Title: Ruby Quality Factors Abstract: Fine-color, large, and eye-clean (lacking visible inclusions) rubies like this 11.01carat (ct) stone from Myanmar (formerly known as Burma) are extremely rare and valuable. – Photo: Robert Weldon/GIA. Courtesy: Jan Goodman Co

Ruby can command the highest prices of any colored gemstone.  The per-carat prices of fine-quality rubies have been rising consistently, many times breaking auction records.

For better-quality material, slight differences in color can make significant differences in value. For top-color ruby that’s also free of eye-visible inclusions, the price rises even more.

The per-carat price of ruby can also increase dramatically as size increases, especially for better-quality stones.
The Color of Ruby

The mixture of these untreated and heat-treated rubies show a range of darker and brighter red colors. Photo: Robert Weldon/GIA. Courtesy: Tommy Wu, Shire Trading Ltd., Hong Kong
Color is the most significant factor affecting a ruby’s value. The finest ruby has a pure, vibrant red to slightly purplish red color. In most markets, pure red colors command the highest prices and ruby with overtones of orange and purple are less valued. The color must be neither too dark nor too light to be considered finest quality. If the color is too dark, it has a negative effect on the stone’s brightness. At the other extreme, if the color is too light, the stone may be considered to be a pink sapphire, even if color strength or intensity is high. That said, pink sapphires enjoy a following, at a far more competitive prices than rubies. Ultimately, the most desirable color of ruby is the one you prefer the most.
The Difference Between Pink Sapphire and Ruby
Some gem dealers debate the borderline between ruby and pink sapphire. Historically, the word ruby referred to shades of red, which technically included pink. There are also cultural differences in the interpretation of ruby versus pink sapphire. In some gem-producing nations such as Sri Lanka, pink colors were always considered ruby, while in many consuming countries it is classified as pink sapphire.

The GIA Laboratory uses a controlled set of comparison stones called masterstones to determine if corundum is ruby The laboratory grades its masterstones on the principle that red must be the dominant hue before a stone can be called a ruby. In the gem trade, though, pinpointing the dominant hue is subject to personal perception.
Burmese Pigeon Blood Ruby
Historically, the term “pigeon’s blood” described the red to slightly purplish or pinkish red color of rubies with a soft, glowing, red fluorescence.

Traditional descriptions like these are useful for evoking images and describing color among professionals. But they can be subject to misinterpretation when used to describe a ruby’s actual color.

Over time and years of experience trade terms can conjure up perceptions of certain colors and qualities that are associated with a stone’s source. However, the qualities might be typical of that source or they might represent the finest stones from that source.

A single source never yields gems that are all the same color and quality. In fact, the descriptive trade term might represent only a small, yet highly desired percentage of stones from that source.

New sources can produce material very similar to rubies from classical localities or present a slightly different appearance, but remain just as beautiful.
Ruby Clarity

Intersecting needles of the mineral rutile create a common ruby inclusion called silk. When they are intact, they prove the ruby was not heat-treated at very high temperatures. It’s still possible that lower-temperature heat treatment might have occurred. Photo: John I. Koivula, GIA.
People in the trade expect rubies to have at least some inclusions because inclusion-free rubies are practically nonexistent. Ruby value can depend on how visible the inclusions are. Obvious inclusions, or inclusions that reduce transparency or brightness, lower a ruby’s value dramatically.

If large and prominent inclusions are located under the table facet, they greatly diminish the transparency, brilliance, and value of the stone. Inclusions can also limit a ruby’s durability. Significant surface-reaching fractures can pose durability threats.

Typical ruby clarity characteristics include thin mineral inclusions called needles. When the mineral is rutile and needles are present in intersecting groups, it is called silk. Needles might be short or long and slender, and they might appear to be woven tightly together.

Ruby can also contain needles composed of other minerals, small crystals, zones of color variation, or inclusions that resemble fingerprints.

Some inclusions can actually contribute positively to a gem’s appearance. The presence of rutile silk causes light to scatter across facets that might otherwise be too dark. This adds softness to the color and spreads the color more evenly across the ruby’s crown.

Needles that intersect can also cause the star effect, called asterism, when the stone is cut with a curved upper surface, called a cabochon cut.

Long mineral inclusions that intersect can create the star effect when stones are cut as cabochons. - Photo: Robert Weldon/GIA. Courtesy: Hussain Rezayee, Rare Gems & Minerals
Ruby Cut

Rubies are commonly cut into oval and cushion shapes. – Photo: Robert Weldon/GIA. Rough: Gift of William F. Larson. Cut stone: Courtesy: Edward Boehm.
Several factors affect the cut and proportion of rubies on the market. A ruby’s crystal shape dictates its suitability for certain cuts. The most common shape is a flat tabular hexagonal shape, but ruby crystals from some sources can be elongated.

To accommodate these crystal shapes, the most common shapes of fashioned rubies are ovals and cushions, with brilliant-cut crowns of kite-shaped and triangular facets, and step-cut pavilions with concentric rows of rectangular or square facets.

Round, triangular, emerald-cut, pear, and marquise rubies are also available. But these shapes are rare in larger sizes and higher qualities.

Ruby rough is very expensive, so many cutters try to conserve as much weight as possible. They might fashion flattened ruby rough into shallow stones, even though light escapes through flattened pavilions, causing an unattractive see-through area in the stone called a window.

Pleochroism—the appearance of different colors in different crystal directions—is another factor that influences cut. In ruby it typically appears as red to purplish red in one crystal direction and orangy red in the other. Cutters can minimize the orangy red color by orienting the table facet perpendicular to the long crystal direction. Even so, it’s not always possible to orient a ruby for ideal color return because the potential loss of weight would be too great.
Ruby Size and Weight

These rubies were all mined in Myanmar (formerly known as Burma). The faceted stone weighs 11.55 carats and the rough stones weigh between 16.65 carats and 278.50 carats. Photo: Robert E. Kane/GIA.
Fine-quality rubies over one carat are very rare, but commercial-quality rubies are commonly available in a wide range of sizes. The price per carat goes up significantly for ruby as it increases in size. Source: GIA @topic:1


Title: A Study of Rubies from Cambodia and Thailand Abstract: Rough and faceted rubies from Thailand-Cambodia. The rubies in matrix are associated with green pyroxene. The faceted stones in the center weigh 2.25 and 1.62 carats. Photo by Vincent Pardieu © GIA.

Although miners have exploited ruby deposits around the Thai-Cambodian border for more than a hundred years, activity was most intensive between the 1960s and 1990s. This period coincided with a military coup in Myanmar (Burma) that made that country’s gem deposits largely inaccessible to world markets. As a result, Thailand was ideally placed to take on the mantle of the world’s premier commercial ruby source. Later in the 1990s, the Thai-Cambodian deposits became depleted and new ruby sources elsewhere came on stream. Since then, activity has declined and most mines are abandoned. Although current production is sporadic, gems from these once commercially-important deposits are present in the marketplace and in jewelry.

A new report from the GIA Laboratory in Bangkok, ‘A Study of Rubies from Cambodia and Thailand’ characterizes gems from these once prolific deposits. This study used 41 purplish-red ruby samples obtained by GIA’s Field Gemology Department in previous field expeditions: 34 from Pailin, Cambodia and 7 from Chanthaburi-Trat. The samples were fashioned to optimize them for LA-ICP-MS chemical analysis, UV-Vis-NIR and FTIR spectroscopy, and inclusion studies using microscopy and Raman spectroscopy.

Thai rubies are associated with alkali-basalt deposits in Chanthaburi, Trat and Pailin. These basalt-related gems have a very high iron (Fe) content and very low fluorescence as a consequence. Due to their high Fe content, Thai-Cambodian rubies typically have a purplish aspect, and UV-Vis-NIR spectra show a combination of both chromium and iron chromophores. To remove this purple aspect, and heal any potential fractures, rubies from these deposits are routinely heat-treated.

Minerals like diopside, negative crystals surrounded by fluid fingerprints or thin films, naturally-healed fractures, and intersecting polysynthetic twinning planes with growth tubes are among these rubies most distinctive internal characteristics. LA-ICP-MS analysis showed that comparison of gallium, magnesium, and vanadium content with the trace element chemistry of iron-rich rubies from amphibolite-related deposits is helpful for origin determination.

The authors suggest a combination of techniques—trace-element chemistry and microscopy—can readily separate Thai-Cambodian rubies from Kenyan basalt-related rubies and those originating in amphibole-related deposits. Source: GIA @topic:1


Title: Wheel of Light’s Mesmerizing Optics Abstract: The “Wheel of Light” Numinous pendant contains an 825 ct carved quartz centerpiece. Different rough gems have been placed into a channel drilled into the quartz by the lapidary artist, which was then set in 24K gold. Photo by Robert Weldon/GIA; courtesy of Nature’s Geometry.

