Gems & Gemology最新文献

{"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}

{"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}