Summer 2004 Gems & Gemology
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The Dependence of the Sio Bond Length on Structural Parameters in Coesite, the Silica Polymorphs, and the Clathrasils
American Mineralogist, Volume 75, pages 748-754, 1990 The dependence of the SiO bond length on structural parameters in coesite, the silica polymorphs, and the clathrasils M. B. BOISEN, JR. Department of Mathematics, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, U.S.A. G. V. GIBBS, R. T. DOWNS Department of Geological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, U.S.A. PHILIPPE D' ARCO Laboratoire de Geologie, Ecole Normale Superieure, 75230 Paris Cedex OS, France ABSTRACT Stepwise multiple regression analyses of the apparent R(SiO) bond lengths were com- pleted for coesite and for the silica polymorphs together with the clathrasils as a function of the variables};(O), P (pressure), f,(Si), B(O), and B(Si). The analysis of 94 bond-length data recorded for coesite at a variety of pressures and temperatures indicates that all five of these variables make a significant contribution to the regression sum of squares with an R2 value of 0.84. A similar analysis of 245 R(SiO) data recorded for silica polymorphs and clathrasils indicate that only three of the variables (B(O), };(O), and P) make a signif- icant contribution to the regression with an R2 value of 0.90. The distribution of B(O) shows a wide range of values from 0.25 to 10.0 A2 with nearly 80% of the observations clustered between 0.25 and 3.0 A2 and the remaining values spread uniformly between 4.5 and 10.0 A2. A regression analysis carried out for these two populations separately indicates, for the data set with B(O) values less than three, that };(O) B(O), P, and };(Si) are all significant with an R2 value of 0.62. -
Crystalline Silica, Cristobalite (CAS No
Crystalline Silica, Quartz (CAS No. 14808-60-7) Crystalline Silica, Cristobalite (CAS No. 14464-46-1) Crystalline Silica, Tridymite (CAS No. 15468-32-3) Diatomaceous earth (CAS No. 61790-53-2) This dossier on crystalline silica, quartz, cristobalite and tridymite and diatomaceous earth presents the most critical studies pertinent to the risk assessment of these substances in their use in drilling muds and cement additives. This dossier does not represent an exhaustive or critical review of all available data. The majority of information presented in this dossier was obtained from the ECHA database that provides information on chemicals that have been registered under the EU REACH (ECHA). Where possible, study quality was evaluated using the Klimisch scoring system (Klimisch et al., 1997). For the purpose of this dossier, crystalline silica, quartz (CAS No. 14808-60-7) has been reviewed as representative of crystalline silica cristobalite and tridymite. Crystalline silica, quartz is also considered representative of diatomaceous earth, as they both consist mainly of silicon dioxide. Screening Assessment Conclusion – Crystalline silica, quartz, cristobalite and tridymite and diatomaceous earth are classified as tier 1 chemicals and require a hazard assessment only. 1 BACKGROUND Crystalline silica is a common mineral found in the earth's crust. Materials like sand, stone, concrete and mortar contain crystalline silica. It is also used to make products such as glass, pottery, ceramics, bricks and artificial stone. Silica, in the form of sand, is used as the main ingredient in sand casting for the manufacture of metallic components in engineering and other applications. The high melting point of silica enables it to be used in such applications. -
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. -
Minnesota's Mineral Resources
CHAPTER • 9 Minnesota's Mineral Resources IN MINNESOTA the production of iron ore is far more valuable economically than the total of all other mineral products, but im portant industries are based on Minnesota's other geological forma tions as well. Architectural, monumental, and structural stone are produced from granite, limestone, dolomite, and other Minnesota rocks. Gravel and sand are excavated and processed, and clay is used for many ceramic products. :Manganese in important amounts occurs in the iron ores of the Cuyuna district. Finally, although they are often not thought of as mineral products, two of our most im portant mineral resources are water and soil. The iron ores and mining operations of the Mesabi, Vermilion, and Cuyuna iron-bearing districts and of the southeastern lYlinnesota counties will be discussed in detail in later chapters, but a few sta tistics on Minnesota's iron ore industry may remind us how impor tant this geological heritage is. The following is an estimate of Min nesota's iron ore reserves, made on lYlay 1, 1961: Gross Tons Mesabi Range 500,799,179 Vermilion Range 9,755,974 Cuyuna Range 36,530,000 Fillmore County 'il,860,337 Total iron ore 549,945,490 172 MI NESOTA'S MINERAL RESOURCES The total production of iron ore in Minne ota to January 1, 1962, was 2,529,737,553 tons. Total taxes paid on iron ore to January 1, 1961 , were approximately $1,257,448,400, a very important source of funds for the state government. Slightly over 60 per cent of the total iron ore produced in the United States has come from l\1inne- ota. -
