DOCSLIB.ORG

Winter 1995 Gems & Gemology

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Winter 1995 Gems & Gemology TABL E 0 F CONTENTS EDITORIAL Diamond Prospecting and Market Prospects Richard T. Liddicoat FEATURE ARTICLES A History of Diamond Sources in Africa: Part I A. /. A. (Bram)/arise A Chart for the Separation of Natural and Synthetic Diamonds lames E. Sl~igley,Emmanuel Fritsch, Ilene Reinitz, and Thomas E. Moses REGULAR FEATURES Gem Trade Lab Notes Gem News Book Reviews Gemological Abstracts Annual Index ABOUT THE COVER: The modern history of the diamond industry start- ed in the late 1860s, with the discovery of a bright pebble on a farm in South Africa. Soon, prospectors had spread throughout the Kimberley area (and, eventually, into neighboring countries) looking for-and finding- many major alluvial deposits and the host pipes themselves. For more than a hundred years, countries on the African continent dominated the supply of gem diamonds. Even today, they continue to provide millions of carats annually for the consun1er market. The lead article in this issz~e,Part I of a two-part series, provides a fascinating, and factual, history of the diamond discoveries in southern Africa. The 27.74 ct yellow diamond in the pen- dant to this diamond neclzlace is of African origin; ii is surro~~ndedby 19 circular-cut diamonds, which range from 0.90 to 2.53 ct. Necklace by Harry Winston; photo courtesy of Christie's. Color separations for Gems & Gemology are by Effective Graphics, Compton, CA. Printing is by Cadmus Journal Services, Easton, MD. 0 1996 Gemological Institute of America All rights reserved ISSN 0016-626 Editor-in-Chief Editor Editors, Gem Trade Lab Notes Richard T. Liddicoat Alice S. Keller Robert C. Kamnierling 1660 Stewart St. C. W. Fryer Associate Editors Santa Monica, CA 90404 William E. Boyajian Editors, Gem News (310) 829-299 1 x251 Robert C. IZammerling Robert C. Kammerling c-mail: [email protected] D. Vincent Mcinson John I. Koivula John Sinkankas Subscriptions Mary L. Johnson Technical Editor Jin Lim Cristina Chavira Editors, Book Reviews Carol M. Stockton (800)42 1-7250 x201 Susan B. Johnson Fax: (310) 453-4478 Jana E. Miyahira Assistant Editor Irv Dierdorff Contributing Editor Editor, Geinological Abstracts e-mail: [email protected] John I. Koivula C. W. Fryer Art Director Production Assistant Christine Troianello Gail Young G. Robert Crowningshiekl C. S. Hurlbut, Jr. A. A. Levinson New York, NY Can~lmdge,MA Calgary, Alberta, Canada Alan T. Collins Alan Jobbins Kurt Nassau London, United Kingdom Caterham, United Kingdom P.0. Lebanon, Nl Dennis Foltz Anthony R. Kampf George Rossman Santa Monica, CA Los Angeles, CA Pasadena, CA Emmanuel Fritsch Robert E. Kane Kenneth Scarratt Nantes, France Helena, MT Bangkok, Thailand C. W. Fryer John I. Koivula Karl Schinetzer Santa Monica, CA Santa Monica, CA Petershausen, Germany Henry A. Hiinni James E. Shigley Basel, Switzerland Santa Monica, CA Subscriptions in the U.S.A. are priced as follows: $59.95 for onc year (4 issues), $149.95 for three years 112 issues). Subscriptions sent elsewhere arc $70.00 for one year, $180.00 for three years. Spccial annual subscription rates are available for all students actively involved in a CIA program: $49.95, U.S.A.; S60.00, elsewhere. Your student numbcr must be listed nt the time your subscription is entered. Single issues may be purchased for $15.00 in the U.S.A., $18.00 elsewhere. Discounts are given for bulk orders of 10 or more of any one issue. A limited numbcr of back issues of GeJG arc also available for purchase. Please address all inquiries regarding subscriptions and the purchase of single copies or back issues to the Subscriptions Dep.-ir~iiient. To obtain a Japanese translation of Gems dl Geniology, contact the Association of Japan Gem Trust, Okachimachi Cy Bldg., 5-15-14 Ucno, Taito-la, Tokyo 110, Japan. Our Canadian goods and service registration number is 126142892RT. Gems el Gemology wclcomcs the subn~issionof articles on all aspects of the field. Please sec the Suggestions for Authors in the Spring 1995 issue of the journal, or contact the editor for a copy. Letters on articles published in Gems a) Gemology and othcr relevant matters are also welcomc. Abstracting is permitted with credit to the source. Libraries are permitted to photocopy beyond the limits of U.S. copyright law for private use of patrons. Instructors arc permitted to photocopy isolated articles for noncommercial classroom use without fee. Copying of the photographs by any means othcr than traditional photocopying tech- niques (Xerox, etc.) is prohibited without the express permission of the photographer (where listcd) or author of the article in which the photo appears (where no photographer is listed). For other copying, reprint, or republication pcr- mission,. .nlease contact the editor. Gems a) Gemology is puhlislicd quarterly by the Gemological Institute of America, a nonprofit educational organi- zation for the