Volume 23 No. 1. January 1992 The Journal of Gemmology THE GEMMOLOGICAL ASSOCIATION AND GEM TESTING LABORATORY OF GREAT BRITAIN OFFICERS AND COUNCIL Past Presidents: Sir Henry Miers, MA, D.Sc., FRS Sir William Bragg, OM, KBE, FRS Dr. G.F. Herbert Smith, CBE, MA, D.Sc. Sir Lawrence Bragg, CH, OBE, MC, B.Sc., FRS Sir Frank Claringbull, Ph.D., F.Inst.P., FGS Vice-President: R K. Mitchell, FGA Council of Management D.J. Callaghan, FGA C.R Cavey, FGA E.A. Jobbins, B.Sc., C.Eng., FIMM, FGA 1. Thomson, FGA V.P. Watson, FGA K. Scarratt, FGA RR Harding, B.Sc., D.Phil., FGA Members' Council A. J. Allnutt, M.Sc., G.H. Jones, B.Sc., Ph.D., FGA P. G. Read, C.Eng., Ph.D., FGA H. Levy, M.Sc., BA, FGA MIEE, MIERE, FGA P. J. E. Daly, B.Sc., FGA J. Kessler 1. Roberts, FGA T. Davidson, FGA G. Monnickendam E.A. Thomson, R Fuller, FGA L. Music Hon. FGA D. Inkersole, FGA J.B. Nelson, Ph.D., FGS, R Velden B. Jackson, FGA F. Inst. P., C.Phys., FGA D. Warren C.H. Winter, FGA Branch Chairmen: Midlands Branch: D.M. Larcher, FBHI, FGA North-West Branch: 1. Knight, FGA Examiners: A. J. Allnutt, M.Sc., Ph.D., FGA G. H. Jones, B.Sc., Ph.D., FGA L. Bartlett, B.Sc., M.Phil., FGA D. G. Kent, FGA E. M. Bruton, FGA P. Sadler, B.Sc., FGS, FGA C. R Cavey, FGA K. Scarratt, FGA A.T. Collins, B.Sc., Ph.D E. Stem, FGA A. E. Fam, FGA Prof. LSunagawa,D.Sc. R R Harding, B.Sc., D.Phil.; FGA M. Virkkunen, M.Phil., FGA E. A. Jobbins, B.Sc., C. Eng., FIMM, FGA C. Woodward, B.Sc., FGA Editor: E. A. Jobbins, B.Sc., C.Eng., FIMM, FGA Editorial Assistant: Mary A. Burland Curator: C. R Cavey, FGA The Genunological Association and Gem. Testing Laboratory of Great Britain 27 Greville Street, London EClN 8SU Telephone: 071-4043334 Fax: 071-4048843 The Journal of Gemmology VOLUME 23 NUMBER ONE JANUARY 1992 Cover Picture A synthetic diamond during electron bombardment. Symmetric arrangement of various growth sectors of greenish-yellow and blue clearly revealed. (See Cathodoluminescence (CL) and CL spectra of De Beers' experimental synthetic diamonds by Johann Ponahlo, p.3-17.) ISSN: 0022-1252 2 J. Gemm., 1992, 23, 1 R. Keith Mitchell, FGA It is fitting that as we introduce this He had assisted the late Thorold new volume of the Journal we honour Jones with practical classes at one of our eminent Fellows who Chelsea Polytechnic in 1947 and, celebrates his eightieth birthday on when Anderson gave up teaching January 28 1992. and Webster took over the practical Mr Mitchell joined the silver and instruction in 1949, moved on to leather-goods buying department of tutor first year students in the Mappin and Webb Ltd in 1928. Gemmological Association Geology and minerals had always Correspondence Courses. Within a fascinated him and he eventually year C.J. Payne opted out of the obtained a move to their gem Diploma course instruction and the department in 1933. late Gordon Andrews, the shrewd The previous year had been secretary of the Gemmological significant since he then joined the Association, asked Mr Mitchell to gemmology course under J.G. Jardine take both Courses over. He then at Chelsea Polytechnic. In 1934 he ran these single-handed until 1959 won the Tully Memorial Medal when Vera Hinton took on 100 of despite strong rivalry from Robert the first year students and then, a Webster and other students in what year or so later, the Rev. Nikon- had been a remarkable year - the first in the charge of Cooper also took over some of the first year people. B.W. Anderson - when nearly half the students who Mr Mitchell still coped with a substantial surplus of sat the examination achieved Distinction passes and no first year students and with the entire Diploma quota one failed. for twenty years (during which eight of his students He wrote occasionally for the Gemmologist and other gained Tully Medals), plus frequent revision of course journals until marriage in 1937, and the War two years notes to keep them in line with a rapidly advancing later, diverted his interests. subject, until 1969 when sudden illness forced him to 1936 had seen him working first for B. Barnett Ltd give up this work. One year he had found himself and then for A.E. Davis Ltd in London's Piccadilly, with a work-load of some 240 students, some of whom where he remained through the desperate period of the elected to write in their own languages rather than in London Blitz until call-up in 1941 sent him north to English. In 1979 he was once more asked to revise Catterick to train as an operator in