examination of important features POUGH, F.H. 1987. Garnet. Lapidary Journal, 40, related to the current practice of heating sapphire 10, 16-18. rough to improve colour and/or asterism. R.K.M. A brief and general discussion of the garnet gem species. M.O'D. NAGIN, T., NAGIN, I., 1986. Quartz crystals of Colombia. Lapidary Journal, 40, 8, 38-41, 6 figs. POUGH, F.H. 1986. Zircon. Lapidary Journal, 40, A useful account of a quartz deposit at Alto de 9, 15-18. Cruces, Colombia, with descriptions of the crystals A short review of the various treatments applied and of their mode of formation. An Arkansas to gem-quality zircon. M.O'D. company is marketing them. M.O'D. READ, P.G., 1984-1985. (1) Spotting the Fakes, O'DONOGHUE, M., 1986. Gems and gemmology. Gem Instrument Digest, August 1984, 1, 6, 76-7, 1 Watchmaker, Jeweller and Silversmith, November, fig: (2) Gem Instrument Reports, ibid., 77-84, 14 45-7, 1 fig. figs: (3) Disclosure of Gemstone Treatments, id., The whole column is devoted to a detailed review November 1984, 1, 7, 90-1, 1 fig: (4) Gem of Gübelin's Photoatlas of inclusions in gemstones Instrument Reports, ibid., 91-8, 11 figs: (5) Gem from which a number of extracts are taken, dealing Instrument Design Trends, id., February 1985, 1, in particular with diamond, emerald and ruby. 8, 103-4,1 fig: (6) Gem Instrument Reports, ibid., (Author's abstract.) M.O'D. 104-11, 12 figs: (1) Diamond seems to be the only stone O'DONOGHUE, M. 1987. Gems and gemmology. identifiable with some certainty without the use of Watchmaker, Jeweller and Silversmith, January expensive research equipment: the risk of mistaken 1987, 47-9. identification increases as each new synthetic Among the topics discussed are the partially coloured stone is introduced. As each new effective restored Green Vaults at Dresden, glass made from test is discovered, manufacturers seem to go out of volcano ash, gem and mineral nomenclature and their way to defeat it, and we are back to using a cobalt-coloured natural blue spinel. gem's distinctive internal features to separate the (Author's abstract) M.O'D. genuine from the fake. PANJIKAR, J., 1986. Gem resources of India. Indian (2) Reports on Rayner LED-illuminated Dialdex Gemmologist, 1, 1, 15-17, 1 fig. refractometer; OPL Wavelength Spectroscope; The first part of a promised series of papers on Presidium DiaMeter; Eickhorst Uviscope Pocketlite; 384 J. Gemm., 1987, 20, 6

Gemlab Digital Spectroscope; Eickhorst Gemlyzer; (GIA Colormaster and Zeiss spectrophotometer). Diamontron thermal tester; Demetron UV curing Mention is made of the computer-based 'expert' adhesives and lamps; Diamond Mounting Gauge by network developed by American Gem Market Centennial Casting Co.; Master Pearl Grading Sets System (AGMS). (Author's abstract) P.G.R. (Midwest Gem Lab.); three new light sources (Illuminator/Magnifier by Beech & Son Ltd; Aristo READ, P.G. 1986. Fancy diamonds: treated or not? Mic-O-Lite illuminators; Omnilite high-intensity British Jeweller, September 1986, 39. fibre-optic probe). Contains a brief historical review of the alteration (3) The disclosure rules of the Federal Trade of a diamond's colour by irradiation and heating, Commission (USA) and CIBJO are compared and together with the methods of discriminating between discussed. treated and untreated diamonds. Since the discovery (4) Reports on GemPro Digital Analyser; that the diagnostic 595 nm absorption line in a Rayner Polariscope with Konoscope attachment; treated diamond can be eliminated if the stone is SKS Macroscopes; Eickhorst LED-Lite Refracto- heated to around 1000°C, identification problems meter Illuminator; widefield lens for Rayner S have existed. Drs Collins and Wood have solved Refractometer; battery/stand unit for Eickhorst these problems by detecting two more diagnostic Thermolyzer; Prior ZS2500 stereo-zoom microscopes; lines in treated diamonds at 1,936 and 2.024 nm. JDN FireScope; Leveridge gauge for mêlée weight (Author's abstract) P.G.R. estimation; Mettler CE 150 and AE500C electronic balances. ROHRBACH, R.P., 1986. Stars and stripes forever. (5) No major innovations in last two years other Lapidary Journal, 40, 7, 20-30, 8 figs in colour. than the GemPro, but some unusual features Non-rigorous account of asterism and chatoyancy introduced and existing instruments improved to in gemstones. M. O ' D. reduce cost and improve ease of handling. Queried whether Rofin 6010 unit (light source, scanning ROOT, E., 1986. Gems and minerals of the USSR. monochromator, sample holder/photodetector, with Lapidary Journal, 40,8,42-7,6 figs (5 in colour). absorption spectrum shown on standard oscillo­ A brief account of some of the gem materials to be scope) is 'poor man's version' of spectrophotometer. found in the Soviet Union, based on a tourist (6) Reports on Eickhorst Microlab; Spectroscope visit. M.O'D. Unit M-l (McCrone Research Associates); Kassoy Gemmological Microscope; two light sources (Krüss Roux, J. 1986. The information revolution - thirty fibre-optic units KL5120, KL5130; Kassoy halogen years on. Indiaqua, 45, 1986/3, 97-9. Jeweller's Lamp); static elimination (Zerostat 3; The author, formerly Information Officer of De 3M Anti-static mat; ASP40 Anti-static spray); Beers Central Selling Organization in London, Nelson Ray-path Unit; GRC Gem Color Analyzer; contrasts the early days, when diamond knowledge Pye Unicam PU8800 UV-Vis Spectrophotometer and lore were jealously guarded and passed down ('Basil Anderson Spectrophotometer'). J.R.H.C. from father to son, with the printed information explosion of the present day. P.G.R. READ, P.G. 1986. A question of colour. Canadian Jeweller, November 1986, 25-7, 9 figs in colour. SCHLÜSSEL, R. 1986. Nouveau traitement de rubis The mechanism of colour production in gem- naturels. (New treatment for natural rubies.) stones is discussed (transition elements in allo- Revue de Gemmologie, 89, 4-8, 13 figs in colour. chromatic and ideochromatic gems, pleochroism, This paper forms the second part of an account of interference and diffraction effects, and colour methods used to improve the appearance of natural centres). The second part of the article comprises a rubies. Cavity filling is the technique mainly series of product knowledge profiles covering the described. M.O'D. characteristics and occurrence of twenty-two gem species. (Author's abstract) P.G.R. SCHMETZER, K., KIEFERT, L., 1986. Untersuchung eines Sapphir-Katzenauges aus Burma. (Investi­ READ, P.G. 1986. Grading coloured stones. gation of a sapphire cat's-eye from Burma.) Canadian Jeweller, November 1986, 11. Zeitschrift der Deutschen Gemmologischen Gesell­ A review is made of the politics and techniques of schaft, 35, 3/4, 105-11, 6 figs (1 in colour). instrumental colour grading for both diamonds and The chatoyancy was examined in a sapphire cat's- coloured gemstones. Instruments for diamond eye from Burma which did not show any needle or colour grading (Eickhorst Diamond Photometer, rod-type inclusions. The crystal was shown to be the Okuda Diamond Color Checker and the twinned, inclination angle about 11 degrees. Both Kalnew GemColor 2) are briefly described as are 'twins' have growth planes parallel to the hexagonal two instruments used for grading coloured stones dipyramid as well as glide planes parallel to the J. Gemm., 1987, 20, 6 385

