Cameos of the Rainforest Interview with Martin Rapaport Taking the Strain

Total Page:16

File Type:pdf, Size:1020Kb

Cameos of the Rainforest Interview with Martin Rapaport Taking the Strain Nov/Dec 2015 / Volume 24 / No. 7 Cameos of the rainforest Interview with Martin Rapaport Taking the strain: diamonds under crossed polars The Tucson Gem and Mineral Society Proudly Presents: THE 62ND ANNUAL TUCSON GEM AND MINERAL SHOW® Shades of Blue Minerals of the World Aquamarine Photographer Mark Mauthner Azurite Photographer Joe Budd Tucson Convention Center February 11 - 14, 2016 FEATURING: • Retail Dealers • Special & Guest Exhibits • Educational Area • FREE Lecture Series For more information, visit: www.tgms.org CONTENTS Nov/Dec 2015 / V Nov/Dec 2015 olume 24 / No. 7 Martin Rapaport 9 interview The chairman of the Rapaport group offers his thoughts on the market — past, present and future. Cameo s of the rainf Intervie orest w with Martin Rapaport Taking the strain: diamonds under crossed polar s 12 Polished diamonds: take the strain Cover Picture Grenville Millington FGA looks at diamonds A 0.53 ct rose-cut diamond viewed under under crossed polars. the polariscope with the analyzer in position. See Grenville Millington’s article on ‘The ins and outs of polished diamonds: take the strain’ on page 12. Goldsmiths’ Fair 17 Published by The Gemmological Association 2015 of Great Britain (Gem-A) 21 Ely Place, London EC1N 6TD Kim Foxwell FGA DGA reviews the latest offerings from up-and-coming designers t: +44 (0)20 7404 3334 at this year’s Goldsmiths’ Fair. f: +44 (0)20 7404 8843 e: [email protected] w: www.gem-a.com Registered charity no. 1109555 Copyright 2015 ISSN 1746-8043 Deputy Editor 22 Blue John Georgina Brown Auction Advisory Board Mary Burland, Andrew Fellows, Andrew Fellows FGA DGA discusses the Harry Levy history of Blue John and the results of the auction at Fellows auction house Design and Production on 5 October. Zest Design +44 (0)20 7864 1504 Advertising February 11 - 14, 2016 For mediapack and advertising rates contact Georgina Brown, Deputy Editor, Editor’s Note 5 Recent Events 24 at [email protected]. Gem News 6 Jewellery 26 Gem-A Events 8 Gems & Minerals 28 Any opinions expressed in Gems&Jewellery are • Retail Dealers • Special & Guest Exhibits understood to be the views of the contributors Shows and Exhibitions 20 Museum Collections 32 and are not necessarily those of the publishers. • Educational Area • FREE Lecture Series Auctions 22 Book Shelf 34 For more information, visit: www.tgms.org GEMS&JEWELLERY NOV/DEC 2015 3 Polish yourour knowledgeknowledge Are these diamonds or synthetic moissanites?issanites?issanit s?* If you’reyyouou’re not sure,, sign upup forfoorr ourour world-famous Diamond Diploma, onene off the mostmost comprehensivecocomcomprehensivensiv and valuablevaluv able diamond qualiications worldwide. You will gain a thorough understandingstanding ofof diamondsdiamonds and howhow the diamondddiamoiamondnd marketmar operates; learn about diamond grading, the 4Cs and the other factors that inluence value; study the factors that affect a diamond’siamoiamond’snd’s appearanceappe ance and properties;pr pertierties;ties;s; and will learn how to identify and recognize imitations, synthetics and treatments. Our Diamond Diploma graduates can apply for Membership, entitling them to use the prestigious DGA post-nominal letters — a mark of excellence in the trade. For more information or to sign upp contact [email protected]@gem-aedu [email protected]@gem-a.com. * They’re diamonds. JoinJoin us. The Gemmological Association of Great Britain, 21 Ely Place, London, EC1N 6TD, UK. T: +44 (0) 20 7404 3334 F: +44 (0) 20 7404 8843. Registered charity no. 1109555. A company limited by guarantee and registered in England No. 1945780. Registered Ofice: 3rd Floor, 1-4 Argyll Street, London W1F 7LD. EDITORIAL Final thoughts for 2015 Welcome to the November/December issue of Gems&Jewellery. By the time you read this we will have finished our annual Gem-A Conference and the 18th FEEG Symposium, held at the Royal