Publication Year: 2018 Title: Natural Emerald with Inclusions Along Three Directions Abstract: Figure 1. This 10.48 ct sugarloaf emerald from Zambia shows a vivid and highly saturated green color. Photo by Yizhi Zhao.

Recently, Guild Gem Laboratories received a 10.48 ct sugarloaf emerald (figure 1) for identification and origin determination. The refractive index (approximately 1.58) and specific gravity (approximately 2.80) fell within the range for beryl, and Fourier-transform infrared (FTIR) testing confirmed it as natural emerald. Additionally, energy-dispersive X-ray fluorescence (EDXRF) analysis revealed Fe, V, and Cr contents consistent with those in Zambian material.

Figure 2. Platy inclusions in the emerald in three directions, intersecting at 60/120 degree angles viewed along the c-axis. Photo by Yujie Gao; field of view 2.8 mm.

Figure 3. Top: The hexagonal inclusions in the basal plane are parallel to the orientation of the platy inclusion described in figure 2. Field of view 3.1 mm. Bottom: A thin layer exhibiting growth lines is perpendicular to the emerald’s c-axis. Photos by Yujie Gao.
The stone showed interference colors when placed under a polariscope with the bottom facing up. With a conoscope, the optic axis of this emerald was determined to be perpendicular to the bottom. Using the microscope, we found thin platy inclusions arranged in three directions intersected with each other at 60/120 degree angles (figure 2). Those inclusions were mainly dark brownish and transparent with well-formed rectangular shapes, some of which exhibited a light bodycolor resembling an unhealed fracture. Evenly distributed reflective light could be seen at certain angles. We deduced that those inclusions had relatively smooth surfaces, which means that their original crystal faces were not corroded during the emerald’s formation. Further observation revealed hexagonal inclusions in the basal plane. Owing to uneven development during their crystalline formation, several of them were nearly triangular in shape. Their sides were parallel to the direction of the platy inclusions (figure 3, top). We also found distinct growth lines near the bottom of the sugarloaf perpendicular to the c-axis. These platy inclusions appeared to be concentrated sparsely in a thin layer with a thickness around 1.5–2.0 mm, as shown figure 3 (bottom). The sparseness of the oriented inclusions resulted in the absence of asterism or cat’s-eye phenomena.

Figure 4. Proposed illustration of hexagonal inclusions in the basal plane and platy inclusions along the prismatic faces. Illustration by Yujie Gao.
Considering the optic axis, we concluded that the platy inclusions grew along the hexagonal prismatic emerald faces, with the hexagonal platy inclusion parallel to the basal plane, as illustrated in figure 4. However, it is still unclear whether they were syngenetic or exsolution, since their well-preserved shapes showed little evidence of corrosion and there was insufficient evidence of exsolution. @chapter:9


Publication Year: 2023 Title: A Red Herring in a Red Garnet Abstract: Gas bubbles hide just beneath natural crystal inclusions in this garnet and glass doublet. Photomicrograph by Emily Jones; field of view 1.58 mm.
At first glance, a 2.54 ct round mixed-cut stone examined by the author presented itself as a natural red garnet. Microscopic inspection revealed a host of transparent crystals and widespread epitaxial needles, both typical inclusions for garnet. Upon closer inspection, however, some of the apparent “crystals” were recognized as gas bubbles, betrayed by their smooth spherical forms (see above). This distinction can be easily missed without careful examination under high magnification. Additional observations and testing conclusively identified the material as pyrope-almandine garnet fused with manufactured glass. As with most garnet-topped doublets, the garnet portion was cut to occupy the crown while the glass made up most of the pavilion so that the natural inclusions of the garnet top masked the telltale signs of manufactured glass beneath. @chapter:19


Publication Year: 2006 Title: Identification of “Chocolate Pearls” Treated by Ballerina Pearl Co. Abstract: Treated cultured pearls with a “chocolate” coloration have entered the market from several sources. Gemological, spectroscopic, and chemical analyses were performed on both untreated and treated cultured pearls to provide a better understanding of the “chocolate” treatment process that is used by one company (Ballerina Pearl Co.) and to determine how these products can be identified. It is likely that the organic components in black cultured pearls were bleached to create the brown coloration; no foreign coloring agent was detected. Cultured pearls treated by this method can be identified based on their unusual coloration, characteristic fluorescence, UV-Vis-NIR reflectance and Raman spectra, and trace-element composition. @chapter:40


Publication Year: 2015 Title: Chinese Freshwater Pearl Culturing, Overall Market Summary Abstract: Figure 1. Jack Lynch of Sea Hunt Pearls displays strands of baroque bead-nucleated Chinese freshwater cultured pearls at his AGTA booth. Photo by Duncan Pay/GIA.

Also at the AGTA show, Jack Lynch (Sea Hunt Pearls, San Francisco) offered his perspective as a pearl entrepreneur (figure 1). Over the years he has introduced many trends in cultured pearls and pearl culturing techniques to the market, including soufflé pearls: large baroque Chinese freshwater cultured pearls with fine luster, interesting colors, and light heft (Spring 2010 GNI, pp. 61–63, www.gia.edu/gems-gemology/spring-2010-gem-news-international).

Lynch’s reputation for introducing new products and styles leads to the same question at his Tucson booth every year: “What’s new in the pearl business?” Typically the question centers on freshwater cultured pearls from China. This year, he noted, the emphasis of Chinese pearl culturing innovation was on size. As evidence, Lynch showed us a remarkable necklace composed of round freshwater cultured pearls graduating from 15.4 to 19.3 mm (figure 2). He had never seen a necklace of this size and quality, with beautifully matched, top-quality round pearls. His supplier only had four available, and this necklace was the finest.

Figure 2. This spectacular strand of Chinese freshwater cultured pearls is graduated from 15.4 to 19.3 mm. Lynch described it as the best of four such strands available when he purchased it from his supplier. Photo by Duncan Pay/GIA; courtesy of Sea Hunt Pearls.
Rather than producing baroque pearls, like the soufflé, the drive is now toward bead nucleation and large, spherical pearls. As producers initially sell by weight, there is a financial imperative to produce bigger pearls.

Although producers are ultimately striving for quality, quantity is still the most important factor. Lynch felt that the goal of Chinese freshwater pearl culturing has always been the production of “large white round pearls” and that success to date has been limited, with extremely small volumes of fine-quality product available. Certainly, Lynch knows of no more than a handful of examples like the necklace he showed us at his AGTA booth.

Lynch was uncertain which kind of nuclei or culturing process is used for these larger spherical pearls, but he said the results speak for themselves. He believed it might be similar to the proprietary process used by Chinese producer Grace Pearl for its “Edison” pearls. In this method, genetically selected mussels are implanted using tiny beads instead of mollusk tissue. “Edison” is a backhanded tribute to American inventor Thomas Edison.

Lynch noted that producers are continually hybridizing the mussels used for cultivation, and that they remain very tight-lipped about their methods. Without drilling, sawing, or X-raying the pearls, it is difficult to fully understand the processes or growth methods used.

He mentioned that some of the top producers in China have become increasingly “bullish” about their products, comparing them very favorably with the best South Sea cultured pearls. Because the Chinese domestic market is so strong, its consumers are prepared to pay higher prices than consumers in countries like the U.S. The producers are, in effect, pricing their products out of these markets. According to Lynch, the message from these producers is that the traditional stature of their product vis-à-vis other pearl types must change. In the meantime, they will not consider lowering their prices to satisfy traditional export markets in the U.S. and Europe.

We noticed he had a comprehensive selection of baroque freshwater cultured pearls. Lynch said that while there is moderate market demand for baroque pearls, much of the production originates from cultivators striving for spherical pearls, because “that’s where the money is.” In his opinion, much of the current Chinese production is similar to “Kasumiga pearls” with textured skins that display very strong orient over natural colors (figure 3).

Figure 3. These 16 × 13 mm bead-nucleated baroque Chinese freshwater cultured pearls have impressive heft along with striking orient and warm natural colors. Photo by Duncan Pay/GIA; courtesy of Sea Hunt Pearls
Known as “ripple” pearls for their textured surface, they are highly regarded for their prismatic effects, near-metallic luster, and organic shapes. As a strand wholesales for just a few hundred dollars, they present a “big look” for a modest outlay. For example, a very rough estimate on the 15.4–19.3 mm round necklace shown in figure 2 would be $10,000 per strand, whereas these baroque multicolor necklaces cost just a few hundred dollars per strand.

Lynch’s higher-quality baroque Chinese freshwater pearls are larger and have smoother skins (figure 4), so the price rises accordingly. The next examples he showed us cost two to three times more. According to Lynch, they are very fashion-forward and still represent a tremendous value for the size.

Figure 4. These slightly larger, higher-quality baroque cultured pearls have smoother skins than those in figure 3. As a consequence, they are priced two to three times higher. Natural-color goods are in the foreground, while the white pearls have been bleached for a more uniform appearance. Photo by Duncan Pay/GIA; courtesy of Sea Hunt Pearls.
The higher-quality baroque strands Lynch showed us were also bead nucleated, but the bead had been positioned more conventionally, in the gonad of the mollusk. This technique produces a different type of pearl, known in the trade as a “fireball” (D. Fiske and J. Shepherd, “Continuity and change in Chinese freshwater pearl culture,” Summer 2007 G&G, pp. 138–145, www.gia.edu/gems-gemology/summer-2007-continuity-change-chinese-freshwater-pearl-culture-fiske).

All the peach to pink colors in these strands are natural, Lynch told us. Bleaching produces the white product. Unlike the soufflé pearls, which are typically hollow after being drilled, these bead-nucleated pearls have impressive heft. They sell very well, according to Lynch, and no two necklaces are uite the same due to the uniqueness of every pearl. As an aside, he told us that the weight of the pearls he shipped to the show was around 489 pounds (about 221 kg), much of that consisting of bead-nucleated freshwater cultured pearls.

Next, he showed us some tissue-nucleated (non-beaded) round freshwater cultured pearls (figure 5). These 5–6 mm spherical pearls were impressively uniform with high luster and crisp reflections from smooth skins, making them an excellent substitute for an akoya strand. Finding this sort of quality is very difficult these days, Lynch told us. These also cost a few hundred dollars per strand.

Although Lynch carries a wide stock of Chinese freshwater pearls, most of his resources go into purchasing Tahitian, South Sea, and akoya cultured pearl products. All in all, he said, supply of every top-quality cultured pearl type is very limited, and competition for available product is very high. The increase in Chinese consumption has drastically affected supply for U.S. and European wholesalers. Fortunately, Lynch told us with a sense of relief, he has been a “pearl hoarder” for many years, so he has a significant inventory to draw upon.

