Title: Gem-Quality Grossular-Andradite: A New Garnet from Mali Abstract: A find of new gem garnets has been made in contact metamorphic deposits in the Republic of Mali, western Africa. These garnets, primarily yellow-green to brown but also (rarely) intense green, have compositions between grossular and andradite. Although garnets of similar composition are relatively well known, this is the first documented occurrence of gem-quality material in commercial quantities. Because this gem variety is not represented by any of the gem garnet terms previously in use, it is described as grossular-andradite by the GIA Gem Trade Laboratory. It can be distinguished from grossular by its absorption spectrum and (usually) higher refractive index; it can be distinguished from andradite by its lower R. I. The stacked parallel planes of growth zoning, always visible between crossed polarizers, are diagnostic of grossular-andradite. Source: GIA @topic:2


Title: Gem Corundum in Alkali Basalt: Origin and Occurrence Abstract: Many deposits of gem corundum are associated with alkali basalt. Best known are the occurrences in Southeast Asia (especially Thailand) and Australia, which are responsible for much of the sapphire and fancy sapphire on the world market today. Yet alkali basalts are relatively uncommon, and corundum deposits are found only in those alkali basalts that occur in association with subduction zones involving ocean-continent plate collisions. This article offers a new hypothesis for the relationship between this rock type and gem corundum. It suggests that gem corundum is formed when certain rocks—such as shales, laterites, or bauxites, with aluminum-rich minerals—are subducted to depths of about 50 km, where metamorphism converts the minerals into corundum and other products that the alkali basalts later carry to the surface. The potential for new deposits is considered. Source: GIA @topic:1


Title: A Prospectors’ Guide Map to the Gem Deposits of Sri Lanka Abstract: Sri Lanka is world famous for its gem wealth, but the actual extent of the deposits has never been determined. Recently, a geologic survey team gathered field data in order to compile the first gem prospectors' guide map of Sri Lanka. Using the criteria of lithology and topography, stream-drainage density, presence of alluvium, and the nature and abundance of heavy minerals, this team determined that approximately 20% of the land mass of Sri Lanka may be gem bearing. They also characterized the potential of specific regions. Source: GIA @topic:1


Title: A New Gem Beryl Locality: Luumäki, Finland Abstract: Strongly etched prismatic crystals of yellow, green, and pale blue gem beryl have been quarried from a pegmatite dike in Luumäki, Finland. To date, the pegmatite has yielded about 15 kg of gem beryl, minor amounts of facet-grade topaz, and many varieties of quartz. The gem beryls from Luumäki are similar in gemological properties and chemical composition to other pegmatitic beryls, such as those from Brazil and the Ukraine. Large primary fluid inclusions surrounded by micro-fracture halos may be diagnostic of the new locality. Source: GIA @topic:2


Title: Well-Formed Tsavorite Gem Crystals from Tanzania Abstract: Green grossular garnet crystals of fine form and clarity have been found recently in Tanzania, at the Karo pit of the tanzanite mining belt. Although the crystals tend to be relatively light in color, they are consistent in gemological properties and composition with the grossular variety popularly known as tsavorite. The very distinct and complex morphology of these crystals is remarkable. Eight different crystallographic forms have been identified, including one that has never before been recognized for any member of the garnet group. Source: GIA @topic:2


Title: A New Gem Material from Greenland: Iridescent Orthoamphibole Abstract: Orthoamphiboles with pronounced iridescence are found in eight localities in the vicinity of Nuuk, the capital of Greenland. The iridescence, difficult to see on rough samples, becomes clearly visible when the material is cut. This iridescent orthoamphibole is mined by a company wholly owned by Nuuk commune, and is sold under the trade name Nuummite. This orthoamphibole has a composition similar to that of iridescent orthoamphiboles described earlier from Greenland as well as from New Hampshire and Massachusetts, but is believed to be the first such orthoamphibole to be regarded as a gemstone. Source: GIA @topic:1


Title: Synthetic Gem Materials in the 2000s: a Decade in Review Abstract: The first decade of the 2000s brought a constant flow of previously known synthetics into the marketplace, but little in the way of new technology. The biggest development was the commercial introduction of faceted single-crystal gem-quality CVD synthetic diamonds. A few other interesting and noteworthy synthetics, such as Malossi hydrothermal synthetic emeralds and Mexifire synthetic opals, also entered the market. Identification of synthetic gem materials continued to be an important function of—and, in some cases, challenge for—gemologists worldwide. Source: GIA @topic:1


Title: The Elahera Gem Field in Central Sri Lanka Abstract: Commercially important quantities of gem-quality sapphire, spinel, garnet, chrysoberyl, zircon, tourmaline, and many other gemstones are being recovered from deep gem pits and surface excavations in the Elahera gem field, a region in central Sri Lanka about 115 km northeast of the capital city of Colombo. Large-scale mining is being conducted in this highly metamorphosed sedimentary deposit by the State Gem Corporation in collaboration with the private sector. The chemistry and gemological characteristics of these gem materials are discussed; in many instances, characteristic inclusions were identified by microscopy, microprobe analysis, and X-ray powder diffraction analysis. It is estimated that the Elahera gem field currently provides approximately 35% of the gemstones exported from Sri Lanka. The continued steady production of good-quality gems is anticipated for the future. Source: GIA @topic:1


Title: Contemporary Intarsia: The Medvedev Approach to Gem Inlay Abstract: Using precision inlay (intarsia) techniques, Russian émigré Nicolai Medvedev is creating masterpieces of lapidary work in boxes, candlesticks, clock cases, and jewelry. He uses high-quality lapis lazuli, opal, malachite, sugilite, azurite, tourmaline, and rhodochrosite, among other materials, to create these colorful and precisely constructed pieces. Some of his techniques are explained in a step-by-step procedure used to create the "Camellia" box. Source: GIA @topic:10


Title: A Proposed New Classification for Gem-Quality Garnets Abstract: Existing methods of classifying garnets have proved to be inadequate to deal with some new types of garnets discovered recently. A new classification system based on the chemical analysis of more than 500 gem garnets is proposed for use in gemology. Chemical, optical, and physical data for a representative collection of 202 transparent gem-quality stones are summarized. Eight garnet species are defined—grossular, andradite, pyrope, pyrope-almandine, almandine-spessartine, spessartine, and pyrope-spessartine—and methods of identification are described. Properties that can be determined with standard gem-testing equipment (specifically, refractive index, color, and absorption spectrum) can be used to identify a garnet as one of the eight species and, where appropriate, more precisely as one of several varieties that are also defined. Source: GIA @topic:3


Title: Pinpoint Illumination: A Controllable System of Lighting for Gem Microscopy Abstract: Pinpoint illumination uses a highly flexible but extremely durable glass fiber-optic bundle that incorporates six easily interchangeable light wands of various shapes and cross-sectional thicknesses down to one millimeter in diameter. The wands are hand held and can be used to illuminate hard-to-reach areas in complex jewelry mountings. With the pinpoint illuminator, a gemstone can be examined from any angle; the light source is placed exactly where it is needed, minimizing glare and unwanted external or internal reflections. Source: GIA @topic:1


Title: Gem Garnets in The Red-To-Violet Color Range Abstract: The gemological classification of garnets has been thrown into question with the appearance on the market of new types of garnets that do not fit into the traditional system of description. The question of what criteria should be used to classify both old and new types of garnets is approached in this article through the study of 96 red-to-violet gem garnets. While the color of gem garnets is of paramount importance, color being both their most obvious feature as well as their principal claim to beauty, this article shows that the characteristic of color appears to have little correlation with variations in bulk (not trace) composition or physical properties. Analysis of the gemological properties, chemical composition, and CIE color coordinates of the stones studied led to the more specific definition of the widely accepted terms pyrope, almandine, and rhodolite for meaningful gemological classification. This article represents the first in a series of studies aimed at developing an effective terminology for the characterization of gem garnets. Source: GIA @topic:3


Title: 2014 Sinkankas Symposium on Peridot and Green Gems Abstract: At the 2014 Sinkankas Symposium, Lisbet Thoresen presented lectures on peridot from Zabargad and the historical origins of “chrome” chalcedony. Photo by Robert Weldon/GIA.

                      More than 150 gem enthusiasts attended the twelfth annual Sinkankas Symposium on April 5 at GIA headquarters in Carlsbad, California. The theme for the day was peridot and uncommon green gem minerals.

Cohosted by the Gemological Society of San Diego and GIA, the symposium is held in honor of the famed gem and mineral author John Sinkankas (1915–2002). This year’s event featured 11 half-hour lectures covering a wide range of topics. Symposium organizer Roger Merk, a friend of Sinkankas’s, created a program that blended research, curatorial, and trade perspectives.

Attendees got an in-depth look at important geographic sources of peridot, past and present. Independent gem scholar Lisbet Thoresen, delivering the keynote address on behalf of Dr. James Harrell, described a 2010 archaeological expedition to the ancient mines on the Red Sea island of Zabargad. Dr. Raquel Alonso-Perez, curator of the Harvard Mineralogical and Geological Museum, characterized the geochemical setting of peridot from Pakistan’s Sapat Valley. Dr. George Harlow of New York City’s American Museum of Natural History, showed how the deposits of Mogok, Myanmar, are geochemically similar to those of Zabargad and Sapat Valley.

Dr. Raquel Alonso-Perez discussed the peridot deposits of Pakistan’s Sapat Valley. Photo by Robert Weldon/GIA.
Also in the technical realm, Dr. William “Skip” Simmons of the University of New Orleans detailed the mineralogical and crystallographic properties of the olivine group. Complementing this talk was a presentation on olivine geology by GIA’s Dr. James Shigley.

Dr. William “Skip” Simmons delivered a talk on the physical properties, chemical composition, and crystal structure of olivine. Photo by Robert Weldon/GIA.
In the afternoon sessions, Nathan Renfro of GIA’s Carlsbad laboratory demonstrated lapidary techniques for improving the optical performance of peridot and compared inclusions from various localities. Ms. Thoresen presented the historical context of the quartz variety known as “chrome” chalcedony. Robert Weldon of GIA overviewed the jewels of the Cheapside Hoard, an archeological trove buried in London centuries ago that included peridot from Zabargad. Dr. Shigley surveyed some lesser-known green gem minerals occasionally used in jewelry. Bill Larson, president of Pala International, presented a gallery of green gem and mineral specimens from his personal collection, several of which were also on display. In the closing address, Dr. George Rossman examined the causes of color in various green gem minerals.