The New IMA List of Gem Materials – a Work in Progress – Updated: July 2018
The New IMA List of Gem Materials – A Work in Progress – Updated: July 2018 In the following pages of this document a comprehensive list of gem materials is presented. The list is distributed (for terms and conditions see below) via the web site of the Commission on Gem Materials of the International Mineralogical Association. The list will be updated on a regular basis. Mineral names and formulae are from the IMA List of Minerals: http://nrmima.nrm.se//IMA_Master_List_%282016-07%29.pdf. Where there is a discrepancy the IMA List of Minerals will take precedence. Explanation of column headings: IMA status: A = approved (it applies to minerals approved after the establishment of the IMA in 1958); G = grandfathered (it applies to minerals discovered before the birth of IMA, and generally considered as valid species); Rd = redefined (it applies to existing minerals which were redefined during the IMA era); Rn = renamed (it applies to existing minerals which were renamed during the IMA era); Q = questionable (it applies to poorly characterized minerals, whose validity could be doubtful). Gem material name: minerals are normal text; non-minerals are bold; rocks are all caps; organics and glasses are italicized. Caveat (IMPORTANT): inevitably there will be mistakes in a list of this type. We will be grateful to all those who will point out errors of any kind, including typos. Please email your corrections to [email protected]. Acknowledgments: The following persons, listed in alphabetic order, gave their contribution to the building and the update of the IMA List of Minerals: Vladimir Bermanec, Emmanuel Fritsch, Lee A. -
Symposium on Agate and Cryptocrystalline Quartz
Symposium on Agate and Cryptocrystalline Quartz September 10 – 13, 2005 Golden, Colorado Sponsored by Friends of Mineralogy, Colorado Chapter; Colorado School of Mines Geology Museum; and U.S. Geological Survey 2 Cover Photos {top left} Fortification agate, Hinsdale County, Colorado, collection of the Geology Museum, Colorado School of Mines. Coloration of alternating concentric bands is due to infiltration of Fe with groundwater into the porous chalcedony layers, leaving the impermeable chalcedony bands uncolored (white): ground water was introduced via the symmetric fractures, evidenced by darker brown hues along the orthogonal lines. Specimen about 4 inches across; photo Dan Kile. {lower left} Photomicrograph showing, in crossed-polarized light, a rhyolite thunder egg shell (lower left) a fibrous phase of silica, opal-CTLS (appearing as a layer of tan fibers bordering the rhyolite cavity wall), and spherulitic and radiating fibrous forms of chalcedony. Field of view approximately 4.8 mm high; photo Dan Kile. {center right} Photomicrograph of the same field of view, but with a 1 λ (first-order red) waveplate inserted to illustrate the length-fast nature of the chalcedony (yellow-orange) and the length-slow character of the opal CTLS (blue). Field of view about 4.8 mm high; photo Dan Kile. Copyright of articles and photographs is retained by authors and Friends of Mineralogy, Colorado Chapter; reproduction by electronic or other means without permission is prohibited 3 Symposium on Agate and Cryptocrystalline Quartz Program and Abstracts September 10 – 13, 2005 Editors Daniel Kile Thomas Michalski Peter Modreski Held at Green Center, Colorado School of Mines Golden, Colorado Sponsored by Friends of Mineralogy, Colorado Chapter Colorado School of Mines Geology Museum U.S. -
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. -
THE HANDBOOK for STORYTELLERS and the Handbook for Storytime Programs) Stands on Its Own, Each Complements and Buttresses the Other
