Publish Year: - Title: Where Do Blue Diamonds Come From? Blue Diamonds Have a Surprising “Superdeep” Origin and a Link to Ancient Oceans Abstract: Figure 1: Blue boron-bearing diamond, with dark inclusions of a mineral called ferropericlase that were examined as part of this study. This gem weighs 0.03 carats. Photo by Evan M. Smith.

This is an extended abstract of the article ‘Blue boron-bearing diamonds from Earth’s lower mantle,’ published in the journal Nature. GIA Research Scientist Evan Smith is the lead author of the article, with co-authors Steven B. Shirey, Carnegie Institution for Science; Stephen H. Richardson, University of Cape Town; Fabrizio Nestola, University of Padova; Emma S. Bullock, Carnegie Institution for Science; Jianhua Wang, Carnegie Institution for Science; and Wuyi Wang, Gemological Institute of America.

Type IIb diamonds are a rare variety of diamond distinguished by having boron within the crystal structure, which can impart an attractive blue color. The famous Hope diamond is a perfect example of this blue diamond variety. Type IIb diamonds have long remained a geological enigma, but new research published in the August 2, 2018 issue of Nature reveals they are “superdeep” diamonds, meaning they crystallized much deeper in the earth than most other gem diamonds. Remarkably, the boron atoms contained in these blue gems may have originally been derived from ancient oceans.

Figure 2: Rough blue diamonds weighing between 0.7 and 3 carats each. Examining rough samples, such as these, can be a good opportunity to see inclusions, because inclusions are often skillfully cut and polished away to optimize the appearance of the faceted gem. Photo by Evan M. Smith.
Boron is an element that is strongly concentrated at Earth’s surface. But in the mantle, where diamonds grow, the concentration of boron is extremely low. The boron content of type IIb diamonds is therefore unexpected and challenging to explain. Blue diamonds have intrigued scientists for decades, but the high value and rarity of these gems and their near lack of mineral inclusions have been major hurdles to research.

Prior to this study, no mineral inclusion had ever been identified in a type IIb diamond. However, systematic screening of diamonds submitted to GIA over two years made it possible to find and examine 46 type IIb diamonds with inclusions. By studying the inclusions – small pieces of material trapped in the diamond during crystallization – the research team was able to deduce the host rock and depth where the diamonds grew. The minerals identified in these inclusions are only found together at extremely high pressures, very deep in the earth, leading to the conclusion that type IIb diamonds formed at least as deep as the transition zone (410–660 km), reaching into the lower mantle (>660 km). For comparison, this is approximately four times deeper than most other kinds of diamonds, which form near the base of old and thick continents at depths of about 150–200 km.

The inclusions also show that, at this great depth, the diamonds grew in the presence of ocean crust which was carried down to the lower mantle by the conveyor-belt-like process of subduction. The connection with subducted oceanic lithosphere suggests that boron, responsible for the blue color in type IIb diamonds, may have been carried down from the earth’s surface.

Figure 3: Inclusion of calcium silicate in a 0.21 carat blue diamond seen with the field view of 1.42 mm wide. This inclusion is evidence that the diamond grew at extreme depths in the mantle. Photo by Evan M. Smith.
When seawater infiltrates the ocean floor, it causes chemical reactions that deposit boron into the oceanic lithosphere. This new study proposes a model whereby some of this boron is subducted with hydrous (water-bearing) minerals down to the lower mantle. At this great depth, the increased temperature and pressure break down the hydrous minerals, which then release a boron-enriched fluid that triggers diamond growth. Many of the inclusions in the blue diamonds that Smith and his colleagues examined have coexisting methane and hydrogen as a thin layer surrounding the solid minerals, providing evidence of diamond growth from such a boron-enriched hydrous fluid.

This new study reveals not only that type IIb diamonds are among the deepest diamonds ever found, but also that boron and maybe even water can be carried from the ocean deep into the mantle by the process of subduction. This is a key observation for our understanding of mantle geochemistry and plate tectonic processes.

August 2018 Nature cover “Deep Blue,” explores Evan M. Smith’s research on type IIb blue diamonds that formed when boron hitchhikes to Earth’s lower mantle on oceanic tectonic plates. Image courtesy of Nature.
Until recently, it was widely held that superdeep diamonds are always small and never of gem quality. This notion is upended by the present discovery that blue boron-bearing diamonds are superdeep, in addition to the 2016 finding that relatively large and pure (CLIPPIR) diamonds are also superdeep. Thus, many of the world’s most expensive and dazzling gem diamonds are superdeep diamonds, making them invaluable physical samples from the convecting mantle hundreds of kilometers beneath our feet.

Dr. Evan Smith will present this research at GIA’s International Gemological Symposium, Oct. 7-9 in Carlsbad, CA. For more information on the program and to register, visit symposium.GIA.edu. @topic:10


Publish Year: - Title: Summer 2017 G&G: Russian Diamonds and PL Mapping of Synthetic Diamonds, Plus Sapphire Inclusions Chart Abstract: The Fall 2017 issue of Gems & Gemology covers topics across the gemological spectrum, from HPHT synthetic diamond identification criteria to natural saltwater pearls harvested during the Columbian era and the current state of Colombia’s emerald industry. Other highlights include a study of photoluminescence spectra in emerald as a method of determining geographic origin, a review of synthetic star corundum from mid-twentieth century Germany, and an examination of the material known in the industry as “dalmatian jasper.”
OBSERVATIONS ON HPHT-GROWN SYNTHETIC DIAMONDS: A REVIEW

While some HPHT synthetic inclusions appear transparent, most appear to be pieces of dark solidified metal flux. A variety of shapes are possible, including thin rods and irregular shapes, and some are associated with feathers. These metallic inclusions can create a magnetic attraction. Photo by Sally Eaton-Magaña.
While synthetic diamonds grown by the high-pressure, high-temperature (HPHT) method have been commercially available since the mid-1990s, the technology has made great strides in the last decade. In the issue’s lead article, GIA’s Sally Eaton-Magaña, James E. Shigley, and Christopher M. Breeding provide insight into the HPHT-grown material available on the market, including statistical data about the cut, color, and clarities available as well as identification criteria for gemologists.
SALTWATER PEARLS FROM THE PRE- TO EARLY COLUMBIAN ERA: A GEMOLOGICAL AND RADIOCARBON DATING STUDY

These natural pearls, reportedly from thepre- to early Columbian era, represent some of the 85samples examined in the study. They were discoveredalready drilled but were only recently strung as anecklace. The center blister pearl (31.41 × 16.86 ×10.25 mm) consists of multiple small pearls thatformed as an aggregate. Photo by Sood Oil (Judy)Chia.
Pearls were treasured by the indigenous people of the Americas and by the Spanish colonists. Oyster beds in the Caribbean were heavily exploited during the first half of the sixteenth century before oysters became scarce. A supplier came into possession of 85 pearls, reportedly from Central or South America and dating from the pre- or early Columbian era. A team from GIA and the Gübelin Gem Lab, led by Chunhui Zhou, analyzes the pearls through a variety of methods to validate these claims.
PHOTOLUMINESCENCE SPECTRA OF EMERALDS FROM COLOMBIA, AFGHANISTAN, AND ZAMBIA

Emerald crystals from Zambia (left), Colombia (top right), and Afghanistan (bottom right). Each emerald’s hexagonal prismatic crystal habit has been enhanced by polishing flat the two hexagonal end faces (perpendicular to the crystal’s c-axis) and two or more prism sides (parallel to the c-axis). Photo by D.B. Thompson.
Photoluminescence (PL) in emerald arises from trace chromium impurities. An emerald’s PL spectrum displays two features that can vary depending on the stone’s origin. Lead author David Brian Thompson and his team examine the PL spectra of 48 emeralds from Colombia, Afghanistan, and Zambia to provide evidence for or against possible geographic origins.
SYNTHETIC STAR SAPPHIRES AND RUBIES PRODUCED BY WIEDE’S CARBIDWERK, FREYUNG, GERMANY

Three synthetic blue star sapphire cabochons and one synthetic star ruby cabochon in direct sunlight. The ruby weighs 8.92 ct and measures 13.2 × 11.0 mm; the sapphire at the bottom left weighs 3.67 ct and measures 9.1 mm in diameter. Photos by K. Schmetzer.
During the 1950s, Wiede’s Carbidwerk patented a method of growing star synthetic corundum for the commercial market. The company sold these goods through the late 1970s, though the samples from the 1960s and beyond differ slightly from their earlier counterparts. Karl Schmetzer and his coauthors explore the variant of the Verneuil process that Wiede’s used to grow these synthetics.
TRUE COLORS OF “DALMATIAN JASPER”