basal pinacoid. Chatoyancy is presumed to be composition ever reported for tourmaline. The caused by total internal reflection at irregular patch­ postulation is of a possible solid-solution series like fissures on basal glide planes. E. S. between elbaite and a hypothetical Mn analogue 'tsilaisite'. RI was 1.621,1.649 with a DR of 0.028; SHIGLEY, J.E., FRITSCH, E., STOCKTON, CM., SG was 3.13. The stone is thought to have come FRYER, C.W., KANE, R.E. 1986. The gemological from Zambia. M.O'D. properties of Sumitomo gem quality synthetic yellow diamonds. Gems & Gemology, XXII, 4, SLAHOR, S., 1986. Mysterious moonstone. Lapidary 192-208, 20 figs in colour. Journal, 40, 7, 37, 1 fig. In 1985 Sumitomo Electric Industries produced Single page note on the legend and lore of gem quality yellow synthetic diamond crystals in moonstone. M.O'D. quantity. They now make them up to 2 carats in weight, primarily for the industrial market as heat SOBOTT, R.J., 1986. Gemmologisches Wissen im sinks and for precision cutting tools. But some have christlich geprägten Kulturraum zur Zeit des been faceted as gems, the largest to date being Frühund Hochmittelalters (7.-12.Jh.n.Chr.). a brilliant of 0.8 carat. Grown at high temperatures (Gemmological knowledge in the sacred arts and pressures in a metal flux solvent around seed between the 7th and 12th centuries AD.) Zeit­ crystals of synthetic diamond, giving crystals which schrift der Deutschen Gemmologischen Gesellschaft, are consistent in their properties. Yellow colour is 35, 3/4, 139-59, 4 figs in colour. due to dispersed nitrogen which is carefully Much work was done by medieval goldsmiths for controlled in amount. the church making extensive use of gemstones. The twenty samples examined were all deep Monks and bishops also wrote treatises on gems yellow, cleavage-free and with no prominent which are of great interest, but because of their lack inclusions. Growth trigons were absent. All were of knowledge of the subject, do not contribute to type lb and their spectra lacked the strong lines of the progress of gemmology. The author lists many the natural type la yellow diamond. Inert to such works and also quotes a number of original LWUV, the crystals glow greenish-yellow under texts in Latin with translations; the stones discussed SWUV. They are non-conducting of electricity, but by these medieval authors are mainly sapphires, their thermal conduction is similar to that of natural emeralds, amethysts and carbuncles. E. S. diamond. Specific gravity (3.505) is slightly lower than that for most natural stones. Inclusions: STRIPP, D.M. 1986. Beginner's luck. Lapidary random pinpoints of whitish material and some Journal, 40, 9, 24-31, 4 figs in colour. opaque crystals of flux. Some crystals had colourless The article describes a visit to the gem-hunting thread-like veins near their surfaces which were not grounds at Spruce Pine, North Carolina, USA, and retained in the cut stones; these are not seen in the emerald crystals recovered. M.O'D. natural diamonds. Parallel colour graining is a prominent feature of these synthetics, while a STRUNZ, H., WILK, H., 1986. Die modernen 'Maltese Cross' of wedge shapes is seen in some of Edelstein-Refraktometer. (The modern gem them. Polarizing microscope showed an interference refractometer.) Zeitschrift der Deutschen Gem­ pattern of a twisted dark cross. Two crystals were mologischen Gesellschaft, 35, 3/4, 161-77,13 figs. slightly magnetic. The article is sub-titled 'Basis, shape and Identification: the inert reaction to LWUV and materials of refractometers, how they are handled, the bright yellow under SWUV provide an easy their history and corrections'. European refracto­ test. Sharp absorption lines in the blue will confirm meters generally use Rayner reflectors, American natural yellows, but their absence cannot be taken ones a semi-cylindrical reflector. Indicatrix used to indicate a sure synthetic. Large stones of deep since 1910 gives rise to some misunderstandings yellow, at this stage, are unlikely to be synthetic. which are corrected. The author points out that the Pale yellows also seem unlikely to be made. A light entering the modern refractometer does not valuable paper on a significant synthetic. R. K. M. graze, but enters at an angle from below; also that the depth of the light from the reflector into the gemstone measures only a few wavelengths SHIGLEY, J.E., KANE, R.E., MANSON, D.V., 1986. (589nm). E.S. A notable Mn-rich gem elbaite tourmaline and its relationship to 'tsilaisite'. American Mineralogist, THEMELIS, T., 1986. Synthetic stars. Lapidary 71, 1214-16, 1 fig. Journal, 40, 7, 46-8, 6 figs in colour. A tourmaline with an uncommon yellowish- Straightforward account of the manufacture of green colour was found to have the most Mn-rich starstones. M.O'D. 386 J. Gemm., 1987, 20, 6

THEMELIS, T. 1986. Urano-pyrochlore in sapphire. from the neighbourhood of Böckstein.) Lapis, Lapidary Journal, 40, 9, 19, 2 figs in colour. 12, 2, 11-14, 11 figs (8 in colour). A short description, with references, of the Among the crystals found in the area of Böckstein uranium pyrochlore found as a reddish inclusion in are aquamarine and phenakite; the location is in the sapphire crystals from Pailin, Khmer Republic. eastern Austrian alps. M.O'D. M.O'D. ZEITNER, J.C., 1986. Phenomenal gems - find them VOGLER, K., 1986. Neue Untersuchungen an in the USA. Lapidary Journal, 40, 7, 32-6, 3 figs einem farblosen Chrysoberyll. (New investigation in colour. of a colourless chrysoberyl.) Zeitschrift der Useful account of some gem minerals found in Deutschen Gemmologischen Gesellschaft, 35, 3/4, the United States. M.O'D. 179-83, 2 figs. A colourless chrysoberyl of 8.2 ct of doubtful ZHOU, Y. 1986. Growth of high quality large origin, previously examined by K. Schmetzer Nd:YAG crystals by temperature gradient (Zeitschrift der Deutschen Gemmologischen Gesell­ technique (TGT). Journal of Crystal Growth, 78, schaft, 1985, 34, 1/2, 6-12*) has been re-examined 31-5, 6 figs. by non-destructive, chemical analysis (EDS XRF) Though usable laser rods of YAG doped with Nd and the presence of gallium was clearly shown. This are usually grown by the Czochralski pulling and other internal features showed the specimen to technique, such crystals often show an optically be of natural origin. E. S. inhomogeneous core region due to the convex interface attained during growth. TGT growth WINKLER, R. 1987. Berylliummineralien aus der allows the whole crystal rather than outer regions Umgebung von Böckstein. (Beryllium minerals only to be used. M.O'D.

