Publish Year: 2000 Title: Pre-Columbian Gems and Ornamental Materials from Antigua, West Indies Abstract: Two archeological sites that were discovered recently on the island of Antigua appear to have had flourishing lapidary industries. Excavation of these sites, which date to about 250–500 AD (Saladoid period), has revealed beads, pendants, and “zemis” made from a variety of materials, with shell being the most abundant. All of the unworked materials (e.g., shell, carnelian, and diorite) are of local origin. However, amethyst, nephrite, serpentine, and turquoise were found only as finished gems; these are not local and imply that trade or exchange existed between Antigua and other parts of the Caribbean and possibly the Americas during Saladoid time. @topic:9


Publish Year: 2019 Title: Ornamental Jadeites from the Levoketchpel Deposit in the Polar Urals of Russia Abstract: Figure 1. Five of the 10 jadeite samples from the Levoketchpel deposit (back row) and four jadeites reportedly from the Polar Urals (front row). Photo by Shunsuke Nagai.

Although most jadeites on the market are from Myanmar, other sources include Guatemala, Japan, Kazakhstan, and Russia. Russian jadeites have been studied using geological and petrological approaches (e.g., A.M. Fishman, Gems in the North Ural and Timan, Geoprint, Syktyvkar, 2006, pp. 1–88; F. Meng et al., “Jadeitite in the Syum-Keu ultramafic complex from Polar Urals, Russia: insights into fluid activity in subduction zones,” European Journal of Mineralogy, Vol. 28, No. 6, 2016, pp. 1079–1097), but their gemological characteristics are still unclear. To date, several jadeite deposits have been found within some ultramafic complexes at the Polar Urals (Fishman, 2006). In August 2013, the authors visited a closed jadeite mine at the Levoketchpel deposit in the Voykar-Syninsky ultramafic complex of the Polar Urals to collect samples (figure 1). Here we describe the gemological and trace element chemistry of these jadeites.

Figure 2. Left: A geological map of the Voykar-Syninsky ultramafic complex in the Polar Urals. Modified from Meng et al. (2011). A: A whitish jadeite dike within serpentinized peridotite at the Levoketchpel area. The hammer is 40 cm long. Photo by Dimitri Kuznetsov. B: A jadeite boulder with surrounding phlogopite-rich rock. Photo by Makoto Miura.
The jadeites were found as dikes within serpentinized peridotite (figure 2A). The Levoketchpel deposit was reportedly discovered in 1959 (V.F. Morkovkina, “Jadeites in the hyperbasites of the Polar Urals,” Izvestiya Akademii Nauk SSSR (Seriya Geologicheskaya), 1960, Vol. 4, pp. 103–108). Mining at this area was done on a small scale, and the quality was low. In the outcrop, the jadeite dike is surrounded by phlogopite-rich rock (figure 2B) and peridotite. The Levoketchpel jadeites are translucent to opaque, and whitish to pale green and vivid green with a mottled color distribution. The samples showed a mosaic to fibrous aggregate structure. We collected 10 samples from the jadeite dike (five of these are shown in figure 1) and rubbles produced during mining. For the gemological observation, advanced testing, and quantitative laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) analysis of trace elements, we prepared wafers and thin sections (figure 3). Standard gemological testing revealed RI values of 1.66 to 1.67 and hydrostatic SG values of 3.2 to 3.4. In a handheld spectroscope, the whitish and pale green zones in the samples showed fine chrome lines at 630, 655, and 691 nm, and the diagnostic 437 nm line. These results strongly suggested that the samples were all jadeite.

Figure 3. Two jadeite samples from the Levoketchpel deposit, measuring 3.4 cm and 1.8 cm wide. Photo by Shunsuke Nagai.
EDXRF testing also indicated that the samples were composed mainly of jadeites. The pale green jadeites were characterized by a low CaO/Na2O ratio of 0.20 to 0.26, and a relatively high Al2O3/Fe2O3 ratio of 11.03 to 20.14. The vivid green parts tended to be slightly rich in Ca (CaO/Na2O ratio, 0.32 to 0.34), and the compositional ranges are suited for jadeite (Al2O3/Fe2O3 ratio of 10.73 to 20.14). Vivid green zones were slightly higher in Cr2O3, 0.06 to 0.16 wt.%, than the whitish and pale green samples (Cr2O3 up to 0.01 wt.%).
Careful observation and Raman spectroscopic analysis suggested that the samples were mainly composed of fine jadeite grains with minor amounts of omphacite, natrolite, feldspar, phlogopite, zircon, and chromite. Natrolite was found as the interstitial phase between jadeite grains. Jadeite crystals surrounding chromite crystals tended to be rich in green color. This green color concentration around chromite crystals is probably due to chromium diffusion from chromite during the jadeite’s formation. The coexisting mineral assemblage observed is consistent with previous petrological studies (e.g., G.E. Harlow and S.S. Sorensen, “Jade (nephrite and jadeite) and serpentinite: metasomatic connections,” International Geological Review, Vol. 12, 2005, pp. 49–68). In UV-Vis spectra, vivid green regions of the jadeites from Levoketchpel show an Fe3+ band and strong chromium bands in the 550–700 nm range. Similar results were also reported from jadeites from the Polar Urals (A. Abduriyim et al., “Japanese jadeite: History, characteristics, and comparison with other sources,” Spring 2017 G&G, pp. 48–67).

Figure 4. Trace element characteristics of the Levoketchpel jadeites. (A) Primitive mantle–normalized trace element patterns for green jadeites. (B) Chondrite-normalized rare earth element (REE) patterns for green jadeites. The detection limit is shown by the gray dashed line. Samples in this study are shown in red and compared with jadeites from the Pusyerka deposit at the Syum-Keu complex, the Polar Urals (Meng et al., 2016), Myanmar, Guatemala, and Japan (Abduriyim et al., 2017; Abduriyim et al., unpublished data). Primitive mantle and chondrite values for normalizing are from Sun and McDonough (1989).
Trace element compositions (Rb, Sr, Y, Zr, Nb, Ba, and the rare earth elements Hf, Ta, W, and U) were analyzed by LA-ICP-MS for 10 samples (70 spots total). Four of the samples had both whitish to pale green and vivid green zones. Chemical analyses were conducted on five spots for each of these zones. The whitish to pale green jadeites were depleted in REEs, while the vivid green zones tended to be richer in REEs. We calculated the primitive mantle–normalized trace element patterns and the chondrite-normalized REE patterns (figure 4) of the vivid green Levoketchpel jadeites (W.F. McDonough and S.-S. Sun, “The composition of the earth,” Chemical Geology, Vol. 120, 1995, pp. 223–253) and compared them to jadeites with similar color ranges from another jadeite locality in the Polar Urals (the Pusyerka deposit in the Syum-Keu ultramafic complex; Meng et al., 2016), Myanmar, Guatemala, and Japan (Abduriyim et al., 2017; Abduriyim et al., unpublished data). The primitive mantle–normalized trace element patterns of the Lavoketchpel jadeites reveal strong positive anomalies of Sr, Zr, and Nb (figure 4A). Such enrichment of the large-ion lithophile elements (LILE) and the high field strength elements (HFSE) in jadeites have been reported previously in jadeites from other localities (e.g., G.E. Harlow et al., “Jadeites and plate tectonics,” Annual Review of Earth and Planetary Sciences, Vol. 43, 2015, pp. 105–138). In these patterns, green jadeites from each locality show a very close overlap. In the chondrite-normalized patterns, the Levoketchpel jadeites show a right-downward slope: the light rare earth element (LREE) La, Ce, Nd, and Sm concentrations tended to be higher than the heavy rare earth element (HREE) Eu, Gd, Dy, Y, Er, Yb, and Lu contents (figure 4B). The Levoketchpel jadeites are depleted in HREE relative to the Pusyerka jadeites. Jadeites from Myanmar and Guatemala have higher total REE concentrations than the Polar Ural and Japanese jadeites (figure 4B). Burmese jadeite patterns show a gentle right-downward slope from La to Lu, and Guatemalan jadeites tend to be enriched in HREE. The Levoketchpel jadeites and some Japanese jadeites display a similar slope in REE concentration, although the former tend to be relatively depleted in HREE. @topic:9


Publish Year: 2018 Title: Colored Stones and Pearls Abstract: Figure 1. A single tourmaline fiber contains three distinct chemical zones, each recording the fluid composition at the time of growth. Between zones, fluids dissolved preexisting tourmaline to provide components for the new species in equilibrium. This overall compositional trend mimics the fractionation trend in a pegmatite.