Institute of British Architects in London. This year’s conference was particularly special, as we welcomed delegates and graduates from the Federation for European Education in Gemmology (FEEG). We hope many of you were able to attend and meet with our FEEG delegates, as well as with your colleagues and friends — after all, that is partly what conferences are all about: making new connections in order to share and expand your knowledge. We would like to thank our Sponsors for their generous support, all of whom helped to make this year’s conference truly spectacular. Thank you to our Platinum Sponsors, JTV; our Silver Sponsors AnchorCert GemLab, American Gemological Laboratories, the Canadian Gemmological Association, Gemworld and Marcus McCallum, and our two Bronze Sponsors Fellows Auctioneers and TH March. We diamond qualiications worldwide. would also like to thank our speakers, workshop and trip hosts and all of our delegates for their support and attendance. Look for a report of the conference in operates; learn about diamond grading, the 4Cs and the other factors that inluence the next issue of Gems&Jewellery, published in early 2016. Christmas is now well on its way and, with learn how to identify and recognize imitations, synthetics and treatments. Our Diamond it, a new year and a new start. In the last few months we have welcomed several new Diploma graduates can apply for Membership, entitling them to use the prestigious members of staff to Gem-A, including Fiona — a mark of excellence in the trade. Conway, Finance Manager; Magdalena Nepal, Accounts Assistant and our new interim CEO, Nick Jones. A chartered accountant by trade, Nick brings a wealth of experience to Gem-A, having acted as Head I hope you enjoy this issue of They’re diamonds. of Finance for the Society of Operations Gems&Jewellery. Helen Serras-Herman … after all, that is partly Engineers (SOE) from 2001–2007 and takes a look at two sets of cameos; we as Chief Executive of the SOE from feature a report from the IRV Loughborough what conferences 2007–2013. He is working closely with Conference by Charles Evans and Natalie are all about: making the Gem-A Council and will advise on the Harris; Grenville Millington takes a look at future structure of the Association. Stay diamonds under crossed polars, and we talk new connections tuned for the January/February issue of to diamond titan Martin Rapaport. Gems&Jewellery, which will feature a guest Wishing you all very happy holidays, in order to share editorial from Nick. and best wishes for the New Year ahead. your knowledge. Georgina Brown, Deputy Editor The Gemmological Association of Great Britain, 21 Ely Place, London, EC1N 6TD, UK. T: +44 (0) 20 7404 3334 F: +44 (0) 20 7404 8843. Registered charity no. 1109555. A company limited by guarantee and registered in England No. 1945780. Registered Ofice: 3rd Floor, 1-4 Argyll Street, London W1F 7LD. GEMS&JEWELLERY NOV/DEC 2015 5 GEM NEWS Gem News that there is more work to be done when it COWDRAY PEARLS comes to managing the global diamond supply FETCH TOP SALE PRICE chain. While the vast majority of diamonds The Cowdray Pearls suite — the contribute a significant benefit to the countries necklace strung and mounted by in which they’re produced, as an industry we Cartier and accompanied by a pair of are committed to staying the course until we Cartier-mounted earrings — sold at reach the goal of zero conflict diamonds. Sotheby’s Hong Kong on 7 October “However, the Amnesty International for US$5.27 million. Featured in report ignores the careful and conscientious the Magnificent Jewels and Jadeite framework being put in place in CAR. Interim Autumn Sale, the necklace comprises arrangements regarding future CAR diamond 42 rare, natural, grey saltwater exports and green export zones have been pearls, well-matched in lustre, approved by the Kimberley Process and shape and size. the Civil Society Coalition of the Kimberley The Swiss Gemmological Institute Process Certification Scheme, who have in described the pearls as the “finest addition commissioned an