Publication Year: - Title: Diamond Description Abstract: However gem quality diamonds are fashioned from the original crystal shape they possess a combination of brightness, sparkle, fire, and sense of purity not matched by other gems. - Jeff Scovil, courtesy Barker & Co.

                      Diamond’s characteristic chemical composition and crystal structure make it a unique member of the mineral kingdom.

Diamond is the only gem made of a single element: It is typically about 99.95 percent carbon. The other 0.05 percent can include one or more trace elements, which are atoms that aren’t part of the diamond’s essential chemistry. Some trace elements can influence its color or crystal shape.

	Whether fashioned or rough, and no matter what their shape, all diamonds have the same chemical composition and internal crystal structure.
The way a mineral forms helps determine its identity. Diamond forms under high temperature and pressure conditions that exist only within a specific depth range (about 100 miles) beneath the earth’s surface. Diamond’s crystal structure is isometric, which means the carbon atoms are bonded in essentially the same way in all directions. Another mineral, graphite, also contains only carbon, but its formation process and crystal structure are very different. The result is that graphite is so soft that you can write with it, while diamond is so hard that you can only scratch it with another diamond.

	The most common shape for rough gem quality diamond is the octahedron, which looks like two pyramids back to back. Crystals that are almost perfect in shape and transparency are called glassies.
Without any one of these factors, diamond might be just another mineral. Fortunately, though, this special combination of chemical composition, crystal structure, and formation process gives diamonds the qualities that make them extraordinary.

	This diamond is a D color grade and has exceptional chemical purity. - Courtesy Lazare Kaplan Diamonds
On almost all modern birthstone lists, diamond is recognized today as the birthstone for April. Diamond is also the gem that marks the 60th and 75th wedding anniversaries.

	Diamond’s unique optical and physical properties give it the highest possible luster of any transparent gemstone. This is called adamantine luster after the Greek word Adamas meaning diamond-like. - Courtesy Chow Tai Fook Jewellery Co. @chapter:35


Publication Year: 1994 Title: Summer 1994 Gem News International Abstract: Diamonds
            Argyle Upgrades Operation
            DeBeers's Rough Diamond Sales Up
            Diamond Pipes Located Outside Canada's "Corridor of Hope."
            More Evidence that Wisconsin Diamonds Come from Canadian Pipes
            Update on Ghana Production
            Russia Offers Rough for Sale
            Russia Develops Diamond-Cutting Equipment
            Production Plant Upgrade for Zimbabwe
            Near-Colorless Russian Synthetic Diamond Examined
Colored Stones
            Amber Marketed with Photomicrography
            Basel Fair Highlights
            Fluorite from California
            Gem Artistry Knows no Boundaries
            Green Gems from Australia
            Myanmar Liberalizes Gem Trading
            Freshwater Pearls from Bangladesh
            Tiger's-Eye Quartz Production Record in South Africa
            Cat's-Eye Sillimanite from Orissa, India
            "Wagon Wheel" Tanzanite
            Bicolored Topaz
            "Zebra" Stones from Australia
Enhancements
            New Emerald Treatment/Polishing Systems from Israel
Synthetics and Simulants
            New Emerald Imitation
            Kimberley Expands Product Line
            Minute "Machine-Cut" Synthetics
            Faceted Synthetic Opal
            Bright Yellow "Pulled" Synthetic Sapphires

To view the full section, download the PDF above @chapter:24


Publication Year: 2021 Title: Hole Drilled by Hand in Briolette Abstract: Figure 1. The diamond paper that held the 6.19 ct briolette diamond. Photo by Nathan Renfro.

Recently, a 6.19 ct briolette diamond was submitted to GIA’s Antwerp laboratory for examination. It had been in the family of Belgian diamond cleaver and Auschwitz survivor Philip Isidoor Frank, who died in 1982. Mr. Frank is known for his work on many important diamonds, such as the 69.42 ct D-color Internally Flawless pear-shaped Taylor-Burton diamond. The diamond paper containing the briolette had a note, presumably written by Mr. Frank: “drilled by hand about 400 years ago” (figure 1). Sadly, this cannot be substantiated, and Mr. Frank left no other record. It raises the question as to whether this age is theoretically possible.

Figure 2. The facet arrangement of the 6.19 ct briolette. The horizontal drill hole is at the top. Photo by Jian Xin (Jae) Liao.
The diamond (figure 2) loosely fits the briolette definition since the hole is at the very tip rather than through the central portion. In reference to Mr. Frank’s note on the diamond paper, this description seems appropriate, even though the stone lacks the appealing teardrop shape we think of with modern briolettes. The style of faceting for this diamond is reminiscent of early cutting from India (1550–1900), but it could have been cut at any time (figure 3). By the 1700s, Europeans were already moving toward variations of brilliant styles with good symmetry, thin girdles, and specific ratios of crown and pavilion. They did not typically care for the quality of Indian diamond cutting, and many stones were recut.

Figure 3. Early Indian cutting styles (ca. 1550–1900) feature a very thick girdle area with multiple facets, similar to the briolette’s plane that wraps around the stone. From Ogden (2018), p. 320.
The briolette cutting style has a remarkably long history. Seventeenth-century French gem merchant Jean Baptiste Tavernier (1676, p. 336) sold four briolettes to the French king Louis XIV. The invoice described two stones as “round pendant with little facets” and “cut with facets on all sides” (Bapst, 1889, p. 404), respectively, and included illustrations. Two others, not illustrated, were “cut as round pendants with facets on all sides.” Tavernier’s drawings depict a briolette style, although that term was not used much before the nineteenth century.

However, Tavernier’s gems are not the earliest recorded briolettes. One had arrived in the royal court in England almost 20 years before his first voyage to India. On February 17, 1612, payment was arranged to the Flemish goldsmith Stephen le Gouche for a piece of jewelry with “one fair large pendant diamond, cut with fancies [facets] on all sides, and pierced at the top” that had been delivered to Queen Anne of Denmark (Green, 1858, p. 121), who was married to James VI and I (r. 1603–1625). The court accounts further describe the piercing at the top as lateral.

Noël-Antoine Pluche’s extensive multivolume work on natural history, Le Spectacle de la Nature, features an illustrated briolette described as a pear-shaped diamond cut in the “taille à l’Indienne” or Indian style (1748, pp. 349–352). The comments by Pluche, along with the Indian examples traded by Tavernier, point to the briolette form as being associated with India. Several later books specifically state this association and even mention lateral piercing. A French encyclopedia from 1859 (Guillaumin, pp. 980–981) explains that “In India, where the briolettes formerly came from, it was customary to pierce them with a very small hole in the upper part. Today a few lapidaries in Amsterdam cut briolettes very well, but they haven’t yet managed to pierce them.”

By 1600, Italian, German, Flemish, and Belgian cutters worked in India (Everaert, 2000, 2005), bringing along their techniques and cutting styles to higher-quality rough. These faceted stones would then be sent to Europe (Ogden, 2018, pp. 297–305). For example, the briolette shown in Tavernier’s book may have been cut by a European living in India rather than by a local Indian diamond cutter (there is no mention of a hole in the briolettes sold by Tavernier). Indian diamond cutters continued to follow their own styles, often cutting the lesser-quality rough destined for the Indian market. Short of documentation showing early briolettes with this specific facet arrangement by Indian cutters, dating the 6.19 ct briolette from Mr. Frank is impossible.

Figure 4. The drill hole at the tip of the stone. Note the unique surface, a remnant of the process of drawing a wire coated with diamond dust and oil back and forth. Photomicrograph by Nathan Renfro; field of view 4.02 mm.

The drill hole at the tip of this briolette (figure 4) is consistent with sawing techniques used to make holes in diamonds from the seventeenth century through the 1970s. By the mid-1500s, iron wires coated with diamond dust and oil were used to saw through a diamond. By the early 1600s, lapidaries rotated a diamond-tipped iron point or iron drill with diamond powder to create a hole from each side. Once these two holes met and the opening was large enough, the wire was inserted and drawn back and forth, the apparent method used for this diamond.

In 1811, Napoleon Bonaparte presented a 263 ct diamond briolette necklace to his empress consort, Marie Louise. It featured 19 oval- and pear-shaped briolette-cut diamonds (probably of Indian origin but faceted by European cutters in India) with drill holes. The facet arrangements of the stones in the necklace are more symmetrical and quite different from the 6.19 ct briolette.

It is unclear when laser drilling for larger holes began, but General Electric researchers used a laser to drill 0.02-inch-diameter holes into an industrial diamond in the early 1960s (Overton, 2008, p. 46). As early as 1970, GIA’s Robert Crowningshield reported that lasers were being used as part of a process to bleach or dissolve dark inclusions, and soon this treatment was widely available to members of the trade (Overton, 2008, p. 46). This means that sometime after the 1970s, lasers would have been employed for the process of drilling holes for beads and such. Older briolettes that came into GIA’s laboratory would still have holes drilled by hand, but by the 1980s, this hand drilling process was mostly abandoned. Has GIA seen a handmade drill hole in diamonds in the past, and if so, how many? Uncovering records of hand-drilled diamonds submitted to the laboratory is quite difficult since records prior to the 1990s are not computerized for searching and briolettes are rarely seen. Notations about the surface of the drill hole are also uncommon in reports. Our research into past submissions did not yield any useful results.

From the above, it is impossible to date this diamond, although it was probably cut before 1920 in India, possibly much earlier, but not by highly skilled cutters.

The briolette is heavily abraded. One possible reason is that it was kept in a diamond parcel rubbing against other diamonds for a long time, though this seems unlikely. Why would any diamond merchant allow a diamond in their stock to become so excessively abraded? It was more likely worn in an item of jewelry, repeatedly wearing against other diamonds and being casually stored by the owner, suggesting an extended period of use.

Of final note, there are several naturals on the surface of the briolette, including a trigon (figure 5).