Tourmaline: A Gemstone’s Guide to Geologic Evolution of the Earth’s Crust
Barbara L. Dutrow
Louisiana State University, Baton Rouge
Tourmaline is recognized as an important gemstone and a stunning collector’s item, and each crystal contains geochemical fingerprints that can elucidate an astonishing array of geological processes. Through field, experimental, analytical, and theoretical studies, the rich chemical signature encapsulated in tourmaline is being unraveled and revealed. Because of its widely varying chemistry, tourmaline is particularly adept at recording the host-rock environment in which it grew, be it a melt, a marble, or a former subduction zone. In addition, it can record the thermal and baric conditions of its growth, acting as a geothermometer or geobarometer. A crystal that exhibits sector zoning can provide the complete temperature history of its growth, serving as a single-mineral thermometer. Other tourmaline compositions may reveal the absolute age of a geologic event that produced tourmaline formation.
Tourmaline also excels at recording the evolution of the fluids with which it interacts. Its essential ingredient is boron (B), a fluid-mobile element. Thus, tourmaline is nature’s boron recorder. Tourmaline formation and growth reflects the availability of boron to the rock system. Fluids can be sourced internally from the melt or from the breakdown of other B-bearing minerals, or fluids with boron can infiltrate the rock system from external sources. In each case, tourmaline preserves signatures of these events in the form of new growth, dissolution of preexisting tourmaline with growth of a new tourmaline composition (tourmaline cannibalizing itself to form anew), or replacement of another mineral. Tourmaline species may hint at fluid compositions. For example, species ranging from oxy-dravite to povondraite are typically found in saline, oxidizing environments and are indicators of these fluids in the geologic past. The deep green chrome (Cr) tourmalines reflect an unusual environment enriched in both Cr and B. Similarly, tourmaline compositions may reflect specific components of the fluid phase and, in some cases, provide quantitative estimates of fluid compositions (figure 1). Fitting data to tourmaline–fluid partitioning experiments permits calculation of the sodium (Na) concentrations in the coexisting fluid phase, and suggests that the alkali species of tourmaline—elbaite, dravite, and schorl—form in fluids with greater than 0.30 mol/L Na, whereas the vacancy-dominant species, foitite and oxy-foitite, are stable in fluids with less than 0.25 mol/L Na. Once formed, tourmaline resists attack by corrosive acidic fluids.
Combining these features, tourmaline is a mineral containing unparalleled information on the environment in which it grew and the geologic processes responsible for it. An advantage of tourmaline as a geologic record keeper is that once these signals are incorporated, they are retained throughout the “lifetime” of the grain due to its slow volume diffusion. In some extraordinary cases, a single tourmaline grain can record its complete “life cycle,” from its original crystallization from a cooling magma deep within the crust through the rock’s uplift, cooling, and partial destruction during erosion to deposition and reburial followed by heating and regrowth in a new geologic environment. The oldest known tourmaline dates back about 3.7 billion years, and it retains the chemical growth zones from its formation in early Earth, thus elucidating the presence of boron-bearing fluids and continental crust during that time.
The totality of this embedded geologic history is the result of tourmaline’s flexible crystal structure, which incorporates a substantial number of chemical elements and isotopes, across a wide array of sizes and valence states, and in quantities from major to trace amounts. Such variable chemistry not only produces a kaleidoscope of colored gemstones but also permits tourmaline to be stable over nearly all pressure and temperature conditions found in Earth’s crust, and to develop in all major rock types, from solidified igneous melts and pegmatites to metamorphic and sedimentary rocks. This chemical variability classifies tourmaline as a mineral supergroup, currently consisting of 33 different species, each with a different and unique story.
Telling tourmaline’s story typically requires chemical compositions to be obtained. New methods involving laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) and infrared and Raman spectroscopy, along with well-established techniques such as electron microprobe analysis, provide such information to gemologists and geologists. For tourmaline, a mineral with one of the most exquisite arrays of color, geologists tease apart the complex clues it harbors, and gemologists can use these to tell the story of each gemstone. The widespread occurrence of the tourmaline minerals and their ability to imprint, record, and retain information make them a valuable tool for investigating Earth’s geological processes. Tourmaline is the ultimate keeper of geologic information, a geologic DVD.
“Boehmite Needles” in Corundum Are Rose Channels
Franck Notari1, Emmanuel Fritsch2 (presenter), Candice Caplan1, and Thomas Hainschwang1
1GGTL-Laboratories Switzerland, Geneva, and Balzers, Liechtenstein
2Institut des Matériaux Jean Rouxel and University of Nantes, France
Crystallographically oriented, linear inclusions in corundum are often referred to as “boehmite needles” or “polycrystalline boehmite” (boehmite is the orthorhombic aluminum hydroxide g-AlOOH). These inclusions are oriented along the edges of the rhombohedral faces and form angles of about 90°. They are always found at the intersection of twin lamellae, formed by twinning along the rhombohedral faces. They contain apparently polycrystalline material tentatively identified (at least in some cases) as boehmite. These are common in natural corundum and sometimes used as a criterion to separate natural from synthetic corundum.
Boehmite can be recognized through its infrared absorption. The great majority of the “needle”-containing gem corundum showed no boehmite infrared absorption, thus leading us to believe that these inclusions have a different origin. Microscopic observation reveals three aspects: some are lath- or ribbon-shaped, others are clearly negative crystals, and sometimes they appear as dotted lines. At the outcrop of the feature on the gem’s surface there is most commonly a void that can be followed into the gem, so the “needle” is essentially empty. This feature was also documented in a flux-grown synthetic ruby with no boehmite infrared signal. These channels are favored during titanium diffusion and take on color first, as diffusion is much faster in the empty space.

Figure 1. Left: Rose channels at the intersection of twin lamellae in a 7.17 ct color-change sapphire from East Africa, viewed in partially polarized light. Right: Detail of the same zone in reflected light, illustrating the fact that these channels are empty. Photos by Franck Notari; fields of view approximately 5.66 mm (left) and 2.83 mm (right).
It is known that in a small number of materials—some metals, calcite, and diamond—hollow channels may form at the intersection of twin lamellae, caused by deformation twinning. This was discovered by Gustav Rose (1868) in calcite, and thus the features are called “Rose channels” (figure 1). We believe that “boehmite needles” are in fact Rose channels. Even when very small, these channels would explain the optical relief observed, without a change in chemistry or infrared absorption. They fit the crystallographic nature of the structures observed.
Gemstones and Photoluminescence
Claudio C. Milisenda
DSEF German Gem Lab, Idar-Oberstein
Laser- and ultraviolet-excited luminescence spectroscopy and imaging are important techniques for gemstone testing, as they are among the most sensitive spectroscopic methods (see Hainschwang et al., 2013). They are able to identify optically active crystallographic defects such as vacancies and substitutions that are present in such small amounts that they cannot be detected by any other analytical method. Photoluminescence (PL) analysis became particularly important in the last decade for the separation of natural from synthetic diamonds and the detection of treatments. Today the availability of specially designed and reasonably priced portable equipment enables the rapid in situ identification of mounted and unmounted natural diamonds.
Although PL spectroscopy is most commonly used for diamond identification, it can also be applied to colored stones. Some stones exhibit unique luminescence patterns, which can be used to identify the material. Other examples are the separation of natural from synthetic spinel and the detection of heat-treated spinel. Since chromium is a typical PL-causing trace element, it is also possible to separate chromium-colored gems such as ruby and jadeite from their artificially colored counterparts. The color authenticity of specific types of corals and pearls can also be determined.
The rare earth elements (REE) are among the main substituting luminescence centers in Ca2+-bearing minerals (Gaft et al., 2005). Recently, REE photoluminescence has been observed in cuprian liddicoatite tourmalines from Mozambique (Milisenda and Müller, 2017). When excited by a 785 nm laser, the stones showed a series of bands at 861, 869, 878, 894, and 1053 nm, consistent with the PL spectra of other calcium-rich minerals (Chen and Stimets, 2014). LA-ICP-MS analysis confirmed the REE enrichment in this type of tourmaline compared to cuprian elbaites from Brazil and Nigeria. As a result, photoluminescence can be used as a further criterion for origin determination of Paraíba-type tourmalines.
We have extended our research on other calcium-rich gems, including various grossular garnet varieties such as hessonite and tsavorite (figure 1), uvarovite garnet, apatite, titanite, and scheelite, as well as a number of high-refractive-index glasses and color-change glasses, respectively.

Figure 1. 785 nm laser-induced REE photoluminescence spectra of tsavorite and hessonite garnets. Spectra are offset for clarity.
REFERENCES
Chen H., Stimets R.W. (2014) Fluorescence of trivalent neodymium in various materials excited by a 785 nm laser. American Mineralogist, Vol. 99, No. 2-3, pp. 332–342, https://doi.org/10.2138/am.2014.4311

Gaft M., Reisfeld R., Panczer G. (2005) Modern Luminescence Spectroscopy of Minerals and Materials. 2nd edition, Springer, Heidelberg, Germany, 606 pp.

Hainschwang T., Karampelas S., Fritsch E., Notari F. (2013) Luminescence spectroscopy and microscopy applied to study gem materials: a case study of C centre containing diamonds. Mineralogy and Petrology, Vol. 107, No. 3, pp. 393–413, https://doi.org/10.1007/s00710-013-0273-7

Milisenda C.C., Müller S. (2017) REE photoluminescence in Paraíba type tourmaline from Mozambique. 35th International Gemmological Conference, Windhoek, Namibia, pp. 71–73.
An Overview of Asteriated Gems: From Common Star Sapphire to Rare Star Aquamarine to One-of-a-Kind Star Zircon
Martin P. Steinbach
Steinbach–Gems with a Star, Idar-Oberstein, Germany
Rays of angel’s hair in a star-like shape, beams of light hovering over the surface of a gem—gems with stars have fascinated people of all cultures, continents, and religions since ancient times.
Asteriated gems have been known for more than 2,000 years, starting with Periegetes’ description of “Asterios” in the first century BCE. Other historical names were asteria, asterius, astrion, astrodamas, and astriotes. From Pliny the Elder (first century CE) to the Middle Ages, to De Boodt (1609) and Brueckmann (1783), asterism was known only in corundum and some feldspar varieties.

Figure 1. This 15.51 ct star rhodochrosite is from the Sweet Home mine in the state of Colorado. Photo by Martin P. Steinbach.
Currently, about 60 different gem varieties display asterism, whereas 15 gemstone varieties show a “trapiche” star. The well-known commercial examples include star ruby, sapphire, quartz, almandine garnet, moonstone (orthoclase feldspar), and the four-rayed black star diopside from India. Rare or less well-known varieties include star aquamarine, beryl, bronzite, calcite, chrysoberyl (A.G.S. Research Service, 1937), enstatite, hypersthene, kyanite, peridot, scheelite, scapolite, spinel, and sunstone (oligoclase feldspar). The extremely rare one-of-a-kind stars consist of star alexandrite, amazonite (Steinbach, 2016), cordierite, apatite, “star diamond,” ekanite, emerald (Liddicoat, 1977), kornerupine, kunzite, labradorite, opal, parisite, prehnite, rhodochrosite (figure 1), rhodonite, rutile, serandite, fibrolite (sillimanite), spessartine, taaffeite, tanzanite, topaz, tourmaline, and zircon.
Some of the 60 different star stones introduced in this colorful presentation can also show double stars; 12-, 18-, or 24-rayed stars; a network of stars; and trapiche varieties.
One new source of star rose quartz (China) and two new sources of almandine star garnet (China and Russia) will also be presented.
REFERENCES
A.G.S. Research Service (1937) Star chrysoberyl. G&G, Vol. 2, No. 8, p. 130.

Liddicoat R.T. (1977) Comments on the Hixon Collection. G&G, Vol. 15, No. 9, p. 1.

Steinbach M.P. (2016) Asterism—Gems with a Star. MPS Publishing and Media, Idar-Oberstein, Germany, 896 pp.
Quantitative Identification of Green Nephrite from Five Major Origins In Asia and North America
Zemin Luo, Andy H. Shen, and Meihua Chen
China University of Geosciences, Wuhan
Green nephrite (serpentine-related) has been generating substantial interest in the gem market. The primary sources are China, Russia, and Canada. Preliminary observations of mineral impurities and chemical components can help separate some dolomite-related nephrite from serpentine-related material. We have developed a novel classifier that can automatically identify the geological origin of random green nephrite samples on the market with 95% prediction accuracy. The technique behind this classifier is based on a trace-element database for green nephrite and a machine learning algorithm.

Figure 1. Representative green nephrite samples from the five serpentine-related deposits in Asia and North America: Manasi (A), Hetian (B), Taiwan (C), British Columbia (D), and Siberia (E).
The green nephrite database was built from 34 samples from five major geological origins (Manasi and Hetian in Xinjiang, China; Taiwan; British Columbia, Canada; and Siberia, Russia; representative samples are shown in figure 1). Trace-element information was collected by LA-ICP-MS with an average of six points on each sample. The following classification models were tested: neural network (multilayer perceptron), random forest, logistic regression, naive Bayes, and support vector machine. The random forest model gives the best performance on both training sets and cross-validation sets, with over 90% accuracy (table 1). The random forest model also identified the 10 most important trace elements for green nephrite classification as Sr, Ba, Zn, U, Ti, LREE, Cd, Rb, Mn, and K (figure 2). The geological information about this trace-element “fingerprint” needs further investigation.