Figure 5. These tissue-nucleated Chinese freshwater cultured strands resemble fine akoya cultured pearls. Photo by Duncan Pay/GIA; courtesy of Sea Hunt Pearls.
Lynch suggested that the Chinese domestic market does not know what the market value of many products might be elsewhere. The Chinese have a different mindset than consumers in the West, he told us, citing a fashion example: “You’ll pay more for couture items in Shanghai than in Paris… If it’s expensive, it’s better.” Although many commentators insist the Chinese economy is slowing down and no longer enjoying double-digit percentage growth, Lynch said that the emergence of a large middle class that wants all the trappings of wealth is driving up the market prices for gems and pearls. He noted that the Chinese like to display their wealth, and jewelry is an obvious way to do that.

Asked what was selling this year, Lynch explained how his business has changed. He used to sell more volume at the Tucson show, especially freshwater items wholesaling for $300 to $600 apiece. Today he handles fewer transactions, but the average transaction has increased dramatically. Lynch’s perception is that spending habits have changed as the middle class in the U.S. has shrunk. He finds fewer consumers looking for $1,000 items. Instead, he sees purchasers from a higher income bracket looking for a $20,000 or $30,000 piece.

Figure 6. Fine Tahitian and South Sea cultured pearl singles and pairs are in high demand with designers for one-of-a-kind custom jewelry pieces. Photo by Duncan Pay/GIA; courtesy of Sea Hunt Pearls.
Lynch now sells far more round white South Sea and Tahitian goods, along with fine single pearls and pairs (figure 6). The first piece he showed us was a superb, exceptionally large round South Sea cultured pearl of 18.2 mm (figure 7). Lynch said he buys with designers in mind, as items like this are far more affordable than a strand and make excellent centerpieces for custom jewelry pieces. The price for such a piece would be approximately $6,000, whereas a necklace of this quality would cost many tens of thousands of dollars.

Figure 7. This superb spherical South Sea cultured pearl measures 18.2 mm in diameter and weighs 8.25 grams. Photo by Duncan Pay/GIA; courtesy of Sea Hunt Pearls.
Finally, Lynch pulled out a uniquely shaped Tahitian baroque cultured pearl (figure 8). Its flattened shape would allow it to sit especially well as a pendant. At 19.7 mm, it was large. Even though the pearl was very baroque, its color was exceptional. This piece had the style and substance to really make a statement at a reasonable price (a couple of thousand dollars).

Figure 8. This 19.7 mm Tahitian Sea cultured pearl weighs 2.45 momme (9.19 grams). It would make a fine centerpiece for an item of custom jewelry. Photo by Duncan Pay/GIA; courtesy of Sea Hunt Pearls. @chapter:14


Publication Year: 2016 Title: Book Review: Collector’s Guide to the Amphibole Group Abstract: By Robert J. Lauf, softcover, 96 pp., illus., publ. by Schiffer Publishing, Atglen, Pennsylvania, 2015, $19.99.

Collector’s Guide to the Amphibole Group joins a long list of Schiffer Earth Science Monographs authored by Robert Lauf. These individual works focus on a specific mineral group and are intended to bring a greater appreciation of the more technical aspects of the mineralogical sciences to the serious gem and mineral collector, and, perhaps, to remind professional mineralogists of the aesthetic appeal of the minerals they are studying. Given the importance of nephrite jade in the gem industry and the occasional occurrence of gem-quality pargasite, edenite, and richterite, this work should also be of general interest to the practicing gemologist.

	The introduction gives a brief discussion of the gemological and industrial uses of various amphibole minerals. The next chapter plunges into the confoundingly complex realm of amphibole taxonomy, crystallography, and crystal chemistry. The difficulty (or impossibility) of finding a simple way to present the naming conventions in the amphibole group quickly becomes apparent. The problem is caused by the ability of the amphibole structure to accept a wide range of atomic substitutions in its crystallographic sites. This, in turn, means that there are an exceedingly large number of ways in which nature can put together atoms to form an amphibole mineral. While much of the information presented here is likely to be technically daunting for many amateur mineralogists and gemologists, if the reader can make it through this section unscathed, he will be rewarded with two much more accessible chapters concerning the geological formation of amphiboles and another chapter which separately covers all of the amphibole species. All of the amphiboles described here are from the very rare species that occur in only one locality, such as joesmithite, to the common examples such as hornblende. Each mineral is described from its initial discovery and naming to the well-known localities to general discussion of typical geological conditions of its formation.

	The entire book is perfectly complemented by high-quality images of a multitude of stunning amphiboles. The composition and execution of the mineral and rock photography are, in general, quite exceptional. Unfortunately, far too many of the photos lack field of view measurements or any kind of indication of the size of the specimen.

	This work, along with the other monographs in this series, should satisfy the curiosity of serious gem and mineral collectors wanting to understand more about the technical and scientific aspects of their hobby or profession. Perhaps the words of Roberta Oberti in the foreword are relevant when she states her hope that this book can serve as a bridge between the collector and the scientific community. @chapter:4


Publication Year: 2006 Title: Winter 2006 Gem News International Abstract: Diamonds
            Update on Diamond Trading in Sierra Leone
            Jewelry Repair Damages a Diamond
Colored Stones and Organic Materials
            Green Augelite from Peru
            Bicolored Beryl from the Erongo Mountains, Namibia
            Diopside from Afghanistan
            California Jadeite with Copper Inclusions
            Labradorite from Chihuahua, Mexico
            Gem News from Mogok, Myanmar
            Moonstone from Madagascar
            A Large Phenomenal Fire Opal with Possible Uranium-Related Luminescence
            “Sunset” Quartz: A New Gem Material from Brazil
            Swedish Blue (Slag) and Swedish Iron Ore
            Tourmaline Mining at Nandihizana, Madagascar
            Green Uvite from Afghanistan
Synthetics and Simulants
            Synthetic Corundum “Gem Rough” in Tanzania
            Small Treated Synthetic Pink Diamonds Set in a Ring
Treatments
            Update on “Chocolate” Tahitian Cultured Pearls
            Treated Violetish Blue to Violet Quartz from Brazil
            Circular Ring-Like Inclusions in a Diffusion-Treated Sapphire
            Diffusion-Treated Synthetic Sapphire with Unusual Fluorescence
Conference Reports
            32nd Annual GSJ Gemological Conference
            International Mineralogical Association Biennial Meeting
Announcements
G&G Online Conference Calendar
            GIA’s Russell Shor Wins Liddicoat Journalism Award for Gems & Gemology Article
            Visit Gems & Gemology in Tucson
Exhibits
            Colored Diamonds at the Natural History Museum
            Jewelry History at the Newark Museum
            Symbols of Identity—Jewelry of Five Continents
            Gold at AMNH
            Jewelry of Ben Nighthorse
            South Sea Pearls at the GIA Museum
            French Jewelry at the Legion of Honor
            Native American Jewelry

To view the full section, download the PDF above. @chapter:7


Publication Year: 2024 Title: Cloud Inclusions Causing Fancy Light Blue Color in Diamond Abstract: Figure 1. The 2.20 ct Fancy Light grayish blue diamond. Photo by Jian Xin (Jae) Liao.
The most common cause of blue color in diamond is the incorporation of boron into the diamond crystal lattice (type IIb), such as the recently auctioned Cullinan Blue (Summer 2022 Lab Notes, pp. 216–217). Other causes of blue color in diamond are hydrogen-related absorption (C.H. van der Bogert et al., “Gray-to-blue-to-violet hydrogen-rich diamonds from the Argyle mine, Australia,” Spring 2009 G&G, pp. 20–37) and irradiation, either natural or artificial. Artificial irradiation using an electron beam is a common diamond treatment (Winter 2020 Lab Notes, pp. 517–518).

Figure 2. The mid-infrared spectrum of type IIb diamond compared to the 2.20 ct grayish blue diamond, which was type IIa with no boron or hydrogen-related features. Spectra are offset vertically for clarity.

Figure 3. The UV-Vis-NIR spectrum of the 2.20 ct grayish blue diamond compared to a UV-Vis-NIR spectrum with typical hydrogen absorbance (notably at ~545 nm) and broad bands at ~700–800 nm, causing the desirable violet to blue colors. The inset shows typical colors associated with this absorbance spectrum. The red trace is also inconsistent with type IIb absorption. With a slight rise to higher energy, a yellow color is expected. Spectra are offset vertically for clarity. Inset photo by Robert Weldon.
Recently submitted to the New York laboratory for colored diamond grading service was a 2.20 ct Fancy Light grayish blue diamond (figure 1). Compared to the Cullinan Blue, which was graded as Fancy Vivid blue on GIA’s color grading scale, this diamond was type IIa (i.e., no boron) (figure 2). In addition to the absence of boron-related impurities, this diamond lacked any hydrogen-related impurities (observed in the ultraviolet/visible/near-infrared spectrum in figure 3) (van der Bogert et al., 2009) or any GR1-related color centers, thus ruling out these major causes of blue color in diamond. Instead, the UV absorption for the 2.20 ct diamond was similar to what would be expected for a yellow type Ib (isolated nitrogen) diamond (figure 3).

Figure 4. Fine milky cloud inclusions are responsible for the natural blue color of the type IIa diamond, shown in darkfield illumination. Photo by Paul Johnson.
The diamond was heavily included with fine cloud-like inclusions, giving it a milky appearance (figure 4). Clouds, sometimes hydrogen-related, often cause gray, brown, black, or even white color in natural diamonds (S. Eaton-Magaña et al., “Natural-color fancy white and fancy black diamonds: Where color and clarity converge,” Fall 2019 G&G, pp. 320–337). In this case, the cloud micro-inclusions caused Rayleigh light scattering, creating a desirable blue color and not the expected yellow color resulting from a slight rise in absorption from lower to higher energy.
Based on these cloud inclusions, the diamond was given a final color grade of Fancy Light grayish blue, a natural origin of color, and an I3 clarity grade. @chapter:11


Publication Year: 1994 Title: Fall 1994 G&G Book Reviews Abstract: “Diamonds”
By Fred Ward, 64 pp., illus., publ. by Gem Book Publishers, Bethesda, MD, 1993. US$14.95

“Streeter of Bond Street: A Victorian Jeweller”
By Patrick Streeter, 174 pp., illus., publ. by Matching Press, Harlow, England, 1993. US$30.00

“Beads of the World”
By Peter Francis, Jr., 142 pp., illus., publ. by Schiffer Publishing, Ltd., Atglen, PA, 1994. US$19.95

To view the full section, download the PDF above. @chapter:16


Publication Year: - Title: In Search of the Perfect Specimen Abstract: Vincent Pardieu (B.Sc., G.G.A., GIA GG), GIA Supervisor of Field Gemology in Thailand, is somewhat of a legendary figure. After working for ten years as a tour guide in Southeast Asia, he decided to pursue his interest in gems and earned his GIA GG. Pardieu has made numerous expeditions to some of the most remote corners of the world to chronicle the mining, trading, and production of gems. His discoveries enrich GIA course materials.

Were you always interested in gems?

I was always interested in nature, and my love for gems grew slowly over the years. I began to realize that gems belonged to a larger world; they are not just pretty little things. They touch everything: art, history, chemistry, and geology.