outside company grey pearls in existence” that possess to audit the stockpile. “extraordinary characteristics and merit “We also applaud the Antwerp Diamond special mention and appreciation”. Office’s strict control mechanism for The necklace originally belonged to the each import or export of diamonds. Their Viscountess Cowdray, Lady Pearson, close monitoring led to the interception who died in 1932. Sotheby’s London and seizure in 2014 of two shipments first auctioned the item in 1937. The containing rough diamonds from the Central pearls were displayed at the Andrew Cohen stand at Baselworld 2015, as reported in the African Republic. This is an example of our June issue of Gems&Jewellery (Volume 24, page 31). members’ commitment to ensuring the integrity of the industry.” GIA NOTIFIES TRADE OF WDC CRITICIZES AMNESTY CAR REPORT CIBJO RELEASES CORAL BLUE BOOK INVALIDATED GRADING REPORTS The World Diamond Council (WDC) has issued CIBJO, the World Jewellery Confederation, GIA has invalidated grading reports for a statement in response to the recently has launched online its latest Blue Book, 1,042 diamonds submitted primarily to its published report by Amnesty International delineating acceptable trade practices and grading laboratory in India. An outside party focusing on the global diamond supply chain nomenclature for the coral industry and who gained unauthorized remote access and the Central African Republic (CAR). The trade. The document was compiled by to GIA’s grading information database report claimed diamond trafficking was being the CIBJO Coral Commission, headed by altered the reports. GIA strongly requests used to fund violence in CAR. commission president Enzo Liverino, under that anyone in possession of any of these In its statement, the WDC urges Amnesty the auspices of CIBJO’s Sector A, which has diamonds or grading reports return them International to engage with the Kimberley jurisdiction over gem materials.
Recommended publications
  • 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.
    [Show full text]
  • Elimination of Ferric Ion Effect on Separation Between Kyanite and Quartz Using Citric Acid As Regulator
    minerals Article Elimination of Ferric Ion Effect on Separation between Kyanite and Quartz Using Citric Acid as Regulator Yanping Niu 1, Ya Li 1, Haoran Sun 2,*, Chuanyao Sun 3, Wanzhong Yin 2 and Hongfeng Xu 4 1 Heilongjiang Province Geology Ore Test and Application Institute, Harbin 150000, China; [email protected] (Y.N.); [email protected] (Y.L.) 2 College of Resources and Civil Engineering, Northeastern University, Shenyang 110816, China; [email protected] 3 State Key Laboratory of Mineral Processing, BGRIMM Technology Group, Beijing 100160, China; [email protected] 4 Heilongjiang Mining Group Co., Ltd., Harbin 150000, China; [email protected] * Correspondence: [email protected]; Tel.: +86-188-4250-4743 Abstract: Ferric ions produced during grinding influence the flotation separation between kyanite and quartz adversely. In this study, citric acid was used as a regulator to eliminate the effect of ferric ions on the separation of kyanite from quartz with sodium oleate (NaOL) as a collector. The microflotation test results indicated that the quartz was selectively activated by FeCl3 and maintained significant quartz recovery. However, the citric acid could selectively eliminate the effect of ferric ions on the quartz and minimally influenced the kyanite. Contact angle tests demonstrated that FeCl significantly increased the interaction between NaOL and quartz, resulting in the high 3 hydrophobicity of quartz, and the addition of citric acid made the quartz surface hydrophilic again but slightly influenced the kyanite. Fourier-transform infrared spectroscopy showed that FeCl Citation: Niu, Y.; Li, Y.; Sun, H.; Sun, 3 C.; Yin, W.; Xu, H. Elimination of facilitated NaOL adsorption onto the quartz surface, and the addition of citric acid eliminated the Ferric Ion Effect on Separation activation of FeCl3 on the quartz, resulting in the nonadsorption of NaOL onto the quartz surface.