Figure 2. The 10 most important trace elements for green nephrite classification, ranked in descending order, analyzed by the random forest algorithm.

We used linear discriminant analysis (LDA) to visually demonstrate the obvious separation of Siberian and Manasi green nephrites from the other origins (figure 3). This result is consistent with our optic and spectra characterization results. Green nephrite from the Manasi mine usually presents a heterogeneous grayish yellow green color, which is quite different from that of other origins. The absence of garnet inclusions in Siberian green nephrite—which distinguishes it from material from the other localities—can be confirmed by Raman spectroscopy. Samples from all origins have been characterized by photomicrography, micro-infrared spectra, and Raman spectra. We can therefore integrate the spectra and trace-element features into our classification model in the next step. We believe that the research method proved in this work is also applicable for other gemstones. It can also be a useful tool to study ancient green nephrite origins.

Figure 3. This scatter plot illustrates how an LDA algorithm was used to separate green nephrite. It shows clear separation of Manasi and Siberian nephrite from the other three origins (Hetian, British Columbia, and Taiwan), which show obvious overlap.
Radiocarbon Measurements on Pearls: Principles, Complexities, and Possibilities
Gregory Hodgins
University of Arizona Accelerator Mass Spectrometry Laboratory, Tucson
Radiocarbon dating is a method for determining the age of organic remains formed in the past 45,000 years. Also known as carbon-14 or 14C (figure 1), radiocarbon is a naturally occurring radioactive isotope of carbon with a half-life of 5,730 years. It is continuously formed in the earth’s upper atmosphere and makes its way into the biosphere via photosynthetic uptake and the food chain. Several radiocarbon dates for pearls have recently appeared in the scientific literature. Mollusks take up radiocarbon during life and incorporate it into shell and pearl carbonate. The aim of this presentation will be to describe the method, identification complexities, and challenges inherent in dating pearls based upon radiocarbon measurement so that we may plot a path for future research.

Figure 1. The author stands beside the terminus of the accelerator mass spectrometer radiocarbon beam line. Photo by Gretchen Gibbs.
There are two variants of the dating method. The first is conventional radiocarbon dating, which applies to organisms that lived before 1955 CE. The second involves the detection of anthropogenic radiocarbon in organisms living between 1955 CE and the present. There are biological, environmental, and experimental complexities in the radiocarbon dating of pearls, and the method will not work in all circumstances. However, some of these complexities—coupled with historic changes in when, where, and how pearls have been produced—mean radiocarbon measurement can provide information unavailable by other means.
Unconventional Techniques in Pearl Testing: Their Potential and Limitations
Chunhui Zhou
GIA, New York
Current routine pearl testing involves the application of various basic and advanced gemological techniques. These include the use of the gemological microscope, ultraviolet (UV) luminescence, microradiography, computed X-ray microtomography, optical X-ray luminescence, energy-dispersive X-ray fluorescence spectrometry (EDXRF), ultraviolet-visible (UV-Vis) spectroscopy, and Raman spectroscopy. While the majority of pearls may be identified using these existing conventional techniques, in certain cases identification challenges remain.

Figure 1. The application of unconventional pearl testing methods could be useful in separating difficult pearl samples, such as various types of freshwater pearls shown here. Photo by Diego Sanchez.
This talk will discuss the potential and limitations of various unconventional techniques that have been applied to pearl testing over recent years. Some of these techniques have been explored by GIA and resulted in meaningful benefits to the trade, and others referenced in the literature will also be briefly covered. Examples of these techniques include radiocarbon age dating, deoxyribonucleic acid (DNA) bar coding, in-depth trace-element geochemistry and isotope analysis, and 3D reconstruction of internal structures. It is important for gemological and research institutions to continue developing novel techniques for pearl testing in order to achieve the accurate separation between natural and cultured pearls, principally non-bead cultured, as well as other aspects of identification that might assist in reaching this accurate analysis (e.g., species determination, geographical origin determination, and treatment identification). Despite decades of pearl testing experience, some challenges remain within laboratories, and the application of additional unconventional methods could resolve some of these issues.
ADDITIONAL READING
Krzemnicki M.S., Hajdas I. (2013) Age determination of pearls: A new approach for pearl testing and identification. Radiocarbon, Vol. 55, No. 3, pp. 1801–1809, http://dx.doi.org/10.1017/S0033822200048700

Meyer J.B., Cartier L.E., Pinto-Figueroa E.A., Krzemnicki M.S., Hänni H.A., McDonald B.A. (2013) DNA fingerprinting of pearls to determine their origins. PLOS One, Vol. 8, No. 10, pp. 1–11, http://dx.doi.org/10.1371/journal.pone.0075606

Saruwatari K., Suzuki M., Zhou C., Kessrapong P., Sturman N. (2018) DNA techniques applied to the identification of Pinctada fucata pearls from Uwajima, Ehime Prefecture, Japan. G&G, Vol. 54, No. 1, pp. 40–50, http://dx.doi.org/10.5741/GEMS.54.1.40

Zhou C., Hodgins G., Lange T., Saruwatari K., Sturman N., Kiefert L., Schollenbruch K. (2017) Saltwater pearls from the pre- to early Columbian era: A gemological and radiocarbon dating study. G&G, Vol. 53, No. 3, pp. 286–295, http://dx.doi.org/10.5741/GEMS.53.3.286
What Is Cobalt Spinel? Unraveling the Causes of Color in Blue Spinels
Aaron C. Palke and Ziyin Sun
GIA, Carlsbad, California
Cobalt is known to produce vibrant blue color in both natural and synthetic spinel. In the 1980s and ’90s, Vietnam started producing blue spinel with very high concentrations of cobalt and bright, saturated color rivaling that seen in synthetic material. Iron can also cause blue coloration in spinel, although this is typically a duller grayish or greenish blue. So when is a blue spinel worthy of carrying the “cobalt spinel” moniker? With high-sensitivity analytical methods such as LA-ICP-MS, cobalt can be detected in most spinel, even at the sub-ppm level. But sub-ppm concentrations of cobalt do not impact the color of a faceted spinel. In addition, the saturation and quality of blue color will depend on the concentration of iron and its valence state (e.g., Fe2+ vs. Fe3+).
In this contribution we will explore the color space of blue spinel and outline the various contributions to their coloration. Using UV-Vis spectrometry and LA-ICP-MS on blue spinel from Vietnam, Sri Lanka, Madagascar, and Tanzania, we have isolated three unique and consistent chromophores (see figure 1). Cobalt in its divalent form (Co2+) has multiple absorption bands between ~510 and 660 nm and produces a bright blue color. Two broad absorption bands at ~650 and 920 nm are related to Fe2+ substituting for Al3+ in octahedral coordination. Finally, another set of at least three absorption bands occurs at ~500–620 nm and overlaps those from Co2+. Comparison with other Fe-related absorption bands and consideration of the crystal chemistry of spinel suggest that these bands may be related to Fe3+ in the tetrahedral site in the spinel structure. This last absorption feature creates a grayish pink coloration, and in combination with Co2+ it can be responsible for blue to violet color change in some spinel. There is clearly a significant interplay between these three chromophores, and a full understanding of the causes of color in blue spinel can only be attained by consideration of all three contributions.

Figure 1. UV-Vis spectra of the individual contributions from three chromophores in blue spinel, octahedral ferrous iron (VIFe2+), octahedral cobalt (VICo2+), and tetrahedral ferric iron (IVFe3+). At the top is the full spectrum of a blue spinel from Tanzania, followed by the sum of the three individual components (SUM). UV-Vis spectra of all blue spinels in this study could be recreated with varying contributions from the three spectra at the bottom. @topic:1


Publish Year: 2018 Title: Colored Stones and Pearls Abstract: Figure 1. 3D reconstructions of the internal structures of two bead-cultured pearls with atypical nuclei. Left: A flower-shaped bead nucleus. Right: A small gastropod shell used as a nucleus.
3D Reconstruction of the Internal Structures of Pearls
Emiko Yazawa and Chunhui Zhou
GIA, New York
Pearl testing involves a variety of tools and techniques, most notably X-ray imaging. GIA applies both real-time X-ray microradiography (RTX) and computed X-ray microtomography (μ-CT) to reveal the internal structures of pearls and draw conclusions on their identity. These images help gemologists determine whether a pearl is natural, bead-cultured, non-bead cultured (NBC), and so forth. The identification of some pearls remains challenging for even the most well-equipped laboratories. Researchers sometimes find surprises hidden within—a piece of shell or some other interesting object that is difficult to visualize with two-dimensional images.
Here, we present a range of interesting internal three-dimensional structures (figure 1), using specialized software and μ-CT slice images for the reconstruction. These include unusual internal growth features such as bivalve and gastropod shells, foraminifera, flower-shaped bead nuclei, and plastic bead nuclei, as well as non-bead-cultured features such as voids and linear structures. This powerful research tool makes it possible to virtually explore, manipulate, extract, and reconstruct specific areas inside a pearl for analysis. It also gives the operator the ability to enhance the existing μ-CT data to view the details more clearly, thus revealing the fascinating world within pearls that gemologists routinely encounter.
Atypical “Bead”-Cultured Pinctada Maxima Pearls Nucleated with Freshwater Non-Bead-Cultured Pearls
Promlikit Kessrapong and Kwanreun Lawanwong
GIA, Bangkok
At present, most of the freshwater shell bead nuclei used in the cultured pearl industry originate from mussels from the Mississippi River in the United States. However, shell beads are not the only material used as nuclei in the culturing process. Cultured freshwater pearls have also been used as nuclei to produce atypical bead-cultured (aBC) South Sea pearls (Scarratt et al., 2017).
GIA researchers sourced several aBC samples from Orient Pearl Ltd. in Bangkok. Two samples were selected, one “golden” and one white (figure 1), both showing an unmistakable saltwater appearance. Standard testing methods as well as macro photography, microradiography, X-ray luminescence (Hänni et al., 2005; Kessrapong et al., 2017), Raman and photoluminescence (PL) spectroscopy and ultraviolet-visible spectrophotometry (UV-Vis) were applied to the samples prior to cutting them in half. After they were sawn, further data was collected through photomicrography, X-ray fluorescence (XRF) images, and laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) analysis.

