DOCSLIB.ORG

The Separation of Natural from Synthetic Colorless Sapphire

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
The Separation of Natural from Synthetic Colorless Sapphire THE SEPARATION OF NATURAL FROM SYNTHETIC COLORLESS SAPPHIRE By Shane Elen and Emmanuel Fritsch Greater amounts of colorless sapphire—promot- undreds of millions of carats of colorless syn- ed primarily as diamond substitutes, but also as thetic sapphire are manufactured annually (all natural gemstones—have been seen in the gem growth techniques combined), according to B. market during the past decade. In the absence of MudryH of Djevahirdjian in Monthey, Switzerland, a leading inclusions or readily identifiable growth struc- producer of Verneuil synthetics (pers. comm., 1997). He esti- tures, natural colorless sapphires can be separat- mates that about 5%–10% of this production (50–100 mil- ed from their synthetic counterparts by their lion carats) is used by the jewelry industry. Distinguishing trace-element composition and short-wave ultraviolet (SWUV) transparency. Energy-disper- natural from synthetic colorless sapphire can often, but not sive X-ray fluorescence (EDXRF) analysis shows always, be accomplished by standard gemological testing higher concentrations of trace elements (i.e., Fe, (see below). However, this distinction is time consuming for Ti, Ca, and Ga) in natural sapphires. These large parcels, and it is difficult to impossible for melee-size impurities cause a reduction in SWUV trans- stones. parency that can be detected by UV-visible spec- As first described more than 50 years ago (Wild and trophotometry (i.e., a total absorption in the UV Biegel, 1947), natural colorless corundum can be separated region below 280–300 nm, which is not seen in from flame-fusion synthetic colorless corundum (only their synthetic counterparts). This article Verneuil material was being produced at that time) by a dif- describes a SWUV transparency tester that can ference in transparency to short-wave ultraviolet (SWUV) rapidly identify parcels of colorless sapphires. radiation. The present study shows that the difference in SWUV transparency is a result of the difference in trace-ele- ment chemistry between natural and synthetic colorless ABOUT THE AUTHORS sapphire. We also demonstrate that SWUV transparency Mr. Elen ([email protected]) is a research gemologist testing is valid for Czochralski-grown synthetic colorless at GIA Research, Carlsbad, California, and Dr. sapphire, too. Therefore, this technique can help meet the Fritsch is professor of physics at Nantes need for a simple, cost-effective method to mass screen this University, France. relatively inexpensive gem material. The authors thank Sam Muhlmeister and Dino DeGhionno of the GIA Gem Trade Laboratory in Carlsbad for recording some of the EDXRF spec- BACKGROUND tra and measuring gemological properties, Natural Colorless Sapphire. Colorless sapphire is a relatively respectively. Some of the samples were loaned by Dave Ward of Optimagem, San Luis Obispo, pure form of aluminum oxide (Al2O3); it is often inaccurate- California; Michael Schramm of Michael ly called “white sapphire.” Truly colorless sapphire is quite Schramm Imports, Boulder, Colorado; and Shane uncommon, and most “colorless” sapphire is actually near- F. McClure of the GIA Gem Trade Laboratory in Carlsbad. Dr. James E. Shigley of GIA Research colorless, with traces of gray, yellow, brown, or blue. For the provided constructive review of the manuscript. purposes of this article, both colorless and near-colorless Gems & Gemology, Vol. 35, No. 1, pp. 30–41 sapphires will be referred to as “colorless.” The primary © 1999 Gemological Institute of America source for this material has been, and remains, Sri Lanka. Colorless sapphire was a common diamond simulant in 30 Colorless Sapphire GEMS & GEMOLOGY Spring 1999 Figure 1. Colorless sapphire con- tinues to be popular in jewelry, especially for items such as tennis bracelets, but also as single stones. The larger loose sapphire is 4.44 ct; the tennis bracelet con- tains a total weight of 4.33 ct; the stone in the pendant is 8.56 ct and the sapphire in the ring is 5.17 ct. Courtesy of Sapphire Gallery, Philipsburg, Montana; photo © Harold & Erica Van Pelt. the late 19th and early 20th centuries. In the early popular (“Demand strong for white sapphires,” 1970s, it first began to be used as an inexpensive 1996; M. Schramm, pers. comm., 1999), and has starting material for blue