Gems & Gemology最新文献

{"title":"A Quantitative Description of the Causes of Color in Corundum","authors":"Emily V. Dubinsky, J. Stone‐Sundberg, J. Emmett","doi":"10.5741/gems.56.1.2","DOIUrl":"https://doi.org/10.5741/gems.56.1.2","url":null,"abstract":"GEMS & GEMOLOGY SPRING 2020 Gemstones are valued for their beauty, rarity, and durability, and what typically captures our attention is their magnificent array of colors. Corundum exhibits an extremely wide range of colors in nature (figure 1). From pigeon’s blood red ruby to cornflower blue and lemon yellow sapphire, nearly every color is represented. The only corundum color not represented in nature is a saturated intense emerald green. However, less intense olive green to teal green stones are often found in basalt-hosted corundum deposits. Corundum’s broad range of colors is related to its detailed chemistry. Some minerals possess inherent color because the chromophore is one of the basic chemical components of its makeup. Such stones are termed idiochromatic, meaning self-colored. For example, turquoise, whose chemical formula is CuAl6(PO4)4(OH)8•4H2O, is colored by copper, a primary component of its structure. Other minerals such as corundum are, when very pure, completely colorless. In fact, pure corundum, with the chemical formula Al2O3, is absolutely transparent from the deep ultraviolet region into the infrared. Such minerals are termed allochromatic. Their colors in nature are caused by minor impurities, referred to as trace elements, or other point defects in the crystal lattice that have been incorporated during growth or later equilibration in nature. The causes of color in corundum are many and have been primarily addressed in a non-quantitative way for many years (see, for example, Fritsch and Rossman, 1987, 1988; Häger, 2001; Emmett et al., 2003). Trace elements themselves can be the direct cause of color. Cr3+, for example, creates pink and red coloration in corundum. Trace elements can also interact with each other, creating a new chromophore. The Fe2+-Ti4+ pair is such an example, strongly absorbing in the yellow and red regions of the spectrum and thus creating magnificent blue sapphires. When beryllium-diffused corundum entered the marketplace, we were surprised by the wide range of colors that were produced, seemingly by a single element (Emmett et al., 2003). Measurements of the beryllium levels showed that the concentrations were generally from a few to a few tens of parts per million atomic (ppma), yet the colors produced were often intense. For comparison, red coloration in corundum requires several hundred to a few thousand ppma of Cr3+, a concentration at least two orders of magnitude greater than Be2+, to produce strong color. Our studies of the beryllium-diffused stones (Emmett et al., 2003) demonstrated that the Be2+ ion itself was not the cause of color. However, replacing a trivalent aluminum ion with a divalent beryllium ion required the creation of a trapped hole (h•) for A QUANTITATIVE DESCRIPTION OF THE CAUSES OF COLOR IN CORUNDUM","PeriodicalId":12600,"journal":{"name":"Gems & Gemology","volume":"1 1","pages":""},"PeriodicalIF":2.6,"publicationDate":"2020-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43527312","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":"Color Characteristics of Blue to Yellow Beryl from Multiple Origins","authors":"Yang Hu, Ren Lu","doi":"10.5741/gems.56.1.54","DOIUrl":"https://doi.org/10.5741/gems.56.1.54","url":null,"abstract":"GEMS & GEMOLOGY SPRING 2020 Gem beryl is a significant gem species, including color varieties such as emerald, aquamarine, heliodor, goshenite, morganite, and red beryl. Blue to yellow beryl has been found in numerous locations, including Brazil, South Africa, Russia, Ukraine, Canada, Myanmar, the United States, Afghanistan, and China (Belakovskiy et al., 2005). Blue color in aquamarine and yellow color in heliodor are attributed to abundant Fe ions (Wood and Nassau, 1968). Fe ions are also present in all other color varieties of beryl, though Fe content is relatively low in morganite. Although discussions on the role of Fe ions in blue to yellow beryl are not new, they have mainly focused on crystal physics and chemistry. This article explores the color characteristics and chromophore ions of blue to yellow beryl using quantitative chemical and spectral analysis. The crystal structure of beryl is unique for having a peanut-shaped “channel” along the c-axis, and alkali ions in this channel interact with transition metal ions. Therefore, we will discuss the features of alkali elements and their roles in beryl color, based on analysis of the channel mechanism. This research was part of a series of ongoing studies on the color characteristics of beryl. MATERIALS AND METHODS Beryls from different origins were gathered and 14 of them with various color and alkali content were selected for this study (see table 1). They were classified in the following color varieties: goshenite (colorless to near-colorless), aquamarine (greenish blue to blue), green beryl (green to yellowish green), and heliodor (greenish yellow to yellow). With the exception of two faceted stones and one rough stone, the samples were","PeriodicalId":12600,"journal":{"name":"Gems & Gemology","volume":"56 