Gems & Gemology最新文献

{"title":"Geographic Origin Determination of Alexandrite","authors":"Ziyin Sun, Aaron C. Palke, J. Muyal, Dino G. DeGhionno, S. McClure","doi":"10.5741/gems.55.4.660","DOIUrl":"https://doi.org/10.5741/gems.55.4.660","url":null,"abstract":"GEMS & GEMOLOGY WINTER 2019 A fter the discovery of a gem mineral with unusual color-change behavior in the Russian Ural Mountains during the early 1830s, Swedish mineralogist Nils Adolf Erik Nordenskiöld named this new gem alexandrite in 1834 in honor of the future Czar Alexander II (Kozlov, 2005). This immediately created a royal and romantic aura around this variety of chrysoberyl. The most coveted alexandrites exhibit a lush green to greenish blue color in daylight and a warm, bright red shade in candlelight (Levine, 2008); some fine Brazilian and Indian alexandrite examples are shown in figures 1–3 and 6. This phenomenal color change is caused by the presence of trace Cr3+ substituting for Al3+ in the chrysoberyl crystal structure. Alexandrite is routinely described as “emerald by day, ruby by night.” It is a stone of duality—green or red, cool or warm, day or night (Levine, 2008). Because of its rare and attractive color-change phenomenon, alexandrite has been highly sought after and is one of the most valuable gemstones in the trade. Alexandrite, particularly fine-quality material, is also very scarce; it has generally been a byproduct of mining other major colored stones. Overall production statistics are hard to evaluate. It has been mined in Russia (Kozlov, 2005; Schmetzer, 2010), Tanzania","PeriodicalId":12600,"journal":{"name":"Gems & Gemology","volume":" ","pages":""},"PeriodicalIF":2.6,"publicationDate":"2019-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45669714","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 Gemological Characteristics of Pipi Pearls Reportedly from Pinctada Maculata","authors":"Nanthaporn Nilpetploy, Kwanreun Lawanwong, Promlikit Kessrapong","doi":"10.5741/GEMS.54.4.418","DOIUrl":"https://doi.org/10.5741/GEMS.54.4.418","url":null,"abstract":"“tiny” and is used to refer to the small, predominantly yellow or “golden” pearls that originate from the bivalve mollusk Pinctada maculata (Gould, 1846). As the smallest mollusk species in the Pinctada genus, Pinctada maculata rarely exceeds 5 cm when measured in the anterioposterior or dorsoventral positions. The mollusk lives in the Indo-Pacific Ocean, mostly around French Polynesia and the Cook Islands, where they are often found in association with the Pinctada margaritifera mollusk species (Strack, 2006). Pearls from Pinctada maculata often form in round to near-round shapes. As the name implies, the small shells produce small pearls that rarely exceed 8 mm in diameter (Krzemnicki, 2014). Based on GIA’s experience, 6 mm or under is more typical of the species. Pipi pearls are known to occur as natural pearls rather than cultured and, compared with other Pinctada species, are deemed rare. One report recorded only one gem-quality pearl found from a total of 355 mollusks (Passfield, 1997). In 1950, several cultured pearl experiments using Pinctada maculata reportedly took place but were unsuccessful (Segura et al., 2014). In the late 1990s, a few Pinctada maculata cultured blister pearls resulted from experiments in the waters off Penrhyn, an island in the northern atoll of the Cook Islands (Kessrapong et al., 2017). The nacre covering the bead nuclei did not fully overgrow the nuclei, however, and this attempt was not very successful. Some reports suggest that the Pinctada maculata mollusk is not abundant enough for","PeriodicalId":12600,"journal":{"name":"Gems & Gemology","volume":" ","pages":""},"PeriodicalIF":2.6,"publicationDate":"2019-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43134569","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":"An Early Byzantine Engraved Almandine from the Garibpet Deposit, Telengana State, India: Evidence for Garnet Trade Along the Ancient Maritime Silk Road","authors":"H. Gilg, K. Schmetzer, U. Schüssler","doi":"10.5741/GEMS.54.2.149","DOIUrl":"https://doi.org/10.5741/GEMS.54.2.149","url":null,"abstract":"","PeriodicalId":12600,"journal":{"name":"Gems & Gemology","volume":"322 ","pages":""},"PeriodicalIF":2.6,"publicationDate":"2018-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41276368","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":"Features of Synthetic Diamonds","authors":"S. eaton-magaña, C. Breeding","doi":"10.5741/GEMS.54.2.202","DOIUrl":"https://doi.org/10.5741/GEMS.54.2.202","url":null,"abstract":"synthetic diamond production: high-pressure, hightemperature (HPHT) growth and chemical vapor deposition (CVD) growth. It also provides the major gemological and spectroscopic features used to