Lapidary artist Brian Cook, of Tucson-based Nature’s Geometry, is astonished that the optical designs he has experimented with and refined for more than 25 years have finally come of age. Appreciation for his work culminated with a first-place award in this year’s AGTA Spectrum’s Fashion Forward category for his “Wheel of Light” Numinous pendant, which graces the cover of this issue.

The 825 ct quartz center stone of this piece was carved to resemble a rounded disk with a softly contoured apex, or dome. After drilling the apex, Mr. Cook carefully inserted rough crystals of Paraíba tourmaline, haüyne, ruby, and spessartine garnet. The channel was then filled with jojoba wax and hermetically sealed with a quartz plug. The trapped “inclusions” are visible if the disk is observed from the side. As the disk is turned, with the viewer gazing down the apex, an interesting optical effect is noted: The colors corresponding to the included gem rough are revealed as concentric rings. To the eye, the ringed colors appear as painterly brushstrokes. Mr. Cook explained that the quartz vessel becomes both a frame and a mirror for what the eye sees. “The colors are amplified by the quartz, reflected off its inside surface. The jojoba wax, with a refractive index close to that of quartz, causes the channel to virtually disappear. This is how the luminosity and color of the included crystals is accentuated.”

Goldsmith Paula Brent, a longtime collaborator, brings the pieces to completion. The wheels are crafted using 24K gold, which accentuates the strength and purity of the finished object.

Mr. Cook says that the work of Nature’s Geometry is futuristic and imaginative, but at the root of it is a mystical, ancient attraction to the mineral world. The company is connecting with innovative young designers and is appreciative that the “millennial” generation is affected by the beauty and power of gems and hungry for a nontraditional approach to jewelry. Mr. Cook has been involved with the exploration for and marketing of copper-bearing tourmaline from Paraíba, Brazil, since 1988, shortly after its discovery. “The rough I saw were often too small for cutting, and the material was always extremely rare. But the color was so vibrant that I kept looking for a way to bring that ‘electrifying’ color to a greater audience.”

With the Wheel of Light Numinous pendant, Brian Cook has done just that. Source: GIA @topic:1


Title: Moonstone Quality Factors Abstract: Top-quality moonstones accent this beautiful platinum and diamond pendant. Moonstone has fascinated designers and gem connoisseurs for centuries. - Courtesy David Humphrey

                      When buyers select moonstones, they look for three key factors: bodycolor (background color) and color and orientation of the sheen.

Moonstones range in appearance from semitransparent to opaque and colorless to white, with a blue, silver, or white adularescent effect. Moonstone bodycolors vary widely. They can be green, yellow to brown, or gray to nearly black. Along with adularescence, some moonstones show chatoyancy, also called the cat’s-eye effect. A few show four-rayed stars in an effect called asterism.

Color
Throughout its long history, people have agreed on the qualities that the most highly favored moonstones should display: a colorless, semitransparent to nearly transparent appearance without visible inclusions, and a vivid blue adularescence, known in the trade as blue sheen. The finest moonstone is a gem of glassy purity with a mobile, electric blue shimmer.

	Along with multiple reflections of the trade-show booth’s display lights, these moonstone cabochons show a beautiful blue sheen. - Courtesy Temple Trading Company
Bodycolor should be nearly colorless and free of any yellowish, brownish, or unattractive green tints. Adularescence should, ideally, be blue. The sheen should be centered on the top of a cabochon, and it should be easily seen from a wide range of viewing angles. If a moonstone’s adularescence is only visible within a restricted viewing range, its value drops.

	Moonstone can be found in a variety of bodycolors.
In 1997, miners in Southern India discovered a new type of moonstone with a bright green bodycolor, described as “parrot green” by the trade. Moonstone’s signature adularescence floats in this sea of green. The gem also displays a light yellow pleochroism, a term used for a display of different colors in different crystal directions.

Today’s popular moonstone color variety includes orange to yellow colors called peach.

Clarity
A good moonstone should be almost transparent and as free of inclusions as possible. Inclusions can potentially interfere with the adularescence.

Characteristic inclusions in moonstone include tiny tension cracks called centipedes. They are called this because they resemble those long, thin creatures with many legs.

	The most-typical moonstone inclusions are stress cracks that gemologists call centipedes.
Cut
Moonstone might be shaped into beads for strands, but by far the most common cutting style is the cabochon, a form that displays its phenomenal color or colors to best advantage. Moonstone cabochons are usually oval, but cutters sometimes offer cabochons in interesting shapes, such as the tapered sugarloaf—an angular cabochon with a square base.

If a moonstone is cut as a cabochon, the dimensions should be uniform, and the profile shouldn’t be too flat. Very flat cabochons don’t display sheen well and have little value.

Faceted moonstones have become increasingly common. The cut heightens brilliance and tends to hide any inclusions that might be present.

	This unusual moonstone suite employs the rose cut, a style most often seen in antique diamond jewelry. - Courtesy Akiva Gill Co.
Moonstone is popular for carving into decorative jewelry elements, such as cameos or the popular “man-in-the-moon” face that plays on the gem’s name. The uneven surface of the carving combines with the shifting adularescent sheen to create a delightfully intricate and lively effect.

Carat Weight
Moonstone comes in a wide range of sizes and carat weights. Fine-quality material is becoming scarcer in larger sizes.

	Large fine moonstone is very rare, making it relatively valuable. Source: GIA @topic:1


Title: Romancing the Source: Afghanistan Abstract: Afghanistan

	In the Panjshir Valley of Afghanistan, rugged natural beauty provides background for the equally rugged people seeking emeralds and making life-long, trusting friendships.
This series of articles and videos follows a team of GIA Field Gemologists on their travels from the mountains of Afghanistan to the jungles of Sri Lanka in search of the sources of colored gemstones and the people who pursue them. This thrilling journey will take you to remote gemstone-mining areas, where you’ll witness the extreme effort required to wrestle nature’s treasures from the earth.

The romance of a colored gemstone arises from its beauty, the exotic qualities of its source’s location, the adventure leading to its discovery, and the stories of the people who seek it. These factors have united to create the allure of gemstones through the ages, and continue to do so even in modern times.

The Panjshir River winds through the mountain pass into the Panjshir Valley, where some of the world’s most beautiful emeralds can be found. Photo by Andrew Lucas.
Emeralds from Afghanistan can rival any in the world for beauty. The exact source of these incredible stones is the Panjshir Valley. The name means “five lions,” after five highly spiritual brothers who settled in the valley in the eleventh century AD. Recent history has subjected the valley to continual war and security issues, such as the Russian occupation from 1979 to 1989 and the civil war with the Taliban from 1996 to 2001. In a five-year span, the Northern Alliance, under national hero Ahmad Shah Massoud, defeated 10 attempted takeovers of the valley by the Soviets.

The mining of emeralds and the resources gained by selling them helped the courageous people of this valley hold off the Soviet invasion. Now these green stones are helping to rebuild the area’s economy.

Emerald mining involves tunneling into mountainsides and using former military munitions to blast into the hard rock to remove emerald. The miners work under difficult conditions, and mining can only be carried out during certain months of the year. While mild winters allow for continual mining, even in the snow, harsh winters like that of 2015 stop mining operations and even lead to avalanches and deaths.

Miners who have done well over the years are now mine owners and dealers. They are very knowledgeable about the international market and sell their emeralds through markets in Dubai. Other miners digging into the hard rock where the emeralds are found hope to find the stones that will elevate themselves and their families into a better financial position. Source: GIA @topic:7


Title: San Carlos Peridot Abstract: Each year basalt-topped Peridot Mesa, on the San Carlos Apache Reservation, is a major source for thousands of carats of gem-quality peridot in sizes suitable for use in modern jewelry.  Marketed throughout the world, San Carlos material is often confused with, and sold as, peridot from localities that are better known and documented. Peridot Mesa resulted from a single volcanic eruption and basalt flow over an already existing conglomerate base; it is thought to be of late Tertiary or Quaternary age. The peridot is found in irregularly shaped nodules within the basalt. The gemological properties and color range of these Arizona gems suggest an olivine that is rich in the magnesium forsterite end member. Inclusions documented are chromite, chromian spinel, negative crystals, "lily pad" cleavages, glass blebs, chrome diopside, biotite, and smoke-like veiling. Source: GIA @topic:1


Title: Peridot as an Interplanetary Gemstone Abstract: The stony-iron meteorites known as pallasites are famed for the areas of yellowish green olivines they contain. Since the earliest description by Peter Simon Pallas in the 18th century, reference has been made to the gem-like nature of these meteorite "inclusions." Not until the early 20th century, however, was there any record of a faceted pallasitic olivine, and only recently have a handful of stones been available for gemological examination. Study of nine peridots faceted from pallasites revealed properties within the range known for peridots plus a common inclusion feature never before observed in their terrestrial counterparts. Source: GIA @topic:1


Title: Photomicrography for Gemologists Abstract: Just because you don’t see it, doesn’t mean it isn’t there.

