DOCSLIB.ORG

Volume 22 / No. 8 / 1991

Total Page：16

File Type：pdf, Size：1020Kb

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

Recommended publications
  • Phase Equilibria and Thermodynamic Properties of Minerals in the Beo
    American Mineralogist, Volwne 71, pages 277-300, 1986 Phaseequilibria and thermodynamic properties of mineralsin the BeO-AlrO3-SiO2-H2O(BASH) system,with petrologicapplications Mlnx D. B.qnroN Department of Earth and SpaceSciences, University of California, Los Angeles,Los Angeles,California 90024 Ansrru,cr The phase relations and thermodynamic properties of behoite (Be(OH)r), bertrandite (BeoSirOr(OH)J, beryl (BerAlrSiuO,r),bromellite (BeO), chrysoberyl (BeAl,Oo), euclase (BeAlSiOo(OH)),and phenakite (BerSiOo)have been quantitatively evaluatedfrom a com- bination of new phase-equilibrium, solubility, calorimetric, and volumetric measurements and with data from the literature. The resulting thermodynamic model is consistentwith natural low-variance assemblagesand can be used to interpret many beryllium-mineral occurTences. Reversedhigh-pressure solid-media experimentslocated the positions of four reactions: BerAlrSiuO,,: BeAlrOo * BerSiOo+ 5SiO, (dry) 20BeAlSiOo(OH): 3BerAlrsi6or8+ TBeAlrOo+ 2BerSiOn+ l0HrO 4BeAlSiOo(OH)+ 2SiOr: BerAlrSiuO,,+ BeAlrOo+ 2H2O BerAlrSiuO,,+ 2AlrSiOs : 3BeAlrOa + 8SiO, (water saturated). Aqueous silica concentrationswere determined by reversedexperiments at I kbar for the following sevenreactions: 2BeO + H4SiO4: BerSiOo+ 2H2O 4BeO + 2HoSiOo: BeoSirO'(OH),+ 3HrO BeAlrOo* BerSiOo+ 5H4Sio4: Be3AlrSiuOr8+ loHro 3BeAlrOo+ 8H4SiO4: BerAlrSiuOrs+ 2AlrSiO5+ l6HrO 3BerSiOo+ 2AlrSiO5+ 7H4SiO4: 2BerAlrSiuOr8+ l4H2o aBeAlsioloH) + Bersio4 + 7H4sio4:2BerAlrsiuors + 14Hro 2BeAlrOo+ BerSiOo+ 3H4SiOo: 4BeAlSiOr(OH)+ 4HrO.
    [Show full text]
  • Rhodochrosite Gems Unstable Colouration of Padparadscha-Like
    Volume 36 / No. 4 / 2018 Effect of Blue Fluorescence on the Colour Appearance of Diamonds Rhodochrosite Gems The Hope Diamond Unstable Colouration of in London Padparadscha-like Sapphires Volume 36 / No. 4 / 2018 Cover photo: Rhodochrosite is prized as both mineral specimens and faceted stones, which are represented here by ‘The Snail’ (5.5 × 8.6 cm, COLUMNS from N’Chwaning, South Africa) and a 40.14 ct square-cut gemstone from the Sweet Home mine, Colorado, USA. For more on rhodochrosite, see What’s New 275 the article on pp. 332–345 of this issue. Specimens courtesy of Bill Larson J-Smart | SciAps Handheld (Pala International/The Collector, Fallbrook, California, USA); photo by LIBS Unit | SYNTHdetect XL | Ben DeCamp. Bursztynisko, The Amber Magazine | CIBJO 2018 Special Reports | De Beers Diamond ARTICLES Insight Report 2018 | Diamonds — Source to Use 2018 The Effect of Blue Fluorescence on the Colour 298 Proceedings | Gem Testing Appearance of Round-Brilliant-Cut Diamonds Laboratory (Jaipur, India) By Marleen Bouman, Ans Anthonis, John Chapman, Newsletter | IMA List of Gem Stefan Smans and Katrien De Corte Materials Updated | Journal of Jewellery Research | ‘The Curse Out of the Blue: The Hope Diamond in London 316 of the Hope Diamond’ Podcast | By Jack M. Ogden New Diamond Museum in Antwerp Rhodochrosite Gems: Properties and Provenance 332 278 By J. C. (Hanco) Zwaan, Regina Mertz-Kraus, Nathan D. Renfro, Shane F. McClure and Brendan M. Laurs Unstable Colouration of Padparadscha-like Sapphires 346 By Michael S. Krzemnicki, Alexander Klumb and Judith Braun 323 333 © DIVA, Antwerp Home of Diamonds Gem Notes 280 W.