identify these lab-grown diamonds. The last few years have seen numerous advancements in synthetics: the rapid evolution in CVD technology, the ability to produce 10+ carat HPHT synthetics, and the proliferation of HPHT-grown colorless melee diamonds. The far left column of the chart focuses on features of melee-sized lab-grown diamonds (those less than 0.2 ct), while the far right column presents photos and photomicrographs of large (greater than 5 ct) faceted","PeriodicalId":12600,"journal":{"name":"Gems & Gemology","volume":" ","pages":""},"PeriodicalIF":2.6,"publicationDate":"2018-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44642801","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":"Black Diamonds from Marange (Zimbabwe): A Result of Natural Irradiation and Graphite Inclusions","authors":"Karen V. Smith, Elina Myagkaya, S. Persaud, Wuyi Wang","doi":"10.5741/gems.54.2.132","DOIUrl":"https://doi.org/10.5741/gems.54.2.132","url":null,"abstract":"have either natural or treated color origin. Natural black diamonds are usually colored by inclusions of sulfides, graphite, magnetite, hematite, or iron-bearing inclusions (e.g., Titkov et al., 2003). A rare natural diamond (of undisclosed geographic origin) colored by abundant brown radiation stains has previously been examined by GIA’s Carlsbad laboratory (Ardon, 2013). Treated black diamonds are often those that are heavily fractured naturally and then treated at low-pressure and hightemperature (LPHT) conditions to graphitize the fractures and turn them black (Hall and Moses, 2001; Notari, 2002). Artificial irradiation can also produce dark colors that appear black (Collins, 1982; Kitawaki, 2007). The Marange locality in eastern Zimbabwe is well known for producing diamonds that contain both octahedral and cuboid sectors (mixed-habit diamonds) where the cuboid sectors are visible to the eye due to abundant micro-inclusions of graphite (Rakovan et al., 2014; Smit et al., 2016). These micro-inclusions, informally known in the gem trade as “clouds,” give the diamonds a brown-gray appearance that lowers their value. Heat treatment of these lower-quality graphitecontaining Marange diamonds has the potential to introduce gem-quality treated black diamonds into the market. In natural diamonds, these graphite micro-inclusions are around 1 μm in diameter; during heating above 1200°C, they become larger. After annealing at 1700°C, the grain size increases to 11–16 μm, causing the cuboid sectors to appear opaque black (Eaton-Magaña et al., 2017). The challenge for gem laboratories is to confidently distinguish these treated black diamonds from naturally occurring black diamonds. Here our goal was to document a suite of untreated Marange diamonds, all with Fancy Dark brown to Fancy black GIA color grades, so that their characteristics could be distinguished from any suspected treated black diamonds. When viewing the samples, however, it became clear that the appearance of the these dark Marange diamonds was due not only to graphite clouds but also to abundant graphite needles and dark brown radiation stains occurring within surface-reaching fractures. BLACK DIAMONDS FROM MARANGE (ZIMBABWE): A RESULT OF NATURAL IRRADIATION AND GRAPHITE INCLUSIONS","PeriodicalId":12600,"journal":{"name":"Gems & Gemology","volume":" ","pages":""},"PeriodicalIF":2.6,"publicationDate":"2018-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44324623","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":"Cultured Pearls from Lake Kasumigaura: Production and Gemological Characteristics","authors":"A. Abduriyim","doi":"10.5741/gems.54.2.166","DOIUrl":"https://doi.org/10.5741/gems.54.2.166","url":null,"abstract":"Although today’s global freshwater cultured pearl market is mostly dominated by Chinese products, Japanese freshwater pearl cultivation started in 1935. Lake Biwa in Shiga Prefecture supplied pearls in a wide variety of colors to the domestic and international markets until 1982. Due to water pollution and the depletion of Hyriopsis schlegelii , some of the pearl farms relocated to Lake Kasumigaura in Ibaraki Prefecture starting in 1962. Today the annual production of large nucleated cultured pearls at Lake Kasumigaura is below 40 kg, a small portion of which are supplied to the international market. This report investigates “Kasumiga pearl” culturing and describes the quality and production volume. UV-visible spectroscopy, fluorescence testing, and chemical analysis were performed on pearls in six different colors collected from the Hyriopsis schlegelii × Hyriopsis cumingii hybrid mollusk farmed at Kasumigaura.","PeriodicalId":12600,"journal":{"name":"Gems & Gemology","volume":" ","pages":""},"PeriodicalIF":2.6,"publicationDate":"2018-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44992924","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":"Gemological