Figure 5. The trigon is a remnant of the original crystal’s surface. Photomicrograph by Christopher Vendrell; field of view ~1.99 mm. @chapter:29


Publication Year: 2010 Title: A Microstructural Study of Pietersite from Namibia and China Abstract: Pietersite has been described as a brecciated variety of tiger’s-eye. This study examined pietersite specimens from Namibia and China (the main sources) using powder X-ray diffraction, optical microscopy, environmental scanning electron microscopy, and conventional gemological methods. On the basis of the results, quantitative approaches were developed to distinguish pietersite samples from the two localities. It is also proposed that the petrogenesis of this gem material is quite different from that of South African tiger’s-eye. @chapter:0


Publication Year: 2017 Title: Two Natural Type IIa Diamonds with Strong Phosphorescence and Ni-Related Defects Abstract: Figure 1. DiamondView images of two unusual diamonds (0.18 and 0.30 ct, respectively). Left: Unevenly distributed grayish blue fluorescence and strong blue phosphorescence. Right: Vivid red fluorescence, strong blue phosphorescence, and a dislocation network can be seen in the table. Images by Shi Tang.
Strong phosphorescence under UV excitation is rarely seen in natural diamond and normally limited to hydrogen-rich type Ia or type IaA/Ib chameleons and type IIb diamonds (T. Hainschwang et al., “A gemological study of a collection of chameleon diamonds,” Spring 2005 G&G, pp. 20–35; S. Eaton-Magaña and R. Lu, “Phosphorescence in type IIb diamonds,” Diamond and Related Materials, Vol. 20, No. 7, 2011, pp. 983–989). When seen in other diamond types, an even rarer occurrence, it is shorter and less intense. Recently, the National Gemstone Testing Center (NGTC) in Beijing encountered two natural diamonds that showed extraordinarily strong blue phosphorescence and uncommon fluorescence colors under the DiamondView.

The diamonds weighed 0.18 and 0.30 ct and were both graded as E color. Both were type IIa, with neither nitrogen absorption between 1100 and 1400 cm–1 nor boron-related absorption in their infrared spectra. Magnification and examination with a standard UV lamp showed no abnormal phenomena for natural type IIa diamonds. Instead of the deep blue fluorescence and inert phosphorescence that natural type IIa diamonds typically show in DiamondView imaging, the 0.18 ct diamond emitted unevenly distributed grayish blue fluorescence and strong blue phosphorescence, similar to that of a colorless HPHT synthetic diamond. The 0.30 ct diamond displayed vivid red fluorescence and strong blue phosphorescence, which is unusual for a natural colorless to near-colorless diamond (figure 1). Red fluorescence is rare in natural type IIa diamond and seldom reported (Summer 2016 Lab Notes, pp. 189–190).

Photoluminescence (PL) spectra collected with 532 nm laser excitation at liquid nitrogen temperature revealed something even more interesting. Along with the GR1 center emission at 741 nm typically seen in natural type IIa diamonds, the 883.0/884.7 nm doublet that is related to nickel impurity appeared in both samples’ PL spectra (figure 2). This doublet, often referred to as the “1.40 eV center,” is frequently seen in the {111} growth sectors of HPHT synthetic diamonds produced using Ni-based solvents/catalysts. Ni-related defects are more often seen in natural chameleon and greenish yellow diamonds (W. Wang et al., “Natural type Ia diamond with green-yellow color due to Ni-related defects,” Fall 2007 G&G, pp. 240–243; Summer 2014 Lab Notes, pp. 151–152) but seldom found in colorless to near-colorless natural diamonds (e.g., Spring 2017 Lab Notes, pp. 95–96). For natural diamonds with such strong phosphorescence, the presence of Ni-related emissions is unusual.

Figure 2. PL spectra of the two samples with 532 nm laser excitation. Both showed weak Ni-related doublets at 883.0/884.7 nm and strong NV centers at 575 and 637 nm, as well as the GR1 center at 741 nm.
The PL spectrum of the 0.30 ct sample also presented an extremely strong NV center at 575 nm, compared to the diamond emission at 572 nm, which explained the reddish fluorescence in the DiamondView image. In each sample’s PL spectrum, the relative intensity of NV0 (575 nm) is significantly stronger than that of NV– (637 nm), another sign of natural origin.

Figure 3. The PL spectrum of the 0.30 ct sample emitted with a 532 nm laser, at higher excitation energy. The NV0 center peak is saturated, and emissions at 648 and 776 nm are clearly seen.
Furthermore, when we exposed the 0.30 ct sample to higher-energy excitation with the 532 nm laser to reveal more subtle features, the PL spectrum showed moderately strong emissions at 648/649 nm and 776 nm (figure 3). According to previous research, PL peaks at 648.2 and 776.4 nm are associated with boron in phosphorescing type IIb natural diamonds (Eaton-Magaña and Lu, 2011). Later studies ascribed the 648.2 nm defect to a boron-interstitial complex, while the 776.4 nm peak was assigned to a B-V complex (S. Eaton-Magaña and T. Ardon, “Temperature effects on luminescence centers in natural type IIb diamonds,” Diamond and Related Materials, Vol. 69, 2016, pp. 86–95). These emissions may partly explain the strong phosphorescence of the 0.30 ct sample. Since they were not detected in the 0.18 ct sample, which also exhibited strong phosphorescence—the same is true of other phosphorescent natural IIa diamonds the authors have encountered before—this cannot be the full explanation.

Despite the synthetic-like luminescence color in DiamondView imaging and the Ni-related emissions in the PL spectra, the samples’ Fourier-transform infrared (FTIR) spectra, UV-visible spectra, PL spectra, features observed under the crossed polarizing microscope, and UV reaction indicated that they are natural instead of synthetic. These two samples demonstrated the diversity of luminescence and spectral features found in natural diamond. Their identification also highlights the importance of a comprehensive understanding of diamond origin. @chapter:11


Publication Year: - Title: Garnet Quality Factors Abstract: Garnet comes in as wide a variety of sizes and shapes as it does colors.

                      Garnets are a group that includes a number of different minerals, so appearance can vary widely. The first thing a buyer of garnets needs to be aware of is the wide variety of garnet types.

At first, the sheer number of garnet varieties can seem bewildering. It helps to think of the different types of garnets in terms of color.

Color
Pyrope and almandine range in color from purple to orangy red. Spessartine is found in a variety of orange colors, while andradite comes in yellow and yellowish green. Grossular has perhaps the widest color range of any garnet species, from colorless through yellow to reddish orange and orangy red, to a strong, vibrant green.

	These vibrant spessartine garnets are from the US state of Virginia, another important historical source for collectors. - Gift of John Bradshaw

	This tsavorite garnet has an appealing green color and is a 68.82-carat gem. - Courtesy New Era Gems

	This 3.20-carat demantoid garnet’s vivid green hue is exceptionally beautiful. In fact, it’s close to the top color for this variety. The gem is mounted in a platinum ring with diamond accents. - Courtesy A Touch of Color
Gemologists and colored stone dealers further subdivide some garnet species into varieties depending on color. For example, demantoid is a brilliant green variety of andradite that’s highly prized by collectors. Both tsavorite and hessonite are varieties of grossular. Tsavorites are green, while hessonite ranges from orange and orangy red to brownish red. Rhodolite is a purplish red variety.

	Rhodolite is the purplish variety of pyrope-almandine garnet. It can be spectacular, like this 8.72-carat gem.
Clarity
Typical garnet clarity depends on garnet type. For example, the red garnets almandine, pyrope, and rhodolite typically do not have eye-visible inclusions. Some of the orange garnets, like spessartine and hessonite, often have eye-visible inclusions.

	Hessonite garnet often has a turbulent inner appearance called the roiled affect. - © GIA & Tino Hammid, courtesy Gordon Bleck

	Demantoid might have eye-visible inclusions called horsetails that can raise its value.
Grossular is typically translucent, making it popular for cabochons, beads, and carvings.

Cut
Many garnets are cut into standard shapes and standard sizes to allow easy setting into jewelry. This is especially true of many red garnets. Expensive garnets like fine-quality tsavorite are cut into shapes and cutting styles that allow more of the weight to be retained from the rough.

	Garnets come in a variety of shapes and cutting styles.
Demantoid is often cut to exact proportions that allow the best possible display of its fire. Garnets are also popular for designer cuts and carvings. Red garnets are classic materials for cutting into cabochons and beads. They are commonly found to have high clarity and to be very transparent.

Carat Weight
Garnets can be found in all sizes and weights. Some garnets, like demantoid and tsavorite, are more commonly found in small sizes, so their value goes up significantly with size. Other garnets, like almandine, are far more common in larger sizes so there’s no dramatic rise in value as size increases. @chapter:4


Publication Year: 1982 Title: Artistry in Rock Crystal: The Van Pelt Collection Abstract: Harold and Erica Van Pelt of Los Angeles are known worldwide for their superb color photography of gems and minerals. A well-kept secret, however, has been their remarkable proficiency in the lapidary arts, specifically in the production in traditional styles of many important rock crystal objects, including candlesticks, vases, paperweights, and polished quartz crystals containing various mineral inclusions. Agate, amethyst, and other gemstones are also employed. For the most part, the machinery used to create these objects was designed or modified by the Van Pelts themselves and includes devices for sawing, grinding, and polishing. A step by-step procedure for making a hollow ostrich egg, completely covered by triangular facets, is explained. @chapter:25


Publication Year: 2022 Title: Fracture-Filled Emerald with Mysterious Filler Patterns Abstract: Emerald filler with labyrinth- and convolution-like pattern. Photomicrographs by Ungkhana Atikarnsakul; fields of view 2.0 mm (left) and 2.7 mm (right).
Emeralds are known to have natural cracks or fractures. The filling of surface-reaching fractures with various oils and resins is the most common practice to minimize fractures to improve an emerald’s appearance. The author recently examined a 3.04 ct emerald that revealed a mysterious filler pattern along the fractures, resembling a labyrinth and convolution (see above). Fracture filling can be identified using various methods. In this case, it displayed a chalky fluorescence under long-wave ultraviolet flashlight and was also detected with simple microscopic observation and fiber-optic lighting. The internal graining, irregular two-phase inclusions, and long needles within this stone indicated a natural origin. This was a unique and visually interesting pattern in the fracture filling material of an emerald. @chapter:12


Publication Year: - Title: The Real Gemology of Ethiopian Opals in ‘Uncut Gems’ Abstract: NBA star Kevin Garnett, left, plays himself in "Uncut Gems," by Josh and Benny Safdie, along with Lakeith Stanfield, center, and Adam Sandler. They are looking at an Ethiopian opal in matrix that Sandler's character, Howard Ratner, is putting up for auction in the movie. Photo courtesy of A24 Films

The magical quality of opals is the central metaphor of the 2019 movie “Uncut Gems,” starring Adam Sandler. A giant piece of Ethiopian opal, still in its matrix, is smuggled to New York.
“They say you can see the whole universe in opal, that’s how … old they are,” Sandler’s character, Howard Ratner, a jeweler and gem dealer on 47th Street in New York City, tells basketball star Keven Garnett when he shows the opal to him. Garnett is captivated to such an extent that he cannot play well without owning it.
Sandler’s character is enamored with the opal’s potentially huge sale price. He estimates that the piece weighs between 4,000 to 5,000 carats and, at up to his estimated value of $3,000 per carat, he sees millions coming his way. But the auction house he consigns it to values the piece at much less -- $150,000 to $225,000. Why?