    [Show full text]
  • Magnificent Jewels Spring 2013 Sale Highlights a 75.36Ct D/If Type Iia (Ex) Briolette Diamond Pendent Necklace Tops the Sale
    PRESS RELEASE | HONG KONG | 7 MAY 2 0 1 3 FOR IMMEDIATE RELEASE MAGNIFICENT JEWELS SPRING 2013 SALE HIGHLIGHTS A 75.36CT D/IF TYPE IIA (EX) BRIOLETTE DIAMOND PENDENT NECKLACE TOPS THE SALE | Magnificent Jewels, Woods Room, May 28, 1:30pm, Sale 3218| Hong Kong – Christie’s Hong Kong will stage its Magnificent Jewels sale on May 28, 2013. Comprising over 290 jewels, the sale is estimated to realize in excess of HK$590 million/US$74 million. Signed pieces from world-class jewelry houses will be presented in the sale. A number of the fine jewels feature distinctive shapes, structures and colour combinations that will attract the attention of collectors with an eye for design. The leading highlight of the sale is a magnificent diamond and coloured diamond pendent necklace. Highlights also extend to an exceptional emerald and diamond necklace, and a ruby and diamond ring. HIGHLIGHTS OF THE SALE With a blend of high-calibre craftsmanship, top-quality stones and unique design characteristics, three masterpieces stand out in this sale. The first, a magnificent diamond and coloured diamond pendent necklace (illustrated right, lot 1706, estimate: HK$66,800,000-98,000,000/US$8,500,000- 12,500,000), has a marquise-cut purplish pink diamond suspending a briolette diamond weighing 75.36 carats, the biggest briolette diamond that has ever appeared in auction. While less than one carat in every 100,000 carats of diamond will be found in a perfect condition, this briolette of imposing size is certified by the Gemological Institute of America (GIA) to be D colour and type IIa, indicating its internally flawless clarity, excellent polish, highest level of chemical purity and exceptional optical transparency.
    [Show full text]
  • Blue Diamond Prices Are on the Rise
    This copy is for your personal, non-commercial use only. To order presentation-ready copies for distribution to your colleagues, clients or customers visit http://www.djreprints.com. https://www.barrons.com/articles/blue-diamond-prices-are-on-the-rise-1518037930 Blue Diamond Prices Are on the Rise By Ariel R. Shapiro Feb. 7, 2018 4:12 p.m. ET The fancy color diamond market is on the upswing, according to a report, with blue diamonds seeing the largest gains. Blue diamonds saw a 5.9% increase in value in the fourth quarter of 2017 in a year-over-year comparison, according to data published on Feb. 1 by the Fancy Color Research Foundation (FCRF). Pink and yellow diamond prices decreased slightly in the same period, at 0.8% and 1.8%, respectively. The market overall was up 0.1%. A fancy vivid blue diamond ring (est. $14-18 million) goes on view at Sotheby's on Oct. 13, 2017 in London. ILLUSTRATION: GETTY IMAGES FOR SOTHEBY'S In November 2017, Christie’s sold a 8.67-carat fancy intense blue diamond ring in Geneva, Switzerland for $13.2 million. The reason for this disparity has less to do with demand, than it does with the rarity of the stone, says FCRF Chairman Eden Rachminov. Demand for yellow and pink diamonds is actually higher, but the amount of blue diamonds being mined is decreasing. “Almost nothing is coming out of the ground,” he says. Pink diamonds have seen the highest gains in the last 13 years with an overall appreciation of 361.9%, according to FCRF’s index, which is compiled through survey data provided by manufacturers and brokers.
    [Show full text]
  • 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.