Many areas in the jewelry industry—education, gemological research, lecturing, publication, and laboratory and inventory documentation, to name a few—either require or benefit from high-quality photomicrography. This article reviews the basic requirements of gemological photomicrography and introduces new techniques, advances, and discoveries in the field. Proper illumination is critical to obtaining the best possible photomicrographs of gemological subjects, as is the cleanliness of the photomicroscope and the area around it. Equally as important is an understanding of the features one sees and the role they might play in the identification process. This article is dedicated to Dr. Edward J. Gübelin, one of the great pioneers of gemological photomicrography and the first gemologist to truly appreciate the unparalleled beauty of gems in nature’s microcosm. Source: GIA @topic:7


Title: Yellow Sapphires with Unstable Color Abstract: Figure 1. Left: Before a fade test, this approximately 10 ct sapphire displayed a strong orange hue. Right: After the fade test, the orange color became less pronounced and the stone appeared yellow. Photos by Ronnakorn Manorotkul.
In recent years, one concern our laboratory has heard from clients and from other gemologists is the issue of color stability in corundum. Some sapphires, particularly those with a strong yellow component (including padparadscha sapphire), contain unstable color centers that may fade when the stone is exposed to light and/or heat (K. Nassau and G.K. Valente, “The seven types of yellow sapphire and their stability to light,” Winter 1987 G&G, pp. 222–231). We regularly test for this in the laboratory by conducting a fade test. Most of the sapphires we encounter that have an unstable color are unheated stones.

Figure 2. A cluster of glassy discoids suggests that this sapphire has been heat treated. Photomicrograph by E. Billie Hughes; field of view 4.0 mm.

Figure 3. This small crystal with a melted appearance provides evidence that the specimen has undergone heat treatment. Photomicrograph by E. Billie Hughes; field of view 3.5 mm.
Recently an orange sapphire of approximately 10 ct was submitted for testing (figure 1). Microscopic examination revealed signs of heat treatment, with partially dissolved silk, several glassy discoids (figure 2), and melted crystals (figure 3). A fade test was conducted by placing the stone approximately 5 cm under a 120-watt incandescent spotlight for at least an hour, and a dramatic difference was observed. The color had changed from orange to a vivid yellow (again, see figure 1).
Under normal conditions, high-temperature heat treatment (at least 1200–1300°C) will bleach any color centers that might be present. This suggests that the orange color was activated after the heat treatment. It is possible that this occurred either by subjecting the stone to artificial irradiation or by placing it in sunlight (Nassau and Valente, 1987). However, we are unable to state definitively what process was used to activate the orange color.

Figure 4. Before a fade test, the unheated sapphire of approximately 18 ct displayed a highly saturated yellow hue (left). After a fade test involving light and mild heat, the color faded to a pale yellow (right). Once the stone was exposed to sunlight for 30 minutes, the more intense yellow color displayed before the fade test came back. The sapphire was then subjected to a light-only fade test, and the more saturated yellow color remained stable. Photos by Ronnakorn Manorotkul.
Several weeks later, we tested another yellow sapphire of approximately 18 ct (figure 4). In this instance, the stone’s features were consistent with those of unheated sapphire. Again, a fade test was performed with the 120-watt spotlight, which mildly warmed the stone to approximately 100°C. Its color also faded after the fade test, and the owner was informed. The owner explained that they had previously put the sapphire in direct sunlight, which would have brought the color back to what was likely its stable state, a process described by Nassau.
To test this, we placed the stone in direct sunlight for 30 minutes, and the more intense yellow color did return. Unfortunately, placing the gem in direct sunlight behind a window in our office did not have the same effect.
Upon seeing the color return after being placed in direct sunlight, we decided to try another fade test, this time using a light source that would not warm up the stone. An XD-300 xenon light source was used, and the stone was placed within 5 cm of a fiber-optic light guide connected to this source. After exposure to this cooler light source for over an hour, the color did not fade. This suggests that the mild heat of the 120-watt spotlight, not just the light, faded the stone’s color and that the more intense yellow color displayed after exposure to sunlight could indeed be considered the stable color.
We have since adjusted our fade tests to be light-only by switching to this cooler light source to avoid the heat generated with the 120-watt spotlight.
Our experience with these sapphires has been a fascinating case study in the color stability of yellow sapphire. This example reinforces the importance of considering all possibilities when testing stones in the laboratory. We do not fully understand the exact causes of these changes, and much remains to be learned. Source: GIA @topic:3


Title: Tsavorite Garnet and Mahenge Red Spinel Abstract: Figure 1. Daniel and Andre Assaf of the Tsavorite Factory explained the current market for tsavorite. Photo by Duncan Pay/GIA.

At GJX, Daniel Assaf (The Tsavorite Factory, New York City; figure 1) explained the current market situation for tsavorite garnet, Tanzanian red to pink spinel, and yellow danburite. According to Assaf, the recent recession and the ensuing disruption in supply had less of an impact on his business than increasing demand from China. For him, current rough scarcity and high prices relate more to the growth in the Chinese jewelry market, which 5 to 10 years ago was a fraction of its size today.

Assaf explained that both tsavorite and spinel are rare stones, and even minor changes in the market might have a considerable impact. If just a fraction of one percent of Chinese consumers becomes interested in tsavorite, this has a measurable consequence for supply, especially if production in mining areas is static or even showing slight declines. According to Assaf, the biggest tsavorite purchasers at the source in Arusha, Tanzania, are Sri Lankans buying for the Chinese domestic market. These buyers are prepared to pay very high prices for tsavorite rough.

	The Tsavorite Factory

Daniel Assaf of the Tsavorite Factory provided a detailed market update for tsavorite garnet. In this interview, he explains how unprecedented Asian demand for this rare gem has drastically affected availability and pricing for his customers.
To illustrate the sporadic nature of current supply, Assaf cited a bright, light-toned green grossular garnet. This material has become popular and is sold as “Merelani mint” garnet. It is usually recovered as a byproduct of tanzanite mining. Every so often, he related, miners find a productive pocket and buyers fly in within a couple of weeks.

According to Assaf, the stones on the tray in front of us (figure 2) were from the latest small pocket and had been in the ground just a few months earlier. After the initial flurry of buying activity, Assaf said, it might be another year or two before a similar discovery. In the meantime, the miners might bring buyers the occasional stone—at much higher prices.

Figure 2. These light-toned Tanzanian grossular garnets—termed “Merelani mint”—were mined just a few months prior to the Tucson show. Photo by Duncan Pay/GIA; courtesy of
Tsavorite Factory.
In Assaf’s opinion, today’s tsavorite rough prices in Arusha are almost “out of control.” In effect, there is a disconnect between the Arusha prices and the prices in Tucson, which will likely take several years to readjust.

His company stops buying before the Tucson show because the clientele here will not pay the high asking prices. He cited an instance several weeks earlier in which buyers were offering him top-quality rough for approximately $10,000 per stone, in sizes sufficient to cut 3 ct finished gems. A stone cut from this rough would have a per-carat price well above what the market at the Tucson show would pay. Besides the high asking price, Assaf said there is a significant element of risk in buying rough: “You never know what kind of unpleasant surprises you might find.”

He pointed out that there are places in the world where such high prices are accepted—China and possibly parts of Europe—which is why the few fine rough tsavorites that become available every month are snatched up. Assaf had just heard of a 7-gram piece of tsavorite—perhaps suitable for a 10 ct finished gem—that sold for $200,000 in Arusha.

Assaf showed us two examples of the finest tsavorite colors. In his opinion, both are of equal merit (figure 3, left). Some clients love the deeper, darker color, while others prefer a brighter, lighter-toned green. In either case, he said, the most important consideration is to have a blue color component rather than a yellow one. As long as the gem is not overly dark, and has a bluish cast to the green, it is a quality stone. If it is pale but still has a bluish component to the green, he would classify it as a “mint” garnet.

Figure 3. Left: Some prefer tsavorite garnets with a brighter color, while others prefer a darker appearance. The stone on the left weighs 9.50 ct. Right: This suite of three pear-shaped tsavorites totals 37.79 carats. The approximate asking price for such fine gems would be about $15,000 per carat. Photos by Duncan Pay/GIA; courtesy of Tsavorite Factory.
We asked Assaf how recent Chinese demand has affected tsavorite prices. He said that for sizes under 2 ct, prices have increased as much as 30–40%. The impact has been most dramatic in larger stones: For gems larger than 3 ct, prices have tripled. He felt that prices for large tsavorites have gone up in relation to emerald and other gems due to scarcity of supply and high demand.