diffusion-treated sapphires fueled a market for synthetic colorless sapphire. (Kane et al., 1990). At around the same time, large quantities of colorless sapphire were heat treated to Synthetic Colorless Sapphire. Synthetic sapphire produce yellow sapphire (Keller, 1982). The demand has been produced by several growth techniques— for colorless sapphire increased significantly in the in particular, flux, hydrothermal, flame-fusion, and late 1980s to early 1990s. This was a result of the Czochralski. However, because of manufacturing greater interest in blue diffusion-treated sapphires costs, only two types of synthetic colorless sapphire (Koivula et al., 1992), and colorless sapphire’s are typically used as gems: flame-fusion (Verneuil, increasing popularity in jewelry as an affordable 1904) and Czochralski “pulled” (Rubin and Van alternative to diamond that could be used as melee, Uitert, 1966). Early in the 20th century, flame- for tennis bracelets, or attractively set as a center fusion synthetic colorless sapphire was the first syn- stone (Federman, 1994). thetic gem material to be used as a diamond simu- From 1993 through the first half of 1994, a lant (Nassau, 1980, p. 210). However, other synthet- steady demand for faceted colorless sapphire caused ic gem materials have since surpassed colorless syn- the per-carat price to almost double, to US$70 per thetic sapphire for this purpose because of the sig- carat retail (“White sapphire sales up 172%,” 1994). nificantly lower refractive index and dispersion of Colorless sapphire jewelry (figure 1) has remained corundum as compared to diamond. Colorless Sapphire GEMS & GEMOLOGY Spring 1999 31 melee-size sapphires may not exhibit any character- istic inclusions or growth structures. R.I. and S.G. values are of no help, as they are identical for syn- thetic and natural stones (Liddicoat, 1987, p. 338). Inclusions. Natural colorless sapphire contains the same distinctive inclusions encountered in other color varieties of corundum: silk (fine, needle-like rutile or boehmite crystals), groups of rutile needles intersecting in three directions at 60° to one anoth- er, zircon crystals surrounded by stress fractures, and well-defined “fingerprint” inclusions (figure 3) that consist of large networks of irregular fluid-filled cavities (Gübelin, 1942a and b, 1943; Kane, 1990). Two- and three-phase inclusions may be encoun- tered, as well as small crystals of spinel, uraninite, mica, pyrite, apatite, plagioclase, albite, and dolomite (Gübelin and Koivula, 1992; Schmetzer and Medenbach, 1988). Colorless synthetic sapphire may exhibit growth-induced inclusions, typically small gas bub- bles (figure 4) or unmelted aluminum oxide parti- Figure 2. These stones (0.32 ct to 3.08 ct) formed cles that occur individually, in strings, or in part of the sample set used in this study. The col- “clouds.” Gas bubbles may appear round or elongat- orless sapphires on the left are synthetic, and those on the right are natural. Photo © Tino ed in a flask or tadpole shape (figure 5). The gas bub- Hammid and GIA. bles may follow curved trajectories, allowing indi- rect observation of the curved striae that are other- wise invisible in colorless synthetic sapphire Early synthetic sapphire produced by the (Webster, 1994). Verneuil method often contained characteristic The irregularly shaped gas bubbles in synthetic growth defects, such as striations and inclusions. corundum could be mistaken for natural crystal These defects were unacceptable to the industrial inclusions with partially dissolved crystal faces. market, which required extremely high (“optical”) Occasionally, undissolved alumina may take on the quality synthetic sapphire. This led to the develop- appearance of a natural inclusion (Webster, 1994). ment of several new growth techniques, including As noted above, however, recent production tech- the Czochralski method, which provides the high- est-quality single crystals for application in high- performance optics, sapphire semiconductor sub- Figure 3. This “fingerprint” is actually a partially strates, watches, and bearings (Nassau, 1980, p. 84). healed fracture that exhibits a network of fluid With these refinements, the characteristics that inclusions; it is typical of natural colorless sapphire. were previously used to separate natural from syn- Photomicrograph by Shane Elen; magnified 20×. thetic colorless sapphire became less obvious or were eliminated, and the separation became consid- erably