1","pages":"54-65"},"PeriodicalIF":2.6,"publicationDate":"2020-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41461069","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 Vanadium-Rich Emerald from Malipo, China","authors":"Yang Hu, Ren Lu","doi":"10.5741/gems.55.3.338","DOIUrl":"https://doi.org/10.5741/gems.55.3.338","url":null,"abstract":"Emeralds were discovered in Malipo County in southwestern China more than 30 years ago. Malipo emeralds are still being extracted and are expected to be available over the next decade. This study provides a full set of data through standard gemological properties, inclusion scenes, color characteristics, and advanced spectroscopic and chemical analyses including Raman, XRD, micro UV-Vis-NIR, EPR, and LA-ICP-MS. Multiphase inclusions in Malipo emerald are distinct with various shapes and occasionally a colorless transparent crystal. Abundant vanadium substitutes for aluminum in the octahedral site and serves as the predominant coloring agent, leading to a yellowish green color. Among significant known deposits, Malipo emerald has a unique chemical composition in its combination of high V, low Cr, and moderate Fe, as well as high Li and Cs concentrations.","PeriodicalId":12600,"journal":{"name":"Gems & Gemology","volume":" ","pages":""},"PeriodicalIF":2.6,"publicationDate":"2019-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47495534","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":"Gemstones in the Era of the Taj Mahal and the Mughals","authors":"D. Dirlam, Chris L. Rogers, R. Weldon","doi":"10.5741/gems.55.3.294","DOIUrl":"https://doi.org/10.5741/gems.55.3.294","url":null,"abstract":"","PeriodicalId":12600,"journal":{"name":"Gems & Gemology","volume":" ","pages":""},"PeriodicalIF":2.6,"publicationDate":"2019-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43228031","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":"Effects of Mollusk Size on Growth and Color of Cultured Half-Pearls from Phuket, Thailand","authors":"K. Kanjanachatree, Napapit Limsathapornkul, Amorn Inthonjaroen, Raymond J. Ritchie","doi":"10.5741/gems.55.3.388","DOIUrl":"https://doi.org/10.5741/gems.55.3.388","url":null,"abstract":"","PeriodicalId":12600,"journal":{"name":"Gems & Gemology","volume":" ","pages":""},"PeriodicalIF":2.6,"publicationDate":"2019-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41946793","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":"Mineral Inclusions in Ruby and Sapphire from the Bo Welu Gem Deposit in Chanthaburi, Thailand","authors":"Supparat Promwongnan, C. Sutthirat","doi":"10.5741/gems.55.3.354","DOIUrl":"https://doi.org/10.5741/gems.55.3.354","url":null,"abstract":"Thailand are located in the provinces of Chanthaburi-Trat, Kanchanaburi, PhraeSukhothai, Ubon Ratchathani, Si Sa Ket, and Phetchabun (figure 1). However, a few main areas have been economically mined and supplied gems to the world market. Sapphire mines were once extensively operated in Kanchanaburi, but most have recently closed down. The Chanthaburi-Trat area has been the most significant source of Thai corundum, and a few small mines are still in operation there. The most famous source of Thai rubies is located in the Bo Rai deposit in the eastern part of Trat Province, close to the Cambodian province of Pailin (figure 1). What became known as “Siamese ruby” was first named from here and adjacent areas. Meanwhile, the main gem mining area for sapphire (yellow, green, and blue, along with golden star and black star sapphires) is the Bang Ka Cha deposit in western Chanthaburi (again, see figure 1). Most gem mines in the central deposits, around Khlung District within Chanthaburi Province, have supplied more sapphire than ruby (Vichit, 1992; Pattamalai, 2015). The focus of this study, the Bo Welu gem field located in the central gem deposits, has been mined for both ruby and sapphire. Corundum from this area is generally heat-treated to enhance its color, especially the red (or purplish red) ruby and the blue sapphire (figure 2), which are in high demand, particularly within Thailand.","PeriodicalId":12600,"journal":{"name":"Gems & Gemology","volume":" ","pages":""},"PeriodicalIF":2.6,"publicationDate":"2019-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46719367","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-Rich Green Diamond Color-Treated by Multi-Step Processing","authors":"Wenqing Huang, Pei-ran Ni, Ting Shui, Guanghai Shi","doi":"10.5741/gems.55.3.398","DOIUrl":"https://doi.org/10.5741/gems.55.3.398","url":null,"abstract":"been characterized using microscopy and spectroscopic techniques. The diamond has been unambiguously identified as color-treated. The simultaneous presence of multiple centers related to irradiation and annealing—including H1a, H1b, NV0, NV–, H3, H4, GR1, and H2—was revealed. UV-Vis-NIR absorption spectroscopy showed that the diamond owes its color to the two major bands related to H3 and GR1. The combination of these spectroscopic features in one diamond has not been reported in the gemological literature, suggesting that this diamond was subjected to a complex treatment procedure that is not frequently applied. Taking into account the thermal stability of the defects involved and the defect transformations at high temperatures, two possible