Book Reviews

BRUTON, E. 1986. Legendary gems or gems that made (although the Persian Darya-i-Noor is now thought history. NAG Press, Ipswich (and Chilton Books, to be part of this stone). Chapter four includes the Radnor, Pennsylvania), pp.xii, 239. 23 colour story of the Great Blue diamond from which the plates, 75 figures. £15.95. extant Hope diamond may have been cut. Chapter This is essentially a narrative book, but it will also five explains the French connections of the Sancy, serve as a reference book on legendary gems. The Regent (Pitt) and Hortensia diamonds and tells of author has written authoritatively on diamonds, the wars and other international machinations clocks and many other subjects, and can truly list associated with them. Chapter six is a fascinating his professions as writer, publisher, horologist, mixture of history with science and includes gemmologist and restorer of old houses. accounts of the Florentine, De Beers, Red Cross, Chapters one and two deal in fascinating detail Kimberley, Tiffany, Wittelsbach, Dresden Green with the history of the Koh-i-Noor diamond from and other coloured diamonds. Chapter seven, its probable source in the Kollur mines in India, entitled 'The greatest gem of all time', is mainly through its acquisition by the Moguls and other devoted to the Cullinan diamond but inclusion of rulers, to its unfortunate re-cutting in the nineteenth the Excelsior and Star of Sierra Leone completes century and its incorporation in the British Royal the descriptions of the three largest known rough Regalia. Chapter three relates the stories of the gem-quality diamonds. Chapter eight is devoted to diamonds which have now vanished, including 'rubies' and sapphires - in particular to the Black the Great Mogul, the Moon of the Mountains, the Princes and Timur rubies, which are, of course, red Mirror of Portugal, the Pigot and the Great Table spinels. The legends surrounding the St Edwards and Stuart sapphires are covered in some detail and ^Abstracted in Journal ofGemmology, 1985, XIX, 8, 731. J. Gemm., 1987, 20, 6 387 the modern sapphire carvings of the heads of on his own wide experience, the author introduces various American presidents receive attention. some effective and ingenious methods and short Chapter nine is largely devoted to legendary cuts that save both time and cost or improve the emeralds, but famous aquamarines, alexandrites, work entailed. amethysts and opals, are also covered. Chapter ten With over 30 years' experience, in the UK, relates the stories of famous pearls from 2560 BC to Australia and New Zealand, the author provides the present day. Chapters eleven and twelve tried and tested advice on restoring all kinds of complete the narrative with 'Legends in the antique and modern jewellery, with particular making' and the stories of dealers and collectors of emphasis on the making and repairing of rings. He great gems. also describes some of the more unusual repairs to The foregoing summary of the chapters in this lockets, bracelets, earrings, brooches and watch- book cannot convey the extremely interesting way cases, including the making of joints, safety in which the various legends (and facts) surrounding catches, pins, respringing and polishing. The the fabulous gems are recounted. Access to in­ appendices also include a useful and comprehensive formation in the book is facilitated by the gemstone 'Jeweller's guide to gemstone handling' using a species arrangement, but the provision of a good lathe and, increasingly important these days, index is an even better way of finding a specific workshop security. P. R. topic. The author provides a good bibliography and freely acknowledges his debt to the authors of the source books listed. MITCHELL, R.H. 1986. Kimberlites, mineralogy, It would be surprising if no errors were to be geochemistry and petrology. Plenum, New York, found, and apart from minor typographical mistakes pp.xv, 442. $78.00. the reviewer could draw attention to the following The book is concerned primarily with the points. On page 139 it states that spinel is 'an oxide petrology of kimberlites rather than prospecting for of aluminium and manganese' and on page 161 that them. Though the occurrence of minerals in 'ruby and sapphire have a lower relative density' kimberlite is described in chapter six, the main aim than diamond! Figure 9-7 shows a celebrated gem- of the book is to give a survey of the advances made quality aquamarine crystal some 25cm high and not in kimberlite studies over the past 25 years. For this the Devonshire emerald, which has been clipped reason the discussion of diamond with respect to from the bottom of the picture. kimberlites is left to a short section towards the end The book was manufactured in the USA and the of the book. Discussion turns upon whether spelling is American, but this should not detract diamonds are xenocrysts in kimberlite; if they are, from its good narrative flow and the assemblage of then the role of the kimberlite is merely one of so much gemstone history and legend in one transportation. Diamond is regarded as a mineral convenient volume. E.A.J. which can occur in a variety of parageneses in the upper mantle so that several modes of origin are HICKLING, J. 1986. Practical jewellery repair. NAG possible. These are briefly discussed. M.O'D. Press, Ipswich, pp.vi, 192. Over 200 black and white illustrations. £9.95. TAYLOR, L. 1985. Struck by lightning. Jon the Well known for their range of practical books, Printer Pty Ltd, Ashmore, Queensland, pp.183. NAG Press Ltd, of Ipswich, have just published Illus. in black-and-white and in colour. $5.15. Practical jewellery repair, which is sure to become a Now published by the author at Box 675 PO, standard textbook for the amateur restorer of Surfers Paradise, Queensland, this cheerful book jewellery, as well as the working professional and consists mostly of anecdotes and poems, all with an apprentice. opal mining background and theme. Among the Starting where it all begins - in the workshop or tales are sections on the mining, selling and nature workroom - the author shows how a wide range of ofopal. M.O'D. repair work can be undertaken with even quite a modest set-up, that can be extended as finances and Some semi-precious and ornamental stones of South the skills of the user permit. Australia. Geological Survey of South Australia, There is a very thorough grounding in the various Adelaide, 1980. pp.159. Illus. in colour. Price on processes and materials required, including working application. with precious metals and solders and stocking some This is a useful survey with a considerable of the less expensive gemstones. Basic skills such as amount of detail given about the mines, their soldering, casting, wire-drawing, polishing, sawing owners and their production. Opal is not included. and filling, are fully explained and illustrated There is a map in a pocket at the back of the throughout with many clear line drawings. Based book. M.O'D. 388 J. Gemm., 1987, 20, 6

Proceedings of the Gemmological Association of Great Britain and Association Notices

GIFTS TO THE ASSOCIATION The computer, with its Gemdata program, The Council of the Association is indebted to Mr constitutes a means of rapid access to gemmological Peter Read for the gift of the computer installation data for both exam, revision and gem identification used by him to develop his Gemdata programs purposes. It is available for use, on request, to both (Read, 1980 and 1983), which is now installed in the students of gemmology and to visiting gemmologists, Association's library at Saint Dunstan's House. particuarly those who wish to evaluate the use of the The Gemdata program provided for use with the computer for gemmological purposes. computer has five sections: (1) Gem identification, using test inputs for RI References values, optic sign, SG, etc. Read, P. 1980. Computer-aided gem identification. Journal of (2) Gem data tables, arranged in alphabetic, RI and Gemmology, XVII, 4, 239-49. SG orders. Read, P. 1983. A computer program for gem identification. Gems (3) Gem data comparisons, enabling side-by-side & Gemology, XIX, 3, 157-63. comparisons of selected gems. (4) Gem data pages, comprising an encyclopaedia of over 200 gem materials with information on their constants, characteristics and principal NEWS OF FELLOWS occurrences. The Association's Honorary Treasurer, Mr Nigel (5) Gem calculations, for the determination of SG, Israel, of Nibris Books, is moving in April. His new reflectivity, critical angle and Brewster angle. address will be 1 Simon Lodge, 76 Victoria Drive, Wimbledon, London SW19 6HJ. Telephone 01-789 0200. Mr Michael O'Donoghue chaired a seminar on 'Geological and mineralogical literature' at the British Library's Science Reference and Information Service on 3 December 1986. Mr Nigel Israel presented a paper on The literature of gemmology' at the seminar.

MEMBERS' MEETINGS Midlands Branch On 20 February 1987 at Dr Johnson House, Bull Street, Birmingham, a talk was given by Mrs Carole Gibbs on the subject of tortoiseshell, including its recovery and marketing. On 20 March 1987 at Dr Johnson House, Mr Alec E. Farn gave a talk on pearls.