more difficult. Review of Identification Techniques. In many instances, larger natural and synthetic colorless sap- phires (see, e.g., figure 2) can be separated by stan- dard gemological methods, such as microscopy (for the identification of inclusions and the study of growth structures visible with immersion) or UV- induced fluorescence (see below). However, smaller, 32 Colorless Sapphire GEMS & GEMOLOGY Spring 1999 Figure 4. This group of gas bubbles is typical of Figure 5. Although bubbles are uncommon in Verneuil synthetic sapphire. Photomicrograph by Czochralski-grown synthetic sapphires, this flask- Shane Elen; magnified 20×. shaped bubble was noted in one of the samples. Photomicrograph by Shane Elen; magnified 20×. niques have almost entirely eliminated any
Load more

Recommended publications
  • Sapphire: Properties, Growth, and Applications
    Sapphire: Properties, Growth, and 1904), which is sometimes called the flame fusion method. In this technique, alumina powder to be Applications crystallized is fused in a hydrogen–oxygen flame and falls on the molten upper surface of an oriented seed Sapphire has a high refractive index and a broad crystal placed in a furnace (Fig. 1(a)). transmission band spanning the UV, visible, and IR Since this is not a refined process, the material can bands. Sapphire also has a high hardness and melting contain voids and powder inclusions and is likely to be point, and very good thermal conductivity, tensile strained. However, crystals of up to 60mm in diameter strength, and thermal shock resistance (Table 1). The can be grown by this method. Figure 2 shows typical favorable combination of excellent optical and mech- sapphire boules grown by the Verneuil technique. anical properties of sapphire, together with high chemical durability, makes it an attractive structural material for high-technology applications. Sapphire crystals are used in medicine and blood chemistry as 1.2 Czochralski Growth they are resistant to human blood and body fluids, and are totally impervious to moisture and chemically This technique originates from pioneering work by inert. Frequently it is the combination of two, or more, Czochralski (1917). Crystals grow from the meniscus of its properties that make sapphire the only material formed on a free surface of the melt onto the seed available to solve complex engineering design crystal of the required crystallographic orientation. problems. The pull rod is lifted and rotated, and crystallization However, sapphire is difficult to shape owing to its onto the end of the seed occurs (Fig.
    [Show full text]
  • Crystal Growth and Defects
    Hartmut S. Leipner, Reinhard Krause-Rehberg Structure of imperfect solids (2) A. Advanced topics B. Methods Syllabus 1–2. Defects and crystal growth 3–4. Defects and semiconductor technology 5–7.* Defect engineering; diffusion 8. Optical methods 9. * Electrical methods 10. * Positron annihilation 11. * Resonance techniques 12. X-ray methods 13. * Probe techniques (* given by Reinhard Krause-Rehberg) 2 Summary As the continuation of the introduction into crystal defects (in the SS 2001), advanced topics of solid state physics related to defects are treated in this semester. Topics are the crystal growth from the point of view of crystal imperfections, diffusion in solids, and the role of defects in the production and the function of solid state devices. In the second part of this lecture, basic experimental techniques of the investigation of defects are introduced. The following methods are treated: optical and electrical methods (luminescence, Hall effect, DLTS), X-ray techniques, probe and resonance techniques (positron annihilation, pertubed angular correlation, electron paramagnetic resonance). The pieces of information to be extracted from the particular methods for the characterization of the defect structure are discussed. 3 Literature K.-T. Wilke: Kristallzüchtung. Berlin: Deutscher Verlag der Wissenschaften 1988. Silicon devices. Ed. K. A. Jackson. Weinheim: Wiley-VCH 1998. Bergmann Schäfer Lehrbuch der Experimentalphysik. Band 6 Festkörper. Hrg. W. Raith. Berlin: De Gruyter 1992. B. G. Jacobi, D. B. Holt: Cathodoluminescence microscopy of inorganic solids. New York: Plenum 1990. S. Pfüller: Halbleitermeßtechnik. Berlin: Verlag Technik 1976. G. Schatz, A. Weidinger: Nukleare Festkörperphysik. Stuttgart: Teubner 1992. Identification of defects in semiconductors. Ed. M. Stavola. San Diego: Academic Press 1998 Hartmut S.
