DOCSLIB.ORG

Diamonds in Simulants

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Diamonds in Simulants DIAMONDS IN SIMULANTS - An Article by the GA Team When it comes to diamond stimulants and substitutes many of us are left in a daze of confusion and hype created around several materials that replace the popular gemstone in jewellery. Here is an account that puts to rest the differences between diamond stimulants and lab-grown diamonds while shedding some light on the different options available out there. The first and most important fact is to realize the difference between diamond stimulants and lab-grown diamonds. Simulants are man-made or naturally occurring materials that are used in place of diamonds, they have different optical, chemical and physical properties from diamonds. Moissanite, cubic zirconia, crystal, rock crystal, white sapphire and white topaz have all been used as diamond substitutes over the years. On the other hand, lab-grown diamonds are diamonds that have been created in a laboratory and have the same physical chemical and optical properties of naturally occurring diamonds. The term synthetic diamond too at times can be misleading. The term can lead one to erroneously think the diamonds are fake, artificial or stimulants. The Federal Trade Commission (FTC) in the US has acknowledged that the term synthetic could mislead consumers when describing man-made diamonds. According to the FTC, "the term is a potentially confusing term, i.e., consumers associate synthetic gemstones with imitation stones." The body has determined that "these other terms ('laboratory-created,' 'laboratory-grown,' '[manufacturer-name]-created') would more clearly communicate the nature of the stone." Moissanite is almost identical to diamond with a hardness of 9.25 (or 9.5 by some accounts) on Moh’s scale. First discovered in 1893 by a French scientist named Henri Moissan, this material originated as a meteorite that fell to earth. However, natural moissanite is incredibly rare; instead it is now is a widely manufactured mineral composed of silicon carbide. Moissanite’s faceting pattern is different and it is easily distinguishable from diamond by its heightened brilliance. This effect increases in sunlight and as stones increase in size. Even in terms of colour moissanites termed “colourless” may project a yellow or greyish hue under certain lights and this effect becomes more noticeable with increase in size. Natural zircon is distinguishable from a diamond as it displays double refraction causing it to have a “fuzzy” appearance, it is also sometimes possible to tell the two apart by the amount of wear and tear of the edges of the zircon’s facets, as zircon is much softer than diamond with a hardness of around 7 – 7.5. Cubic Zirconia (CZ) is a man-made material measuring around 8.5 on Moh’s scale that has been on the market since 1976. Although not as hard as diamond CZ is generally thought to be compositionally superior to diamond due to its greater brilliance and sparkle as well as it's entirely colourless and blemish-free properties. Even so, common opinion also concurs that CZ is simply ‘too perfect’ and that it looks artificial even to the naked eye. Because of this, some CZ manufacturers have started producing the gem with coloured tints and inclusions so that it more closely resembles diamond. Strontium titanate is a colourless manmade material that became a popular diamond simulant in the 1950s. However, its dispersion (the optical property that creates fire in a faceted gemstone) is over four times greater than diamond and makes it easily distinguishable from the real deal under 10X magnification. YAG and GGG were two diamond stimulants that emerged in the 1960s. Yttrium aluminium garnet (YAG) and its “cousin” gadolinium gallium garnet (GGG) were widely manufactured but today have been rendered obsolete by the popularity of cubic zirconia as a diamond substitute. 1 www.gematlas.com Apart from these, crystal, rock crystal, white topaz, synthetic rutile, synthetic and natural white sapphire have been used as diamond simulants over the years but are now more or less easily identifiable with advanced gemmology equipment and identifying techniques. Lab-grown diamonds date back to the early 1970s, when General Electric produced the first gem-quality synthetic diamond crystals. High Pressure High Temperature (HPHT) process and the Carbon Vapour Deposition (CVD) process are the two production methods widely used for producing lab-grown diamonds today. The HPHT process uses graphite or diamond 'powder' in a high pressure high temperature environment, in the presence of a metal solvent and one or several small diamond crystals to act as seeds. This results in diamonds that can grow as large as 10 carats, generally brown or yellow in colour due to the presence of nitrogen. In the CVD process, graphite is vapourised in a vacuum chamber with a diamond crystal. The carbon vapour gets deposited on the seed crystal and the diamond ‘grows.’ Diamonds produced through this method are very pure and free of distortions - and thus colourless, but the crystals are small (below 1 ct of cut gem) and may have graphite inclusions. Distinguishing a synthetic from a natural diamond is quite challenging, and can authoritatively be accomplished only in a well equipped gemmological laboratory. HPHT stones sometimes show traces of the metal solvent which are a tell tale sign of their origin. However these extremely minute and beyond the scope of a 10X loupe or even a microscope. Lab-grown diamonds show distinct UV and IR absorption behaviour, and infrared Raman spectrography is the only reliable method to distinguish them from their natural counterparts. 2 www.gematlas.com.