Figure 1. Photographs of the “golden” (left) and white (right) atypical bead-cultured pearls. Photos by Kwanreun Lawanwong.
As expected, the results of the examination confirmed their aBC nature. While their appearance, baroque shapes, and white to strong yellow (golden) colors indicated they were typical saltwater Pinctada maxima pearls, their internal structures revealed clear boundaries where the outlines of freshwater NBC pearl nuclei could be seen in the microradiographs. Raman, PL, and UV-Vis spectra for the golden sample indicated it formed within a P. maxima mollusk. Also, in keeping with their freshwater NBC nuclei structure, a weak to moderate fluorescence was observed, which would not be the case to such a degree if they were entirely saltwater in origin. The golden pearl showed a yellow-orange fluorescence to X-ray luminescence, while the white sample exhibited a yellow-green reaction, similar to the result one would expect to see in cultured saltwater pearls incorporating freshwater mussel shell nuclei.
Examining the halves, we observed more detail: the demarcation between the two parts (nuclei and surrounding nacre overgrowth), small void/linear features (proving the NBC origin of the nuclei), the different colors/structures between the saltwater and freshwater nacre components, and some other indications of their cultured origin (i.e., small voids within the demarcation zones). The X-ray luminescence reactions were similar to those seen in the whole samples, only more intense since the inner freshwater nuclei were now directly exposed to the X-rays and not masked by the saltwater nacre that covered them prior to cutting. LA-ICP-MS analysis clearly revealed the nature of the outer saltwater layers and inner freshwater pearls, through significant differences in the concentrations of Sr and Mn among other elements. The Mn levels in the center were higher while the Sr levels were lower compared to the overgrowth layers, where the opposite was true, as expected in saltwater material.
Although cutting the pearls in half was a nice way to reveal the features in more detail, it is worth noting that gemologists do not need to go to such extremes to prove the identities of such pearls in laboratory conditions. Standard testing methods permit the straightforward identification of aBC pearls. Cutting them in half is a useful exercise to carry out for scientific examination of their structures and to allow more detailed analysis that would not otherwise be possible.
REFERENCES
Hänni H.A., Kiefert L., Giese P. (2005) X-ray luminescence, a valuable test in pearl identification. Journal of Gemmology, Vol. 29, No. 5/6, pp. 325–329.

Kessrapong P., Lawanwong K., Sturman N. (2017) Pinctada maculata (pipi) bead-cultured blister pearls attached to their shells. GIA Research & News, Apr. 25, https://www.gia.edu/gia-news-research/pinctada-maculata-bead-cultured-blister-pearls-shells

Scarratt K., Sturman N., Tawfeeq A., Bracher P., Bracher M., Homkrajae A., Manustrong A., Somsa-ard N., Zhou C. (2017) Atypical “beading” in the production of cultured pearls from Australian Pinctada maxima. GIA Research & News, Feb. 13,  https://www.gia.edu/gia-news-research/atypical-beading-production-cultured-pearls-australian-pinctada-maxima
Chinese Freshwater Cultured Pearl Industry at a Crossroads
Qishen Zhou and Ren Lu
Gemmological Institute, China University of Geosciences, Wuhan
During the past 15 years, China has made tremendous progress in the quality and output of freshwater cultured pearls (see figure 1). Innovative technologies have facilitated a variety of colors and high-quality nacre within a shorter culturing cycle. Large-scale culturing has boosted the annual output to a high of 2,200 tons, and China has become an undisputed freshwater pearl empire.

Figure 1. Tea set decorated with Chinese freshwater pearls from the 2016 G20 Summit held in Hangzhou, China. Courtesy of Angeperle Corp.
However, the expanded production has been accompanied by considerable damage to the environment. With a more forceful implementation of the Chinese government’s environmental policy, there have been many strict bans in the main producing areas of freshwater cultured pearls during the past three years. The pearl culturing area decreased from approximately 250 km2 in 2005 to 100 km2 in 2016, and output has also dropped from a peak annual output of over 2,200 tons to less than 1,300 tons in 2017. Production is predicted to decline by about 50 percent in the next year or two.
The number of Chinese lakes with Grade IV–V water quality (Grade IV water is used in general industrial and recreational water areas and Grade V water is employed in agricultural and general landscape water areas; see New York Water Quality Standards, 2016) increased from 16.67% in 2000 to 58.5% in 2016. It is worth emphasizing that about 20% of all lakes are still Grade V. At the same time, water eutrophication has become a common phenomenon. It is caused by the discharge of excess nutrients (mainly nitrogen and phosphorus), resulting in abnormal reproduction and growth of various aquatic organisms and plants. Since 2003, the proportion of eutrophic lakes and reservoirs in China has increased from 50% to an average of 77.93%, while the proportion of eutrophic reservoirs alone has nearly doubled from 15.05% to 28.8%. Among the lakes monitored by the government in 2013 and 2015, many of the eutrophic lakes are also leading areas for pearl culturing.
As a result of the Chinese government’s strict environmental regulations, the extensive feeding model with massive fertilization is no longer permitted. The government has carried out the forced demolitions of some pearl culturing areas during the past three years, and the three largest freshwater pearl-culturing provinces/regions also have implemented strict bans on cultured pearls. Meanwhile, the central and eastern provinces such as Hubei and Zhejiang began compulsory demolition of freshwater pearl culturing in 2017, which caused a dramatic decline in pearl output.
This has been a major setback for freshwater pearl farmers, aquaculture companies, and pearl workers. The Chinese government at all levels has subsidized the farmers who have suffered from demolition, though most are still reported to have suffered serious losses because of culturing bans.
At the same time, the new environmentally friendly and standardized aquaculture models will usher in a new era for Chinese freshwater cultured pearls. The Chinese Academy of Agricultural Sciences and various enterprises have developed many new culturing methods. For example, fish-clam mixed cultivation has been shown to improve water quality and increase output value, and the three-part aquaculture model of fish, clam, and poultry can balance ecological concerns and generate considerable income. Environmentally friendly aquaculture will become the new standard for freshwater cultured pearls, and it will take about 5 to 10 years to adopt automated aquaculture technology across mainland China.
To summarize, wholesale and retail prices of Chinese freshwater pearls will fluctuate significantly in the next two to five years based on the freshwater pearl culturing cycle. China’s freshwater cultured pearl industry has formed a complete and relatively mature supply chain over the past decade. It is still facing new challenges, new development opportunities, and critical decisions for a sustainable industry under the government’s new policy and the promotion of new aquaculture technologies. At the same time, the increasing demand for high-quality freshwater cultured pearls in China and around the world is prompting the upgrade and transformation of the product.
REFERENCES
Akamatsu S., Li T.Z., Moses T.M., Scarratt K. (2001) The current status of Chinese freshwater cultured pearls. G&G, Vol. 37, No. 2, pp. 96–113, http://dx.doi.org/10.5741/GEMS.37.2.96

New York Water Quality Standards (2016) https://www.epa.gov/sites/pro-duction/files/2014-12/documents/nywqs-section1.pdf
Comparison of Laser Ablation and Solution ICP-MS Analyses of Emeralds
Ruan Hattingh1, Raquel Alonso-Perez2, Aaron C. Palke3, Lee Groat4, and James M.D. Day1 (presenter)
1Scripps Institution of Oceanography, La Jolla, California
2Harvard University, Cambridge, Massachusetts
3GIA, Carlsbad, California
4University of British Columbia, Vancouver, Canada
Geochemical studies of emeralds can confirm their provenance and improve our understanding of deposit origin. LA-ICP-MS is a minimally destructive and relatively high-throughput technique that allows determination of more than 30 major, minor, and trace elements simultaneously using small spot sizes (20–100 μm). A reliable and consistent LA-ICP-MS protocol requires good standardization, including the use of matrix-matched standard reference materials. Here we provide a robust assessment of the quality of LA-ICP-MS analysis of emeralds, utilizing a set of natural and synthetic gem-quality emeralds housed within the Mineralogical & Geological Museum at Harvard University. Our goals were to identify large emeralds as potential standard reference materials and to examine the robustness of certain trace elements in emeralds for provenance and for petrogenetic models of their origin.

Figure 1. Comparison of selected trace-element abundances in emeralds measured using both solution- and laser-ablation ICP-MS.
In this study, we have analyzed more than 45 emeralds using both LA-ICP-MS and solution ICP-MS techniques. For solution ICP-MS, between 5 and 10 mg of individual emeralds was digested in HF-HNO3 prior to analysis of Be by standard addition and all other elements by comparisons with standard reference materials spanning a range of major-, minor-, and trace-element compositions (see also the oral presentation by R. Alonso-Perez from this conference). Some emeralds that we analyzed contained small inclusions, but the majority were inclusion-free. For comparison, portions of the same emeralds were also measured by LA-ICP-MS using 100 μm spot sizes on a New Wave Research UP213 (213 nm) laser ablation (LA) system coupled to a ThermoScientific iCAPq ICP-MS. In general, we found excellent agreement for major-, minor-, and trace-element data between the solution ICP-MS and LA-ICP-MS techniques (figure 1), finding reliable results by LA-ICP-MS for Li, Be, Na, Mg, Al, Si, K, Sc, Ti, V, Cr, Fe, Ni, Zn, Ga, Rb, Cs, and Pb. Less reliable results were generated for Sr and the rare earth elements, due to the generally low abundances of these elements in emeralds. During this study, we identified natural emeralds as potential standard reference materials for future inter-laboratory LA-ICP-MS comparison, as well as a synthetic emerald (Harvard ID 109678) that is enriched in the key elements outlined above and in Mo.
Fluid Effervescence: A New Process for Natural Color Variation In Gems
Dan Marshall
Simon Fraser University, Burnaby, British Columbia, Canada
The emeralds from the Emmaville-Torrington deposit in Australia are commonly zoned (figure 1) and display alternating bands of emerald green and colorless growth zones within individual crystals at the millimeter scale. The zoning is seen optically but can be observed via imaging techniques such as backscattered electron and cathodoluminescence, and detected chemically via electron microprobe analyses. Additionally, there is a correlation between the presence of a population of primary vapor-rich fluid inclusions within the clear growth zones (figure 2) and a second population of highly saline three-phase (liquid + vapor + halite) fluid inclusions in the darker or colored growth zones.

Figure 1. Internal features of a zoned emerald crystal from the Emmaville-Torrington deposit. Photomicrograph by Dan Marshall.