Dalmatian stone samples examined in this study reveal a spotted appearance connected with the presenceof alkali amphiboles disseminated through feldspar-quartz matrices. Left: A rough block-shaped specimenmeasuring 1.5 × 1.5 × 1 cm. Right: A polished bracelet (1 cm bead diameter) alongside a pendant measuring 3 cmin length. Photos by Tomasz Powolny.
The decorative gemstone known in the trade as “dalmatian jasper” due to its black spots (identified as arfvedsonite) is not widely discussed in the published literature. Tomas Powolny and Magdalena Dumańska-Słowik investigate the stone’s mineralogical composition and properties. On the basis of the study, they suggest the use of “dalmatian stone,” as the material does not meet the gemological definition of jasper.
THE COLOMBIAN EMERALD INDUSTRY: WINDS OF CHANGE

Colombian emerald-producing areas such as Muzo have a long tradition of independent mining. The hope of finding the stone that will change their lives is a strong motivator for miners, but bringing them into a formal system is challenging. Photo by Andrew Lucas.
Emerald mining in Colombia dates back more than a thousand years. Yet its greatest opportunities may still lie ahead, as multinational companies invest in the industry as transparency and traceability come to the forefront. In this field report, an expedition led by Colombian gemologist Darwin Fortaleché documents the recent changes in the country’s mine-to-market emerald industry.
LAB NOTES

A Brazilian kimberlite yielded a 50.8 ct rough type Ia diamondwith a dodecahedral habit, the result of resorption. Right: This 20.1ct round brilliant with I color was cut from the Brazilian rough.
Updates from GIA’s labs include reports on a high-quality diamond from Brazilian kimberlite, synthetic overgrowth on a flux-heated ruby and a beryllium-diffused sapphire, and separation of synthetic melee from natural diamond using GIA’s iD100 screening device.
MICRO-WORLD

Reminiscentof a flower in a rainstorm,this inclusionscene has been dramaticallyenhanced usingmodified Rheinberg illuminationto accentuatea growth blockageand thin-film rosettewithin a sapphire fromElahera, Sri Lanka.Photomicrograph byJonathan Muyal; fieldof view 1.34 mm.
G&G’s photomicrography section features a flower-like inclusion in a Sri Lankan sapphire, silvery rutile inclusions in quartz, and fluorite hosting eye-visible barite inclusions.
GEM NEWS INTERNATIONAL

These sapphires (0.64–8.27 ct) are from Antangand Gombe, in northern Nigeria. Photo by ShunsukeNagai.
The Fall GNI section includes an update on Mozambique ruby mining, an analysis of blue-green pyrope-spessartine with high vanadium, and an examination of sapphires reportedly from new sources in northern Nigeria. @topic:8


Publish Year: - Title: Fall 2015 G&G: Trapiche Emeralds, Synthetic Diamonds and a Large Diamond Source Abstract: The lead article in this issue is an in-depth study on the geological formation and growth of Colombian trapiche emeralds. The cover photo shows a 58.83 ct. crystal specimen (left) and a 22.74 ct. cabochon (right), both displaying the material’s signature six-rayed pattern, from the renowned Peñas Blancas emerald region. The host rock, seen in the background, is carbonaceous shale containing veins of calcite, pyrite and minute crystals of low-grade emerald. Photo by Robert Weldon/GIA, courtesy of Jose Guillermo Ortiz and Colombian Emeralds Company, Bogota.

A report on Colombia’s unique trapiche emeralds is the cover feature of the fall 2015 issue of Gems & Gemology (G&G), which also offers an analysis of large synthetic diamonds produced in Russia and a detailed look inside the Letšeng Diamond Mine in Lesotho (the leading source for mega-sized diamonds).
Colombian Trapiche Emeralds: Recent Advances in Understanding Their Formation

Colombia’s trapiche emeralds show a distinct pattern that resembles a wheel with six spokes. They are found only in the black shales of the country’s western emerald zone near the legendary mines of Muzo, Quiopama and Coscuez.

These trapiche emeralds, all from Peñas Blancas, range from 5.09 to 22.74 carats. Photo by Robert Weldon/GIA. Courtesy of Jose Guillermo Ortiz, Colombian Emerald Co.
The researchers, Dr. Isabella Pignatelli, Gaston Giuliani, Daniel Ohnenstetter, Giovanna Agrosì, Sandrine Mathieu, Christophe Morlot and Yannick Branquet, performed spectroscopic and chemical analyses on the samples to determine how they formed within their geological setting. They determined that super-pressurized fluid within the black shale helped grow the emerald seed crystals and provided a unique growth environment for them to form into trapiches.
Large Colorless HPHT-Grown Synthetic Gem Diamonds from New Diamond Technology, Russia

In the past five years, the vast majority of synthetic diamonds appearing in the gem market have been manufactured by the Chemical Vapor Deposition (CVD) process, which has been viewed as more efficient than the older High Pressure, High Temperature (HPHT) method, especially for colorless stones.

A Russian manufacturer, New Diamond Technologies, however, has introduced a line of large HPHT grown colorless synthetics and offered 44 samples to GIA for analysis.

As-grown HPHT diamond single crystals produced using a simple Fe-based solvent with Al as a nitrogen getter. The sample on the far right is the largest, weighing 1.40 ct. Photo courtesy of New Diamond Technology.
GIA researchers Ulrika F.S. D’Haenens-Johansson, Andrey Katrusha, Kyaw Soe Moe, Paul Johnson, and Wuyi Wang analyzed the samples using a combination of spectroscopic and gemological techniques to characterize the quality of the material and determine the means of distinguishing them from natural, treated and alternative laboratory-grown diamonds.

These samples had weights ranging from 0.20 to 5.11 carats, color grades from D to K, and clarity grades from IF to I2. Importantly, 89% were classified as colorless (D-F), demonstrating that HPHT growth methods can be used to routinely achieve these color grades.
Letšeng’s Unique Diamond Proposition

The Letšeng-la-Terae diamond mine in Lesotho is the world’s most consistent source of type IIa diamonds (those with exceptionally low nitrogen content), which account for about one-fourth of its production. The mine claims six of the 20 largest diamonds ever discovered: 478, 493, 527, 550, 601 and 603 carats. The largest of these, the Lesotho Promise, was found in 2006 and sold to London jeweler Laurence Graff for $12.4 million.

This remote village, deep in the Maloti Mountains near the Letšeng mine, is primarily dedicated to agriculture and sheep herding. Villagers also form the workforce for the diamond mine. Basuto ponies, such as the one seen here, are esteemed for their speed and surefootedness in the steep, rocky mountain passes. Photo by Robert Weldon/GIA.
The report by Russell Shor, Robert Weldon, A.J.A. (Bram) Janse, Christopher M. Breeding and Steven B. Shirey, also notes that Letšeng’s diamonds are unusual in that a majority are dodecahedral in form, which are very rare in other sources. Despite its bounty, Letšeng has had a difficult history because its ore grade is extremely low – about 2 carats per 100 tonnes and was not economic until recovery technology and diamond prices improved to allow profitable operation.
Origin Determination of Dolomite-Related White Nephrite through Iterative-Binary Linear Discriminant Analysis

Determining the origin of nephrite jade always has been difficult using standard gemological properties and observations. The authors, Zemin Luo, Mingxing Yang and Andy H. Shen, sampled nephrite jade from eight different dolomite-related deposits in eastern Asia.

This ancient pendant was discovered in the tomb of Marquis Yi, ruler of Zeng State during the Warring States period (ca. 475–221 BC). © Hubei Provincial Museum.
The authors used a new statistical analysis method based on linear discriminant analysis (LDA) and trace-element data from laser ablation−inductively coupled plasma–mass spectrometry (LA-ICP-MS), to achieve significantly improved origin determination (an average of 94.4% accuracy) for these nephrite samples. This technique could be applied to other gemstones to determine their geographic origins.
Lab Notes

This section of G&G features a discussion on unusual graining structure in a very light pink diamond with a uniform color plane intersecting with a cone of strain that fit perfectly into a colorless hole; an HPHT treated yellow diamond whose treatment was discovered by spectroscopic analysis; and an emerald with strong color zoning along the pavilion facets that demonstrates the importance of proper orientation and cutting. Other lab notes include a look at irradiated green-blue CVD synthetic diamonds that are the product of new growth technology; a natural green jadeite carving with areas that had been dyed green; and an examination of three large, natural abalone pearls.

Three unique abalone pearls are shown alongside a typical 12 mm golden South Sea bead-cultured pearl for comparison.
Micro-World

The Micro World section shows a Fancy Intense purplish pink diamond with an intricate geometric pattern of planar cracks and strain-induced bodycolor; an otherwise colorless rough diamond that has an eye-visible bluish-green stain near the surface caused by radiation; blue octahedral crystal inclusions within helidor cabochons that are determined to be gahnite, a rare zinc-rich member of the spinel group; and a trapiche pezzottite reportedly found near the Thai-Myanmar border.