jewelry industry, 1660 Stewart Street, Santa Monica, CA 90404. Postmastei: Return unilelivcrahle copies of Gems et) Gelnology to 1660 Stcwait Street, Santa Monica, CA 70404, Any opinions expressed in signed articles are understood to bc the opinions of the authors and not of the publishers. Richard T ~iddicoit,Editor-in-Chief - The search for diamonds has been a preoccupation of wealth-seekers for count- less years. The early discoveries in India, Brazil, and South Africa clearly were fortuitous. More recent discoveries in Africa, as well as on other continents, also have had an element of luck, although many have been based on sound scientific principles. These principles have developed (slowly at first) since the 1870s, when the significance of the kimbcrlite pipes in South Africa was first recog- nized. In the late 1930s) on the basis of these same principles, Professor Vladimir Sobolev discerned the geologic similarities between the diamond-producing areas of South Africa and those of the Yakutia region-leading to the discovery and development of the prolific Siberian diamond mines since the 1950s. In the two-part article by Dr. Brain Janse, an internationally recognized expert in diamond exploration, the history of diamond discoveries on the entire African continent is discussed. As the "plot" unfolds, one is able to follow the evolution of the discovery and production of diamonds from an increasing number of African countries, as well as the fundan~entalgeologic concepts that now form the basis of all modern exploration programs, but throughout the world. The success of diamond exploration has been phenomenal, and some have expressed concern over the prospect of a gem diamond glut as production from new sources has become available. The influx of diamonds from Russia (since 1959),Botswana (since the early 1980~)~and Australia (sincethe mid-1980s) has increased the supply at a dramatic pace-since the mid-1980s alone, from less than 50 million to more than 100 million carats annually. Notwithstanding the continual increase in the supply of diamonds over more than a century, there has been no obvious effect on prices, nor on the appeal of diamonds to the buy- ing public (except, possibly, to make them even more appealing!).Demand for diamonds and diamond jewelry, fueled first and foremost by the American mar- ket, subsequently by the ~a~akesemarket (where present demand has been sti- fled by a pervasive recession), and, most recently, by other Pacific Rim countries, continues unabated. Thus, the market would be expected to absorb moderate increases in production from new discoveries without any significant distortion. Among diainantaires, there seems to be more concern (warranted or not) about the potential impact of jewelry-quality synthetic diamonds, should they ever . become available at a fraction of the price of natural stones. The second article in this issue, and the chart that accompanies it, represent how we at GIA feel that this challenge can best be tackled: through research and education. The well-informed jeweler-gemologist can be just as effective in controlling the impact of synthetic diamonds as the market has been in managing the influx of natural ones. Q 227 Editorial GEMS &. GEMOLOGY Winter 1995 IN AFRICA:PART I By A. J. A. (Bram) Janse For more than 100 years, Africa has pro- lthough diamonds have been known for more than duced large commercial quantities of dia- 2,000 years, with the earliest discoveries in India, monds and important individual stones. large-scale mining and distribution date only from The earliest official finds were made from the late 1860s and the first finds in Africa. For almost a centu- approximately 1867 onward, in sands and ry, Africa-and especially South AfricaÑdon~inate diamond gravels of the Orange and Vaal Rivers in production, representing more than 98% of world output South Africa. Subsequently, diamonds from 1889 to 1959. Many of the most famous stones ever to were found in "hard rock" kimberlites and, most recently, in off-shore deposits enter the gem market originated from these African deposits. along the western coast of South Africa In addition, much of our current knowledge about diamond and Namibia. Important discoveries have occurrences, exploration, and mining comes from the African been made in many other African coun- diamond fields. And the history of these discoveries is among tries. Angola, Botswana, Central African the richest in the archives of gemology. Republic, Ghana, Namibia, and Zaire The first reliable records of diamond finds in Africa date have now joined South Africa as being from the late 1860s ("Diamonds are trumps," April 18, 1867). among the top 10 dian~ond-producing These followed the earlier finds in India several centuries B.C. countries worldwide. Part I of this two- (recorded in Arthasastra and Ratnapariska Sanskrit texts, as part series examines the fascinating histo- reported in Legrand, 1984); Borneo in the 10th century A.D.