North West Branch On 16 October 1986 at Church House, Hanover Street, Liverpool 1, the Annual General Meeting was held, at which Mr S.G. Hill, FGA, was re­ The computer donated by Mr Peter Read, with the Gemdata elected Chairman and Mrs I. Knight, FGA, elected programs. Secretary. J. Gemm., 1987, 20, 6 389

On 20 November 1986 at Church House, Mr J. Mcintosh, Stewart F., Glasgow. 1986 Dickson gave a talk entitled 'Microscopy, equip­ Malhotra, Kapil, Bombay, India. 1986 ment and specimens'. Rowell, Unni G., Bloomington, Ind., USA. 1960 On 21 January 1987 at Church House, Mr J. Skoropad, John D., Edmonton, Alta, Canada. 1985 Condrupt of Sotheby's gave a talk on jewellery that Torrance, Claire H., Auckland, New Zealand. had been auctioned. 1986 On 18 February 1987 Dr G. Trecise arranged a Van Dijk-Pietrzak, Jolanta A., Utrecht, Netherlands. special viewing of gemmological specimens at 1986 Liverpool Museum. On 18 March 1987 at Church House, Mr John Ordinary Membership Pyke, Sen., gave a talk on his newly catalogued Andersen, Aud N., Grimstad, Norway. collection of gemstones. Aoki, Yuka, Osaka, Japan. Arthur, Lynne, Denny. EXTRAORDINARY GENERAL MEETING Atkins, Tristan A., Banstead. An Extraordinary General Meeting was held at Attar, Simon, London. the Royal Automobile Club, 89 Pall Mall, London Axell, Anita, Stockholm, Sweden. SW1, on 28 January 1987, at which special Barber, Susan A., Horsham. resolutions were passed making a number of Blain, Raymond E., Ashton-under-Lyne. changes in the Memorandum and Articles of Burns, Brenda, Edinburgh. Association. Chadwick, Valerie, Brighton. Chang, Kim, Taipei, Taiwan. COUNCIL MEETING Charrington, Rosa M., Beckenham. At a meeting of Council held at the Royal Curran, Paul H., Brighton. Automobile Club immediately following the Extra­ Damiani, Michael, London. ordinary General Meeting on 28 January 1987 the Dawes, Percival E., Stevenage. business transacted included Dominy, Geoffrey M., Edmonton, Alta, Canada. (1) the appointment to the Council and nomination Draper, Geoffrey J., Brighton. for election to the Council at the next Annual Edie, Anmie W., Ditchling. General Meeting of the following Fellows, Foster, Brenda C, St Albans. namely Drs A.J. Allnutt, G. Harrison Jones Fox, Anthony H., Maidenhead. and R.R. Harding and Messrs E.M. Bruton, Francis, Richard, London. A.E. Farn, E.A. Jobbins, D.G. Kent, P.G. Fukuda, Yoshie, Yokohama City, Japan. Read and K. Scarratt. Gray, Thelma, Burnley. (2) the establishment and terms of reference of an Hara, Yoshiko, Osaka, Japan. Executive Committee in accordance with the Hilton, Holly A., London. new Article 61. Hiramatsu, Ikuo, Tokyo, Japan. (3) the appointment to serve on the Executive Hirano, Masato, Tokyo, Japan. Committee of Sir Frank Claringbull (President), Hong, Chi-Won, Osaka, Japan. Mr David Callaghan (Chairman), Mr Noel Hori, Takeaki, Kyoto City, Japan. Deeks (Vice-Chairman), Mr Nigel Israel Hsieh, Chiun-in, Tokyo, Japan. (Honorary Treasurer), Dr G. Harrison Jones Iwasawa, Koichi, Tokyo, Japan. (Chairman of the Education Committee), Mr Jessop, Paul R., Glenrothes. E.A. Jobbins (Chairman of the Board of Kamei, Tsukumi, Osaka, Japan. Examiners), Drs A.J. Allnutt, R.R. Harding Kanodia, Jai P., London. and J.B. Nelson, and Messrs E.M. Bruton, Katz, Raff], London. CR. Cavey, A.E. Farn, P.G. Read, K. Scarratt Keast, Edmund J., Sanderstead. and C.H. Winter. Kingsley, Serena, Eastbourne. (4) receipt of a report of the recent satisfactory Larsson, Thomas, Järfalla, Sweden. business of Gemmological Instruments Limited. Lau, Kwok Hung, Kowloon, Hong Kong. (5) the election to membership of the following: Ley ens, Richard, London. Loveday, Dawn E., Caterham. Fellowship McDonagh, Bernard, Wrightington. Abell, Alison M., London. 1986 Manning, Mark J., North Lancing. Gentsidou, Fontini, Serres, Greece. 1986 Marumo, Kayo, Osaka City, Japan. Goodlin, Franceen D., Toronto, Ont., Canada. Matsumoto, Akira, Honjo City, Japan. 1986 May, James G., Belfast, N. Ireland. Lloyd, Jeremy J., Birmingham. 1986 Millar, Ewan, Paisley. 390 J. Gemm., 1987, 20, 6

Mohsinali-Esufali, Joher, Colombo, Sri Lanka. GEM QUALITY SYNTHETIC DIAMOND Montgomery, Keith B., Leeds. IS BEING MARKETED Mumabe, Atsuhiro, Tokyo, Japan. A synthetic diamond, identified at GIA's Gem Nimry, Lina, London. Trade Laboratory in New York, is the first Nordby, Anita, Oslo, Norway. indication that new synthetic diamonds are circulat­ Ogawa, Yoko, Kana Gawa Pref., Japan. ing in the gem market. GIA broke the news of the Olivares, Rosana, Gibraltar. new synthetics in January in the Institute's quarterly Owen, Margaret E., Pietermaritzburg, South Africa. journal, Gems & Gemology. The article, entitled Ozier, Stephen M., Bournemouth. The gemological properties of the Sumitomo gem- Raskin, David A., Glasgow. quality synthetic yellow diamonds', was prepared Reavell, David, Dunstable. by GIA's research department in Santa Monica, Roberts, Charles, San Antonio, Tex., USA. California. Rodwell, Peter F., Malmesbury. The colour of the 23 point stone, submitted by a Routledge, Hylton M., Bromsgrove. gem dealer, was a very intense yellow. Jewellers Sabel, Sara, London. should definitely be wary of any fancy yellow Sarna, Rajesh, Nairobi, Kenya. diamonds they come across in the trade. Sato, Hitoshi, Tokyo, Japan. Saunders, Geoffrey P., Transvaal, South Africa. Sayers, Charlotte A., London. Shread, Andrew, Beeston. Steedman, Pauline, London. Stone, Anthony R., Poole. Stone, Emma E., Derby. Straitouri, Sophia, London. Tabeling, Raymond W., Wilmington, Del., USA. Tajima, Hidemasa, Osaka, Japan. Tajima, Tomie, Kamakura City, Japan. Taylor, David J., Cowes, IOW. Uchibori, Satoru, Tokyo, Japan. Usui, Kenichi, Tokyo, Japan. An emerald-cut synthetic Sumitomo diamond. The distinctive Wadia, Aneeta, London. hourglass-shaped internal graining pattern has not been observed Warrington, Jeffrey T., Brighton. in any of the rough crystal sections studied. Wege, Joyce, Leeds. Photomicrograph by John Koivula, from Gems & Gemology, Weiss, Anthony S., Bushey. Winter 1986. Winterbottom, Martin, Watford. GIA Board Chairman, Mr Richard T. Liddicoat, Yanagi, Name, Tohka-Machi City, Japan. is not surprised at the appearance of the new Yang, Richard K. K., Kelantan, Malaysia. synthetics in the diamond market. 'As I wrote in ANALYSIS AND TECHNOLOGY Gems & Gemology', Mr Liddicoat says, 'we knew OF ANCIENT GEMSTONES they would show up. The question was when, and it The European University Centre for the Cultural turns out to be sooner rather than later. But then, Heritage is organizing an international symposium our labs are always among the first to see new on * Analysis and technology of ancient gemstones', synthetics whenever they appear'. to be held in Ravello, Italy, from 13 to 16 November The first synthetic diamonds were two stones 1987. Further details from Prof. T. Hackens, submitted by a customer on 18 February, with a European University Centre for the Cultural request for an origin of colour report. The smaller Heritage, Villa Rufolo, I 84010 Ravello, Italy. stone was identified as a diamond using a thermal inertia instrument, a standard test. It was then GEM TRADE RESTRICTIONS IN KENYA found to match the characteristics described in As from 30 December 1986 anyone trading in Gems & Gemology. minerals or gemstones in Kenya must have a licence. As a result of the enactment of the Statute GEM IDENTIFICATION COURSE Law (Miscellaneous Amendment) Act 1986, it is Two- and three-day courses on gem identification now illegal and an offence to be in possession of or run by Mr Alan Hodgkinson will be held at the trade in gemstones and/or other minerals without British Horological Institute, Upton Hall, Newark, registering and having obtained a mineral dealers Notts., in the autumn. licence from the Commissioner of Mines and Full details from the Retail Jeweller, 100 Avenue Geology. Road, London NW3 3TP. JJ.. Gemm.Gemm.,, 19871987,20,6, 20, 6 393911