treatment procedures explaining the observed combination of spectroscopic features are proposed.","PeriodicalId":12600,"journal":{"name":"Gems & Gemology","volume":" ","pages":""},"PeriodicalIF":2.6,"publicationDate":"2019-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48646927","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":"Pressed Gibbsite and Calcite as a Rhodochrosite Imitation","authors":"H. Xu, Xiaoyan Yu","doi":"10.5741/gems.55.3.406","DOIUrl":"https://doi.org/10.5741/gems.55.3.406","url":null,"abstract":"ket, with gemological properties, chemical composition, and structural characteristics that are different from natural rhodochrosite. In this investigation, four samples— two imitations and two rhodochrosites—were examined by standard gemological testing, scanning electron microscopy, energy-dispersive spectroscopy, X-ray diffraction, FTIR, and Raman microspectroscopy. Examination revealed that the imitations are composed of pressed gibbsite and calcite powder with a granular structure, which are easy to identify through standard gemological testing.","PeriodicalId":12600,"journal":{"name":"Gems & Gemology","volume":" ","pages":""},"PeriodicalIF":2.6,"publicationDate":"2019-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46388820","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":"Characteristics of Hydrothermally Treated Beeswax Amber","authors":"Yamei Wang, Yan Li, Fang Liu, Quan-li Chen","doi":"10.5741/gems.55.3.370","DOIUrl":"https://doi.org/10.5741/gems.55.3.370","url":null,"abstract":"lions of years ago when sap from ancient trees hardened and fossilized. Scientists, gemologists, and collectors treasure amber that contains suspended insects or assorted plant fragments, creating a fascinating time capsule (Ross, 2010). Amber has become increasingly popular in the jewelry trade. It is usually translucent to opaque, and its opacity is caused by the reflection and scattering of incident light by an abundance of internal tiny bubbles. “Beeswax,” a term commonly used in the Chinese gem trade, refers to amber that is semi-translucent to opaque with greasy luster. Beeswax accounts for about 60% of natural amber production globally. Due to the saying “Millennium amber, million years beeswax” in the Chinese gem market, many Chinese consumers mistakenly believe that beeswax takes much longer to form than amber. This misimpression has driven demand for beeswax and significantly raised its price. Among beeswax, the “chicken-fat” yellow variety is highly desired in China for its vivid color, but limited in global production. It is worth noting that in the international rough amber trade, transparent and opaque materials are usually mixed together for sale, just as they are mixed together in nature. There is usually a layer of weathered skin on the surface of both transparent and opaque rough amber, making it impossible to choose them individually by hand under normal lighting. There is no price difference between the two. Quality is judged according to weight, size, shape, and impurities. Due to the popularity of beeswax in the Chinese market, however, amber processing enterprises have preferred to purchase and store rough beeswax materials, artificially driving up the price of the rough ma-","PeriodicalId":12600,"journal":{"name":"Gems & Gemology","volume":" ","pages":""},"PeriodicalIF":2.6,"publicationDate":"2019-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48426295","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 Fancy White and Fancy Black Diamonds: Where Color and Clarity Converge","authors":"S. eaton-magaña, T. Ardon, C. Breeding, J. Shigley","doi":"10.5741/gems.55.3.320","DOIUrl":"https://doi.org/10.5741/gems.55.3.320","url":null,"abstract":"mond, we typically discuss atomic-level defects rather than inclusions—relying more on our spectrometers than our microscopes. Seldom are the diamonds distinguished not by color saturation, but by tone (neutral lightness and darkness) and transparency. Nevertheless, Fancy white and Fancy black diamonds break these rules and exist within their own special category, distinct from the other fancy-color diamonds described previously in our article series (Breeding et al., 2018; Eaton-Magaña et al., 2018a, 2018b). Fancy white diamonds, due to their scarcity as faceted stones, comparatively small size, and the lack of notable historical examples, are not well known. They are largely procured by connoisseurs. Probably the most famous of Fancy black diamonds is the Black Orlov (figure 1), a 67.50 ct cushion with a provenance dating back two centuries and, like the Hope diamond, rumored to be “cursed” (Balfour, 2009). Other famous Fancy black diamonds include the 312.24 ct Mogul-cut Spirit of de Grisogono, one of the world’s largest black diamonds, which originated from the Central African Republic. The Gruosi diamond is a 115.34 ct heart shape reportedly discovered in India, and the Korloff Noir is an 88 ct round brilliant. NATURAL-COLOR FANCY WHITE AND FANCY BLACK DIAMONDS: WHERE COLOR AND CLARITY CONVERGE","PeriodicalId":12600,"journal":{"name":"Gems & Gemology","volume":" ","pages":""},"PeriodicalIF":2.6,"publicationDate":"2019-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45954403","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}