To view symposium abstracts and speaker bios, or to order a copy of the proceedings volume, visit www.sinkankassymposium.net.

According to Merk, opal will be the theme for the 2015 Sinkankas Symposium. The lineup of scheduled speakers includes Dr. Eloïse Gaillou, associate curator of the Natural History Museum of Los Angeles County, and Renée Newman, a leading author of gem and jewelry consumer guides. Source: GIA @topic:1


Title: Landmark Articles from Gems & Gemology Abstract: Gems & Gemology, GIA’s peer-reviewed quarterly journal, has had far-reaching effects on the science of gemology. For eight decades, its reporting has informed scientists and researchers, and educated generations of gem and jewelry professionals.

We asked the magazine’s editor and key contributors to review the journal’s body of work, and select articles they considered to be especially significant. After reviewing this treasure trove of materials, they picked ones that were particularly important to advancing gemological knowledge and providing practical insights to the gem and jewelry industry.

We share with you their selections.

A Solution to Diamond Color Grading Problems
By Robert M. Shipley and R.T. Liddicoat
FALL 1941, VOL. 3, NO. 11, PAGES 162-167

Robert Shipley Sr. and Richard Liddicoat describe methods for evaluating the color of colorless to light-yellow diamonds by the use of a standardized light source for viewing; and a prototype colorimeter for grading the color against a graduated color scale (which would later become the D-to-Z color grade scale).

The GIA diamond grading system was introduced in the early 1950s, with the first diamond grading reports issued in 1955. It is now the international standard for evaluating diamond quality.

New or Unusual Gem Materials Encountered in the Institute’s Gem Trade Laboratories
By G. Robert Crowningshield
SUMMER 1957, VOL. 9, NO. 2, PAGES 35-37, 61-62

Robert Crowningshield’s debut column describes new and interesting gem materials submitted to GIA for examination. Nearly 60 years later, reports on gem materials still appear in the “Lab Notes” section of the journal.

An Introduction to Spectroscopy in Gem Testing
By G. Robert Crowningshield
SUMMER 1957, VOL. 9, NO. 2, PAGES 46-55, 62

In the early 1950s, GIA lab staff used a spectroscope pioneered in the United Kingdom to identify diamonds and colored gemstones. During the next few years, Robert Crowningshield became one of the masters in using the spectroscope for studying gems, and also created hand-drawn patterns of spectral bands of a wide variety of gem materials.

Here Crowningshield describes how gemologists can use the spectroscope. Reproductions of a number of his spectra drawings are included. The spectroscope remains one of the most important instruments for gem testing.

Developing the Powers of Observation in Gem Testing
By R.T. Liddicoat
SUMMER 1962, VOL.10, NO. 10, PAGES 291-303

Richard Liddicoat describes methods for observing key features in gem material to determine their identity. More than 50 years later, these methods remain an essential component of GIA gem identification courses.

Rapid Sight Estimates of Diamond Cutting Quality
By R.T. Liddicoat
FALL 1962, VOL. 10, NO. 11, PAGES 323-335

The face-up appearance of a diamond depends upon the proportions of the facets and their related angles. Richard Liddicoat describes visual techniques that allow gemologists to estimate important proportion values.

The Characteristics and Identification of Filled Diamonds
By John I. Koivula, Robert C. Kammering, Emmanual Fritsch, C.W. Fryer, David Hargett, and Robert E. Kane
SUMMER 1989, VOL. 25, NO. 2, PAGES 68-83

Filling surface-reaching breaks with a special glass can hide clarity characteristics and improve the apparent clarity of a diamond. This is the most widespread treatment used on colorless and near-colorless diamonds. The authors describe the visual clues gemologists can use to recognize clarity-treated diamonds.

Color Grading of Colored Diamonds in the GIA Gem Trade Laboratory
By John M. King, Thomas M. Moses, James E. Shigley, and Yan Liu
WINTER 1994, VOL. 30, NO. 4, PAGES 220-242

Colored diamonds are the most valuable and some of the rarest gem materials in the marketplace. The procedures used by GIA to observe and describe the color of these diamonds, and the addition of “Fancy grade” terms are detailed here.

Beryllium Diffusion of Ruby and Sapphire
By John L. Emmett, Kenneth Scarratt, Shane F. McClure, Thomas M. Moses, Troy R. Douthit, Richard Hughes, Steven Novak, James E. Shigley, Wuyi Wang, Owen Bordelon, and Robert E. Kane
SUMMER 2003, VOL 39, NO. 2, PAGES 84-135

Heating is the most widely used treatment to change the color or appearance of ruby and sapphire. This process is often augmented by the diffusion of certain elements into corundum to produce a surface-related color zonation. John Emmett and others describe the various mechanisms used to create or modify color in corundum by heating and diffusion treatments.

A Foundation for Grading the Overall Cut Quality of Round Brilliant Cut Diamonds
By Thomas M. Moses, Mary L. Johnson, Barak Green, Troy Blodgett, Kim Cino, Ron H. Guerts, Al M. Gilbertson, T. Scott Hemphill, John M. King, Lisa Komylak, Renee M. Renitz, and James E. Shipley
FALL 2004, VOL. 40, NO. 3, PAGES 202-228

The foundation of the cut grading system for round brilliant-cut diamonds was created using a decade of work of mathematical models of light interacting with polished diamonds, along with numerous observations of a variety diamonds. It started appearing on diamond grading reports in 2006. It is described here.

Color Grading “D-to-Z” Diamonds at the GIA Laboratory
By John M. King, and Ron H. Guertz, Al M. Gilbertson, and James E. Shigley
WINTER 2008, VOL. 44, NO. 4, PAGES 296-321

The authors describe key concepts for evaluating color in colorless to light yellow diamonds. Grading color remains an essential component of the quality grading system of diamonds, which GIA introduced in the early 1950s. Source: GIA @topic:7


Title: 80 Years of Gems & Gemology Abstract: The journal had humble beginnings. Robert M. Shipley, founder of GIA and the publication, produced the ﬁrst issues out of his home. He and his son, Robert Jr., wrote many of the articles, while Shipley’s wife, Beatrice, was the business administrator. Shipley’s vision of a publication “to increase the gem merchant’s knowledge and ability” evolved and flourished. Eminent gemologists such as Robert Crowningshield and Edward Gübelin wrote articles about industry milestones. Richard T. Liddicoat assumed the roles of editor of Gems & Gemology (G&G) and president of GIA in 1952, continuing in the pioneering tradition of his predecessor. Now 80 years since its conception, G&G continues its legacy as a groundbreaking, award-winning research journal.

Over these eight decades, G&G has been a critical resource for the gem and jewelry industry. Groundbreaking articles on diamond grading appeared as early as the 1940s. Through the Lab Notes section, GIA gemologists reported on the latest treatments and synthetics, which helped to protect the trade and the public.

Clarity enhancement of emeralds and diamonds. High-tech color enhancement of rubies and sapphires. Synthetic rubies, emeralds, sapphires and—perhaps the greatest challenge—synthetic diamonds. All have been explained through the pages of G&G.

At the same time, the journal has introduced to the world new gem materials such as moissanite; explored historic and new gem deposits from Colombia to Mozambique; and reported on rapid developments such as the emergence of China’s cultured pearl industry and diamond mining in Canada.

“For 80 years, G&G has been one of the principal professional journals for information on gem materials of all kinds. Its contents reveal the evolution of the science of gemology,” said Dr. James Shigley, GIA Distinguished Research Fellow. G&G continues to evolve under the editorship of Duncan Pay. While the journal will retain its scientific rigor, Pay’s vision is to reach a broader audience and further integrate its groundbreaking research into GIA education.

“G&G is backed by GIA’s laboratory, giving us unmatched resources to investigate the important issues of the day. This makes it a unique vehicle for advancing the study of gemology and for educating our students and the trade professionals,” noted Pay.

All 80 years of G&G are available for free download at www.gia.edu, thus broadening its reach around the globe. Gem and jewelry professionals can easily access a library of diverse and relevant articles. We also asked the journal’s editor and key contributors to pick ten landmark articles, and their selections are fascinating and illuminating. View the landmark articles here.

If history is a guide, the next 80 years promise to be even brighter than the first. Source: GIA @topic:7


Title: Gem-Carved Ensemble is Music to Philanthropist’s Ears Abstract: View Gallery

	“Symphony in Gemstones,” a miniature, 21-piece orchestra carved of gem materials, was donated to the GIA Museum Collection by Art Sexauer, a longtime benefactor of the museum, in 2002.

	Each instrument offers its own special characteristics, from the tourmaline violins and Persian turquoise trumpet to a lapis saxophone and a spectacular tiger-eye harp with 14K gold strings. The collection’s rhythm section is rounded out by three kettledrums made of black onyx and quartz and a grand piano that features a white quartz and black onyx keyboard

	Sexauer’s idea for the “Symphony in Gemstones” came from a visit to the Tucson Gem and Mineral shows in in the early 1980s when he came across a crude gem carving of a guitar. He was instantly inspired to create an entire gemstone orchestra carved by the expert hands of German artisans in Idar-Oberstein.

	Sexauer, who had already amassed an exceptional collection of tourmaline animal carvings, was well aware of the time and dedication assembling a miniature orchestra carved from gem materials would take. He commissioned master carver Lothar Herrmann and his partner David Hudson, who took one year to create the set, which is displayed on a three-tiered, white marble stage.

	“Symphony in Gemstones” has been on display several times at the Tucson Gem and Mineral shows, as well as in museums across the United States. Sexauer believes the collection may be the only one of its kind in the world.

	Sexauer, who’s had an appreciation for music since his childhood when he would listen to his father play the violin, says the symphony represents two of his favorite things.