Figure 2. Enlarged area of the photomicrograph of the primary fluid inclusions from figure 1 showing alternating colored and clear areas in the zoned emerald crystal. The clear zones correspond to growth zones dominated by primary vapor-rich fluid inclusions. The field of view is approximately 650 microns. Photomicrograph by Dan Marshall.
The two fluid inclusion populations appear to represent conjugate sets of a boiling or effervescent system, with the three-phase fluid inclusions having an average salinity of approximately 33 wt.% NaCl equivalent. This population undergoes total homogenization into the liquid and probably represents fluids trapped in the liquid system of a two-phase (effervescent) system. The vapor-rich population of fluid inclusions (again, see figure 2) have an average salinity of approximately 6 wt.% NaCl equivalent and homogenize into the vapor phase at higher temperatures.
The correlation of color versus clear growth zones—corresponding to high-salinity liquid-dominant and vapor-dominant low-salinity primary fluid inclusions, respectively—indicates that the color banding within the Emmaville-Torrington emerald is related to emerald precipitation in the liquid or vapor portion of an effervescing fluid system. Other emerald deposits worldwide display similar growth banding, as do some other deposits of gem topaz and gem varieties of quartz.
The Heat Treatment of Basalt-Related Blue Sapphires
Wasura Soonthorntantikul, Ungkhana Atikarnsakul, Charuwan Khowpong, and Sudarat Saeseaw
GIA, Bangkok
Heat treatment is the most common method used to improve the color and/or clarity of corundum. Basalt-related blue sapphires typically have an unattractive dark blue color due to their high iron content, and low-temperature heat treatment can be applied to lighten this material (Nassau, 1981; Hughes et al., 2017). The main factors that influence the changes in corundum are the temperatures employed, the conditions in which they are heated, and the duration of the treatment process. However, it is difficult to distinguish between naturally heated and heat-treated blue sapphires from basalt-related deposits using only standard gemological testing and microscopic examination. In this study, basalt-related blue sapphires from various locations (Thailand, Cambodia, Australia, and Nigeria) were heat treated at low temperatures, ranging from 700 to 1050°C, for durations of 1.75, 7, and 28 hours in air (oxidizing atmosphere). The changes in color appearance, UV fluorescence, internal features, and spectroscopic properties were investigated.

Figure 1. Color-calibrated photos of basalt-related blue sapphires before (top) and after heating at 1050°C for 28 hours (bottom). Photos by Sasithorn Engniwat.
The results indicated a negligible change or a slight lightening of the blue color after treatment at 700°C, while an obvious lightening of the blue color resulted from heating at 900°C and 1050°C (figure 1). Some solid inclusions, iron stains, and partially healed fractures showed signs of alteration during the heating experiments, while needles and minute particles did not show any signs of change. Unheated samples were inert to short-wave ultraviolet (UV) radiation. After heating, most basalt-related blue sapphires remained inert under short-wave UV, but a few samples exhibited a very weak chalky green fluorescence. Fourier-transform infrared (FTIR) spectra obtained from the samples varied considerably, with differences between the peak intensities recorded before each heat treatment process and also after each unique temperature and time treatment combination. In most cases, unheated blue sapphires from basalt-related deposits revealed the characteristic 3309 cm–1 series of peaks in the FTIR spectrum (the intensity of 3232 cm–1 being much lower than that of 3309 cm–1). After heating at 700°C and 900°C, the intensity of the 3309 cm–1 peak decreased and the 3232 cm–1 peak increased, respectively. However, some samples that initially showed a relatively intense 3232 cm–1 peak in the series before treatment exhibited a more intense 3309 cm–1 peak and a less intense 3232 cm–1 peak post-treatment. After heating at 1050°C for 1.75 hours, we recorded a decrease in the intensity of the 3309 cm–1 peak and an increase in the 3232 cm–1 peak, to the point where they were of almost comparable intensity. When subsequently heated for 7 and 28 hours, the intensity of 3309 cm–1 peak increased and that of the 3232 cm–1 peak decreased (figure 2). The ultraviolet/visible/near-infrared (UV-Vis-NIR) spectra obtained from the samples heated at 900°C and 1050°C for 1.75, 7, and 28 hours showed a reduction in the height/intensity of the broad band centered at 580 nm related to an Fe2+-Ti4+ intervalence charge transfer. This reduction is the root cause of the lighter color after heat treatment.

Figure 2. FTIR spectra of the sample before and after heating at 1050°C for up to 28 hours.
The results of this study show that even with advanced data, it is very challenging to separate basalt-related stones that have been heated from those that have not undergone any post-mining heat treatment, owing to the variable results associated with the experimental temperatures and durations used. Inclusion studies may provide sufficient evidence in some cases, but even when comparing the inclusions scene before and after treatment, separation often remains challenging.
REFERENCES
Hughes R.W., Manorotkul W., Hughes E.B. (2017) Ruby & Sapphire: A Gemologist’s Guide. RWH Publishing/Lotus Publishing, Bangkok, pp. 146–148, 200–201.

Nassau K. (1981) Heat treating ruby and sapphire: Technical aspects. G&G, Vol. 17, No. 3, pp. 121–131, http://dx.doi.org/10.5741/GEMS.17.3.121
“Low-Temperature” Heat Treatment of Mozambican Ruby
Sudarat Saeseaw, Charuwan Khowpong, and Ungkhana Atikarnsakul
GIA, Bangkok
Mozambique is one of the most important sources of ruby today, with the Montepuez mine producing material ranging from light to dark purplish red. To improve their color, Montepuez rubies are heated at low temperatures to remove the purplish component—caused by blue color zoning—and create a more attractive and desirable red color. For this study, 47 samples were selected for heat treatment in air (oxidizing environment) at different temperatures and varying durations. The samples were heated to 600, 700, 800, and 900°C for 2 hours and 40 minutes, 8 hours, or 24 hours. The results showed no significant change to the blue color zoning when heated to 600 or 700°C over any of the time frames chosen; however, the blue component was reduced when heated to a minimum of 800°C for 2 hours and 40 minutes (figure 1).

Figure 1. Color-calibrated photos of a Montepuez ruby before (left) and after (right) heat treatment at 800°C for 8 hours. The stone’s blue color component clearly decreased after heating. Photos by Sasithorn Engniwat.
Observing any changes to inclusions can be challenging when examining material subjected to lower-temperature heating, since there is less chance inclusions will be affected (Pardieu, 2015). Inclusions in Mozambican rubies are limited to needles, platelets, and other fine particles. When any alteration takes place, the evidence is very subtle. During treatment, spots can form on these platelets (figure 2), although this is not always the case. When crystalline inclusions are present, it is easier to identify heat treatment because fractures often develop around them, especially in larger crystals. Some gems contain fractures with associated iron staining or fingerprints, and their appearance may change drastically during treatment (Sripoonjan, 2016). Inclusion studies are not always conclusive, however, and advanced techniques such as FTIR spectroscopy are needed to assist in detecting low-temperature heat treatment. The presence of the 3309, 3232, and/or 3185 cm–1 peak(s) appears related to heat treatment, since they were only observed in heated stones.

Figure 2. Mozambican ruby with spotted platelets that indicate heat treatment. Brightfield and fiber-optic illumination. Photo by Charuwan Khowpong; field of view 1.0 mm.
REFERENCES
Pardieu V., Saeseaw S., Detroyat S., Raynaud V., Sangsawong S., Bhusrisom T., Engniwat S., Muyal J. (2015) GIA lab reports on low-temperature heat treatment of Mozambique ruby. GIA Research News, Apr. 28, https://www.gia.edu/gia-news-research-low-temperature-heat-treatment-mozambique-ruby

Sripoonjan T., Wanthanachaisaeng B., Leelawatanasuk T. (2016) Phase transformation of epigenetic iron staining: indication of low-temperature heat treatment in Mozambique ruby. Journal of Gemmology, Vol. 35, No. 2, pp. 156–161.
Pearl Classification: GIA’s Approach
Joyce Wing Yan Ho and Sally Chan Shih
GIA, New York
Pearls form in a wide variety of sizes, shapes, and colors. As a result, they are among the most popular materials in the jewelry industry. Their unique appearance and the affordability of many types of cultured pearls on the market have allowed them to gain a greater audience. Throughout the ages, pearls have been associated with class, grace, and beauty by many cultures. Such a diverse range of pearl types has meant that a way of grading or classifying them was required, and as a consequence, a number of different grading systems have been developed. The differences make the comparison of grades between systems difficult to align, and agreeing on a universal grading system has remained one of the many challenges facing the pearl industry.

Figure 1. Color is one of GIA’s 7 Pearl Value Factors. This hue circle depicts generalized color distribution by pearl type.
GIA created the “7 Pearl Value Factors” (figure 1) for the same reason it developed the 4Cs of diamond quality: to establish a standard terminology for describing quality using language everyone can understand. Each value factor is important in determining a pearl’s overall quality. This poster reviews each value factor, starting with size and then looking at shape, color, luster, surface, nacre quality, and matching. GIA has developed a modernized color scale for all types of pearls (saltwater and freshwater) and physical master sets to ensure a pearl is graded with a degree of consistency. Every GIA laboratory worldwide uses the same grading system to produce consistent results. Adopting GIA’s standard pearl classification terminology throughout the gem and jewelry industry would foster improved communication within the trade and, by default, bridge the communication gap between buyers and sellers through easily understandable terminology.
A Pearl Identification Challenge
Nicholas Sturman1, Laura M. Otter2,4, Artitaya Homkrajae3, Areeya Manustrong1, Nanthaporn Nilpetploy1, Kwanreun Lawanwong1, Promlikit Kessrapong1, Klaus Peter Jochum4, Brigitte Stoll4, Herman Götz5, and Dorrit E. Jacob2
1GIA, Bangkok
2Macquarie University Department of Earth and Planetary Sciences, Sydney
3GIA, Carlsbad, California
4Max Planck Institute for Chemistry, Mainz, Germany
5Johannes Gutenberg University, Mainz, Germany
Pearl testing in laboratory conditions usually follows a set routine. The pearls are examined to obtain a preliminary idea of their type and identification, and then a series of steps (e.g., trace-element geochemical analysis, optical X-ray luminescence, microradiography, and X-ray computed microtomography) are undertaken to confirm the initial examination. With experienced gemologists it is possible, in many cases, to reach the same conclusion that was arrived at after the initial examination. However, all experienced gemologists have encountered situations—whether handling pearls or other gems—where the final result does not match the initial opinion.
This poster illustrates the trace-element characteristics of pearls in general, but focuses on two nacreous pearl samples in particular that revealed “atypical” properties not encountered in any pearls tested previously by GIA gemologists. On initial examination, the pearls did not show clear indications of being either freshwater or saltwater. Nor was it clear whether they were likely to be natural or cultured. In most cases, these two questions would be resolved very quickly after some of the initial examination procedures were completed. This was not the case with these two examples, however, since the energy-dispersive X-ray fluorescence (EDXRF) results conflicted with the optical X-ray luminescence observations. This led to additional LA-ICP-MS analysis, a procedure not often required in routine pearl testing. The situation appeared even more perplexing after RTX work revealed inconclusive structures, which led to additional analysis using μ-CT. The pearls were so unusual in a number of ways, especially with regard to their trace-element chemistry, that we decided to seek a second opinion on this aspect in particular. Hence, the pearls were sent to the Max Planck Institute for Chemistry (MPIC) in Mainz, Germany.
The results of the work by GIA and MPIC showed that the pearls consisted of layer-like zones with distinct trace-element signatures associated with both saltwater and freshwater environments, as confirmed by the spot analysis undertaken by three different LA-ICP-MS units in three different locations operated by three different groups of scientists. While the pearls were in Germany, the opportunity was also taken to perform μ-CT analysis on both samples. The results were in keeping with those obtained by GIA, though the interpretation of the structures was not straightforward and together with the trace-element chemistry led to various questions about the producing mollusk and the origin/type.
In summary, the pearls were found to be a mixture of saltwater and freshwater layers. While the pearls are likely non-bead cultured, their true identity remains a puzzle owing to their complex chemistry and questions raised concerning the producing mollusks. To our knowledge, these pearls with mixed trace-element patterns are the first of their type recorded in the literature.
The Study of Tanzanite’s Gemological and Color Characteristics
Jinding Yu and Ren Lu
Gemmological Institute, China University of Geosciences, Wuhan
Tanzanite was discovered in the Merelani Hills in the Arusha region of northeastern Tanzania during the 1960s. It first became popular with a promotional campaign by Tiffany & Co. in the late 1960s. The fact that there is only one deposit in the world further raised its value. Never before had a newly discovered gemstone gained so much success within such a short time.
Natural, unheated blue tanzanite is rare and known for its trichroic colors: bluish violet, violetish blue, and yellow-green. To best realize the hidden beauty, natural tanzanite, often showing a brown hue, is heated to achieve a predominantly blue coloration before reaching the market. It has been previously reported that heated tanzanite will convert from trichroic to dichroic, but there have been few details and virtually no quantitative UV-Vis absorption coefficient data to support that claim.
Tanzanite exhibits metachromatism, a color change, when illuminated by cold and warm light sources. In addition, tanzanite also exhibits the Usambara effect. The only form of zoisite to have its Usambara effect studied until now was epidote. If these two color phenomena are also recognized, it will raise tanzanite’s status and value.
For this study we chose several brown zoisites, a violet tanzanite, a pink zoisite and a green zoisite from Merelani, and a green zoisite from Afghanistan. We conducted a systematic and quantitative analysis of the tanzanite sample using XRF and LA-ICP-MS, as well as FTIR, Raman, and UV-Vis spectroscopy. We attempted to quantitatively analyze the tanzanite’s color before and after heating.
The results showed that tanzanite changed from trichroic to nearly—but not completely—dichroic after heating. The difference between these two types of blue was eye visible but also indicated by the spectrum and the photos. The study revealed tanzanite’s color-change quantitative data and the method for taking photos of its color-change effect. We also found that the brown zoisite displayed the Usambara effect. Lastly, we concluded that the tanzanite’s blue level is probably related to vanadium.