LETTELETTERR TTOO THTHEE EDITOEDITORR cablcablee iiss nickenickedd frofromm youyourr wife'wife'ss ironiron** anandd ththee boboxx cacann bbee anythinanythingg handyhandy.. FromFrom BerniceBemice Backler WordWordss ooff warninwarningg -- beforbeforee switchinswitchingg oonn ththee BarnscottBarnscott GemologicalGemological && MetallogicalMetallogical Laboratory quartquartzz halogehalogenn lamlampp wipwipee iitt ofofff wit withh aa clotclothh dippedippedd iinn benzinebenzine,, whicwhichh disposedisposess ooff ananyy odditieodditiess youyourr DeaDearr SirSir,, sweatsweatyy pawpawss havhavee lefleftt oonn itit.. IIff yo youu don'don'tt ddoo thithiss youyourr FurtheFurtherr ttoo youyourr requesrequestt iinn VolVol.. 2020,, NoNo.4,. 4, p.241p.241,, lamlampp wilwilll ggoo 'bang''bang'.. rree loloww coscostt accessoriesaccessories,, wwee havhavee pleasurpleasuree imn ThThee ususee ooff thithiss lighlightt boboxx iiss manifolmanifoldd -- yoyouu wilwilll submittinsubmittingg ththee followingfollowing:: notnotee thathatt ththee holholee iinn ththee totopp througthroughh whicwhichh ththee lighlightt LetLet therethere bebe lightlight inin youryour darknessdarkness escapeescapess hahass twtwoo piecepiecess ooff aluminiualuminiumm U-sectioV -sectionn ThThee attacheattachedd sketcsketchh (w(wee mamayy bbee manmanyy thingthingss bubutt (wit(withh aa gagapp ooff approximatelapproximatelyy VsVs inch)inch).. IntIntoo thithiss UV­- nonott artistsartists)) showshowss thathatt aa light-sourclight-sourcee cacann bbee madmadee sectiosectionn araree placeplacedd stripstripss ooff blacblackk plastiplasticc witwithh holeholess witwithh aa minimaminimall amounamountt ooff expenditurexpendituree anandd effort. (t(too corresponcorrespondd ttoo ththee boboxx holehole)) ranginrangingg frofromm 1mImmm WWee ddoo nonott claiclaimm thathatt ththee ideideaa iiss originaloriginal,, onlonlyy thathatt uupp ttoo whawhatt yoyouu needneed.. HerHeree yoyouu cacann checcheckk rougroughh wwee puputt braibrainn iinn geagearr anandd gogott ththee pumpkipumpkinn pipipp stonestoness foforr flaws,flaws, crackscracks,, inclusionsinclusions,, etcetc.. AnotheAnotherr movinmovingg afteafterr readinreadingg aann articlarticlee bbyy HugHughh Crawford.Crawford. worwordd ooff warninwarningg -- unlesunlesss yoyouu wanwantt ttoo makmakee youyourr ThThee sketcsketchh iiss virtuallvirtuallyy self-explanatorself-explanatoryy excepexceptt ttoo doctodoctorr richrich,, don'don'tt loolookk directldirectlyy intintoo ththee lighlightt - iitt iiss sasayy thathatt ththee transformetransformerr anandd fafann araree connecteconnectedd intintoo powerfupowerful-l - vievieww obliquelyobliquely.. ththee samsamee electrielectricc linlinee wherwheree ththee switcswitchh wilwilll operatoperatee FoForr instanceinstance,, yoyouu cacann checcheckk garnegarnett foforr flaws, botbothh whewhenn iitt iiss activated.activated. inclusionsinclusions,, etc.etc.,, pearlspearls,, aquamarineaquamarine,, yoyouu namnamee itit..

Aluminium BOBOXX HOUSINHOUSINGG (flexible l7------~-----Hole— Hole Fibre optic light (flexible tube)

FunneFunnell linedlined -T------t-witwithh aluminiualuminiumm foilfoil

(flexible

(flexible Switch Steel plate

Reflector~r-----~ LampLamp 1212VV r------~~------~quartzquartz halogenhalogen oror o 0 tungstentungsten halogenhalogen Heavy duty 12 V --+----4- transformer

GettingGetting thethe partsparts isis fairlyfairly simplesimple -- youyou scroungescrounge ToTo checkcheck a diamonddiamond againstagainst a simulant,simulant, placeplace a themthem -- thethe flexibleflexible fibre opticoptic tubetube cancan bebe obtainedobtained piecepiece ofof groundground glassglass inin thethe V-section,U-section, positionposition thethe fromfrom anyany abominableabominable surgeon,surgeon, oror hospital,hospital, whowho diamonddiamond tabletable downdown andand ifif aa darkdark starstar appearsappears inin thethe throwthrow themthem outout whenwhen theythey break.break. TheThe fanfan isis culetculet youyou havehave a diamond,diamond, ifif not,not, youyou havehave obtainableobtainable fromfrom a refrigerationrefrigeration engineerengineer whowho alsoalso somethingsomething else.else. throwsthrows outout andand replacesreplaces withwith new;new; thisthis isis aa coldcold Cement,Cement, withwith epoxy,epoxy, thethe fibrefibre opticoptic intointo aa sheetsheet ofof countercounter fan.fan. TheThe quartzquartz halogenhalogen headlampheadlamp andand steelsteel andand youyou havehave aa totallytotally movablemovable lightlight source.source. reflectorreflector comescomes fromfrom aa motormotor scrapyard,scrapyard, thethe electricelectric *This*This couldcould bebe dangerousdangerous onon atat leastleast twotwo counts!counts! -- Ed.Ed. 392392 J.J. Gemm.Gemm.,, 1987,20,61987, 20, 6