	“Music is beautiful and gemstones are beautiful,” he says. “If you put the two together the combination must surely be magnificent.” Source: GIA @topic:10


Title: Trade Fair & Play Fair, Says Gem Trade Abstract: Consumer confidence and globalization has led to increasing public awareness of how the goods  are made and where they are sourced. The article discusses how the colored gemstone industry is taking steps to create conditions that are fair and decent for miners and others involved in the industry, just as the global diamond industry has done with the Diamond Development Initiative and the Kimberley Process. The Fair Trade Gems project was launched by the Columbia Gem House firm and is the first jewelry industry company to join the Fair Trade movement. The Quality Assurance and Fair Trade Gems Protocols that were created were designed to increase the standard of living for the miners and gem cutters and also include environmental protection, fair labor practices, and health and safety standards. Protecting the quality and integrity of the product is an important feature of the Fair Trade Gems program, as it extends the protection to consumers, who deserve to know exactly what they are buying.

Abstracted by Michele Kelley Source: GIA @topic:9


Title: Little Black Dress Meets Little Black Gem Abstract: It’s been nearly a century since Gabrielle “Coco” Chanel, the pioneering French fashion designer, popularized the little black dress, which has since become a wardrobe essential for women in all corners of the globe. The LBD, as it is often called, exists in many variants, and can be worn on almost any occasion that calls for style and elegance.

Like the LBD, the little black gem − otherwise known as the LBG − is a classic, yet versatile piece. The varied LBG collection consists of diamonds, pearls, opals, onyx, and other unique stones, ranging from the most affordable to the most precious gems available. No matter what their price, these stunning stones connote affluence while complementing the LBD as well as many other colors and styles of clothing.

Although some black gems, such as the cultured black pearl, are now reaching new heights in popularity, the use of black stones in jewelry can be traced back to Biblical times. A large onyx stone is said to have graced the gem-laden breastplate of Aaron. Black stones were also in the spotlight in the 19th century when Queen Victoria, mourning the loss of her husband, Prince Albert, commissioned the crown jewelers to create entire parures out of carved jet, a fossil coal also known as “black amber.” During the same mid-19th century period, black onyx and other dark stones were extremely fashionable. And later, during the “Roaring Twenties,” style-conscious women in the United States wore long strands of jet beads extending from the neckline to the waistline.

Today, the black diamond represents the ultimate LBG. According to GIA (Gemological Institute of America), the world’s foremost authority in gemology, black diamonds get their color from the presence of numerous inclusions, often consisting of graphite. Due to the dense concentrations of these dark inclusions, sometimes lining the stone’s cleavages and fractures, black diamonds are generally opaque and difficult to cut. Some notable black diamonds are the Black Star of Africa at 202.00 carats and the Black Orfloff at 67.50 carats.

Near the top of the LBG list are natural black pearls, which represent one of the rarest and most exotic of gem materials. A black-pearl culturing industry was initiated in the 1960s and today, cultured black pearls play a prominent role throughout the international jewelry community. Tahitian cultured pearls are among the most popular of the black pearls. Known for their deep luster, these pearls can range from a soft dove grey to a deep midnight ink color.

Other LBG stones to look for include shimmering tourmaline, glassy obsidian, and hematite, a favorite of lawyers because it is fabled to bring the wearer success in litigation. No matter which LBG the wearer may choose, they can be assured it will meet their requirements for versatility and style – proof that the little black dress has finally met its match. Source: GIA @topic:6


Title: Spring 2007 G&G Book Reviews Abstract: “Pearls”
By Elisabeth Strack, 678 pp., illus., publ. by Rühle-Diebener-Verlag, Stuttgart, Germany, 2006. C= 106.10 (US$115.00)

“Not Your Mama’s Beading: The Cool and Creative Way to String ‘Em Along”
By Kate Shoup Welsh, 224 pp., illus., publ. by Wiley Publishing [www.wiley.com], Hoboken, NJ, 2006. US$14.99

“Special Exhibition Jadeite: Treasure of Orient”
By the National Science Museum [www.kahaku.go.jp/english], 202 pp., illus., publ. by the Mainichi Newspapers Co., Tokyo, 2004 [in Japanese; no price information available]

“Hope Diamond: The Legendary History of a Cursed Gem”
By Richard Kurin, 388 pp., illus., publ. by Smithsonian Books [www.smithsonianstore.com], Washington, DC, 2006. $24.95

“Precious Minerals (Gemology)”
By Ruslan I. Kostov, 453 pp., illus., publ. by PENSOFT [www.pensoft.net], Sofia, Bulgaria, 2003 [in Bulgarian; no price information available]

“Faceting History: Cutting Diamonds and Colored Stones”
By Glenn Klein, 242 pp., illus., publ. by the author [www.glennklein.com], Lake Forest, CA, 2005, US$21.99

“Symposium on Agate and Crypto- crystalline Quartz”
Daniel Kile, Thomas Michalski, and Peter Modreski, Eds., 144 pp., illus., publ. by Friends of Mineralogy (Colorado Chapter), Colorado School of Mines Geology Museum, and U.S. Geological Survey, 2005, US$20.00

“The Art of Diamond Cutting, 2nd ed.”
By Sofus S. Michelsen and Basil Watermeyer, 147 pp., illus., publ. by Sofus S. Michelsen [sofus_sidney@ direcway.com], Port Angeles, WA, 2005, US$49.95

“Alexandrite”
By Yury S. Kozlov, 143 pp., illus., publ. by Nauka Publishers [www.maik.rssi.ru], Moscow, 2005, C= 33.00

Aphrodite’s Drop: The Power of Pearls”
A Faction Films production [www.factionfilms.co.uk], London, 75 min., 2005, available in DVD format, £30.00

To view the full section, download the PDF above. Source: GIA @topic:10


Title: Synthetic Moissanite Coated with Diamond Film Imitating Rough Diamond Abstract: Figure 1. This 5.35 ct sample, submitted as a rough diamond, was identified as synthetic moissanite coated with a diamond film. Photo by V. Pakhomova.

A transparent yellowish octahedral (sawable) crystal (figure 1) weighing 5.35 ct was submitted as a rough diamond to the Far East Geological Institute (FEGI) for examination.
The faces of the octahedron showed a stepped appearance, and the edges had parallel grooves and combinational surfaces. The faces and edges were smooth except for one face where mechanical damage was noticeable. Initially, the specimen was examined using conventional gemological instruments. It was inert to long-wave UV (365 nm) and anisotropic. Thermal conductivity testing indicated diamond. Tests for electrical conductivity were not convincing, however: Some areas (mostly on the edges) corresponded to diamond, but others (on smooth faces and dimples) indicated synthetic moissanite. There were no inclusions associated with natural diamond. Only small parallel needle-like inclusions, typical for synthetic moissanite, were found using a gemological microscope (figure 2).

Figure 2. Needle-like inclusions in the rough synthetic moissanite sample. Photo by V. Pakhomova.

Figure 3. Three-dimensional X-ray tomography rendering of the reconstructed sample. The coloring of the image corresponds to the degree of X-ray permeability. The green color represents the SiC crystal, and the blue color represents the film.
X-ray tomography showed that the inner part of the sample was distinguished by its X-ray density from the outer shell, which had a variable thickness from 19 to 115 microns (figure 3). Microprobe analysis with a JEOL JXA-8100 four-channel microanalyzer revealed the presence of up to 61 wt.% silicon on some polished faces of the crystal, along with titanium in the composition of the surface layer (figure 4 and table 1). Some polished faces showed a diamond chemical signature.

Figure 4. A fragment of the synthetic moissanite crystal, viewed with the electron probe microanalyzer. The crystal was analyzed on the surface. Spectrum numbers correspond to the analysis numbers in table 1.
Based on these results, we identified the sample as synthetic moissanite that had been covered with a thin diamond film. Based on the study by T. Teraji et al. (“Chemical vapor deposition of 12C isotopically enriched polycrystalline diamond,” Japanese Journal of Applied Physics, No. 51, 090104, 2012, pp. 1–7), the diamond coating was likely applied using polycrystalline diamonds. The top layer was made of a composite material consisting of metal matrix and nano-diamond particles.
A diamond imitation such as synthetic moissanite coated with a thin diamond film is challenging to identify, since its luster and thermal properties correspond to diamond. Even with a very thin coating that did not exceed 0.001 mm, the sample tested positive for diamond. This application of thin diamond films onto non-diamond material could be an issue for gemologists in the future.
This work was supported by the Russian Foundation for Basic Research (grant N 16-05-00283) and the Far Eastern Branch of the Russian Academy of Sciences (N 15-1-2-003). Source: GIA @topic:4


Title: Synthetic Diamond Fraudulently Inscribed To Match Natural Diamond Report Abstract: Figure 1. This 1.76 ct synthetic diamond was submitted with a fake GIA inscription (partially redacted for privacy) of an actual GIA report number for a natural diamond. Photos by Troy Ardon.
Improvements in diamond growth technology and methods have led to a noticeable increase in colorless synthetic gem diamonds in recent years. Concerns in the diamond industry focus on laboratory-grown diamonds not being properly disclosed or even being sold as natural stones. Through careful examination and analysis, gemological laboratories can separate natural from synthetic diamonds. Occasionally, however, fraud is involved in attempting to conceal a gem’s identity. The Carlsbad laboratory witnessed such an attempt.

On this occasion, a round brilliant cut (figure 1, left) was submitted for an updated diamond grading report. Its girdle was inscribed with an actual GIA report number issued in 2015 (figure 1, right). The older report was for a natural, untreated diamond and contained the following grading information: 1.74 ct, round brilliant cut, D color, Excellent cut grade, and VVS1 clarity. Upon grading, the new submission was described as a 1.76 ct round brilliant cut with F color, Excellent cut grade, and VS1 clarity. Moreover, our screening processes determined that the newly submitted sample needed additional testing to determine its origin. This examination revealed it to be an HPHT-grown synthetic diamond. Synthetic cuboctahedral growth structure and phosphorescence were clearly visible in DiamondView imaging (figure 2).

Figure 2. DiamondView imaging showed the synthetic growth structure and blue phosphorescence typical of HPHT-grown synthetic diamonds.
Aside from the observed discrepancies in weight (1.74 vs. 1.76 ct), color (D vs. F), and clarity (VVS1 vs. VS1), FTIR spectra clearly showed that these were not the same diamond. The natural diamond from the original report was type Ia with aggregated nitrogen impurities, while the new one was type IIb with boron impurities (figure 3). Careful examination of the report number inscribed on the synthetic diamond revealed a font different from the one used by GIA, proving that it was not an authentic inscription.