    [Show full text]
  • Mineralogy and Geochemistry of Nephrite Jade from Yinggelike Deposit, Altyn Tagh (Xinjiang, NW China)
    minerals Article Mineralogy and Geochemistry of Nephrite Jade from Yinggelike Deposit, Altyn Tagh (Xinjiang, NW China) Ying Jiang 1, Guanghai Shi 1,* , Liguo Xu 2 and Xinling Li 3 1 State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China; [email protected] 2 Geological Museum of China, Beijing 100034, China; [email protected] 3 Xinjiang Uygur Autonomous Region Product Quality Supervision and Inspection Institute, Xinjiang 830004, China; [email protected] * Correspondence: [email protected]; Tel.: +86-010-8232-1836 Received: 6 April 2020; Accepted: 6 May 2020; Published: 8 May 2020 Abstract: The historic Yinggelike nephrite jade deposit in the Altyn Tagh Mountains (Xinjiang, NW China) is renowned for its gem-quality nephrite with its characteristic light-yellow to greenish-yellow hue. Despite the extraordinary gemological quality and commercial significance of the Yinggelike nephrite, little work has been done on this nephrite deposit, due to its geographic remoteness and inaccessibility. This contribution presents the first systematic mineralogical and geochemical studies on the Yinggelike nephrite deposit. Electron probe microanalysis, X-ray fluorescence (XRF) spectrometry, inductively coupled plasma mass spectrometry (ICP-MS) and isotope ratio mass spectrometry were used to measure the mineralogy, bulk-rock chemistry and stable (O and H) isotopes characteristics of samples from Yinggelike. Field investigation shows that the Yinggelike nephrite orebody occurs in the dolomitic marble near the intruding granitoids. Petrographic studies and EMPA data indicate that the nephrite is mainly composed of fine-grained tremolite, with accessory pargasite, diopside, epidote, allanite, prehnite, andesine, titanite, zircon, and calcite. Geochemical studies show that all nephrite samples have low bulk-rock Fe/(Fe + Mg) values (0.02–0.05), as well as low Cr (0.81–34.68 ppm), Co (1.10–2.91 ppm), and Ni (0.52–20.15 ppm) contents.
    [Show full text]
  • Ajoite: New Data
    American Mineralogist, Volume 66, pages 201-203, 1981 Ajoite: new data GEORGE Y. CHAO Department of Geology, Carleton University Ottawa, Ontario Kl S 5B6, Canada Abstract New data show that ajoite is triclinic, PI or pI, a ==13.637, b ==14.507, c ==13.620A, a == 107.16, f3 = 105.45, y = 110.57°; Z ==3. The mineral is biaxial positive, 2V ==80°, a ==1.550, f3 = 1.583, y = 1.641 (in Na light); pleochroic: X = very light bluish green, Y -- Z ==brilliant bluish green. {010} cleavage is perfect. The orientation of the principal vibration directions is defined by the spherical coordinates X(26.5°, 80°), Y(118°, 79°), Z(-104.5°, 15°). The ex- tinction angle c: Z' on (0 I0) is 150. Electron microprobe and chemical analyses gave Si02 41.2, Al203 3.81, CuO 42.2, MnO 0.02, FeO 0.11, CaO 0.04, Na20 0.84, K20 2.50, H20 (TGA to 1000°C) 8.35, sum 99.07 wt.%. The analysis corresponds to (Ko.70NaO.36Cao.Ol)(CUt,.97 Feo.o2)Alo.98Si9.oo024(OH)6'3.09H20 or ideally, (K,Na)Cu7AISi9024(OH)6' 3H20. TGA showed a two-stage dehydration; 50% of the total water was released between 70° and 425°C and the rest between 4250 and 800°C. Half of the water is zeolitic in nature. Introduction are always present. The termination on c may be ei- Ajoite, first described by Schaller and Vlisidis ther {001} or {203} or both. (1958) from Ajo, Pima County, Arizona, was thought to be monoclinic on the basis of optical studies.