Any favorite places you’ve visited?

Going to Vietnam in search of a ruby mine. The landscape was so beautiful it looked like it could have been in a movie. There were vast stretches of rice fields, jungles, and bamboo groves.

Thoughts about your GIA education?

My education from GIA has been extraordinarily helpful. It has been a real asset that has helped me throughout my career. The courses were quite comprehensive, and I learned how to properly identify gemstones – a skill I use daily.

Why is it important to get a specimen from a mine?

GIA has to do its homework to be able to identify the origin of gemstones, and this requires having a reference sample. The best way to get a reference stone is to go to the source.

What is it like at a mining site?

The atmosphere is wonderful – it’s filled with rumors, expectations, and excitement. You have thousands of miners thinking, “This is my chance to become a millionaire!” Some poor diggers will find a beautiful stone and become rich. Some rich businessmen will become poor because they can’t tell naturals from synthetics, and will be tricked into buying imitations.

Any other interesting stories?

The first time I took the 20-stone exam at GIA, I failed it. That was a good thing. When you fail an exam like this, you remember that you don’t know everything. You learn not to be over-confident.

Do you have any advice for students who want to have a career like yours?

Believe in yourself. Just go do it. @chapter:18


Publication Year: - Title: Soul of Brazil Shines in Colorful Collection Abstract: View Gallery

The Institute’s first formal international jewelry collection highlights the spirit and soul of Brazilian jewelry.

	Long-known for its abundance of fine gemstones, Brazil is enjoying an emergence as a source of innovative jewelry design worldwide. GIA’s collection, which features pieces donated by Brazil’s top designers and manufacturers, was built with the support of the industry and the Brazilian Gems and Jewellery Trade Association, and showcases traditional and contemporary designs.

	Renowned Brazilian designer Ruth Grieco helped inspire the idea for the collection when she archived her contemporary, handmade tourmaline cross pendant and 18K gold necklace with GIA after it was mentioned in a book review in the Summer 2003 issue of Gems & Gemology.

	Other high-profile donors include:

		Cathrine Clarke, a well-known Brazilian jeweler: a multicolor gold and eroded watermelon tourmaline brooch/ring.

		Daniel André Sauer, director of Amsterdam Sauer and a longtime GIA supporter: his historical “Constellation” ring, the first South American-designed piece to win the De Beers Diamond International Award in 1966.

		Hans Stern, president of internationally recognized H. Stern Jewellers, Inc.: an Art Nouveau-Classical fusion style brooch, set with a 55-carat aquamarine and 38 diamonds in 18K white gold. The piece represents a classic Brazilian design characteristic of the 1960s.

	“GIA is among the few institutions focused on improving the high standards of the entire jewelry trade,” Sauer said. “The [Constellation] ring is an icon and a landmark for the Brazilian jewelry industry.”

	The 18K yellow gold "Constellation" ring won the De Beers Diamond International Awards in 1966. It features 28 round brilliant cut diamonds with total carat weight of 2.66 carats.  Photo by Don Mengason/GIA, gift of Amsterdam Sauer @chapter:21


Publication Year: 2015 Title: Chemical Analysis of Zircon Abstract: Figure 1. The five zircon samples used in this study, ranging in size from 0.56–21.92 ct, were analyzed for radioactive degradation of their crystal structure.

Radioactive elements such as thorium and uranium existed at higher concentrations during earlier ages of the earth; crystal formations from these periods were therefore more susceptible to acquiring higher concentrations of these materials. Zircon has a particular affinity for attracting rare earth elements such as uranium and thorium into its crystal structure due to similarities in the three elements’ cation sizes, which allows U and Th to substitute for Zr in the crystal lattice, and other bonding properties such as coordination, electronegativity, and cation change. The isotopes break down through radioactive decay, releasing harmful doses of radiation to the host crystal. This destroys the crystal structure of zircon until it is nearly amorphous, in a process called metamictization (J.A. Woodhead, “The metamictization of zircon: Radiation dose-dependent structural characteristics,” American Mineralogist, Vol. 76, 1991, pp. 74–82).

In gemology, zircon is categorized by the degree of radioactive degradation that has taken place. Highly degraded material with little to no crystal structure remaining is termed “low” or “metamict” zircon. “High” zircon is crystalline and nearly unaffected by radiation, while “intermediate” zircon is semi-crystalline, between the amorphicity of low zircon and the ordered crystalline structure of high zircon.

Five zircon samples were analyzed in this study based on their apparent crystallinity (figure 1). Raman spectroscopy shows the degradation of the crystal structure from its original structure, which can be illustrated by comparing it to zircon that has not been affected by radiation (figure 2). Infrared spectra (figure 3) also show differences between the low and high zircons, as the former displays peak broadening and baseline irregularities.

Figure 2. Raman analysis of samples 2 and 4, illustrating the difference between “low”
and “high” zircons. Low zircon displaying amorphicity by peak loss and broadening.

Figure 3. FTIR spectra of the zircon samples. The metamict zircons, samples 1 and 2,
display an undefined baseline and broader bands than the high zircons.
Trace-element analysis of high and low/intermediate zircon using LA-ICP-MS illustrated variations in concentrations of several elements, including thorium, uranium, and lead. While uranium and thorium are easily incorporated into the crystal structure, the same is not true for lead, which can only appear in zircon as the byproduct of the radioactive decay chains of thorium and uranium. Due to this property, scientists have been able to accurately date zircons and Earth’s age using isotope ratio analysis by comparing the lead to uranium (238U/206Pb) and lead to thorium (232Th/208Pb) ratios. These results showed the low zircon samples to be far older than the high zircon. Isotopic elemental analysis using LA-ICP-MS (table 1) determined that the low zircon was approximately a billion years old. This is far older than the high zircon samples, which were determined to be approximately 100 million years old. The higher content of radioactive elements earlier in Earth’s formation, along with the longer period of time for metamictization to occur, contributed to the structures of the low zircons.

TABLE 1. Isotopic elemental analysis of zircon using LA-ICP-MS.

Sample
Weight
206Pb
208Pb
232Pb
238U

Greenish yellow "low" zircon
16.32 ct
848.40
54.53
237.10
4529.00

Greenish yellow "low" zircon
21.92 ct
636.67
24.67
603.00
2083.33

Greenish blue "high" zircon
10.14 ct
bdl*
bdl*
51.83
73.17

Near-colorless "high" zircon
0.56 ct
0.81
0.63
200.00
210.17

Blue "high" zircon
1.96 ct
0.12
0.19
85.02
99.98

Trace-element analysis combined with spectroscopy can also detect treatments in zircon. Heat treatment, which is commonly performed on all types of zircon for color modification, can reestablish the crystal structure that was originally destroyed by natural processes. Zircon crystals with high lead content must have experienced a considerable amount of radiation exposure, leading to their lower crystalline order. High-lead zircon samples that show an ordered crystalline structure could have initially been low or intermediate and heat treated to restore the crystal structure. By correlating the trace-element chemistry with other analytical tools such as Raman spectroscopy, it may be possible to determine heat treatment of some types of zircons.

Nearly all blue and near-colorless zircons have undergone heat treatment, as these colors are rarely found in nature; the majority of zircon rough is brown. The blue color of zircon is theorized to come from the chromophore U4+ cations, depending on how the uranium cations interact within the crystal structure. “Electric” blue zircon’s color is typically produced by heating the stone to 1000°C in a reducing environment, while near-colorless material is produced at about the same temperature in an oxidizing environment. Heat treatment of zircons that have not had significant radiation damage can restore the crystallinity at the temperatures used for color modification treatments. Although very metamict zircons must undergo higher temperatures and longer duration of heating to restore a degree of crystallinity, these zircons will never achieve the electric blue color. It is difficult to even produce gem-quality material from this material. Zircon with poor crystallinity has more variation in polycrystalline grain orientation, bond length, element location, and bonding, as well as varying amorphicity. Knowledge of zircon’s chemistry can facilitate the identification of treatments and growth conditions, and can be applied to determine various correlations pertaining to color and origin. @chapter:8


Publication Year: 2013 Title: Imitation Rainbow Moonstone Assemblage Abstract: Figure 1. These assembled cabochons (1.74–10.57 ct) with multicolor iridescence are a skillful imitation of rainbow moonstone. They are composed of a natural rock crystal quartz base with an iridescent coating cemented to a gypsum top, and the entire assemblage is coated in colorless plastic. Photo by Don Mengason.

              The Carlsbad laboratory recently received for examination four semi-transparent to translucent cabochons with a white bodycolor (figure 1), ranging from 1.74 to 10.57 ct. These stones appeared similar to white plagioclase feldspar with multicolor iridescence, known in the trade as “rainbow moonstone” (Summer 1997 Gem News, pp. 144–145). However, a cursory examination proved they were distinctly different: assembled materials composed of a colorless, transparent base cemented to a fibrous white top and coated with a colorless plastic. The stones also displayed an unusual iridescence.

The colorless plastic coating had an RI of 1.55, but this was not useful in identifying the substrate components. The assembled stone fluoresced medium blue to long-wave UV and weak blue to short-wave UV. In polarized light, a bull’s-eye optic figure was resolved in the colorless base material, confirming rock crystal quartz; small fluid inclusions and reflective particles in the bottom sections indicated natural origin. Raman spectroscopy conclusively identified the fibrous top as gypsum.

Microscopic examination revealed an iridescent coating on the quartz section, much like that used on “Aqua Aura” quartz (Fall 1990 Gem News, pp. 234–235). Closer inspection revealed that the iridescent coating was located on the quartz in the join. The colorless plastic coating contained numerous gas bubbles and was easily deformable with a pointer probe. This plastic layer was apparently added to give a vitreous luster to the otherwise dull, waxy gypsum. Gas bubbles in the colorless cement layer made it quite easy to recognize these stones as assemblages.

When viewed face-up, the assemblages made an attractive imitation of rainbow moonstone due to their white bodycolor, milky appearance, and rainbow iridescence. This is the second time the Carlsbad laboratory has examined an assemblage containing plastic-coated gypsum (Fall 2012 Lab Notes, pp. 210–211). Coupling a luster-enhancing coating with an iridescent layer created an interesting imitation rainbow moonstone from two common materials. @chapter:10


Publication Year: 2019 Title: Cat’s-Eye Nephrite Jade from Washington State Abstract: Figure 1. This 1.71 ct cat’s-eye nephrite marquise (11 × 5.5 mm) was mined in Washington State. Photo courtesy of Washington Jade.