    [Show full text]
  • Development Team
    Material science Paper No. : Crystallography & crystal growth Module : Growth from melt II Development Team Prof. Vinay Gupta, Department of Physics and Astrophysics, Principal Investigator University of Delhi, Delhi Prof. P. N. Kotru ,Department of Physics, University of Jammu, Paper Coordinator Jammu-180006 Content Writer Prof. P. N. Kotru ,Department of Physics, University of Jammu, Jammu-180006 Prof Mahavir Singh Department of Physics, Himachal Pradesh Content Reviewer University, Shimla 1 Crystallography & crystal growth Material science Growth from melt II Description of Module Subject Name Physics Paper Name Crystallography & crystal growth Module Name/Title Growth from melt II Module Id 31 2 Crystallography & crystal growth Material science Growth from melt II 31 Bridgman-Stockbarger Growth Technique. 31.1 Introduction The techniques were originated by Bridgman (1925) and Stockbarger (1938) and so are named after them. In these techniques a crucible containing the material to be grown is lowered through a furnace in such a way that the lowest point in the crucible and the solidification surface rises slowly up the crucible. It means that the melt contained in the crucible is progressively frozen to yield a single crystal. The rate of lowering the crucible may range from about 0.1 to 200 mmh─1 but in most of the cases it may range somewhere in between 1-30 mmh─1. There are situations where the movement of the crucible is reversed. In other words, the crucible is raised up through the furnace and so is advantageously applicable for materials which are volatile; the interface with the vapour being the coolest part of the charge.
    [Show full text]
  • Simultaneous Diamond, White Sapphire & Moissanite
    SIMULTANEOUS DIAMOND, WHITE SAPPHIRE & MOISSANITE TESTER NEW ADVANCED EXCLUSIVE TECHNOLOGY RECOMMENDED by CHARLES & COLVARD CREATED MOISSANITE READ BEFORE USING The new moissanite that was introduced in late 2015 has changed. It can no longer be easily visually identified. It is now D-E-F “colorless”, with few inclusions. More importantly, standard diamond/moissanite testers will identify it as diamond since it is now only very slightly electrically conductive. The UltraTester 3+ uses new technology and is calibrated to identify this faint property. Be aware that body oil is also electrically conductive. Due to the tester’s enhanced sensitivity, dirty diamonds may test as moissanite. To avoid false/positive readings on dirty diamonds, ALWAYS CLEAN THE STONE on a cloth prior to testing. Periodically, also clean any accumulated body oil off of the probe tip by gently rubbing it on uncoated paper - SEE MANUAL. NEED HELP? Call GemOro at 800.527.0719 for immediate assistance. The GemOro UltraTester 3+ is the ultimate tester for diamond fraud protection that’s exclusively RECOMMENDED BY CHARLES & COLVARD, the manufacturer of created moissanite! The UltraTester 3+ features NEW ADVANCED EXCLUSIVE TECHNOLOGY capable of identifying the widest range of the electrically conductive moissanite material available, including the new super-low electrically conductive moissanite. OPERATING PROCEDURE & OWNERS MANUAL Congratulations on your purchase of the UltraTester 3+ from GemOro Superior GEMORO ULTRATESTER 3+ 2 Instruments, the most trusted name in gemological instrumentation for the jewelry industry. You’ve made a great choice. Built upon the foundation of the second generation and most popular tester to date, the UltraTester 3+ offers even more.