    [Show full text]
  • Shear Zone Initiation in the Marcy Anorthosite Massif, Adirondacks, New York, USA James Hodge University of Maine, [email protected]
    The University of Maine DigitalCommons@UMaine Electronic Theses and Dissertations Fogler Library Summer 8-23-2019 Fractures, Fluids, and Metamorphism: Shear Zone Initiation in the Marcy Anorthosite Massif, Adirondacks, New York, USA James Hodge University of Maine, [email protected] Follow this and additional works at: https://digitalcommons.library.umaine.edu/etd Part of the Geochemistry Commons, Geology Commons, and the Tectonics and Structure Commons Recommended Citation Hodge, James, "Fractures, Fluids, and Metamorphism: Shear Zone Initiation in the Marcy Anorthosite Massif, Adirondacks, New York, USA" (2019). Electronic Theses and Dissertations. 3050. https://digitalcommons.library.umaine.edu/etd/3050 This Open-Access Thesis is brought to you for free and open access by DigitalCommons@UMaine. It has been accepted for inclusion in Electronic Theses and Dissertations by an authorized administrator of DigitalCommons@UMaine. For more information, please contact [email protected]. FRACTURES, FLUIDS, AND METAMORPHISM: SHEAR ZONE INITIATION IN THE MARCY ANORTHOSITE MASSIF, ADIRONDACKS, NEW YORK, USA By James Hodge B.S. College of Saint Rose, 2017 A Thesis Submitted in Partial Fulfillment of the Requirements for the Degree of Master of Science (in Earth and Climate Sciences) The Graduate School The University of Maine August 2019 Advisory Committee: Scott Johnson, Professor and Director School of Earth and Climate Sciences, Advisor Chris Gerbi, Professor School of Earth and Climate Sciences, Advisor Alicia Cruz-Uribe, Professor School of Earth and Climate Sciences Martin Yates, Professor School of Earth and Climate Sciences FRACTURES, FLUIDS, AND METAMORPHISM: SHEAR ZONE INITIATION IN THE MARCY ANORTHOSITE MASSIF, ADIRONDACKS, NEW YORK, USA By James Hodge Thesis Advisors: Dr.
    [Show full text]
  • High-Pressure Crystal Chemistry of Beryl (Beralrsi.Otr) and Euclase
    American Mineralogist, Volume 71, pages 977-984, 1986 High-pressurecrystal chemistry of beryl (BerAlrSi.Otr) and euclase(BeAlSiO4OH) Rosnnr M. HaznN, ANonpw Y. Au, Llnnv W. FrNcnn GeophysicalLaboratory, CarnegieInstitution of Washington, 2801 Upton Street,N.W., Washington, D.C. 20008 Ansrnlcr Compressibilities and high-pressurecrystal structures of beryl and euclasehave beon determined by X-ray methods at severalpressures. Beryl (hexagonal,space group P6/mcc) has nearly isotropic compressibility; linear compressibilitiesperpendicular and parallel to the c axis ateB':1.72 + 0.04 x l0-a kbar-'and B,:2.10 + 0.09 x 10-akbar-'. The correspondingbulk modulus is 1.70 + 0.05 Mbar if the pressurederivative of the bulk modulus K'is assumedto be 4. Euclase(monoclinic, spacegroup P2r/a)has anisotropic compression,with maximum compressibrlity of 2.44 + 0.05 x l0-a kbar-l parallel to the unique monoclinic b axis, and minimum compressibility of 1.50 + 0.03 x 10-a kbar-' approximately parallel to [01]. The intermediate axis of compressionhas a magnitude of 1.96 + 0.05 x lO-akbar-'in the a-c plane.The bulk modulus of euclaseis 1.59 t 0.03 Mbar if K' is assumedto be 4. The bulk moduli ofBe, Al, and Si cation coordination polyhedrain beryl are all consistent with 1.7 Mbar, which is the crystal bulk modulus. Beryl compressionoccurs primarily by shorteningof cation-anion bond distances.In euclase,the 2.3-Mbar polyhedralbulk moduli are significantly greater than the observed 1.6-Mbar crystal modulus. Compression in euclase,particularly along the b crystallographicaxis, results from a combination of poly- hedral compressionand changesin interpolyhedral angles.