Between crossed polars the diamond shows high-order interference colors consistent with the strain causing the cleavage network along the octahedral planes. Photomicrograph by Jonathan Muyal; field of view 0.62 mm.
Other features in this section include glassy melt inclusions in alluvial Montana sapphires, molybdenite inclusions in colorless topaz, and a lighting technique from gemological microscopy, Modified Rheinberg Illumination, that provides false-color contrast to enhance inclusion scenes. @topic:1


Publish Year: 2013 Title: Perles de Culture de la Mer de Cortez: Les Belles Inconnues [Unknown Beauties: Cultured Pearls from the Cortez Sea] Abstract: The first part of the article gives a historical survey of pearls from the Sea of Cortez (Gulf of California), followed by an account of the actual situation. Black pearls and nacre have been known since pre-Columbian times and were much coveted in Europe after the Spanish conquest. In the 16th century, the coastal city of La Paz became the main commercial center for nacre and pearls. The most famous pearl from this source is “La Peregrina,” a 203.8-grain gem last owned by Elizabeth Taylor, and John Steinbeck’s story “The Pearl” also takes place there.

While nacre production was predominant in the first half of the 19th century, black pearls were very much in fashion in the middle of the century. From 1893 to 1914, José Gourieux was the first to cultivate Pteria mazatlanica black-lipped oysters from La Paz for their nacre. He produced about five million oysters per year, of which 10% contained natural pearls. Although these were only a by-product, they led to a sharp decline in pearl diving. In 1914, the plant farm was destroyed during the Mexican revolution. The appearance of artificial substitutes for nacre, overfishing of the oyster banks, and a mysterious infection of the oyster larvae in 1939 finally led to the prohibition of all pearl diving a year later.

After attempts to renew pearl cultivation in the 1960s and 1970s, which failed largely because of political influences and the commercial success of black Tahitian pearls, three students of the Monterrey Institute of Technology and Superior Studies set up a small farm on the campus at Bacochicampo Bay in Guaymas. Their intent was not the industrial production of pearls but the development of environmentally sound and “oyster-friendly” methods of cultivation, which is why the oysters are implanted only once and harvests are small. The 2011 harvest consisted of 1,783 pearls, or 1.7 kg, as compared to 50 tons of Akoya pearls, 11 tons of South Sea pearls, 12 tons of Tahiti pearls, and 1,800 tons of Chinese freshwater pearls.

The other pearl-producing oyster of those waters, the rainbow-lipped Pteria sternia, yields black pearls with many different overtones. The young oysters are all harvested in the sea. Before the implantation of nuclei, the oysters are X-rayed. Some 3% contain natural pearls, and these oysters are not implanted. The pearls are sold as “natural,” though purists would dispute this description. The oysters with nuclei are cultivated for 18–24 months. The diameter of the cultured pearls ranges from 8–12 mm (3.2–4.8 inches), the thickness of the nacre from 0.8 mm–2 mm (0.3–0.8 inches). The pearls are black and very iridescent and show various strong overtones, including red (“cranberry”). Their luster is somewhat more silky than that of the Tahitian pearls. Unlike most other cultured pearls, they are not treated in any manner, except for rinsing with water. They show a pink to red UV fluorescence, which is characteristic of pearls from the Sea of Cortez.

The future is uncertain, however. The volume of larvae has dropped significantly because of global warming effects, damage to the oyster cages from fishing boats, and the fragility and sensitivity of Pteria sternia.

Abstracted by Rolf Tatje @topic:5


Publish Year: 2004 Title: Spring 2004 G&G Book Reviews Abstract: “Pearl Buying Guide: How to Evaluate, Identify and Select Pearls & Pearl Jewelry”
By Renée Newman, 134 pp., illus., publ. by International Jewelry Publications, Los Angeles, 2004. US$19.95

“Faszination Turmalin”
By Paul Rustemeyer, 309 pp., illus., publ. by Spektrum Akademischer Verlag, Heidelberg, Germany, 2003 (in German). 99.95

“Flux-Enhanced Rubies and Sapphires”
By Ted Themelis, 48 pp., illus., publ. by Gemlab Inc., Bangkok, 2004. US$20.00

“Tesouros de Arte e Devoção [Treasures of Art and Devotion]”
By Artur Goulart de Melo Borges, 336 pp., illus., publ. by Fundação Eugénio de Almeida, Évora, Portugal, 2004 (in Portuguese). 40.00

“Glitter & Greed: The Secret World of the Diamond Carte”
By Janine Roberts, 374 pp., illus., publ. by The Disinformation Co., New York, 2003. US$22.95

“Minerals of Nevada”
By Stephen B. Castor and Gregory C. Ferdock, 560 pp., illus., publ. by the University of Nevada Press, Reno, NV, 2003, US$75.00

To view the full section, download the PDF above. @topic:6


Publish Year: 2019 Title: Chatoyant Quartz/Tourmaline Doublet Abstract: Figure 1. This 4.86 ct cabochon displays unusual yellowish chatoyancy against a predominantly purple bodycolor. Photo by Shunsuke Nagai.

Doublets are assemblages of two different materials, often joined with cement. Historically they were composed of inexpensive materials used to imitate precious stones. Recently new combinations have been reported, such as a beryl/topaz doublet (Winter 2014 GNI, pp. 306–307), synthetic sapphire/synthetic spinel doublets (Winter 2016 Lab Notes, pp. 418–419), and a beryl/glass complex assemblage (Summer 2018 Lab Notes, pp. 206–208).
GIA’s Tokyo laboratory had the chance to examine a unique doublet. The 4.86 ct purplish cabochon, measuring 11.07 × 10.00 × 5.94 mm, appeared to display chatoyancy with a yellowish sheen (figure 1). The hydrostatic specific gravity (SG) and spot refractive index (RI) readings were 2.66 and 1.54, respectively. Assembled features with a cemented plane were easily recognized when viewed from the side, as shown in figure 2. Standard gemological testing, microscopic observation, and infrared spectra revealed that the cabochon segment was a natural amethyst. There were no parallel inclusions that might have caused chatoyancy in this segment. On the other hand, the semitransparent yellowish base had parallel striations and tube-like inclusions throughout (figure 3). Raman spectroscopy identified the base as tourmaline.

Figure 2. Viewed from the side, the assemblage was obvious. Trapped bubbles in the cemented plane can also be seen. Photo by Shunsuke Nagai.

Figure 3. Cavities on the base show the parallel striations and columnar or tube-like inclusions. Photomicrograph by Yusuke Katsurada; field of view 1.88 mm.
Parallel inclusions located near the bottom of a cabochon can create a chatoyant phenomenon (Winter 2017 Lab Notes, pp. 459–460). This assembled item displayed a similar effect due to the flat tourmaline base with parallel structures. When light was reflected through the amethyst by the tourmaline base, the parallel striations and tube-like inclusions in the tourmaline created the band of reflected light that appeared on the cabochon. Transparent amethyst and semitransparent yellow tourmaline are an uncommon combination. This doublet is an example that assemblages are not always aimed to imitate precious stones but can be creative artworks. @topic:3


Publish Year: 2017 Title: Book Review: Jeweler’s Enameling Workshop: Techniques and Projects for Making Enameled Jewelry Abstract: By Pauline Warg, paperback, 160 pp., publ. by Interweave, Fort Collins, Colorado, 2016, $16.99.

Enameling is a form of art that many cultures have practiced for centuries, all around the world. If you happen to be a jeweler, you’ve most likely had some exposure to the process in your career, whether facing a challenging request for repair, using the technique to enhance a design, or simply admiring the delicate, colorful work. If you are a jewelry enthusiast but not a maker, you’ve most likely seen the art form but perhaps not realized the minutia behind the beauty.

Why do craftspeople enamel jewelry, and what exactly is enameling? you may wonder. Pauline Warg’s new book, Jeweler’s Enameling Workshop, will help answer these questions. Flipping through the book, we are regaled with page after page of answers: full-size pictures that show the vibrant colors created with the enameling process. The author’s account in the introduction deepens our understanding of why. Jewelry metals can be very monochromatic, and Ms. Warg writes “I love being able to add color to my work without necessarily using gemstones.”

The title’s reference to “workshop” points to the second question: what is enameling? We think of attending a workshop, where we’ll learn hands-on practice, and also of the jeweler’s workspace, where we get a glimpse of interesting tools and various stages of enameled pieces. Ms. Warg has delivered a 160-page resource detailing the intricate art of fusing glass to metal. The book includes essential information, step-by-step project instructions, links to other well-known authors and books, and a list of resources and supply houses.

The book’s first section, "Enameling Basics," provides a wonderful general introduction to enameling that is both easy to read and informative. It includes enough of the science behind the methods for the reader to understand what is happening, but not so much as to bog down the reader. For those who are inspired to pursue enameling, there are other, more process-intense publications that include the expanded science; that is not this book’s intent.

