Rendering Precious Gems
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Summer 2006 Gems & Gemology Gem News
EDITOR Brendan M. Laurs ([email protected]) CONTRIBUTING EDITORS Emmanuel Fritsch, IMN, University of Nantes, France ([email protected]) Henry A. Hänni, SSEF, Basel, Switzerland ([email protected]) Franck Notari, GIA GemTechLab, Geneva, Switzerland ([email protected]) Kenneth V. G. Scarratt, GIA Research, Bangkok, Thailand ([email protected]) COLORED STONES AND tusk fragments. The amber in figure 1 was eventually ORGANIC MATERIALS acquired by Barry Schenck of M. M. Schenck Jeweler Inc., Chattanooga, Tennessee, who recently loaned it to GIA for Alaskan amber. Few may think of Alaska as a source of examination. Mr. Schenck has counted more than 30 amber, but the Inuit people have long collected this organ- insects trapped inside the piece, as well as other organic ic gem from northern beach gravels between Harrison Bay materials, including an apparent seedpod. GIA subsequent- and Smith Bay on the Arctic Ocean. In Gemstones of ly purchased the piece (Collection no. 35840). North America (D. Van Nostrand Co., Princeton, NJ, Most of the insects were eye-visible, though others 1959), J. Sinkankas noted that locals refer to the amber as were best seen with magnification (up to 40×). Prominent auma, which translates as “live coal.” were a mosquito, spiders, beetles, gnats, ants, and possibly In 1943, an American soldier stationed in Alaska found a bee (see, e.g., figure 2). Other inclusions consisted of gas a 117.8 g chunk of amber (figure 1) while strolling along bubbles and debris that was probably associated with the the coast. Subsequent visits to the area yielded other trees from which the amber formed. -
Pezzottaite from Ambatovita, Madagascar: a New Gem Mineral
PEZZOTTAITE FROM AMBATOVITA, MADAGASCAR: A NEW GEM MINERAL Brendan M. Laurs, William B. (Skip) Simmons, George R. Rossman, Elizabeth P. Quinn, Shane F. McClure, Adi Peretti, Thomas Armbruster, Frank C. Hawthorne, Alexander U. Falster, Detlef Günther, Mark A. Cooper, and Bernard Grobéty Pezzottaite, ideally Cs(Be2Li)Al2Si6O18, is a new gem mineral that is the Cs,Li–rich member of the beryl group. It was discovered in November 2002 in a granitic pegmatite near Ambatovita in cen- tral Madagascar. Only a few dozen kilograms of gem rough were mined, and the deposit appears nearly exhausted. The limited number of transparent faceted stones and cat’s-eye cabochons that have been cut usually show a deep purplish pink color. Pezzottaite is distinguished from beryl by its higher refractive indices (typically no=1.615–1.619 and ne=1.607–1.610) and specific gravity values (typically 3.09–3.11). In addition, the new mineral’s infrared and Raman spectra, as well as its X-ray diffraction pattern, are distinctive, while the visible spectrum recorded with the spec- trophotometer is similar to that of morganite. The color is probably caused by radiation-induced color centers involving Mn3+. eginning with the 2003 Tucson gem shows, (Be3Sc2Si6O18; Armbruster et al., 1995), and stoppaniite cesium-rich “beryl” from Ambatovita, (Be3Fe2Si6O18; Ferraris et al., 1998; Della Ventura et Madagascar, created excitement among gem al., 2000). Pezzottaite, which is rhombohedral, is Bcollectors and connoisseurs due to its deep purplish not a Cs-rich beryl but rather a new mineral species pink color (figure 1) and the attractive chatoyancy that is closely related to beryl. -
Phenomenal Gemstones Possess Striking Optical Effects, Making Them Truly a Sight for Sore Eyes