    [Show full text]
  • Gemmologythe Journal of Volume 28 No.7 July 2003
    ^ GemmologyThe Journal of Volume 28 No.7 July 2003 The Gemmological Association and Gem Testing Laboratory of Great Britain ~ ~. ~ Gemmological Association , ~ '.~ , and Gem Testing Laboratory ~, :~ of Great Britain • 27 Greville Street, London ECIN 8TN Tel: +44 (0)20 7404 3334 Fax: +44 (0)20 7404 8843 e-mail: [email protected] Website: www.gem-a.info President: Professor A.T Collins Vice-Presidents: N. W. Deeks, A.E. Farn, RA Howie, D.G. Kent, RK. Mitchell Honorary Fellows: Chen Zhonghui, RA Howie, K. Nassau Honorary Life Members: H . Bank, D.J. Ca llaghan, E.A [obbins, H . Tillander Council of Management: T J. Davidson, RR Harding, I. Mercer, J. Monnickendam, M.J. 0'Donoghue, E. Stern, I. Thomson, Y.P. Watson Members' Council: A J. Allnutt, S. Burgoyne, P. Dwyer-Hickey, S.A Everitt, J. Greatwood, B. Jackson, L. Music, J.B. Nelson, P.J. Wates, CH. Winter Branch Chairmen: Midlands -G.M. Green, North West -D. M. Brady, Scottish - B. Jackson, South Eas t - CH. Winter, South West - RM. Slater Examiners: A J. Allnutt, M.5e., Ph.D., FGA, L. Bartlett, B.5e., M.Ph il., FGA, DGA, S. Coelho, BS e., FGA, DGA, Prof. AT Co llins, BSe., Ph.D, A.G. Good, FGA, DGA, J. Greatwood, FGA, S. Greatwood, FGA, DGA, G.M. Green, FGA, DGA, G.M. Howe, FGA, DGA, S. Hue Williams MA, FGA, DGA , B. Jackson, FGA, DGA, G.H. Jones, BSe., PhD., FGA, Li Li Ping, FGA, DGA, M.A Medniuk, FGA, DGA, M. Newton, BSe. , D.Phil., CJ.E. Oldershaw, BSe. (Hans), FGA, DGA, H.L.
    [Show full text]
  • Some Uncommon Sapphire “Imitations”: Blue Co-Zirconia, Kyanite & Blue Dumortierite Dr Michael S
    Some Uncommon Sapphire “Imitations”: Blue Co-zirconia, Kyanite & Blue Dumortierite Dr Michael S. Krzemnicki Swiss Gemmological Institute SSEF [email protected] 筆者滙報數個瑞士珠寶研究院(SSEF)近期收到 in the ring showed a negative RI reading 要求鑑證的藍色寶石，經檢測後確定其中包括 (above 1.79), an isotropic optical character 一些非常罕見的藍寶石模擬石：含錮氧化鋯、 (polariscope) and thus no pleochroism at all. 藍晶石及藍線石等。 Under the microscope, we saw no inclusions, however a slightly greenish reaction under Sapphires are among the most abundant gems the LWSW and there was a weaker similar we receive at the Swiss Gemmological Institute reaction under SWUV lamps. Based on these (SSEF) for testing. From time to time, however, properties and a chemical analysis by X-ray we are quite surprised by the imitations which fluorescence (EDXRF), the blue stone was we find among the goods sent in and this can readily identified as cubic zirconia (ZrO2). then be disappointing news for the clients. In Having seen this artificial product in a wide the following short note, the author presents a range of colours, the author had not previously few uncommon imitations identified recently at seen one of such a saturated and attractive the SSEF. Identification of these imitations is blue. Based on literature (Nassau 1981) the straightforward and should be no problem for analysed traces of cobalt in that stone have any experienced gemmologist. been identified as the colouring element in this specimen. The absorption spectrum of the stone The first case is that of an attractive blue (Fig. 2) – although superposed by several rare faceted stone of approximately 1.4 ct, set in a ring with diamonds (Fig.