Another key aspect of the first section is a thorough overview of the tools and setup necessary for enameling. In general, jewelry making is a tool-rich activity, and enameling takes the richness to a whole new level. Having basic jewelry-making tools is not enough to start enameling in your studio, and the author does a good job outlining the difference between the two. Further, she is very thoughtful about listing not only what tools and supplies are needed, but also the skills necessary to complete a project. Instructions on how to use the tools, process photos, and troubleshoot, and reminders of general safety concerns guide readers through the methods to create enameled pieces. Lastly, and most importantly, after reading the first section we are left inspired and ready to get busy in our “workshop.”

The main body of the book, titled "Projects," features a series of 20 enameled jewelry projects with step-by-step instructions. The way the author created connections between terms, similar processes, and sections where expanded explanations can be found is very well thought-out. Not only is it like having an instructor present, but it also helps the reader navigate without having to reread similar instructions in each section.

Here and there throughout the book an entry-level jewelry maker may feel a little lost. A few pages include written descriptions of tools that, while standard in a well-used jeweler’s shop, are not everyday knowledge. Although the book is described as appropriate for someone wholly new to both enameling and jewelry making, this is a tall order for one publication. More than likely the reader will need some prior courses or additional books to understand some of the instructions.

Another area that may leave a beginning enamelist feeling behind is the instruction of loading pieces into the kiln for firing. Balancing a small piece of metal coated with ground glass on top of a metal trivet, carefully placing these on a wire rack, and then successfully balancing the three items on a long-handled firing fork while gently placing them into a 1450°F kiln is a precarious maneuver! While Ms. Warg does outline the method, not including a full-size image of the practice in the extensive photos is an oversight, considering it is such an essential part of the enameling process. The author does, however, carefully outline the different types of kilns, as well as the difference between an enameling, or jeweler’s, kiln and a top-loading ceramicist’s kiln.

The flow of the book from one section to another is well thought-out and easy to follow, transitioning nicely from entry-level enameling to more complex projects. The author very thoroughly covers the volume of information necessary to teach how to enamel, while also taking into account how to make a lovely piece of jewelry.

Jeweler’s Enameling Workshop is a great pick for any beginning to advanced jeweler. Having a copy on your bench will inspire you to get working and to start dreaming about how to add beautiful color to your jewelry designs. @topic:6


Publish Year: 2006 Title: Summer 2006 G&G Book Reviews Abstract: “The Heartless Stone: A Journey through the World of Diamonds, Deceit and Desire”
By Tom Zoellner, 294 pp., publ. by St. Martin’s Press, New York, 2006. US$24.95

“Making the Most of Your Flex-shaft”
By Karen Christians, 96 pp., illus., publ. by MJSA/AJM Press and the Ganoksin Project, Providence, RI, 2006. US$34.95

“Charming: The Magic of Charm Jewelry”
By Deborah Alun-Jones and John Ayton, 112 pp., illus., publ. by Thames & Hudson Inc., New York, 2005. US$19.95

“Bedazzled: 5,000 Years of Jewelry”
By Sabine Albersmeier for The Walters Art Museum, 64 pp., illus., publ. by D. Giles Ltd., London, 2005. US$9.95

“Modernist Jewelry, 1930–1960: The Wearable Art Movement”
By Marbeth Schon, 227 pp., illus., publ. by Schiffer Publishing Ltd., Atglen, PA, 2004. US$69.95

To view the full section, download the PDF above. @topic:6


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

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

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

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


Publish Year: 2015 Title: Near-Colorless Melee-Sized HPHT Synthetic Diamonds Identified in GIA Laboratory Abstract: Figure 1. These six near-colorless round brilliant melee, ranging from 0.01 to 0.005 ct, proved to be HPHT synthetic diamonds. Photo by Nuttapol Kitdee.

              With significant development in diamond treatments and synthesis over the last decade, the trade has serious concerns about treated and/or synthetic material mixed with natural melee-sized stones. The mixing of treated and synthetic diamonds with yellow natural melees was previously reported (Winter 2014 Lab Notes, pp. 293–294; Spring 2015 Lab Notes, pp. 64–65). In order to ensure consumer confidence, it is essential to screen melees so as to distinguish all treated and synthetic goods.

Recently, the Bangkok lab had the opportunity to examine six melee-sized specimens submitted for synthetics and treatment screening. The transparent, near-colorless round brilliants ranged in size from 0.005 to 0.01 ct (figure 1). Microscopic observation revealed no obvious inclusions. Between crossed polarizing filters, very little or no strain was observed. Infrared absorption spectra showed that four of the samples were type IIa diamonds with no detectable defect-related absorption, while the other two were type IIb diamonds accompanied by uncompensated boron showing moderately strong absorption at approximately 2800 cm–1. Photoluminescence spectra obtained at liquid-nitrogen temperature with 514 and 633 nm laser excitations revealed an emission doublet of the negatively charged silicon split-vacancy defect [Si-V]– at 736.6/736.9 nm for five of the samples, while 830 nm laser excitation showed an emission doublet at 883.0/884.7 nm owing to a nickel-related defect for all six samples (figure 2). DiamondView imaging revealed either blue or green fluorescence, together with characteristic growth features of HPHT synthesis, as seen in figure 3. Strong blue phosphorescence was also observed for all six samples. These gemological and spectroscopic features confirmed that the specimens were grown by HPHT synthesis.

Figure 2. Photoluminescence spectra at liquid-nitrogen temperature of a small near-colorless HPHT synthetic diamond. The spectra displayed emission peaks at 736.6 and 736.9 nm related to a [Si-V]– defect (left, 514 nm laser excitation) and at 883.0 and 884.7 nm associated with a Ni-related defect (right, 830 nm laser excitation).

Figure 3. This DiamondView image of one sample (third from the left in figure 1) shows the characteristic growth features of HPHT-grown synthetic diamonds. DiamondView image by Charuwan Khowpong.
To the best of our knowledge, this is the first examination of near-colorless HPHT synthetics of these sizes by a gemological laboratory. Discovery of these HPHT synthetic diamond melee reaffirms the need to screen the huge volume of near-colorless melee currently in the trade. @topic:4


Publish Year: 2009 Title: Gray-To-Blue-To-Violet Hydrogen-Rich Diamonds from the Argyle Mine, Australia Abstract: The Argyle diamond mine is the only known source of type IaB hydrogen- and nitrogen-rich diamonds colored gray to blue to violet. Twenty such diamonds were studied to investigate the relationships between their spectroscopic characteristics and color grades. The unusual color is the result of broad absorption bands centered at ~520–565 nm and 720–730 nm. A pronounced 551 nm band is superposed on the 520–565 nm feature. Spectral deconvolution of this feature suggests that it may be a composite, including H-related absorptions at ~545 and 563 nm and bands at 520–530 and 551 nm. The near- and mid-IR regions exhibit strong absorptions, including those related to H and N, many of which become more intense with increasing color saturation. The PL spectra exhibit peaks associated with nickel-related defects, which may play an important role in the coloration of the more violet diamonds in this group. H-rich gray-to-blue-to-violet diamonds, which are not known to be treated, can be readily separated from similar-hued diamonds that may be HPHT enhanced or synthetic.

	DATA DEPOSITORY

Supplemental Material
	Spring, 2009 @topic:4


Publish Year: 2023 Title: Treated HPHT Laboratory-Grown Diamond with Dramatic Color Zoning Abstract: Figure 1. This 2.20 ct Fancy Deep brownish orange treated HPHT-grown diamond owes its distinctive appearance to multiple defect concentrations created within the various growth sectors. Photo by Diego Sanchez.

Figure 2. The square-shaped cubic {100} growth sector appears pink when viewed through the table (left) and more of a purple color when viewed through the pavilion (right). The surrounding regions appear predominantly yellow due to the presence of single nitrogen. Photomicrographs by Nathan Renfro; fields of view 4.23 mm and 4.50 mm.
Recently, the Carlsbad laboratory examined a 2.20 ct laboratory-grown diamond that received a color grade of Fancy Deep brownish orange (figure 1). Spectroscopic analysis indicated high-pressure, high-temperature (HPHT) growth methods and subsequent irradiation and annealing to create nitrogen vacancy centers. Infrared absorption spectra collected from the entire stone identified it as type Ib with a concentration of ~5 ppm of single isolated nitrogen. The diamond was distinctive because of a pronounced pink square under the table facet within the cubic {100} sector. The other major growth sectors (e.g., {110}, {111}) surrounding the central cubic sector appeared yellow due to single isolated nitrogen. The pink growth sector displayed pronounced reflections when viewed through the pavilion facets and had more of a purple color (figure 2).