Washington Jade (Edmonds, Washington) made its Tucson debut at the AGTA show with nephrite jade from Washington State. They offered a selection of cabochons with and without chatoyancy, along with carvings and rough collectors’ stones. The cat’s-eye nephrite (figure 1) was the most popular by a wide margin, according to Washington Jade’s Nathaniel Cook. Rod Cook, his father and business partner, said that according to many at the show the chatoyancy was reminiscent of the Siberian nephrite that dominates the mid- to high-end Chinese nephrite market.
Cat’s-eye nephrite is found only in Washington and Russia; a deposit in Taiwan has been mostly depleted. While nephrite has been found in northwest Washington since the early 1900s, formal production was limited to an operation west of Darrington, near Everett, that ended in the 1970s. Chatoyant nephrite was documented there in 1974. Since then there has been an artisanal “gray market” for nephrite, with people collecting illegally from streams and state lands, but no formal production. This changed in 2012 when Washington Jade began staking claims. Most of their production comes from a deposit northwest of Darrington.
Washington Jade uses innovative small-footprint mining methods instead of more invasive traditional methods. To identify a jade seam, they use pattern recognition to look at geologic models of the area, along with biological indicators such as tree species and lichen growth. Magnetic and conductivity surveys are used to locate the high-grade portion of the seam. With these methods they can develop a 3D model of the subsurface and focus on the high-grade deposits, in contrast to the traditional model of core drilling, digging up an area with heavy equipment, and taking out all the jade to be sorted by grade. They take only the high-value materials, leaving the rest in the ground. Rod Cook said they backfill and replace the plants after extracting the jade, leaving a very small footprint.
British Columbia is the leading supplier of nephrite, but Washington’s deposits, part of the same geological formation, have yet to be developed. The domestic jade market is much smaller than the Asian market, where jade has been part of Chinese culture for thousands of years. Nathaniel Cook said the nephrite market overall has tightened recently and prices have come down after steady growth the past two decades, but people were still surprised by what they saw as a low price point for the cat’s-eye material.
Rod Cook said there has been an explosion of artisanal jewelers using nephrite. The cat’s-eye nephrite is popular with them, though market acceptance is still in the early stage. He noted that Washington Jade’s output is large enough to meet domestic demand and could be scaled up to the level needed for a jeweler with a few hundred stores. He sees a trend toward jewelry with “less bling” and said that millennials seem to prefer carved material over faceted.

Figure 2. View from inside the “jade cave” on one of Washington Jade’s mining claims. The ceiling appears to be a vein of chatoyant nephrite. Near the opening is another vein, the first couple feet of which provided the rough for many of the stones at the AGTA show. Photo courtesy of Washington Jade.
The Cooks also discovered a “jade cave” (figure 2) in a 200-foot canyon cut by a stream. The jade exposed there informs their geologic models by allowing them to see what a similar structure looks like deep in the ground. The cave formed when a piece of the main chatoyant seam broke loose, slid down the hill, and fell into the stream along one side, creating a tunnel underneath. During the spring melt, water flowed through and created a hydraulic plume, which washed away the overburden on one side and revealed a 2-foot-wide seam of chatoyant jade traveling up into the mountains. Rod Cook estimates there are 30 to 100 tons of chatoyant jade in the cave’s immediate vicinity, and they have confirmed outcrops of the main nephrite lode containing the chatoyant seam for 1,500 feet over two of their 23 claims. Based on their discoveries so far, he estimates that the main lode is 150 to 300 feet wide and “goes for miles.” @chapter:37


Publication Year: 2014 Title: Yellow CVD Synthetic Diamond Abstract: Figure 1. This 0.40 ct square-shaped type Ib CVD synthetic diamond was color graded as Fancy yellow. Photo by Sood Oil (Judy) Chia.

              Gem-quality CVD-grown synthetic diamonds are usually type IIa and occasionally type IaA. In addition, a faceted type Ib yellow CVD synthetic of 3 mm in diameter was reported more than a decade ago (J.E. Butler, “Chemical vapor deposited diamond: Maturity and diversity,” Interface, Spring 2003, pp. 22–26). To the best of our knowledge, no other type Ib examples have been documented in the gem industry since then. The New York laboratory recently examined a gem-quality type Ib CVD-grown synthetic diamond. This Fancy yellow square weighed 0.40 ct and measured 4.20 × 4.12 × 2.55 mm (figure 1).

As is typical for CVD synthetics, the strong silicon-vacancy ([Si-V]–) center was detected as a doublet at 736.5 and 736.9 nm in the 633 nm PL spectrum. The mid-IR spectrum showed a single substitutional nitrogen atom (Ns0) at 1130 and 1344 cm–1 (figure 2). The nitrogen content, which contributed to the yellow color, was calculated from absorption bands in the 1000–1400 cm–1 mid-IR spectral region as 4.5 ppm. Nitrogen can be unintentionally introduced during the growth process; it can also be added deliberately to control the growth rate of single-crystal CVD synthetic diamond. DiamondView images showed curved green lines, indicating changes in conditions during growth (figure 3, left). The DiamondView also revealed green and greenish blue regions of pronounced growth events near the culet, as in the middle image of figure 3. A graphitized stress halo (figure 3, right) and small feathers on the girdle were observed under the microscope. Typical CVD strain—a localized tatami-like structure with low-strain interference colors—was visible under cross-polarized light.

	Figure 2. The yellow CVD synthetic’s mid-IR spectrum revealed single substitutional nitrogen atoms (Nos at 1130 and 1344 cm–1. The diamond Raman band was detected at 1331 cm–1. A hydrogen-related defect was detected at 3107 cm–1, and C-H defects could be observed at 2948, 2920, 2905, 2873, and 2849 cm–1. An unknown doublet was also observed at 3030 and 3032 cm–1.

	Figure 3. DiamondView imaging revealed curved green lines, reflecting changes in growth conditions (left). Pronounced growth events were also observed in green and bluish green regions near the culet (middle). Microscopic examination revealed a graphitized stress halo (right, magnified 112.5×), along with small feathers on the girdle (not shown). Images by Kyaw Soe Moe.
Post-growth treatment was detected: a hydrogen-related defect at 3107 cm–1 and C-H defects at 2948, 2920, 2905, 2873, and 2849 cm–1 (again, see figure 2). We did not observe the neutral charge state of the nitrogen vacancy–hydrogen complex ([N-V-H]0) at 3123 cm–1. These results suggested that the sample was HPHT-treated. An unknown doublet at 3030–3032 cm–1 was also found. Strong N-V (nitrogen-vacancy) defects at 575 (NV0) and 637 (NV–) nm were detected in PL spectrum using a 514 nm laser. The negatively charged nitrogen vacancy–hydrogen complex ([N-V-H]–) is usually contained in as-grown nitrogen-doped single-crystal CVD synthetic diamond, but it is unstable. After HPHT treatment, the hydrogen atoms were dissociated, causing C-H and N-V defects to form. Additional defects, such as H3 and H2, were also detected. Both centers could be introduced in as-grown CVD synthetic diamonds by HPHT annealing. The H3 centers were responsible for the observed green dislocations in the DiamondView image. As-grown CVD synthetic diamonds usually possess an unattractive brown color component. This can be removed by HPHT treatment to achieve an attractive yellow color, as observed in this sample.

Type Ib CVD synthetics are also of interest for technological applications, especially for quantum computing (see E. Gibney, “Flawed to perfection: Ultra-pure synthetic diamonds offer advances in fields from quantum computing to cancer diagnostics,” Nature, Vol. 505, 2014, pp. 472–474). The N-V electron spin could be used as a basic unit of quantum computing, known as a quantum bit or “qubit.” Qubits are not limited to the binary “0” or “1” states of bits in traditional computers, but can simultaneously exist in both binary states and any state in between—a difficult concept to grasp but one that will lead to vastly enhanced computational capacity. Type Ib yellow CVD diamonds of micrometer size were grown and subsequently electron beam–irradiated and annealed by P. Neumann to create NV centers, as noted in his 2012 PhD thesis, “Towards a room temperature solid state quantum processor: The nitrogen-vacancy center in diamond.” After irradiation, the color changed from the as-grown yellow to green, then to purplish pink after annealing. @chapter:15


Publication Year: 2011 Title: A Historic Turquoise Jewelry Set Containing Fossilized Dentine (Odontolite) and Glass Abstract: A set of six antique brooches, set with diamonds and light blue cabochons, was investigated with microscopy, Raman analysis, and EDXRF spectroscopy. Most of the cabochons proved to be fossilized dentine, also known as odontolite (mineralogically, fluorapatite). The brooches also contained turquoise and artificial glass. @chapter:3


Publication Year: 2016 Title: Sphalerite in Topaz Abstract: Figure 1. Oblique diffuse illumination reveals the scene within a colorless topaz. Its sphalerite inclusions all feature an isometric crystal habit, metallic luster reflections, and subtle iridescent interface colors. Photomicrograph by Jonathan Muyal; field of view 4.79 mm.

	A 6.54 ct colorless topaz specimen hosting eye-visible dark crystals was examined at GIA’s Carlsbad laboratory. The crystals exhibited a submetallic luster and showed isometric morphology with step-like growth (figure 1). Some also displayed slightly corroded rounded edges with a reflective iridescent interface. The corroded appearance suggested that these dark crystals are protogenetic inclusions that were present in the growth environment before the topaz began to form. Raman spectrometry and LA-ICP-MS analysis confirmed that the inclusions were sphalerite, a zinc-iron sulfide with the formula (Zn,Fe)S. Fluid inclusions were also observed in this topaz.

	Sphalerite has been described in the literature as a collector’s gem for its rarity and beautiful luster (Summer 1992 Gem News, p. 202). This is the first documented example of sphalerite as a crystal inclusion in colorless topaz, making it an unusual collector’s gemstone. @chapter:0


Publication Year: 1995 Title: An Update on the Ural Emerald Mines Abstract: The emeralds of the Ural Mountains, in what is now called the Russian Federation, have been known for more than 160 years. They were famous worldwide during the early part of the 20th century. However, because little information was made available about these deposits in recent years, many in the gem industry concluded that they had been exhausted. This article reveals that mining and processing are ongoing in the region, with significant reserves of gem-quality emerald still to be exploited. In addition, the reopening of four mines promises to increase commercial production. @chapter:1


Publication Year: 2007 Title: Fall 2007 G&G Book Reviews Abstract: “Adventures at the Bench: Tricks to Overcome a Jeweler’s Daily Challenges”
By Juergen Maerz, 110 pp., illus., publ. by MJSA Press [www.mjsa.org], Providence, RI, 2006. US$34.95

“Jeweled Garden: A Colorful History of Gems, Jewels, and Nature”
By Suzanne Tennenbaum and Janet Zapata, 216 pp., illus., publ. by The Vendome Press, New York, 2006. US$50.00

“Pedras Preciosas No Arte e Devoção: Tesouros Gemológicos na Arquidiocese de Évora [Precious Stones in Art and Devotion: Gemstone Treasures of the Archdiocese of Évora]”
By Rui Galopim de Carvalho, 154 pp., illus., publ. by Fundação Eugênio de Almeida, Évora, Portugal, 2006 [in Portuguese and English, no price information available]

“Shamelessly: Jewelry from Kenneth Jay Lane”
By Nancy N. Schiffer, 240 pp., illus., publ. by Schiffer Publishing Ltd. [http://www.schifferbooks.com], Atglen, PA, 2007. US$59.95

