Andy H. Shen

Lab-Grown Colored Diamonds From Chatham Created Gems

developments in recent years has been the commercial availability of jewelry-quality synthetic diamonds. What for almost three decades was primarily an industrial or research product is now becoming a commodity in the gem and jewelry marketplace. In addition to the products being offered by such companies as the Gemesis Corp. and Lucent Diamonds, Chatham Created Gems of San Francisco, California, has introduced a line of synthetic diamonds from a new source (figure 1). This article presents results of our examination of a large group of these high pressure/high temperature (HPHT) laboratory-grown diamonds in yellow, blue, green, and pink colors showing a full range of saturation, from weak to strong. Our examination indicates that most of the yellows and blues represent “as-grown” colors (i.e., those produced by nitrogen and boron impurities during diamond crystallization), while the greens and pinks are the result of either growth or growth plus post-growth treatment processes (i.e., irradiation, with or without subsequent heating). A single manufacturer is supplying Chatham Created Gems with approximately 500 carats of synthetic diamond crystals per month, with future increases in production planned (T. Chatham, pers. comm., 2004). The material is faceted in China into cut goods that range from a few points (melee) to as large as 2 ct. Chatham Created Gems is the sole distributor of this material for jewelry purposes. Previous gemological reports on synthetic diamonds produced in Russia and sold by Mr. Chatham (see, e.g., Scarratt et al., 1996) may not be applicable to the new HPHT-grown material described here, which is grown in Asia with a non-BARS press. This article provides information on material from all four color categories of this new product, including descriptions of green and pink synthetic diamonds, which have not been reported on extensively in the gemological literature. Most of the green samples display this color because they contain both blue and yellow growth sectors. Some of this new material displays hues and weaker saturations that more closely resemble natural diamonds

Identification of "Chocolate Pearls" Treated by Ballerina Pearl Co.

appearance, cultured pearls are frequently treated by bleaching, dyeing (such as with silver nitrate), or exposure to radiation. A “new” color for cultured pearls was introduced to the market in 2000 (figure 1; see, e.g., “U.S. gem labs...,” 2004; Zachovay, 2005; “GIA identifies...,” 2006; Strack, 2006; “Study shows...,” 2006). The induced brown color reportedly results from the bleaching of “black” Tahitian cultured pearls. These are now known in the trade as “chocolate pearls” and have become quite popular (Sanchez, 2004). They are available from several sources, including Ballerina Pearl Co. in New York and Shanghai Gems SA in Geneva (“Better techniques,” 2006). The companies treating these cultured pearls assert that no color is added during treatment (Sanchez, 2004). However, it is unlikely that all the “chocolate pearls” marketed today have been treated using the same technique. To better understand the treatment process being used by one company (Ballerina Pearl Co.) and how these new products can be identified, we analyzed the gemological, chemical, and spectroscopic properties of several of these “chocolate pearls” as well as silver-dyed Tahitian cultured pearls and untreated gray and brown Tahitian cultured pearls. In addition, we asked Ballerina Pearl Co. to treat four Tahitian cultured pearls specifically for this study.

An Updated Chart on The Characteristics of HPHT-Grown Synthetic Diamonds

GEMS & GEMOLOGY WINTER 2004 303 lmost a decade ago, Shigley et al. (1995) published a comprehensive chart to illustrate the distinctive characteristics of yellow, colorless, and blue natural and synthetic diamonds. The accompanying article reviewed synthetic diamond production at the time, and discussed how the information presented on the chart was acquired and organized. It also included a box that provided a “practical guide for separating natural from synthetic diamonds.” The chart was distributed to all Gems & Gemology subscribers, and a laminated version was subsequently made available for purchase. Since that time, and especially within the past several years, the situation of synthetic diamonds in the jewelry marketplace has become more complicated. Lab-created colored diamonds are now being produced in several countries (including Russia, the Ukraine, Japan, the U.S., and perhaps China and elsewhere), although the quantities continue to be very limited. And today they are being sold specifically for jewelry applications (figure 1), with advertisements for synthetic diamonds seen occasionally in trade publications and other industry media. Recent inquiries to three distributors in the U.S.— Chatham Created Gems of San Francisco, California; Gemesis Corp. of Sarasota, Florida; and Lucent Diamonds Inc. of Lakewood, Colorado— indicate that their combined production of crystals is on the order of 1,000 carats per month (mainly yellow colors), a quantity that does not meet their customer demand. The synthetic diamonds currently in the gem market are grown at high pressure and high temperature (HPHT) conditions by the temperature-gradient technique using several kinds of high-pressure equipment (belt, tetrahedral, cubic, and octahedral presses as well as BARS apparatuses), and one or more transition metals (such as Ni, Co, and Fe) as a flux solvent/catalyst. Typical growth temperatures are 1350–1600°C. Some lab-grown diamonds are being subjected to post-growth treatment processes (such as irradiation or annealing, or both) to change their colors (and, in some cases, other gemological properties such as UV fluorescence). Thus, the gemologist is now confronted with the need to recA AN UPDATED CHART ON THE CHARACTERISTICS OF HPHT-GROWN SYNTHETIC DIAMONDS

Developments in Gemstone Analysis Techniques and Instrumentation During the 2000s

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.

Solution-Generated Pink Color Surrounding Growth Tubes and Cracks in Blue to Blue-Green Copper-Bearing Tourmalines from Mozambique

RAPID COMMUNICATIONS GEMS & GEMOLOGY SPRING 2009 ver the past year, we examined nine blue to bluegreen Cu-bearing tourmalines from Mozambique that contained surface-reaching growth tubes and cracks that were outlined or “sleeved” with obvious pink color zones (e.g., figure 1). These gems came from four different gem dealers over the course of the year. The first gem, from Simon Watt, was a 14.12 ct blue heart-shaped mixed cut measuring 15.82 × 13.68 × 10.82 mm that was purportedly from Mozambique. As shown in figure 2, this tourmaline contained a surface-reaching growth tube sleeved by a pink zone of moderate intensity. Soon thereafter, Bill Vance and David Freeland Jr. sent us the 27.63 ct cushion mixed cut shown in figure 1. This gem, also said to be from Mozambique, measured 17.82 × 17.13 × 12.95 mm. It contained a surface-reaching macroscopic growth tube under its table that was enveloped along its length by an intense zone of pink (almost red) color, which created a clear contrast against the blue bodycolor of its host. The third and largest of the gems came into the GIA Laboratory for identification and origin determination. This tourmaline was a blue-green pear-shaped modified brilliant cut that weighed 33.26 ct and measured 24.34 × 19.88 × 12.89 mm. It contained several thin surface-reaching growth SOLUTION-GENERATED PINK COLOR SURROUNDING GROWTH TUBES AND CRACKS IN BLUE TO BLUE-GREEN COPPER-BEARING TOURMALINES FROM MOZAMBIQUE