Figure 3. FTIR absorption spectra revealed that the synthetic diamond was type IIb, whereas the fraudulently inscribed report number referred to a natural type Ia diamond. The spectra are offset for clarity.
While most synthetic diamonds that come to the laboratory are properly disclosed, some are submitted out of concern that a stone presented as natural might be synthetic. Rarely do we encounter the type of blatant fraud described here. It is important for the industry and public to exercise caution, because these types of misleading practices do occur. We believe the submitting client noticed inconsistencies with the GIA report information and sent it to the lab for an updated report. If any doubt exists or some aspect of a diamond (such as an inscription) seems odd, the stone should be sent to a gemological laboratory for verification. Source: GIA @topic:4


Title: Diamond Market Forecast: Declining Credit, Soft Prices and Lab-Grown Diamonds Abstract: Lab-grown diamonds have become a competitive force to natural diamonds, according to a report, and competition will continue to increase.

Despite the generally strong year for jewelry retail, the diamond industry continues to face problems with ever-tightening credit, spotty demand and softening prices from continued over-production of some types of goods.
Trading sites report that prices for polished natural diamonds declined 2% to 5% since the second half of 2018 due to overproduction and a slowdown in Chinese demand. This caused inventories to climb more than 20% during the year, according to Rapaport estimates. Some analysts speculate that demand for lab-grown diamonds has begun to erode the market for lower-quality natural stones.
In India, local press reports say that available bank credit is half of what it was five years ago and that the decline of the rupee against the U.S. dollar has raised borrowing costs.
De Beers began the year with cautious cycle sales of $505 million, which is down 25% from the same period in 2018 and well below the December cycle, normally the smallest of the year. De Beers will likely follow with a cautious February/March allocation. The company held the line on prices after reducing rates on small, lower-quality goods in the fall, and is likely to continue hold prices, despite the high probability that some clients will leave some allocations on the table.
De Beers sold $5.39 billion worth of rough in 2018, an increase of $8 million from the previous year according to the company, and will release volume data later this year.
Alrosa, the world’s largest diamond miner by quantity, sold $4.412 billion worth of rough in 2018, an increase of 6%. By quantity, sales were down 8% to 36.6 million carats. Alrosa held back selling small, lower-quality diamonds that are in over-supply.
A report from ABN-Amro Bank predicts that this year will see increased pressure on natural diamonds from lab-grown diamonds. The bank says lab-grown diamonds are a game changer in the industry that will ultimately reduce demand for natural diamonds – even larger, better quality stones. The game, according to the report, was changed by De Beers’ low prices ($800 per carat) for Lightbox lab-grown diamonds, coupled with improving technology to grow larger, better quality diamonds. These lab-grown diamonds will enter the market in ever-increasing numbers.
The bank report states that this pressure may expand to larger natural diamonds with more attractive margins and notes that, while De Beers has been careful to position lab-grown diamonds as a different product, consumers are likely not to see them as such.
RETAIL
Analysists are looking at a mixed year for retail sales, including jewelry.
In the U.S., the National Retail Federation (NRF) predicts that retail sales will continue to grow through 2019, though at a slightly slower pace. The retail association says the U.S. economy will remain strong and sales will increase 3.8% to 4.4% for the year, compared to 4.6% last year.
The NRF’s total includes all sales channels, but excludes gasoline, restaurants and autos. Non-store sales, which includes online, grew $10.4% last year. The NRF is predicting a similar increase this year.
The organization noted that consumer confidence remains high and that any problems in the economy are likely to be “self-inflicted,” such as trade wars and government shutdowns.
In China, the results from the top retailers quantify the economic slowdown there. The largest jewelry retailer, Chow Tai Fook, saw its sales fall 7% (gem-set pieces were down 5%), while Luk Fook’s revenues took a 10% hit for the final quarter of 2018. Retailers blame the trade war between the U.S. and China – and no one is predicting an upturn. Source: GIA @topic:8


Title: Single HPHT Synthetic Diamond Mixed in Natural Diamond Ring Abstract: Figure 1. The ring with 194 natural diamonds and one HPHT-grown specimen. Photo by Nazar Ahmed Ambalathveettil.

Recently, a ring with 195 mounted colorless and near-colorless stones (figure 1) was submitted to Dubai Central Laboratory for identification. The ring contained round-brilliant-cut diamond melee arranged in rows. Testing with the DiamondSure instrument identified 194 of them as natural diamond, and the remaining melee was referred for further testing.

Figure 2. These metallic flux inclusions that are associated with feathers show high reflection in oblique light. Photo by Nazar Ahmed Ambalathveettil.

Figure 3. The laboratory-grown diamond fluoresced yellow under long-wave UV (left) and greenish yellow under short-wave UV light (right). Photos by Nazar Ahmed Ambalathveettil.
The sample’s setting in the ring restricted us to FTIR spectroscopy in reflection mode to determine its identity. Solid metallic inclusions were revealed under the microscope (figure 2). The specimen displayed strong yellow and moderate greenish yellow fluorescence under long-wave UV and short-wave UV, respectively (figure 3). The inclusions and fluorescence suggested HPHT-grown diamond, which generally shows a stronger fluorescence reaction to short-wave UV than to long-wave UV. The vast majority of HPHT synthetics in the “colorless” range exhibit no detectable fluorescence to long-wave UV (S. Eaton-Magaña et al., “Observations on HPHT-grown synthetic diamonds: A review,” Fall 2017 G&G, pp. 262–284), but this one showed strong fluorescence under long-wave UV.
The stone was further examined with DiamondView imaging and photoluminescence (PL) spectroscopy. Strong yellowish green fluorescence and blue phosphorescence were observed with the DiamondView, but the growth sector pattern typical of HPHT-grown diamond was not visible because of the stone’s size. PL spectroscopy showed nickel-related peaks at 882/884 nm. Based on these results, we concluded that this was an HPHT laboratory-grown diamond.
We later learned that the customer had given the ring to a jewelry repair shop to replace a broken diamond, which may account for the single lab-grown specimen. This is a good example of the need for vigilance in every stage of diamond jewelry making. Source: GIA @topic:4


Title: An Irradiated CVD Synthetic Melee Diamond Found in Irradiated Natural Melee Diamonds Abstract: Figure 1. This group of 300 green-blue diamonds (1.97 carats total) was screened by GIA’s Tokyo laboratory. Among these, 299 were irradiated natural melee diamonds and the one on the right was an irradiated CVD synthetic melee diamond. Photo by Shunsuke Nagai.

Mixing of synthetic melee diamonds with natural melee diamonds has been reported several times. Those examples were colorless (Winter 2016 Lab Notes, pp. 416–417; Summer 2017 Lab Notes, pp. 236–237) and yellow (Winter 2014 Lab Notes, pp. 293–294). Recently, GIA’s Tokyo lab found a single irradiated green-blue CVD synthetic melee diamond in a parcel of similarly colored irradiated natural melee.
The parcel of 300 uniformly green-blue round melee was submitted for identification (figure 1). Each diamond’s color was attributed to strong GR1 by irradiation treatment. Infrared absorption spectroscopy, photoluminescence spectroscopy, and DiamondView analysis confirmed that 299 of them were irradiated natural diamonds and one of them was an irradiated CVD synthetic diamond. The CVD synthetic diamond weighed 0.007 ct, with a diameter of 1.14 mm.

Figure 2. DiamondView imaging revealing weak linear striations in the pavilion of the irradiated CVD synthetic melee diamond.

Figure 3. The photoluminescence spectrum of the green-blue CVD synthetic melee diamond at liquid nitrogen temperature shows a strong GR1 peak. The SiV– center defect can be observed at around 736 nm. The doublet at 596/597 nm indicates that this diamond did not undergo annealing after synthesis.
DiamondView images of the synthetic showed very weak linear striations in the pavilion (figure 2). Dark inclusions were observed under the microscope. The infrared spectrum showed a peak at 3123 cm–1, and the photoluminescence spectrum showed doublet peaks at 596/597 nm (figure 3). These peaks are seen in CVD synthetic diamonds without post-annealing. The photoluminescence spectrum also showed a small, broad SiV– center defect at 737 nm next to a very strong GR1 center at 741 nm (figure 3). From the peak at 3123 cm–1 and the 596/597 nm doublet peak, this diamond was concluded to be irradiated without pre-annealing.
Irradiated CVD synthetic diamonds are rarely seen at GIA, which had examined only six of them before this report (Fall 2014 Lab Notes, pp. 240–241; Fall 2015 Lab Notes, pp. 320–321; Summer 2018 Lab Notes, pp. 215–216). Previously reported irradiated CVD synthetic diamonds were relatively large, from 0.43 to 1.34 ct. This is the first melee-sized irradiated CVD synthetic diamond examined by GIA. Source: GIA @topic:4


Title: Contribution to the Identification of Treated Colored Diamonds: Diamonds with Peculiar Color-Zoned Pavilions Abstract: Some treated yellow and blue-to-green diamonds show a peculiar color zoning when viewed through the pavilion. The culet or keel-line area on such stones exhibits a bright yellow or blue color that contrasts with the otherwise lighter (and/or different) body color of the diamond (which does not show any other strong color zoning). Such peculiar color zoning near the culet or keel-line is a strong indication that the stone has been treated by electron irradiation. Although rare, this feature can be useful in identifying irradiated diamonds, especially some green diamonds, for which few criteria are available to separate natural-color from laboratory-treated stones. Source: GIA @topic:4


Title: Treated-Color Pink-To-Red Diamonds from Lucent Diamonds Inc. Abstract: Lucent Diamonds has developed a new treatment process for natural type Ia diamonds that produces colors ranging from pink-purple through red to orangy brown, using a multi-step process that involves HPHT annealing, irradiation, and low-pressure annealing at relatively lower temperatures. Those stones that achieve a predominant pink-to-red or purple color are marketed as “Imperial Red Diamonds.” Gemological properties and characteristic spectra are presented for 41 diamonds, representing the range of colors produced thus far. These treated-color natural diamonds can be readily identified by internal graphitization and surface etching seen with magnification, distinctive color zoning, and reactions to long- and short-wave UV radiation. The color is caused primarily by the absorption of the (N-V)- center, with further influence from the (N-V)O, H3, H4, and N3 centers. Other characteristic infrared and UV-visible absorption features include the H1a, H1b, H1c, 6170 cm-1, and, frequently, 594 nm bands. This type of defect combination is not known in naturally colored diamonds. Source: GIA @topic:4