WitWithh a bitbit ofof ingenuityingenuity (an(andd anyonanyonee whwhoo isis a thisthis yearyear.. ThiThiss issuissuee wilwilll compriscomprisee numbersnumbers 7 andand 8 membememberr ofof ththee GGAA isis ingenious)ingenious) a clamclampp cacann bebe ooff thethe currencurrentt volumvolumee whichwhich meansmeans thathatt membersmembers madmadee ssoo thathatt thithiss lighlightt sourcsourcee isis usedused,, forfor instance,instance, willwill not receivreceivee a journajournall inin July.July. oonn thethe microscope.microscope. WithWith felicitationsfelicitations fromfrom ththee mamadd professor.professor. IfIf youyou CHALCOPYRITCHALCOPYRITEE IINN PERIDOTPERIDOT publispublishh thithiss I'llI'll sendsend youyou more,more, ifif yoyouu don'don'tt I'llI'll useuse InIn thethe papepaperr bbyy J.J. KoivulaKoivula anandd C.WC.W.. Fryer,Fryer, mymy alchemyalchemy ttoo turnturn yoyouu intintoo somethingsomething thatthat (Journal of Gemmology, 2020,, 55,, 272-3)272-3),, thisthis wawass shiveredshivered inin youryour recentrecent colcoldd spell.spell. claimedclaimed ttoo bebe ththee firstfirst recorderecordedd occurrencoccurrencee ooff chalcopyritechalcopyrite inin peridotperidot.. WWee havehave beebeenn informed,informed, YoursYours etc.,etc., however,however, bbyy DDrr H.JH.J.. SchubnelSchubnel ooff Paris,Paris, thatthat hehe BernicBernicee BacklerBackler describeddescribed chalcopyritechalcopyrite inin peridotperidot inin a paperpaper 1919 JanuaryJanuary 19871987 publishepublishedd inin 19681968 (Giraud,(Giraud, R.R.,, PicotPicot,, P.,P., andand 2c2c MedicaMedicall CentraCentra,, 7979 ComptoComptonn Street,Street, SchubnelSchubnel HJ.H.J.,, 1968.1968. LeLess inclusioninclusionss spheroidalessphérofdales PPOO BoBoxx 1692,1692, PinetownPinetown 3600,3600, SouthSouth Africa.Africa. desdes gemmesgemmes dede rocherochess ultrabasiques.ultrabasiques. Revue de Gemmologie, NoNo.. 14,14, 9—11)9-11).. WeWe apologizeapologize toto DrDr ANNUALANNUAL GENERALGENERAL MEETINGMEETING SchubnelSchubnel forfor thisthis error.error. TheThe AnnuaAnnuall GeneraGenerall MeetinMeetingg ooff ththee AssociationAssociation iiss ttoo bbee helheldd oonn TuesdaTuesdayy 1616 JuneJune 19871987 aatt thethe FlettFlett CORRIGENDCORRIGENDAA OOnn pp.. 176176 above,above, 1st1st column,column, linlinee 15,15, forfor TheatreTheatre,, GeologicalGeological Museum,Museum, ExhibitionExhibition Road,Road, 3 SouthSouth Kensington,Kensington, LondoLondonn SW7,SW7, atat 6.306.30 forfor 'en<(T b - Hc)/(lHc)/a.. -T- Tb))'' reareadd 'H^lKl'HcT1!(l- - Tb)'·Tb)\ OnOn p ..176 176 above,above, 2nd2nd column,column, lineslines 2, 3 andand 8,8, forfor 7.007.00 pm.pm. ThisThis willwill bebe followefollowedd bbyy a GemmologicalGemmological 3 3 Forum,Forum, whewhenn a panelpanel ooff expertsexperts willwill bbee answeringanswering <('(11 - TTb)Hc/(I-b)Hc/(l - TT1)'b)' reareadd Hc(l-Hc(l - TT1)/(1b)/(1 - Tb)'.Tb)\ questionquestionss onon a numbernumber ofof subjects.subjects. OOnn p.287p.287 above,above, thethe captioncaption toto ththee laslastt figurfiguree inin ththee 2nd2nd columncolumn shouldshould readread Tig'Fig.. 7.7. ThThee thinthin THTHEE JOURNALJOURNAL OOFF GEMMOLOGYGEMMOLOGY sectionsection ooff a naturalnatural freshwaterfreshwater pearpearll (Laboratory(Laboratory COMBINEDCOMBINED ISSUEISSUE collection).'collection).' TheThe EditoEditorr iiss pleasepleasedd ttoo announceannounce thathatt followingfollowing OnOn p.28p.2888 aboveabove,, ththee captioncaption toto ththee firsfirstt figure inin thethe successfulsuccessful launclaunchh ofof ththee presenpresentt volumvolumee ofof The ththee 1st1st columcolumnn shouldshould reareadd Tig'Fig.. 6.6. A closercloser viewview ooff Journal of Gemmology inin itsits newnew format,format, plansplans areare thethe internainternall structurestructure ofof a freshwaterfreshwater pearpearll seenseen inin underwaunderwayy ttoo develodevelopp ththee contentcontentss ooff thethe JournalJournal FigurFiguree 5.'5.' furthefurtherr iinn a wayway ttoo maximizmaximizee ththee interesinterestt andand OnOn p.289p.289 above,above, ththee illustrationillustrationss ttoo figuresfigures benefibenefitt toto thethe readershipreadership.. AAss a resultresult ofof thesthesee plans,plans, 1313 andand 1515 havhavee beenbeen transposed.transposed. a combinedcombined issueissue willwill appearappear inin September/OctoberSeptember/October OnOn p.30p.3099 aboveabove,, iinn first columncolumn,, linlinee 27,27, forfor '1983-1985'1983 - 1985'' reareadd '1983'1983-1984' - 1984' .

ADVERTISINGADVERTISING IINN RatesRates peperr insertioninsertion,, excludingexcluding THETHE JOURNALJOURNAL OOFF VAT,VAT, areare asas follows:follows: GEMMOLOGYGEMMOLOGY WholWholee pagpagee £180£180 HalHalff pagpagee £100£100 ThThee EditorsEditors of theJournalthe Journal invitinvitee QuarterQuarter pagpagee £60£60 advertisementsadvertisements fromfrom gemstonegemstone andand mineraminerall dealersdealers,, scientificscientific EnquirieEnquiriess ttoo MrMrss M.M. Burland,Burland, instrumeninstrumentt makers,makers, publisherspublishers AdvertisinAdvertisingg Manager,Manager, andand othersothers witwithh interestsinterests inin thethe GemmologicalGemmological Association,Association, gemmological,gemmological, mineralogical,mineralogical, SaintSaint Dunstan'Dunstan'ss House,House, lapidarylapidary andand jewellerjewelleryy fields. CareyCarey Lane,Lane, LondoLondonn EC2EC2VV 8AB8AB.. JJ.. Gemm.Gemm.,, 19871987,20,6, 20, 6 393933

~neSiS 'enesis Britain'Britain'ss LeadinLeadingg ** LeaderLeaderss iinn gemmologicagemmological l educationeducation, , spespecializincializingg iinn intensivintensivee tuitiontuition, , frofromm scratcscratchh ttoo F.G.AF.G.A.. DiplomDiplomaa iinn ninninee monthsmonths. . WWecanclaime can claim aa ververyy DiamonDiamondd MerchanMerchantt highighh levelevell ooff passe passess includinincludingg DistinctionDistinctionss amongsamongstt ouourr studentsstudents.. ** WWee organizorganizee a comprehensivcomprehensivee programmprogrammee ooff StudStudyy TourTourss fofi,rr ththee studenstudent t anandd practisinpractising sincsincee 18718722 gemmologistgemmologist, , ttoo areaareass ooff gemmologica gemmological l interestinterest,, includinincludingg AntwerpAn twerp,, Idar-ObersteinIdar·Oberstein,, SrSrii Lankaa anandd BangkokBangkok.. ** Dealerss iinn gemstonegemstoness anandd rarraree specimenspecimenss foforr bothothh ththee studenstudentt anandd ththe cocollectorllector.. ** Supplierss off gemmologicagemmologicall instruments, especiallespeciallyy ththe worlworldd famoufamouss OPOPLL diffractiondiffraction gratingratingg spectroscopespectroscope,, togethetogetherr witwithh a rangrangee ooff bookbookss anandd studstudyy aidsaids.. F oror furtherfurther detailsdecails ofo( these these and otherOIher activities,aoivities, pleaseplease contact:-concaCl:- ColiColinn WinterWinter,, F.G.A.F.G.A.,, oorr HilarHilaryy TaylorTaylor,, B.A.B.A.,, F.G.A.F .G .A.,, aatt GENESISGENESIS,, 2211 WesWestt Street,, Epsom,Epsom, SurreSurreyy KT1KT188 7RL7RL,, England.England. TelTel:: EpsoEpsomm (03727(03727)) 42974.42974. TelexTelex:: 923499234922 TRFRTRFRTT G attattnn GENGENSS..