To emphasize the point, Assaf chose a suite of three tsavorite pear shapes totaling 37.79 carats (figure 3, right). Each gem was above 10 ct and of the highest clarity, so they constituted exceptionally rare material. Aside from these standouts, Assaf admitted he had few stones of such size—large stones are typically a Tsavorite Factory specialty—due to the prohibitively high price of rough. He lamented that with today’s stratospheric prices, he would have to pay around $200,000 to obtain another 7-gram piece to cut another 10 ct gem. And very few clients—likely none at this show—would accept the resultant high per-carat prices for the finished gem. That leaves two possibilities: Either the prices will adjust in Arusha, or they will become accepted in the U.S.

Assaf recounted that some of the same market factors apply to red spinel. His company does not carry spinel from Myanmar, focusing instead on Tanzanian material. This year, he said, a specific color people were calling “Mahenge”—deep pink with a touch of orange, almost like a “padparadscha” color—was in extremely high demand (figure 4). Assaf had sold all of his “Mahenge” spinel but none of the other colors. While these lavenders, blues, and mauves are quite beautiful and competitively priced at around 10% of the pinks, the red to pink spinels are what his clients seek. Assaf also mentioned that buyers looking for something unusual picked yellow danburite from Tanzania, and that this gem had sold quite well for him at the show (Summer 2008 GNI, pp. 169–171).

Figure 4. An example of “Mahenge” spinel from Tanzania. This was one of the few examples left at Daniel Assaf’s booth at the time of our interview. Photo by Duncan Pay/GIA; courtesy of Tsavorite Factory. Source: GIA @topic:1


Title: Decades-Old Synthetic Alexandrite Sheds Light on Modern Research Needs Abstract: Figure 1. These rough and faceted synthetic alexandrites, grown by Creative Crystals Inc., are shown in daylight (blue-green, top) and incandescent light (bottom). The crystals were grown on seeds parallel to the b pinacoid (1, 2), parallel to the r prism (3, 6) or parallel to the l dipyramid (4); the 13.49 ct faceted synthetic alexandrite measuring 16.6 × 11.8 mm (5) was grown on a seed parallel to the r prism. Photos courtesy of K. Schmetzer, The Journal of Gemmology.

                      For decades, much attention has been given to provenance studies of natural colored gemstones (such as emerald, ruby, and sapphire), as knowing their place of origin is significant in valuation. Synthetic colored stones do not command the same price per carat as their natural counterparts, but being able to pinpoint the growth technique and possibly the manufacturer is of value to the jewelry consumer, researcher, or collector. For example, many flux and hydrothermal producers can command a premium for their “luxury synthetics” over more quickly grown flame-fusion or Czochralski crystals.

The synthetic alexandrite produced by Creative Crystals Inc. from 1971 to the early 1980s exhibited true red-green color change (figure 1), and with no production for the last 30 years, these specimens are a rarity. A recent study by Karl Schmetzer, Heinz-Jurgen Bernhardt, and Thomas Hainschwang (“Flux-grown synthetic alexandrites from Creative Crystals Inc.,” The Journal of Gemmology, 2012, Volume 33, Number 1–4, pp. 49–81) goes into fascinating detail on the company’s history, how the seed crystals were generated, and how the crystals were grown, unlocking the mystery of the distinct growth zoning observed in these particular synthetics.

The authors’ diligence in collecting a highly representative group of samples of this out-of-production material, as well as their thorough review of the available literature, is commendable. Woven into the article are interesting tidbits about the various seed origins and orientations used for growing these alexandrites, which demonstrates how both practical considerations and research-based findings can influence production and ultimately quality. A highlight of the article is the two-page history recounted by David Patterson, a former owner of Creative Crystals Inc.

	Figure 2. This microphotograph shows layered growth zoning associated with intense color zoning in a faceted synthetic alexandrite grown by Creative Crystals Inc.; immersion, field of view 5.3 × 4.0 mm. Photo courtesy of K. Schmetzer, The Journal of Gemmology.
To capture the uniqueness of these synthetics, the authors conducted meticulous microscopic studies. Several other techniques—including X-ray fluorescence, electron microprobe, and ultraviolet through infrared absorption spectroscopy—were used to describe corresponding chemical and optical zoning, pleochroism, absorption bands, and inclusions. The authors draw clear correlations between growth parameters and crystal characteristics, such as the impact of seed orientation on morphology. Even more significantly, they link the previously unexplained internal growth bands (figure 2) to multiple growth cycles – the growing crystals were actually removed from the furnace repeatedly to assess their progress. Similarly, I.G. Farben grew synthetic emeralds in the 1930s using multiple growth cycles (Karl Schmetzer, Lore Kiefert, “The colour of Igmerald: I.G. Farbenindustrie flux-grown synthetic emerald,” The Journal of Gemmology, 1998, Volume 26, Number 3, pp. 145-155). However, Creative Crystals would cool the melt slightly during cycles lasting one week whereas I.G. Farben would keep the melt at a constant temperature during 20-day cycles.  Using a temperature gradient to grow synthetic alexandrite was not practiced for several more years (Karl Schmetzer, personal communication). A comparison with commercially produced flux alexandrite from Russia also illustrates how characterization techniques can reveal details of the growth process.

The article is not a light read, 33 pages in length with 46 figures and well over 100 images. But for crystal growers or those simply interested in understanding more about gem synthesis, this article serves as a window into the crystal growth engineering process, and how a specimen’s characteristics can shed light on its origin. Other synthetic materials have been similarly studied, and the need for such analyses continues to increase as additional synthetics and more advanced characterization techniques emerge. Source: GIA @topic:3


Title: Seeing Green: All About Emeralds Abstract: Emeralds are formed when chromium, vanadium, and iron are present in the mineral beryl. The varying presence of these three elements gives emerald its range of color. Chromium and vanadium make an intense green color. Iron gives the stone a bluish tint. Courtesy of Bill Larson, Palagems.com.

                      Want to see into the future? Be an eloquent speaker? Defeat spells and enchantments?
Such is the lore of the emerald.

The first known emerald mines were in Egypt, dating from at least 330 B.C. into the 1700s. Cleopatra was known to have a passion for emerald, and used it in her royal adornments. 16th-century Conquistadors discovered South American mines hidden by the Incas. A ready and exceptional supply of emeralds was suddenly available, and Europeans fell in love with the bewitchingly beautiful gemstone.

Some 500 years later, emeralds are still enchanting us. Emerald is the birthstone for the month of May because its color symbolizes the rebirth and renewal that comes with spring. Pantone named it the Color of the Year for 2013 because of the “luxury and elegance (it brings) to the palette.”

Emeralds are formed when chromium, vanadium, and iron are present in the mineral beryl. The varying presence of these three elements gives emerald its range of color. Chromium and vanadium make an intense green color. Iron gives the stone a bluish tint.

The most valuable emeralds are bluish-green to green and have a medium to medium-dark tone. Since emeralds typically form in six-sided prisms, they are naturally suited for, and often shaped into, the emerald cut.

Most emeralds have inclusions (internal clarity characteristics) and blemishes (surface clarity characteristics) that can be seen with the unaided eye. The size and types of inclusions greatly affect price: from $10 per carat for a small low-quality stone, to $50,000 per carat for an exceptionally clean stone.

So how hot are emeralds? Harry Winston sold a pair of circular clip earrings with 6.91 ct. and 7.32 ct. round emeralds for a cool $218,000 in November 2012. Brooke Astor’s 22.74 ct. emerald engagement ring went for $1.2 million at a recent Sotheby’s auction. Source: GIA @topic:3


Title: A Useful Technique to Confirm the Hydrophane Nature of Opal Abstract: With the emergence of opal production in Wollo, Ethiopia, the supply of hydrophane opal has increased significantly. This deposit offers beautiful material at a fraction of the price of similar-looking opal from several other sources, including Australia and Brazil. However, most of the opal from Wollo is hydrophane, which simply means it is porous enough to readily absorb water, much like a sponge. This property can occasionally cause durability issues that may lead to significant cracking, depending on the porosity of the material and how included it is. In general, it is difficult to predict if this material will crack when immersed, but the potential is certainly higher in hydrophane opal than in nonporous material. In hydrophane opal with a bodycolor other than white, there is the distinct possibility of artificial coloration, since stones that absorb water also absorb dye (N. Renfro and S.F. McClure, “Dyed purple hydrophane opal,” Winter 2011 G&G, pp. 260–270). While this ability to absorb water is not proof of dye, it calls for extra caution when examining an opal for color modification, especially if it has a bodycolor that can exist naturally, such as orange.