THE HANDBOOK FOR JUDY FREEMAN and CAROLINE FELLER BAUER An imprint of the American Library Association CHICAGO 2015 www.alastore.ala.org Caroline Feller Bauer (1935–2013) was a public librarian, professor of children’s literature, radio personality, international speaker and performer, author of nineteen children’s books and professional books about children’s literature for adults, and tireless cheerleader for literacy and storytelling. Judy Freeman (www.judyreadsbooks.com) is a former school librarian; an adjunct professor at Pratt Institute in New York City, teaching courses in children’s literature and storytelling; an international speaker and performer for children, teachers, librarians, and parents; a children’s book reviewer; and the author of more than a dozen professional books about children’s literature and storytelling. She continues to work closely with librarians, teachers, and hundreds of students at several elementary schools to test out new books, ideas, and ways to incorporate literature into children’s lives. Both have developed and performed thousands of programs and workshops incorporating children’s literature, storytelling, music, poetry, and drama to tens of thousands of children and adults across the United States and abroad. © 2015 by Judy Freeman and Caroline Feller Bauer Printed in the United States of America 19 18 17 16 15 5 4 3 2 1 Extensive effort has gone into ensuring the reliability of the information in this book; however, the publisher makes no warranty, express or implied, with respect to the mate- rial contained herein. All reasonable efforts have been made to identify and contact copyright holders, but in some cases these could not be traced. -
Winter 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, Geneva, Switzerland ([email protected]) Kenneth V. G. Scarratt, GIA Research, Bangkok, Thailand ([email protected]) DIAMONDS Angola and the Democratic Republic of Congo. This situ- Update on Diamond Trading in Sierra Leone. During the ation led to the Kimberley Process for certifying dia- decade-long civil war in Sierra Leone, the Revolutionary monds from mine to market, which was implemented in United Front (RUF) rebel army committed widespread 2002. With the signing of the Lomé Peace Agreement atrocities against innocent civilians, drawing global con- between the Sierra Leone government and the RUF earlier demnation by governments, human rights groups, and that year, peace has returned to the country. concerned citizens. The RUF was partially funded by the In August 2006, GIA Education instructor Ric Taylor country’s diamond resources, bringing the issue of con- traveled through the Sierra Leone diamond mining areas of flict diamonds in Sierra Leone to world attention in the Koidu, Tongo, Kenema, and Bo, some of which were once late 1990s. Meanwhile, similar diamond-funded conflicts controlled by the rebels. He saw no evidence of continuing were being waged in other African nations, such as conflict, and residents and journalists in these areas con- firmed that there is no desire to return to war. In the town of Koidu (figure 1), in the diamond mining district of Kono Figure 1. The town of Koidu, in the Kono district of in eastern Sierra Leone, one can still see the bare walls of eastern Sierra Leone, was at the center of the county’s buildings that were looted and burned, but many others protracted conflict because of the area’s diamond have been rebuilt and have roofs of corrugated metal or resources. -
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). -
John S. White Mineral and Gem Collections GENERAL Nephrite Boulder – Trinity County, California Pyrite Navajun, Logroño, Spain 20-11-3
John S. White Mineral and Gem Collections GENERAL Nephrite boulder – Trinity County, California Pyrite Navajun, Logroño, Spain 20-11-3 12 cm Figured specimen (12) Beryl var. emerald – Crabtree Mountain emerald mine, Mitchell Co., N.C. G5-9-12 5 cm Ocean jasper – Cabamby mine, Majunga, Madagascar – G10-9-1 4.3 cm Ocean jasper – Cabamby mine, Majunga, Madagascar G11-2-3 4 cm Andalusite, variety chiastolite – China 10-2-43 2.7 cm Graphic granite – Madagascar 17-9-3 4.5 cm Garnet color suite – mixed localities G8-11-1 Sasha Siemel Beryl Jaguar hunter Governador Valadares & Minas Gerais, Brazil Mineral dealer 19-4-2 & 19-5-4 These specimens were sold by Sasha Siemel to friends of mine at a mineral show in Doylestown, PA, 1956 Gas bubble in fluorite Cave-in-Rock, Illinois 4-12-3 Russell Feather photo Regional Collection Pennsylvania – Maryland - Virginia Magnetite – Grace mine, Morgantown, PA 4-6-1 6.5 cm Rutile – Parkesburg, Chester County, PA 3-9-16 5 cm Dolomite - Ober & Binkley quarry, E. Petersburg, Lancaster Co., PA 17-2-6 10.5 cm Pyromorphite – Wheatley mine, Phoenixville, Chester Co., PA 6-6-9 9 cm Analcime & Apophyllite – Cornwall mine, Cornwall, Lebanon County, PA 20-10-15 10 cm Quartz – Reading anthracite mine, near St. Clair, Schuykill Co., PA 19-9-7 10 cm Fluorapatite & Actinolite – Silver Hill quarry, Brecknock Twp., Lancaster Co., PA 18-2-18 11.5 cm Wavellite – Mt. Pleasant Mills quarry, Perry Twp., Snyder Co., PA 18-2-19 4 cm Strontianite – Oak Hill quarry, Centre County, PA 21-11-1 5.5 cm Strontianite – Tonoloway limestone, Mt. -
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