Title: New Filling Material for Diamonds from Oved Diamond Company: A Preliminary Study Abstract: Diamonds filled with a new glass formulation (XL-21) are being marketed by the Oved Diamond Company. These diamonds are readily identifiable as treated by the intense flash-effect colors seen with magnification. Durability testing on a small number of these treated diamonds indicates that this filler material is more stable to conditions of normal jewelry repair, such as direct heating with a torch, than the filler material produced by the Goldman Oved Company a decade ago. Nevertheless, some damage to the filler was observed in half the new Oved diamonds that were subjected to a standard prong retipping. Source: GIA @topic:4


Title: Latest-Generation CVD-Grown Synthetic Diamonds from Apollo Diamond Inc. Abstract: Gemological and spectroscopic properties of 43 CVD synthetic diamonds from Apollo Diamond Inc. were examined to characterize the latest generation of their CVD products. These samples, which included both faceted gems and partially polished crystals, were provided as representative examples of Apollo’s 2006–2007 production. Relative to the Apollo CVD products examined in 2003, the new samples showed significant improvements in size, color, and clarity. In addition to colorless and near-colorless material, fancy orange-to-pink colors are now produced. These high-quality CVD-grown diamonds, comparable in color and clarity to natural diamonds, can be identified using a combination of gemological and spectroscopic properties. Source: GIA @topic:4


Title: GIA Diamond Grading Report Provides Most Respected Diamond Analysis Abstract: Items of significant value typically come with important documentation. Houses have deeds. Vehicles have titles and registration. Purebred pets have pedigree papers. And a college education is validated with a diploma. But what about something as valuable as a diamond? The answer is yes: independent support documentation is available for diamonds to verify their quality and provide positive identification.

The most widely used and recognized means of verifying a diamond’s quality is with a GIA Diamond Grading Report™, provided by the internationally recognized, nonprofit GIA (Gemological Institute of America).

A report from GIA provides an expert analysis of the quality of a diamond based on the 4Cs of diamond grading: color, cut, clarity and carat weight. The GIA Diamond Grading Report also includes a plotting diagram that depicts the diamond’s unique clarity characteristics, such as inclusions. In addition, since GIA is not affiliated with any commercial enterprise, the public is assured the world’s most impartial and accurate analysis of a diamond.

The GIA laboratory employs highly trained diamond graders, gemologists, and research technicians and scientists to ensure the highest caliber of analysis for every diamond submitted for grading. Some of the world’s most famous diamonds have been graded by GIA laboratory experts, including the legendary Hope Diamond (45.52 carats), the De Beers Centenary Diamond (273.85 carats) and the Taylor-Burton Diamond (69.42 carats).

GIA only grades unmounted diamonds, and the fee for services varies based on the weight of the diamond. For an additional fee, the unique GIA Report Registry number can be micro-laser inscribed onto the diamond’s girdle (thin outer edge). This unique number provides added security to the diamond’s owner. The owner can also choose to inscribe a personal message, such as “I Love You” or a special date. The number or wording is permanently registered in GIA’s archive database.

Diamonds weighing 1.99 carats or less can be issued a GIA Diamond Dossier®. This report provides the same information as the GIA Diamond Grading Report, except for the plotting diagram. The micro-laser inscription of the diamond’s unique GIA Report number is included for each diamond receiving a Dossier at no additional charge.

The most convenient way for the public to obtain a GIA Diamond Grading Report or Diamond Dossier, or to request laser inscription services from the GIA laboratory, is to request services through a local fine jewelry retailer. Retail jewelers are familiar with the care and handling of diamonds and jewelry, are better equipped to facilitate service arrangements, and are uniquely qualified to advise the public on the importance of features discussed in a GIA Grading Report.

In 2012, GIA announced the GIA Diamond eReport service, delivering GIA grading results completely online. It is available for natural, D-to-Z color diamonds from 0.15 to 2.99 carats and is available via Report Check, GIA’s secure web-based report database. This new digital-only report provides grading results in a format that is not only more environmentally responsible, but also meets the needs of an evolving marketplace where information must be accessed and communicated rapidly. Additionally, the paperless report format allows us to offer this grading service at a lower fee.

GIA, the world’s foremost authority in gemology, is a public benefit institute and was established in 1931.  The organization is noted for such achievements as inventing the modern jeweler’s loupe (1934), creating the 4Cs (late 1930s), and establishing the International Diamond Grading System™ (1953) – which is recognized worldwide as the standard for diamond grading. Source: GIA @topic:4


Title: Pink-to-Red Coral: A Guide to Determining Origin of Color Abstract: Pink-to-red coral has a long history as an ornamental gem material in jewelry, carvings, and sculptures. However, due to a variety of environmental and legal factors, the supply of high-quality, natural-color coral in this color range has dramatically decreased in recent years—and the quantity of dyed coral on the market has increased. From a study of more than 1,000 natural- and treated-color samples, this article summarizes the procedures that are useful to identify the color origin of pink-to-red coral. A variety of techniques—including magnification, exposure to acetone, and Raman analysis—can determine if the color of a piece of such coral is dyed. Although there are limitations to the use of magnification and acetone, Raman analysis can establish conclusively that the color is natural. Source: GIA @topic:12


Title: The Characterization of Tortoise Shell and its Imitations Abstract: Tortoise shell has long been used as an ornamental gem material for art objects, jewelry, and personal items such as combs and eyeglass frames. Though humans have used tortoise shell for thousands of years, the material reached the height of its popularity during the 18th, 19th, and early 20th centuries. The advent of plastic imitations, as well as the passage of laws protecting sea turtles beginning in the 1970s, have led to a drastic reduction in the amount of tortoise shell in the market. Nevertheless, because older material can still be traded, especially in antique pieces, and because numerous imitations exist, proper identification is still important. This study summarizes the gemological properties of tortoise shell and its imitations. In addition to standard gemological data, the results of several spectroscopic techniques are presented; transmission and specular reflectance infrared spectroscopy were found to be of particular value. Source: GIA @topic:12


Title: Synthetic Moissanite Imitating Rough Diamond Abstract: Figure 1. A very light green 9.71 ct synthetic moissanite crystal, submitted to the Carlsbad laboratory as a rough diamond. Photo by Rebecca Tsang; field of view approximately 14 mm.

The Carlsbad laboratory recently examined a very light green 9.71 ct specimen (figure 1), measuring 11.79 × 9.69 × 11.61 mm, that was submitted as a rough diamond. The sample resembled a diamond octahedron, with surface growth features and a bright vitreous to subadamantine luster. Closer examination of its habit and surface features, along with gemological and advanced testing results, revealed it to be a synthetic moissanite.

The specimen was not a true octahedron, as is typical of a diamond crystal, but a rectangular bipyramid with 10 faces (eight triangular and two hexagonal side pinacoids on the girdle). The surface was dimpled, and two of the faces had deep striations resembling growth features in a rough diamond. Irregularly shaped and sub-hexagonal etch pits (figure 2), along with some dark brown residue, were also found on the surface. Due to the uneven surface, observation of internal features was limited to some small scattered pinpoint inclusions and a few etch tubes (figure 3). The surface also made it difficult to see any doubling effect or a doubly refractive reaction in the polariscope. Viewed in plane-polarized light, however, a large twinning plane crossed the crystal diagonally, bluish green on one side and colorless on the other. This dichroism served as proof of the stone’s doubly refractive nature, as opposed to singly refractive diamond. Standard gemological properties of the stone offered further evidence of its true identity, including an over-the-limit refractive index reading, a hydrostatic specific gravity (SG) of 3.23, very weak yellow fluorescence in both long-wave and short-wave UV, and a uniaxial optic figure. These properties and advanced testing results, including Fourier-transform infrared (FTIR) and Raman spectrometry, identified the specimen as synthetic moissanite. It is important to note that although natural moissanite exists, it is extremely rare and gem-quality material has never been found. Natural moissanite commonly occurs in fragmented pieces and in much smaller sizes (the largest known specimen measured 4.1 mm), often with a creamy white or red matrix (Summer 2014 GNI, pp. 160–161). That was not the case for this 9.71 ct synthetic moissanite.

Figure 2. Sub-hexagonal etch pits in synthetic moissanite are observed using differential interference contrast. Photo by Rebecca Tsang; field of view approximately 1.44 mm.

Figure 3. Etch tubes extended from surface etch pits and ended at the twinning plane. Photo by Rebecca Tsang; field of view approximately 2.30 mm.
Gemological and advanced testing are indispensable tools for revealing the true identity of gems, especially simulants and imitations with an appearance that can easily deceive the general public. While there is no evidence that this specimen was deliberately deceptive, gemological knowledge is important in preventing accidental and intentional acts of fraud and preserving the integrity of the trade. Source: GIA @topic:4


Title: HPHT-Grown Synthetic Diamond with Strain Abstract: Figure 1. This DiamondView image of the 1.60 ct HPHT synthetic shows the diagnostic square pattern seen in the crown facets. Photo by Troy Ardon.

	An undisclosed HPHT-grown synthetic diamond was submitted to the GIA laboratory in Ramat Gan, Israel, for a diamond grading report. It weighed 1.60 ct and was in the near-colorless range. Initial screening showed the diamond was type IIa (without detectable nitrogen or boron in the infrared spectrum), which prompted further testing. Examination with the DiamondView fluorescent imaging system revealed the growth patterns betraying the synthetic origin (figure 1). Photoluminescence detected a further lack of impurities: no nickel-related peaks, a very common defect in HPHT synthetics, and only small amounts of nitrogen-vacancy centers.