    [Show full text]
  • HK Fancy Sapphire
    Hong Kong, March 2011 Fancy Coloured Sapphires: The Beauty beyond "Blue" of Sapphire and "Red" of Ruby Dr. Michael S. Krzemnicki Swiss Gemmological Institute SSEF Switzerland All photos © M.S. Krzemnicki, SSEF except where indicated. The range of colours... © Swiss Gemmological Institute SSEF 1 The range of colours... © Swiss Gemmological Institute SSEF The range of colours... © Swiss Gemmological Institute SSEF 2 The range of colours... © Swiss Gemmological Institute SSEF The range of colours... © Swiss Gemmological Institute SSEF 3 The range of colours... © Swiss Gemmological Institute SSEF The range of colours... © Swiss Gemmological Institute SSEF 4 The range of colours... © Swiss Gemmological Institute SSEF The range of colours... © Swiss Gemmological Institute SSEF 5 The range of colours... © Swiss Gemmological Institute SSEF The range of colours... © Swiss Gemmological Institute SSEF 6 The range of colours... © Swiss Gemmological Institute SSEF The range of colours... © Swiss Gemmological Institute SSEF 7 The range of colours... © Swiss Gemmological Institute SSEF The range of colours... © Swiss Gemmological Institute SSEF 8 The range of colours... © Swiss Gemmological Institute SSEF The range of colours... Fancy sapphires: The colour range beyond red of rubies and blue of sapphires © Swiss Gemmological Institute SSEF 9 The range of colours... Photo: © SilkenEast Ltd, Bangkok © Swiss Gemmological Institute SSEF The range of colours... Collection: SilkenEast Ltd, Bangkok © Swiss Gemmological Institute SSEF 10 Jewellery with fancy sapphires Photos © Luc Phan, SSEF © Swiss Gemmological Institute SSEF © Swiss Gemmological PhotoInstitute © Luc SSEF Phan, SSEF 11 Corundum Chemical composition: aluminium oxide, Al2O3 Chemical pure aluminium oxide is colourless © Wikipedia In nature always with trace elements (chemical impurities), usually: - Mg, Ti, V, Cr, Fe, Ga - and occasionally rare HFS-elements such as Nb, Sn, Ta, Th Not all trace elements are affecting the colour (e.g.
    [Show full text]
  • Wickenburgite Pb3caal2si10o27² 3H2O
    Wickenburgite Pb3CaAl2Si10O27 ² 3H2O c 2001 Mineral Data Publishing, version 1.2 ° Crystal Data: Hexagonal. Point Group: 6=m 2=m 2=m: Tabular holohedral crystals, dominated by 0001 and 1011 , to 1.5 mm. As spongy aggregates of small, highly perfect f g f g individuals; as subparallel aggregates or rosettes; granular. Physical Properties: Cleavage: 0001 , indistinct. Tenacity: Brittle but tough. Hardness = 5 D(meas.) = 3.85 D(cfalc.) g= 3.88 Fluoresces dull orange under SW UV. Optical Properties: Transparent to translucent. Color: Colorless to white; rarely salmon-pink. Luster: Vitreous. Optical Class: Uniaxial ({). Dispersion: r < v; moderate. ! = 1.692 ² = 1.648 Cell Data: Space Group: P 63=mmc: a = 8.53 c = 20.16 Z = 2 X-ray Powder Pattern: Near Wickenburg, Arizona, USA. 10.1 (100), 3.26 (80), 3.93 (60), 3.36 (40), 2.639 (40), 5.96 (30), 5.04 (30) Chemistry: (1) (2) SiO2 42.1 40.53 Al2O3 7.6 6.88 PbO 44.0 45.17 CaO 3.80 3.78 H2O 3.77 3.64 Total 101.27 100.00 (1) Near Wickenburg, Arizona, USA. (2) Pb3CaAl2Si10O24(OH)6: [needsnew??formula] Occurrence: In oxidized hydrothermal veins, carrying galena and sphalerite, in quartz and °uorite gangue (near Wickenburg, Arizona, USA). Association: Phoenicochroite, mimetite, cerussite, willemite, crocoite, duftite, hemihedrite, alamosite, melanotekite, luddenite, ajoite, shattuckite, vauquelinite, descloizite, laumontite. Distribution: In the USA, in Arizona, at several localities south of Wickenburg, Maricopa Co., including the Potter-Cramer property, Belmont Mountains, and the Moon Anchor mine; on dumps at a Pb-Ag-Cu prospect in the Artillery Peaks area, Mohave Co.; and in the Dives (Padre Kino) mine, Silver district, La Paz Co.
