Gems & Gemology最新文献

{"title":"Iridescence in metamorphic \"rainbow\" hematite","authors":"Xiayang Lin, P. Heaney, J. Post","doi":"10.5741/GEMS.54.1.28","DOIUrl":"https://doi.org/10.5741/GEMS.54.1.28","url":null,"abstract":"ing 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 are permitted to reproduce isolated articles and photographs/images owned by G&G for noncommercial classroom use without fee. Use of photographs/images under copyright by external parties is prohibited without the express permission of the photographer or owner of the image, as listed in the credits. For other copying, reprint, or republication permission, please contact the Managing Editor. Gems & Gemology is published quarterly by the Gemological Institute of America, a nonprofit educational organization for the gem and jewelry industry. Postmaster: Return undeliverable copies of Gems & Gemology to GIA, The Robert Mouawad Campus, 5345 Armada Drive, Carlsbad, CA 92008. Our Canadian goods and service registration number","PeriodicalId":12600,"journal":{"name":"Gems & Gemology","volume":"54 1","pages":"28-39"},"PeriodicalIF":2.6,"publicationDate":"2018-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45713779","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Real-Time Microradiography of Pearls: A Comparison Between Detectors","authors":"S. Karampelas, A. Al-Alawi, Ali Al-Attawi","doi":"10.5741/GEMS.53.4.452","DOIUrl":"https://doi.org/10.5741/GEMS.53.4.452","url":null,"abstract":"ries have been using film-based microradiography to reveal minute structures that separate natural from cultured pearls, sometimes alongside other methods such as Laue diffraction and endoscopy (e.g., Galibourg and Ryziger, 1927; Anderson, 1932; Alexander, 1941; Webster, 1954; Farn, 1980; Hänni, 1983; Poirot and Gonthier, 1998; Scarratt et al., 2000; Sturman, 2009). Today, real-time X-ray microradiography (RTX) is the foremost testing method for carrying out this vital work. It can also be paired with the more timeconsuming X-ray computed microtomography for challenging identifications and research purposes (Karampelas et al., 2010; Krzemnicki et al., 2010). With film-based microradiography, pearls are sometimes placed in direct contact with a high-resolution film cassette or immersed in a scatter-reducing liquid (e.g., lead nitrate solution or carbon tetrachloride, both of which are hazardous). X-ray scattering may also be reduced by simply surrounding individual pearls with a thin lead sheet or film. Regardless of the technique, a darkroom and a series of chemicals are necessary for film processing. It takes approximately 20 minutes to select the film and secure the pearls to the film cassette. At the same time, the exposure must be determined assuming an average-sized sample and keeping in mind that pearls in a strand are often graduated in size and that spheres require longer exposure times through the centers than the edges. Next, the film must be developed, fixed, and dried. All told, it is a time-consuming process. The last 20 years have seen RTX steadily replace film-based radiography in the medical sector, and over the last decade most gemological laboratories have followed this trend by partially or fully adopting RTX. This method has several important advantages. No hazardous liquids are needed, and it gives immediate or nearly immediate results, which are easier to store and share among a team of technicians or in publications and presentations. RTX microradiography also requires a lower total amount of radiation than filmbased microradiography, though similar X-ray generating tubes may be used without a need to reduce X-ray scattering. Some gemological laboratories initially employed RTX units with image intensifier (II) technology generally associated with digital cameras to acquire RTX microradiographs. More recent units have employed flat panel detectors (FPD), which can be of larger dimension with high resolution. However, FPD costs approximately US$25,000, about 40% more than II units and cameras. An II is a vacuum tube device that converts invisible X-rays transmitted through the sample into visible light by a cesium iodide (CsI) scintillator. The visible light is then converted into electrons at the photoelectric surface and emitted inside the vacuum tube. The emitted electrons are accelerated and focused by electrodes, which act as an electron lens, onto the output screen and converted into bright visible light that is captur","PeriodicalId":12600,"journal":{"name":"Gems & Gemology","volume":" ","pages":""},"PeriodicalIF":2.6,"publicationDate":"2018-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47945468","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Akoya cultured pearl farming in eastern Australia","authors":"L. Otter, O. Agbaje, L. T. Hương, T. Häger, Dorrit E. Jacob","doi":"10.5741/GEMS.53.4.423","DOIUrl":"https://doi.org/10.5741/GEMS.53.4.423","url":null,"abstract":"Akoya cultured pearls have been produced on the eastern shoreline of Australia since approximately 1999 using Pinctada imbricata fucata mollusks native to New South Wales. Unlike many of their Japanese counterparts, Australian akoya cultured pearls are harvested after 18 months of growth and marketed