“Costume Jewelry for Haute Couture”
By Florence Muller, 271 pp., illus., publ. by The Vendome Press, New York, 2007. US$75.00

“Pearl Oyster Information Bulletin, No. 17”
By various authors, 48 pp., illus., publ. by the Secretariat of the Pacific Community, www.spc.int/Coastfish/ News/POIB/17/POIB17.pdf, December 2006, free

“The Jeweled Menagerie: The World of Animals in Gems”
By Suzanne Tennenbaum and Janet Zapata, 216 pp., illus., publ. by Thames & Hudson, New York, 2007, US$34.95

“Kimberlite and Related Rocks of India”
By Fareeduddin and M. S. Rao, Eds., 271 pp., illus., publ. by the Geological Society of India [www.gsi.gov.in], Bangalore, 2007, Rs20

“Paraíba Tourmaline “Electric Blue Brilliance Burnt into Our Minds”
By Masashi Furuya, 23 pp., illus., publ. by the Japan Germany Gemmological Laboratory [jggl@sapphire.co.jp], Kofu, Japan, 2007, ¥1,500

“The Geology of Gem Deposits”
by Lee A. Groat, 276 pp., illus., publ. by the Mineralogical Association of Canada [www.mineralogicalassociation.ca], Quebec, 2007, US$50.00

To view the full section, download the PDF above. @chapter:21


Publication Year: 2013 Title: Growth Strategy for Controlling Dislocation Densities and Crystal Morphologies of Single Crystal Diamond by Using Pyramidal-Shape Substrates Abstract: A single synthetic diamond crystal can be used as an electronic device because of its properties, such as a high breakdown field and thermal conductivity. However, defects, such as dislocation bundles, which were formed during growth process, can cause current leakage, higher bandgap, and birefringence. Defect-free single diamond crystal that is large enough to be used as an electronic device is difficult to grow using current methods. For example, the “threading dislocations” can be formed in a CVD diamond using (001)-oriented substrate. The authors demonstrated that these defects could be reduced by modifying substrate’s shape and orientations.

									Two type Ib HPHT-grown, pyramidal substrates, type A and type B, were used to grow single CVD crystals in this research. The {100} directions in type A substrate and {110} directions in type B were polished into inclined faces with 20°, 30°, and 40° angles. Both possessed a square top measuring 200 x 200 µm2. Crystals were grown on these substrates using plasma-assisted CVD technique with power density of 100 W/cm3 and methane concentration of 5% at 850°C, achieving a growth rate of 13 microns per hour.

									After removal of the substrate, the fully grown CVD crystals showed high transparency. Nitrogen-related defects were not detected. The inclined faces in type A substrate helped prevent twin sectors from reaching the top face. The growth rates of the lateral and top faces were 32.5 and 13.5 µm per hour, respectively. When thickness reached about 490 microns, the inclined faces started to disappear. The dislocations, originating from the square top of a pyramidal substrate, were observed in a crystal grown on type A substrate with 20° dislocations. However, these dislocations were diverted toward the edges rather than the top. Photoluminescence image showed that the inclined faces effectively diverted the direction of threading dislocations from {100} to {110} direction. Absence of sharp edges in these pyramidal substrates also helped in reducing dislocations. The lateral surfaces had the highest growth rate and possessed “fish scale” morphology in type A grown crystals, a morphology not observed in type B crystals. A maximum thickness of 2.2 mm could be achieved with a dislocation of 40° on type B substrate. A crystal 1.70 mm thick containing very low defects was achieved using type B substrate with 20° or 30° dislocations.

Abstracted by Kyaw Soe Moe @chapter:15


Publication Year: 2017 Title: “Sango Pearl” from Japan Abstract: Figure 1. Sango pearls (left and center) and a coral bead nucleus (right), each approximately 6 mm in diameter. Photo by Y. Katsurada.

A type of pink Japanese akoya cultured pearl, introduced about a decade ago and known as “Sango” pearl (figure 1), uses a pink coral nucleus and a Pinctada fucata mollusk. It is produced by Matsumoto Pearls, a Japanese pearl farming company based in Uwajima, Ehime Prefecture. Sango is the Japanese word for coral, and the species of pink coral used as the nucleus is likely a Corallium species, one of the precious corals harvested off the Pacific coast of Japan, especially around southern Kochi Prefecture (N. Iwasaki et al., “Biology of Japanese Corallium and Paracorallium,” Proceedings of the First International Workshop on Corallium Science, Management, and Trade, 2009, pp. 68–70). Matsumoto Pearls has successfully combined two beautiful organic gem materials to produce these attractive pink-colored pearls.

The coral nuclei in this study exhibited a pinkish orange color and measured 5.60–5.90 mm in diameter. Under microscopic examination, white layer-like structures and banding as well as polyp-related cavities have sometimes been observed. The nuclei also exhibit a weak whitish and stronger whitish fluorescence under short-wave and long-wave UV, respectively. The coral bead’s Raman spectrum (figure 2, top) shows strong pigment peaks at 1129 and 1517 cm–1 and calcite peaks (e.g., 280 and 713 cm–1), identifying them as Corallium species, as in S. Karampelas et al. (“Identification of the endangered pink-to-red Stylaster corals by Raman spectroscopy,” Spring 2009 G&G, pp. 48–52). The full-range photoluminescence spectra closely match that of natural pink coral with natural pigment-related peaks, similar to those in C.P. Smith et al. (“Pink-to-red coral: A guide to determining origin of color,” Spring 2007 G&G, pp. 4–15). Visible-range reflectance spectra (figure 2, middle) reveal peaks at 468, 482, 590, and 666 nm, like those observed in the spectra of natural coral by C.P. Smith et al. (2007). Ten partially drilled Sango pearls examined for this note were of a similar size (5.60–6.00 mm) as the coral beads used as nuclei. No color concentrations were noted down the drill holes or anywhere on their nacreous surfaces using a loupe or microscope. The nacre thickness measured between 120 and 400 microns (0.12–0.40 mm) under the microscope using a small table gauge. The different nacre thicknesses were also visible in real-time X-ray (RTX) images (figure 3). The pearls exhibited excellent luster, with almost no overtone and very weak orient, and showed a weak yellow to greenish yellow fluorescence under long-wave and short-wave UV radiation, respectively. These observations indicated that the 10 samples’ pink coloration was natural, though it remained to be seen whether the pink color originated from the pearls’ nacre or the underlying coral beads.

Figure 2. Top: Raman spectra of a coral bead (black trace) and a Sango cultured
pearl (pink trace) with pigment-related peaks at 1129 and 1517 cm–1. The bead’s
peaks are stronger at those wavelengths. Middle: Visible-NIR spectra of a coral
bead (black trace) and two Sango cultured pearls showing the different reflectance
values obtained. The dark pink trace represents thinner nacre (120 μm thick); the
light pink trace is from nacre that is 400 μm thick. Bottom: Plot of the relationship
between nacre thickness and the differential reflectance of Sango pearls at 482 nm
based on the average reflectance of the coral beads (differential reflectance =
RSango pearls – Rcoral beads).

Figure 3. RTX images of Sango cultured pearls showing clear demarcations between the larger coral bead nucleus and thinner nacre overgrowth. The pearl on the left has a thinner nacre than the one on the right.
Chemical analysis using an energy-dispersive X-ray fluorescence (EDXRF) spectrometer revealed manganese levels of 0 to 28 ppmw and strontium levels of 1077 to 1719 ppmw, indicating that the pearls formed in a saltwater environment. A useful observation was that pearl color seemed to be related to nacre thicknesses: Thin nacre overgrowth produced a more obvious pink tint, while thicker nacre resulted in a less saturated pink. Likewise, the Raman and visible-range reflectance spectra were also related to the nacre thickness. Raman spectra for pearls with thin nacre showed stronger pigment peaks at approximately 1129 and 1517 cm–1, similar in strength to those noted in the coral beads; only the aragonite-related peaks—and no pigment peaks—were noted in pearls with thicker nacre (see figure 2, top). The visible-range spectra of the pearls possessing thin nacre also matched the coral beads more closely, albeit with a lower reflectance (figure 2, middle), while pearls with thicker nacre had higher reflectance, as would be expected for lighter-colored pearls. By correlating the coral pigments with the maximum visible reflectance spectrum at 482 nm, the point of least reflectance (see figure 2, bottom), the relationship between nacre thickness and the visible spectra of the pearls could be gauged. The intensity at 482 nm indicates that the pink color of Sango pearls most likely originates from their coral nuclei.

While Sango pearls are not the first cultured pearls to use atypical bead nuclei in the form of other gem materials (see K. Scarratt et al., “Atypical ‘beading’ in the production of cultured pearls from Australian Pinctada maxima,” GIA Research News, 2017, https://www.gia.edu/gia-news-research/atypical-beading-production-cultured-pearls-australianpinctada-maxima), this is the first time the author has analyzed the detailed color origin of Sango pearls with Pinctada fucata mollusks as the host. The pearls are known to possess relatively thin nacre overgrowth, which has enabled the creation of the commercial type of akoya cultured pearl using a natural coral nucleus. GIA would classify Sango pearls as atypical bead-cultured pearls. @chapter:14


Publication Year: - Title: Diamond Research Gives Clues to the Formation of the Continents Abstract: This rough type Ib diamond, from Zimmi in West Africa, near the Sierra Leone-Libera border, contains a sulphide inclusion with compositions that give clues to how the West African continent formed. Photo by Karen Smit/GIA.

This is a summary of the article "Sulfur Isotopes in Diamonds Reveal Differences in Continent Construction" by Karen V. Smit, Steven B. Shirey, Erik H. Hauri and Richard A. Stern published on April 26, 2019, in Science.
Diamonds, one of the most valuable gemstones, are also very valuable to geoscientists. Mineral inclusions in diamonds are the most direct samples we have from the inaccessible depths of Earth. Inclusions in diamonds have given geoscientists information about water in the earth’s interior, mineralogy of the deep earth and metallic phases in the deep earth. Also, because there is no direct way to determine a diamond’s age from the diamond itself, mineral inclusions trapped within diamonds provide the only way to date diamonds. So, although inclusions in diamonds are often considered to be undesirable in the gem trade, they are extremely valuable scientific samples.
In our study, we measured the sulphur and rhenium-osmium isotopes in sulphide inclusions in diamonds from the Zimmi region of Sierra Leone. The sulphides are tiny minerals, often between 100 and 300 microns across, trapped in the diamonds during growth.
We found that the sulphides recorded two episodes of subduction in the West African continent. Subduction is when the oceanic crust is thrust under another tectonic plate during collision into the deep earth. The first subduction event recorded by Zimmi sulphides occurred around three billion years ago and the second was around 650 million years ago.