With white or colorless opals, checking for dye is not necessary, but the gemologist may find it valuable to determine if they are hydrophane so the client can be warned to avoid immersing them in liquid. Micro inclusions often present in these stones are sometimes the source of minute internal cracks. When these opals are saturated with water, the cracks often enlarge due to the strain and propagate through the entire stone. In these cases, the only option is to recut several small stones from the broken fragments.

	This Ethiopian hydrophane opal with a small crack was examined at 15× magnification in reflected light (A). The lighting environment has been changed to direct transmitted light or brightfield illumination by opening the baffle in the microscope well (B). A drop of water placed on the surface (C) and absorbed by the stone creates an optical aberration (D) that confirms the opal’s hydrophane nature. Note that the water has also produced a more pronounced optical aberration in the crack. Photos by Nathan Renfro.
To safely determine if an opal is hydrophane and avoid further propagation of existing cracks, the stone should be examined using a standard gemological microscope and direct transmitted light (with the microscope in brightfield mode). Simply place a single drop of water on the surface and observe how the water drop interacts with the opal. After a few seconds of allowing the water to either evaporate or soak into the stone, reexamine the appearance. If the water is absorbed into the stone, that area’s refractive index will be slightly different, creating an optical aberration where the drop is placed and confirming that the stone is hydrophane. This method poses less risk of breakage than complete immersion. Source: GIA @topic:11


Title: Sapphire Series Part 2: The Next Generation of Sapphire Crystal Growth Techniques Abstract: Figure 1. These photos show flame-fusion synthetic sapphire crystals, as-grown (left) and during growth in the furnace (right). Courtesy of Hrand Djevahirdjian, SA.

                      Previously we touched upon the basic science of sapphire—its mineralogy, chemistry, and physics—and also its appeal as a gemstone and in some industrial applications. Having looked at the first breakthroughs in synthesis, we now turn to the next generation of growth techniques developed to meet the demand for larger, more perfect crystals. As mentioned, much of the sapphire grown by the early flame-fusion method is used as high-purity feedstock for these advanced growth techniques (figure 1).

Bulk sapphire crystals are industrially produced using various methods and can be summarized broadly as either solution- or melt-grown. Solution growth involves using solvents such as water (hydrothermal) or other chemicals (flux) to create the crystal at a temperature below its melting point. Melt growth is achieved by bringing the Al2O3 all the way to its melting temperature (2040°C) in a crucible. Starting with a specifically oriented seed, a large crystal is formed either by pulling out a portion of the melt or by directionally cooling (gradient freezing) the melt in the crucible. Melt techniques are the focus here, as industry demands large, specifically oriented crystals. We will explore two pulling techniques, two gradient freezing techniques, and one hybrid.

In 1960, the Czochralski growth technique, a method introduced in 1918 that involves rotating and pulling a crystal out of a molten solution in a crucible, was first applied to sapphire. This technique is still very significant today for sapphire and a wide variety of other crystalline materials (including silicon) because it can produce some of the highest-quality crystals in terms of both purity and defects. The quality of these products stems mainly from the precisely controlled growth rate, made possible by carefully adjusting the power required for heating based on a mass-controlled feedback loop. Another factor that makes the Czochralski technique so invaluable is the ability to control the distribution of intentionally added impurities in “doped” crystals. This is accomplished by removing only a fraction of the molten solution rather than freezing the entire melt (figure 2).

	Figure 2. A Czochralski-grown synthetic ruby crystal is shown alongside a fabricated piece (left), and during removal from the growth station (right). Photos by Jennifer Stone-Sundberg.
In 1962, the edge-defined film-fed growth technique was first applied to sapphire. This allowed for the production of tubes, sheets, and other highly specified profiles by pulling the sapphire melt through a shaped die. As the demand for protective sapphire windows increases for a wide variety of end uses, this technique will continue to be refined (figure 3). The next part of the series will describe these applications more fully.

	Figure 3. Shown here are synthetic sapphire sheet crystals from edge-defined film-fed growth (left) and a growth machine that uses this technique (right). Photos courtesy of GT Advanced Technologies.

In 1964, Khachik Bagdasarov introduced a unique gradient-freeze technique in which the crystal is frozen from one side of the crucible to the other: the horizontal directional solidification method. Prof. Bagdasarov still uses this process to produce sapphire and other crystals. In 1967, Frederick Schmid introduced another gradient-freeze technique, the heat exchanger method, for making large ingots of various crystals (figure 4). This technique has yielded some of the finest optical-quality sapphire and is now owned by GT Advanced Technologies, which produces furnaces based on this technique under the brand name Advanced Sapphire Furnace.

	Figure 4. The two crystals on the top left were grown by the heat exchanger method, using the growth equipment pictured on the top right. A schematic of the growth process is shown on the bottom. Courtesy of GT Advanced Technologies.
The Kyropoulos growth method, which combines aspects of both the Czochralski and gradient-freeze techniques, was first applied to sapphire in 1980. Similar to the Czochralski technique, this method involves rotating a seed in contact with the melt, but the crystal is not pulled out of the melt. Instead, the melt inside the crucible is cooled in a very controlled fashion. The Kyropoulos technique has gained widespread use because of its ability to produce extremely large (up to 100 kg) high-quality sapphire crystals (figure 5).

	Figure 5. This crystal was grown by the Kyropoulos method, using the equipment shown on the right. Courtesy of GT Advanced Technologies.
Beyond timepiece bearings and scratch-resistant watch faces, what are the high-tech applications of sapphire? These uses, which capitalize on the material’s desirable mechanical, optical, physical, chemical, and structural properties, will be discussed in the third part of this series. Source: GIA @topic:3


Title: What Possesses Bidders at Auction? This Article Offers Some Clues Abstract: J. Spann and G. C. Spann. “The Heritage Auction of the Hoppel Collection,” Rocks & Minerals, Vol. 88, No. 6, Spring 2013, pp. 14–15. Photo courtesy of Heritage Auctions, HA.com.

              Auctions of world-class diamonds and colored stones have made headlines around the world, with prices reaching the tens of millions for some top rarities.

What is it about the auction process that spurs buyers to keep waving their paddles long after a particular piece has exceeded the recommended price tag? Jim and Gail Copus Spann’s article on the auction of the Hoppel Collection gives some insight into how this can happen.

The sale of the Hoppel mineral collection was held at Heritage Auction Galleries in Dallas on June 2, 2013. According to the authors, the name Hoppel was a pseudonym for a “serious collector of rare minerals” who did not want his identity known.

This article, like many auctions, makes us wait a bit for the good stuff. The first couple of pages are taken up with the arrival of the catalog, the meet-and-greet at the previews, and buyers’ wishful thinking that some of the lots being offered without reserve prices may go for bargain prices (the first clue to the auction mentality). This otherwise bland section is richly illustrated with images of some significant pieces from the sale.

The excitement kicks in when the authors, who were active buyers in Dallas, take their place in the audience and the bidding commences. We’re there, scoping the audience. We size up the buzz, who’s in and who’s out. We hear the grumbling from bidders who got outbid—and know that they’re just waiting for the moment to strike. And suddenly the price is way past what anyone planned to spend. Do we stay in? Do we really want this thing? How high can it go?

The sale’s costliest item was a large smoky quartz crystal enmeshed within folds of rose quartz, standing at a height of 39 cm, found in Minas Gerais, Brazil. Bidding started at $100,000 but quickly reached $350,000 (the pre-sale estimate). The final selling price landed at $660,000.