Load more

Recommended publications
  • Mg2sio4) in a H2O-H2 Gas DANIEL TABERSKY1, NORMAN LUECHINGER2, SAMUEL S
    Goldschmidt2013 Conference Abstracts 2297 Compacted Nanoparticles for Evaporation behavior of forsterite Quantification in LA-ICPMS (Mg2SiO4) in a H2O-H2 gas DANIEL TABERSKY1, NORMAN LUECHINGER2, SAMUEL S. TACHIBANA1* AND A. TAKIGAWA2 2 2 1 , HALIM , MICHAEL ROSSIER AND DETLEF GÜNTHER * 1 Department of Natural History Sciences, Hokkaido 1ETH Zurich, Department of Chemistry and Applied University, N10 W8, Sapporo 060-0810, Japan. Biosciences, Laboratory of Inorganic Chemistry (*correspondence: [email protected]) (*correspondence: [email protected]) 2Carnegie Institution of Washington, Department of Terrestrial 2Nanograde, Staefa, Switzerland Magnetism, 5241 Broad Branch Road NW, Washington DC, 20015 USA. Gray et al. did first studies of LA-ICPMS in 1985 [1]. Ever since, extensive research has been performed to Forsterite (Mg2SiO4) is one of the most abundant overcome the problem of so-called “non-stoichiometric crystalline silicates in extraterrestrial materials and in sampling” and/or analysis, the origins of which are commonly circumstellar environments, and its evaporation behavior has referred to as elemental fractionation (EF). EF mainly consists been intensively studied in vacuum and in the presence of of laser-, transport- and ICP-induced effects, and often results low-pressure hydrogen gas [e.g., 1-4]. It has been known that in inaccurate analyses as pointed out in, e.g. references [2,3]. the evaporation rate of forsterite is controlled by a A major problem that has to be addressed is the lack of thermodynamic driving force (i.e., equilibrium vapor reference materials. Though the glass series of NIST SRM 61x pressure), and the evaporation rate increases linearly with 1/2 have been the most commonly reference material used in LA- pH2 in the presence of hydrogen gas due to the increase of ICPMS, heterogeneities have been reported for some sample the equilibrium vapor pressure.
    [Show full text]
  • A Quick Guide to Cooking with Ausab Abalone in Brine
    A Quick Guide to Cooking With Ausab Abalone in Brine Ausab Canned Abalone is a versatile product that requires minimal effort to create the perfect meal at home. The abalone is completely cleaned and cooked, and ready to eat. With a unique umami flavor, it can be used in many different ways. The meat is smooth and tender, and the perfect balance between sweet and salty. Ensure the canned abalone is stored in a well ventilated, cool place out of direct sunlight. How to Prepare the Abalone The abalone is canned, ready to eat with mouth attached. To preserve it’s tender texture, it is best to use the abalone when just heated through. This can be achieved by using the abalone at the end of cooking, or slowly heated in the can. To safely heat the abalone in it’s can follow these steps: 1. Leave the can unopened and remove all labels. 2. Place the can into a pot of water so that it is fully submerged and is horizontal. 3. Bring the water to a gentle simmer and leave submerged for 15 – 20 minutes. 4. Remove the pot from the heat and wait for the water to cool before carefully lifting the can out of the water with large tongs. 5. Open the can once it is cool enough to handle. 6. The abalone can be served whole or sliced thinly. Abalone Recipes Ausab Canned Abalone can be pan fried, used in soups or grilled. Teriyaki Abalone Serves 4 1 x Ausab Canned Abalone in Brine 250ml Light Soy Sauce 200ml Mirin 200ml Sake 60g Sugar 1.
