Gems and Gemology

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The first decade of the 2000s continued the trend of using more powerful analytical instruments to solve gem identification problems. Advances in gem treatment and synthesis technology, and the discovery of new gem sources, led to urgent needs in gem identification. These, in turn, led to the adaptation of newer scientific instruments to gemology. The past decade witnessed the widespread use of chemical microanalysis techniques such as LA-ICP-MS and LIBS, luminescence spectroscopy (particularly photoluminescence), real-time fluorescence and X-ray imaging, and portable spectrometers, as well as the introduction of nanoscale analysis. Innovations in laser mapping and computer modeling of diamond rough and faceted stone appearance changed the way gemstones are cut and the manner in which they are graded by gem laboratories.
Kyanite derives its name from the Greek word for blue, due to its typical color. Gem-quality green kyanite has also been seen (e.g., Winter 2001 GNI, pp. 337-338), and colorless or yellow varieties have occasionally been faceted. Recently, however, orange kyanite has appeared in the gem market. The material was mined at Loliondo, Tanzania, near the area that recently produced fine crystals of spessartine (see, e.g., Spring 2008 GNI, pp. 76-78).
Since late 2007, rubies and sapphires have been mined by hand methods from both eluvial and primary deposits at Winza in central Tanzania. The gem corundum is related to "dikes" of amphibolitic rocks that belong to the Paleoproterozoic Usagaran Belt. Based on crystal morphology, Winza corundum is subdivided into two types: prismatic-tabular-rhombohedral and dipyramidal. In general, medium red and dark (orangy) red top-quality rubies are rhombohedral. Pinkish red and purplish red rubies, as well as pink, purple, and blue (often strongly color zoned) sapphires are, for the most part, dipyramidal. The top-quality rubies are characterized by a distinct assemblage of long tube-, fiber-, needle-, or hair-like inclusions containing an orange-brown material (most likely limonite). The lower-quality material generally contains a larger amount of solid inclusions (mostly amphibole crystals), fissures, and growth features. Unique to corundum from this locality are bluish violet color zones oriented parallel to the prism and basal pinacoid, and occasionally also parallel to rhombohedral and dipyramidal faces. The relatively high Fe content of Winza rubies separates them from most other natural and almost all synthetic counterparts.
Data for global annual rough diamond production (both carat weight and value) from 1870 to 2005 were compiled and analyzed. Production statistics over this period are given for 27 diamond-producing countries, 24 major diamond mines, and eight advanced projects. Historically, global production has seen numerous rises - as new mines were opened - and falls - as wars, political upheavals, and financial crises interfered with mining or drove down demand. Production from Africa (first South Africa, later joined by South-West Africa [Namibia], then West Africa and the Congo) was dominant until the middle of the 20th century. Not until the 1960s did production from non-African sources (first the Soviet Union, then Australia, and now Canada) become important Distinctions between carat weight and value affect relative importance to a significant degree. The total global production from antiquity to 2005 is estimated to be 4.5 billion carats valued at US$300 billion, with an average value per carat of $67. For the 1870-2005 period, South Africa ranks first in value and fourth in carat weight mainly due to its long history of production. Botswana ranks second in value and fifth in carat weight although its history dates only from 1970. Global production for 2001-2005 is approximately 840 million carats with a total value of $55 billion, for an average value per carat of $65. For this period, USSR/Russia ranks first in weight and second in value, but Botswana is first in value and third in weight just behind Australia.
Chemical and microscopic examination of the first gem-quality synthetic emeralds of facetable size proves that Prof. Richard Nacken grew two main types of emerald by flux methods in the mid-1920s. One of these two types, grown with colorless beryl seeds in molybdenum-bearing and vanadium-free fluxes, has not previously been mentioned in the literature and would appear to be unknown to gemologists. The other main type, which has already been described in gemological publications, was grown from molybdenum-and vanadium-bearing fluxes. In drawing these conclusions, rough and faceted synthetic emeralds produced by Nacken were available for study from two principal sources: the Deutsches Museum in Munich, to which Nacken had donated samples in 1961, and family members who had inherited such crystals. Chemical, morphological, and microscopic properties are given, and circumstances concerning the developmental history of the Nacken production, including the possibility of collaboration with IG Farben (a subject of past speculation), are discussed as well. The latter has recently been elucidated by the discovery of original documents from the IG Farben gemstone plant, preserved in the Archives of the German Federal State of Saxony-Anhalt.
The 1980s witnessed great development in the application of new technologies to gemology These technologies provided new or better ways to grow synthetic gem materials and to treat natural ones. They also permitted numerous breakthroughs in gem identification, in areas where classical gemological methods were no longer sufficient to make a positive identification. In particular, various types of spectroscopy proved to be of important practical value, for example, infrared absorption, X-ray fluorescence, Raman scattering, and cathodoluminescence.
This article provides an overview of the many changes that took place in how jewelry was designed, manufactured, and marketed during the last decade. Driven by a highly competitive market that favored the unique, designers created innovative cuts for diamonds and colored stones. The use of gem materials in the '90s was marked by a greater demand for fancy-color diamonds, colored stones in dramatic combinations, and large and multicolored cultured pearls. In precious metals, the emphasis shifted toward platinum and other white metals. Designer jewelry took on a vanety of distinctive setting styles, textures, and motifs. As designers sought to distinguish themselves through name recognition, the branding of diamonds and finished jewelry became a major force. Jewelry worn by entertainers and promoted in the mass media touched off instant trends, which the new marketplace of television shopping networks and the Internet was able to accommodate directly.