Load more

Recommended publications
  • CUBIC ZIRCONIA: an UPDATE by Kurt Nassau
    CUBIC ZIRCONIA: AN UPDATE By Kurt Nassau Soon after it was first marketed in 1976, ubic zirconia was discovered as a natural mineral in colorless cubic zirconia became the C 1937, when two German mineralogists, von Staclz- dominant diamond imitation, with elberg and Chudoba (1937), were examining a highly current production of approximately 60 metamict zircon given to them by B. W. Anderson. The million carats per year. Although cubic zircon contained some tiny crystals which they identified zirconia was discovered as a natural by X-ray diffraction as the cubic form of zirconium oxide mineral in 1937, crystals usable for (or zirconia), a compound lznown as baddeleyite when in faceting were first produced ill 1969 and it was not until a practical sltull-melting the monoclinic form. So little did von Staclzelberg and technique was developed in the USSR in Chudoba think of this discovery that they did not even 1972 that commercial production became assign a name to the new mineral. As a result, it is lznown feasible. This article reviews the sl<ull- to this day by its scientific name, cubic zirconia, and the melting technique used to produce cubic prefix synthetic, although proper, is not usually included. zirconio and examines the current status This same material had already been used for many of this diamond simulant with regard to years as a ceramic composition for high-temperature in- q~~ality,production, ond market. The dustrial and scientific purposes; because of an exception- patent situation is discussed, as well as ally high melting point, "stabilized zirconia" ceramics prospects lor new diamond imitations can be used at temperatures up to 2540°C (4604°F)and are and the recent surge of interest in colored cubic zirconia.
    [Show full text]
  • Graphene – Diamond Nanomaterials: a Status Quo Review
    Preprints (www.preprints.org) | NOT PEER-REVIEWED | Posted: 29 July 2021 doi:10.20944/preprints202107.0647.v1 Article Graphene – diamond nanomaterials: a status quo review 1 Jana Vejpravová ,* 1 Department of Condensed Matter Physics, Faculty of Mathematics and Physics, Charles University, Ke Karlovu 5, 121 16 Prague 2, Czech Republic. * Correspondence: JV, [email protected] Abstract: Carbon nanomaterials with a different character of the chemical bond – graphene (sp2) and nanodiamond (sp3) are the building bricks for a new class of all-carbon hybrid nanomaterials, where the two different carbon networks with the sp3 and sp2 hybridization coexist, interact and even transform into one another. The unique electronic, mechanical, and chemical properties of the two border nanoallotropes of carbon ensure the immense application potential and versatility of these all-carbon graphene – diamond nanomaterials. The review gives an overview of the current state of the art of graphene – diamond nanomaterials, including their composites, heterojunctions, and other hybrids for sensing, electronic, energy storage, and other applications. Also, the graphene- to-diamond and diamond-to-graphene transformations at the nanoscale, essential for innovative fabrication, and stability and chemical reactivity assessment are discussed based on extensive theo- retical, computational, and experimental studies. Keywords: graphene; diamond; nanodiamond; diamane; graphene-diamond nanomaterials; all car- bon materials; electrochemistry; mechanochemistry; sensor; supercapacitor;
    [Show full text]
  • Preparation of Barium Strontium Titanate Powder from Citrate