Ethiopian opal ‒ the featured gemstone in the movie “Uncut Gems” ‒ was first discovered in Ethtiopia in 1994. Photo by Eric Welch/GIA
With opals, as with most gemstones, the final polished stones weigh only a fraction of their rough form. The specimen shown in the movie appears to have several opal nodules (though probably not black opal) inside the matrix of host rock, but that host rock appears to account for the majority of its volume. This means that it would be very difficult – in real life – to evaluate the opal and appraise its value until the matrix was removed.
“In real life, the opal nodules must be shaped and polished into gems after removing the valueless matrix, which often results in much more weight loss,” explained Nathan Renfro, GIA Graduate Gemologist® and manager of colored stone identification services at GIA. “Any realistic valuation of rough gem material is based on the potential for yielding polished gems and the risk involved in fashioning finished gemstones.”
Adding to that risk is the fact that, unlike most gems, opals are not stones or minerals.
Opals are formed from centuries upon centuries of seasonal rains that leach microscopic silica particles from sandstone, carrying them deep into underground fissures and cavities. As the deposited materials dry, the microscopic silica spheres become compressed into a closely-packed lattice. As light travels through this microstructure, it creates a dazzling kaleidoscope of flashing rainbow colors, called play-of-color.

The opal that beguiles the main characters in “Uncut Gems” was still in its matrix, similar to this piece of rough opal in matrix. Photo by Robert Weldon/GIA
The Many Colors and Types of Opal
There are five major types of opals:

White or light opal: Translucent to semi-translucent, with play of color against a white or light gray background color, called bodycolor. The opal specimen seen in “Uncut Gems” appears likely to be a representation of a white opal, despite its description as a black opal in the film.
Black opal: Translucent to opaque, with play-of-color against a black or other dark background. They often sell for higher prices than white opals because the color contrast is much greater against the dark background.
Fire opal: Transparent to translucent, with brown, yellow, orange or red bodycolor. This material, which often doesn’t show play-of-color, is also known as “Mexican opal.”
Boulder opal: Translucent to opaque, with play-of-color against a light to dark background. Fragments of the surrounding rock, called matrix, become part of the finished gem.
Crystal or water opal: Transparent to semitransparent, with a clear background. This type shows exceptional play-of-color.

Australian opal is best-known and the country remains the most prolific source of opals - mainly white and black. Ethiopia is the newest source, with the first discovery in 1994.
The most prolific source – which was named in the movie – was in found 2008 near a town called Wegal Tena in Wollo Province. This material, mostly white opal, was formed from the silica from ancient volcanic ash. Another deposit, producing black opals about 30 miles to the northwest of the Wollo mine, was discovered in 2013 – a year after 2012, the year in which “Uncut Gems” takes place.
GIA has reported extensively on opals for many years and much research can be found in this Summer 2019 Gems & Gemology chart. @chapter:18


Publication Year: 1984 Title: Freshwater Pearls of North America Abstract: Natural pearls are among the rarest and most valued of fine gems. American freshwater pearls have a history thousands of years old and played a particularly prominent role in the jewelry of the late 19th and early 20th centuries. Today, though a fraction of its original size, the American freshwater pearl industry continues to produce fine material for the jeweler worldwide. The source of this pearl is the Unio mussel, "fished" by brailing boats and intrepid divers from the rivers and lakes of America. From the Unio in which it grows, the American freshwater pearl derives its distinctive shapes and colors. A new entry to the American pearl industry is the freshwater cultured pearl, illustrated in this article for the first time ever. @chapter:14


Publication Year: - Title: Color Classification and Stability of Queen Conch Pearls Abstract: Figure 1. Six Queen conch pearls showing the differences in appearance between stronger (top) and weaker (bottom) saturation levels within the same hue. Three different hues are shown. Photo by Jian Xin (Jae) Liao.

Due to the ever increasing popularity and value of Queen conch (Lobatus gigas, formerly Strombus gigas) pearls, GIA has seen a steady increase in the number of conch pearls submitted to its various laboratories for identification. In response, this is an appropriate time to improve and expand upon GIA’s conch pearl color terminology in general and, more specifically, how it is applied to GIA Pearl Identification Reports.
To that end, GIA has redefined its approach to conch pearl color, so that it bears a stronger resemblance to the more refined process applied to GIA’s classification of nacreous pearls. Establishing and defining practical color boundaries has improved specificity and consistency in the description of conch pearl color opinions between all GIA gemologists and laboratories. In addition, the resulting conch pearl color classification system provides more precision in the communication of conch pearl color, for both the pearl industry and the public at large.
In order to be identified as Queen conch pearl, non-nacreous pearls that formed in the Lobatus gigas mollusk must fall into the red (pink) hues, namely reddish purple (extremely rare), purplish red, red, orangy red, and reddish orange. While conch pearls do occur in colors outside of this hue range, it is challenging to definitively identify them as such in a laboratory when they lack any red (pink) hue. Because the vast majority of Queen conch pearls fall into mid-tone and mid-saturation ranges, in the straight red hue, GIA (in keeping with the trade) has traditionally described conch pearl color in a much more general way than nacreous pearl color. The bulk of conch pearls were simply described as pink, unless the tone and saturation were significantly out of the mid-range in either direction (weaker or stronger). GIA’s current and historical data, as well as the studied sample materials, produced results that reinforced the notion that pink occurred most often, followed by Strong pink, Light pink, and Very light pink, with Red occurring very rarely. Some examples of these pearls are shown in figure 1.
In determining the boundaries for the different aspects (hue, tone, and saturation) of Queen conch pearl color classification, a number of resources were used. In addition to physical samples, we also used references from GIA’s database, with the application of color science, and from GIA’s color system for nacreous pearls. The goal was to create practical boundaries and color ranges that were discrete enough to differentiate between the obvious typical variances in conch pearl color, but would not be difficult to employ or understand. Once the accuracy of the boundaries was established, a “Conch Pearl Color Terminology Chart” was developed. This chart illustrates all of the boundaries, as well as the master pearl placement in the defined color space, and the designated color classification terminology.
A key issue that needed to be explored before expending the time, effort, and cost to create Queen conch pearl masters was color stability, especially with regard to the pink component; we have seen previously that such color can be modified under X-ray radiation. One quick illustrative experiment, where a piece of Queen conch shell was exposed to X-ray radiation under GIA’s X-ray luminescence instrument (100 kV, 3.2 mA, approximately 4 inches from the X-ray source), is presented here. The left side of the shell’s surface was shielded from the radiation, while the right side was exposed to X-rays. After 15 minutes of exposure, the apparent color of the shell turned from pink (left) to purplish (right), with reduced saturation (figure 2). A different result was observed when pink shell was exposed to short-wave UV radiation, for an extended time (after 4 hours), using a conventional 4-watt short-wave (254 nm) lamp. However, unlike the hue change observed in response to X-ray exposure, the effect observed using short-wave UV was a reduced saturation of the same hue (fading). No obvious changes were observed when the shell was exposed to long-wave UV radiation (365 nm) for 6 hours, although the effect of long-term exposure under long-wave UV radiation is still unknown. Exposure to sunlight and the fluorescent white light used for pearl classification also failed to induce any color changes.

Figure 2. Hue and saturation changes observed on a piece of Queen conch shell after 15 minutes’ exposure to X-ray radiation. The shielded area is to the left, the exposed area to the right. Photo by Sood Oil (Judy) Chia.
In addition, we recorded a real-time color change of a section of Queen conch shell exposed to X-ray radiation for 10 minutes, which clearly shows a gradual color shifting over this period. A ten-second time-lapse video is shown here, with the before and after appearance of the shell also shown at the end of the video. However, this experiment was strictly for research purposes, as the actual laboratory testing of Queen conch pearls only requires a very brief exposure of the samples under X-rays at minimal power settings necessary for examination of their internal structures. Proper shielding with lead is also used when multiple conch pearls are mounted in a single piece of jewelry, to avoid any unnecessary collateral exposure.

	Queen Conch Shell Exposed to X-Ray Radiation.

In summary, GIA has developed a consistent in-house color classification system and color masters for conch pearls, resulting in a comprehensive yet straightforward method to evaluate conch pearl color. While the color stability experiments clearly illustrate that the color of Queen conch shell and pearls may shift in hue and/or saturation under either X-ray radiation or short-wave UV radiation, GIA has long-standing precautions in place to mitigate the issue. Furthermore, the results showed that under standard lighting conditions, no discernible color changes were evident. Improved precision in describing conch pearl color facilitates better color consistency between GIA gemologists and the GIA laboratories. The clearer color terminology also allows buyers and sellers to communicate more accurately and effectively with each other. @chapter:14


Publication Year: - Title: How to Protect Your Diamond from Chipping Abstract: Diamonds are known for their hardness – their ability to resist scratches and abrasions.  But diamonds are not impervious to damage, since their hardness is uneven along different crystal directions. This image shows a 1.05 ct diamond with a chip starting at its girdle, extending to the culet. Photo © GIA.

	DIAMOND DURABILITY

	Gems are valued for their beauty, rarity, and durability. Durability is a gemstone’s ability to withstand wear, heat, and chemicals. The concept of durability consists of three properties:

		Hardness: How well a gemstone resists scratches and abrasion

		Toughness: How well a gemstone resists breaking and chipping

		Stability: How well a gemstone resists chemicals and thermal shock

	Diamond is very stable and extremely hard, but only somewhat tough. The hardness is uneven along different directions of the crystal, and this has important implications both for the cutting process and the durability of diamonds cut in various shapes.

Hardness
	The hardness of a diamond is a result of its very compact crystal structure. “Diamond has an indentation or scratch hardness five times that of carbides. [Figure 1] illustrates the hardness of diamond compared to other materials according to both Moh’s [sic] and Knoop’s hardness scales. However, diamond is relatively brittle and will chip or fracture if it is not handled and protected against shock” (V.C. Venkatesh and S. Izman, Precision Engineering, 2007, p. 50). Diamond is the hardest known natural mineral on both the Mohs and Knoop scales, which characterize a mineral’s scratch resistance through the ability of a harder material to scratch a softer material.

	Figure 1. A comparison of the Mohs hardness scale and the Knoop hardness scale, a
	micro-hardness test where a pyramidal diamond point is pressed into the polished
	surface of the sample with a known load for a specified time and the resulting indentation
	is measured with a microscope. Illustration modified from V.C. Venkatesh and S. Izman,
Precision Engineering, 2007, p. 50.