    [Show full text]
  • Some Uncommon Sapphire “Imitations”: Blue Co-Zirconia, Kyanite & Blue Dumortierite Dr Michael S
    Some Uncommon Sapphire “Imitations”: Blue Co-zirconia, Kyanite & Blue Dumortierite Dr Michael S. Krzemnicki Swiss Gemmological Institute SSEF [email protected] 筆者滙報數個瑞士珠寶研究院(SSEF)近期收到 in the ring showed a negative RI reading 要求鑑證的藍色寶石,經檢測後確定其中包括 (above 1.79), an isotropic optical character 一些非常罕見的藍寶石模擬石:含錮氧化鋯、 (polariscope) and thus no pleochroism at all. 藍晶石及藍線石等。 Under the microscope, we saw no inclusions, however a slightly greenish reaction under Sapphires are among the most abundant gems the LWSW and there was a weaker similar we receive at the Swiss Gemmological Institute reaction under SWUV lamps. Based on these (SSEF) for testing. From time to time, however, properties and a chemical analysis by X-ray we are quite surprised by the imitations which fluorescence (EDXRF), the blue stone was we find among the goods sent in and this can readily identified as cubic zirconia (ZrO2). then be disappointing news for the clients. In Having seen this artificial product in a wide the following short note, the author presents a range of colours, the author had not previously few uncommon imitations identified recently at seen one of such a saturated and attractive the SSEF. Identification of these imitations is blue. Based on literature (Nassau 1981) the straightforward and should be no problem for analysed traces of cobalt in that stone have any experienced gemmologist. been identified as the colouring element in this specimen. The absorption spectrum of the stone The first case is that of an attractive blue (Fig. 2) – although superposed by several rare faceted stone of approximately 1.4 ct, set in a ring with diamonds (Fig.
    [Show full text]
  • 2015 AFMS Endowment Fund Drawing
    2015 AFMS Endowment Fund Drawing The 2014 Endowment Fund Drawing took place in Tulsa, Oklahoma. We had some very nice donations for prizes, and a lot of people stepped up and bought tickets to support the AFMS Endowment Fund. Thank you for your support. And thank you to those who picked up prizes to deliver at the banquet in Tulsa. That helped save the cost of mailing the items. We have received the following donations for the 2015 Endowment Fund Drawing, which will be held on October 24, 2015, at the awards banquet in Austin, Texas. 1.Copper piece and stock certificate donated by Pam Hecht. Estimated value is $65. MWF 2. Howelite and onyx agate necklace and earrings. Donated by Sharon Rogow, crafted by Betsy Oberheim. Estimated value is $75. CFMS 2015 AFMS Endowment Fund Drawing Page 1 of 11 10-11-2015 3. A large agatized coral head donated by the Suncoast Gem and Mineral Society. It was from an old collection of Withlacoochee River coral donated by a member who passed some years ago. The value is estimated to be at least $100. SFMS (This one is larger than the one given last year.) 4. Phareodus encaustus (fossil fish) from the Eocene Period, Green River formation, Kemmerer, Wyoming. This was donated by J.C. and Donna Moore with an approximate value of $65. MWF #5 - is a Tampa Bay Coral pair donated by Barbara Sky, MWF Uniform Rules Chairman. The pair is about six inches long and two and a half inches wide. The estimated value is $50.