ATTENTION:ATTENTION: Museums,Museums, EducationalEducational DIAMONDSDIAMONDS EstablishmentsEstablishments andand 'CollectorsCollectors II havehave whatwhat isis probablyprobably thethe tefilÖN&r'PHONE FREEFREE. largestlargest rangerange ofof genuinelygenuinely rarerare gemstonesgemstones (including(including 0800 28-94-2828-94-28 synthetics)synthetics) inin thethe UK.UK. . . ~ . and ask for ~, .fo r ListList availableavailable (large(large s.a.e.s.a.e. appreciated)appreciated) JOANNA HARDY F.G.A. A.A. J.J. FRENCH.F.G.A.FRENCH.F.G.A. I'i • -•jtsV.t'i^-jW-.-'-ï/i-Vv«-. ..•.••:.„,:•. -. -, . GemGem DealerDealer andand ConsultantConsultant J~ 8282BrookleyRoad Brookley Road ,, C:: GINDER LTD Brockenhurst,Brockenhurst, HantsHants 5042S042 7RA7RA 44 Hatton Garden Telephone:Telephone: 059023214059023214 '^44Ältön Garden • 394 J. Gemm., 1987, 20,

We look after ajl your insurance PROBLEMS For nearly a century T. H. March has built an whether it be home, car, boat or pension plan. outstanding reputation by helping people in business. We would be pleased to give advice and As Lloyds brokers we can offer specially tailored quotations for all your needs and delighted to visit policies for the retail, wholesale, manufacturing and your premises if required for this purpose, without allied jewellery trades. Not only can we help you with obligation. all aspects of your business insurance but we can For a free quotation ring Mike Ward or Jim Pitman also take care of all your other insurance problems, on 01-6061282.

T. H. March and Co. Ltd. Saint Dunstan's House, Carey Lane, London EC2V 8AD. Telephone 01 -606 1282 & Lloyd's Insurance Brokers J. Gemm., 1987, 20, 6 395

NEW from the Natural History Museum Gemstones by R.R. Harding & CM. Woodward A concise and colourful introduction to the fascinating world of gemstones with sections on gem cutting, mining, gems in jewellery and descriptions of many species. All illustrations are taken from the collection at the Geological Museum. May 1987.64pp, full colour illustrations on each page. Pbk. 0 565 010115 £3.95 Minerals of Cornwall & Devon by P. G. Embrey & R. F. Symes The history of mining in south-west England goes back at least 3,500 years. The economic importance of the minerals mined has tended to overshadow their beauty. In this book, 80 specimens are illustrated in colour accompanied by descriptions of their crystallographic features. June 1987.120pp, 80 colour plates, 30 figs. Hbk. 0565 00989 3 £9.95 Available from booksellers or direct from : Sales Dept., Natural History Museum Publications, Cromwell Road, London SW75BD. Please add 10% of price (P & P) to your remittance. A free catalogue of all our publications is available on request.

PRACTICAL VL GEM IDENTIFICATION COURSES r ^^^^*^^ II Residential courses, devised by m >^ II Mr Alan Hodgkinson, FGA, and sponsored by the Retail Jeweller, to be held at the : British Horological Institute, Upton Hall, %gf Newark, Notts. Guest lecturers include Mr P.J.E. Daly, Mr A.D. Morgan and Dealers in Dr J.B. Nelson. Two day the gem stones of Introductory Course the world 28 and 29 September Designed for first year gemmology students and those interested in learning the basic Diamonds, Rubies, II techniques of gem testing and identification. Sapphires, Emeralds, and II Three day most coloured gem stones II Advanced Course Pearls & Synthetics. I 30 September, 1 and 2 October A practical refresher and update for qualified gemmologists, and a preparatory course for R.M.Weare second year gemmology students. & Company Limited. II 67 The Mount York. England. Y02 2AX. II Details from Carole Moore, Retail Jeweller, Telephone 0904-2I984. Telex: 57697 Yorvex.C II 100 Avenue Road, London NW3 3TP. Telephone: 01-935 6611. L * 396 J. Gemm., 1987, 20, 6

^ 4># O« THE RAYNER VERSALITE ^ •••••••••••••••••••it** %. An easy-to-use low cost multi-function light source ideal for a wide range of gem testing equipment. By simply using the 100W quartz-halogen fibre optic light guide in conjunction with your existing gem identification equipment, you will maximize your gemmological knowledge and carry out more accurate and positive gem identification.

SPECIAL FEATURES INCLUDE:

* Variable light intensity * Transmitted and overhead illumination facility * Semi-rigid fibre optic * Ease of light manoeuvrability * Useful for most refractometers, spectroscopes and dichroscopes * Optional microscope attachment * Pin pointer and monochromatic filter * Well presented, yet sturdy design •*••••••••

(Refractometer, spectroscope, dichroscope and microscope optional extras)

This unit is ideal for the professional and non professional gemmologist/jeweller alike and is available at a special price to Gemmological Association members. Normal Price £445.50 SPECIAL OFFER PRICE £295.00!!

To order contact: Doreen Walker, Gemmological Instruments Limited, Saint Dunstan's House, Carey Lane, London EC2V 8AB. Tel: 01 -726 4374

UK customers should add £48.30 postage and VAT **+ Overseas customers will be sent a pro forma invoice ^ Credit/charge card payments will be accepted for both # •\ UK and overseas orders. r^ J. Gemm., 1987, 20, 6 397

SRI LANKAN GEMSTONES All varieties in calibrated and uncalibrated sizes, single stones or lots at realistic prices. Be Dealers in convinced of what others already know. Finest untreated blue sapphire, ruby, pink, yellow and fancy sapphire, chrysoberyl, Emeralds hessonite, rhodolite and other garnets, moonstone, spinel, silver topaz, tourmaline, Sapphires zircon, quartz varieties, idocrase, fluorite, epidote, aquamarine, apatite, axinite, diopside, enstatite, scheelite, rutile, andalusite, taaffeite, Rubies sinhalite, scapolite, kornerupine, iolite, danburite, ekanite, fibrolite. Diamonds Cat's-eyes and stars of most of the above species, collector sets, colour suites, crystal specimens, study specimens and cabochons, available to suit your needs. Buying by mail from the experts at source is most economical. A. Freeman You will be pleasantly surprised at what we offer (Precious Stones) Ltd. and our prompt service. 26-27 Hatton Garden, D.F.Jayakody,FGA, London EClN 8BR 8 Batagama North, Telephone: 01-242 6564 and JA-ELA, 01-242 4847 Sri Lanka

AN EXCITING NEW OPPORTUNITY IN GEMM0L0GICAL EDUCATION

The Gemmological Association has launched a whole new programme of short practical courses in gemmology.

The one-day courses, organized in collaboration with the Gem Testing Laboratory of Great Britain, have been designed to give students practice in gem identification under the guidance of experts and to update qualified gemmologists' knowledge. Further details are published on page 338 in this issue. To book for the courses, please use the coupon below and enclose the necessary remittance.