Stability
	Diamonds are very stable and invulnerable to virtually all acids. They can also withstand higher temperatures than most gemstones. Sudden extreme temperature changes can cause damage, however.

Toughness
	Diamonds can chip or fracture from hard impact, especially in areas where the carbon atoms are not tightly bonded. These areas, called cleavage planes, are the major source of damage to diamonds (figure 2). The toughness scale used in scientific literature is called a fracture toughness scale, but it is rarely mentioned in gemology. The toughness scale measures (in erg/cm2) the work required to separate two surfaces of a crystal along a certain crystallographic plane. Values for diamond generally range from 5,000 (along the cleavage planes) to over 8,000 (in the “hardest” direction). Compare those values to 225,000 for nephrite and 120,000 for jadeite, which are tougher, and 600 for corundum, which is not as tough.

Figure 2. Atoms of carbon are arranged in very tight rows. In the directions where carbon atoms are most compact, it is very difficult to break a diamond. Note that atoms also lie in planes. The distances between planes are greater than the other distances between the carbon atoms. In the directions where the atoms lie in planes, diamonds can break, though with some difficulty. Those directions are referred to as cleavage planes. Illustration by Al Gilbertson, © GIA.

	TOUGHNESS: THE ACHILLES HEEL OF DIAMOND

	Even though diamond is the hardest natural material, it can chip and fracture in the course of normal wear. Diamond is formed in the cubic crystal system and has four perfect cleavage directions. A cleavage plane is the weakest direction in the molecular arrangement of the crystal. Diamonds are tougher in the directions where the atoms are bonded tightly together, less tough where they’re not so tightly bonded. The most common form of the natural diamond crystal is an octahedron (figure 3), and our focus will be on that typical shape. Cleaving is the splitting of a diamond crystal parallel to one of its triangular, octahedral planes. While not the perfect example, compare wood, which has a single grain typically split by an axe with ease. A natural diamond crystal can only be cleaved parallel to one of the triangular octahedral faces (figure 4).

Figure 3. Idealized octahedron. Illustration by Al Gilbertson, © GIA.

Figure 4. Cleavage planes are parallel to the triangular octahedral face. Illustration modified from V.C. Venkatesh and S. Izman, Precision Engineering, 2007, p. 54.

	Because diamonds are harder and tougher along certain directions of the octahedral crystal, they are also more resistant to chipping, abrasion, or cutting with other diamonds along these directions (figure 5). There are also softer directions (figure 6). For some of the famous historical diamonds, months were spent planning before cleaving because the external partial crystal form obscured the octahedral directions.

Figure 5. These are the hard directions in diamond crystals, the most difficult ones for the cutter to work with. Illustration by Al Gilbertson, © GIA.

Figure 6. These soft directions are easier for the cutter to work with. Illustration by Al Gilbertson, © GIA.

	Diamonds are rarely cleaved today. Usually they are sawn and, more recently, cut by laser. However, cutters still need to understand the hard and easy directions of polishing as well as the location of cleavage planes in order to plan cutting. An octahedron generally yields a round brilliant from a certain location within the crystal (figure 7).

Figure 7. When cut from the octahedral crystal, the outer edge of the round brilliant would nearly touch the outer edge of the original octahedron. Illustration by Al Gilbertson, © GIA.

	During the planning stage, a saw is used to cut off the top portion, which can be used to cut another diamond. Note that the typical crown (top) of a round brilliant is slightly higher than the typical crown of a princess cut. If the cutter wants to create two princess-cut diamonds from a crystal, the planning is slightly different than when two rounds are being cut (figure 8).

Figure 8. When sawn, the lower plane (lower red line) will eventually yield two princess-cut diamonds. If the crystal were being cut to yield round brilliants, the sawing line would be the higher line (upper red line). Illustration by Al Gilbertson, © GIA.

	Remember that diamonds are tougher in the directions where the atoms are bonded tightly together, less tough where they’re not so tightly bonded. Look at the location of the corners on a princess cut, which are very vulnerable to chipping since they lie close to the cleavage plane. Cutting styles like these, with pointed corners or ends, are often set with prongs to protect the corners from chipping. Even still, a hard blow to a prong at a corner of a princess cut (figure 9) can cause a chip to run down the side of the diamond. This is not exactly at the cleavage plane, where the carbon atoms are farthest apart, but very near it. When chips occur, they rarely look like smooth flat planes of cleavage. Rather, they appear to be stepped, because they are not directly on the cleavage plane (figures 10 and 11).

Figure 9. The corners of a princess cut are very vulnerable to chipping since they lie close to the cleavage plane. Illustration by Al Gilbertson, © GIA.

Figure 10. The chip at the corner of this princess-cut diamond has a stepped look since it is near but not directly at the cleavage plane. Photo by James Gibson, © GIA.

Figure 11. Chips typically have a stepped appearance. Photo by Mitch Lam, © GIA.

	HOW TO MINIMIZE THE RISK OF DIAMOND CHIPPING

	Chips typically occur when the girdle (edge) or point of a diamond strikes something hard. Bathroom and kitchen countertops, as well as jewelry items with diamonds worn next to each other, are common causes of chips.

1. Avoid shapes with points or sharp corners
	Any shape of diamond with points or sharp corners is more exposed to chipping at those locations (figures 11 and 12). Round, oval, and rounded-corner cushions don’t have that point exposure. A more recent cutting technique called chamfering is used by some in the diamond trade and believed to improve durability for princess cuts. Chamfering places a very small flat facet on the corners (figure 13).

Figure 12. Corners for emerald cuts, triangular shapes, radiants, and princess cuts are at higher risk and need adequate girdle thickness to minimize their exposure to chipping. Here an extra facet at the corner of a princess cut brings that corner to a sharp point, resulting in a very high risk of being chipped. Photo by James Gibson; illustrations by Al Gilbertson, © GIA.

Figure 13. A chamfered corner on a princess cut is so small that most cannot see the small facet without magnification. Photo by Jonathon Muyal, illustrations by Al Gilbertson, © GIA.

2. Protect the culet
	At one time, almost all standard round brilliant cut diamonds and many other shapes were cut with a small facet at the culet. This was to protect the culet from chipping. Now most diamonds come to a sharp point at the culet, and thus all culets with points are vulnerable (figure 14). Once they are set in jewelry, however, there is little risk of damaging the culet.

Figure 14. Pointed culets are vulnerable to chipping when diamonds are loose and strike against each other in stone papers. Photo by James Gibson, © GIA.

3. Avoid girdles with very thin sections
	While a strong blow can break a diamond at the girdle, a thicker girdle is more difficult to chip. Girdles with very thin places along the sides or at the corners and points are at a much higher risk of damage (figures 15 and 16).

Figure 15. Extremely thin girdles are at extreme risk of being chipped. Here, a marquise has a knife-edged portion of a girdle that could be chipped very easily. Photo by Leo Ochoa, illustrations by Al Gilbertson, © GIA.

Figure 16. This emerald cut with an extremely thin girdle has two chips. Photo by Leo Ochoa, illustrations by Al Gilbertson, © GIA.

4. Chose a setting that protects the diamond
	Vulnerable points or corners are better protected with bezels, partial bezels, or V-shaped prongs.

5. Use caution with tension settings
	A tension setting holds a diamond in place using a groove cut into the metal that the girdle fits into, and the two ends of the ring press tightly against the diamond’s sides. A jeweler with experience in tension settings will be very careful about the condition of the girdle before allowing a diamond to be set in this manner.

	The mounting is already exerting pressure on the diamond at two opposing locations on the girdle. Hitting the side of the ring puts even more stress on the girdle. This style also leaves the exposed sides of a diamond vulnerable to damage just during casual wear.

6. Regularly inspect prongs for damage
	A very common cause of chipping is that the prongs holding the gem in place in a piece of jewelry become bent or broken. If a diamond is loose in the mounting, it is at higher risk of getting chipped. Prongs protect their corners, points, and sides. If the prongs become bent or broken due to wear and tear, they are not doing their job: protecting your diamond.

	Even if only one prong is damaged, your diamond is no longer held securely in its mounting.

7. Don’t wear a diamond that has already chipped
	If a diamond already has a chip, some think they can take care of the mounting later. That knife-edged portion of the diamond that is chipped has an extremely high risk of getting chipped far worse. Stop wearing it until you can have it repaired.

8. Be careful with inclusions near the girdle
	It’s rather obvious that a diamond with many inclusions located near the girdle and/or points is rendered more prone to chipping or breaking. But sometimes there can be a small feather or other small inclusion near the girdle or point that also makes the diamond vulnerable (figures 17 and 18). If the stone is hit precisely on a feather or inclusion near the direction of a cleavage plane or at a point, a chip is likely to occur. Open cavities at the girdle are much like chips and are more easily damaged (figure 19).

	Figure 17. The small cluster of feathers at the corner of this princess cut poses a high risk
	for damage when setting the diamond or when it is being worn. Photo by Mitch Lam, © GIA.

	Figure 18. The corner of this radiant cut has a large feather that places it at risk for further
	damage. Photo by Mitch Lam, © GIA.

	Figure 19. The open cavity at the girdle makes this thick girdle more susceptible to chipping. Photo by Mitch Lam, © GIA.

	There is no such thing as perfect toughness. Any gem will break, not just chip, if it is hit hard enough. Diamonds are very tough, but remember that if a cutter can purposely cleave (split) a diamond by giving it a sharp blow in the right direction, you can achieve the same thing if you hit it hard enough accidentally. You are more likely to damage a diamond at the girdle or at a point. Diamonds with exceptionally thin places on their girdles are very vulnerable. To avoid damage, you should only wear your diamond jewelry during activities where you are unlikely to hit them hard against solid objects. @chapter:31


Publication Year: 2008 Title: Winter 2008 G&G Lab Notes Abstract: Fancy Dark Brown-Yellow Zoned Type IIa/IIb Diamond
HPHT-Treated CVD Synthetic Diamond Submitted for Dossier Grading
Quartz with Secondary Covellite Dendrites
Induced Copper Contamination of Tourmaline

To view the full section, download the PDF above. @chapter:11


Publication Year: 1990 Title: New Technologies of the 1980s: Their Impact in Gemology Abstract: The 1980s witnessed great development in the application of new technologies to gemology. These technologies provided new or better ways to grow synthetic gem materials and to treat natural ones. They also permitted numerous breakthroughs in gem identification, in areas where classical gemological methods were no longer sufficient to make a positive identification. In particular, various types of spectroscopy proved to be of important practical value, for example, infrared absorption, X-ray fluorescence, Raman scattering, and cathodoluminescence. @chapter:23


Publication Year: 2021 Title: In Memoriam: Jean Claude Michelou Abstract: Colored stone industry veteran Jean Claude Michelou was founder and longtime editor-in-chief of ICA’s quarterly, InColor. Photo by Vincent Pardieu.