    APPLIED ORGANOMETALLIC CHEMISTRY Appl. Organometal. Chem. 13, 383–397 (1999) Preparation of Barium Strontium Titanate Powder from Citrate Precursor Chen-Feng Kao* and Wein-Duo Yang Department of Chemical Engineering, National Cheng Kung University, Tainan, 70101, Taiwan TiCl4 or titanium isopropoxide reacted with INTRODUCTION citric acid to form a titanyl citrate precipitate. Barium strontium citrate solutions were then BaTiO3 is ferroelectric and piezoelectric and has added to the titanyl citrate reaction to form gels. extensive applications as an electronic material. It These gels were dried and calcined to (Ba,Sr)- can be used as a capacitor, thermistor, transducer, TiO3 powders. The gels and powders were accelerometer or degausser of colour television. characterized by DSC/TGA, IR, SEM and BaTiO3 doped with strontium retains its original XRD analyses. These results showed that, at characteristics but has a lower Curie temperature 500 °C, the gels decomposed to Ba,Sr carbonate for positive temperature coefficient devices under and TiO2, followed by the formation of (Ba,Sr)- various conditions. TiO3. The onset of perovskite formation oc- Besides solid-state reactions, chemical reactions curred at 600 °C, and was nearly complete at have also been used to prepare BaTiO3 powder. 1 1000 °C. Traces of SrCO3 were still present. Among them the hydrolysis of metal alkoxide , The cation ratios of the titanate powder oxalate precipitation in ethanol2, and alcoholic prepared in the pH range 5–6 were closest to dehydration of citrate solution3 are among the more the original stoichiometry. Only 0.1 mol% of the attractive methods. In 1956 Clabaugh et al.4 free cations remained in solution.
    [Show full text]
  • X-Ray Topographic Investigation of Diamond Anvils for High Pressure Generation - Correlation Between Defects and Early Failure
    X-ray topographic investigation of diamond anvils for high pressure generation - Correlation between defects and early failure Dewaele A. and Loubeyre P. CEA/DPTA, BP12, 91680 Bruyères le Châtel The diamond anvil cell technique revolutionized high pressure physics some 25 years ago. This device takes advantage of the unusual mechanical properties of the diamond. A metallic gasket with a hole in it to confine the sample is compressed between two diamond anvils. This device allows the generation of pressures that reach 300 GPa (3 millions times atmospheric pressure), pressure at which the diamond exhibits large elastic strain [1]. The pressure reached in diamond anvil cells is very often limited by the failure of a diamond anvil. In order to prevent this phenomenon, anvils are selected on the basis of their chemical purity, and their internal strains. However, the chemical purity does not guarantee the resistance of diamond anvils under high pressure operation. In particular, when the diamonds are used in contact with H2 or Helium samples, species which diffuse in diamond. Unfortunately, helium is known to be the best pressure transmitting medium, and is often loaded for that use in diamonds anvil cells [2]. A better understanding of early breakdown of diamond anvils and an a priori diagnostic of their resistance would thus constitute a major improvement for high pressure techniques. X-ray topography helps to establish this anvils quality diagnostic, because this method evidences intrinsic crystallographic defects of the anvils. These defects are likely to influence the mechanical properties of the anvil [3]. However, the liability of x-ray topography diagnostic had to be proven.
