Gems & Gemology最新文献

{"title":"Naturally Colored Yellow and Orange Gem Diamonds: The Nitrogen Factor","authors":"C. Breeding, S. eaton-magaña, J. Shigley","doi":"10.5741/gems.56.2.194","DOIUrl":"https://doi.org/10.5741/gems.56.2.194","url":null,"abstract":"GEMS & GEMOLOGY SUMMER 2020 Among fancy-color diamonds, those with saturated blue, green, and red colors are the rarest and generally the most highly valued. Over the last decade, however, diamonds with pure hues in these colors have made up less than one-tenth of one percent of all diamonds examined at GIA, making them virtually unattainable in the marketplace. In recent issues of Gems & Gemology, we have documented the gemological and spectroscopic properties of the rarest of fancy-color diamonds ranging from pink-to-red, blue, and green to the more unusual white and black. This article will address the most common colored diamonds, those with yellow hues, while also examining their much rarer orange cousins (figure 1). This is the last of the fancy color groups in this series, and a brief summary of all the colored diamond groups is provided at the end of the article. Yellow and orange diamonds owe their color primarily to nitrogen impurities that are incorporated in the diamond lattice during growth deep in the earth. Nitrogen is the most common impurity in natural diamond due to the very similar atomic radii of nitrogen and carbon atoms (155 and 170 picometer Van der Waals radii, respectively) as well as the relative abundance of nitrogen in the growth environ-","PeriodicalId":12600,"journal":{"name":"Gems & Gemology","volume":"56 1","pages":"194-219"},"PeriodicalIF":2.6,"publicationDate":"2020-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47924416","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":"History of the Chivor Emerald Mine, Part II (1924-1970): Between Insolvency and Viability","authors":"K. Schmetzer, G. Martayan, A. Blake","doi":"10.5741/gems.56.2.230","DOIUrl":"https://doi.org/10.5741/gems.56.2.230","url":null,"abstract":"GEMS & GEMOLOGY SUMMER 2020 Many legends are told about the history of the Chivor emerald mine.1 The story begins with the sporadic working of the Colombian mine by indigenous people before being sought out by Spanish conquistadores in the first half of the sixteenth century. The property was exploited by the Spanish in the sixteenth and seventeenth centuries and then forgotten in the jungle for a period of more than two centuries after 1672. Schmetzer et al. (2020) chronicled the first part of the modern era commencing after the 200-year break, covering from 1880 to 1925. During that interval, Colombian miner Francisco Restrepo searched for and rediscovered the mine, and mining titles were granted to him and his associates in 1889. Through a series of transactions, the mining titles and land in the area came under the ownership of the Compañía de las Minas de Esmeraldas de Chivor, a Colombian entity in which Restrepo was involved. Only intermittent operational activities took place until 1912, when the German gem cutter and merchant Fritz Klein joined Restrepo with an increased focus on the operational side. Early mining by Restrepo and Klein yielded several finds promising enough for them to travel to Germany together in 1913 to seek investors (figure 1). Further work was curtailed one year later, however, when Restrepo died in 1914 and Klein, who had hoped to purchase the mine with German funding, was thwarted by the outbreak of World War I. When hostilities ended, Klein sought to recommence his efforts to buy the mine in 1919, but an American corporation, the Colombian Emerald Syndicate, Ltd., had in the interim obtained an option to purchase the mine. That option was exercised, and the mine was sold in December 1919 to two key representatives of the American group, Wilson E. Griffiths and Carl K. MacFadden. On behalf of the Colombian Emerald Syndicate, mining operations HISTORY OF THE CHIVOR EMERALD MINE, PART II (1924–1970): BETWEEN INSOLVENCY AND VIABILITY","PeriodicalId":12600,"journal":{"name":"Gems & Gemology","volume":"56 1","pages":"230-257"},"PeriodicalIF":2.6,"publicationDate":"2020-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48850206","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":"Optical Whitening and Brightening of Pearls: A Fluorescence Spectroscopy Study","authors":"Chunhui Zhoi, T. Tsai, Nicholas Sturman, Nanthaporn Nilpetploy, Areeya Manustrong, Kwanreun Lawanwong","doi":"10.5741/gems.56.2.258","DOIUrl":"https://doi.org/10.5741/gems.56.2.258","url":null,"abstract":"GEMS & GEMOLOGY SUMMER 2020 Optical brightening agents (OBAs) are chemical compounds that can absorb light in the ultraviolet and violet region of the electromagnetic spectrum and emit light in the blue region as fluorescence, due to their extended conjugation and/or aromaticity. They are sometimes called fluorescent brightening agents or fluorescent whitening agents, and have been frequently used to enhance the appearance of fabric and paper (Lanter, 1966; Leaver and Milligan, 1984; Esteves et al., 2004; Bajpai, 2018). While many types of brighteners are listed in the Colour Index (https://colour-index.com), only a handful are commercially important. Some examples are shown in figure 1. Photoluminescence is light emission from any form of matter after the absorption of photons. Fluorescence is a type of photoluminescence in which a molecule dissipates its absorbed energy through the rapid emission of a photon, while phosphorescence is the emission of radiation in a similar manner to fluorescence but on a longer timescale, so that emission continues after excitation ceases. Fluorescence can be generated by exciting the substance via a range of energy sources. The molecule in the substance absorbs the source energy and once excited moves from a lower electronic state to a higher one. Immediately after absorbing energy, it loses the energy by emitting a photon; this process of photon emission is called luminescence. Typically, fluores-","PeriodicalId":12600,"journal":{"name":"Gems & Gemology","volume":"56 1","pages":"258-265"},"PeriodicalIF":2.6,"publicationDate":"2020-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42447808","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 Evolution of Chinese Jade Carving Craftmanship","authors":"Mingying Wang, Guang-Yi Shi","doi":"10.5741/gems.56.1.30","DOIUrl":"https://doi.org/10.5741/gems.56.1.30","url":null,"abstract":"","PeriodicalId":12600,"journal":{"name":"Gems & Gemology","volume":"56 1","pages":"30-53"},"PeriodicalIF":2.6,"publicationDate":"2020-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47180284","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":"History of the Chivor Emerald Mine, Part 1 (1880-1925): From Rediscovery to Early Production","authors":"K. Schmetzer, G. Martayan, Jose Guillermo Ortiz","doi":"10.5741/gems.56.1.66","DOIUrl":"https://doi.org/10.5741/gems.56.1.66","url":null,"abstract":"GEMS & GEMOLOGY SPRING 2020 The foregoing outline of the story, as presently known, has been drawn largely from three books authored by individuals who led the mining activities at Chivor during different eras: German gem merchant Fritz Klein, South African mining engineer Peter W. Rainier, and American gem hunter and buyer Russell W. Anderton. All three men wrote in a style to highlight the adventurous nature of the work. Klein’s memoir covered the period from approximately 1911 to 1923 and was initially published in 1941, with a slightly updated version released in 1951. Rainier’s narrative chronicled from the second half of the 1920s to the early 1930s and was printed in 1942. Anderton’s work, coming to press in 1953 in the United States and 1954 in the United Kingdom, recounted activities of the late 1940s and early 1950s. The events presented in the three books have, since their respective publications, found their way in numerous variations into historical articles or descriptions as well as gemological, mineralogical, or geological papers.1 The rediscovery of Chivor by Francisco Restrepo (figure 1) and the clues that motivated his search have been a particularly popular topic. In general, the events described by Klein, Rainier, or Anderton have been accepted as facts in the literature, and only Klein’s description and dating of the rediscovery","PeriodicalId":12600,"journal":{"name":"Gems & Gemology","volume":"56 1","pages":"66-109"},"PeriodicalIF":2.6,"publicationDate":"2020-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41755148","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":"Rhodonite-Pyroxmangite from Tanatz Alp, Switzerland","authors":"F. Caucia, L. Marinoni, M. Riccardi, O. Bartoli, Maurizio Scacchetti","doi":"10.5741/gems.56.1.110","DOIUrl":"https://doi.org/10.5741/gems.56.1.110","url":null,"abstract":"","PeriodicalId":12600,"journal":{"name":"Gems & Gemology","volume":"56 1","pages":"110-123"},"PeriodicalIF":2.6,"publicationDate":"2020-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46048054","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 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}