	When viewed under polarized light, the diamond showed very little strain throughout most of the body, but one side on the pavilion displayed noticeable birefringent colors caused by internal strain (figure 2). HPHT-grown synthetic diamonds are known for being mostly free of strain, which generally occurs only around inclusions. They are grown in a metal catalyst, and metal particles can become trapped in them. These trapped particles place stress on the host diamond, which causes strain. But that is a localized strain seen around an inclusion, which was not the case in this synthetic diamond. Except for a small fracture on the pavilion, there were no internal inclusions that could have created strain. Furthermore, the strain patterns were linear rather than radial, as is the case with inclusion-related strain.

Figure 2. An image taken with polarized light showing the linear birefringence colors, indicating the presence of linear strain in the diamond lattice. Photo by Troy Ardon; field of view 6 mm.

	Fortunately, this strain is still distinguishable from the type of strain in natural diamonds, which have a cross-hatched pattern known as “tatami” strain. The cause of the strain in this synthetic diamond is unknown, but if it is related to a new growth process we would expect to see more strained HPHT-grown diamonds in the future. As innovations in the synthetic diamond industry continue to introduce a wider variety of products, more and more properties of natural and synthetic diamonds will start to overlap, necessitating caution when separating stones. Source: GIA @topic:4


Title: Etch Features Reveal the Morphology of Diamond Abstract: Figure 1. Table (left) and pavilion (right) views of a chameleon diamond with visible trigons and tetragons. The trigons and tetragons are shown in more detail in figures 2 and 3. The diamond measures 1.28 cm in length. Photo by Adriana Robinson.
Natural monocrystalline diamonds formed in the earth’s mantle have two major growth forms: octahedron and cube. It has been suggested that diamond growth habit depends on multiple factors, including crystallization temperature, growth rate, and the degree of carbon supersaturation in the diamond-forming fluids (J.W. Harris et al., “Morphology of monocrystalline diamond and its inclusions,” Reviews in Mineralogy and Geochemistry, Vol. 88, No. 1, 2022, pp. 119–166). If a diamond forms under changing conditions, it might not have a regular octahedral or cubic morphology but a combination of both. In some cases, diamonds grow without any well-defined crystal faces and are referred to as “irregular diamonds” (see examples in R. Tappert and M.C. Tappert, Diamonds in Nature: A Guide to Rough Diamonds, Springer-Verlag, Berlin, 2011, p. 28). While octahedral or cubic faces cannot always be identified visually in irregular diamonds, the morphology can be inferred by etch features left on the diamond by fluids in the mantle or during kimberlite eruption. Trigons and tetragons are the most common of these etch features—restricted to octahedral and cubic crystal faces, respectively.

Figure 2. Flat-bottom and pointed-bottom trigons (surface features restricted to an octahedral crystal face) preserved on an unpolished portion of the diamond. A circular etch pit overprinting a pointed-bottom trigon indicates a late-stage diamond dissolution event that postdated the formation of the trigon. Photomicrograph by Matthew Hardman; field of view 1.26 mm.

Figure 3. Tetragons (surface features restricted to the cubic crystal face) preserved at the culet of the diamond. Photomicrograph by Matthew Hardman; field of view 1.26 mm.
The Carlsbad laboratory recently examined a 2.00 ct Fancy brown-greenish yellow diamond with both trigons and tetragons on its surface (figure 1). The trigons were located within a small indented natural near the table facet, while the tetragons were preserved within an indented natural at the culet (figures 2 and 3). Co-occurring trigons and tetragons are very uncommon and indicate an irregular morphology, characterized by both octahedral and cubic growth.
This stone was identified as a chameleon diamond. For such a classification, the diamond must include a green color component, show phosphorescence to short-wave UV, and change from a greenish color to a yellow or orange color with gentle heating or when kept in the dark for an extended period (C.M. Breeding et al., “Natural-color green diamonds: A beautiful conundrum,” Spring 2018 G&G, pp. 2–27). These diamonds typically have a broad visible absorption band centered at approximately 480 nm and are referred to as “480 nm band diamonds.” A study on rough yellow diamonds from Canada showed that all of those colored by the 480 nm absorption band have irregular morphology (M.Y. Lai et al., “Yellow diamonds with colourless cores – evidence for episodic diamond growth beneath Chidliak and the Ekati mine, Canada,” Mineralogy and Petrology, Vol. 114, 2020, pp. 91–103), suggesting that diamonds with the 480 nm absorption band may form under changing conditions in the mantle.
Trigons on diamond have two major morphologies: either a flat bottom or a pointed bottom (pyramidal). The type of trigon is primarily dependent on the temperature and pressure at the position where diamond dissolution occurs, as well as on the carbon dioxide and water contents in the fluid that etches diamonds. Experimental work indicates that fluids with higher carbon dioxide content tend to produce pointed-bottom rather than flat-bottom trigons (Y. Fedortchouk, “A new approach to understanding diamond surface features based on a review of experimental and natural diamond studies,” Earth-Science Reviews, Vol. 193, 2019, pp. 45–65). Both forms of trigons were observed on the chameleon diamond we examined, as well as a circular etch pit overprinting a pointed-bottom trigon (figure 2). Unlike pointed-bottom trigons, circular pits are typically created by fluids with low carbon dioxide contents, indicating a late-stage etching event after the formation of the trigon.
The combination of surface features provides clues for the morphology of diamonds in rough form, as well as the interactions between diamonds and fluids throughout their journey from mantle residence to the earth’s surface. Source: GIA @topic:4


Title: CVD Diamond Over 34 Carats Abstract: Figure 1. This 34.59 ct CVD-grown diamond (24.94 × 13.95 × 9.39 mm), produced by Ethereal Green Diamond in India, is the largest GIA has tested. Photo by Johnny (Chak Wan) Leung.
Chemical vapor deposition (CVD) growth technology has advanced significantly over the last two decades. In this study, we report on the largest CVD gem diamond GIA has encountered, recently tested in the Hong Kong laboratory. This emerald-cut diamond weighing 34.59 ct and measuring 24.94 × 13.95 × 9.39 mm (figure 1) was produced by Ethereal Green Diamond in India. It had G color and VS2 clarity. Small black graphite inclusions were found. Some stood alone inside the body, while others formed clusters of clouds located between growth layers. Microscopic observation showed a weak oily or wavy graining when looking through the table facet, a feature sometimes seen in CVD gem diamonds. It tends to appear more prominently in CVD diamonds with high amounts of strain and a strong birefringence pattern when viewed through crossed polarizers (figure 2).

Figure 2. A high amount of strain and a strong birefringence pattern were observed using crossed polarizers. Photomicrograph by Ka Wing Tam; field of view 15.92 mm.
Infrared absorption spectroscopy revealed no absorption related to nitrogen, which is consistent with type IIa diamond. However, a weak absorption related to boron (an absorption peak at ~2800 cm–1) was detected, corresponding to around 2 ppb of boron impurity. This trace amount of boron was very likely due to contamination during diamond growth. There are different opinions on whether this trace contamination should be considered in diamond type classification.

Figure 3. Left: The PL spectrum with 514 nm laser excitation under liquid nitrogen temperature showed features of treated CVD diamond. Right: The PL spectrum with 457 nm laser excitation under liquid nitrogen temperature recorded a strong H3 defect and a negligible 467.6 nm center.
Photoluminescence (PL) spectroscopy was performed at liquid nitrogen temperature (–196°C) with several laser excitations (figure 3). In addition to strong emissions from NV0 and NV– centers at 575 nm and 637 nm, respectively, moderately strong doublet emissions from SiV– at 736.6 and 736.9 nm were recorded. A weak emission at 946.4 nm, possibly from the SiV0 defect, was also observed. Other important emission features included a strong emission from the H3 defect at 503.2 nm and a weak emission band with peaks at 566.0, 566.7, and 567.7 nm. The emission at 467.6 nm, which is common in as-grown CVD diamonds, was reduced by high-temperature treatment. These observations and spectroscopic features confirmed that this CVD diamond was annealed under high pressure and high temperature (HPHT) to improve its color appearance. In contrast, no post-growth color treatment was applied to the 16.41 ct CVD lab-grown diamond tested a year earlier in the New York laboratory (W. Wang et al., “New record size for CVD laboratory-grown diamond,” GIA Research News, January 27, 2022).

Figure 4. DiamondView imaging of the 34 ct CVD diamond revealed at least eight growth steps. Image by Ka Wing Tam.
DiamondView fluorescence imaging showed green and blue colors with a banded pattern. Typical CVD growth striations were clearly visible (figure 4). Green fluorescence was from the H3 defect, produced during HPHT annealing. This banded structure revealed at least eight growth steps to achieve sufficient depth for this large diamond. Additionally, strong blue phosphorescence with similar banding was detected in the DiamondView.
This very large CVD diamond represents a milestone in CVD growth. Mined diamonds with similar size and quality are very rare. We will continue monitoring developments in gem diamond growth technology to ensure all diamonds are properly identified in GIA laboratories. Source: GIA @topic:4


Title: Natural Diamond with CVD-Like Fluorescence Pattern Abstract: DiamondView imaging of the pavilion facets for this HPHT-treated natural diamond shows graining and zoning that resemble those of a laboratory-grown CVD diamond with HPHT treatment. The inset shows the DiamondView image of an HPHT-treated CVD-grown diamond. Images by Jemini Sawant.
Fluorescence images collected using the DiamondView are very useful in identifying whether a diamond is natural or laboratory grown (S. Eaton-Magaña and J.E. Shigley, “Observations on CVD-grown synthetic diamonds: A review,” Fall 2016 G&G, pp. 222–245). In many cases, type II natural diamonds show varying dislocation networks in these images. Meanwhile, high-pressure, high-temperature (HPHT) synthetic diamonds show cuboctahedral growth patterns, and chemical vapor deposition (CVD) laboratory-grown diamonds show growth striations.
The Mumbai laboratory recently received a 0.40 ct colorless round brilliant for diamond grading service. Spectroscopy identified it as a type IIa diamond, and it was examined further for color origin determination. DiamondView imaging showed uncommon and interesting patterns. In the figure above, the lower right is dominated by green fluorescence while the upper left shows mainly blue fluorescence, with a clear and straight boundary. Detailed examination revealed numerous sharp and clear dislocation lines in multiple orientations in both parts of this diamond. These dislocation lines were introduced by plastic deformation and provide strong evidence that the diamond crystallized in nature. It should be pointed out that the interface layer seen in the fluorescence image is uncommon for natural diamonds but similar to that of CVD laboratory-grown diamonds. Further photoluminescence spectroscopy analysis confirmed this natural diamond was treated by annealing under high pressure and high temperature to improve its color, reinforcing our assertion that advanced analytical study is often crucial in identifying a diamond.
Natural diamonds with fluorescence patterns similar to those of HPHT synthetic diamonds have also been reported previously (Spring 2013 Lab Notes, pp. 45–46). With recent advances in technology, manufactured diamonds with unique features have become more widely available on the market. Therefore, it is more important than ever to scrutinize each feature to ensure the appropriate identification results in such scenarios. Since natural and manufactured diamonds are structurally identical, we often need to rely on advanced gemological and spectroscopic data, particularly for such low-nitrogen diamonds, to correctly identify their origin. Source: GIA @topic:4


Title: Green Diamond, Treated with Radioactive Salt Abstract: Figure 1. This 3.17 ct round brilliant cut diamond owed its Fancy Deep green color to irradiation with radioactive salts. Photo by Jian Xin (Jae) Liao.

