Gems & Gemology最新文献

{"title":"Mineral Inclusions in Sapphire from Basaltic Terranes in Southern Vietnam: Indicator of Formation Model","authors":"Doan Thi Anh Vu, A. Salam, Alongkot Fanka, E. Belousova, C. Sutthirat","doi":"10.5741/GEMS.56.4.498","DOIUrl":"https://doi.org/10.5741/GEMS.56.4.498","url":null,"abstract":"GEMS & GEMOLOGY WINTER 2020 Since the late 1980s, sapphire mines in southern Vietnam have supplied significant quantities of gem materials to the jewelry industry (figure 1). Commercial gem mines in southern Vietnam have been located in four main areas, including Dak Nong, Di Linh, Binh Thuan, and Krong Nang (figure 2) (Smith et al., 1995; Long et al., 2004; Garnier et al., 2005; Izokh et al., 2010; Vu, 2010, 2018). Specifically, the first discovery of abundant gem sapphires was in Dak Nong, followed by Di Linh, Binh Thuan, and Krong Nang, respectively. These sapphires accumulated in Upper-Pleistocene to Quaternary alluvial deposits. In 2017, we carried out field trips in southern Vietnam encompassing Binh Thuan Province, Di Linh (Lam Dong Province), Dak Nong Province, and Krong Nang (Dak Lak Province), where sapphire samples were collected directly from the mines (see figure 2). Gem mining activities in these areas are conducted by a few local miners. Pits are dug with basic tools before washing and hand picking along streams by artisanal miners (figure 3), and mines worked by machinery (figure 4) can also be found. Sapphires in this region usually range from dark blue to bluish green, yellowish green to green, with rare yellow sapphire. The natural intense blue sapphire is the best known and has been specifically recovered from the Dak Nong and Di Linh gem fields (figure 1, left). Other colors such as bluish green and yellowish green to green are common, particularly in the Binh Thuan and Krong Nang gem fields, respectively (figure 1, right). However, these sapphire varieties are generally heat treated for color enhancement. In addition, trapiche-type sapphires (figure 5) are sometimes found in these gem fields.","PeriodicalId":12600,"journal":{"name":"Gems & Gemology","volume":"56 1","pages":"498-515"},"PeriodicalIF":2.6,"publicationDate":"2021-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42462734","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":"Fluorescence Characteristics of Blue Amber from the Dominican Republic","authors":"Zhiqing Zhang, Jiang Xinran, Wang Yamei, Fanli Kong, A. Shen","doi":"10.5741/GEMS.56.4.484","DOIUrl":"https://doi.org/10.5741/GEMS.56.4.484","url":null,"abstract":"GEMS & GEMOLOGY WINTER 2020 Amber is widely distributed around the world. It is of interest not merely as an important natural fossil resin witnessing the history of the earth and providing direct evidence for paleobiologists, but also as a widely loved organic gemstone. Transparent yellow amber from the Dominican Republic, Mexico, and Myanmar displaying a blue or greenish blue glow when viewed on a black background in normal sunlight is called “blue amber” in the Chinese gem trade. This paper focuses on amber displaying this characteristic and will refer to this material as blue amber. In the Guangzhou and Shenzhen amber trading centers, Dominican blue amber can be sold for up to thousands of Chinese RMB (around several hundred U.S. dollars) per gram, while Mexican material fetches only several hundred RMB (around several tens of U.S. dollars) per gram—even though they have a similar appearance. Bellani et al. (2005) first described blue amber and studied the fluorescence emission, excitation, and optical absorption spectra of Dominican blue and non-blue (including yellow and red varieties) amber. They found that multiple emission fluorescence peaks at 449 nm, 476 nm, and 505 nm occurred in this blue amber, while only a broad fluorescence band was observed in non-blue amber. They further","PeriodicalId":12600,"journal":{"name":"Gems & Gemology","volume":"56 1","pages":"484-496"},"PeriodicalIF":2.6,"publicationDate":"2021-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49464682","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":"Low-Temperature Heat Treatment of Pink Sapphires from Ilakaka, Madagascar","authors":"Sudarat Saeseaw, Charuwan Khowpong, W. Vertriest","doi":"10.5741/GEMS.56.4.448","DOIUrl":"https://doi.org/10.5741/GEMS.56.4.448","url":null,"abstract":"GEMS & GEMOLOGY WINTER 2020 Heat treatment has been used to improve the color and/or clarity of corundum for more than a thousand years. Various parameters such as temperature, heating and cooling time, and oxidizing or reducing atmosphere will affect the final color (Emmett and Douthit, 1993; Emmett et al., 2003; Hughes et al., 2017). The border between highand low-temperature heat treatment has been defined by Emmett (in Hughes et al., 2017) as the temperature needed to dissolve second-phase microcrystals, which is somewhere between 1200° and 1350°C. Heating at high temperatures will damage most inclusions in ruby and sapphire and is often detectable by trained gemologists. In contrast, heating corundum at low temperatures, sometimes below 700°C, will only subtly affect their internal inclusions, making the treatment much more challenging to detect without advanced instrumentation (figure 1). Previous