The colored stone industry lost one of its true leaders with the passing of Jean Claude Michelou (see above) on May 3 at the age of 72. Mr. Michelou graduated from the London School of International Business and began selling emeralds in Colombia in 1977. The business he later established, Imperial Colors Ltd., specializes in rough buying, grading, and cutting of emerald, tourmaline, beryl, and sapphire. He relocated the company to Bangkok in 2018.
Mr. Michelou was active with the International Colored Gemstone Association (ICA), serving as a board member for 18 years and as vice president for 10 years. In 2004, he founded ICA’s quarterly magazine, InColor, and was its editor-in-chief until his retirement earlier this year. He was also a consultant for the United States Agency for International Development (USAID), the World Bank, and other agencies on developing standards for the colored stone industry. In addition, he served on the advisory board for the University of Delaware’s Gemstones and Sustainable Development Knowledge Hub and organized the World Emerald Symposiums held in Bogotá since 2015.
For more than a decade before his passing, Mr. Michelou had been deeply involved in several beneficiation projects in source countries, including the Swat Valley emerald deposits of Pakistan and a Nigerian sapphire mining venture. He shared his insights on supply chain transparency and beneficiation with G&G in the Spring 2018 issue (Gem News International, pp. 93–94). Over the years, Mr. Michelou was a valuable source of knowledge for this journal and a mentor to many young industry professionals. We extend our condolences to his family and friends. @chapter:28


Publication Year: 2018 Title: Discovery of Color-Change Chrome Grossular Garnets from Ethiopia Abstract: Figure 1. Left: Three rough garnets (left to right, stones 2, 3, and 4) and one faceted garnet photographed in an LED light source with 6000K color temperature (a daylight-equivalent light simulator). Right: The same stones photographed in an LED light source with 3100K color temperature (an incandescent light simulator). The 2.705 ct faceted stone measures 8.08 × 7.18 × 5.49 mm. Photos by Kevin Schumacher.
Ethiopia has become a significant producer of opal, sapphire, and emerald in recent years. In addition, reports of gem-quality green garnets have started to emerge (B. Williams et al., “Tsavorite reportedly from Ethiopia,” Journal of Gemmology, Vol. 35, No. 8, 2017, pp. 702–704).
Todd Wacks (Tucson Todd’s Gems, Tucson, Arizona, and Vista, California) recently submitted three rough and one faceted garnet (figure 1, stones 1, 2, 3, and 4) to GIA in Carlsbad for scientific examination. He purchased the garnets from Inna Gem, which reported that the garnet mine is located near the town of Wbi and the new Dubuluk emerald deposit (Spring 2017 GNI, pp. 114–116). The stones showed obvious color change from yellow-green under daylight-equivalent lighting to orange-brown under incandescent illumination. This is similar to the color-change behavior reported for some color-change garnets from Sri Lanka (Spring 2017 GNI, pp. 137–138).
Standard gemological testing revealed a refractive index (RI) of 1.740 on the faceted stone. Hydrostatic specific gravity (SG) of all garnets in this study ranged from 3.62 to 3.68. Fluorescence was inert to long-wave and short-wave UV light. Rotating the stones 360° between a pair of crossed polarizing filters revealed an anomalous double refraction. Using a handheld spectroscope, faint absorption bands at 480–490 and 570–590 nm were observed. Microscopic examination showed fingerprints composed of two-phase inclusions, iron-stained and cloudy fractures, long thin etch channels, unidentified transparent crystals, and zoned greenish brownish yellow areas. These properties are consistent with grossular (grossular-andradite) garnets (I. Adamo et al., “Tsavorite and other grossulars from Itrafo, Madagascar,” Fall 2012 G&G, pp. 178–187; M.L. Johnson et al., “Gem-quality grossular-andradite: A new garnet from Mali,” Fall 1995 G&G, pp. 152–166).
Laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) analyses were performed to obtain the chemical composition of these garnets using a Thermo Fisher iCAP Qc ICP-MS coupled with an ESL NWR213 nm laser ablation unit. USGS glass standards GSD-1G and GSE-1G and NIST glass standard 610 were used as external standards. 29Si was used as an internal standard. The analyses were performed in the same region where spectroscopic data was collected for stones 3, 4 (Ethiopian garnets), 5 (non-Ethiopian tsavorite), and 6 (non-Ethiopian demantoid) (see supplementary table S1).

Figure 2. The calculated visible absorption spectra (corrected for reflection loss) of garnets 3, 4, 5, and 6 with various path lengths. Transmission window A is centered at 545 nm. Transmission window B is between 620 and 650 nm; transmission window C is centered at 520 nm. In Ethiopian grossular stones 3 and 4, the absorption bands at 431 and 599 nm are caused by Cr3+. In stone 5 (non-Ethiopian tsavorite) the absorption bands at 428 and 611 nm are caused by V3+. In stone 6 (non-Ethiopian demantoid) the absorption bands at 431 and 627 nm are caused by Cr3+ (Adamo et al., 2009). The human eye is not color sensitive above 650 nm or below 420 nm wavelength (gray color zoning in the graph). The transmission in these ranges cannot contribute to the color seen. Please note that the y-axis units are in true absorbance and not absorbance coefficients.
The Ethiopian garnets are predominantly composed of 87.24–91.60% grossular, 6.03–8.19% andradite, 1.04–2.80% spessartine, 1.29–0.55% uvarovite, 0.71–0.82% pyrope, and 0.03–0.05% goldmanite (again, see stones 1–4 at the link provided above). The dominant chromophore is Cr3+ at about 0.19–0.43 wt.%, with an almost negligible contribution from V3+. This contrasts significantly with most tsavorite grossular garnets, whose color is dominantly derived from V3+ with a lesser contribution from Cr3+ (Adamo et al., 2012).

Figure 3. The color panels of four garnets (stones 3, 4, 5, and 6) under CIE A (incandescent) and CIE D65 (daylight-equivalent) illumination are quantitatively reproduced. The garnets’ colors are shown at different light path lengths (defined by stone thickness). For each sample, the top and bottom rows represent the color under incandescent light (A) and daylight-equivalent light (D65), respectively. For calculation methods, please see Sun et al. (2017).
UV-Vis-NIR spectra (figure 2) were collected and corrected for reflection loss. These spectra were then used to quantitatively calculate the color of the garnets at a wide range of path lengths and under different lighting conditions. In addition to two of the Ethiopian grossular garnets, UV-Vis spectra were also collected on the non-Ethiopian tsavorite (stone 5) and the non-Ethiopian demantoid (stone 6) for comparison. The chemistry of stones 5 and 6 is also reported; see the supplementary table S1.

The calculated color panels of stones 3–6 under daylight-equivalent lighting (CIE D65 illumination) and incandescent light (CIE A illumination) are shown in figure 3, which shows the possible colors these four garnets would exhibit with different path lengths (defined by stone thickness) and the approximate corresponding carat weight of a well-proportioned round brilliant (for details of this calculation, see Z. Sun et al., “Vanadium- and chromium-bearing pink pyrope garnet: Characterization and quantitative colorimetric analysis,” Winter 2015 G&G, pp. 348–369). Ethiopian grossular stone 4 showed a stronger color change and a higher chromium component than Ethiopian grossular stone 3. Stone 6 showed a more yellowish green than stone 5 due to the demantoid’s higher Fe component, which absorbs more blue light than in tsavorite (again, see figure 2).

Figure 4. In the CIELAB 1976 color circle, the color of stone 4 changes from yellow-green under CIE D65 illumination to yellow-orange under CIE A illumination, with a hue angle difference of 16.68˚ and a chroma difference of 7.40. The color of stone 3 changes from yellow-green under CIE D65 illumination to yellow-orange under CIE A illumination, with a hue angle difference of 15.94˚ and a chroma difference of 3.74. Stone 5 (tsavorite) has no color change in D65 and A visually. The hue angle difference is 0.48˚, and the chroma difference is 21.73. Stone 6 (demantoid) has no color change in D65 and A visually. The hue angle difference is 1.63˚, and the chroma difference is 20.54.
One way to judge the quality of a color-change stone is to plot the color panel pair in the CIE 1976 color circle. Good color-change pairings show a large hue angle difference, a small chroma difference, and large chroma values (Z. Sun et al., “How to facet gem-quality chrysoberyl: Clues from the relationship between color and pleochroism, with spectroscopic analysis and colorimetric parameters,” American Mineralogist, Vol. 102, No. 8, 2017, pp. 1747–1758). The color coordinates of the four stones in daylight-equivalent (D65) and incandescent (A) illumination were plotted in the CIE 1976 color circle (figure 4). Ethiopian grossular stone 4 had the largest hue angle difference among the four stones and a relatively small chroma difference. The non-Ethiopian tsavorite and demantoid both had a very small hue angle difference that was close to zero but with large chroma difference.
One interesting observation is that the Cr3+ absorption band shifted significantly from 627 in demantoid (stone 6) to 599 in the Ethiopian grossulars (stones 3 and 4; all stone samples contained little V). This shift opens a transmission window B in the red region shown in figure 2. To our knowledge, color-change behavior has not been reported in tsavorite or demantoid. This is because the absorption bands of V3+ at the 610 region in tsavorites (green grossular) or of Cr3+ at the 627 nm region are dominated by Cr3+ in demantoids and prevent the transmission of red light in these stones. In other words, there is no transmission window in the red for tsavorite or demantoid. However, these Ethiopian grossulars have little V3+, and the Cr3+ absorption is shifted away from the red region, which allows for significant transmission of red light through these stones. This creates a transmission window that produces significantly different color for the Ethiopian grossular in incandescent illumination versus daylight. To the authors’ knowledge this was the first group of color-change gem-quality chrome grossular garnet reported. @chapter:4


Publication Year: - Title: Bench Tip #16: How to Modify a Goldsmith Hammer Abstract: Modify a goldsmith's hammer

Jewelers and metalsmiths have had to make their own tools throughout the ages to accomplish different tasks at the jeweler’s bench. One tool a jeweler can’t do without is a hammer. Today, many styles of hammers, made in a variety of shapes and materials, are available to the jeweler.