    [Show full text]
  • 38Th RMS Program Notes
    E.fu\wsoil 'og PROGRAM Thursday Evening, April 14, 2011 PM 4:00-6:00 Cocktails and Snacks – Hospitality Suite 400 (4th Floor) 6:00-7:45 Dinner – Baxter’s 8:00-9:15 THE GUALTERONI COLLECTION: A TIME CAPSULE FROM A CENTURY AGO – Dr. Renato Pagano In 1950, the honorary curator of the Museum of Natural History in Genoa first introduced Dr. Renato Pagano to mineral collecting as a Boy Scout. He has never looked back. He holds a doctorate in electrical engineering and had a distinguished career as an Italian industrialist. His passion for minerals has produced a collection of more than 13,000 specimens, with both systematic and aesthetic subcollections. His wife Adriana shares his passion for minerals and is his partner in collecting and curating. An excellent profile of Renato, Adriana, and their many collections appeared earlier this year in Mineralogical Record (42:41-52). Tonight Dr. Pagano will talk about an historic mineral collection assembled between 1861 and 1908 and recently acquired intact by the Museum of Natural History of Milan. We most warmly welcome Dr. Renato Pagano back to the speakers’ podium. 9:15 Cocktails and snacks in the Hospitality Suite on the 4th floor will be available throughout the rest of the evening. Dealers’ rooms will be open at this time. All of the dealers are located on the 4th floor. Friday Morning, April 15, 2011 AM 9:00 Announcements 9:15-10:15 CRACKING THE CODE OF PHLOGOPITE DEPOSITS IN QUÉBEC (PARKER MINE), MADAGASCAR (AMPANDANDRAVA) AND RUSSIA (KOVDOR) – Dr. Robert F. Martin Robert François Martin is an emeritus professor of geology at McGill University in Montreal.
    [Show full text]
  • Astrology & Gemstones 1
    Astrology & Gemstones A birthstone is a gem whose vibrarion harmonizes with a person’s sun sign. Although today we wear gems primarily for decorative purposes, our ances- tors chose gemstones to influence an individual’s astrological characteristics. Gems, they believed, could strengthen weaknesses or tone down ex- cesses in a person’s natal makeup. Don’t choose a birthstone based on the calendar month in which you were born, however––go by the astrological sign instead. Each sign straddles two months. Aquarius, for example, begins on about January 20 and ends around February 18. Astrologers consider the garnet Aquarius’s sign, but jewelers who don’t understand astrology usually link garnets with January and amethysts with February. Amethyst, astrologers argue, belongs to the zodiac sign Pisces. As you can see in the following lists, each planet and each sign relates to more than one gem. The correspondences are based on energetic proper- ties, colors, and other factors. Aries, a sign known for its aggressive and daring nature, is linked with bloodstone, a gem used by Roman soldiers for protection. Moonstone relates to the sign Cancer, which is ruled by the moon. Some stones may possess the qualities of more than one sign and there- fore have affinities with others, as is the case with aquamarine. Stones that come in many colors, such as agates, are usually associated with the planet(s) and signs(s) that govern their colors. Today, as in the past, we can use gemstones to attract things we desire and to repel or prevent things we don’t want to interfere in our lives.
    [Show full text]