In the end, there were few bargains in the $3 million auction, but the authors believed the prices were fair and restored a sense of price transparency that is often lacking. Source: GIA @topic:8


Title: Sweet Home Mine Rhodochrosite from 1888 Abstract: A 7.94 ct rectangular step-cut rhodochrosite from the Sweet Home mine in Colorado’s Alma Mining District. Photo by Robert Weldon; courtesy of Barker & Co.
At AGTA, Ann Barker and Tori Lopez of Barker & Co. (Scottsdale, Arizona) exhibited a 7.94 ct rectangular step-cut rhodochrosite (see above) with a provenance dating back more than a hundred years. The stone is from the Sweet Home mine in Colorado’s Alma Mining District, at an elevation of about 3,300 m in the Rocky Mountains.
Sweet Home was established as a silver mine in 1872. Miners initially discarded most of the rhodochrosite found in association with the silver ore because it interfered with the amalgamation process used then in silver mining. But the large, highly saturated, and nearly perfectly formed crystals later discovered there are some of the world’s finest rhodochrosite specimens.
Rhodochrosite was first described in the mineralogical literature in 1813 based on specimens from what is now Romania. In 1887, George F. Kunz wrote of gem-quality rhodochrosite in Colorado, noting it was the first source with such large and transparent crystals. Most of the rhodochrosite available worldwide was light pink, opaque, and often banded—typically used for beads, cabochons, and carvings. This source introduced pink to red gem-quality single-crystal rhodochrosite, which is rare. The gemstone became more widely known in the late 1930s, after a German gemologist found large volumes in Argentina’s Catamarca Province high in the Andes. (In Argentina, the use of rhodochrosite dates back to the ancient Incas, who are said to have believed it was the solidified blood of their fallen rulers.)
The step-cut stone’s traceable history began in 1888, when a shaft collapse resulted in a 32.61 ct cleavage fragment. Miner Edward Abbott kept it and in 1925 gave it to Denver businessman Edwin Spray, who later owned the mine. The same year, Sweet Home miners found large specimens on quartz matrix, many of which were sold to museums in the U.S. and Europe. In 1968, the fragment made its way from Spray’s widow, Eleanor, through a friend of the family to geologist and mineral collector Charles Trantham in California. In 1981, Glenn Vargas, a gem and mineral dealer and university instructor, expertly cut the stone. Rhodochrosite often presents challenges for cutting due to its low hardness (3.5–4.0 on the Mohs scale) and perfect rhombohedral cleavage.
Rhodochrosite mining at Sweet Home expanded significantly in 1991—long after silver production ended in the 1960s—when Eleanor Spray’s nephew, F. Leonard Beach, leased the property to a group of investors led by Collector’s Edge Minerals. The group found several new pockets and in 1992 uncovered the Alma King, a 14.2 × 16.5 cm deep cherry red rhombohedron, the world’s largest known fine rhodochrosite crystal.
The Sweet Home mine closed in 2004, but the group went on to develop the associated Detroit City mine, which has produced some fine specimens since 2019. Source: GIA @topic:1


Title: Book Review: Ruby Abstract: By Joanna Hardy, 368 pp., hardcover, illus., publ. by Thames & Hudson, New York, 2017, US$125.00.

With its deep crimson color and bold gold lettering, Ruby stands out on a bookshelf, much as a piece of fine jewelry catches attention in a room. This eye for design continues inside the beautifully laid-out volume, with plenty of examples of important ruby jewelry and the powerful people who have worn them throughout history.

Ruby begins with a section on spinel, which has been confused with ruby in the past. This is a nice touch, because any historical account of ruby would be incomplete without the mention of spinel. Author Joanna Hardy goes on to describe ruby and its properties. However, it must be emphasized that, by the author’s own admission, this book is not meant to be a gemological text. In fact, the gemological information is brief and in places contains minor errors. For example, the fluorescence in rubies is attributed to different levels of chromium without a clear explanation of how iron content has a strong influence on a ruby’s fluorescence and overall appearance.

Hardy’s strength is in talking about rubies’ historical impact and in explaining the significance of prominent pieces of jewelry, and much of the book is devoted to this. The sections cover a wide range, from older royal collections to modern pieces worn by 20th century celebrities such as Grace Kelly and Marlene Dietrich. They provide a wonderful overview of how rubies became a symbol of power and influence. There are numerous illustrations both of the jewels, such as the legendary Nga Mauk ruby, and the people who owned these storied pieces

Following this topic, the book covers some of the techniques used by jewelry designers from the classic houses of Cartier and Van Cleef & Arpels to more contemporary designers like Wallace Chan. Again the author plays to her strengths, sharing insights from her experience as a jewelry expert.

In the final sections Ms. Hardy provides a charming travelogue of her own visits to the world’s most important ruby mines, which she took in preparation for writing this book. I particularly enjoyed following the journey of a ruby crystal sourced from artisanal miners in Mogok, Myanmar (formerly Burma) from rough into a piece of finished jewelry.

Readers should not expect a gemology textbook when purchasing this volume. Instead, it reads like a gorgeously illustrated art history guide. Although Ruby can be read cover-to-cover, it is presented in sections that can stand alone, making it an ideal coffee table book to pick up and read at leisure. I found myself skipping forward to sections that I was most curious about, which works well with the format.

This luxurious tome will broaden your gemological background, explaining the historical and cultural impact of ruby and how it has earned its title as the king of gems. It would make a wonderful gift for anyone with an interest in ruby, and an especially nice accompaniment to a piece of ruby jewelry. Source: GIA @topic:6


Title: Books: Van Cleef & Arpels: Treasures and Legends Abstract: By Vincent Meylan, hardcover, 344 pp., publ. by Antique Collectors Club, 2014, $95.00.

Van Cleef & Arpels: Treasures and Legends by Vincent Meylan delves into the glittering world of the venerable Parisian jewelry firm. Meylan explores the glamorous and exotic patrons who commissioned and collected these pieces, and the world in which they lived. Each chapter of Treasures and Legends is filled with both color and black-and-white photos of necklaces, rings, bracelets, brooches, and earrings. Some images show the firm’s pieces as worn by many of the prominent collectors over the past century. The original design sketches often accompany photos from the VC&A archives.

History buffs will enjoy the stories of royalty, particularly the maharajas and maharanis of Baroda (now Vadodara), India. The vast wealth of jewels that were collected in the Indian principalities is legendary, and Baroda, in Gujarat, was one of the wealthiest. The three-tier great ceremonial diamond collar necklace of Baroda, one of the crown jewels of the state, was made for Maharaja Khanderao in 1864. The necklace contained three of the world's most important diamonds: the Dresden Green, the Star of the South, and the Eugénie. At the time of its creation, it was the most valuable piece of jewelry in the world. The author traces the history of these and other magnificent jewels of Baroda, as well as the colorful and sometimes tragic stories of their owners, such as Maharani Seta Devi of Baroda. With India's independence in 1947, many maharajas had to sell their treasures to sustain their large homes. Seta Devi moved to Paris instead, where she was known for lavish parties and extravagant living. But eventually her money ran out, her beloved son was murdered, and she died in obscurity in 1989.

Other royal stories involve the coronation and crown jewels of the Shah of Iran, as well as the coronation crown of his third wife, Farah Diba. Intimate family photos and sumptuous coronation images highlight the story of the firm’s greatest commission. A first-hand account by Pierre Arpels adds to the interesting narrative of this journey to create these royal treasures. The Duke and Duchess of Windsor’s famous love affair was documented by many of the pieces of jewelry that he purchased for her at the great jewelry houses of Paris. The Duchess is seen wearing their pieces in many candid photos of them in social settings. Their wedding day photo shows the Duchess wearing her wedding gift: a large sapphire and diamond Mystery-set Jarretière bracelet from Van Cleef & Arpels.

Meylan also explores the role VC&A played in the world of Hollywood royalty. Marlene Dietrich was seen wearing her large ruby and diamond Jarretière bracelet in more than one film. At her death, Elizabeth Taylor’s estate contained more jewelry pieces from Van Cleef & Arpels than from any other jewelry house. Several of her impressive pieces are displayed in this book, and with them their stories of love and passion that defined Taylor’s life. Meylan names other luminaries, such as Barbara Hutton and Grace Kelly, as fans of the jewelry house.

The book ends with a chapter on the personalities in the family, including founders Esther Arpels and Alfred Van Cleef, their daughter Renée Puissant, and Esther’s brothers Charles, Julian, and Louis Arpels. Puissant in particular plays a fascinating role in the company’s history, becoming the artistic director of the firm in 1926. In the 1930s, under her direction, some of the firm’s most iconic pieces, including the “Mystery Setting” and the “Zipper Necklace,” are created. Van Cleef & Arpels: Treasures and Legends takes the reader on a historical journey filled with stunning pieces and interesting characters throughout the world—characters connected with a golden thread, their love of the beautiful art of Van Cleef & Arpels. Source: GIA @topic:6


Title: Tenebrescent Zircon Abstract: Figure 1. This 13.16 ct zircon is shown before (left) and just after 30 minutes of short-wave UV exposure (center). The SWUV lighting darkened the stone, while darkness restored the orange color. The image on the right shows the color of the stone after it was left in the dark for three weeks. Photos by Sasithorn Engniwat.

              The Bangkok laboratory recently received for identification a 13.16 ct reddish orange stone, submitted as tenebrescent zircon (figure 1, left). Standard gemological testing indicated typical properties for the stable form of zircon: RI was over the detection limit of the standard refractometer, SG was approximately 4.50, and the sample was inert to both long- and short-wave UV. After exposure to short-wave UV for approximately 30 minutes, however, its tone became darker. Chemical analysis using EDXRF showed significant amounts of zirconium and silicon, as well as a trace amount of hafnium.