    [Show full text]
  • Ecological Comparison of Synthetic Versus Mined Diamonds
    Ecological Comparison of Synthetic versus Mined Diamonds Saleem H. Ali Working Paper, Institute for Environmental Diplomacy and Security University of Vermont, January, 2011 http://www.uvm.edu/ieds Abstract The energy usage and emissions in mined versus lab-created diamonds was evaluated, based on industrial data, since these two factors are often a general indicator of environmental impact that can be useful in product comparisons. Depending on the process and the location of the mine, the data can be highly divergent and cannot be used as a singular measure of environmental impact. There is a need to develop life cycle analysis techniques from industrial ecology to conduct a detailed comparison of synthetic versus mined stones. Introduction Synthetic diamonds have come of age, and the year 2010 will be remembered as a landmark year in this regard since for the first time labs of the Gemological Institute of America (GIA) in New York were able to grade a gem quality near-colorless synthetic diamond (formed by chemical vapor deposition) , greater than 1 carat. The history of synthetic diamonds at the industrial level, goes back to patents for super-abrasives at General Electric can be traced back to several decades (Hazen, 1996). However, gem quality synthetic diamonds have only risen to prominence in the last decade with the rise of a few key companies who are taking on this growing market in concert with boutique jewelry brands. As jewelers consider environmental social responsibility more seriously in marketing their gemstone products, energy usage in mined versus lab-created gems can be an important factor in determining comparative environmental impact.
    [Show full text]
  • OF SYNTHETIC DIAMONDS. Introduction
    PI ^ AU9817130 IONOLUMINESCENCE (IL) OF SYNTHETIC DIAMONDS. A. A. Bettiol, K. W. Nugent, D. N. Jamieson and S. Prawer School of Physics, Microanalytical Research Centre, University of Melbourne, Parkville, 3052, AUSTRALIA. Introduction The optical properties of natural and synthetic diamonds have been extensively characterized in the past by absorption and luminescence. The use of such techniques as cathodoluminescence, photoluminescence, photoluminescence excitation and electron spin and paramagnetic resonance has resulted in the identification of many impurity and defect related optical centres in diamond [1-2]. Of the impurities found in diamond, nitrogen is by far the most abundant and hence responsible for most of the optical properties [3]. The development of diamond synthesis methods has resulted in the discovery of a number of a new optically active impurities and defects which are introduced during the growth process. These include Si, O, Ni and B [1-2]. In this study we identify a number of defect and impurity related centres in two commercially produced synthetic diamond samples by using the novel technique of ionoluminescence (IL) [4]. The first sample characterized is a Norton polycrystalline diamond detector. Signal produced in any charged particle detector is degraded if recombination of the electrons and holes occurs before the charge can be swept out by the electric field in the detector. In diamonds where the radiative recombination cross-section can be quite high, signal degradation can occur depending on the optical centres present and their lifetimes. Recombination centres with lifetimes much longer than the sweep out time will potentially saturate hence only cause a degradation of signal.
    [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]
  • DIAMOND Natural Colorless Type Iab Diamond with Silicon-Vacancy
    Editors Thomas M. Moses | Shane F. McClure DIAMOND logical and spectroscopic features con- Natural Colorless Type IaB firmed the diamond’s natural origin, – Diamond with Silicon-Vacancy despite the occurrence of [Si-V] emis- Defect Center sions. No treatment was detected. Examination of this stone indicated The silicon-vacancy defect, or [Si-V]–, that the [Si-V]– defect can occur, albeit is one of the most important features rarely, in multiple types of natural dia- in identifying CVD synthetic dia- monds. Therefore, all properties should monds. It can be effectively detected be carefully examined in reaching a using laser photoluminescence tech- conclusion when [Si-V]– is present. nology to reveal sharp doublet emis- sions at 736.6 and 736.9 nm. This Carmen “Wai Kar” Lo defect is extremely rare in natural dia- monds (C.M. Breeding and W. Wang, “Occurrence of the Si-V defect center Figure 1. Emissions from the Screening of Small Yellow Melee for in natural colorless gem diamonds,” silicon-vacancy defect at 736.6 and Treatment and Synthetics Diamond and Related Materials, Vol. 736.9 nm were detected in this Diamond treatment and synthesis 17, No. 7–10, pp. 1335–1344) and has 0.40 ct type IaB natural diamond. have undergone significant develop- been detected in very few natural type ments in the last decade. During this IIa and IaAB diamonds over the past showed blue fluorescence with natural time, the trade has grown increasingly several years. diamond growth patterns. These gemo- concerned about the mixing of treated Recently, a 0.40 ct round brilliant diamond with D color and VS2 clarity (figure 1) was submitted to the Hong Figure 2.