Sulphide inclusions still trapped in the Zimmi diamonds. Sulphides are silver-grey in appearance and are surrounded by blackened fracture systems. These fractures develop during kimberlite ascent because the sulphides expand more than the diamond. Photo by Karen Smit/GIA
3 billion-year-old subduction
The sulphides have isotopic compositions that indicate the sulphur was cycled through the ancient atmosphere prior to the rise of oxygen 2.5 – 2.3 billion years ago (Farquhar et al., 2001). This is indicated by mass-independently fractionated (MIF) sulphur isotopes. Any modern sulphur (or sulphur that did not cycle through the ancient atmosphere) will not have these MIF isotopes1. The presence of MIF sulphur in these sulphide inclusions indicates that they have a surficial origin in the earth’s ancient atmosphere. The sulphides were likely emplaced into the deep earth around 3 billion years ago – a time that has been well established for subduction and incorporation of oceanic crust material into the mantle2,3.
650 million-year-old subduction
We also measured the rhenium-osmium isotopes in these sulphide inclusions. Rhenium-osmium is the most widely used technique to date the time of diamond formation4. Zimmi diamonds were found to have 650-million-year-old ages5, an age that overlaps with subduction and collisional mountain building in the region, between 700 and 550 million years ago. Subduction of oceanic crust and subsequent dehydration of the oceanic crust would have introduced carbon-bearing fluids into the deep earth for diamond formation6.
Why do we find this interesting?
Earth’s oldest continents (called cratons) are stabilized by lithospheric mantle keels. The stability of Earth’s continents in the face of destructive tectonic activity is an essential geologic backdrop for the emergence of life on our planet. Since this is the only tectonically active, rocky planet that we know, understanding the geology of how our continents formed is a crucial part of discerning what makes Earth habitable.
The stability of cratons depends on the underlying mantle keels that are around 150 – 200 km thick. The processes for how these mantle keels form are still debated, and there are several different theories for their origin. Some of the models for craton formation involve subduction-style plate tectonics where plates are subducted into the deep earth and stabilize the cratonic keels. Other models do not invoke subduction, and instead, require deeper mantle processes like melting in mantle plumes or melting at oceanic plateaus.
Luckily these mantle keels have the ideal conditions for diamond formation. The majority of natural diamonds form in these cratonic mantle keels. Diamonds become important samples that can be used to investigate how the stabilizing keels below the oldest continents are formed.
Sulfur isotopes in diamonds, combined with their Re-Os ages, can be used to track multiple subduction events during craton growth, even those separated by billions of years. Subduction processes were essential to the growth and modification of the West African craton over a period of 2 billion years.
We compared our results to diamonds from southern Africa and northern Canada. We found that this combined isotopic approach also reveals differences in craton construction worldwide. Similar to the Zimmi diamonds, diamonds from the Jwaneng and Orapa mines in southern Africa do contain MIF sulfur1,7. This indicates that subduction was also an important process in the construction of the cratonic mantle in southern Africa.
But diamonds mined in northern Canada do not show the same sulphur chemistry. Diamonds from the Ekati mine have 3.5-billion-year-old rhenium-osmium ages and do not have MIF sulphur8,9. This means that the mantle keel in this region originated in some way that did not incorporate surface material. The sulphur in the Canadian diamonds does not tell us how the mantle keel formed, only how it did not.
Our work shows that sulphide inclusions in diamonds are a powerful tool to investigate craton construction processes.

Sulphide inclusion that has been broken out of a diamond and imaged in a scanning electron microscope. This sulphide has cubo-octahedral morphology and trigons on its surface. Both these features were imposed on the sulphide by the diamond. Image by Karen Smit/GIA

How did we do this?
To characterize the diamonds and image the inclusions, we first laser cut and polished double-sided plates of the diamonds.
Rhenium-osmium isotopes
We broke the diamond plates using a small hammer and a steel cracker to release the sulphide inclusions. The inclusions are tiny and weighed between 3 and 162 micrograms. After breaking each inclusion out of the diamond, we imaged it and analyzed its major element composition using a scanning electron microscope.
In a clean laboratory, we then dissolved the sulphide in some acid along with a known amount of tracer solution known as an isotopic spike. Chemical procedures are done to separate rhenium and osmium into different acidic solutions. The solutions that contain rhenium and osmium are each dried down on a hotplate.
The dried-down salt of osmium is placed on a metallic filament, which is then placed in a thermal ionization mass spectrometer (TIMS). The filament is heated to produce ions that are then accelerated through the instrument and the different osmium isotopes are measured on a very sensitive detector.
The dried-down salt of rhenium was taken up into a dilute acid solution. That solution was introduced into a multi-collector inductively coupled mass spectrometer (MC-ICP-MS). The solution was ionized in a plasma and those ions were accelerated through the instrument, where the two different rhenium isotopes were measured simultaneously on very sensitive detectors.
The amount of rhenium and osmium that we measured in the sulphides is in the femtogram to picogram range - where 1 femtogram is 10-15 g or 1 part per quadrillion (ppq) and 1 picogram is 10-12 g or 1 part per trillion (ppt). Because we are measuring such tiny amounts, any small amount of contamination can ruin the sample. This is why it is essential to do this work in a clean laboratory with dedicated supplies for diamond inclusion work.
Rhenium-osmium analyses were done using chemistry labs and a Thermo-Fisher Triton instrument at the Department of Terrestrial Magnetism at the Carnegie Institution for Science.
Sulphur isotopes
Sulphide inclusions were not broken out of the diamonds for sulphur isotope measurements. Instead, we polished the diamond plates down further with a diamond scaife to expose the sulphide inclusions. It took a few hours to a day to expose each inclusion.
Diamond plates with the exposed sulphide inclusions were placed in a secondary ion mass spectrometer (SIMS). The samples were bombarded with a cesium ion beam to create small pits in the sulphides. The material released from the sulphides was then accelerated through the instrument and the four different sulphur isotopes were measured simultaneously on very sensitive detectors.
Sulphur isotope measurements were done using a Cameca IMS 1280 instrument at the University of Alberta. Preliminary measurements were done using a Cameca NanoSIMS at the Department of Terrestrial Magnetism at the Carnegie Institution for Science.
About the diamonds themselves
Diamonds for this study are from the Zimmi alluvial deposit in Sierra Leone. The Zimmi mining area is located south of the town Zimmi, near the Libera-Sierra Leone border. The Zimmi locality is known for producing yellow diamonds with abundant sulphide inclusions.
The Zimmi diamonds have nitrogen impurities in the rare isolated form that classifies them as Type Ib diamonds. Type Ib diamonds are exceptionally rare among natural diamonds and account for less than 0.1% of worldwide natural diamonds.
The Authors
Karen V. Smit has been a research scientist at the Gemological Institute of America (GIA) since 2014. She is interested in using diamonds and their mantle host rocks to understand diamond formation processes in the deep earth. Her research focuses on the origin of the earth’s continents, how plate tectonic processes influence diamond stability, and most recently in using the spectroscopic features of natural diamonds to distinguish them from lab-grown and treated diamonds.
Steven B. Shirey has been a staff member at the Department of Terrestrial Magnetism of the Carnegie Institution for Science for 34 years. Shirey's research focuses on the evolution of Earth's continents, especially as a function of mantle evolution. His interest in diamonds began more than 20 years ago as a way to examine continent formation and plate tectonics from the deepest possible perspective in the mantle.
Erik H. Hauri (now deceased) was a staff member at the Department of Terrestrial Magnetism of the Carnegie Institution for Science for 24 years. He passed away in 2018. Hauri was interested in the geochemical cycles of volatiles on the earth and moon and their relationship to planetary dynamics. Hauri's remarkable expertise in secondary ion mass spectrometry led to breakthroughs in understanding the water content of the moon, and the analysis of stable isotopes in diamonds and their mineral inclusions.
Richard A. Stern is a research scientist and ion probe facility manager at the University of Alberta. His research over the last 25 years has focused on developments and applications of secondary ion mass spectrometry to a broad range of topics in geochemistry and geochronology, most recently emphasizing light stable isotopes.

References
1. Farquhar et al., 2002
https://science.sciencemag.org/content/298/5602/2369

2. Barth et al., 2002
https://www.sciencedirect.com/science/article/pii/S0301926802001110

3. Aulbach et al., 2019
https://academic.oup.com/petrology/advance-article-abstract/doi/10.1093/petrology/egz011/5364029

4. Pearson et al., 1998
https://www.sciencedirect.com/science/article/pii/S0012821X98000922

5. Smit et al., 2016
https://www.sciencedirect.com/science/article/pii/S0301926816300882

6. Smit et al., 2019
https://www.sciencedirect.com/science/article/abs/pii/S0009254119301895

7. Thomassot et al., 2009
https://www.sciencedirect.com/science/article/pii/S0012821X09001447?via%3Dihub

8. Westerlund et al., 2006
https://link.springer.com/article/10.1007%2Fs00410-006-0101-8

9. Cartigny et al., 2009
https://www.sciencedirect.com/science/article/pii/S0024493709002497?via%3Dihub @chapter:29


Publication Year: - Title: Rubies Reportedly from the Niassa Region of Mozambique Abstract: Attractive new rubies reportedly from northern Mozambique have begun to appear on the Thai gem market. The stones resemble rubies from Winza, Tanzania, but this study shows they can be distinguished by microscopic examination. Download PDF to view. @chapter:3


Publication Year: 2018 Title: A Cat’s-Eye Rock Consisting of Jadeite and Amphibole Abstract: Figure 1. This 1.42 ct translucent variegated green bead displays a distinct chatoyant band on the darker green side (left). No chatoyancy was observed on the lighter green side (right). Photos by Tony Leung.
The Hong Kong laboratory recently examined a translucent variegated green bead exhibiting chatoyancy (figure 1). The 1.42 ct bead, measuring approximately 5.62 mm in diameter, displayed two different shades of green on opposite sides. A distinct cat’s-eye band was readily visible across the darker green region with fiber-optic illumination, whereas no chatoyancy was observed in the lighter green region on the reverse side.