    [Show full text]
  • Ga2o3 and Its Vertical Structure Leds
    micromachines Review Epitaxy of III-Nitrides on β-Ga2O3 and Its Vertical Structure LEDs Weijiang Li 1,2,3, Xiang Zhang 1,2,3, Ruilin Meng 1,2,3, Jianchang Yan 1,2,3, Junxi Wang 1,2,3, Jinmin Li 1,2,3 and Tongbo Wei 1,2,3,* 1 State Key Laboratory of Solid-State Lighting, Institute of Semiconductors, University of Chinese Academy of Sciences, Beijing 100083, China; [email protected] (W.L.); [email protected] (X.Z.); [email protected] (R.M.); [email protected] (J.Y.); [email protected] (J.W.); [email protected] (J.L.) 2 Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China 3 Beijing Engineering Research Center for the 3rd Generation Semiconductor Materials and Application, Beijing 100083, China * Correspondence: [email protected]; Tel.: +86-010-8230-5430 Received: 7 April 2019; Accepted: 8 May 2019; Published: 13 May 2019 Abstract: β-Ga2O3, characterized with high n-type conductivity, little lattice mismatch with III-Nitrides, high transparency (>80%) in blue, and UVA (400–320 nm) as well as UVB (320–280 nm) regions, has great potential as the substrate for vertical structure blue and especially ultra violet LEDs (light emitting diodes). Large efforts have been made to improve the quality of III-Nitrides epilayers on β-Ga2O3. Furthermore, the fabrication of vertical blue LEDs has been preliminarily realized with the best result that output power reaches to 4.82 W (under a current of 10 A) and internal quantum efficiency (IQE) exceeds 78% by different groups, respectively, while there is nearly no demonstration of UV-LEDs on β-Ga2O3.
    [Show full text]
  • The Journal of Gemmology Editor: Dr R.R
    he Journa TGemmolog Volume 25 No. 8 October 1997 The Gemmological Association and Gem Testing Laboratory of Great Britain Gemmological Association and Gem Testing Laboratory of Great Britain 27 Greville Street, London Eel N SSU Tel: 0171 404 1134 Fax: 0171 404 8843 e-mail: [email protected] Website: www.gagtl.ac.uklgagtl President: Professor R.A. Howie Vice-Presidents: LM. Bruton, Af'. ram, D.C. Kent, R.K. Mitchell Honorary Fellows: R.A. Howie, R.T. Liddicoat Inr, K. Nassau Honorary Life Members: D.). Callaghan, LA. lobbins, H. Tillander Council of Management: C.R. Cavey, T.]. Davidson, N.W. Decks, R.R. Harding, I. Thomson, V.P. Watson Members' Council: Aj. Allnutt, P. Dwyer-Hickey, R. fuller, l. Greatwood. B. jackson, J. Kessler, j. Monnickendam, L. Music, l.B. Nelson, P.G. Read, R. Shepherd, C.H. VVinter Branch Chairmen: Midlands - C.M. Green, North West - I. Knight, Scottish - B. jackson Examiners: A.j. Allnutt, M.Sc., Ph.D., leA, S.M. Anderson, B.Se. (Hons), I-CA, L. Bartlett, 13.Se, .'vI.phil., I-G/\' DCi\, E.M. Bruton, FGA, DC/\, c.~. Cavey, FGA, S. Coelho, B.Se, I-G,\' DGt\, Prof. A.T. Collins, B.Sc, Ph.D, A.G. Good, FGA, f1GA, Cj.E. Halt B.Sc. (Hons), FGr\, G.M. Howe, FG,'\, oo-, G.H. jones, B.Se, PhD., FCA, M. Newton, B.Se, D.PhiL, H.L. Plumb, B.Sc., ICA, DCA, R.D. Ross, B.5e, I-GA, DGA, P..A.. Sadler, 13.5c., IGA, DCA, E. Stern, I'GA, DC/\, Prof. I.
    [Show full text]
  • Colourless Gemstones
    GEMS THE gem DeteCTIVE: COLOURLess gemstONes superseded in the 1970s by a man-made gemstone called cubic zirconia that is still the most popular and common diamond imitation in modern jewellery due to its low cost, high dispersion and good hardness (8.5 on Mohs scale). Another man-made gemstone called synthetic Moissanite was introduced as a diamond simulant in the late 1990s. Although TED A synthetic Moissanite tests positive on a FFILI A diamond tester, it is easily distinguished from diamond by a property called double refraction, detected using a 10x loupe. This property is also displayed by zircon, a natural CCREESH, O’NEILS O’NEILS CCREESH, gemstone with a sub-adamantine lustre. M N N A Complicating the process of identification are treatments that may affect the value of gemstones. For example, a laser may be used to drill down to a dark diamond inclusion and remove it using acid in a process called GE COURTESY OF BREND OF COURTESY GE laser drilling. Also common is fracture filling, ma I where a high refractive-index lead glass is used to fill surface-reaching fractures to make Sparkling, colourless gemstones may People love to assume that their great ALTHOUGH them less visible. Fortunately, both of these appear similar to the naked eye but they grandma’s solitaire engagement ring SYNTHETIC treatments are easily identified using a loupe can vary significantly in identity, rarity contained a natural diamond by virtue MOISSANITE or microscope. TESTS POSITIVE and value. Making such distinctions of its age but they should think again. Some off-coloured diamonds may be ON A DIamOND requires the detective skills of a qualified Synthetically-produced sapphire, spinel and TESTER, IT CAN BE whitened using High Pressure High gemmologist.