studies on the effect of low-temperature heat treatment on inclusions have focused on rubies from Mozambique (Pardieu et al., 2015; Sripoonjan et","PeriodicalId":12600,"journal":{"name":"Gems & Gemology","volume":"56 1","pages":"448-457"},"PeriodicalIF":2.6,"publicationDate":"2021-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45719201","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":"Natural-Color D-to-Z Diamonds: A Crystal-Clear Perspective","authors":"S. eaton-magaña, T. Ardon, C. Breeding, J. Shigley","doi":"10.5741/GEMS.56.3.335","DOIUrl":"https://doi.org/10.5741/GEMS.56.3.335","url":null,"abstract":"GEMS & GEMOLOGY FALL 2020 When people hear the word diamond, colorless diamonds generally come to mind— not the more exotic colors discussed earlier in this article series. In purchasing a diamond, they are likely to choose one that is colorless to nearcolorless. When one thinks of perfection in a diamond, a D-Flawless stone is usually the benchmark. The lack of color, which so inhibits the consumer appeal of many other gemstones, is instead considered a measure of stature for diamonds. Therefore, we finish this series (Breeding et al., 2018, 2020; Eaton-Magaña et al., 2018a, 2018b, 2019) by examining diamonds with very little to no color at all—those on the D-to-Z grading scale. Although they make up by far the largest proportion of stones submitted to GIA, detailed statistics of D-to-Z diamonds have never been presented before. In each of our previous colored diamond articles, we presented data on stones submitted to GIA from 2008 to 2016. For example, GIA examined more than 15,000 naturally colored blue/gray/violet diamonds in that period (Eaton-Magaña et al., 2018a). During those same years, GIA received millions of D-to-Z diamonds (e.g., figure 1). For this study, we examined all D-to-Z diamonds submitted for grading reports or dossier reports to any of GIA’s laboratories during much of 2017. From our analysis of submissions over the last decade, those from 2017 and used in this study are representative of GIA’s current and historical intake. Any diamonds submitted on multiple occasions during this period were identified, and only the most recent data for each stone are included in this study.","PeriodicalId":12600,"journal":{"name":"Gems & Gemology","volume":"56 1","pages":"318-335"},"PeriodicalIF":2.6,"publicationDate":"2020-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45001323","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":"A History of European Royal Jewel Sales, Including Sotheby's 2018 Auction of Marie Antoinette's Jewels","authors":"R. Shor","doi":"10.5741/GEMS.56.3.356","DOIUrl":"https://doi.org/10.5741/GEMS.56.3.356","url":null,"abstract":"","PeriodicalId":12600,"journal":{"name":"Gems & Gemology","volume":"56 1","pages":"356-379"},"PeriodicalIF":2.6,"publicationDate":"2020-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41474683","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":"Unique Raindrop Pattern of Turquoise from Hubei, China","authors":"Ling Liu, Ming-xing Yang, Yan Li","doi":"10.5741/GEMS.56.3.380","DOIUrl":"https://doi.org/10.5741/GEMS.56.3.380","url":null,"abstract":"","PeriodicalId":12600,"journal":{"name":"Gems & Gemology","volume":"56 1","pages":"380-400"},"PeriodicalIF":2.6,"publicationDate":"2020-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43640788","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":"Inclusion and Trace Element Characteristics of Emeralds from Swat Valley, Pakistan","authors":"H. Guo, Xiaoyan Yu, Yuyu Zheng, Zhulin Sun, M. Ng","doi":"10.5741/GEMS.56.3.336","DOIUrl":"https://doi.org/10.5741/GEMS.56.3.336","url":null,"abstract":"","PeriodicalId":12600,"journal":{"name":"Gems & Gemology","volume":"56 1","pages":"336-355"},"PeriodicalIF":2.6,"publicationDate":"2020-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43332799","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":"Vietnam: Shell Nuclei, Pearl Hatcheries, and Pearl Farming","authors":"Nicholas Sturman, Kwanreun Lawanwong, Nuttapol Kitdee, Devchand Chodhry","doi":"10.5741/GEMS.56.3.402","DOIUrl":"https://doi.org/10.5741/GEMS.56.3.402","url":null,"abstract":"GEMS & GEMOLOGY FALL 2020 V is a land of great diversity and beauty. From the hustle and bustle of Ho Chi Minh City to the beauty of Hạ Long Bay and Hoi An (both UNESCO World Heritage Sites), there are innumerable places of interest. Economically, Vietnam is beginning to see significant investment from a wide range of businesses, domestic and foreign. While still dependent on agriculture, the country is emerging as a major player in the electronics and oil/gas industries, among others. These factors, together with a robust tourism industry, are resulting in an expanding population with greater prosperity than ever before. Jewelry, including pearl jewelry, ranks high on the list of luxury items, as there is a significant range of price points at which disposable wealth can be spent. From the costume jewelry sector to high-end offerings, there is something to suit all tastes. While cultured pearls, accounting for 99.9% of the market since the early 1900s, do not usually fall into the higher-end bracket, there remains a healthy demand from consumers (Shor, 2007; Heebner, 