Characterization of Sapphires from Yogo Gulch, Montana","authors":"Nathan D. Renfro, Aaron C. Palke, R. Berg","doi":"10.5741/GEMS.54.2.184","DOIUrl":"https://doi.org/10.5741/GEMS.54.2.184","url":null,"abstract":"Gulch, Montana, have produced millions of carats of rough sapphire. Much of that has yielded very small finished stones, and faceted stones over 1 ct are highly prized (figure 1). The largest known Yogo sapphire crystal was found in 1910 and weighed 19 ct (Howard, 1962a) The shape of Yogo rough is often in the form of flat tabular crystals that offer a very low yield. Large stones over 1 ct are almost exclusively collector stones, with the provenance having a significant impact on value. While there are other significant sources of gem-quality sapphire in Montana—including Rock Creek, Missouri River, and Dry Cottonwood Creek—Yogo sapphires are unique among these and other sapphire deposits worldwide (figure 2). Virtually all of the material produced has a desirable even blue to violet or purple color, often with higher clarity than sapphires from other deposits (Yaras, 1969) (figure 3). Yogo sapphires do not require heat treatment, offering a virtual guarantee of their untreated nature. They also possess a unique trace-element chemistry and an inclusion suite that makes them easily recognizable to the experienced gemologist. HISTORY In 1895, the Yogo sapphire deposit was accidentally discovered by a gold prospector named Jake Hoover. Hoover sought financial backing from two friends— local banker S.S. Hobson and Dr. Jim Bouvet, a veterinarian from Chicago—and the three formed a mining partnership. While recovering gold from his","PeriodicalId":12600,"journal":{"name":"Gems & Gemology","volume":" ","pages":""},"PeriodicalIF":2.6,"publicationDate":"2018-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41499561","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 Blue, Gray, and Violet Diamonds: Allure of the Deep","authors":"S. eaton-magaña, C. Breeding, J. Shigley","doi":"10.5741/gems.54.2.112","DOIUrl":"https://doi.org/10.5741/gems.54.2.112","url":null,"abstract":"","PeriodicalId":12600,"journal":{"name":"Gems & Gemology","volume":" ","pages":""},"PeriodicalIF":2.6,"publicationDate":"2018-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47741425","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 Green Diamonds: A Beautiful Conundrum","authors":"C. Breeding, S. eaton-magaña, J. Shigley","doi":"10.5741/GEMS.54.1.2","DOIUrl":"https://doi.org/10.5741/GEMS.54.1.2","url":null,"abstract":"valued of gemstones due to their beauty and rarity. Interestingly, the rarest of diamond colors correlate with the three most popular choices for favorite color, in general—green, blue, and pink to red. The unique set of conditions in nature that produce the structural imperfections (defects in the lattice of carbon atoms; see Shigley and Breeding, 2013) responsible for the most vibrant hues of green, blue, and pink/red diamonds are so uncommon that many people are not even aware these stones exist. Over the last ten years, diamonds with these natural color components comprised less than 0.4% of all diamonds submitted to GIA’s laboratories worldwide (including both fancy-color and those on the D–Z scale). Pure hues of green, blue, or red are even rarer, accounting for less than 0.07% of all diamonds examined. Many articles published over the last 20 years in the scientific and gemological literature have looked at specific properties of colored diamonds, quality grading characteristics, or particular treatments. Few researchers, however, have had the opportunity to examine large quantities of similarly colored natural diamonds and report on their distinctive characteristics. Colored diamonds are extremely rare and, consequently, highly valued. This value factor means that laboratory reports are requested for most colored dia-","PeriodicalId":12600,"journal":{"name":"Gems & Gemology","volume":" ","pages":""},"PeriodicalIF":2.6,"publicationDate":"2018-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43796387","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":"DNA Techniques Applied to the Identification of Pinctada Fucata Pearls from Uwajima, Ehime Prefecture, Japan","authors":"K. Saruwatari, Michio Suzuki, Chunhui Zhou, Promlikit Kessrapong, Nicholas Sturman","doi":"10.5741/GEMS.54.1.40","DOIUrl":"https://doi.org/10.5741/GEMS.54.1.40","url":null,"abstract":"","PeriodicalId":12600,"journal":{"name":"Gems & Gemology","volume":" ","pages":""},"PeriodicalIF":2.6,"publicationDate":"2018-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47907386","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}