    [Show full text]
  • INTERNSHIP REPORT Single Crystal Growth of Constantan by Vertical
    INTERNSHIP REPORT Single Crystal Growth of Constantan by Vertical Bridgman Method Supervisor: Prof. Henrik Rønnow Laboratory for Quantum Magnetism (LQM) Rahil H. Bharani 08D11004 Third year Undergraduate Metallurgical Engineering and Materials Science IIT Bombay May – July 2011 ACKNOWLEDGEMENT I thank École Polytechnique Fédérale de Lausanne (EPFL) and Prof. Henrik Rønnow, my guide, for having me as an intern here. I have always been guided with every bit of help that I could possibly require. I express my gratitude to Prof. Daniele Mari, Iva Tkalec and Ann-Kathrin Maier for helping me out with my experimental runs and providing valuable insights on several aspects of crystal growth related to the project. I thank Julian Piatek for his help in clearing any doubts that I have had regarding quantum magnetism pertaining to understanding and testing the sample. I am indebted to Neda Nikseresht and Saba Zabihzadeh for teaching me to use the SQUID magnetometer, to Nikolay Tsyrulin for the Laue Camera and Shuang Wang at PSI for the XRF in helping me analyse my samples. I thank Prof. Enrico Giannini at the University of Geneva for helping me with further trials that were conducted there. Most importantly, I thank Caroline Pletscher for helping me with every little thing that I needed and Caroline Cherpillod, Ursina Roder and Prof Pramod Rastogi for co-ordinating the entire internship program. CONTENTS INTRODUCTION REQUIREMENTS OF THE SAMPLE SOME METHODS TO GROW SINGLE CRYSTALS • CZOCHRALSKI • BRIDGMAN • FLOATING ZONE TESTING THE SAMPLES • POLISH AND ETCH • X-RAY DIFFRACTION • LAUE METHOD • SQUID • X-RAY FLUORESCENCE THE SETUP TRIAL 1 TRIAL 2 TRIAL 3 TRIAL 4 Setup, observations, results and conclusions.
    [Show full text]
  • Gemstones by Donald W
    GEMSTONES By Donald W. olson Domestic survey data and tables were prepared by Nicholas A. Muniz, statistical assistant, and the world production table was prepared by Glenn J. Wallace, international data coordinator. In this report, the terms “gem” and “gemstone” mean any gemstones and on the cutting and polishing of large diamond mineral or organic material (such as amber, pearl, petrified wood, stones. Industry employment is estimated to range from 1,000 to and shell) used for personal adornment, display, or object of art ,500 workers (U.S. International Trade Commission, 1997, p. 1). because it possesses beauty, durability, and rarity. Of more than Most natural gemstone producers in the United states 4,000 mineral species, only about 100 possess all these attributes and are small businesses that are widely dispersed and operate are considered to be gemstones. Silicates other than quartz are the independently. the small producers probably have an average largest group of gemstones; oxides and quartz are the second largest of less than three employees, including those who only work (table 1). Gemstones are subdivided into diamond and colored part time. the number of gemstone mines operating from gemstones, which in this report designates all natural nondiamond year to year fluctuates because the uncertainty associated with gems. In addition, laboratory-created gemstones, cultured pearls, the discovery and marketing of gem-quality minerals makes and gemstone simulants are discussed but are treated separately it difficult to obtain financing for developing and sustaining from natural gemstones (table 2). Trade data in this report are economically viable deposits (U.S.