THE PHENOMENAL PROPERTIES OF GEMS Phenomenal gemstones possess striking optical effects, making them truly a sight for sore eyes. Here is GIA’s guide to understanding what makes each phenomenon so uniquely brilliant. ASTERISM CROSSING BANDS OF REFLECTED LIGHT CREATE A SIX-RAYED STAR-LIKE APPEARANCE. ASTERISM OCCURS IN THE DOME OF A CABOCHON, AND CAN BE SEEN IN GEMS LIKE RUBIES AND SAPPHIRES. ADULARESCENCE THE SAME SCATTERING OF LIGHT THAT MAKES THE SKY BLUE CREATES A MILKY, BLUISH-WHITE GLOW, LIKE MOONLIGHT SHINING THROUGH A VEIL OF CLOUDS. MOONSTONE IS THE ONLY GEM THAT DISPLAYS IT. AVENTURESCENCE FOUND IN NATURAL GEMS LIKE SUNSTONE FELDSPAR AND AVENTURINE QUARTZ, IT DISPLAYS A GLITTERY EFFECT CAUSED BY LIGHT REFLECTING FROM SMALL, FLAT INCLUSIONS. CHATOYANCY OTHERWISE KNOWN AS THE “CAT’S EYE” EFFECT, BANDS OF LIGHT ARE CAUSED BY THE REFLECTION OF LIGHT FROM MANY PARALLEL, NEEDLE-LIKE INCLUSIONS INSIDE A CABOCHON. NOTABLE GEMS THAT DISPLAY CHATOYANCY INCLUDE CAT’S EYE TOURMALINE AND CAT’S EYE CHRYSOBERYL. IRIDESCENCE ALSO SEEN IN SOAP BUBBLES AND OIL SLICKS, IT’S A RAINBOW EFFECT THAT IS CREATED WHEN LIGHT IS BROKEN UP INTO DIFFERENT COLORS. LOOK FOR IT IN FIRE AGATE AND OPAL AMMONITE (KNOWN BY THE TRADE AS AMMOLITE). LABR ADORESCENCE A BROAD FLASH OF COLOR THAT APPEARS IN LABRADORITE FELDSPAR, IT’S CAUSED BY LIGHT INTERACTING WITH THIN LAYERS IN THE STONE, AND DISAPPEARS WHEN THE GEM IS MOVED. INSIDER’S TIP: THE MOST COMMON PHENOMENAL COLOR IN LABRADORITE IS BLUE. PLAY OF COLOR THE FLASHING RAINBOW-LIKE COLORS IN OPAL THAT FLASH AT YOU AS YOU TURN THE STONE OR MOVE AROUND IT. -
SOME UNUSUAL SILLIMANITE CAT's-EYES by E
NOTES AND NEW TECHNIQUES SOME UNUSUAL SILLIMANITE CAT'S-EYES By E. Giibelin, M, Weibel, and C. P. Woensdregt Brown-black sillimanite cat's-eyes from Sri Lanka thin-section study and the ion etching necessary present an unusually sharp band, which would make for subsequent electron diffraction. them extraordinary gems wereit not for therather un- This article summarizes the results of the elec- attractive body color of the stones. A study of six of tron microscope study of the inclusions causing these stones found that they contain 0.5 wt.% iron the chatoyancy, as well as the gemological charac- oxide. The principal inclusion mineral is ilmenite, teristics of this unusual material. which occurs in elongated, submicroscopically thin lamellae. Complex thicker lamellae consist of hercy- EXPERIMENTAL METHODS nite spinel grown together with a member of the pyroxene group. These thicker inclusions were not Chatoyancy, like asterism, is caused by the scat- foundin all of the specimens investigated. tering of light on numerous fibrous inclusions aligned in one or more directions in the host crys- tal; proper cutting en cabochon is required to re- veal the phenomenon. For good chatoyancy or asterism, the elongated inclusions must be thin sillimanite, also known as fibrolite, is a common compared to the wavelengths of light (Weibel, metamorphic mineral. Cuttable material is ex- 1985). Such minute crystal individuals are not ac- tremely rare but is found in the Mogok Stone Tract cessible to ordinary microscopy and X-ray analy- of Burma and in the Sri Lankan gem gravels, as sis. Even though the inclusions may show up in a transparent rounded crystals with a blue, violet- thin section viewed with a polarizing microscope, blue, or grayish green hue (Webster, 1983). -
Autumn 07 Cover
Winter Antiques & Fine Art Auction Wednesday 28, Thursday 29 £5 & Friday 30 November 2018 ewbank’s auction sale dates 2018/19 Viewing days/times vary, please contact the auctioneer for details December 2018 August Thursday 13th Toys & Models Wednesday 7th Antique & Collectors inc. Silver Thursday 13th Entertainment & Memorabilia Wednesday 21st Antique & Collectors inc. Silver Friday 14th Vintage Posters Wednesday 21st Garden Furniture & Statuary Wednesday 19th Antique & Collectors’ Thursday 22nd Militaria, Stamps, Books & Maps Wednesday 19th Fine Wines & Spirits September January Wednesday 11th Jewellery, Watches & Coins Wednesday 16th