the Royal Corps of the Course notes which had been allowed to become Signals. rather static in the ten years since he had retired as an Training completed he was shipped to Singapore, instructor. By the mid-eighties a veritable team of arriving ten days before Japan entered the war. Ten instructors had taken his place. weeks later Singapore fell and he was incarcerated with In business he continued to work from home until some fifty thousand other prisoners in the Changi area. insurance problems forced him to take an office in After 15 months and much ill-health he was shipped to Holborn in 1967, a happy move which was to prove Hokkaido, the northern island of Japan, to slave long very rewarding until he retired from active business in and hard under extremely arduous conditions on an 1979. But the habits of a lifetime die hard, and even insufficient diet of rice, levelling airfields, feeding steel today he still dabbles a little with gems and jewellery furnaces and mining coal. and undertakes some coaching when students ask. At the end of the 5War he came home to rejoin A.E. Always interested in writing, he has contributed Davis in Piccadilly and remained with that firm until some fifty papers of greater or lesser scientific 1957. A misguided appointment with a provincial importance to this and to other Journals both here and jeweller swiftly foundered and Mr Mitchell started overseas since the mid-thirties and compiled a set of dealing from home on his own account in July of that Gem Crystal Transparencies which assist the teaching year. of crystal recognition. Today he is perhaps best By this time his interest was largely in antique known for the numerous abstracts from foreign jewellery and in rare and unusual gems and over the magazines which have appeared over the initials years the writer, who had first met Keith Mitchell in R.K.M. for many years in our Journal, and for 1950, had, in his capacity as Curator of Gem and lamentably frequent obituaries of old friends. Mineral Collections at the Geological Museum, In April 1984, 50 years after acquiring his Tully acquired from him many outstanding and mouth- Medal, R. Keith Mitchell was elected Vice-President wateringly beautiful gems for those National of our Association - a well-deserved tribute and a collections. Some of these had come from contacts fitting reward for the very considerable service he has with over-seas students in the course of Keith's afforded to the Association for more than half a teaching activities. century. We wish him well for many years to come. JJ.. Gemm.Gemm.,, 19921992,, 2323,, 11 3 CathodoluminescencCathodoluminescencee (CL(CL)) anandd CCLL spectrspectraa ooff DeDe BeersBeers'' experimentaexperimentall synthetisyntheticc diamonddiamondss Johann Ponahlo,Ponahio, FGAFGA formerlformerlyy AustriaAustriann GemmologicaGemmologicall ResearcResearchh InstitutInstitutee (E.Ö.G.G.)(E.G.G.G.),, ViennaVienna,, AustriAustriaa 11.. IntroductionIntroduction systesystemm mamayy diffusdiffusee intintoo ththee vacuuvacuumm compartmentcompartment LargLargee man-madman-madee experimentaexperimentall diamonddiamondss havhavee anandd becombecomee absorbeabsorbedd oonn ththee surfacsurfacee ooff a samplesample beebeenn describedescribedd bbyy variouvariouss authorauthorss iinn ththee paspastt wherwheree thetheyy araree crackecrackedd bbyy ththee electroelectronn beambeam.. BByy (Crowningshiel(Crowningshieldd (1971)(1971),, KoivulKoivulaa et al. (1984)(1984),, placinplacingg a moleculamolecularr sievsievee betweebetweenn ththee pumpingpumping ShigleShigleyy et al. (1986(1986,, 1987))1987)).. TherTheree iiss nnoo doubt,doubt, systesystemm anandd ththee vacuuvacuumm compartmencompartmentt contamina­contamina­ anymoreanymore,, abouaboutt ththee technicatechnicall potentialitiepotentialitiess ttoo growgrow tiotionn cacann bbee avoidedavoided.. IfIf,, iinn rarraree instancesinstances,, a slightslight singlsinglee crystalcrystalss ooff diamonddiamondss uupp ttoo 20ct20ct.. TwTwoo yearyearss yelloyelloww ttoo browbrownn discoloratiodiscolorationn ooff a bombardedbombarded agoago,, bbyy courtescourtesyy ooff ththee DiamonDiamondd ResearcResearchh Labora­Labora­ diamondiamondd facefacett iiss observeobservedd ththee thithinn film mamayy easileasilyy torytory,, JohannesburgJohannesburg,, anandd ththee DTDTCC Laboratories,Laboratories, bbee removeremovedd usinusingg a polishinpolishingg agent.agent. 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