Figure 1. Colorimetric parameters for three axes of an unheated and a heated tanzanite sample are shown in CIELAB color space under standard A illuminant (left) and standard D65 illuminant (right). See Liu et al. (1999), Schmetzer et al. (2009), and Sun et al. (2015).
REFERENCES
Liu Y., Shigley J.E., Halvorsen A. (1999) Colour hue change of a gem tourmaline from the Umba Valley, Tanzania. Journal of Gemmology, Vol. 26, No. 6, pp. 386–396.

Schmetzer K., Bernhardt H.-J., Bosshart G., Hainschwang T. (2009) Colour-change garnets from Madagascar: Variation of chemical, spectroscopic and colorimetric properties. Journal of Gemmology, Vol. 31, No. 5-8, pp. 235–282.

Sun Z., Palke A.C., Renfro N. (2015) Vanadium- and chromium-bearing pink pyrope garnet: Characterization and quantitative colorimetric analysis. G&G, Vol. 51, No. 4, pp. 348–369, http://dx.doi.org/10.5741/GEMS.51.4.348 @topic:5


Publish Year: 2018 Title: Exhibition Review: Ornamental Traditions: Jewelry from Bukhara Abstract: Figure 1. Paisley earrings ca. 1885. Gilt silver with cloisonné enamel. Promised gift of Barbara and David Kipper. Photo courtesy of the Art Institute of Chicago.

The Uzbek city of Bukhara, the last capital of the Emirate of Bukhara (1785–1920), was designated a UNESCO World Heritage site in 1993. Situated along the famous transcontinental Silk Road, the city is known for its architecture, particularly the blue glazed tiles and complementary blue enamelwork that grace its buildings. This same blue ornamentation is worked into the jewelry from this period of Bukhara’s history. The large pieces that characterize the jewelry of the emirate, stunning in their elaborate ornamentation, are rarely seen outside the former Soviet republics. Through promised gifts from the private collection of Barbara Levy Kipper and her late husband, David, the Art Institute of Chicago is able to display almost 50 such pieces in Ornamental Traditions: Jewelry from Bukhara. Enameling is used in a number of objects—such as the paisley earrings in figure 1—to represent Bukhara’s famous blue detailing with great success, while other pieces use turquoise and glass stones (figure 2) to create a similar effect.

Figure 2. Pair of armbands, ca. late nineteenth century. Silver inlaid with turquoise and glass stones. Promised gifts of Barbara and David Kipper. Photos courtesy of the Art Institute of Chicago.
In Bukharan culture, large jewelry pieces were normally designed as sets and intended to serve multiple purposes. For instance, the pieces of one suite might be intended to ward off evil spirits while simultaneously indicating political status and religious affiliation. There is no shortage of objects devoted to religious observation; one, a Quran carrying case dating from the late nineteenth century (figure 3), includes a strap for portability. The entire piece is made of gilt silver, cloisonné enamel, and leather. A set of pendants feature turquoise, coral, and glass stones inlaid in silver. Silver (both pure and gilded) is the primary metal in the pieces on display. This is understandable given the weight of large belts and elaborately decorated headdresses, such as one ceremonial piece featuring ruby, coral, and glass. Gold is occasionally seen in objects from the late nineteenth century, such as a pair of earrings designed in the Gujarati akota style. Decorative objects such as a twentieth-century pen case (figure 4) and an enameled box dating to 1883 (figure 5) are no less fantastic in their attention to detail and functionality.

Figure 3. Quran carrying case ca. 1890–91. Gilt silver with cloisonné enamel and leather. Promised gift of Barbara and David Kipper. Photo courtesy of the Art Institute of Chicago

Figure 4. Pen case ca. 1912, inscribed “A.H. 1330.” Gilt silver with cloisonné enamel. Promised gifts of Barbara and David Kipper. Photos courtesy of the Art Institute of Chicago.
Juxtaposed alongside Central Asian textiles—some created using the elaborate ikat resist dyeing technique—from the Art Institute’s permanent collection, Ornamental Treasures is a small but powerful view into a bygone world rarely seen by Westerners.

Figure 5. Enameled box ca. 1883. Silver with cloisonné enamel. Promised gifts of Barbara and David Kipper. Photos courtesy of the Art Institute of Chicago.
Ornamental Traditions: Jewelry from Bukhara is on view in Gallery 50 of the Islamic Art section of the Art Institute of Chicago until June 30, 2019. Admission is $20.00 for Chicago residents, $22.00 for Illinois residents, and $25.00 for visitors from out of state. Senior and student pricing begins at $14.00. Children 17 and under qualify for free admission. The Art Institute of Chicago is open daily from 10:30 a.m. to 5:00 p.m. and Thursdays until 8:00 p.m. @topic:6


Publish Year: 2015 Title: Books: Bright Lights in the Dark Ages: The Thaw Collection of Early Medieval Ornaments Abstract: By Noël Adams, hardcover, 432 pp., illus., publ. by The Morgan Library & Museum, New York, 2014, US$95.00.

Bright Lights in the Dark Ages is the seventh volume in which the Morgan Library and Museum documents a segment of the Eugene Thaw collection. Thaw’s many collections have been assembled over a lifetime, and he is considered the museum’s greatest benefactor since J.P. “Pierpont” Morgan himself. Art collector and dealer Eugene Thaw began acquiring ornaments from the early medieval period in the 1980s, leading to a systematic effort in 2001 to bridge the gap between the Museum’s ancient collections and its late medieval holdings. Thaw’s choices were based on aesthetic rather than scholarly merit, and he was advised on his acquisitions by the author of this book.

	This volume focuses on small personal ornaments (brooches, buckles, and pendants), from Western Europe, including the United Kingdom and Scandinavia, to the Black Sea, that were fabricated in the early Middle Ages, often referred to as the “Dark Ages.” These small objects, often found interred with their owner in gravesites, are considered “portable wealth” and are usually interpreted by historians and archeologists as emblems of power and status.

	The book’s narrow focus allows the author to address two objectives. The first is to challenge the preconceptions of art and culture of the “Dark Ages,” and the pejorative use of that term to describe a time that was actually quite culturally dynamic. The second is to demonstrate the continuity and evolution of metalworking from the 2nd century to the 10th century AD. To provide helpful context, the introductory sections outline the declining Roman Empire, the migration and invasion of new peoples and tribes from the East and the North, and the contraction of the Byzantine Empire.

	The term “Dark Ages” refers to the death of classical literature in the sense that pagan tribes, specifically Germanic and Slavic “barbarians,” had rich oral traditions that eclipsed the written word following the disintegration of the Roman Empire. Other scholars of the 14th century regarded the dearth of written history, building activity, and artistic output as an indication of a “dark” time in history. Even today, “Hun,” “Goth,” “barbarian,” and, to a lesser degree, “Middle Ages” have negative connotations. Yet the barbarians and nomads, dismissed by the Greeks and Romans as having no culture or heritage, did recognize the sophistication of the Romans and sought to incorporate aspects of their culture, including classical forms and realistic imagery. In the 20th century, some scholars attempted to discontinue the pejorative use of “Dark Ages” and “barbarian,” promoting for a time the use of “migration period,” but the appellation and connotation appears to have been thoroughly embedded. The title of the volume seeks to challenge that preconception and to point out that all was not “dark” in this historical era.

	The book features more than 100 examples of personal ornaments from this period from the Thaw collection, including fine metal, inlay, cloisonné, and mounted gemstones. The pieces were collected as singles and not as part of a grave burial collection. Through extrapolation from similar objects interpreted in a grave context, the pieces can be assigned to specific periods and regions. In interpreting the significance and meaning of the objects, Adams admits to having “committed one of the graver sins for the archeologist—the purposeful mixing of different types of evidence” in having used historical information to explain archeological findings and vice versa.  The result, however, is a coherent narrative in which the reader can understand the significance and the sequence of the featured objects in an appropriate framework.

	Following the introduction are six chapters examining different facets of the migration and invasions that bridged the transformation of Western Europe from a Greco-Roman world to the modern nation-states. The chapter introductions weave together history and cultural shifts (illustrated with maps), theories of visual art and personal adornment, and the state of craftsmanship/technology. Examples from other collections are included to better illustrate concepts. The remainder of the chapter is devoted to examples from the Thaw collection. Each is illustrated by a large-scale photo plus detail views. For those wanting technical details, the gemstones are identified and the jewelry making techniques are described. The stylistic attributes are discussed and the placement of the piece in its historical and cultural context is elaborated on, usually referencing other documented pieces. The photography and description are detailed enough to inspire and serve as a guide for a contemporary jeweler to design or manufacture archeological “revival” pieces that vastly differ from the Renaissance, Etruscan, or Egyptian objects associated with medieval influence.