Figure 2. Left: Parallel fibrous amphibole crystals were the cause of chatoyancy in this green bead; field of view 11.34 mm. Right: Tight interlocking grains were visible in the lighter green jadeite region; field of view 3.80 mm. Both observed with fiber-optic illumination. Photomicrographs by Bona Hiu Yan Chow.
Microscopic observation revealed that the darker green side consisted of parallel fibrous crystals (figure 2, left). Light reflecting off these oriented crystals produced a chatoyant band perpendicular to the length of the crystals. On the lighter green side, tight interlocking grains were observed (figure 2, right). Raman spectroscopy detected the presence of richterite, an amphibole with the general formula Na2CaMg5Si8O22(OH)2, in the darker green region and jadeite in the lighter green region.
While it is not unusual to encounter a rock consisting of jadeite and amphibole (G. Shi, “Mineralogy of jadeitite and related rocks from Myanmar: a review with new data,” European Journal of Mineralogy, Vol. 24, No. 2, 2012, pp. 345–370), it is fascinating to see such a rock being fashioned into an attractive variegated green bead exhibiting chatoyancy. @chapter:5


Publication Year: 1990 Title: Diagnostic Features and Heat Treatment of Kashmir Sapphires Abstract: The locality origin of natural-color blue sapphires from Kashmir can, in many cases, be positively identified. However, the field of origin determination is a very complex one – especially with the now common practice of heat treatment. Today, only by combining different gemological tests with years of practical experience, can a conclusive determination of the origin of a sapphire be made. For all practical purposes, examination of inclusions in conjunction with optical spectrophotometry remain the most important tests. @chapter:19


Publication Year: 2022 Title: Social Media Success for Black Opal Direct Abstract: Figure 1. Black Opal Direct’s YouTube channel helped dramatically increase sales during the last two years.
At the GJX show, Justin Thomas (New South Wales, Australia) told us about Black Opal Direct’s success on social media during the pandemic, his efforts to share opal knowledge, and a black opal with a special story. Founded in 1961 by Thomas’s father, Jurgen, and owned and operated by Thomas and his wife, Ruth, Black Opal Direct specializes in black opal from Lightning Ridge.
Thomas said most of their customers come from YouTube and Instagram. In the last three years, their YouTube subscriber count has increased from 30,000 to 170,000. He said views fluctuate between 500,000 and 3 million a month, averaging about a million. This led to a tripling of sales over the last two years, though their business has now returned to normal. “It was a dream run,” Thomas said. “I believe those days are over.” He acknowledged that they have been fortunate in a time when many businesses around the world failed due to the pandemic. Without YouTube, he said, they would have weathered the last two years but would not be doing nearly as well.
Black Opal Direct began selling on eBay more than a decade ago. They determined that a million people per month were searching the Internet for the word “opal.” Within a few months of starting to sell rough on eBay, sales were strong; then they built their website and brought their eBay customers to it. Thomas created a YouTube channel (figure 1) around the same time as the eBay store, but it was only three years ago that he started posting videos more frequently.
“As the channel grew, it started to morph into more entertainment videos, showing them how fun it is to cut an opal, and my funny side, so they can see my personality,” he said. “I think in social media you have to show a lot more and a little bit of vulnerability. If you can connect in that way, in the heartstrings way, people will trust you a lot more and are much more likely to buy from you.”
Thomas believes his videos are helping the whole industry because he does not push sales. “I don’t even give the link to my website very often,” he said. “It’s all about the love of opal, how to cut it, how to mine it. It also helps the world understand opal.”
According to Thomas, the opal industry is very secretive, and he is probably the first person to share so openly through social media how to cut opal. He said many had thanked him at the show, saying they learned how to cut opal from his videos and in some cases quit their jobs to go into the opal business. “I think it’s awesome to be able to share that abundance,” he said.
Thomas learned to cut opal from his father, who moved to Australia from East Germany in the ‘60s and began mining in Lightning Ridge. Jurgen Thomas’s tools included a pick, shovel, and candle. When he began cutting, he used a manual Singer sewing machine that he converted by adding a corundum grinding wheel. “He’s passed away now, and all that knowledge is only with me,” Justin Thomas said. Despite the positive response of those learning from his videos, he said, many cutters are unhappy because he’s giving away prized secrets. “That knowledge—if that’s gone with my dad, and it goes with me, and my son never takes it up, it’s wasted,” he said. “Why let it go?”
Thomas emphasizes the quality of social media followers over the number. “Even if you’ve got a hundred followers, they could be a hundred genuine followers because they genuinely like you,” he said. “Say up to five percent of those people may buy. You grow from that.”
When Thomas cuts a highly valuable opal from rough on camera, he often does a dance. “They love it,” he said. “There’s always a comment before they watch a video: ‘I hope this one gets a dance!’” He has also been testing TikTok. “I always make jokes so they can see that I’m human, I’m personable, I can make an idiot of myself. I thought TikTok could be a good place for me to concentrate on those parts of my videos. I had a lot of followers quickly, who want to see me dancing.”
Some competitors have tried to copy him—unsuccessfully, according to Thomas, because “their heart’s not in it.” Some also criticize his style. “I get lots of people saying ‘You’re an idiot’ or ‘You’re a clown’ or ‘Why are you dancing?’ Water off a duck’s back. I try to focus on all the people that love me.”
After years of working out of their home, the Thomases recently purchased a warehouse and built a cutting workshop there. Thomas said their subscribers have loved watching the small business grow. “I love this industry so much and I love what I do so much that it’s addictive,” he said. “Giving more and more to the subscribers and to my followers, going to the next level. So watch this space.”
Thomas showed us a 10.65 ct black opal (figure 2), which he calls “the ultimate black opal.” Its vivid colors, patterns, and strong play-of-color make it extraordinary. One of his father’s friends, who mined with him at Lightning Ridge in the ‘60s, brought it to Thomas two years ago after finding it almost directly under the shed his father lived in back then.

Figure 2. A 10.65 ct black opal found in Lightning Ridge by one of Jurgen Thomas’s friends, at a location almost directly under where Jurgen lived nearly 60 years ago. Shown in diffused (left) and direct (right) lighting. Photos by Robert Weldon; courtesy of Black Opal Direct. @chapter:33


Publication Year: 2021 Title: Amphibole Mineral Inclusions in Mozambique Ruby Abstract: Figure 1. Densely distributed amphibole inclusions in ruby. Photomicrograph by Kazuko Saruwatari; field of view 9.40 mm.
Amphibole, a mineral supergroup with a diverse chemical composition of the general formula AB2C5T8O22W2, where A =  (vacancy), Na+, K+, Ca2+, Pb2+, Li+; B = Na+, Ca2+, Mn2+, Fe2+, Mg2+, Li+; C = Mg2+, Fe2+, Mn2+, Al3+, Fe3+, Mn3+, Cr3+, Ti4+, Li+; T = Si4+, Al3+, Ti4+, Be2+; and W = OH−, O2−, F−, Cl−, is a collectors’ item as a loose stone; its members are known as constituent minerals of nephrite (X. Feng et al., “Characterization of Mg and Fe contents in nephrite using Raman spectroscopy,” Summer 2017 G&G, pp. 204–212).

Figure 2. Rounded anhedral amphibole crystals. Photomicrograph by Masumi Saito; field of view 3.25 mm.
In addition, amphibole appears as crystal inclusions in both ruby and sapphire reported from Mozambique and Kashmir (e.g., Winter 2018 Lab Notes, pp. 435–436). Recently, the GIA lab in Tokyo received a Mozambique ruby densely included with rounded anhedral crystals (figures 1 and 2).

Figure 3. The Raman spectrum of the amphibole mineral inclusions (blue) and the reference spectrum of pargasite from the RRUFF database (R060072).
The Raman pattern of the surface-reaching crystals most closely matched the RRUFF reference spectrum (no. 060072) of the calcic amphibole pargasite (figure 3). The Raman peak at 669 cm–1 corresponded to the symmetric stretching vibration of T elements, which are tetrahedral ring structures composed mainly of the Si-Ob-Si linkage (Ob = bridging oxygen) and often used to fingerprint various amphibole species (N. Waeselmann et al., “Nondestructive determination of the amphibole crystal‐chemical formulae by Raman spectroscopy: One step closer,” Journal of Raman Spectroscopy, Vol. 51, No. 9, 2020, pp. 1530–1548).

Figure 4. The FTIR spectrum of the Mozambique ruby, indicating the amphibole-related peaks between 3600 and 3800 cm–1. The 3309 cm–1 peak is associated with corundum.
The FTIR pattern showed some peaks between 3600 and 3800 cm–1 in the principal OH-stretching region of octahedral metal components, which are C cations in the general formula of amphibole (figure 4). The FTIR pattern showed a peak at 3643 cm–1 in addition to peaks at 3671 and 3704 cm–1, suggesting the possibility that other elements such as Fe occupied those sites typical of pargasite in some portions (e.g., M.C. Day et al., “Gem amphiboles from Mogok, Myanmar: Crystal-structure refinement, infrared spectroscopy and short-range order–disorder in gem pargasite and fluoro-pargasite,” Mineralogical Magazine, Vol. 83, No. 3, 2019, pp. 361–371). The FTIR spectra of corundum between 2000 and 5000 cm–1 were very useful for the identification of mineral inclusions in corundum. This is the first known report of an FTIR pattern identifying amphibole mineral inclusions in corundum. @chapter:5


Publication Year: 2019 Title: Large Laboratory-Grown Star Ruby and Sapphire Abstract: Figure 1. A 4,759 ct synthetic star ruby and a 467.2 ct synthetic star sapphire were submitted to GIA’s Tokyo lab. Photo by Shunsuke Nagai.

The Tokyo lab received for a Quality Assurance report two unusually large loose stones with asterism. One was a 4,759 ct red sphere (figure 1, left) with a diameter of approximately 76.96 mm, and the other a 467.2 ct blue cabochon measuring approximately 52.04 × 42.29 × 20.89 mm (figure 1, right).

Figure 2. Asterism seen on the surface and irregular grain boundaries (Plato striations). Photomicrograph by Masumi Saito; field of view 11.4 mm.
These stones both had a spot refractive index of 1.77 and were doubly refractive with a uniaxial interference figure. The red sphere displayed a ruby spectrum with a handheld spectroscope. Microscopic observation showed curved bands of gas bubbles, cottony structure on the surface, and Plato striations (figure 2), providing proof of a laboratory-grown star ruby. The cottony structure indicates the possibility of diffusion treatment. The blue cabochon displayed a faint blue sapphire spectrum with the handheld spectroscope. It had a mottled blue color in diffused light (figure 3). Apparently it was a titanium-diffused colorless synthetic sapphire polished to produce asterism. As a result of polishing, the blue color is concentrated on the flat bottom and mottled on the curved top. This is visible when viewed from the side. Microscopic observation showed curved bands of gas bubbles, proof of laboratory growth.

Figure 3. Mottled blue patterns were observed in the synthetic sapphire against transmitted illumination through a diffuser plate. Photo by Shunsuke Nagai.
As Schmetzer et al. summarized (“Dual-color double stars in ruby, sapphire, and quartz: Cause and historical account,” Summer 2015 G&G, pp. 112–143), the Czochralski pulling technique can produce large crystals. These crystals have a uniform distribution of color and titanium-bearing precipitates compared to other growth methods, and they can be cut from any part of the crystal, regardless of size. Therefore, this laboratory-grown star ruby was most likely produced by the pulling technique. Also, this specimen was too large to have been produced by flame fusion. Detailed information on these two items is not available, but they are probably similar products.
Synthetic star corundum is not rare, but these were among the largest laboratory-grown star rubies and star sapphires submitted to the GIA laboratory. @chapter:12


Publication Year: 2015 Title: Moldavites: Natural Or Fake? Abstract: Figure 1. Glass in a silver brooch, hallmark from 1866. Private collection, photo by Jaroslav Hyršl.