    [Show full text]
  • Metamorphic and Metasomatic Kyanite-Bearing Mineral
    Metamorphic and Metasomatic Kyanite-Bearing Mineral Assemblages of Thassos Island (Rhodope, Greece) Alexandre Tarantola, Panagiotis Voudouris, Aurélien Eglinger, Christophe Scheffer, Kimberly Trebus, Marie Bitte, Benjamin Rondeau, Constantinos Mavrogonatos, Ian Graham, Marius Etienne, et al. To cite this version: Alexandre Tarantola, Panagiotis Voudouris, Aurélien Eglinger, Christophe Scheffer, Kimberly Tre- bus, et al.. Metamorphic and Metasomatic Kyanite-Bearing Mineral Assemblages of Thassos Island (Rhodope, Greece). Minerals, MDPI, 2019, 10.3390/min9040252. hal-02932247 HAL Id: hal-02932247 https://hal.archives-ouvertes.fr/hal-02932247 Submitted on 7 Sep 2020 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. minerals Article Metamorphic and Metasomatic Kyanite-Bearing Mineral Assemblages of Thassos Island (Rhodope, Greece) Alexandre Tarantola 1,* , Panagiotis Voudouris 2 , Aurélien Eglinger 1, Christophe Scheffer 1,3, Kimberly Trebus 1, Marie Bitte 1, Benjamin Rondeau 4 , Constantinos Mavrogonatos 2 , Ian Graham 5, Marius Etienne 1 and Chantal Peiffert
    [Show full text]
  • The Use of Raman Spectroscopy in the Characterization of Variscite Provenance: the Gavà Case
    Chapitre III : Apport des méthodes d’analyses à l’étude de la diffusion des productions The use of Raman spectroscopy in the characterization of variscite provenance: the Gavà case Joan Carlos Melgarejo, Laia Arqués, Cristina Villanova-de-Benavent, Tariq Jahwari, Lisard Torró, Josep Bosch Argilagós, Montgarri Castillo-Oliver, Marc Campeny, Sandra Amores, Aleu Andreazini, Saleh Lehbib, Antoni Camprubí Abstract. The Gavà phosphate deposit, mined during the Neolithic, was produced by weathering processes affecting primary apatite beds. It exhibits a neat vertical zoning, related to chemical gradients during weathering. Strengite, yellowish Al-rich strengite and ferroan variscite are found at the top, pale- green variscite at the intermediate levels, and green variscite in depth. Fe values are very low in the greenish samples, as well as Cr and V. Raman spectrums of the Gavà variscite show differences with samples from other occurrences worldwide. Moreover, some spectral differences can also be observed in the Raman spectra of variscite coming from different depths in the deposit. Raman spectroscopy can be an efficient tool to discriminate not only samples from different geographical localities, but also from its original position in a given deposit. Key-words: variscite, Raman, microprobe, veins, supergene. Résumé. Le gîte de phosphates de Gavà, exploité au Néolithique, s’est formé par des processus de météorisation qui auraient affecté des strates primaires d’apatite. Ce gîte a une zonation chimique verticale, qui aurait été produite par des gradations chimiques lors de la météorisation. La partie haute du gîte contient de la strengite, de l’Al-strengite et de la Fe-variscite jaunâtres ; les niveaux intermédiaires contiennent de la variscite verdâtre et les niveaux plus profonds, de la variscite verte.
    [Show full text]
  • Turquoise: the Cerrillos Mineral Gem
    A Living History Museum Turquoise: The Cerrillos Mineral Gem The mines of Cerrillos, New Mexico produce a particularly beautiful blue/ green variety of turquoise, so stunning in fact that they have been mined for roughly the last 3,000 years! Chemically, it is a phosphate of aluminum carrying small quantities of copper and iron and a green mineral, variscite. These give the gemstone its color as well as its value and beauty. This is the only phosphate that is considered a precious stone. Ancestral Puebloans first started mining the Cerrillos hills circa 900 BCE, and it’s been mined ever since. This “gem” of a mineral has been found across the state, and archaeological evidence shows it’s been mined and fashioned into ornaments and jewelry for centuries, with remnants found at one of the most ancient sites in the state, Chetro Ketl at Chaco Canyon. Southwest indigenous groups call turquoise chalchihuitl, as did the ancient peoples of Mexico and Central America who used the same word to describe jade or green turquoise. One of the hills still being mined in Cerrillos still bears the name, Mount Chalchihuitl. Combined with shell and coral from the California coast acquired in trade, turquoise jewelry itself became a valued commodity. Spanish settlers didn’t have much interest in turquoise as they were looking for what they considered a more important prize, namely gold and silver. In fact, outside of local indigenous groups, other cultural groups weren’t much interested in it and it didn’t really gain popularity with the American cultural at large until the 1890s.
    [Show full text]
  • 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).
    [Show full text]
  • 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
    [Show full text]