    [Show full text]
  • Growth from Melt by Micro-Pulling Down (Μ-PD) and Czochralski (Cz)
    Growth from melt by micro-pulling down (µ-PD) and Czochralski (Cz) techniques and characterization of LGSO and garnet scintillator crystals Valerii Kononets To cite this version: Valerii Kononets. Growth from melt by micro-pulling down (µ-PD) and Czochralski (Cz) techniques and characterization of LGSO and garnet scintillator crystals. Theoretical and/or physical chemistry. Université Claude Bernard - Lyon I, 2014. English. NNT : 2014LYO10350. tel-01166045 HAL Id: tel-01166045 https://tel.archives-ouvertes.fr/tel-01166045 Submitted on 22 Jun 2015 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. N° d’ordre Année 2014 THESE DE L‘UNIVERSITE DE LYON Délivrée par L’UNIVERSITE CLAUDE BERNARD LYON 1 ECOLE DOCTORALE Chimie DIPLOME DE DOCTORAT (Arrêté du 7 août 2006) Soutenue publiquement le 15 décembre 2014 par VALERII KONONETS Titre Croissance cristalline de cristaux scintillateurs de LGSO et de grenats à partir de l’état liquide par les techniques Czochralski (Cz) et micro-pulling down (μ-PD) et leurs caractérisations Directeur de thèse : M. Kheirreddine Lebbou Co-directeur de thèse : M. Oleg Sidletskiy JURY Mme Etiennette Auffray Hillemans Rapporteur M. Alain Braud Rapporteur M. Alexander Gektin Examinateur M.
    [Show full text]
  • Identifying Diamonds Diamond Is One of the Most Important Gemstones Traded in the World Today
    GEMMOLOGY Identifying Diamonds Diamond is one of the most important gemstones traded in the world today. Diamond has all properties in the superlative state- best luster, highest hardness, highest thermal conductivity among gems and these properties help in identification and form the basis for some of the tips to check whether the white stone is a diamond. t is said that Alexander the stone then do so only with a stone case of simulants, the line will Great found a valley full of both holder or tweezer. Never move appear partially or complete. This Idiamonds and poisonous snakes. your fingers through the diamonds, test can be easily carried out on No one could work out how to you would never know how many unset stones; but care must be retrieve the jewels until Alexander diamonds would get stuck to your taken when they are mounted. had the idea of throwing down fingers and fall out. Confusion is possible with raw meat, to which the diamonds old cut diamonds, in which full attached. When eagles flew down Visual Methods advantage of the low critical angle for the meat, Alexander's men just was not taken in cutting. Here, the had to follow them to their nests. It Tilt Test line may appear unnaturally clear or sounds like fantasy but diamonds The high Refractive Index (RI) of transparent for diamonds. The large are attracted to fat, and the story Diamond makes possible a simple culet and the facet edges will be reminded people how to tell real test to distinguish it quickly from immediately apparent to the naked diamonds from fakes.
    [Show full text]
  • Distinguishing Natural Diamonds from Synthetic Diamonds and Diamond
    Synthetic Diamond Identification About GIA Knowing the Difference Because of the contrasting conditions of natural Established in 1931, GIA has studied the scientific Natural diamonds have long fascinated mankind and artificial formation, synthetic diamonds properties of gems, developing new methods of with their unique physical and visual properties. display several features which allow them to be identifying natural, synthetic and treated gemstones. Distinguishing Features such as exceptional hardness, durability, gemologically distinguished from natural diamonds. This research serves to protect all who buy and sell light reflectivity (brilliance) and dispersion (fire) These include visual characteristics such as color gems by ensuring accurate and unbiased standards Natural Diamonds from distinguish them from other gems. The beauty and zoning, dark metallic inclusions, weak strain for determining and describing gem quality. GIA universal appeal of natural diamonds come at a patterns and distinctive patterns and colors of research findings are incorporated into its educational Synthetic Diamonds and price, as the recovery and fashioning of such rare ultraviolet fluorescence. Because they represent programs, published in professional journals, used for Diamond Simulants gems are challenging. For decades, researchers types of diamonds that are rare in nature, synthetic developing practical instruments and tools and applied have sought alternatives by creating less expensive diamonds also possess additional features that in grading and
    [Show full text]