    [Show full text]
  • CHEMICAL STUDIES on the MEAT of ABALONE (Haliotis Discus Hannai INO)-Ⅰ
    Title CHEMICAL STUDIES ON THE MEAT OF ABALONE (Haliotis discus hannai INO)-Ⅰ Author(s) TANIKAWA, Eiichi; YAMASHITA, Jiro Citation 北海道大學水産學部研究彙報, 12(3), 210-238 Issue Date 1961-11 Doc URL http://hdl.handle.net/2115/23140 Type bulletin (article) File Information 12(3)_P210-238.pdf Instructions for use Hokkaido University Collection of Scholarly and Academic Papers : HUSCAP CHEMICAL STUDIES ON THE MEAT OF ABALONE (Haliotis discus hannai INo)-I Eiichi TANIKAWA and Jiro YAMASHITA* Faculty of Fisheries, Hokkaido University There are about 90 existing species of abalones (Haliotis) in the world, of which the distribution is wide, in the Pacific, Atlantic and Indian Oceans. Among the habitats, especially the coasts along Japan, the Pacific coast of the U.S.A. and coasts along Australia have many species and large production. In Japan from ancient times abalones have been used as food. Japanese, as well as American, abalones are famous for their large size. Among abalones, H. gigantea (" Madaka-awabi "), H. gigantea sieboldi (" Megai-awabi "), H. gigantea discus (" Kuro-awabi") and H. discus hannai (" Ezo-awabi") are important in commerce. Abalone is prepared as raw fresh meat (" Sashimi") or is cooked after cut­ ting it from the shell and trimming the visceral mass and then mantle fringe from the large central muscle which is then cut transversely into slices. These small steaks may be served at table as raw fresh meat (" Sashimi") or may be fried, stewed, or minced and made into chowder. A large proportion of the abalones harvested in Japan are prepared as cooked, dried and smoked products for export to China.
    [Show full text]
  • The Hydrous Component in Andradite Garnet
    American Mineralogist, Volume 83, pages 835±840, 1998 The hydrous component in andradite garnet GEORG AMTHAUER* AND GEORGE R. ROSSMAN² Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91125, U.S.A. ABSTRACT Twenty-two andradite samples from a variety of geological environments and two syn- thetic hydroandradite samples were studied by Fourier transform IR spectroscopy. Their 2 spectra show that H enters andradite in the form of OH . Amounts up to 6 wt% H2O occur in these samples; those from low-temperature formations contain the most OH2. Some 42 ↔ 42 features in the absorption spectra indicate the hydrogarnet substitution (SiO4) (O4H4) whereas others indicate additional types of OH2 incorporation. The complexity of the spectra due to multi-site distribution of OH2 increases with increasing complexity of the garnet composition. 42 ↔ 42 INTRODUCTION tution (O4H4) (SiO4) . This observation has been Systematic studies have shown that hydroxide is a con®rmed by XRD of a hydrous andradite with a Si de- common minor component of grossular and pyrope-al- ®ciency of about 50%, and a high OH content (Arm- mandine-spessartite garnets (Aines and Rossman 1985; bruster 1995). The structure of this particular sample with Rossman and Aines 1991). Comparable surveys of an- space group Ia3d is composed of disordered microdo- dradite garnet have not been previously presented. Sev- mains containing (SiO4) and (O4H4) tetrahedral units. eral reports indicate that appreciable amounts of OH2 can The aim of the present investigation was to perform a be incorporated in both natural and synthetic andradite- Fourier transform infrared (FTIR) study on different sam- rich garnet (Flint et al.