Figure 3. Room-temperature Vis-NIR absorption spectra were collected using a reflectance probe to document the absorption differences between the pink central region and the surrounding areas. The red trace shows a pronounced absorption associated with NV– along with Ib (i.e., single nitrogen) absorption. The yellow trace also shows Ib absorption along with a minor contribution of NV0 and small peaks associated with GR1 (741.2 nm) and nickel (883/884 nm). Spectra are offset vertically for clarity.
Visible/near-infrared (Vis-NIR) absorption spectra were collected from the center of the table using a reflectance probe positioned to show pink fluorescence. The probe was then repositioned toward the crown facets that did not show pink fluorescence (figure 3). The spectra from both areas indicated type Ib-related absorption at low wavelengths. Additionally, the pink color region was dominated by the NV– center (zero-phonon line, or ZPL, at 637 nm) and its associated sidebands, while the surrounding yellow regions had minor absorption from NV0 (ZPL at 575 nm). This difference in NV-related absorption shifts the transmission window from pink to yellow.
The uptake of single nitrogen is generally lower in {100} growth sectors than in {111} sectors (R.C. Burns et al., “Growth-sector dependence of optical features in large synthetic diamonds,” Journal of Crystal Growth, Vol. 104, 1990, pp. 257–279). However, the concentration of single nitrogen (necessary to ultimately create NV centers) can be increased within the cubic sector through lower growth temperatures (S. Satoh et al., “Differences in nitrogen concentration and aggregation among (111) and (100) growth sectors of large synthetic diamonds,” Science and Technology of New Diamond, KTK Scientific Publishers/Terra Scientific Publishing Co., Tokyo, 1990, pp. 351–355). It is possible that such growth conditions were used with this diamond in order to incorporate sufficient nitrogen within the cubic sectors, which were subsequently transformed to NV centers with treatment.

Figure 4. PL mapping using 532 nm excitation at liquid nitrogen temperature shows pronounced differences in defect concentrations based on growth sector. The NV– intensity (left, normalized to the diamond Raman line) is highest within {100} and much lower within the other regions. The normalized NV0 defect intensity (right) was detected throughout the diamond but was noticeably higher within {111} sectors.
Within the cubic sector, photoluminescence (PL) mapping showed a significantly higher concentration of NV– compared with the other major growth sectors (e.g., {110} and {111}), while the concentration of NV0 was lower (figure 4). The presence of donors, such as single nitrogen, can often shift the balance between neutral and negative NV centers so that NV– is enhanced in diamonds with single nitrogen (I.A. Dobrinets et al., HPHT-Treated Diamonds: Diamonds Forever, 2013, Springer-Verlag, Berlin). The presence of single nitrogen can be related to an elevated concentration of NV– within the cubic sector; however, in the {111} sectors, NV0 dominates over NV– despite the appreciable concentrations of single nitrogen. This can likely be attributed to the {111} sectors also preferentially incorporating boron. Although boron was not detected within the infrared absorption spectra for this stone, it is often present in HPHT-grown diamond, even at low concentrations. Since boron preferentially incorporates within {111} sectors (U.F.S. D’Haenens-Johansson et al., “Synthesis of diamonds and their identification,” Reviews in Mineralogy and Geochemistry, Vol. 88, No. 1, 2022, pp. 689–753), these acceptors could shift the charge balance within those areas, thus causing the preferential creation of NV0 over NV–.
PL mapping highlighted other pronounced differences between the growth sectors. The GR1 defect (V0) and TR12, an irradiation-related defect with ZPL at 469.9 nm, was highest in {110} and negligible in {100}. The nickel-related doublet at 883/884 nm was extremely high in {111} and negligible in {110} and {100}.
This HPHT-grown diamond is a notable example of growth techniques and treatment engineering producing a combination of defects that is visually interesting. The faceting approach, in which the pink growth sector was positioned under the table facet, served to enhance the dramatic appearance. @topic:4


Publish Year: 2023 Title: Diamondiferous Mantle Eclogite: Diamond Surface Features Reveal a Multistage Geologic History Abstract: Figure 1. Mantle eclogite xenolith (2.8 cm in longest dimension) consisting of clinopyroxene (green) and garnet (red-orange), with a partially exposed octahedral diamond. Photo by Annie Haynes. Gift of Mark Mauthner, GIA Museum no. 37511.
More than 99% of diamonds originally formed in the lithospheric mantle, the cold, rigid mantle that underlies continents, generally <300 km deep (T. Stachel and J.W. Harris, “The origin of cratonic diamonds – Constraints from mineral inclusions,” Ore Geology Reviews, Vol. 34, No. 1-2, 2008, pp. 5–32). In the lithospheric mantle, the two major rock types—and host rocks for diamond—are peridotite (>95 vol.%), composed predominantly of olivine, and eclogite (<5 vol.%), composed of iron-magnesium-calcium garnet and sodium-rich clinopyroxene. Eclogite is a high-pressure and high-temperature metamorphic rock that can form when dense oceanic crust subducts into the mantle beneath continents at convergent margins.
We cannot directly study the deep portion of the earth where diamonds form. Instead, geologists study diamonds themselves, as well as pieces of mantle rock that are transported to the surface as xenoliths by volcanic magmas such as kimberlite or lamproite. The authors have studied one such mantle eclogite xenolith, part of the GIA Museum collection (figure 1). This sample was recovered from a kimberlite in Russia and contained a partially exposed octahedral diamond. The exposed portions of the diamond had visible surface features, including trigons (figure 2).

Figure 2. Partially exposed diamond embedded in an eclogite xenolith, with positive and negative trigons on the octahedral face. A mineral is included within the diamond, visible through the octahedral face. Photomicrograph by Matthew Hardman; field of view 5.74 mm.
Trigons are inferred to be etch features that form after diamond crystallization, through interaction with fluids or melts either in the mantle source region or during transport to the surface (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). Trigons form exclusively on the octahedral faces of diamond and can have several different orientations. Positive trigons are oriented in the same direction as the octahedral face, and negative trigons have opposing orientation (figure 2). Positive trigons are very rare and may relate to interaction with carbon-oxygen-hydrogen-rich fluids at temperatures between ~800° and 1000°C at near-surface pressures (Z. Li et al., “Positively oriented trigons on diamonds from the Snap Lake kimberlite dike, Canada: Implications for fluids and kimberlite cooling rates,” American Mineralogist, Vol. 103, No. 10, 2018, pp. 1634–1648). Trigons with negative orientation are much more common. It has been shown experimentally that increasing water content in melts could be one cause for the change of a trigon from positive to negative (e.g., A.F. Khokhryakov and Y.N. Pal’yanov, “The dissolution forms of diamond crystals in CaCO3 melt at 7 GPa,” Russian Geology and Geophysics, Vol. 41, No. 5, 2000, pp. 682–687). Diamonds with coexisting positive and negative trigons are extremely rare (e.g., Harris et al., 2022) and may indicate that the diamond experienced a complex multistage history related to thermal or fluid changes after its formation.
Using the acquired infrared absorption spectrum, the authors identified the diamond as type IaAB, containing nitrogen in the A- and B-aggregated forms. When the entire xenolith was exposed to ultraviolet light, the diamond fluoresced blue due to N3 defects (three nitrogen atoms surrounding a lattice vacancy), consistent with the presence of nitrogen impurities.
The diamond also contained an unidentified mineral inclusion with visible iridescence (figure 2). Minerals included fully within diamond (which itself is an impermeable time capsule) represent pieces of the mantle source region present at the time of diamond formation. For this sample, the mineral was too deep within the diamond to conclusively identify it nondestructively. However, if the mineral inclusion could be extracted, its chemical composition might be very useful in reconstructing the geologic history of the host diamond, as well as that of the mantle rocks in which the diamond formed. @topic:8


Publish Year: 2023 Title: Natural Type IIa Diamond with Unusual Red Fluorescence Distribution Abstract: Figure 1. This 3.58 ct natural type IIa diamond with H color and SI2 clarity displayed a unique fluorescence pattern when exposed to deep-UV light. Photo by Diego Sanchez.
The Carlsbad laboratory received a natural type IIa diamond with some unusual characteristics. As part of the standard data collection, the diamond type was determined by Fourier-transform infrared (FTIR) spectroscopy and deep-UV fluorescence images collected using the DiamondView instrument. The DiamondView images revealed predominantly red fluorescence on one side of the diamond and blue fluorescence on the other. This 3.58 ct pear modified brilliant diamond had H color and received an SI2 clarity grade due to cavities, chips, and a feather (figure 1).