Recently submitted to the East Coast laboratory was a 3.17 ct round brilliant cut diamond, color graded as Fancy Deep green (figure 1). Natural diamonds of this color are very rare and desirable.

Examination with a gemological microscope revealed a very unusual surface coloration. The surface had a mottled pattern created by very shallow green staining, likely from exposure to radiation (figure 2). This unusual feature is rarely observed on natural diamond surfaces or facets. Natural radiation staining on the surface of a diamond crystal would be mostly removed during faceting.

Figure 2. Observed at 35× magnification, the diamond shows a mottled effect created by shallow green radiation stains. Photo by Jian Xin (Jae) Liao.
The stone owes all of its green color to these shallow radiation stains. Today, most artificially irradiated diamonds are treated with a low-energy electron beam. This often results in shallow color zoning that penetrates into the stone and aligns with the facet shape. In this case, the shallow staining was created using the older method of exposing the diamond to radioactive salts for an extended period of time. Mainly used on polished stones, this method leaves surface contamination.
Stones irradiated in this fashion can have residual radiation, so we tested this stone using a Geiger counter. Only background radiation was detected, indicating that the treatment likely occurred decades earlier. Thus, this diamond posed no radiation hazards. Sir William Crookes first discovered radiation’s effects on diamond color by conducting a series of experiments using radium salts in 1904. Although rarely encountered today, these types of treated diamonds still show up in the trade. A careful inspection of the surface in diffused lighting is the most effective means of revealing the diagnostic surface coloration. Source: GIA @topic:4


Title: Orange Diamond with Unusual Color Origin Abstract: Figure 1. This 1.53 ct diamond was color graded as Fancy Intense pinkish orange. Spectroscopic analysis revealed it was type IIa and dominated by an approximately 550 nm band absorption, which usually introduces a pink-red color in natural diamonds rather than orange. Photo by Jian Xin (Jae) Liao.

              Orange bodycolor in diamond is usually caused by an absorption band centered at approximately 480 nm or by a high concentration of isolated nitrogen. Meanwhile, it is well known that the 550 nm absorption band often introduces pink to red colors. Physical models of these two optical centers have not been resolved yet. The New York laboratory recently examined an orange diamond whose color was attributed mainly to the 550 nm absorption band.

This 1.53 ct heart-shaped diamond (6.84 × 7.76 × 3.88 mm) was color graded as Fancy Intense pinkish orange (figure 1). Color was distributed evenly throughout the stone, which was very clean and showed no internal features under the microscope. The absorption spectrum in the infrared region revealed that it was a regular type IIa diamond, with no nitrogen-or hydrogen-related absorptions. The UV-Vis region showed a broad absorption band centered at ~550 nm and its corresponding band at ~390 nm, absorption features typical of natural type IIa pink diamonds. From the optical centers detected, we would not expect this diamond to show a dominant orange bodycolor.

The reason for this discrepancy is not fully understood. Our finding from this stone demonstrates the complexity of diamond color origin. Source: GIA @topic:4


Title: Diamond with Cavities Showing Radiation Evidence Abstract: Figure 1. This 0.70 ct natural diamond contained an inclusion of wollastonite and CaSiO3-breyite with a large disk-like graphitic fracture due to exhumation from the mantle. Photomicrograph by Garrett McElhenny; field of view 1.15 mm.
The Carlsbad laboratory recently examined a 0.70 ct, E-color round brilliant. Infrared spectroscopy showed this to be a type IIa diamond, so we performed a variety of additional spectroscopy and imaging to verify its natural origin. This diamond also had I1 clarity due to a large inclusion under the table (figure 1). Raman analysis of the inclusions verified that this crystal was a metastable composite of the minerals wollastonite (CaSiO3) and CaSiO3-breyite (E.M. Smith et al., “The very deep origin of the world’s biggest diamonds,” Winter 2017 G&G, pp. 388–403), which indicates a sublithospheric origin. These minerals are believed to be the lower-pressure phases of CaSiO3-perovskite. Around these minerals were large disk-like graphitic fractures indicating inclusion expansion as pressures on the diamond reduced during exhumation from the mantle. The other inclusion present was unidentifiable due to its graphitic casing. Recent research of inclusions in other type II diamonds shows that many, if not most, have a superdeep origin (again, see Smith et al., 2017). This stone is one more example of diamonds forming at incredible depths of 360–750 km before being transported to near the surface.

Figure 2. This DiamondView fluorescence image of the table and crown facets shows green fluorescence halos around two cavity features (as indicated by the red arrows). The green fluorescence, caused by the H4 defect, was caused by localized radiation within those cavities while the diamond resided within the earth’s crust and was exposed to radioactive fluids.
But even after such a tumultuous journey, the earth was not finished writing the story of this diamond. While in the earth’s crust, the diamond was exposed to radioactive fluids, particularly in etch channels now in the form of cavities on the table and crown facets. DiamondView imaging revealed fluorescing green halos around these cavities (figure 2). Although these isolated areas of fluorescence around the cavities indicated they had likely been filled with a radioactive fluid, there was none of the greenish color or radiation staining that would likely accompany higher radiation doses.

Photoluminescence (PL) mapping with 532 nm (figure 3) and 455 nm (figure 4) excitation shows a pronounced increase in radiation-related defects such as GR1, 3H, and TR12 and other vacancy-related peaks such as NV–, NV0, and H4 (a B aggregate with an additional vacancy) within these cavities (figures 3 and 4). Although this diamond was type IIa, there was sufficient nitrogen to form related defects that could be observed at the lower level of detection of PL spectra.

Figure 3. Left: A 532 nm PL map of the top cavity pictured in figure 2 shows a false-color image of GR1 intensity, revealing much higher concentrations along the perimeter of the cavity. Right: A plot of calculated concentrations for several vacancy-related centers from the PL map at left and collected at 3 μm intervals along the red line in the left image. The plot shows the elevated concentrations along the cavity edges of GR1 (neutral vacancy; zero-phonon line [ZPL] at 741.2 nm), NV0 (ZPL at 575 nm), and NV– (ZPL at 637 nm).

Figure 4. A photomicrograph (top left) of the lower cavity pictured in figure 2 is also shown in a 455 nm PL map (top right) displaying a false-color image of the H4 intensity. The corresponding spectra (bottom) for two points from the red and blue color regions are shown. Although the spectra were collected at only ~50 μm distance, there are pronounced differences in peak intensities. The diamond Raman peaks within the two spectra are scaled as equal. Photomicrograph by Sally Eaton-Magana.
A number of other peaks often seen in natural diamonds but not yet identified, such as those at 490.7, 498, and 505 nm, also showed elevated concentrations in these cavities; their enhanced presence due to natural radiation was consistent with prior observations (I.A. Dobrinets et al., HPHT-Treated Diamonds: Diamonds Forever, 2013, Springer). The width of the fluorescence halos in figure 2 and the elevated GR1 shown in figure 3 is approximately 30 μm, consistent with the penetration depth of alpha radiation (S. Eaton-Magaña and K.S. Moe, “Temperature effects on radiation stains in natural diamonds,” Diamond and Related Materials, Vol. 64, 2016, pp. 130–142). We know this radioactive fluid exposure must have occurred in the crustal region because many of the features, such as 3H, would not survive if this exposure occurred at greater depths and, therefore, higher temperatures.
These localized effects of radiation are particularly interesting because the dose was low enough to not impart green coloration or green to brown radiation stains. Nevertheless, the radioactive fluids left their mark on this diamond with the green fluorescence halos around the cavities, providing an excellent example of how many peaks are enhanced by radiation compared with the unaffected portions within the remainder of the diamond. It is also interesting that two distinctly different geological conditions and depths within the earth both contributed to the gemological characteristics of this diamond. The sublithospheric depths imparted some notable minerals as evidence of its superdeep formation, and radioactive fluids within the shallow, crustal region of the earth created the green-fluorescing halos and other radiation features. Source: GIA @topic:4


Title: Omphacite and Chromite: A "Bimineralic Inclusion" in Diamond Abstract: Sometimes a clue to the identity of an inclusion is its color. Diffuse transmitted lighting reveals the colors of the omphacite (left) and chromite (right) crystals composing a "bimineralic inclusion" in a 90-point diamond. Photomicrograph by Nathan Renfro; field of view 0.95 mm.

The micro-world of diamonds is fascinating not only to gemologists interested in inclusions but also to mineral physicists who study the deep earth, arguably one of the last frontiers and one not yet accessible to us. Diamond inclusions offer a window into that world and help us piece together its nature to unravel the mysteries of the earth’s very formation (J.I. Koivula and E.A. Skalwold, “The microworld of diamonds: Images from the earth’s mantle,” Rocks & Minerals, Vol. 89, No. 1, 2014, pp. 46–51). Sometimes even relatively common inclusions in diamond present an uncommon sight.