    [Show full text]
  • Mineral Processing
    Mineral Processing Foundations of theory and practice of minerallurgy 1st English edition JAN DRZYMALA, C. Eng., Ph.D., D.Sc. Member of the Polish Mineral Processing Society Wroclaw University of Technology 2007 Translation: J. Drzymala, A. Swatek Reviewer: A. Luszczkiewicz Published as supplied by the author ©Copyright by Jan Drzymala, Wroclaw 2007 Computer typesetting: Danuta Szyszka Cover design: Danuta Szyszka Cover photo: Sebastian Bożek Oficyna Wydawnicza Politechniki Wrocławskiej Wybrzeze Wyspianskiego 27 50-370 Wroclaw Any part of this publication can be used in any form by any means provided that the usage is acknowledged by the citation: Drzymala, J., Mineral Processing, Foundations of theory and practice of minerallurgy, Oficyna Wydawnicza PWr., 2007, www.ig.pwr.wroc.pl/minproc ISBN 978-83-7493-362-9 Contents Introduction ....................................................................................................................9 Part I Introduction to mineral processing .....................................................................13 1. From the Big Bang to mineral processing................................................................14 1.1. The formation of matter ...................................................................................14 1.2. Elementary particles.........................................................................................16 1.3. Molecules .........................................................................................................18 1.4. Solids................................................................................................................19
    [Show full text]
  • Rare Earth Elements in Planetary Crusts: Insights from Chemically Evolved Igneous Suites on Earth and the Moon
    minerals Article Rare Earth Elements in Planetary Crusts: Insights from Chemically Evolved Igneous Suites on Earth and the Moon Claire L. McLeod 1,* and Barry J. Shaulis 2 1 Department of Geology and Environmental Earth Sciences, 203 Shideler Hall, Miami University, Oxford, OH 45056, USA 2 Department of Geosciences, Trace Element and Radiogenic Isotope Lab (TRaIL), University of Arkansas, Fayetteville, AR 72701, USA; [email protected] * Correspondence: [email protected]; Tel.: +1-513-529-9662 Received: 5 July 2018; Accepted: 8 October 2018; Published: 16 October 2018 Abstract: The abundance of the rare earth elements (REEs) in Earth’s crust has become the intense focus of study in recent years due to the increasing societal demand for REEs, their increasing utilization in modern-day technology, and the geopolitics associated with their global distribution. Within the context of chemically evolved igneous suites, 122 REE deposits have been identified as being associated with intrusive dike, granitic pegmatites, carbonatites, and alkaline igneous rocks, including A-type granites and undersaturated rocks. These REE resource minerals are not unlimited and with a 5–10% growth in global demand for REEs per annum, consideration of other potential REE sources and their geological and chemical associations is warranted. The Earth’s moon is a planetary object that underwent silicate-metal differentiation early during its history. Following ~99% solidification of a primordial lunar magma ocean, residual liquids were enriched in potassium, REE, and phosphorus (KREEP). While this reservoir has not been directly sampled, its chemical signature has been identified in several lunar lithologies and the Procellarum KREEP Terrane (PKT) on the lunar nearside has an estimated volume of KREEP-rich lithologies at depth of 2.2 × 108 km3.
    [Show full text]
  • Circular 162. the Soft-Shell Clam
    HE OFT­ iHELL 'LAM UNITED STATES DEPARTMENT 8F THE INTERIOR FISH AND WILDLIFE SERVICE BUREAU OF COMMERCIAL FISHERIES Circular 162 CONTENTS Page 1 Intr oduc tion. • • • . 2 Natural history • . ~ . 2 Distribution. 3 Taxonomy. · . Anatomy. • • • •• . · . 3 4 Life cycle. • • • • • . • •• Predators, diseases, and parasites . 7 Fishery - methods and management .•••.••• • 9 New England area. • • • • • . • • • • • . .. 9 Chesapeake area . ........... 1 1 Special problem s of paralytic shellfish poisoning and pollution . .............. 13 Summary . .... 14 Acknowledgment s •••• · . 14 Selected bibliography •••••• 15 ABSTRACT Describes the soft- shell cla.1n industry of the Atlantic coast; reviewing past and present economic importance, fishery methods, fishery management programs, and special problems associated with shellfish culture and marketing. Provides a summary of soft- shell clam natural history in- eluding distribution, taxonomy, anatomy, and life cycle. l THE SOFT -SHELL CLAM by Robert W. Hanks Bureau of Commercial Fisheries Biological Labor ator y U.S. Fish and Wildlife Serv i c e Boothbay Harbor, Maine INTRODUCTION for s a lted c l a m s used as bait by cod fishermen on t he G r and Bank. For the next The soft-shell clam, Myaarenaria L., has 2 5 years this was the most important outlet played an important role in the history and for cla ms a nd was a sour ce of wealth to economy of the eastern coast of our country . some coastal communities . Many of the Long before the first explorers reached digg ers e a rne d up t o $10 per day in this our shores, clams were important in the busin ess during October to March, when diet of some American Indian tribes.