In the last decade, technology has unproved how we synthesize, process, identify, and otherwise study gem materials. Significant trends include: the widespread availability of computerized communication; the application of synthesis techniques to gem treatments; the increased prominence of treated synthetics; the greater need for expensive instrumentation to solve gem problems in general, and the broader availability of small dedicated instruments to solve specific problems; and the adaptation of techniques from other sciences. Potentially applicable technology must be evaluated critically to assess its usefulness and appropriateness to solve a particular gemological problem.
The past decade saw growth in gem exploration, production, and marketing worldwide. Important colored stone-producing regions included: Southeast Asia (Myanmar, Thailand, and Vietnam), Africa (Tanzania, Kenya, Zimbabwe, Nigeria, and Namibia, as well as Madagascar), South America (Brazil and Colombia), central and southern Asia (Sri Lanka, India, Afghanistan, Pakistan, Russia, and China), and Australia. The major sources for diamonds were Australia, central and southern Africa (Botswana, South Africa, Namibia, Angola, and Zaire), and Russia (mainly in the Republic of Sakha), with exciting discoveries in northern Canada. Cultured pearls from French Polynesia, Australia, and China became increasingly important, as production from Japan declined. This article provides a comprehensive overview of those gem deposits that were either new or remained commercially significant in the last decade of the 20th century.
The 1990s witnessed important developments in the commercial viability of gem-quality synthetic diamonds. Improvements in, and new applications for, existing synthesis processes in the production of colored stones such as ruby, sapphire, emerald, quartz, and alexandrite have had an impact as well. The development and commercialization of a variety of new synthetics and simulants, such as synthetic moissanite and flux-grown synthetic spinel, also played an important role in shaping the past decade for the gem and jewelry industry.
Gemstone enhancements and their disclosure became the most important gemological issue for the jewelry trade in the 1990s. Growing public awareness of treatments and the greater use of sophisticated technology to enhance the color and/or apparent clarity of gem materials brought to the forefront the need to maintain (or in some cases regain) the consumer confidence that is so vital to this industry. The treatments with the greatest impact were those that affected the gems that were commercially most important: heat and diffusion treatment of ruby and sapphire, "oiling" of emeralds, and fracture filling of diamonds. At the end of the decade, the decolorization of diamonds by high pressure and high temperature posed one of the greatest identification challenges ever faced by gemologists worldwide. Yet most other gem materials were also subjected to enhancements - ranging from traditional processes as with quench-crackled quartz to novel "impregnation" techniques such as the Zachery treatment of turquoise. This article discusses the treatments that were new or prominent during the '90s and suggests methods for their detection.
Madagascar was one of the largest producers of sapphires—in a variety of colors—in the 2000s. The stones shown here weigh ~3–5 ct. Courtesy of Menavi International; photo by Robert Weldon.  
Australia's Argyle mine is the world's largest single diamond producer by volume. Since the 1980s, the deposit has been mined in a large open pit; the processing plant and west pit wall are shown here. Over the next few years, mining will move underground. This 2009 photo is courtesy of Rio Tinto Diamonds.  
This two-strand necklace, which was owned by the Maharajas of Baroda in western India, consists of 68 natural pearls from 9.47 to 16.04 mm. At the April 2007 Christie's New York auction, the necklace and its accompanying ear pendants, brooch, and ring sold for $7,096,000, setting a world auction record for natural pearl jewels. Courtesy of Christie's Images Ltd. 2010.  
While the past decade saw some impressive discoveries of diamonds and colored stones (such as corundum, spinel, garnet, and tourmaline), it also witnessed reduced gem production in many areas as a result of high development costs, environmental considerations, and the downturn in the global economy. With legal and ethical restrictions on the trade in gems from some nations, and with premium market values paid for certain stones from particular sources, "locality of origin" determinations took on increased importance for some colored stones such as ruby, sapphire, emerald, and copper-bearing tourmaline. This article reviews the geographic sources of diamonds and colored stones, as well as the areas of production for both natural and cultured pearls, that were commercially important during the years 2001-2010. Maps of most of the important gem-producing regions of the world are included on an accompanying wall chart.
The first decade of the 2000s brought a constant flow of previously known synthetics into the marketplace, but little in the way of new technology. The biggest development was the commercial introduction of faceted single-crystal gem-quality CVD synthetic diamonds. A few other interesting and noteworthy synthetics, such as Malossi hydrothermal synthetic emeralds and Mexifire synthetic opals, also entered the market. Identification of synthetic gem materials continued to be an important function of-and, in some cases, challenge for-gemologists worldwide.
Advances in technology and increased demand for lower-priced gem materials contributed to the proliferation of new treatments throughout the first decade of the 2000s. The developments that made the most difference were the diffusion treatment of corundum with beryllium, diffusion of copper into feldspar, clarity enhancement of ruby and diamond, and heat treatment of diamond, ruby, and sapphire. Gemological laboratories and researchers have done their best to keep up with these treatments, and the jewelry trade has struggled with how to disclose them. This article summarizes these developments and the methods used to identify the various enhancements
Top-cited authors
E. Fritsch
  • Institut des Materiaux Jean Rouxel
John I. Koivula
  • Gemological Institute of America
Stefanos Karampelas
Wuyi Wang
  • Gemological Institute of America (GIA)
Emmanuel Fritsch
  • University of Nantes