Figure 2. 514 nm PL spectra collected on the pavilion of opposite sides of the stone. The spectrum plotted in red corresponds with the red-fluorescing region, and the blue spectrum corresponds with the blue-fluorescing region, with Raman lines at 552 nm scaled as equal. Spectra are offset vertically for clarity. PL analysis spots are circled in the deep-UV fluorescence images. Images by Barbara Whalen.
Type IIa diamonds typically display a blue fluorescence pattern under deep UV as a result of “band A” fluorescence or the N3 defect in the stone (U.F.S. D’Haenens-Johansson et al., “Synthesis of diamonds and their identification,” Reviews in Mineralogy and Geochemistry, Vol. 88, No. 1, 2022, pp. 689–753). High amounts of nitrogen vacancy (NV) centers can cause red fluorescence in diamonds; however, this is rare in type IIa stones, as they are defined by nitrogen concentrations low enough to be undetectable by FTIR (Summer 2016 Lab Notes, pp. 189–190). The NV centers can be detected in a negative charge state (NV–, zero-phonon line at 637 nm) or a neutral state (NV0, zero-phonon line at 575 nm). Photoluminescence (PL) testing revealed much higher concentrations of both NV centers in the red-fluorescing region of the stone (figure 2). This distribution could have occurred if traces of isolated nitrogen were concentrated in one growth area of the stone.

Figure 3. False-color 532 nm PL map showing the Raman-normalized peak area of NV0 (left) and NV– (right). The maps were compiled from 47,040 spectra. The pronounced gradient in NV centers across the diamond resulted in the different fluorescence color observations (see figure 2 insets).
PL mapping using 532 nm laser excitation (figure 3) displayed the relative intensities of these defects, demonstrating the wide distribution of the NV centers in opposite sides of the table and crown facets of this diamond. Analysis of this interesting fluorescence feature demonstrated that nitrogen could have been distributed unevenly in a relatively pure type IIa diamond when it initially formed. @topic:4


Publish Year: 2018 Title: Gemological Analysis of Lightbox CVD-Grown “White” Diamonds Abstract: Figure 1. The 0.26 ct near-colorless CVD-grown diamond (left) has an internal inscription showing the Lightbox logo, composed of dual narrow lines. The logo is easily detected with a microscope (center) and clearly visible in the DiamondView image (right), in which the red fluorescence is due to nitrogen-vacancy centers. Also seen in the DiamondView image are subtle striations, additional evidence of the CVD origin. The outer square of the Lightbox logo measures 300 microns on each side. Photos by Robison McMurtry (left) and Sally Eaton-Magaña (center and right).
Lightbox, a De Beers company, has begun selling “white,” pink, and blue CVD laboratory-grown diamonds at a flat rate of $800 per carat. Through a third-party vendor, we recently had the opportunity to examine two such samples (0.24 and 0.26 ct) intended for setting in a pair of earrings. Both were near-colorless with color grades equivalent to G color and cut grades of Excellent and Very Good, respectively.
Both lab-grown diamonds had very few clarity characteristics. The 0.24 ct sample had a pinpoint in a bezel facet, and the 0.26 ct round (figure 1, left) had a feather in a star facet, both with VVS clarity. However, the grade-setting feature for both was the Lightbox logo, internally inscribed underneath the table facet (figure 1, center). As a result of the Lightbox mark, the clarity grade for both was reduced to VS. The laser-inscribed internal feature is reportedly made using technology developed by Opsydia (Gem and Jewellery Export Promotion Council, “De Beers to use Opsydia’s laser tech to inscribe lab-grown diamonds in Lightbox Jewelry,” https://www.gjepc.org/news_detail.php?id=4075). It is composed of dual narrow lines ~2.5 microns wide with a total area of 300 × 300 microns, positioned about 200 microns below the table surface.
Spectroscopic analysis showed both samples had very similar features that were consistent with previously analyzed CVD products from other manufacturers. IR absorption spectroscopy confirmed these samples as type IIa with no detectible single nitrogen at 1344 cm–1. Photoluminescence (PL) spectra showed that both had the 596/597 nm doublet, indicating that they were as-grown and not subjected to post-growth HPHT processing (S. Eaton-Magaña and J.E. Shigley, “Observations on CVD-grown synthetic diamonds: A review,” Fall 2016 G&G, pp. 222–245). Faceted, as-grown near-colorless CVD samples are less common since most manufacturers grow CVD layers quickly, but with a brown color, knowing that they can be HPHT treated to improve color appearance after growth. Approximately 75% of the CVD material in this color range examined by GIA has been HPHT treated after growth (S. Eaton-Magaña, “Summary of CVD lab-grown diamonds seen at the GIA laboratory,” Fall 2018 G&G, pp. 269–270).

Figure 2. This 514 nm PL spectrum collected on the 0.26 ct sample at liquid nitrogen temperature shows strong nitrogen vacancy centers at 575 and 637 nm and the 596/597 nm doublet, evidence of an as-grown CVD sample.
Through crossed polarizers, we observed very low birefringence compared with the majority of CVD-grown diamonds examined. Additionally, both samples showed very strong emission from nitrogen-vacancy centers by PL spectroscopy (figure 2), as well as visible red fluorescence using DiamondView imaging (figure 1, right), but there was no detectable fluorescence with long-wave UV. With careful DiamondView imaging, subtle CVD striations were visible through the table facet. In the DiamondView images, there were no apparent growth interfaces showing multiple growth events, and no apparent seed crystal remnants were observed. Also, PL spectroscopy of both samples showed very weak but detectable silicon-vacancy centers at 736.6/736.9 nm.
The Lightbox CVD lab-grown diamonds, due to their price point and manufacturer, will likely be highly visible in the trade. The pink and blue samples, as evidenced by De Beers’ literature, have an appearance that is unusual among natural-color diamonds and are unlikely to ever be perceived as a natural-color product. However, the colorless Lightbox samples are readily identifiable as CVD-grown diamonds by spectroscopic techniques, DiamondView imaging, and their distinctive internal inscription. @topic:4


Publish Year: 2023 Title: HPHT-Grown Colorless Diamond Displaying Unusual Phosphorescence Effects Abstract: Figure 1. Top: A series of images showing the gradual change (left to right) in the phosphorescence of the 0.71 ct HPHT-grown colorless diamond after removing it from the LWUV source (left image) in increments of 30 seconds for 150 seconds (right image). Bottom: The gradual change in phosphorescence after exposure to a SWUV source (left image) in increments of 30 seconds. The greenish blue and orange emissions decay differently, with the blue fading faster (~90 seconds, fourth image from left) than the orange (~240 seconds, right image). Images by Guy Borenstein.
Phosphorescence longer than 10 seconds in reaction to ultraviolet radiation is regularly observed in colorless to near-colorless and blue-colored diamonds grown by a high-pressure, high-temperature (HPHT) technique. The gemological laboratory of Stuller Inc. recently tested an HPHT-grown colorless (approximately E color grade with a blue-gray overtone) oval brilliant diamond weighing 0.71 ct that showed unusual fluorescence and phosphorescence reactions.
When exposed to a long-wave ultraviolet (LWUV, 365 nm) source for 60 seconds using a standard UV viewing cabinet, the stone emitted a gradually increasing strong orange fluorescence, followed by a long-lasting noticeable phosphorescence (~150 seconds, figure 1, top). The fluorescence and phosphorescence reactions demonstrated a nonuniform color distribution. Similar results were observed using other light sources, including 395 nm UV LED, 405 nm blue laser, a tungsten incandescent flashlight, and a fiber-optic halogen unit.
Given that orange phosphorescence can also be generated by low- and non-UV light sources, further analysis was performed using a series of spectral bandpass filters to identify other wavelengths that stimulate the orange phosphorescence. Testing demonstrated that medium- to strong-intensity light centered at around 430 nm produces the excitation.
Under short-wave ultraviolet (SWUV, 254 nm) radiation using a standard viewing UV cabinet and a De Beers PhosView instrument, the stone displayed a mix of strong greenish blue and medium orange zoned fluorescence and phosphorescence (figure 1, bottom). The colored phosphorescing areas decayed at different rates, with the greenish blue fading faster than the orange (~90 seconds vs. ~240 seconds, with a half-life of about 25 and 35 seconds, respectively).

Figure 2. Deep-UV imaging of the 0.71 ct colorless diamond showing a cuboctahedral-structured luminescence associated with HPHT growth. Image by Guy Borenstein.
Deep-UV (<225 nm) imaging demonstrated a strong greenish blue fluorescence with a clear cuboctahedral structure associated with HPHT growth (figure 2). After removal from the excitation source, the stone displayed a phosphorescence reaction similar to the reaction under SWUV.