In this case, two minerals identified by Raman microspectroscopy, omphacite and chromite, are in such close association that they appear joined (see above). Such a “bimineralic inclusion” poses the question of how they might have ended up that way: Was it just fate or attraction? There is even the possibility that they were a single mineral at the time of inclusion into the diamond but separated when pressure and temperature dropped as the diamond found its way to the earth’s surface. Future detailed chemical analysis of this pair may yield valuable information about the earth’s interior, including the compositions, pressures, and temperatures of the host rocks in which the diamonds formed.

Many gemologists are familiar with so-called carbon spots in diamonds. Often these are actually chromite crystals—not carbon at all, but rather a chromium-rich iron oxide mineral of the spinel group. If thin enough, these may appear dark red-brown to yellowish brown in transmitted light, as seen in this specimen. Chromite is classified in both the peridotitic and eclogitic inclusion suites found in diamonds. By contrast, the omphacite crystal next to it is a monoclinic pyroxene mineral (clinopyroxene) that is typically pale to dark grayish green or grayish blue in transmitted light and considered a member of the eclogitic suite of inclusions found in diamonds. This inclusion specimen is not only worthy of the photomicrographer’s artistry but also a very valuable portion of the earth’s interior puzzle, which is slowly being put together one piece at a time. Source: GIA @topic:4


Title: Treated “Nickel-Rich” Green Diamond Abstract: Figure 1. This 2.12 ct Fancy yellow-green diamond owes its color to both the nickel-related absorption band and the artificially introduced GR1 absorption. Photo by Jian Xin (Jae) Liao.
Natural-color green diamonds are extremely rare. The cause of color for most green diamonds is attributed primarily to radiation damage resulting from exposure to radioactive elements over geologic time (W. Wang et al., “Natural type Ia diamond with green-yellow color due to Ni-related defects,” Fall 2007 G&G, pp. 240–243). The New York laboratory recently received a 2.12 ct pear-shaped diamond measuring 9.52 × 7.24 × 4.27 mm that was graded as Fancy yellow-green (figure 1), and testing attributed the color to several mechanisms.

Figure 2. DiamondView imaging reveals greenish yellow fluorescence that is typical for nickel-rich diamond. Image by Luthfia Syarbaini.
Microscopic examination revealed dark crystals and clouds throughout the stone, and infrared spectroscopy confirmed it was a type Ia diamond. DiamondView imaging showed greenish yellow fluorescence (figure 2), typical for “nickel-rich” diamond.

Figure 3. UV-Vis-NIR spectra show the nickel-related absorption band and 883 peak in both a natural diamond from the GIA database and the 2.12 ct treated diamond. In addition, the spectrum for the treated diamond shows the GR1 peak around 740 nm. Spectra are offset vertically for clarity.
The ultraviolet/visible/near-infrared (UV-Vis-NIR) absorption spectrum showed a nickel-related absorption band at around 670 nm, a peak at 883 nm (an attributed peak in “nickel-rich” diamonds), and a GR1 (general radiation damage) peak at about 740 nm (figure 3). This is an uncommon combination of spectral features in diamond. The Ni-related absorption band is usually responsible for the green color in this type of diamond (Fall 2013 Lab Notes, pp. 173–174; Spring 2022 Lab Notes, pp. 50–51). In this particular diamond, the yellow-green color saturation can be attributed to both the nickel-related absorption band and the GR1 absorption. We have not observed these two features together in natural-color green diamond. Additional testing and gemological observations confirmed that the GR1 peak was artificially introduced, and we concluded that the color was treated. The color was likely a lighter and less saturated green before treatment.
This stone illustrates the importance of combining gemological observations with spectroscopic characteristics to separate natural- and treated-color green diamonds. Source: GIA @topic:4


Title: Quarterly Crystal: Cr-Diopside in Diamond Abstract: Figure 1. Measuring 7.59 mm in largest dimension and weighing 1.84 ct, this partially etched diamond octahedron contains a bright green inclusion of chromium diopside. Photo by Robison McMurtry.

Brightly colored mineral inclusions in diamonds are rare. Some examples of these rarities are dark blue kyanite, yellowish orange almandine-pyrope, and deep purplish red pyrope garnet. This year’s first Quarterly Crystal offering expands on this bright inclusion theme with a transparent colorless partially etched octahedron from the Kimberley mine in South Africa. Shown in figure 1, the diamond measures 7.59 × 6.59 × 4.79 mm and weighs 1.84 ct.

Situated along the edge of one of the octahedral planes, the diamond crystal plays host to a bright green transparent elongated mineral inclusion. Laser Raman microspectrometry was used to identify this included crystal as diopside, and the bright green color results from a trace amount of chromium.

Figure 2. Rich green transparent crystals of chromium diopside are very uncommon inclusions in diamond. The example shown here has a typical rounded, etched habit. Photomicrograph by Nathan Renfro; field of view 1.80 mm.
As a diamond inclusion, chromium diopside is a medium to deep green transparent mineral with a vitreous luster. As shown in figure 2, it typically forms as rounded protogenetic mineral grains. Geologically, the presence of a Cr-diopside inclusion in a diamond is an indicator that the host diamond formed in a rock type known as peridotite. Source: GIA @topic:4


Title: 15 Carat HPHT Synthetic Diamond Abstract: Figure 1. This 15.32 ct cushion modified brilliant, with grades equivalent to H color and I1 clarity, is the largest HPHT synthetic diamond graded by GIA. Photo by Robison McMurtry.

The Carlsbad laboratory recently examined an HPHT synthetic diamond that is now the largest faceted lab-grown diamond examined by GIA. The specimen was a cushion modified brilliant weighing 15.32 ct, with grades equivalent to I1 clarity and H color (figure 1). The largest previously reported fully faceted synthetic diamonds were a 10.02 ct emerald-cut HPHT-grown (equivalent to E-color; Summer 2016 Lab Notes, pp. 195–196) and a 10.08 ct emerald-cut HPHT-grown diamond (equivalent to Fancy Deep blue; Winter 2016 Lab Notes, p. 416). The 15.32 ct synthetic contained large metallic flux inclusions (figure 2) as well as numerous fractures. Examination under crossed polarizers revealed no strain patterns, except for small strain fields around the metallic flux inclusions.

Figure 2. The metallic flux inclusions present in the synthetic diamond. Several rod-shaped structures can be seen, as well as an inclusion with a trapezoidal shape. Photomicrograph by Jonathan Muyal; field of view 4.79 mm.

Figure 3. Left: This DiamondView fluorescence image of the HPHT-grown diamond’s pavilion shows a combination of apparent layered growth, along with the more common cross-pattern morphology seen in HPHT synthetics. The area of the pavilion shown here also indicates the region of PL mapping. The red arrow indicates the regions that showed a high concentration of nickel, silicon, and NV center defects compared to the remainder of the mapped region. Above this more heavily doped layer is the metal rod inclusion also seen in figure 2. Right: The patterning in the corresponding phosphorescence image closely resembles the fluorescence image. A thin layer of material showing orange (~580 nm) phosphorescence is indicated by the white arrow.
The infrared absorption spectrum showed no detectable boron or nitrogen, indicating that the sample was type IIa. DiamondView imaging did reveal blue phosphorescence, which is characteristic of boron impurities (figure 3, right), but any boron present was below the detection level of the FTIR spectrometer. Photoluminescence (PL) spectroscopy taken with the 514 nm laser revealed the presence of the negative silicon vacancy defect at 737 nm; the neutral nitrogen-vacancy center was also seen at 575 nm. The nickel-related doublet at 882/884 nm was seen in the 830 nm PL spectrum. Energy-dispersive X-ray fluorescence (EDXRF) revealed the presence of iron and cobalt which, together with the nickel feature in the PL, gives insight into the flux mixture used to grow this specimen.
Due to their growth method, HPHT synthetics generally show very distinct growth patterns when examined in the DiamondView. While they can show dramatic differences in fluorescence color, these are generally seen within angular zones that radiate from the center and extend through the volume of the specimen. In contrast, CVD synthetic diamonds are grown as layers. The start/stop events of the CVD reactor result in distinct changes in diamond chemistry that are visible in DiamondView fluorescence images; the changes in fluorescence color are usually parallel due to the layered growth. Therefore, it was quite interesting to see DiamondView fluorescence patterns in which the pavilion section toward the culet far more closely resembles the layers seen in CVD growth than the cross-pattern color zoning often seen in HPHT synthetics (figure 3, left). The fluorescence zoning commonly found in HPHT-grown material can be seen towards the girdle section of this sample. PL mapping at liquid nitrogen temperatures was used to verify the DiamondView observations and detect the distribution of defects through the synthetic diamond (for more on the PL mapping collection technique see L.C. Loudin, “Photoluminescence mapping of optical defects in HPHT synthetic diamond,” Summer 2017 G&G, pp. 180–189). We mapped the PL spectra of the region shown in figure 31 using 532, 633, and 785 nm laser excitations. One of the layers (red arrow in figure 3) in particular showed greatly elevated concentrations of nickel (as the 883/884 nm doublet; average concentration in this area was 5× greater than the average intensity of the doublet in other portions of the mapped pavilion), silicon (as the SiV– defect at 737 nm; 10× greater), and NV centers (NV0 at 575 nm [2× greater] and NV– at 637 nm [2.5× greater]). This particular layer also showed orange phosphorescence in the DiamondView, assumed to be centered at approximately 580 nm (U.F.S. D’Haenens-Johansson et al., “Large colorless HPHT synthetic diamonds from New Diamond Technology,” Fall 2015 G&G, pp. 260–279), in addition to the more common blue phosphorescence.
The specific growth process that creates the apparent layers in this HPHT synthetic is unknown, but it may be a necessary condition to grow synthetic material in such large sizes. The manufacturer may use successively larger seeds in separate growth runs or alter the pressure or temperature conditions within a single growth experiment. It should be noted that this growth feature, while layered in appearance, is quite different from CVD growth layers, which have sharp boundaries and are often differently colored. The chemistry collected on the layered portion was consistent with HPHT growth and not CVD growth; the chemistry was also consistent between the layered portion and the cross-patterned portion of growth. Therefore, a CVD seed was not used to grow this specimen. Similar layers were observed in the DiamondView images of the 10.08 ct blue HPHT synthetic (unpublished data). However, the size of this most current specimen demonstrates that the growth technologies and processes are continuing to improve and continuing to impress. Source: GIA @topic:4