The hammer used here as an example of how to make modifications is used for riveting, shaping, forming and working on rings for sizing. The hammer has one round/slightly contoured end (called the pean) one chisel-shaped end and a hardwood handle.

Two modifications that are crucial to a jeweler will be made to:

		The handle, which is key to maximizing its effectiveness at achieving its specific task

		The round/slightly contoured face and the chisel-shaped heads

A hammer handle that is too long will not be balanced, and can cause fatigue. If it is too short, it reduces the amount of force you can apply with the hammer. The length of the handle can be modified to fit your hand by measuring from the tip of your thumb to the tip of your pinky, with your hand spread out. Alter the length of the handle, by cutting it down, to help you apply the maximum force to the object.

Next, you can modify the hammer heads by contouring and polishing them. Make a stack of paper on your work surface and place abrasive paper on top. Move the hammer in a circular motion over the paper to shape it. The stack provides a cushion so you can more easily modify the head. Work with sheets graduating grits of abrasive paper, from coarse to fine.

	You will achieve the maximum potential of your goldsmith hammer by modifying the round
	(top) and chiseled (bottom) heads. Polish with tripoli and rouge on a hard felt buff. This will
	give the surface of the round head a slightly convex shape, reduce the sharp outside edges,
	and leave a polished surface with minimal tool marks. If you don’t polish the head, the
	surface marks will transfer to the metal you are working on when struck.

You should apply the same modification to the chiseled end of the hammer head. Instead of a circular motion, however, use a back and forth motion that follows that end’s contours. The goal is to put a convex surface on the end face and to round over all edges and corners so they don’t leave deep, hard-edged marks in the metal you work on. Use the same materials and set up you used to finish and polish the hammer’s round face.

These two modifications will help you achieve the maximum potential of your goldsmith hammer.

	This goldsmith hammer is being used to tighten a hinge pin. @chapter:28


Publication Year: 2015 Title: Apatite “Piñata” Abstract: Figure 1. A 42.92 mm polished sphere with an exposed orange calcite inclusion was fashioned by Dale Carson from fluorapatite recovered from the Yates uranium mine in Otter Lake, Pontiac County, Quebec, Canada. Photo by Elise A. Skalwold.

While gemologists are accustomed to transparent and translucent materials with microscopically visible inclusions, semi-translucent to opaque gems are generally not considered potential hosts of interesting inclusions. Consequently, only the surfaces of these materials are really explored microscopically. This should not dissuade the avid inclusionist from taking the opportunity to look closely at them for unexpected surprises that may be revealed.

Apatite is appreciated for its range of beautiful colors and other optical properties, as well as its morphological characteristics. Most gem apatite is the fluorine end-member of the apatite group known as fluorapatite, or apatite-(CaF). Transparent gem-quality apatite often contains interesting inclusions such as tourmaline, glass, biotite, goethite, hematite, manganese oxide, and pyrrhotite, so it seems logical that the semi-translucent to opaque form would also host inclusions, albeit obscure ones.

The Otter Lake locality in southern Quebec, Canada, is well known for producing aesthetic cabinet specimens featuring elongated prismatic fluorapatite crystals on orangy or pinkish marble matrix, sometimes with deep purple fluorite in the associated mineral assemblage as well. Damaged crystals of limited potential commercial value as faceted gems or mineral specimens may be fashioned into lapidary items such as carvings, cabochons, and spheres (figure 1), or simply find their way into study collections.

A fascinating dark green apatite crystal obtained from Luciana Barbosa of the Gemological Center in Asheville, North Carolina, recently captured our attention. This specimen, from the Yates uranium mine at Otter Lake, measured 31.16 mm in length and weighed 99.21 ct (figure 2).

Figure 2. This 31.16-mm-long fluorapatite crystal was also recovered from the Yates
uranium mine. Photo by Elise A. Skalwold.
What made this crystal interesting was that it had cracked in half along a plane more or less perpendicular to its length, exposing the otherwise unseen inclusions (figure 3). The two spherical inclusions were identified by Raman analysis as brownish orange calcite, the larger of which measured 5.74 mm in diameter (figure 4). Because of its size, this inclusion was probably at least somewhat responsible for the host apatite cracking apart.

Figure 3. Two orange spherical inclusions were exposed when the fluorapatite crystal fractured in half. Photo by Elise A. Skalwold.

Figure 4. The larger inclusion in the apatite, a 5.74 mm sphere of orange calcite, featured
a pair of purple “eyes” on its surface. Upon further analysis, these were revealed to be
fluorite. Photomicrograph by John I. Koivula.
Upon closer inspection and Raman analysis, two tiny deep purple fluorite crystals could be seen perched on the surface of the largest included calcite sphere (again, see figure 4). The resulting bouquet of contrasting colors and the surprising spherical form of the calcite inclusions with purple fluorite “eyes” turned mishap into treasure, reminiscent of breaking open a piñata to find candy within. These calcite spheres are a mineralogical enigma, though current research suggests they formed at high temperature from entrapped carbonate melt (F. Sinaei-Esfahani, “Localized metasomatism of Grenvillian marble leading to its melting, Autoroute 5 near Old Chelsea, Quebec,” master’s thesis, Department of Earth and Planetary Sciences, McGill University, Montreal, 2013).

While providing valuable insights into geological processes, such inclusions in gems and minerals never fail to enrich the day-to-day experience of gemologists and mineralogists. @chapter:13


Publication Year: 2015 Title: Book Review: Towards an Art History of Medieval Rings: A Private Collection Abstract: By Sandra Hindman, with Ilaria Fatone and Angelique Laurent-di Mantova. Introduction by Diana Scarisbrick, hardcover, illus., 260 pp., publ. by Paul Holberton Publishing, London, 2015, £35.00.

	The 35 rings in this private collection belong to Sandra Hindman, owner of Les Enluminures, a gallery of artworks from the Middle Ages and the Renaissance with locations in Paris, Chicago, and New York. The book is the accompanying catalog to recent exhibitions at Les Enluminures.

	It is one of the few modern volumes on the topic of medieval rings. Beautifully printed and illustrated, it is a scholarly overview of the design and use of medieval rings ranging from the Early Byzantine period through the Renaissance.

	The book is divided into individual chapters: Byzantine & Early Christian, Early Medieval, Gothic, and Renaissance. Each chapter gives a brief overview of the period and the drivers that influenced the creation of these rarities. The contents have been arranged chronologically so as to compare and contrast the styles between and within each period. In addition to multiple images of each ring, there are comparative photos of rings and objects in other collections. The book also presents the catalogue entry for each of the rings, featuring their description and technical details on construction and condition.

Towards an Art History of Medieval Rings is an exceptionally crafted and well-organized book for anyone interested in this rare topic. @chapter:21


Publication Year: 2022 Title: Conversation with True Blue Opals and Gems Abstract: Figure 1. A 13.12 ct black opal from Lightning Ridge, 19.7 × 14.4 × 7 mm. Photo by Robert Weldon; courtesy of True Blue Opals and Gems Inc.
At the AGTA show, we spoke with Natassa Patel, who along with her mother, Salma, owns and operates True Blue Opals and Gems (Tucson and Gold Coast, Queensland, Australia). While they typically specialize in black opal from Lightning Ridge (figure 1), the closure of Australia’s state borders during the pandemic prevented them from traveling there. Canceled trade shows and the inability to see clients face-to-face also limited business, but their online sales increased and they began sourcing from Queensland’s Yowah and Koroit boulder opal fields. The majority of the stones at the booth were Yowah and Koroit boulder opal, with only one showcase of black opal.
“Circumstance made us specialize in Yowah and Koroit,” Natassa said. “I think my mom has taught me that, to make the opportunity. We could have just left it at home because everybody’s chasing black opal, but we didn’t. We believe in it.”
According to Natassa, buyers don’t want “generic” stones anymore, and opal is “very non-generic.” She said boulder opal (figures 2 and 3) is “like a bouquet of flowers” with its immense variety of colors and patterns. “I think it appeals to the uniqueness we all want to feel, with our imaginations running wild in trying to see landscapes and faces and paintings that are so prevalent in the patterns of boulder opals,” she said.

Figure 2. A Yowah boulder opal or “Yowah nut” weighing 312.6 ct and measuring 74.6 × 67.3 × 22.6 mm (detail on the right). Photo by Robert Weldon; courtesy of True Blue Opals and Gems Inc.