    [Show full text]
  • List of New Mineral Names: with an Index of Authors
    415 A (fifth) list of new mineral names: with an index of authors. 1 By L. J. S~v.scs~, M.A., F.G.S. Assistant in the ~Iineral Department of the,Brltish Museum. [Communicated June 7, 1910.] Aglaurito. R. Handmann, 1907. Zeita. Min. Geol. Stuttgart, col. i, p. 78. Orthoc]ase-felspar with a fine blue reflection forming a constituent of quartz-porphyry (Aglauritporphyr) from Teplitz, Bohemia. Named from ~,Xavpo~ ---- ~Xa&, bright. Alaito. K. A. ~Yenadkevi~, 1909. BuU. Acad. Sci. Saint-P6tersbourg, ser. 6, col. iii, p. 185 (A~am~s). Hydrate~l vanadic oxide, V205. H~O, forming blood=red, mossy growths with silky lustre. Founi] with turanite (q. v.) in thct neighbourhood of the Alai Mountains, Russian Central Asia. Alamosite. C. Palaehe and H. E. Merwin, 1909. Amer. Journ. Sci., ser. 4, col. xxvii, p. 899; Zeits. Kryst. Min., col. xlvi, p. 518. Lead recta-silicate, PbSiOs, occurring as snow-white, radially fibrous masses. Crystals are monoclinic, though apparently not isom0rphous with wol]astonite. From Alamos, Sonora, Mexico. Prepared artificially by S. Hilpert and P. Weiller, Ber. Deutsch. Chem. Ges., 1909, col. xlii, p. 2969. Aloisiite. L. Colomba, 1908. Rend. B. Accad. Lincei, Roma, set. 5, col. xvii, sere. 2, p. 233. A hydrated sub-silicate of calcium, ferrous iron, magnesium, sodium, and hydrogen, (R pp, R',), SiO,, occurring in an amorphous condition, intimately mixed with oalcinm carbonate, in a palagonite-tuff at Fort Portal, Uganda. Named in honour of H.R.H. Prince Luigi Amedeo of Savoy, Duke of Abruzzi. Aloisius or Aloysius is a Latin form of Luigi or I~ewis.
    [Show full text]
  • Compilation of Reported Sapphire Occurrences in Montana
    Report of Investigation 23 Compilation of Reported Sapphire Occurrences in Montana Richard B. Berg 2015 Cover photo by Richard Berg. Sapphires (very pale green and colorless) concentrated by panning. The small red grains are garnets, commonly found with sapphires in western Montana, and the black sand is mainly magnetite. Compilation of Reported Sapphire Occurrences, RI 23 Compilation of Reported Sapphire Occurrences in Montana Richard B. Berg Montana Bureau of Mines and Geology MBMG Report of Investigation 23 2015 i Compilation of Reported Sapphire Occurrences, RI 23 TABLE OF CONTENTS Introduction ............................................................................................................................1 Descriptions of Occurrences ..................................................................................................7 Selected Bibliography of Articles on Montana Sapphires ................................................... 75 General Montana ............................................................................................................75 Yogo ................................................................................................................................ 75 Southwestern Montana Alluvial Deposits........................................................................ 76 Specifi cally Rock Creek sapphire district ........................................................................ 76 Specifi cally Dry Cottonwood Creek deposit and the Butte area ....................................