without any post-harvest treatments involving dyes or bleaches.This study presents the first gemological and mineralogical characterization of Australian akoya cultured pearls using Raman, photoluminescence, FTIR, and UV-Vis specular reflectance spectroscopy. Raman and FTIR spectroscopy identified the major mineral phase aragonite as well as some organic compounds. While Raman spectroscopy revealed polyene-related pigments with bands occurring at 1134 and 1532 cm–1 , FTIR spectroscopy showed sulfateand polysaccharide-associated groups occurring at around 1200 and 1115 cm–1 , respectively. UV-Vis spectroscopy revealed broad spectral features that provide insight into the distinct bodycolors and enable discrimination from some non-akoya saltwater cultured pearls from P. margaritifera, P. maxima, and P. mazatlanica bivalves, while separation from other untreated akoya pearls is not possible. Production processes are examined to better understand the modern, sustainable, and environmentally friendly pearl farming operations in Australia.","PeriodicalId":12600,"journal":{"name":"Gems & Gemology","volume":"53 1","pages":"423-437"},"PeriodicalIF":2.6,"publicationDate":"2018-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49066904","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Accurate Reporting of Key Trace Elements in Ruby and Sapphire Using Matrix-Matched Standards","authors":"J. Stone‐Sundberg, Timothy M. Thomas, Ziyin Sun, Y. Guan, Zachary Cole, R. Equall, J. Emmett","doi":"10.5741/GEMS.53.4.438","DOIUrl":"https://doi.org/10.5741/GEMS.53.4.438","url":null,"abstract":"To improve the accuracy and efficiency of trace element analysis in ruby and sapphire, standards sets containing matrix-matched corundum with targeted levels of beryllium, magnesium, silicon, titanium, vanadium, chromium, iron, and gallium were created. Ultra-high-purity corundum was also incorporated as a “true matrix zero.” To our knowledge, these sets contain the most accurate standards for the key trace elements in corundum today. The standards were designed to cover the optimal range of the main trace elements typically characterized in natural ruby and sapphire. Additionally, we were able to accurately quantify silicon in corundum by successfully resolving the ^(28)Si^+ peak from the ^(27)Al^1H^+ peak using the superior mass resolving power of secondary ion mass spectrometry (SIMS) as compared to laser ablation–inductively coupled plasma–quadrupole mass spectrometry (LA-ICP-QMS).","PeriodicalId":12600,"journal":{"name":"Gems & Gemology","volume":" ","pages":""},"PeriodicalIF":2.6,"publicationDate":"2018-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49020036","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Very Deep Origin of the World's Biggest Diamonds","authors":"Evan M. Smith, S. Shirey, Wuyi Wang","doi":"10.5741/GEMS.53.4.388","DOIUrl":"https://doi.org/10.5741/GEMS.53.4.388","url":null,"abstract":"gemstones for jewelry, are some of the most scientifically valuable samples of the deep earth. Interpretation of their included minerals and crystallization history provides a snapshot of otherwise inaccessible geological processes from more than 100 kilometers underground and often from billions of years in the past (e.g., Shirey and Shigley, 2013). No other mineral sample can provide information for research from such depths and from so long ago. Until recently, exceptional gem diamonds such as the famous Cullinan or Lesotho Promise, with a set of physical characteristics that distinguish them from other kinds of diamonds, were enigmatic and had an unknown origin (Bowen et al., 2009; Gurney and Helmstaedt, 2012; Moore, 2014). How did they form? Certainly not like 99% of other gem diamonds. New research carried out in the last two years at GIA, the Carnegie Institution for Science, and the University of Padua reveals that these Cullinan-like diamonds form in a geologically special way, involving metallic liquid and originating from extreme depths in Earth’s mantle well below that of other gem diamonds (Smith et al., 2016).","PeriodicalId":12600,"journal":{"name":"Gems & Gemology","volume":" ","pages":""},"PeriodicalIF":2.6,"publicationDate":"2018-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46094533","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Inclusions in Natural, Synthetic, and Treated Ruby","authors":"Nathan D. Renfro, John I. Koivula, J. Muyal, S. McClure, Kevin Schumacher, J. Shigley","doi":"10.5741/GEMS.53.4.457","DOIUrl":"https://doi.org/10.5741/GEMS.53.4.457","url":null,"abstract":"See end of article for About the Authors. GEMS & GEMOLOGY, Vol. 53, No. 4, pp. 457–458, http://dx.doi.org/10.5741/GEMS.53.4.457 © 2017 Gemological Institute of America been critical to the development of color and clarity treatments (including heating and dyeing, and now more recently introduced processes) and synthetic gems. In the early 1900s, over five million carats of synthetic ruby were produced annually by the flamefusion, or Verneuil, method (Hughes, 2017). Innovative new treatments have also played a major role in satisfying the continued demand for ruby. In the early 1990s, gemological laboratories saw the introduction of chromium-diffused rubies (McClure et al., 