Figure 3. Boulder opals: “Rainbow Jungle” (left), 73.53 ct and 52 × 25 × 7 mm, and “Red Lantern” (right), 188 ct and 54.8 × 41.4 × 22.0 mm. Photos by Robert Weldon; courtesy of True Blue Opals and Gems Inc.
Natassa said that despite the common belief that anticipating customer demand is the way to success, it’s important to her and her mother “to stay true to ourselves and sell what we like.” She added that if you focus on persuading people by sharing knowledge rather than on trends, you can create a trend. “I like to pave the road. I don’t like to follow: I want to go first.”
When True Blue began exhibiting in Tucson in the early 2000s, they often had to educate customers on black opal. Natassa estimated that the number of opal dealers at the Tucson shows has increased perhaps tenfold since, which has increased customer understanding of the gem. Boulder opal has become more popular, but they still have to inform people about Yowah and Koroit boulder opal.
“No matter if we sell one stone or a hundred stones, the focus, for me, should still be the same,” Natassa said. “To bring something new, to educate people. What’s the point of doing all this, if people still misunderstand opal or they don’t see the value in it?”
Natassa noted that while many more designers use opal now, customers are still coming to terms with pricing. She attributes this to a lack of understanding of opal mining: The cost of opal is difficult to standardize because there are too many variables in its mining. “If you find one pocket in five years, and you’ve spent half a million dollars in mining, then that parcel is half a million plus,” she said. “And sometimes there’s a drought—no water to wash the dirt to see if there’s opal trace.”
True Blue celebrated their 20th anniversary last year, but Salma’s passion for opal goes back further. After the Patels moved from Vanuatu to the Gold Coast in 1988, Salma was free to wander the shops while Natassa and her siblings were in school. She became fascinated with the black opals that were so different from the familiar gold and diamonds. After learning they were from Lightning Ridge, she traveled there with an opal dealer friend in the early 1990s. “I think it’s something that she was called to,” Natassa said. “I think what happened to her was what happened to me.”
In 1995, Salma bought a small store on the Gold Coast, initially focusing on small parcels. Natassa helped her mother on nights and weekends while attending university, although she wasn’t interested in gemstones at first. “I’m assertive, but I’m not aggressive,” she said. “I didn’t know how to push them.”
Salma’s first visit to Tucson was in 1995, and a few years later she exhibited at the Globex Gem and Mineral Show (now held at the Red Lion Inn). In 2002, after Natassa finished her master’s degree, she went to live with family in New Jersey and look for a job in finance. Salma asked her to help at that year’s show, but Natassa was still reluctant about selling. Salma promised she only had to stand behind the booth and rely on set prices. Natassa made a good salary based on commission over the two-week show. “It took her a while, but she convinced me to join the business,” she said.
Soon Natassa started going to the opal fields with Salma and doing the smaller trade shows in Tucson. “I’m a good listener, I think,” Natassa said. “And I believe I’m a good observer. So I learned quickly. It just kind of started rolling off my tongue eventually.”
Since then, Natassa has only missed the Tucson shows twice, once while completing the Accredited Gemologist program at the Asian Institute of Gemological Sciences (AIGS) in Bangkok. “I felt that opals weren’t in the mainstream,” she said. “There was so much misinformation.” She wanted to be able to explain opal in gemology terms “because it’s this mysterious stone to most people.” She found she loved gemology and being in the lab. “I love the microscope,” she said. “It’s pretty cool to see opals under microscopes.”
True Blue’s first AGTA show was in Las Vegas in 2005. Natassa got a call on opening day offering them the booth of an exhibitor who hadn’t showed. “Back then we didn’t have any money,” she said. “We used to put stuff on credit cards.” The cost of the booth was $7,000—the cost of the entire trip. “I’m thinking, how are we going to do these two booths? Is there enough stock to spread around? Plus seven grand. Plus it’s already opening. Then we said okay—we’ll just do it.” Their first big sale that day wasn’t an opal but a giant clam (Tridacna gigas) pearl they’d bought a few days prior, for which another exhibitor paid $10,000 cash. “So we covered our booth,” Natassa said.
“We’re blessed, because there have been difficult times for us personally and financially over the last 28 years,” Natassa said. “For my mum, even more so because she was on her own before me. All these things I’ve learned from her, day in, day out.”
Natassa recalled that in the early years some customers, expecting a male dealer, would ask where the owner was. “They just assumed that we weren’t. A client would say, ‘Go ask your boss if I can get a better deal on this.’ I’d say, ‘Well, I am the boss, and this is the price.’ It’s easier now.”
Natassa and Salma try to find niches in the local market, such as opal beads (figure 4), which they began selling in the late 2000s. The beads use the precious part of the opal as well as the potch. “The really dark potch is jet black,” Natassa said. “If you can wear a black spinel strand, you can wear a potch opal strand.”

Figure 4. Faceted beads of black opal from Lightning Ridge totaling 45.15 carats. Each bead is 4 × 4 × 3 mm. Courtesy of True Blue Opals and Gems Inc.
Natassa revealed that she never intended to stay in the opal business this long. “But I think it’s God’s plan for me,” she said. “I don’t think I could do anything else.” She hopes someone in the family will take over and operate True Blue when she and her mother no longer can.
The Patels (figure 5) have been discussing what to do when they return to Australia. They have considered splitting their stock fifty-fifty between black and boulder opal. “Black will always be king of all opal,” Natassa said. “That’s our favorite. We grew up on black opal, so we can’t help ourselves.”

Figure 5. Salma and Natassa Patel of True Blue Opals and Gems at their AGTA show booth. Photo by GIA Staff. @chapter:25


Publication Year: 2007 Title: Global Rough Diamond Production Since 1870 Abstract: Data for global annual rough diamond production (both carat weight and value) from 1870 to 2005 were compiled and analyzed. Production statistics over this period are given for 27 diamond-producing countries, 24 major diamond mines, and eight advanced projects. Historically, global production has seen numerous rises—as new mines were opened—and falls—as wars, political upheavals, and financial crises interfered with mining or drove down demand. Production from Africa (first South Africa, later joined by South-West Africa [Namibia], then West Africa and the Congo) was dominant until the middle of the 20th century. Not until the 1960s did production from non-African sources (first the Soviet Union, then Australia, and now Canada) become important. Distinctions between carat weight and value affect relative importance to a significant degree. The total global production from antiquity to 2005 is estimated to be 4.5 billion carats valued at US$300 billion, with an average value per carat of $67. For the 1870–2005 period, South Africa ranks first in value and fourth in carat weight, mainly due to its long history of production. Botswana ranks second in value and fifth in carat weight, although its history dates only from 1970. Global production for 2001–2005 is approximately 840 million carats with a total value of $55 billion, for an average value per carat of $65. For this period, USSR/Russia ranks first in weight and second in value, but Botswana is first in value and third in weight, just behind Australia. @chapter:38


Publication Year: 2014 Title: Long-Term Durability of CVD Synthetic Film on Diamond Abstract: Figure 1. This 0.27 ct diamond with a boron-doped CVD synthetic diamond film on the pavilion received a color grade of Fancy Dark brownish yellowish gray. The distinct color zoning seen in this photo makes it apparent that the diamond has been treated in some way and is not a natural stone. Photo by Robison McMurtry.

In 2005, a thin film (10 µm) of synthetic diamond grown by chemical vapor deposition was deposited on the pavilion of a 0.27 ct natural diamond. The CVD layer was deliberately doped with boron to create a bluish color. No subsequent polishing was performed. Rather than blue, the resulting color was a less desirable gray. This natural diamond with CVD overgrowth was then reset in a ring and worn daily by the author for the next eight years. Recently, this hybrid diamond was removed from its setting for gemological and spectroscopic characterization and to assess the current state of the CVD film.

Well-controlled durability studies have examined non-diamond coatings on diamond (e.g., A.H. Shen et al., “Serenity coated colored diamonds: Detection and durability,” Spring 2007 G&G, pp. 16–34) and nanocrystalline diamond coatings on non-diamond materials (J.E. Shigley et al., “Characterization of colorless coated cubic zirconia [Diamantine],” Spring 2012 G&G, pp. 18–30). To our knowledge, however, none have been performed on CVD diamond films grown on natural diamond. The assessment of this one sample, given the exposure a ring is usually subjected to, can indicate the long-term stability of such coatings on diamond. The expectation was that such films would remain stable, as there is no lattice mismatch in the crystal structure between the CVD synthetic film and the natural diamond. Lattice mismatch and the resulting low cohesion at the diamond/non-diamond interface typically result in moderate to very poor durability.

It was difficult to find evidence of the CVD layer using spectroscopic techniques. FTIR absorption (which generally provides data from the bulk of the diamond) revealed no CVD-specific features, only that the underlying diamond was type Ia. Using PL spectroscopy, which collects data from a limited area, it was difficult to find spectroscopic evidence of the CVD film, even when the PL data were collected in confocal mode. No CVD-related 3123 cm–1 peak was detected in IR absorption, and the silicon peak at 737 nm was not observed in PL. The best evidence of the CVD layer’s continued existence on the diamond was from its unusual appearance in visual observation (figure 1) and microscopic analysis (figure 2). The pavilion also showed electrical conductivity, which provides another indication of the boron doping.

Figure 2. This differential interference contrast image shows the irregular texture of the CVD overgrowth film on the pavilion facets of the 0.27 ct natural diamond. Each facet is a different color, and the boundaries between colors are facet junctions. Image by Nathan Renfro; field of view 246 microns.
By examining the pavilion of the diamond at high magnification, we could assess the condition of the CVD layer after eight years of daily wear. The film was still largely intact, covering the entire pavilion and containing only a few sporadic pinholes. There was no noticeable degradation at the facet junctions. The obvious color zoning in figure 1 that appears to divide the diamond into quadrants is likely due to differences in deposition and boron incorporation rates on the various facets. Recently, the diamond was annealed twice, at 600°C and 700°C for one hour each in a reducing atmosphere, in an effort to make it appear bluer. This treatment changed the color from Fancy Dark brownish yellowish gray to Fancy Dark gray.

As treatments become more sophisticated and move from the laboratory into the trade, the need for accurate detection only intensifies. Nevertheless, such semipermanent films are identifiable and reiterate the need to use both spectroscopic and traditional methods for gemological characterization. @chapter:15


Publication Year: 1999 Title: Spring 1999 G&G Lab Notes Abstract: Alexandrite with a Fish-Eye Effect
Diamond with a Stellate Cloud
Invisible Filler in Emerald
Glass Imitation of Peridot
Jadeite with Unusual Evidence of Enhancement
Black Cultured Pearls with Surface Enhancement
Imitation Tahitian Pearls
Cat’s-Eye Taaffeite

To view the full section, download the PDF above. @chapter:17


Publication Year: - Title: Incredible Insects Abstract: View Gallery

Some have wings. Some have six legs. Some can fly. They’re insects, and they come in a stunning variety. At last count, scientists have identified more than 925,000 species of insect. They elicit a wide range of emotions in people – from repulsion to fascination – and in the hands of imaginative jewelry designers, they become majestic monarchs decorated in diamonds, rubies, pearls, and other spectacular gemstones.

Just as a caterpillar turns into a butterfly, master jewelers take raw elements and transform them into wearable works of art. Put aside whatever preconceptions you may have about insects, and prepare to step into another world – one that you have passed by countless times but may not have ever noticed.

	Bizarre Beetle
This antique (circa 1865) Egyptian scarab pendant watch is crowned with a pharaoh’s head of carved carnelian and a headdress of green and blue enameled gold. Dangling from the head is an enameled scarab with ruby eyes and diamonds set in the wings. The underside of the scarab is also realistically engraved – the finishing touches of an exceptionally complex piece.

	Photo courtesy Mona Nesseth and Michelle Laurenti

	A Pearly Caterpillar
Making a caterpillar out of pearls is a leap of creative genius. The body of this bug brooch is two large freshwater pearls that are naturally fused together (50 x 40 mm, weighing 40.4 grams) and a Keshi pearl; the head is a medium-dark gray Keshi pearl. Nine bezel-set cabochon rubies stud the body of the caterpillar. The leaf on the lower right is another freshwater cultured pearl; the leaf above it has 27 round-cut dark-green sapphires. This caterpillar is so beautiful that it doesn’t need to turn into a butterfly.

	Photo © GIA and Tino Hammid, Gift of Avi Raz, A&Z Pearls, Inc.

	Celeb Spider
Hollywood designer Tony Duquette shows how far the imagination can reinvent a common bug with his “Phoenix Spider.” With her pearled head, hanging sack, undulating golden limbs, and enamel-flecked legs, this combination brooch and pendant is a fanciful creation by the famed set designer. A goddess ready to feast or to give birth to a new brood, although not an insect, she is the queen of her realm.