Antique & Collectors inc. Silver Thursday 12th Silver & Fine Art Thursday 17th Decorative Arts Friday 13th Antique Furniture & Clocks Thursday 17th Contemporary Art & Modern British Paintings October February Wednesday 2nd Antique & Collectors inc. Jewellery & Silver Thursday 007th Bond & Beyond Wednesday 2nd Toys & Models Wednesday 13th Antique & Collectors inc. Silver Thursday 3rd Entertainment & Memorabilia Thursday 14th Militaria, Stamps, Books & Maps Thursday 3rd Movie Props Wednesday 27th Toys & Models Friday 4th Vintage Posters Thursday 28th Entertainment & Memorabilia Thursday 24th Decorative Arts Thursday 28th Movie Props Thursday 24th Contemporary Art & Modern British Paintings March November Friday 1st Vintage Posters Wednesday 6th Antique & Collectors inc. Silver Wednesday 6th Antique & Collectors inc. Silver Thursday 7th Asian Art Wednesday 20th Jewellery, Watches & Coins Thursday 7th Vintage -
Mineral Collecting Sites in North Carolina by W
.'.' .., Mineral Collecting Sites in North Carolina By W. F. Wilson and B. J. McKenzie RUTILE GUMMITE IN GARNET RUBY CORUNDUM GOLD TORBERNITE GARNET IN MICA ANATASE RUTILE AJTUNITE AND TORBERNITE THULITE AND PYRITE MONAZITE EMERALD CUPRITE SMOKY QUARTZ ZIRCON TORBERNITE ~/ UBRAR'l USE ONLV ,~O NOT REMOVE. fROM LIBRARY N. C. GEOLOGICAL SUHVEY Information Circular 24 Mineral Collecting Sites in North Carolina By W. F. Wilson and B. J. McKenzie Raleigh 1978 Second Printing 1980. Additional copies of this publication may be obtained from: North CarOlina Department of Natural Resources and Community Development Geological Survey Section P. O. Box 27687 ~ Raleigh. N. C. 27611 1823 --~- GEOLOGICAL SURVEY SECTION The Geological Survey Section shall, by law"...make such exami nation, survey, and mapping of the geology, mineralogy, and topo graphy of the state, including their industrial and economic utilization as it may consider necessary." In carrying out its duties under this law, the section promotes the wise conservation and use of mineral resources by industry, commerce, agriculture, and other governmental agencies for the general welfare of the citizens of North Carolina. The Section conducts a number of basic and applied research projects in environmental resource planning, mineral resource explora tion, mineral statistics, and systematic geologic mapping. Services constitute a major portion ofthe Sections's activities and include identi fying rock and mineral samples submitted by the citizens of the state and providing consulting services and specially prepared reports to other agencies that require geological information. The Geological Survey Section publishes results of research in a series of Bulletins, Economic Papers, Information Circulars, Educa tional Series, Geologic Maps, and Special Publications. -
Thirty-Fourth List of New Mineral Names
MINERALOGICAL MAGAZINE, DECEMBER 1986, VOL. 50, PP. 741-61 Thirty-fourth list of new mineral names E. E. FEJER Department of Mineralogy, British Museum (Natural History), Cromwell Road, London SW7 5BD THE present list contains 181 entries. Of these 148 are Alacranite. V. I. Popova, V. A. Popov, A. Clark, valid species, most of which have been approved by the V. O. Polyakov, and S. E. Borisovskii, 1986. Zap. IMA Commission on New Minerals and Mineral Names, 115, 360. First found at Alacran, Pampa Larga, 17 are misspellings or erroneous transliterations, 9 are Chile by A. H. Clark in 1970 (rejected by IMA names published without IMA approval, 4 are variety because of insufficient data), then in 1980 at the names, 2 are spelling corrections, and one is a name applied to gem material. As in previous lists, contractions caldera of Uzon volcano, Kamchatka, USSR, as are used for the names of frequently cited journals and yellowish orange equant crystals up to 0.5 ram, other publications are abbreviated in italic. sometimes flattened on {100} with {100}, {111}, {ill}, and {110} faces, adamantine to greasy Abhurite. J. J. Matzko, H. T. Evans Jr., M. E. Mrose, lustre, poor {100} cleavage, brittle, H 1 Mono- and P. Aruscavage, 1985. C.M. 23, 233. At a clinic, P2/c, a 9.89(2), b 9.73(2), c 9.13(1) A, depth c.35 m, in an arm of the Red Sea, known as fl 101.84(5) ~ Z = 2; Dobs. 3.43(5), D~alr 3.43; Sharm Abhur, c.30 km north of Jiddah, Saudi reflectances and microhardness given. -