    [Show full text]
  • ANNUAL REPORT and ACCOUNTS 2018 Gem Diamonds Is a Leading Producer of High-Value Diamonds
    ANNUAL REPORT AND ACCOUNTS 2018 Gem Diamonds is a leading producer of high-value diamonds The Group, which has its head office in the United Kingdom, owns the Letšeng mine in Lesotho and the Ghaghoo mine in Botswana. The Letšeng mine is renowned for its regular On the cover, the 910 carat Lesotho production of large, exceptional white diamonds, making it the Legend recovered in January 2018, highest average dollar per carat kimberlite diamond mine in largest gem quality diamond ever recovered at Letšeng. the world. Since Gem Diamonds acquired the mine in 2006, Letšeng has produced some of the world’s most remarkable Welcome to the Gem diamonds. Among these diamonds recovered are the 910 carat Diamonds Annual Report Lesotho Legend, the 603 carat Lesotho Promise, the 550 carat and Accounts 2018 Letšeng Star and the 493 carat Letšeng Legacy. The Annual Report and Accounts have been prepared in accordance Gem Diamonds’ strategy is underpinned by three key priorities with: to deliver maximum value for all shareholders through its – applicable English and British Virgin Islands law; business cycle. Its current focus is on enhancing the efficiency – regulations and best practice as of the Group’s operations by improving day-to-day advised by the Financial performance, driving stringent cost control and capital Reporting Council and the discipline; and selling non-core assets. The selling of diamonds Department of Business, is supported by the Group’s sales, marketing and manufacturing Innovation and Skills in the United Kingdom; and capabilities. Financial, technical and administrative services are – International Financial supported by its South African subsidiary.
    [Show full text]
  • A Review on Historical Earth Pigments Used in India's Wall Paintings
    heritage Review A Review on Historical Earth Pigments Used in India’s Wall Paintings Anjali Sharma 1 and Manager Rajdeo Singh 2,* 1 Department of Conservation, National Museum Institute, Janpath, New Delhi 110011, India; [email protected] 2 National Research Laboratory for the Conservation of Cultural Property, Aliganj, Lucknow 226024, India * Correspondence: [email protected] Abstract: Iron-containing earth minerals of various hues were the earliest pigments of the prehistoric artists who dwelled in caves. Being a prominent part of human expression through art, nature- derived pigments have been used in continuum through ages until now. Studies reveal that the primitive artist stored or used his pigments as color cakes made out of skin or reeds. Although records to help understand the technical details of Indian painting in the early periodare scanty, there is a certain amount of material from which some idea may be gained regarding the methods used by the artists to obtain their results. Considering Indian wall paintings, the most widely used earth pigments include red, yellow, and green ochres, making it fairly easy for the modern era scientific conservators and researchers to study them. The present knowledge on material sources given in the literature is limited and deficient as of now, hence the present work attempts to elucidate the range of earth pigments encountered in Indian wall paintings and the scientific studies and characterization by analytical techniques that form the knowledge background on the topic. Studies leadingto well-founded knowledge on pigments can contribute towards the safeguarding of Indian cultural heritage as well as spread awareness among conservators, restorers, and scholars.
    [Show full text]
  • GSA TODAY Conference, P
    Vol. 10, No. 2 February 2000 INSIDE • GSA and Subaru, p. 10 • Terrane Accretion Penrose GSA TODAY Conference, p. 11 A Publication of the Geological Society of America • 1999 Presidential Address, p. 24 Continental Growth, Preservation, and Modification in Southern Africa R. W. Carlson, F. R. Boyd, S. B. Shirey, P. E. Janney, Carnegie Institution of Washington, 5241 Broad Branch Road, N.W., Washington, D.C. 20015, USA, [email protected] T. L. Grove, S. A. Bowring, M. D. Schmitz, J. C. Dann, Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA D. R. Bell, J. J. Gurney, S. H. Richardson, M. Tredoux, A. H. Menzies, Department of Geological Sciences, University of Cape Town, Rondebosch 7700, South Africa D. G. Pearson, Department of Geological Sciences, Durham University, South Road, Durham, DH1 3LE, UK R. J. Hart, Schonland Research Center, University of Witwater- srand, P.O. Box 3, Wits 2050, South Africa A. H. Wilson, Department of Geology, University of Natal, Durban, South Africa D. Moser, Geology and Geophysics Department, University of Utah, Salt Lake City, UT 84112-0111, USA ABSTRACT To understand the origin, modification, and preserva- tion of continents on Earth, a multidisciplinary study is examining the crust and upper mantle of southern Africa. Xenoliths of the mantle brought to the surface by kimber- lites show that the mantle beneath the Archean Kaapvaal Figure 2. Bouguer gravity image (courtesy of South African Council for Geosciences) craton is mostly melt-depleted peridotite with melt extrac- across Vredefort impact structure, South Africa. Color scale is in relative units repre- senting total gravity variation of 90 mgal across area of figure.
    [Show full text]