	Photo courtesy The Anthony & Elizabeth Duquette Foundation for the Living Arts

	A Streamlined Moth
An Art Deco moth? Sounds strange, but that’s what you’re seeing. The layered metal gives the brooch an architectural feel of the era. The angular lines of the wings make it look as if it were in flight. The dazzling opal appears a bit surreal. So much for thinking that moths are the ugly stepsisters of the insect kingdom!

	Photo courtesy Wallace Goldsmithing

	A Praying Mantis, Immortalized in Gold
How many unusual elements are in this Praying Mantis? This objet d’art is a solid silver cast of a real Praying Mantis (a dead one was used to make the mold). This makes it an exact replica of the original. The bottom wings were made using the ancient and difficult Japanese mokume gane technique – “welding thin layers of different metals…without solder and flux.” A wood grain look is the tell-tale sign of mokume gane. The upper wings were the artist’s inspiration. Now the finished piece probably decorates someone’s desk – or is out hunting for metallic prey.

	Gift of Robert F. Officer @chapter:21


Publication Year: 2016 Title: Synthetic Quartz: A Designer Inclusion Specimen Abstract: Figure 1. A 50 × 27 × 13 mm synthetic quartz crystal in which almandine and pyrope garnets introduced during the growth process created a suite of inclusions in the lower right of the specimen within the same plane as an elongated liquid and gas two-phase inclusion. The six vertical prism faces and angled rhombohedral faces help orient the crystal and mirror those of natural quartz, but their unnatural surface features immediately give away the synthetic origin. In the foreground are approximately 2.5 mm water-worn pyrope crystals (left) and 1.5–2.0 mm dodecahedral almandine crystals (right) similar to those used as inclusions; the almandines were extracted from the schist matrix specimen shown in the background. Photo by Elise A. Skalwold.

	As interest in gem and mineral inclusions grows, the value of inclusion specimens has increased as well. This has led to the relatively recent trend of simulated inclusion specimens being offered in the marketplace (see E.A. Skalwold, “Evolution of the inclusion illusion,” InColor, Summer 2016, pp. 22–23). To the best of this author’s knowledge, the synthesis of a quartz host with inclusions—or for that matter, any type of synthetic crystal—for the express purpose of creating a collectable inclusion specimen has not yet been reported and therefore presents a very interesting project to pursue.

	Natural quartz plays host to a wide variety of inclusions, including several types of colorful garnets that often lend an aesthetic contrast to this already fascinating mineral. The author retained the services of a synthetic quartz manufacturer who refined and implemented her plan for growing four small specimens: one with pyrope garnets, one with almandine garnets, one with both types, and one without added garnets as control. The chosen garnets are brightly colored despite their tiny size and so fit with the desire to keep the finished quartz crystals small, given the long and expensive growth period required for the hydrothermal process.

	Using a five-meter-tall industrial high-pressure autoclave, several runs were completed over a four-month period. Prior to the second run, the garnets were introduced into holes bored into the quartz. A few of the garnets were thus successfully captured and incorporated within the host as the second run continued. The nutrient solution for the quartz growth consisted of approximately 10 wt.% of Na2CO3 in pure water, with many trace elements originating from the milky vein Arkansas quartz used as the silica source. To produce the desired crystal morphology, a seed with “c-a” cut was used to initiate growth vertically along the c-axis and elongation along the a-axis. Rather than being hung by wires in the autoclave, the growing crystals sit on a shelf, and hence there is no wire in the finished specimen. The growth temperature was approximately 350°C in a pressurized environment of 700-plus bars.

	When the autoclave was opened at the end of four months, four crystals of approximately the same size emerged intact, one of which is described here as representative of the entire set (figure 1). Along with “breadcrumb” inclusions familiar to gemologists, the suite of captured garnets was surrounded by unidentified white masses and radiating cracks. Quartz’s structure can be thought of as an open yet distorted framework of silicon and oxygen atoms. Because these bonds have angles that change rapidly with temperature, the volume of quartz changes rapidly with change in temperature—much more rapidly than the rather closely packed atoms in garnet. So it is not surprising that as the specimens cooled, the quartz shrank faster than the garnets, causing the quartz to fracture (figure 2). Having formed previous to the growth of the quartz that later captured them, these garnets would be considered “protogenetic” inclusions. Some liquid and gas originating from the autoclave’s environment was also captured as a two-phase inclusion running perpendicular to the c-axis of the quartz. The glassy prism faces of the crystals display characteristic diagonal striations, unlike the prism faces of natural quartz, which have horizontal striations (i.e., perpendicular to the c-axis). Originally, one of the four crystals was intended to be cut into a cabochon to illustrate a classic “rough and cut” suite, but it would have been a shame to sacrifice even one of these pristine and arguably unique synthetic quartz inclusion specimen simulants. Therefore, they will remain as they are in the author’s collection—as her own “designer inclusion specimens.”

	Figure 2. Amid a storm of breadcrumb inclusions, two orangy red almandines and two larger red pyropes caused tension cracks to form in the quartz upon cooling. Portions of a two-phase liquid and gas inclusion running nearly the length of the crystal are indicated by the large bubbles seen at the left and right edges of the image. The guest quartz crystal (part of a multiphase inclusion at right), along with the white masses accompanying the garnets, are remnants from the nutrient environment in which the quartz crystal grew. Transmitted and oblique fiber-optic light. Photo by Elise A. Skalwold; field of view 13 mm. @chapter:19


Publication Year: 2014 Title: Yellow Sapphire Filled with Lead Glass Abstract: Figure 1. This 4.27 ct sapphire was filled with orangy yellow lead glass throughout the stone. Photo by Gagan Choudhary; courtesy of Dheeraj Gupta.

              This contributor has previously reported glass-filled, color-changing red and blue corundum (Spring 2008 GNI, pp. 88–89). After recent reports of green sapphire filled with lead glass (Fall 2013 Lab Notes, p. 176) and sapphires with cobalt-colored lead glass (e.g., T. Leelawatanasuk et al., “Cobalt-doped glass-filled sapphire; an update,” Australian Gemmologist, Vol. 25, No. 1, 2013, pp. 14–20), an orangy yellow sapphire filled with lead glass was presented to us by Dheeraj Gupta (Gem & Jewellery Sales Promotion Council, New Delhi).

The 4.27 ct sapphire (figure 1) was hazy throughout, with a roiled effect reminiscent of hessonite, but standard gemological properties and microscopic analysis identified the specimen as natural corundum. It gave an RI of 1.762–1.770; a hydrostatic SG of 4.03; an absorption band at around 450 nm, along with fine lines in the red end under the desk-model spectroscope; and reddish orange fluorescence in long- and short-wave UV. The sapphire showed stronger fluorescence under long-wave UV. Microscopic examination revealed numerous low-relief cracks throughout the stone with a distinct flash effect. Also visible were trapped, flattened gas bubbles, as seen in figure 2, and whitish cloudy patches; these are typically associated with filled stones. Also present were milky zones consisting of fine discs (usually rutile) and negative crystals associated with liquid films. Under diffused lighting, the glass-filled fractures appeared orangy yellow against the pale yellow bodycolor of the stone (again, see figure 2). As a result, the face-up color also appeared orangy yellow. The color of the filler glass was similar to that observed in glass-filled rubies. The lead content of the glass was further confirmed by EDXRF analysis, while the presence of iron (the cause of the sapphire’s yellow color) was confirmed by an Fe-related 450 nm band in the UV-visible spectrum.

	Figure 2. The color of glass-filled fractures appeared orangy yellow against the sapphire’s pale yellow bodycolor; thus, the face-up color also appeared orangy yellow. Note the spherical bubbles trapped within the fractures. Also present were flattened bubbles and a typical flash effect (not shown here). Photomicrograph by Gagan Choudhary, magnified 32×.
Since this was first example of lead-glass-filled yellow sapphire examined by this contributor, its market penetration is still unknown. With its transparency and color, this material qualifies as an inexpensive substitute for yellow sapphire, provided there is complete disclosure. @chapter:12


Publication Year: 2015 Title: Assembled and Bead-Cultured Pearls Abstract: Figure 1. The 10.27 ct baroque cultured pearl exhibited a suspicious translucent ring at one end. Photo by Nuttapol Kitdee.

              A cream and white baroque pearl weighing 10.27 ct (figure 1) was recently submitted with seven other pearls to the Bangkok laboratory for a GIA Quality Assurance Report, which provides rapid identification for sorting purposes. The pearl appeared to have been assembled, as it possessed an odd translucent ring at one end, indicating where separate components had been joined together.

Prior to examination with real-time microradiography, it seemed likely that a shell bead nucleus was hidden from view, as the banded structure of a shell was observed in the translucent area when viewed with transmitted light from a fiber-optic light source. The transparent bonding agent used to join the two parts also contained black impurities (figure 2, left). Obvious gas bubbles were visible with a loupe or gemological microscope. Out of scientific interest, the pearl was also examined with X-ray fluorescence and DiamondView imaging. X-ray fluorescence showed a strong reaction in the damaged and repaired area, as would be expected because of its thinner nacre coverage. DiamondView imaging revealed the banding within the bead, the dark inclusions in the bonding agent, and the bonding agent itself (figure 2, right).

Figure 2. Left: Weak banding was faintly visible beneath the repaired and assembled area when viewed with a strong light source. Field of view 8 mm. Right: The banding was more noticeable in the DiamondView. Photo and DiamondView image by Areeya Manustrong.
Real-time microradiography revealed the bead nucleus as well as an extremely thin nacreous cap that had been used to cover the damaged bead. While X-ray computed microtomography (μ-CT) would not normally be needed to identify such an obviously bead-nucleated pearl, it was used to display the results with even greater clarity (figure 3). This analytical technique clearly showed the broken bead and an area where a new piece of nacre had been applied to repair the pearl. This would explain the mismatching translucent ring.

Figure 3. The broken bead and the nacreous cap applied to conceal the damage are clearly visible in this X-ray computed microtomography (μ-CT) slice.
This study demonstrated how the internal secrets of pearls can be revealed by a variety of techniques. @chapter:14


Publication Year: 2009 Title: Celebrating 75 Years of Gems & Gemology Abstract: Gems & Gemology, the professional quarterly of GIA, debuted in 1934. Appearing in the 306th issue, this article looks back at the first 75 years. By reviewing the journal’s milestones, it also traces the history of modern gemology, as the articles, notes, and news updates in G&G represent a virtual encyclopedia of the developments that have influenced the science into the 21st century. @chapter:20