To: Paula Jennings, Gemmological Association of Great Britain, Saint Dunstan's House, Carey Lane, London EC2V 8AB Please reserve place(s) for the course to be held on (Date). Enclosed is my remittance for £ The fee is £55 plus VAT (i.e. £63.25) per person, per course. NAME ADDRESS

Please use BLOCK LETTERS 398 J. Gemm., 1987, 20, 6

LABORATORY SERVICES

• Coloured stone identification • Pearl testing • Diamond grading • Coloured diamond verification • Educational courses • Professional consultancy

Find out more by telephoning 01-405-3351 or write for details to: GEM TESTING LABORATORY OF GREAT BRITAIN 27 GREVILLE STREET, LONDON EC IN 8SU

Have you a worn prism? Arrangements have now been made to LJvtiàtopiWi cA. K^aAeu, F.G.A. offer a speedy repair/overhaul service for Rayner refractometers*. Dealer in fine, rare and collectors' So if your refractometer glass prism is gemstones, carvings and mineral cracked, chipped or marked, or the specimens. refractometer just is not operating satisfactorily, simply send it to Specialist supplier of jade, from the Gemmological Association for archaic nephrite to imperial jadeite. overhaul. This will include completely stripping the unit down, checking and Valuations of collections and of replacing, if necessary, damaged internal individual items undertaken. lens system parts, replacing the top glass prism with a harder glass and generally I wish to purchase gem and mineral cleaning and realigning optics to collections, engraved gemstones ensure many more years of use. (especially intaglios) and old books The cost is j ust £51.00 plus postage and on gem related subjects. VAT where applicable. Christopher R. Cavey, F.G.A. Gemmological Association of Telephone: 01-575 2873 Great Britain, Saint Dunstan's House, Or write to Box No. GA1669, Carey Lane, London EC2V 8AB. Gemmological Association, * Please note that it is not possible to repair some of the old 'black style' refractometers as they are now obsolete. Saint Dunstan's House, Carey Lane, London EC2V 8AB. J. Gemm., 1987, 20, 6 399

ROCKMIN LIMITED

Dealers in all fine precious gems ton es.

63-66 Hatton Garden, London EC1N 8LE Telephone: 01-242 5586 Telex: 263042 Gemrox G. é 400 J. Gemm., 1987, 20, 6

GEMMOLOGICAL ASSOCIATION OF GREAT BRITAIN Saint Dunstan's House, Carey Lane, London EC2V 8AB. Telephone: 01-726 4374 Cables: Geminst, London EC2

Gem testing instruments, manufactured by the Rayner Optical Company and other international suppliers, are available from the Gemmological Association of Great Britain. Enquiries may be made direct to the Association or to officially appointed stockists throughout the world, a list of which is given below. United Kingdom Italy The Gem Testing Laboratory of Great Britain, Fraul, srl, Mr. Luciano Dezulian, 27 Greville Street, London EC1N 8SU. Via Marmolaia 14, 1-38033 Cavalese TN. Jewellery Valuation Services, 84-86 Comiston Gianfranco Lenti, Via Mazzini 10, Road, Edinburgh, Lothian EH10 5QJ. 15048 Valenza PO. Rubin & Son (UK) Ltd., 18 Greville Street, Japan London EC1N 8SQ. Gemmological Association of All Japan, H. S. Walsh & Sons Ltd., 243 Beckenham Tokyo Bihokaikan Bldg., 1-24 Akashi-cho, Road, Beckenham, Kent BR3 4TS. Chuo-ku, Tokyo 104. Australia Gemmological Association of Japan, Ladybird Gem Merchants, Shop 112, Kaneku Building, 3-27-11 Yushima, Second Gallery, The Strand Arcade, Sydney, Bunkyo-ku, Tokyo 113. NSW 2000. Norway Austria J. E. Aaby, A/S Kirkegt 15, Oslo 1. Josef Felber, Siebensterngasse 30, Postfach 5, Spain A1071 Wien. A. Santiago, Calle de la Rosa No. 10, Belgium 38002 Santa Cruz de Tenerife, Canary Islands. Rubin & Son pvba, Rubin House, Sweden Pelikaanstraat 94-96, B-2018, Antwerp. Thure Detter, Sodergatan 26, P.O. Box 4197, Canada 203 13 Malmo. W. Donald Goodger, 30 Evermede Drive, Switzerland Don Mills, Ont. M3A 2S3. Gübelin SA, Schweizerhof quai 1, Finland Denkmalstrasse 2, 6006 Lucerne. Ms. Anu Heiskanen, Gemmological Society of Pierre Misteli, 18 Rue du Marche, (Terraillet), Finland, c/o Kellomiehet Oy, Aleksanterinkatu CH-1204, Geneve. 48A, SF-00100 Helsinki. Thailand France Asian Institute of Gemmological Sciences, Gemodiam, 43 Rue Volta, 75003 Paris. P.O. Box 2714,987 Silom Road, Rama Jeweller Bldg, 5th Floor, Bangkok 5. Germany Eickhorst & Co., Hans Henny Jahn-Weg 21, USA D-2000 Hamburg 76. Gem Instruments Corporation, 1660 Stewart Gemphot GmbH, Postfach 01, D.8702 Street, P.O. Box 2147, Santa Monica, Uettingen. CA 90406. A. Kruss, Postfach 605 265, Mrs Dorothy Gibson, Arcus Gern Services, D-2000 Hamburg 60. P.O. Box 253, Chatham, NJ 07928. E. Gunter Wild, Bismarckstrasse 64, Hanneman Lapidary Specialities, Postfach 2713, 658 Idar Oberstein 2. P.O. Box 2453, Castro Valley, CA 94546. I. Kassoy Inc., Diamond Club Bldg, Hong Kong Mrs Kitty Wong, NuSovereign Co., Room 603, 30 West 47th Street, New York, NY 10036. Mongkok Commercial Centre, 16 Argyle Street, Wards Natural Science Establishment, Kowloon. P.O. Box 92912, Rochester, NY 14692-9012. Any company or individual interested in commencing an Agency should contact Bill Pluckrose at the Gemmological Association. GEMMOLOGICAL ASSOCIATION OF GREAT BRITAIN

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

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

Notes for Contributors The Editors are glad to consider original is consistent wi th clear indication of the articles shedding new light on subjects of content of the paper. It should be followed by gemmological interest for publication in the the names (with initials) of the authors and by Journal. Articles are not normally accepted their addresses. A short abstract of 50-100 which have already been published elsewhere words should be provided. Papers may be of in English, and an article is accepted only on any length, but long papers of more than the understanding that (1) full information as 10 000 words (unless capable of division into to any previous puJ"lication (whether in parts or of exceptional importance) are English or another language) has been given, unlikely to be acceptable, whereas a short (2) it is not under consideration for publication paper of 400-500 words may achieve early elsewhere and (3) it will not be published publication. elsewhere withou t the consent of the Editors. Twen ty five copies of individual papers are Papers should be submitted in duplicate on provided on request free of charge; additional A4 paper. They should be typed with double copies may be supplied, but they must be line spacing with ample margins of at least ordered at first proof stage or earlier. 25rrun all round. The title should be as brief as Volume 20 No. 6 April 1987

1 lK Journal of Gemmology

Contents

Damage to cut diamonds H.A. Hänni and G. Bosshart 339

Confusing colourless stones D. Kent 344

Investigation of a sapphire cat's-eye

from Burma K, Schmelzer and L. Kiefert 346

On the colour of gemstones and Nelson's 'body colour' K. Nassau 350

The two-colour beryl from Orissa, India R. Aliprandi andG. Guidi 352

Notes from the Laboratory-10 K. Scarratt 356

Colour and irradiation-induced defects in topaz treated with high-energy electrons K. Schmelzer 362 Sapphirine (not sapphire) in a ruby from Bo Rai, Thailand J J. Koivula andC .W. Fryer 369

Diaspore, a rare faceted gem J ,M. Duroc-Danner 371

Some colour variation in Jadeite C.R. Cavey 376

On the inclusions in emeralds from Santa Terezinha de Goiâs,

Brazil T. Miyatay M. Hosaka and A. Chikayama ill

Gemmological abstracts 380

Book reviews 386

Proceedings of the Gemmological Association of Great Britain and Association Notices 388 Copyright© 1987 Gemmological Association of Great Britain Registered Office: Saint Dunstan's House, Carey Lane, London EC2V 8AB

ISSN: 0022-1252

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