Figure 3. The infrared spectrum of the 0.71 ct HPHT-grown diamond revealed it was type IIb with relatively high levels of uncompensated boron (for a colorless diamond) at 4089, 2929, 2800, and 2455 cm–1.
Infrared spectroscopy revealed a type IIb diamond with relatively high levels of electrically uncompensated boron at 4089, 2929, 2800, and 2455 cm–1 (figure 3). Photoluminescence spectroscopy with 532 nm laser excitation at liquid nitrogen temperature (77K) showed no results, except for the diamond’s first- and second-order Raman spectrum peaks, a common tendency in HPHT-grown colorless diamonds (S. Eaton-Magaña et al., “Observations on HPHT-grown synthetic diamonds: A review,” Fall 2017 G&G, pp. 262–284).
The two phosphorescence colors emitted and their relatively long duration are well-known properties of HPHT-grown diamonds (S. Eaton-Magaña and R. Lu, “Phosphorescence in type IIb diamonds,” Diamond and Related Materials, Vol. 20, No. 7, 2011, pp. 983–989; Eaton-Magaña et al., 2017), and a blue-orange luminescence combination in one gem was also previously reported (Eaton-Magaña and Lu., 2011; B. Deljanin et al., “NDT breaking the 10 carat barrier: World record faceted and gem-quality synthetic diamonds investigated,” Contributions to Gemology, Vol. 15, No. 1, 2015) but of weaker intensity. The laboratory-grown diamond’s property of bicolor, decay-varying phosphorescence has been previously reported as well (K. Watanabe et al., “Phosphorescence in high-pressure synthetic diamond,” Diamond and Related Materials, Vol. 6, No. 1, 1997, pp. 99–106; Eaton-Magaña and Lu, 2011; Ulrika F.S. D’Haenens-Johansson et al., “Large colorless HPHT-grown synthetic gem diamonds from New Diamond Technology, Russia,” Fall 2015 G&G, pp. 260–279).
Considering the HPHT growth method, the long-lasting greenish blue phosphorescence produced by exposure to SWUV and deep UV was expected. It was previously suggested to be related to nitrogen-boron donor-acceptor pair recombination (Watanabe et al., 1997). However, the orange phosphorescence demonstrated a new stimulation source. Its combination with the greenish blue phosphorescence and the identified visible-light excitation wavelength reinforces the theory that the recorded orange phosphorescence is of a different donor-acceptor pairing.
Light of 430 nm wavelength can be found in most fluorescent and all incandescent indoor light sources, as well as the desk lamps and color grading cabinets found in gemological laboratories. Therefore, considering the possibility of more diamonds with this property in the market, their phosphorescence produced from visible light makes it challenging to assign a color in the colorless to near-colorless range for these diamonds during grading. Even under standard non- or low-UV output 6500K fluorescent bulbs, the orange luminescence generated by the source becomes noticeable, adding a yellowish overtone to the blue-gray bodycolor and changing its apparent color grade to approximately F to G. Such a change may impair the diamond grader’s ability to accurately assess the stone’s bodycolor. @topic:4


Publish Year: 2023 Title: Grayish Blue CVD Diamond Colored by GR1 and SiV– Abstract: Figure 1. Left: This 1.63 ct grayish blue diamond was identified as a CVD synthetic, with its color caused by both the GR1 and SiV– centers. Photo by Xiaoyu Zhang. Right: Dark cloud-like non-diamond carbon inclusions. Photomicrograph by Meng Li; field of view 0.25 mm.
Silicon is a common impurity in chemical vapor deposition (CVD) laboratory-grown diamond. The silicon-related SiV– center, which has zero-phonon lines at 736.6 and 736.9 nm and is active in absorption and luminescence, is widely considered an identifying feature of CVD diamond. Generally, the SiV– center is detected by photoluminescence spectroscopy and is not observed using absorption spectroscopy for most CVD synthetics due to the low silicon content. The absorption spectra may reveal the presence of the SiV– center in the case of a relatively high silicon content, but rarely in amounts significant enough to affect the color. When the silicon content becomes particularly high, the absorption of SiV– is in sufficient concentration to influence the bodycolor of a diamond. It has been reported that the color of silicon-doped blue CVD diamonds produced by the PDC Company is attributed to strong absorption of the rather intense SiV– center (A. Peretti et al., “New generation of synthetic diamonds reaches the market (Part A): Identification of CVD-grown blue diamonds,” Contributions to Gemology, No. 14, 2013, pp. 3–20).

Figure 2. In the Vis-NIR region, in addition to very strong absorptions at 737 nm (SiV–) and 741 nm (GR1), weak absorptions at 830, 856, and 946 nm (SiV0) were observed.
National Gemstone Testing Center’s (NGTC) Beijing laboratory recently received a 1.63 ct grayish blue princess cut (figure 1, left) for identification. Standard testing identified it as a CVD synthetic diamond. The sample showed an even color distribution. Microscopic investigation revealed abundant non-diamond carbon inclusions in the form of both crystals and clouds, with the clouds distributed along the growth layer (figure 1, right). The visible/near-infrared (Vis-NIR) spectrum (figure 2), recorded at liquid nitrogen temperature, included a strong broad SiV– center defect at 737 nm next to an equally strong GR1 center. The diamond’s grayish blue bodycolor was attributed to both the strong GR1 center and the high intensity of the SiV– center, which produced preferential absorption in the red part of the spectrum. In addition, weak absorptions at 830, 856, and 946 nm (the SiV0 center) were observed, which were also reported in CVD synthetic diamonds with high silicon content (Peretti et al., 2013; Z. Song et al., “Silicon-doped CVD synthetic diamond with photochromic effect,” Journal of Gems and Gemmology, Vol. 18, No. 1, 2016, pp. 1–5).

Figure 3. DiamondView imaging showed green fluorescence with blue dislocations. The diamond also revealed a layered growth structure, indicating a start-stop cycling growth process typical of CVD diamond, as CVD diamond growth takes place layer by layer on the top surface of the growing crystal. Image by Xiaoyu Zhang.

Figure 4. The PL spectrum of the grayish blue CVD synthetic diamond obtained with 473 nm excitation (A) showed that the H3 center (503.2 nm) and radiation-related features included very strong 3H at 503.5 nm and weak 486.3 nm. B: 532 nm excitation revealed the NV centers and silicon-vacancy center that are typically observed in CVD-grown diamonds, along with strong GR1. C: 785 nm excitation showed the H2 center at 986 nm.
Infrared spectroscopy showed features typical for type IIa diamond (i.e., no defect-related absorptions were detected). The diamond was inert to short-wave and long-wave ultraviolet illumination. Under the ultra-short-wave UV radiation of the DiamondView, the sample fluoresced green, with minor areas showing some blue dislocations. It also showed subtle growth striations and two parallel planes fluorescing stronger than the bulk of the crystal (figure 3). The sample did not phosphoresce. Photoluminescence (PL) spectra taken with various laser excitation wavelengths and at liquid nitrogen temperature (figure 4) showed the presence of radiation-related features including very strong 3H at 503.5 nm, strong GR1 at 741 nm, and weak 486.3 nm. The PL spectra also indicated strong nitrogen-vacancy centers at 575 NV0 and 637 NV– nm and multi-nitrogen defects such as H3 and H2, combined with the absence of the unassigned 596/597 nm doublet that is normally seen in as-grown CVD synthetics, suggesting that it had undergone post-growth high-temperature annealing before irradiation.
The PL spectrum with 532 nm laser excitation also exhibited a rather large silicon doublet peak at 736.6/736.9 nm that dwarfs all other PL peaks, including the GR1 in the spectrum. The intensity ratio between the 736.6/736.9 nm PL peak and the diamond Raman peak was about 52. The PL spectrum reaffirmed that the 737 nm absorption peak of the ultraviolet/visible spectrum was the SiV– defect, and the silicon content of this diamond was so high that it produced strong absorption in the red range of visible light and affected the color of the diamond together with the GR1 center. @topic:4


Publish Year: - Title: CVD Diamond Over 34 Carats Examined in GIA’s Hong Kong Laboratory 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 weighed 34.59 ct, measuring 24.94 × 13.95 × 9.39 mm (figure 1), 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 looking through the table facet, a feature sometimes seen in CVD gem diamonds. It tends to appear more prominent 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.

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.
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 incorporated as contamination during diamond growth. There are different opinions on whether this trace contamination should be considered in diamond classification. 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. Emissions at 596/597 and 467.6 nm, which are common in as-grown CVD diamonds, were 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 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. @topic:4


Publish Year: 2021 Title: Rare Mixed Type IaB-IIb Diamond with a Long-Lasting Phosphorescence Abstract: Figure 1. The 0.20 ct diamond’s FTIR spectrum. Insets show the type IaB aggregate nitrogen at 1175 and 1010 cm–1 (top inset) and IIb boron (bottom inset) at 3725 and 2803 cm–1, confirming a mixed-type stone.
Phosphorescence is an optical effect in which electromagnetic radiation absorbed by a substance is released relatively slowly in the form of light. Long-lasting UV phosphorescence of more than 10 seconds’ duration is an extremely rare property in natural diamonds, normally limited to hydrogen-rich type Ia chameleon and type IIb diamonds.
Recently, a natural round brilliant weighing 0.20 ct (E-F color, VS2-SI1 clarity) was submitted to Stuller Inc. by a client for a custom design. During our diamond screening process, using a phosphorescence imaging-based screening device, the diamond was automatically identified as having an HPHT-grown origin, conflicting with the client’s natural origin disclosure. Secondary testing, using a fluorescence spectroscopy-based screening device, identified the diamond as having a natural origin. Under magnification, only a few pinpoints were spotted.
Due to the ambiguous results, the gem was sent to Stuller’s Gem Lab for further analysis. The FTIR spectrum (figure 1) showed a mixed diamond type comprising low levels of aggregated nitrogen (IaB) and boron (IIb), indicating a natural origin. Similar results were given using fluorescence spectroscopy, which identified N3 peaks, associated with natural origin. Photoluminescence spectroscopy, using a 532 nm laser under liquid nitrogen temperature (77 K), provided results supporting the other instruments and confirming the absence of synthetic origin-related peaks.