SSEF FACETTE No. 12 SWISS GEMMOLOGICAL INSTITUTE SCHWEIZERISCHES GEMMOLOGISCHES INSTITUT INSTITUT SUISSE DE GEMMOLOGIE
SSEF FACETTE No. 12 SWISS GEMMOLOGICAL INSTITUTE SCHWEIZERISCHES GEMMOLOGISCHES INSTITUT INSTITUT SUISSE DE GEMMOLOGIE International Issue No. 12, January 2005 Reproduction allowed with reference to the Swiss Gemmological Institute SSEF In this Issue: - Diamonds are forever - New Diamond Courses 2005 - Coral en Vogue - LIBS in Gemmology - Lead glass in Ruby - New: Launching of SSEF Alumni - News from CIBJO and LMHC - GemmoBasel 2005 SSEF Facette No. 12, © 2005 Editorial Dear Reader The year 2004 was again packed with many inter- pearl research in China, instrumental development esting challenges for the SSEF laboratory but also in Florida, diamond conference in England, SSEF for the trade. We are lucky that business for the is always on the edge. And you may profit from SSEF was much better than predicted under tight this: SSEF is proud to have found a new analyti- general conditions. The high performance and the cal solution for the detection of beryllium diffusion degree of integrity of the SSEF is appreciated by a treated sapphires, which caused so much concern number of well-known international companies. We and “headache” to the international gem trade. The notice with pleasure that our origin determinations SSEF is the first laboratory offering an inexpensive and treatment identifications form an important part and reliable Be detection service. of our activity and strongly influence the price of a gem. Reliable SSEF We are glad to offer you the SSEF Facette in a new Test Reports for pearls and colourful look. We are continuing to produce guarantee the trade with this newsletter in three languages: German, French sometimes extremely and English. -
The Origins of Color in Minerals Four Distinct Physical Theories
American Mineralogist, Volume 63. pages 219-229, 1978 The origins of color in minerals KURT NASSAU Bell Laboratories Murray Hill, New Jersey 07974 Abstract Four formalisms are outlined. Crystal field theory explains the color as well as the fluores- cence in transition-metal-containing minerals such as azurite and ruby. The trap concept, as part of crystal field theory, explains the varying stability of electron and hole color centers with respect to light or heat bleaching, as well as phenomena such as thermoluminescence. The molecular orbital formalism explains the color of charge transfer minerals such as blue sapphire and crocoite involving metals, as well as the nonmetal-involving colors in lazurite, graphite and organically colored minerals. Band theory explains the colors of metallic minerals; the color range black-red-orange- yellow-colorless in minerals such as galena, proustite, greenockite, diamond, as well as the impurity-caused yellow and blue colors in diamond. Lastly, there are the well-known pseudo- chromatic colors explained by physical optics involving dispersion, scattering, interference, and diffraction. Introduction The approach here used is tutorial in nature and references are given for further reading or, in some Four distinct physical theories (formalisms) are instances, for specific examples. Color illustrations of required for complete coverage in the processes by some of the principles involved have been published which intrinsic constituents, impurities, defects, and in an earlier less technical version (Nassau, 1975a). specific structures produce the visual effects we desig- Specific examples are given where the cause of the nate as color. All four are necessary in that each color is reasonably well established, although reinter- provides insights which the others do not when ap- pretations continue to appear even in materials, such plied to specific situations. -