              Tectites are members of a large group of impact glasses, formed by the collision of a meteorite on the Earth’s surface and the subsequent melting of surrounding rocks. The most famous tectites used as gemstones are moldavites from southern Bohemia in the Czech Republic. These were formed by a meteorite’s impact in the Ries crater in southern Germany 14.7 million years ago, about 500 km from their occurrence (V. Bouška, Moldavites: The Czech Tektites, Stylizace, Prague, 1994). Moldavites are popular for their pleasant green color, enigmatic origin, and interesting etched texture. They are used in jewelry, in either faceted or natural form. The price of moldavite has risen in the last few years, and as a logical consequence imitations have become more widespread.

In fact, moldavite imitations are nothing new. Faceted moldavites were very popular in Czech jewelry during the second half of the 19th century, often with Czech garnets (chrome pyropes) or small river pearls. Their use diminished in the beginning of the 20th century when imitations made from green bottle glass began to appear. Nevertheless, the author’s recent study of five moldavite sets (bracelet, brooch, and earrings) from the second half of the 19th century in the collection of the Museum of Decorative Arts in Prague revealed an unexpected result. Only one set contained moldavites—a donation to the museum by Olga Havlova, the first wife of Vaclav Havel, the late Czech author and statesman. All of the stones in the other four sets proved to be glass imitations. This means that glass imitations have been around decades longer than previously thought (figure 1).

Fortunately, the identification of faceted moldavite is simple. Besides their flow texture and abundant bubbles (almost always much more abundant than in an artificial glass), moldavites contain “wires” of lechatelierite, a high-temperature form of SiO2. Lechatelierite is very easy to see with a loupe due to its lower RI.

Figure 2. Two moldavites from southern Bohemia, Czech Republic (top row) and two recent imitations from China (bottom row). The natural specimen on the top right measures 44 mm across. Photo by Jaroslav Hyršl.

Figure 3. One of two huge moldavite fakes seen in Hanoi. Photo by Jaroslav Hyršl.
The identification of moldavite with a natural-looking surface is much more difficult. Rumors of moldavite imitations from China have been circulating among Czech dealers for many years, but only recently has the author been able to study some examples (see figure 2). Two large moldavite imitations were seen in a high-end jewelry shop in Hanoi during the 2013 International Gemmological Conference (figure 3). Their size was astonishing, because very few real moldavites weigh more than 100 g. Their shape was also too perfect, making them easy to recognize.

Figure 4. Typical bubbles and inclusions of lechatelierite in natural moldavite; image width 5 mm. Photomicrograph by Jaroslav Hyršl.
Chinese producers are now manufacturing small stones weighing just a few grams that are very realistic. The surface feature of natural moldavite is caused by natural etching, and an almost identical feature can be created artificially, likely in hydrofluoric acid. If the stone in question has a polished surface, the presence or lack of lechatelierite “wires” (figure 4, top and bottom) is the best diagnostic tool, along with refractive index (table 1). For rough, immersion in water or especially oil with a similar RI is very helpful to reveal lechatelierite. Imitation moldavite also has a different density, UV-Vis absorption spectrum (figure 5), and fluorescence (again, see table 1). The color of natural moldavites is caused by very low concentration of iron; all other tectites are more Fe-rich and therefore black. Fluorescence is particularly helpful because it may be used on large mixed lots. Some imitations are not fluorescent, however. One imitation seen by the author several years ago was not fluorescent, but its very high specific gravity of 3.60 immediately ruled out natural moldavite.

TABLE 1. Characteristics of natural and imitation moldavite.

				Moldavite

				Chinese imitations

				19th-century glass imitations

				Color

				Light green to brown

				Light green

				Light green

				RI

				1.490 (1.480–1.510)

				1.520

				1.545–1.580

				Density

				2.35 (2.27–2.46)

				2.52–2.53

				n.a.

				Fluorescence

				Inert in UV

				Chalky in short-wave UV

				Inert in UV

				Absorption spectrum

				Minimum at 550 nm

				Maxima at 460 and 640

				n.a.

Figure 5. Absorption spectra of natural moldavite (black and red lines) and imitations (green and blue lines). @chapter:2


Publication Year: 2023 Title: Italian Precious Coral Abstract: Mediterranean coral from different regions. Left: Dark red fine coral from the northern coast of Sardinia. Center two pieces: “Classic” coral from the southern coast of Sardinia. Right: Orangy coral, termed “Sciacca,” from the coast of southern Sicily. Photo by Lisa Kennedy; courtesy of Fulvio Di Gennaro Srl.
Coral from the Mediterranean Sea has been harvested and used for adornments for thousands of years. More than 7,000 species are categorized as precious, common, or reef coral. Precious coral is defined by the World Jewellery Confederation (CIBJO) Coral Commission as “those that are used in jewelry and decoration, specifically red, pink, and white varieties with porcelain-like luster after polishing.” Italian coral harvested from the Corallium rubrum species is considered precious.
At the GJX show, the authors spoke with Sergio Di Gennaro of Fulvio Di Gennaro Srl. (Torre del Greco, Naples) about the Italian coral market. The Mediterranean has been precious coral’s major source since it was first collected for ornamentation over 3,000 years ago, followed by Taiwan and Japan with smaller quantities. Beginning in the late 1970s, Mediterranean coral was threatened by overharvesting. Di Gennaro explained that many strict regulations for harvesting coral are in place today. Harvesting is limited to coral with trunks having a basal diameter of at least 7 mm recovered from 50 meters or deeper by licensed scuba divers.
Precious coral is the exoskeleton of very tiny marine invertebrates, known as coral polyps. When a colony of polyps arrives in a particular area, they start to create the exoskeletons on rocks, growing upward in a branch-like or fan formation. Di Gennaro mentioned that divers do not harvest coral with active colonies as these will continue to grow and the future, larger coral will be more valuable. Divers therefore tend to harvest the coral where the colony has already left. Unlike other types of corals, such as common and reef, these Mediterranean “deep sea” precious corals are not a natural habitat for other marine species. Reef coral species, which are a natural environment to many different marine species, are in many cases endangered and must be preserved.
Di Gennaro explained that the quality of the coral depends on the locality. He showed us a piece of dark red coral (see above, left), which is the typical color of coral harvested from northern Sardinia. It is a darker red due to cooler water temperatures from strong currents in the area. Coral from the southern portion of Sardinia (see above, center) tends to be lighter in color. Di Gennaro described this as a more “classic” color of Mediterranean coral. He also showed us a piece of reddish orange coral called “Sciacca,” named for a town in southern Sicily where the coral is harvested (see above, right). Di Gennaro said that volcanic activity below the surface results in warmer water temperatures, which in turn causes a more orangy color.
Di Gennaro emphasized the importance of sustainability in the coral industry, noting the heritage of the city of Torre del Greco, which was built on the art of processing coral. While current restrictions have reduced the amount of coral being harvested compared to decades past, sustainable production will guarantee that we continue to see stunning Mediterranean precious coral for decades to come. @chapter:40


Publication Year: - Title: Dreamy Drusy: Minute Crystals Shimmer in Dramatic Designs Abstract: This cobaltoan calcite drusy (a pink to purple cobalt-bearing calcite) has been cut into a heart-shape pendant and is accented with a swirl of 18K gold. Courtesy of Kara Ross. Photo by Orasa Weldon/ GIA

Drusy (also spelled druzy) jewelry has surged in popularity in recent years. Celebrities wear it on the red carpet and designers clamor for it at gem shows.

Drusy refers to clusters of small crystals that sparkle like snow or sugar coatings on the minute crystals of rock surfaces. These unique and glistening gems sparkle in bright light and appeal to those who like a natural or boho style of jewelry – and judging by the lively interest and brisk trading for it at the recent gem shows at Tucson in February, the interest continues. Designers clamored for naturally sparkling gems, along with those treated to be even brighter and more colorful, for fresh, new jewelry looks.

In nature, the most plentiful and durable drusies are found in quartz, or in the cryptocrystalline varieties of agate and chalcedony. Quartz has long been a favorite of gem carvers, and contemporary designers and cutters have discovered the intrigue and challenge of working with material that contains these minute crystals. The outcome is often stunning: designers have won national awards with gold and platinum jewelry that feature them.

The surface of this black onyx carved pendant sparkles with natural drusy crystals and is carved by Glenn Lehrer. Courtesy of Rebecca Young Buys. Photo by Orasa Weldon/GIA
Drusy is often cut in a free-flowing style that follows the shape of the material to preserve the mini crystals. Because of its delicate nature, it is best suited in jewelry as pendants, earrings, or brooches. It can be fashioned in rings and bracelets too, if they are designed with protective settings and care instructions are provided.

Quality is determined not only by color, weight and clarity, as in most colored gemstones, but also by evenness in size and coverage of the crystals on the matrix. Good quality drusy is especially rare in non-quartz species, such as garnet and calcite. The durability, or toughness, of the drusy is dependent on the nature of the crystals and the matrix in which they are embedded. For example, drusy on quartz and chalcedony are more durable than on calcite, which is more fragile.

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Colorful natural drusy materials are rare; pink is a rare and coveted color in the gem world. Natural pink cobaltoan calcite drusy material is trending with designers for its coveted combination of color, rarity and sparkle. It was first discovered on Elba Island, Livorno Province of Tuscany, Italy in 1910 and can also be found in other countries in Europe and in Africa.

Uvarovite, a natural garnet drusy, has the look of thousands of brilliant, tiny green crystals. This gemstone was discovered in the rugged Ural Mountains of Russia and is named after the Count Uvarov, who lived in the mid-1800s. Since there are no other known localities, this material is also rare.

Rainbow pyrite, the trade name for natural iridescent pyrite drusy, was first seen in the trade in the late 1990s and has been found in only one location in the world – along the banks of the Volga River in Russia. Rainbow pyrite is famed for its iridescence, caused by refraction and diffraction of light, and its metallic luster blends beautifully when set with all metals. Top quality material can shimmer in a spectrum of color, including gold, green, pink and blue. Rainbow pyrite also has a stunning array of bright golds, brassy coppers, blues, greens and rose hues, and has been said to resemble fancy color diamond melée.

This group of agate drusy shows a variety of possible coating effects. From left: silicone dioxide coating, black titanium coating, blue titanium coating and platinum coating. Courtesy of Rare Earth Mining Co. Photo by Robert Weldon/GIA
Rainbow colors and metallic sheen may occur naturally, but others colors are a result of gemstone treatment. Titanium drusy is created in spectacular iridescent shades of white and blue by a titanium coating process applied in a vacuum chamber. Electroplating, a process similar to rhodium application, gives drusy a fancier and brighter appearance than its natural counterpart. Colorful crystals are sometimes coated with a film of gold, platinum, sterling silver or titanium.

Although less frequent, drusy is also found in azurite, turquoise, demantoid garnet, melanite garnet, dolomite, sphalerite, dioptase and vanadinite.

No matter how it is featured, drusy is nature’s gift – and will inspire your design and fashion dreams. @chapter:24