Tenebrescence, the phenomenon of reversible photochromism, is common in gemstones such as hackmanite (a variety of sodalite) but unusual in zircon. In September 2011, GIA examined two zircons from central Australia that turned orange in darkness and faded to near colorless when exposed to light (S.F. McClure, “Tenebrescent zircon,” Winter 2011 G&G, pp. 314–315). This zircon displayed a different phenomenon: Its reddish orange color did not fade under fluorescent lighting or fiber-optic light. Exposure to short-wave UV (SWUV) caused it to darken. The reddish orange component gradually diminished, and the stone appeared brown (figure 1, center). There was no further change after 30 minutes.

The UV-visible spectrum after SWUV exposure showed a significant increase in absorption in the 590–750 nm range, reducing transmission of the orange to red color and making the stone darker (figure 2).

	Figure 2. After 30 minutes of SWUV exposure, the zircon’s absorption spectrum revealed more absorption in the 590–750 nm range, which relates to an orange to red color.
As noted above, the reaction is reversible. The reddish orange color returned when the stone was stored in the dark at room temperature (see figure 1, right). The color change was obvious in the first 10 to 20 hours. After that, no further color change was observed.

To determine whether the process was repeatable, the stone was again subjected to SWUV. Once again the reddish orange color darkened in tone.

In summary, the reddish orange zircon was darkened by short-wave UV exposure, and the color returned when the stone was stored in the dark. The darkening reaction was much faster than the recovery. Further studies incorporating other conditions that might affect the rate of color modification in tenebrescent zircon are being conducted. Source: GIA @topic:3


Title: Futurescape Forum Abstract: The 2018 Symposium’s finale, the Futurescape Forum, brought together six industry leaders in a panel discussion moderated by Dr. David Ager, managing director of executive development at the Harvard Business School. The panelists were Bruce Cleaver, CEO of the De Beers Group; Gina Drosos, CEO of Signet Jewelers; Jason Goldberger, CEO of Blue Nile; Andy Johnson, CEO of Diamond Cellar Holdings; Rahul Kadakia, international head of jewelry at Christie’s; and Kent Wong, managing director of Chow Tai Fook.
The forum began with an industry forecast via video from Scott Galloway of the NYU Stern School of Business. The discussion centered around several key points:

Technologically driven changes in retailing and trading, and continued consolidation across the value chain. These market shifts include challenges from giants such as Amazon and an increase in manufacturers selling direct to consumers, bypassing traditional retail channels.
Evolving consumer tastes and desires, including concerns over gem sources and sustainable production
The need to appeal to a rapidly changing workforce
Disruption caused by laboratory-grown diamonds, both in the marketplace and in laboratory testing and identification

Bruce Cleaver of the De Beers Group listens as Signet Jewelers’ Gina Drosos explains the importance of omni-channel retailing. Photo by Denise Conrad/GIA.
TECHNICAL CHALLENGES
There was broad agreement that retailers must adapt to technology, not just in sales channels, but in ways it can help individualize each customer.
Drosos explained that omni-channel retailing is a necessity because customers routinely cross channels in their shopping experience, starting online and ending in the store. Online channels can enhance the in-store experience by making it possible for customers to make appointments online—90% of such appointments result in a sale, she noted.
Wong said that 15% of Chow Tai Fook’s sales by volume are done online, but mainly in small gold items and in charms such as Hello Kitty and Disney characters. At the high end, Kadakia said that 90% of Christie’s auction business is still done by traditional bidding, but the remainder is online, mainly from younger clients buying pieces under $10,000. “This is how we target younger customers,” he said.
A CHANGING WORKFORCE
The changing workforce was a key discussion point in the session. Businesses must adapt to a millennial workforce comprised of people who switch careers because they value diverse experiences and often do not want to stay with a company over the long term.
Goldberger told the audience that organizations should not become too insular and that people with diverse backgrounds bring new thinking. He added, “The reality of today is that tech people move every two or three years, so we have a choice: Do we lose them entirely or benefit from their talent while they are here?”

An audience member poses a question for the panel at the Futurescape Forum. Photo by Denise Conrad/GIA.
Cleaver noted that there are excellent opportunities to diversify the traditionally conservative diamond industry, while Wong said his company brings in gifted designers by offering them a platform to create and sell their designer pieces. “Talented people need that freedom,” he pointed out. Johnson added that not everyone wants to switch careers, and businesses must adapt to workers who cannot be on hand full-time.
NATURAL AND LABORATORY-GROWN DIAMONDS
Laboratory-grown diamonds occupied a great deal of discussion in the Futurescape Forum. Panelists agreed that while they have a place in the market, natural diamonds will still be the choice to celebrate life’s landmark occasions. Kadakia was confident that natural diamonds will remain the consumer choice because they will always have value, while synthetics will not hold value over time.
Goldberger noted that while today’s engagement ring buyers invariably prefer natural diamonds, we cannot take this for granted in the future. He cited the example of consumers who in the 1990s loved to browse bookstores but then deserted them for online channels. Cleaver said that synthetic diamonds’ place in the market was firmly in the “fun and fashion” side.
GEMSTONE SOURCING AND PRODUCTION
Cleaver also related the economic and political success of Botswana, once one of the world’s poorest nations. Diamond revenues, coupled with good governance, helped transform Botswana into one of Africa’s most prosperous countries.
As Cleaver noted, “It’s a story not always told—the good that diamonds can do in employing people and development.” Drosos said customers are interested in knowing the origins of their diamonds and that Signet is working to familiarize all employees with its corporate social policies regarding sourcing.

Kent Wong discusses Chow Tai Fook’s approach to attracting talented designers while David Ager (left) and Rahul Kadakia (right) look on. Photo by Denise Conrad/GIA. Source: GIA @topic:8


Title: Vlasovite Abstract: Figure 1. This 1.20 ct octagonal modified brilliant was identified as the rare gem vlasovite. Photo by Diego Sanchez.

The Carlsbad laboratory recently received for identification service a stone with properties that were not consistent with stones previously identified at GIA. This yellow octagonal modified brilliant (figure 1), measuring 6.41 × 5.26 × 4.68 mm, weighed 1.20 ct and had a specific gravity of 3.01. Microscopic features observed included distinct parallel twinning planes (figure 2), iridescent fractures, stringers, and fingerprints. Standard gemological testing revealed that it was doubly refractive, with a biaxial optic figure and a refractive index of 1.608–1.628. It fluoresced a very weak yellow under short-wave UV and had no reaction under long-wave UV. The Raman spectrum of the stone (figure 3) was matched to one in the RRUFF database, which confirmed the gem’s identity as vlasovite, an inosilicate mineral with the chemical formula Na2ZrSiO4O11 (rruff.info/vlasovite/R060913).

Figure 2. Colorful twinning planes were observed in the faceted vlasovite using polarized light. Photomicrograph by Jessa Rizzo; field of view 3.23 mm.

Figure 3. Raman spectroscopy confirmed the gem’s identity as vlasovite.
Vlasovite is known to be found in pegmatites in northern Russia, Canada, and Portugal. It was named after Kuzma Alekseevich Vlasov, who studied the region where vlasovite originated (handbookofmineralogy.com). Vlasovite is a rare mineral, and faceted stones are especially rare. This is the first faceted example examined at GIA’s Carlsbad laboratory. Source: GIA @topic:2


Title: Complex Yellow Fluid Inclusions in Red Burmese Spinel Abstract: This octahedral-shaped negative crystal in a Burmese red spinel is filled with colorless carbonate crystals, yellow sulfur-rich liquid, opaque sulfide crystals, and diaspore fibers. Photomicrograph by Victoria Raynaud; field of view 1.20 mm.

Spinel has found new popularity and is now recognized as a birthstone for August. Some of the most desirable stones come from Myanmar, as they exhibit a pure red color with a light tone, accompanied by extremely high fluorescence under long-wave UV. Red Burmese spinel can also be found with a dark tone and much weaker fluorescence. The main localities that produce the highly fluorescent spinel are Namya in northern Myanmar and Man Sin in the Mogok Valley (V. Pardieu, “Hunting for ‘Jedi’ spinels in Mogok,”Spring 2014 G&G, pp. 46–57). Clean stones are rare, as the majority have inclusions consisting of colorless carbonate crystals and complex multiphase negative crystals. These complex negative crystals contain a sulfur-rich yellow liquid, opaque metal sulfides, transparent carbonate daughter crystals, diaspore fibers, and a gas bubble. This unique yellow complex fluid inclusion (see above) is only known to occur in Burmese spinel and therefore serves as a good indicator of this origin. Source: GIA @topic:3


Title: Opal Quality Factors Abstract: This large Australian light opal cabochon weighs 117.85 carats. Small play-of-color flashes of orange and green predominate in a pinfire pattern, with spots of a more muted blue over a grayish bodycolor.