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. -
Beryllium Diffusion of Ruby and Sapphire John L
VOLUME XXXIX SUMMER 2003 Featuring: Beryllium Diffusion of Rubies and Sapphires Seven Rare Gem Diamonds THE QUARTERLY JOURNAL OF THE GEMOLOGICAL INSTITUTE OF AMERICA Summer 2003 VOLUME 39, NO. 2 EDITORIAL _____________ 83 “Disclose or Be Disclosed” William E. Boyajian FEATURE ARTICLE _____________ pg. 130 84 Beryllium Diffusion of Ruby and Sapphire John L. Emmett, Kenneth Scarratt, Shane F. McClure, Thomas Moses, Troy R. Douthit, Richard Hughes, Steven Novak, James E. Shigley, Wuyi Wang, Owen Bordelon, and Robert E. Kane An in-depth report on the process and characteristics of beryllium diffusion into corundum. Examination of hundreds of Be-diffused sapphires revealed that, in many instances, standard gemological tests can help identify these treated corundums. NOTES AND NEW TECHNIQUES _______ 136 An Important Exhibition of Seven Rare Gem Diamonds John M. King and James E. Shigley A look at the background and some gemological observations of seven important diamonds on display at the Smithsonian Institution from June to September 2003, in an exhibit titled “The Splendor of Diamonds.” pg. 137 REGULAR FEATURES _____________________ 144 Lab Notes • Vanadium-bearing chrysoberyl • Brown-yellow diamonds with an “amber center” • Color-change grossular-andradite from Mali • Glass imitation of tsavorite • Glass “planetarium” • Guatemalan jade with lawsonite inclusions • Chatoyant play-of-color opal • Imitation pearls with iridescent appearance • Sapphire/synthetic color-change sapphire doublets • Unusual “red” spinel • Diffusion-treated tanzanite? -
Star Stones (Asterism)
Learning Series: Basic Rockhound Knowledge Star Stones (Asterism) When parallel, needle-like inclusions, or tube-like channels, are oriented along two or more of the crystal faces of a mineral, and when that stone is cut as a domed cabochon, a four- to six-rayed figure is displayed on the dome. This phenomenon of reflected light is called "asterism" and the gems are called star stones. The most commonly seen examples are star corundums; where there are inclusions of titanium oxide (rutile or "silk") parallel to three crystal faces giving a six-rayed star. In rare cases, a twinned crystal slightly offset with its own set of rutile needles can lead to the formation of a twelve-rayed star. Although rutile is an extremely common inclusion in sapphire, few good, natural, star sapphires are found. One of the major reasons is that the heating, which is almost universally done to sapphire rough, dissolves rutile needles; clarifying and sometimes color enhancing the stone, yes, but eliminating potential stars! [Rutile needles (silk) aligned in three directions in unheated corundum] [Star ruby, white star sapphire ring, rare bi-colored star sapphire] The only other gem which commonly forms stars is quartz, where the phenomenon tends to be more visible in transmitted than in reflected light. In this species, rose quartz is the most frequently asterated variety. Most citrine in commerce has been heated, which tends to dissolve the fine rutile inclusions necessary for star formation, so it is rather rare. In fine, near-transparent quartzes which have been cut to a spherical shape, multiple stars can form an intersecting pattern over the surface.