2015). The choice of bead cultured pearls in the marketplace is also diverse. Consumers may choose from the usual imported gray to black Tahitian bead cultured pearls, “golden” bead cultured pearls from the Philippines or Indonesia, and bead cultured pearls produced in China. Hạ Long Bay (figures 1 and 2) in northern Vietnam is where most pearl farms, producing predominantly “akoya” (Pinctada fucata martensii) pearls, may be found. These farms are a mix of independent operations and joint ventures with the Vietnamese government. A prime example of the latter is Spica, a Vietnamese-Japanese joint venture that has produced bead cultured pearls for more than a decade. Some farming activity is also found in the waters off southern Vietnam at Nha Trang, as will be seen later, and Phu Quoc (Strack, 2006). Vietnam has produced saltwater cultured pearls commercially since the 1990s. However, the first attempts reportedly began in the 1960s (Strack, 2006). Today, based on the 300–400 kg production from the two farms visited in this report, the country is estimated to produce approximately 2,000 kg per annum. The majority of the production is akoya, with a smaller quantity of Pinctada maxima, and much of the production is currently exported to China, Japan, India, and the United Sates. When the harvests are good, the quality tends to be higher, but the opposite also holds true.","PeriodicalId":12600,"journal":{"name":"Gems & Gemology","volume":"56 1","pages":"402-415"},"PeriodicalIF":2.6,"publicationDate":"2020-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41908068","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":"Separation of Natural Laboratory-Grown Diamond Using Time-Gated Luminescence Imaging","authors":"C. McGuiness, Amber M. Wassell, P. Lanigan, S. Lynch","doi":"10.5741/gems.56.2.220","DOIUrl":"https://doi.org/10.5741/gems.56.2.220","url":null,"abstract":"GEMS & GEMOLOGY SUMMER 2020 The task of identifying a diamond will typically fall to a diamond appraiser, grader, or gemologist while preparing a grading certificate or appraisal. Whether a diamond is natural or lab-grown is a key factor in its market value and is of paramount importance to the gemologist. Many characteristics can be used to distinguish between natural and synthetic dia mond, but the inherent variability in the properties of natural and synthetic diamond can make such a task difficult. A useful and proven characteristic is the emission of luminescence when a diamond is excited by a source of ultraviolet energy. Typically, a gemologist would utilize an ultraviolet lamp with excitation wavelengths of 365 nm (long-wave ultraviolet, LWUV) or 254 nm (short-wave ultraviolet, SWUV), which correspond to the emission lines of a low-pressure mercury-vapor lamp. In this application, “fluorescence” would be observed during ultraviolet excitation, while “phosphorescence” may be observed when the excitation is removed. The De Beers DiamondView instrument (Spear and Welbourn, 1994; Welbourn et al., 1996) was designed to authenticate natural diamonds and synthetic diamonds. It allows a more sophisticated observation to be made by way of a shorter wavelength excitation of <225 nm corresponding to the primary absorption edge and only exciting around 1-micron depth of material, such that observed luminescence","PeriodicalId":12600,"journal":{"name":"Gems & Gemology","volume":"56 1","pages":"220-229"},"PeriodicalIF":2.6,"publicationDate":"2020-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46934365","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":"Hydrogen and Oxygen Stable Isotope Ratios of Dolomite-Related Nephrite: Relevance for its Geographic Origin and Geological Significance","authors":"Kong Gao, Ting Fang, Taijin Lu, Yan Lan, Yong Zhang, Yuanyuan Wang, Yayun Chang","doi":"10.5741/gems.56.2.266","DOIUrl":"https://doi.org/10.5741/gems.56.2.266","url":null,"abstract":"GEMS & GEMOLOGY SUMMER 2020 Nephrite is a near-monomineralic rock composed of tremolite-actinolite, Ca2(Mg,Fe)5Si8O22(OH)2. It occurs worldwide (figure 1) and is classified as dolomite-related or serpentine-related according to the different parent rocks and ore-hosting rocks, and both types form by metasomatism (Yui et al., 1988; Tang et al., 1994; Yang and Abduriyim, 1994; Harlow and Sorensen, 2005; Burtseva et al., 2015). The large and well-known dolomite-related nephrite deposits are distributed in the Xinjiang Uyghur Autonomous Region (hereafter abbreviated as Xinjiang) of China, Qinghai Province of China, Siberia in Russia, and Chuncheon in South Korea (figure 1). Data from smaller-scale deposits such as Val Malenco in Italy and Złoty Stok in Poland are also used in this study (figure 1). The rest of the data were collected from nephrites produced at multiple small-scale sources in China: Xiuyan, Tanghe, Dahua, and Luodian (figure 2). With nephrite jade, a premium is placed on geographic origin since the gem’s cultural significance differs by location. It is possible to have an opinion","PeriodicalId":12600,"journal":{"name":"Gems & Gemology","volume":"56 1","pages":"266-280"},"PeriodicalIF":2.6,"publicationDate":"2020-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47878477","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}