	The book ends rather abruptly, in the style of a catalog. The glossary could be more extensive, being dominated by geographic and historical periods rather than jewelry and stylistic terms. The bibliography attests ultimately to the scholarly nature of this work—it is an overwhelming 50 pages.

	Trained as a geologist, art historian, and archeologist, Noël Adams brings her unique scholarly perspective to the technological aspects of metalwork. Less attention is paid to historiography, historical gender studies, cemetery analysis, dating analysis, and anthropological interpretations of burial ritual. The body of historical knowledge is augmented by examining how the pieces were physically made and the origin of materials, though one can only speculate how pieces were commissioned, supplied, bought and sold, or their meanings.

	One favorite of Adams that was unfamiliar to me was “garnet cloisonné” or “framework cloisonné,” where garnets or glass pieces are collet set, giving the appearance of fired glass enamel. She defines this technique as “cold cloisonné” in the glossary. Examples are given of its evolution through Hunnic, Visigothic, and Merovingian periods of the 5th and 6th centuries.

	I enjoyed this book because it gently made me aware of my own preconceived notions about the so-called “Dark Ages,” and then dispelled those notions. The early medieval period is one of the most complex in history—transitioning from long-established cultures of the Roman and Byzantine Empires to domination and displacement by very different peoples. The resulting turmoil eventually settled into an era of assimilation and comingling that would set the stage for a new era of creativity and progress, the “high” Middle Ages that eventually led to the Renaissance. In the introductory sections, the historical and cultural context is presented with just enough information to keep the interest of the average reader. Some of the chapters go into a level of historic detail that may be overwhelming to some, but gemological or jewelry enthusiasts can be satisfied by skipping to sections and illustrations focusing on medieval techniques and styles. Overall, Bright Lights in the Dark Ages is a worthwhile read. @topic:6


Publish Year: 2019 Title: Sourcing Stones with Columbia Gem House Abstract: Figure 1. Left: These trillion-cut blue hyalite opals from Oregon, weighing about 2.25 ct each, are reminiscent of moonstone. Right: Five Montana sapphires, ranging from 0.60 to 1.20 ct, showcase Columbia Gem House’s “GeoCut,” which follows the crystal’s natural shape. Photo by Robert Weldon/GIA.
Eric Braunwart (Columbia Gem House, Vancouver, Washington) spoke to us on how the industry has evolved since he opened his doors in 1976. Columbia Gem House has been a pioneer in the responsible sourcing of gemstones.
Braunwart traces his commitment to ethically sourced gems, those that he can track and trace and align with the company’s fair trade protocols, to a project he worked on with the World Bank in Madagascar about 20 years ago. His involvement with this project led him to set up fair trade standards for his own business—no small feat, as there were no such procedures for the gem and jewelry industry at the time. To create policies, Braunwart and his staff turned to industries such as food and agriculture. The company has remained open to public feedback; this is how Braunwart became passionate about prevention of silicosis in cutting communities. They have collaborated with different entities to create projects to benefit miners and their communities (read about one such project in J.-L. Archuleta, “The color of responsibility: Ethical issues and solutions in colored gemstones,” Summer 2016 G&G, pp. 144–160). The company continues to seek out projects in regions where they can make a difference by setting up schools, medical facilities, and other community needs.
Growing up in the American West led to Braunwart’s interest in the region’s nontraditional gem materials, such as agates, garnets, and petrified wood. Even though his business was involved in more traditional gem materials, he was drawn to the chalcedony, variscite, and turquoise that were not featured in classic jewelry. Today, Columbia Gem House sources and cuts about 150 different varieties of gemstones. American gemstones, such as the faceted blue hyalite opal from Oregon (figure 1, left), are one of their specialties. Much of their current business comes from small designers rather than large corporate interests. They have run their cutting facility in China for 35 years, with a trusted team that can quickly respond to orders.

	Sourcing stones with Columbia Gem House

While the company was in business before millennials were even born, this generation has clearly influenced the company’s sales; many of this year’s buyers in Tucson were people in their twenties representing small designer firms making modest purchases. Braunwart has been able to capitalize on social media (particularly Instagram) to make decisions on materials, colors, and cuts, allowing followers to vote on what types of material to promote. He believes that social media will continue to drive consumers toward ethical and sustainable choices in jewelry, with the full impact being felt within the next five years.

Figure 2. This 21.33 ct blue and green unheated sapphire is from Tanzania. Photo by Robert Weldon/GIA.
The 2019 AGTA show brought many new and established buyers to the Columbia Gem House booth. In fact, Braunwart said that this Tucson show, the company’s 41st, was their most successful ever. He attributes that to a growing interest in sustainably and ethically mined gemstones. Popular items included small baguettes in a variety of colors and materials, unheated Montana sapphire, Cortez pearls, and fossilized coral from Utah. The company’s “GeoCut,” a simple cut that follows the natural shape of the crystal, is used in materials such as Montana sapphire (figure 1, right). One remarkable stone from outside the United States was a 21.33 ct unheated sapphire from Tanzania showing distinct blue and green colors (figure 2). @topic:11


Publish Year: - Title: Pearls: Nature's Sustainable Gem Abstract: A research group is studying marine cultured pearls, like these Tahitians, and their potential as a sustainable gem. Photo by Amanda Luke/GIA.

	Pearls – unlike any other gem – are organic, created inside a living mollusk. Regardless if it forms naturally or is cultured with care, pearls develop beneath the water’s surface amidst plants, animals and an often fragile ecosystem. But have you ever wondered if pearls can help the environment? That’s the question at hand for a group studying the ecological effects of marine cultured pearls.

	Dr. Saleem Ali, director of the Centre for Social Responsibility in Mining at the University of Queensland, Australia, visited Carlsbad, CA on Friday, June 7, 2013 to share his research on the benefits of pearls as a renewable gem and sustainable pearl farming practices with students studying at GIA. Dr. Ali is part of a team researching pearls and their effect on the environment.

	The research group works directly with pearl farmers to understand the pearl supply chain and will use their research to create a set of sustainability standards for the industry. The three-year project, funded by the Tiffany & Co. Foundation, is exploring the environmental impact of pearl farming and ways it can improve water quality, positively impact coral reef conservation and reduce overfishing.

	Already midway through the project, Dr. Ali and his team have identified a distinct positive connection between pearl farming and conservation. According to their research, the need for clean water is an essential part of the cultured pearl industry. “If you want a good quality marine pearl, you need happy oysters, and happy oysters need pollution-free waters,” Dr. Ali said.

	Other environmental factors – such as marine life – also play a significant role. Dr. Ali and his team examined the effects of pearl farming on coral reefs to learn what practices can help sustain the reefs. The critically endangered ecosystems are home to many species of fish that help maintain ocean biodiversity and provide nutrients for mollusks. Climate change and bleaching from pollution threaten these delicate reefs. Dr. Ali and his team study all potential threats since even small things – such as the type of netting material used in pearl farming – can have a negative effect on the health of coral reefs.

	Dr. Ali also reviewed the impact of pearl farming on local economies. He said their research shows that pearl farming diversifies these economies and is able to coexist with tourism and the fishing sector. In fact, pearl farming also provides more income opportunities for residents so they don’t have to rely on fishing, which reduces the risk of overfishing.

	As the project continues in the next year and a half, Dr. Ali and his team will explore opportunities to brand pearls as sustainable and promote their environmental benefit. “Pearls are unique – they are the only renewable gemstone in the human timescale,” said Dr. Ali. Since 1999, however, pearl exports in French Polynesia have increased, but value decreased. The team hopes that if consumers know pearls are a renewable resource and can improve the environment, their value will increase.

	Students were very interested in how Dr. Ali’s research could affect the pearl industry. One student, whose family works in the cultured pearl industry, said she was eager to share what she learned back home. “It was great to get a different perspective… and know there is a way to be more sustainable in this industry,” she said.

	Dr. Ali emphasized that sustainability is a natural part of pearl farming – the key is to allow everything to exist together. There is “a lot of potential” for students planning to enter the cultured pearl industry, he added.

	Dr. Saleem Ali presents his research to GIA students and staff in Carlsbad, CA. Photo by Kevin Schumacher/GIA.

	Marine pearl farms, like this one in the South Pacific, are the focus of a three-year research project on the environmental impact of pearl farming. Photo by Amanda Luke/GIA.

	Students at the lunchtime presentation learned how the research group is exploring ways to brand pearls as sustainable. Photo by Kevin Schumacher/GIA. @topic:5


Publish Year: 2010 Title: Possible “Sister” Stones of the Hope Diamond Abstract: For more than a century, historians have debated the existence of “sister” stones to the Hope diamond, most notably the Brunswick Blue and the Pirie diamonds. The recent discovery of a lead cast of the French Blue, the Hope’s precursor, has provided a more accurate model of that diamond, which disappeared in 1792.Computer models of the French Blue and its parent stone, the Tavernier Blue, were used to determine whether other diamonds might have been created when the Tavernier Blue was cut into the French Blue, or when the latter was cut into the Hope. The results show that it was not feasible for other significant diamonds to have been created during any recutting. @topic:10


Publish Year: 1999 Title: The Identification of Zachery-Treated Turquoise Abstract: Over the last 10 years, millions of carats of turquoise have been enhanced by a proprietary process called the Zachery treatment. Tests show that this process effectively improves a stone’s ability to take a good polish and may or may not improve a stone’s color. It also decreases the material’s porosity, limiting its tendency to absorb discoloring agents such as skin oils. Examination of numerous samples known to be treated by this process revealed that Zachery-treated turquoise has gemological properties that are similar to those of untreated natural turquoise, and that the treatment does not involve impregnation with a polymer. Most Zachery-treated turquoise can be identified only through chemical analysis—most efficiently, by EDXRF spectroscopy—as it contains significantly more potassium than its untreated counterpart. @topic:8


Publish Year: 2017 Title: CVD Synthetic Diamond Mimicking Natural Stone Abstract: Figure 1. This 0.51 ct CVD synthetic diamond, submitted to GIA for update service, yielded some surprising results. Photo by Johnny Leung.

A 0.51 ct round brilliant (figure 1) was recently submitted to GIA’s Hong Kong laboratory for update service to verify the results from a diamond grading report issued in 2014. Investigation showed that its properties were much different from the diamond in the original report and that it was actually a CVD synthetic diamond.