Individual opals can vary widely in appearance and quality. As diverse as snowflakes or fingerprints, each gem can differ noticeably.
There are three main aspects of an opal’s quality:

Color—Background color and play-of-color
Pattern—Arrangement of play-of-color
Clarity—Transparency and quantity of inclusions

How to Evaluate an Opal
Opal evaluation should be done under controlled lighting on a dark background. Rotating the opal against a background helps when you’re determining its type and evaluating its play-of-color and cut.
The Five Steps of Evaluating an Opal

Determine the type of opal:

Is it a black opal, white opal, crystal opal, etc.?

Determine the ratio and quality of its play-of-color:

Consider the percentage of play-of-color compared to background color, its intensity, dominant hues, range of color and pattern.

Determine the opal’s transparency:

Is it transparent, semi-transparent, translucent, semi-translucent or opaque?

Determine the opal’s clarity:

Look for the presence of matrix, crazing, pits, etc.

Evaluate the opal’s cut:

Consider the opal’s symmetry, thickness, polish, sizing and calibration.

Opal Colors
Opal hues can range across the spectrum. An opal might display a single color, two or three colors, or all the colors of the rainbow. Opal displays background color in addition to play-of-color. Background color—also called bodycolor—is caused by the suspension of tiny impurities within opal’s silica spheres.

This black opal has a lot of red play-of-color, which is considered highly desirable. Courtesy Mariora, Surfer’s Paradise, Australia
Opals are often divided into types based on background color. Even though there are many different categories for opals, here are the main five types:

Black Opal
All other quality factors being equal, many buyers favor the dark background color of black opal. This is partly because play-of-color tends to stand out attractively against a dark background. The contrast of play-of-color to bodycolor makes black opals very popular. Additionally, black opals are considered to be the rarest (white opals are more common).

White Opal
An opal with a translucent to opaque white and other light color backgrounds (bodycolor) with play-of-color is called white opal.

Fire Opal
Fire opal is transparent to translucent with a bodycolor that is usually yellow, orange or red. This material, which might show play-of-color, is also known in the trade as “Mexican opal” or “Mexican fire opal”.

This fire opal weighs a spectacular 132 carats. Courtesy W. Constantin Wild & Co., Idar-Oberstein, Germany
Boulder Opal
Boulder opal is translucent to opaque opal with play-of-color within a host rock. Thin layers of opal exist within the host rock (called matrix). The opal is cut with the matrix attached and is part of the finished gem.

Boulder opals can display intense play-of-color. Photo: Robert Weldon/GIA

Crystal and Water Opal
Crystal opal is transparent to semitransparent with a clear background. This type of opal can show excellent play-of-color. Water opal might or might not display play-of-color. If it does show play-of-color, it is faint and covers only small portions of the gem.

Play-of-color might be the most spectacular aspect of an opal’s appearance. No matter the color or combination of colors, play-of-color must be vivid to command a high rating. In other words, opal lovers prize bright play-of-color over faint play-of-color.
Secondary in importance to play-of-color’s strength is its range. If an opal’s play-of-color is not just bright, but also ranges across the entire spectrum, it’s very rare and valuable. Not every precious opal, however, sparkles with every color of the rainbow. In some, the play-of-color consists of just one main color and two or more secondary colors.

These light-colored opal beads are milky in appearance and have numerous dead spots with no play-of-color. Courtesy Cody Opal
Desirable play-of-color is further broken down by the colors themselves. Traditionally, red is considered the best prominent color, orange the next most desirable, followed by green. However, favored colors can vary with fashion or personal preference.
In addition, an opal’s play-of-color can change along with the viewing angle or type of light. For example, red might dominate in the same portion of an opal cabochon where blue dominates when it’s viewed from a different angle.
The most valuable opals display play-of-color from all angles.
Opal Patterns
Pattern describes the arrangement of an opal’s play-of-color. Like the shapes you see in the clouds, play-of-color takes many forms.
Common terms for play-of-color patterns include:

Pinfire or pinpoint: Small, closely set patches of color
Harlequin or mosaic: Broad, angular, closely set patches of color
Flame: Sweeping reddish bands or streaks that shoot across the stone
Peacock: Mainly blue and green

In general, connoisseurs prefer large, closely arranged patches of color over tiny, scattered dots. As with any play-of-color, no matter what the pattern, colors must be bright for the stone to be valuable.

The harlequin pattern in this black opal has a lot of red, blue, and green play-of-color. Photo: Rudy Weber. Courtesy Cody Opal

In a close-up view, you can see the details of a black opal’s near-perfect harlequin pattern. Courtesy Cody Opal
In addition to the arrangement and shape of the play-of-color patches, buyers must consider extinction, or “dead spots,” when evaluating pattern. A dead spot is an area of the gem in which no play-of-color appears and only background color is visible. Dead spots detract from opal value, especially if there are several of them.
Opal Clarity and Transparency
With an opal, clarity is its degree of transparency and freedom from inclusions. An opal’s clarity can range all the way from completely transparent to opaque. Experts prize different levels of clarity for different opal types. For example, in crystal opal, experts admire transparency, while in black opal they prefer an opaque background. Each provides the best background for displaying play-of-color in its individual opal type. A cloudy or milky background color lowers the value of any opal. It makes the gem less attractive, and it can sometimes signal a lack of stability.

Crystal opal can have intense play-of-color in a harlequin pattern.
There are various types of opal clarity characteristics that affect value. Opals, like other gems, can have fractures, or pits and other surface blemishes. An opal might also contain fragments of its host rock, called matrix. Matrix in a polished opal is usually—but not always—detrimental to its appearance and value. It depends on the type of opal.
If an opal loses moisture, it can lead to crazing: a fine network of cracks that resembles a spider’s web. The moisture loss can be caused by heat or excessive dryness, or by exposure to bright light or direct sunlight. Crazing can be prevented by never displaying opals in places— such as window displays—where they’re exposed to these conditions.

Boulder opals are opaque, giving them a mysterious look that’s ideal for designer jewelry pieces. Courtesy Cody Opal
Even if cracked opals don’t break right away, they have little durability in jewelry, and the fractures spoil the beauty and clarity of the gem. For quality control, producers and dealers single out opals that they suspect might ultimately craze. Dealers who willingly buy crazed opal do so because it commands a lower wholesale price than undamaged opal. This means they can sell it at a lower retail price level.
Opal Cutting
The cutter considers an opal’s color, pattern, and clarity when planning the finished gem. As with many top-quality colored stones, exceptional opals might not be cut to standard sizes and shapes.

This incredible black opal is cut in a freeform shape. Photo: GIA
Cutters usually fashion exceptional rubies or sapphires, for example, in a way that saves weight or maximizes color— even if the result is an unevenly proportioned gem. In a similar strategy, opal cutters usually cut top-quality rough to show off its spectacular play-of-color.
To achieve this goal, cutters might fashion fine opals into large, irregular shapes that keep as much play-of-color as possible. Designers set these costly one-of-a-kind gems into custom pieces.
On the other hand, cutters typically fashion commercial-quality white opal and assembled opal into standard calibrated sizes, usually ovals.
The cut of a fine opal should be symmetrical. If it’s a cabochon, the dome should be well rounded. Domed surfaces give the best play-of-color, and make the stone appear vivid from most viewing angles. If the cabochon is flat, it might be vulnerable to breakage, especially during setting into jewelry. If it’s too high, it might be hard to set in jewelry.
Carat Weight
Opals come in a wide range of sizes and carat weights. Opal has relatively low density compared to many other gemstones so even larger sizes can be comfortable to wear.
Common sizes for many of the opal cabochons set in jewelry are 6×4, 7×5, and 8×6 mm.
The Fire of Australia, a large uncut opal, weighs 998 grams or just under 5,000 carats. South Australia is one of the few places on Earth where opals of this size can be found. Approximately 90% of the world’s opals are from Australia.

At 24 carats, this high-quality black opal will make an impressive centerpiece for a jewelry design.  Courtesy Cody Opal
Assembled Opals
Opal can be fragile. In solid opal cabochons, the gem material is usually thick enough to withstand everyday wear and jewelry repair without breaking. But with thinner material, manufacturers often have to add a rigid backing for durability.
Assembled opals are fashioned opals with backings. They might include materials like glass that aren’t usually part of gem-quality jewelry, but because they are partly precious opal, they still have value as gems. They sell for only a fraction of the price of boulder opals, but they allow manufacturers to make attractive finished gems from thin opal pieces.
The two common types of assembled opal are the opal doublet and triplet. The doublet is a thin layer of opal cemented to a backing. The backing is often composed of obsidian, dyed black chalcedony, black glass, natural common opal, or plastic. The triplet is a thin layer of opal cemented between a domed top of colorless quartz or clear glass and a backing of obsidian, chalcedony, or black glass. Source: GIA @topic:11