1993). In the early 2000s, lead-glass filling of low-quality rubies reached international markets and became one of the most widespread—and most","PeriodicalId":12600,"journal":{"name":"Gems & Gemology","volume":" ","pages":""},"PeriodicalIF":2.6,"publicationDate":"2018-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44566656","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Gem Virtuosos: The Drehers and Their Extraordinary Carvings","authors":"R. Weldon, C. Jonathan, R. Tozer","doi":"10.5741/gems.53.4.404","DOIUrl":"https://doi.org/10.5741/gems.53.4.404","url":null,"abstract":"the father-and-son team of Gerd and Patrick Dreher are remarkably lifelike. Agate toads appear bumpy, glistening, and slippery. Brimming with personality, their eyes appear to follow the viewer around the room. A carved tiger lily emerges from banded agate (figure 1) as a velvety, dappled flower, its petals enticingly curling inward. And on the backs of these petals, details of the flower’s physiognomy are scrupulously maintained. Much like the gem materials from which they are carved, these works are one-of-a-kind creations. Decades of experience between the two imparts virtuosity to their work, as well as a sense of humor often depicted in the subjects. Today, Gerd is globally acknowledged as a master of the craft, while Patrick has emerged from the younger generation, adding new carving techniques to the family repertoire. This enhances the formidable range of skills that have been passed down through the Dreher family for 13 generations. Following in the path of their ancestors, the Drehers’ ability to render the anatomy of flora and fauna in astonishing detail demands an intimate knowledge of their subject matter, not to mention a deep understanding of the characteristics and attributes of the gem materials they carve. The Drehers study rough gem material, sometimes for years. From these observations they conceive a three-dimensional outcome and then set to work bringing the stone to life (figure 2). A growing collection of diamond-sintered tools, and a thorough understanding of how to use them, underpins their closely guarded lapidary techniques.","PeriodicalId":12600,"journal":{"name":"Gems & Gemology","volume":" ","pages":""},"PeriodicalIF":2.6,"publicationDate":"2018-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44132503","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Saltwater Pearls from the Pre- to Early Columbian Era: A Gemological and Radiocarbon Dating Study","authors":"Chunhui Zhou, G. Hodgins, T. Lange, K. Saruwatari, Nicholas Sturman, L. Kiefert, K. Schollenbruch","doi":"10.5741/GEMS.53.3.286","DOIUrl":"https://doi.org/10.5741/GEMS.53.3.286","url":null,"abstract":"ing 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 are permitted to reproduce isolated articles and photographs/images owned by G&G for noncommercial classroom use without fee. Use of photographs/images under copyright by external parties is prohibited without the express permission of the photographer or owner of the image, as listed in the credits. For other copying, reprint, or republication permission, please contact the Managing Editor. Gems & Gemology is published quarterly by the Gemological Institute of America, a nonprofit educational organization for the gem and jewelry industry. Postmaster: Return undeliverable copies of Gems & Gemology to GIA, The Robert Mouawad Campus, 5345 Armada Drive, Carlsbad, CA 92008. Our Canadian goods and service registration number","PeriodicalId":12600,"journal":{"name":"Gems & Gemology","volume":" ","pages":""},"PeriodicalIF":2.6,"publicationDate":"2017-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47393837","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Colombian Emerald Industry: Winds of Change","authors":"Darwin Fortaleche, Andrew Lucas, J. Muyal, Tao Hsu, P. Padua","doi":"10.5741/GEMS.53.3.332","DOIUrl":"https://doi.org/10.5741/GEMS.53.3.332","url":null,"abstract":"C is synonymous with fine emerald, and production is believed to date back well over a thousand years. Over the centuries the beautiful verdant gemstone, which emerges from areas that are also a lush green, has been linked to violence and human exploitation. Nevertheless, the desire of the Colombian people to mine for this treasure and strike it rich has endured, with enough dreams coming true to drive their passion. In recent years, industry changes have accelerated, perhaps more profoundly than ever before. While gov-","PeriodicalId":12600,"journal":{"name":"Gems & Gemology","volume":"53 1","pages":"332-358"},"PeriodicalIF":2.6,"publicationDate":"2017-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45382368","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Photoluminescence Spectra of Emeralds from Colombia, Afghanistan, and Zambia","authors":"D. Thompson, C. Bayens, M. Morgan, Taylor J. Myrick, N. E. Sims","doi":"10.5741/GEMS.53.3.296","DOIUrl":"https://doi.org/10.5741/GEMS.53.3.296","url":null,"abstract":"","PeriodicalId":12600,"journal":{"name":"Gems & Gemology","volume":" ","pages":""},"PeriodicalIF":2.6,"publicationDate":"2017-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43482470","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}