    [Show full text]
  • Sensitization of Titanium Dioxide and Strontium Titanate Electrodes By
    Subscriber access provided by University of Texas Libraries Sensitization of titanium dioxide and strontium titanate electrodes by ruthenium(II) tris(2,2'-bipyridine-4,4'-dicarboxylic acid) and zinc tetrakis(4-carboxyphenyl)porphyrin: an evaluation of sensitization efficiency for component photoelectrodes in a multipanel device Reza Dabestani, Allen J. Bard, Alan Campion, Marye Anne Fox, Thomas E. Mallouk, Stephen E. Webber, and J. M. White J. Phys. Chem., 1988, 92 (7), 1872-1878 • DOI: 10.1021/j100318a035 Downloaded from http://pubs.acs.org on February 2, 2009 More About This Article The permalink http://dx.doi.org/10.1021/j100318a035 provides access to: • Links to articles and content related to this article • Copyright permission to reproduce figures and/or text from this article The Journal of Physical Chemistry is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 1872 J. Phys Chem. 1988, 92, 1872-1878 Sensitization of Titanium Dioxide and Strontium Titanate Electrodes by Ruthenium( I I) Trls (2,2’- bipyridine-4,4’-dicar box y lic acid) and Zinc Tetrakis (4-carboxy phen yl) porphyrin: An Evaluation of Sensitization Efficiency for Component Photoelectrodes in a Muitipanei Device Reza Dabestani, Allen J. Bard, Alan Campion, Marye Anne Fox,* Thomas E. Mallouk, Stephen E. Webber, and J. M. White Department of Chemistry, University of Texas, Austin, Texas 78712 (Received: December 1. 1986; In Final Form: October 6, 1987) The utility of polycrystalline anatase Ti02 and SrTi03 semiconductor electrodes sensitized by ruthenium(I1) tris(2,2’-bi- pyridine-4,4’-dicarboxylicacid) (1) and by zinc tetrakis(4-carboxypheny1)porphyrin (2) as component photoelectrodes in a multipanel array has been evaluated.
    [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]
  • Download PRIM II Refractive Index Chart
    What is Refractive Index (R.I.)? What do the numbers Light travels at different speeds through in the brackets on this chart mean? different types of gemstones due to The numbers in the brackets indicate the Important Note structure of the stone. This affects the tolerance level for readings derived from All testers have been calibrated during the manufacturing process and requires no amount of light refraction and causes the the product. These slight fluctuations further adjustment or user intervention. Self-calibration should not be attempted and is bending of light. The slower the light's indicating a tolerance level are necessary not advised. speed in the material; the greater the due to the optical sensor and electronic REFRACTIVE INDEX CHART FOR bending effect. The refractive index of the components in the product. To minimize any risks associated, users should contact Presidium at gemstone can be defined as the ratio [email protected] or its service center for assistance. PRESIDIUM REFRACTIVE INDEX METER II between the speed of light in vacuum versus the speed of light in gemstone. In the event that users require the manufacturer to re-calibrate the unit, users will have to bear the associated to and fro freight cost for shipping of the unit to the Presidium service center. Presidium Instruments Please note that the gemstone tested on this product must have a flat surface and should Unit 7, 207 Henderson Road Singapore 159550 not be an opaque gemstone. www.presidium.com.sg Family Name of Stones Refractive Index Reading Family
    [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]