The round brilliant submitted (5.18–5.20 × 3.11 mm) had H-equivalent color grade, much lower than the D color of the diamond submitted in 2014 (5.07–5.09 × 3.15 mm). Its IF-equivalent clarity was better than the VVS1 clarity of the original stone, however. Only pinpoints and blemishes observable with greater than 10× magnification were found in this specimen. A GIA report number inscribed on the girdle was easily identified as a fake (figure 2). A minor difference in weight was also observed: an “increase” from 0.50335 ct to 0.51444 ct.

Figure 2. The GIA report number of a natural diamond graded three years earlier
was inscribed on the CVD synthetic diamond shown in figure 1. Photo by Billie Law.
Infrared absorption spectroscopy identified the synthetic as type IIa and led to further spectroscopic testing. Photoluminescence (PL) spectroscopy was performed at liquid nitrogen temperature, and spectra were collected with various excitation wavelengths. A very strong SiV– doublet observed at 736.6 and 736.9 nm indicated a synthetic diamond. Under the short-wave UV radiation of the DiamondView, the sample showed green fluorescence but, interestingly, none of the obvious layered growth structures that CVD synthetics usually display. All gemological and spectroscopic features confirmed that the stone was CVD synthetic with post-growth HPHT annealing. This is another example of the importance of using a combination of tests and data to identify a stone. GIA’s laboratories continue to develop and implement various measures to identify possible fraud. @topic:4


Publish Year: 2017 Title: A Melee-Sized CVD Synthetic Diamond in Pearl and Diamond Jewelry Abstract: Figure 1. A pair of pearl and diamond earrings set with about 200 natural melee diamonds and one CVD synthetic melee. Photo by Jun Su.

Since 2012, CVD synthetic diamonds have been tested and identified by NGTC labs in China, typically in sizes above 0.20 ct. Since 2015, a large number of melee-size colorless and near-colorless synthetic diamonds have been detected in daily screenings at NGTC labs. Melee-size HPHT synthetics are accurately screened and identified at NGTC labs using new devices, some of them developed by NGTC. Melee-size CVD synthetic diamonds were reported by GIA’s Mumbai lab earlier this year (A. Krawitz, “GIA finds significant undisclosed synthetics,” Diamonds.net, March 7, 2017).

In March 2017, NGTC’s Beijing lab received 24 pieces of pearl and diamond jewelry (including the earrings seen in figure 1) from a domestic client, who claimed they were imported. Synthetic melee diamonds were identified in 14 of the 24 pieces. Most of the synthetic specimens were HPHT grown, but one was a melee-size CVD synthetic. The near-colorless CVD round brilliant circled in figure 2 was mounted in a pearl earring with about 200 natural melee diamonds. The estimated weight of this CVD melee is 0.01 ct. No obvious inclusions were found under 10× magnification.

Figure 2. A CVD synthetic diamond (circled in red) was mounted in an earring along with very similar-looking natural melee diamonds. Photo by Shi Tang.
Using NGTC’s GV5000 rapid screening instrument, the UV luminescence of a group of diamonds can be observed at the same time. Unlike colorless to near-colorless HPHT synthetic melee, which normally displays strong phosphorescence, the CVD phosphorescence reaction tends to be weak or inert. The GV5000 provides broadband UV excitation, in which colorless to near-colorless HPHT synthetics display strong greenish blue phosphorescence for about 3–60 seconds. Colorless to near-colorless CVD synthetics normally emit weak phosphorescence that lasts less than 3 seconds, while natural diamonds very rarely show phosphorescence with medium to weak intensity for 1 to 2 seconds. Also, the fluorescence color under the GV5000 is mostly blue-white for natural diamonds, strong greenish blue for HPHT synthetics, and bluish green or green or orange to red for CVD synthetics (colorless to near-colorless). We noticed the green fluorescence and weak green phosphorescence of this melee and conducted further testing. The green fluorescence and phosphorescence were more pronounced in the DiamondView (figure 3), but the layered growth structure of CVD synthetics was still not seen due to the specimen’s small size.

Figure 3. Left: The CVD-grown melee diamond (red arrow) shows green fluorescence in DiamondView imaging, while the natural melee below it exhibits blue fluorescence. Right: The DiamondView reveals the green phosphorescence of the synthetic melee, while the natural stone displays no phosphorescence. Images by Shi Tang.
An absorption spectrum collected by micro-FTIR identified it as a type IIa synthetic diamond, with no N-related absorption. A weak 270 nm absorption band usually associated with synthetic origin was detected in the UV-Vis spectrum. With 532 nm laser excitation at liquid nitrogen temperature, the PL spectrum showed strong SiV– center double peaks at 736.6 and 736.9 nm (figure 4), indicating a CVD synthetic. A clear 978 nm emission also appeared in the PL spectrum with 785 nm laser excitation; the assignment of this emission is unknown. The green fluorescence was attributed to an H3 center, which means the specimen was HPHT-treated after growth.

This is the first time NGTC has identified a melee-size CVD synthetic diamond mounted alongside natural stones. This development is concerning, considering the challenge it would pose for gem laboratories. CVD synthetic screening requires more time and effort than HPHT synthetic screening, since the rapid methods of phosphorescence observation currently used would no longer be reliable. Therefore, new screening techniques and instruments are needed.

Figure 4. The melee-size CVD synthetic diamond shows strong SiV– center emissions at 737 nm in the PL spectrum, as collected with a 532 nm laser. @topic:4


Publish Year: 2021 Title: Pinctada maxima Pearls from Operated Mollusks, Sudoite in Ceramic-Age Caribbean Jewelry, Persian Turquoise Field Report, and More Abstract: We invite you to cozy up with the new Fall edition of G&G! Travel to Western Australia as we continue the series on Pinctada maxima pearls, this time with a focus on cultured pearls harvested directly from operated marine mollusks. Then let two historical articles transport you back in time with the discovery of Ceramic-Age objects fashioned from sudoite in the Lesser Antilles and a look at the state of Iran’s Neyshabur turquoise mine, the source of treasures dating back to the Neolithic period.
“An examination of lapidary craft from five archaeological excavations in the French West Indies has revealed the use of a rare gem material: sudoite.”
This issue opens with part two in a three-part series on Pinctada maxima pearls. Artitaya Homkrajae and fellow GIA researchers investigate the internal structures of 86 saltwater cultured pearls collected directly from operated mollusks off the coast of Western Australia. Real-time microradiography and X-ray computed microtomography revealed several broad growth structural types, some of which may overlap with their natural counterparts. This study illustrates some of the challenges laboratories face, as the distinction between non-bead cultured and natural pearls is not always clear.
An examination of lapidary craft from five archaeological excavations in the French West Indies has revealed the use of a rare gem material: sudoite. In the second article of this issue, Alain Queffelec and coauthors provide a mineralogical and geological analysis of nine sudoite objects to understand the provenance of the material and the trade networks of Amerindian cultures from the Early Ceramic period.
Next, Philippe Belley and Aaron Palke compare trace element chemistry and visible light absorption spectra of two purple gem spinels from Luc Yen, Vietnam, and Badakhshan, Afghanistan. Their study presents the first reported example of a saturated purple color in spinel attributed to chromium and cobalt.
Historically, the Neyshabur mine has produced the majority of Iranian turquoise, which possesses a unique color and quality and has been prized by civilizations dating back to the Neolithic period. In this field report, Bahareh Shirdam and coauthors uncover the current state of the Neyshabur mine and document the different techniques used to extract this vivid blue to green gem turquoise.
Highlights from the Lab Notes section include a unique emerald cabochon with two distinct chatoyant bands, the creative use of manufactured glass to imitate star sapphire, and zircon with unusual color-change behavior when viewed under different illuminants. Explore the inner beauty of gemstones with the Micro-World section, featuring a stunning apatite crystal floating over a cloud of silk in a star sapphire, a diamond with an octahedral-shaped cloud inclusion resembling a six-pointed star, and hematite reminiscent of a blossoming rose in aquamarine. In Gem News International, you’ll find a study on mabe pearl cultivation in the French territory of Mayotte, as well as a report on Fura Gems’ inaugural auction for rough untreated Mozambican rubies, and much more.
We hope you enjoy the latest issue of Gems & Gemology! @topic:5


Publish Year: 2014 Title: Shell Pearl as a Pearl Imitation Abstract: Figure 1. These shell pearls range from 10 to 12 mm and display black, white, and golden colors. Photo by Jian Xin (Jae) Liao.

              Imitation pearls made of shell, or “shell pearls,” have a long history in the jewelry market and have been reported in previous Lab Notes columns (Fall 1984, p. 170; Winter 1986, p. 239; Summer 2001, pp. 135–136; Summer 2004, p. 178). The shell beads are often coated with artificial materials to simulate a wide variety of natural and cultured pearls in the market. Recent submissions of such imitations to GIA prompted researchers in the lab to obtain several samples from a commercial website. Labeled as shell pearls (figure 1), they resembled Tahitian black, white, and yellow/golden South Sea cultured pearls.

Although the samples were similar in appearance and heft to cultured pearls, routine gemological tests revealed unnatural surface characteristics. The black shell pearl necklace also exhibited multicolored but rather oily orient. Magnification showed numerous minute particles with a glittering effect (figure 2, left), as well as a lack of the obvious overlapping nacre platelets commonly found in nacreous pearls. These features suggested that an artificial coating had been applied to the bead. Inspection near the drill holes of some samples revealed chipping and peeling of this very thin coating, exposing white bead-like shell material underneath (figure 2, right).

	Figure 2. Left: The surface of the imitation pearls contained a glittery coating rather than overlapping nacre platelet structures (magnified 112.5×). Right: White bead-like shell material was exposed at a damaged area near the drill hole (magnified 10×). Photos by Chunhui Zhou (top) and Jessie Yixin Zhou (bottom).
X-radiography showed only the inner bead, with occasional parallel banding and cracks—similar to the banding and trematode “tunnels” common in some saltwater shell beads—while the outer coating remained transparent (figure 3). EDXRF analysis detected a high concentration of bismuth, which usually does not occur in pearls but had been reported previously in coated natural and cultured pearls (Fall 2005 Gem News International, pp. 272–273; Winter 2011 Lab Notes, pp. 313–314). Finally, Raman spectroscopic analysis of the exposed white bead identified it as aragonite. These results, coupled with the bead’s inert reaction under X-ray fluorescence, confirmed it was made of saltwater shell.

	Figure 3. X-radiography revealed banding and cracks in the inner shell beads.
We have noted the use of the terms shell pearl or just pearl for such imitations in product descriptions on numerous commercial websites. Such inappropriate nomenclature could be misleading to inexperienced buyers. According to the CIBJO Blue Book on pearls, “Imitations or simulants of natural pearls and cultured pearls . . . shall be immediately preceded by the word ‘imitation’ or ‘simulated’, with equal emphasis and prominence . . . as those of the name itself.” Imitation pearl would be the proper name of this material, and consumers need to be aware of its true identity. @topic:5