Figure 2. The 0.20 ct diamond’s phosphorescence, as seen immediately after exposure to UV radiation (left) and after 60 seconds of elapsed time (right). Images by Guy Borenstein.
In order to identify the cause of the false positive results from the first screening device, the diamond was placed in a SWUV cabinet to analyze its phosphorescence effect. Once excited, the stone emitted a strong bluish green phosphorescence for about 120 seconds (figure 2).
The emitted color and the unusually long duration of the effect are typically associated with HPHT-grown diamonds. Consequently, these properties triggered the false positive results in the phosphorescence imaging-based screening device. In this case, the rare combination of natural diamond types, which includes a boron component, was probably the reason for the unusual phosphorescence.
This case demonstrates the complexity of diamond origin identification and the need for multiple diamond screening devices, each with a different screening technology, to cover all possibilities and ensure a 100% correct identification. @topic:4


Publish Year: 2017 Title: HPHT Synthetic Diamond Melee Without Si or Ni Defects Abstract: Figure 1. These four near-colorless round brilliant melee were identified as HPHT synthetic diamonds lacking the typical Si- and Ni-related defects. Photo by Nuttapol Kitdee.

	Near-colorless synthetic diamond melee grown using the high-pressure, high-temperature (HPHT) method have created significant concern in the industry, and various screening methods have been developed to take into account their most reliable distinguishing features. In general, the specimens described in previous Lab Notes (e.g. Summer 2015, pp. 183–184) were very small round faceted goods ranging between 0.005 and 0.01 ct.

	Recently GIA’s Bangkok laboratory received four loose near-colorless round brilliants for quality assurance service (figure 1). They weighed between 0.07 and 0.09 ct, slightly more than previously submitted melee. All were identified as type IIb HPHT-grown material using Fourier-transform infrared (FTIR) spectroscopy. Their most interesting feature was the absence of silicon- or nickel-related emission peaks when analyzed at liquid nitrogen temperature by photoluminescence (PL) spectroscopy (figure 2). The spectra typically observed in HPHT synthetic diamonds show an emission doublet related to the negatively charged silicon split-vacancy defect SiVˉ at 736.6/736.9 nm and an associated Ni-related defect at 883.0/884.7 nm.

	Figure 2. The PL spectra features observed at liquid nitrogen temperature lacked the 736.6/736.9 nm emission doublet related to the SiV– defect (left, 514 laser excitation) and the Ni-related defect doublet at 883/884 nm (right, 830 nm laser excitation).

	The growth patterns observed in the DiamondView were an identifying feature that did remain the same. The characteristic angular growth patterns and blue-green fluorescence, together with an associated green phosphorescence, still provide important evidence that aid in the separation of natural and synthetic diamonds (figure 3). Examination with a gemological microscope revealed metallic and rod-like inclusions (figure 4) that also assisted in identifying these melee as synthetic diamonds.

	Figure 3. These DiamondView fluorescence and phosphorescence images of a 0.081 ct sample show growth patterns characteristic of HPHT synthetic diamond. Image by Charuwong Khowpong.

	Figure 4. Darkfield illumination reveals rod-like inclusions in a 0.087 ct HPHT-grown melee diamond. Photomicrograph by Charuwan Khowpong and Ungkhana Atikarnsakul.

	The study of these four melee-size HPHT synthetic diamonds revealed atypical PL spectra. However, other means of identification (inclusions, growth patterns as seen via the DiamondView, and their phosphorescence reactions) still played an important role in their identification. It is interesting to note that HPHT synthetic melee diamonds being submitted to GIA for identification are getting larger, indicating the continuous improvement of synthetic technology. @topic:4


Publish Year: 2022 Title: 10 ct HPHT-Treated CVD Laboratory-Grown Diamond Abstract: Figure 1. This 10.04 ct G-color CVD-grown diamond proved to have been HPHT treated. Photo by Annie Haynes.
Recent years have seen several size milestones for faceted diamonds grown by chemical vapor deposition (CVD). In all the published reports that commented on treatment, these record-size CVD diamonds were indicated to be as-grown and with no indications of post-growth treatment (Winter 2016 Lab Notes, pp. 414–416; “IGI Hong Kong certifies largest CVD grown diamond to date,” 2020, https://www.igi.org/gemblog/igi-hong-kong-certifies-largest-cvd-grown-diamond-to-date/; Spring 2022 Lab Notes, pp. 54–56). For other recent milestone CVD diamonds reported within the trade, we could not confirm whether they were as-grown or treated. At the time of publication, the current benchmark is a 30.18 ct H-color diamond reportedly grown by Ethereal Green Diamond (Rapaport News, June 12, 2022).

Figure 2. The green and blue fluorescence colors in this DiamondView image of the 10.04 ct CVD-grown diamond confirm its post-growth treatment. Image by Taryn Linzmeyer.
Against this backdrop, a notable 10.04 ct CVD-grown diamond (figure 1) was recently submitted to the Carlsbad laboratory for a laboratory-grown diamond report. This emerald-cut stone with G color and VS2 clarity had several growth remnants, including a cloud of dark non-diamond carbon. As with all laboratory-grown diamonds, it underwent extensive testing including spectroscopy to verify its CVD origin. IR absorption spectroscopy identified it as type IIb with an uncompensated boron concentration of ~2 ppb. Spectral features such as the lack of a 468 nm peak in photoluminescence along with the coloration in the DiamondView fluorescence imaging (figure 2) confirmed it had undergone post-growth treatment (W. Wang et al., “CVD synthetic diamonds from Gemesis Corp.,” Summer 2012 G&G, pp. 80–97).
Many CVD-grown diamonds are subjected to high-pressure, high-temperature (HPHT) treatment after growth to remove a brownish appearance caused by extended defects (such as vacancy-related complexes). The brown color often correlates with a faster CVD growth rate, which the manufacturer uses knowing the color can be reduced by treatment afterward. It appears that when manufacturers create a CVD diamond of record-setting size, the growth is performed so slowly that subsequent HPHT treatment is not required for a colorless to near-colorless grade.
While some 80% of colorless to near-colorless CVD-grown diamonds have been subjected to post-growth treatment to reduce their brownish coloration (S. Eaton-Magaña et al., “Laboratory-grown diamond: A gemological laboratory perspective,” Journal of Gems & Gemmology, Vol. 23, No. 6, 2021, pp. 25–39), this treatment is not often applied to larger stones. Therefore, evidence of HPHT treatment in a CVD-grown diamond larger than 10 carats is noteworthy. These products will likely become more commonplace in the future. @topic:4


Publish Year: 2022 Title: Diamonds from Guyana, Ekanite from Sri Lanka, a New Amber Source in Vietnam, and More... Abstract: Welcome to the Summer 2022 issue of Gems & Gemology! This installment is packed with interesting new content, including five feature articles ranging from reports on new and lesser-known gem sources to a study of the emeralds once embedded in the crown of Napoleon III.
“…an overview of diamond production and mining practices in Guyana, along with findings on color…”
In our lead article, Roy Bassoo and Kenneth Befus explore diamonds and diamond mining in Guyana. Drawing on their own observations of diamonds from various alluvial deposits, coupled with government reports, datasets, and historical accounts, the authors provide an overview of diamond production and mining practices in Guyana, along with findings on color, morphology, nitrogen content, and luminescence.
Our second article investigates the uneven shapes and surface features of ekanite from Sri Lanka. Lutz Nasdala and his team analyze ekanite fragments and ekanite-containing specimens of rock discovered near Ampegama, comparing the samples to those from other Sri Lankan sources to identify the processes that led to the distinctive shape and surface features.
As part of an ongoing effort to research gemstones of historical significance, Stefanos Karampelas and coauthors present their analysis of 45 “emeralds” formerly set in the coronation crown of Napoleon III. Using nondestructive mobile spectroscopic and gemological means at Mines Paris - PSL, they verified that 41 of these 45 gems were emeralds, likely of Colombian provenance, while the remaining four were glass containing iron and/or copper.
Next, a team led by Le Ngoc Nang examines the gemological properties and commercial potential of a newly discovered amber source on Phu Quoc island in Vietnam. They conclude that based on the high quality of the amber and the wide distribution of the host rock on the island, Vietnam’s only known amber locality may have a promising future in the market.
In our final article, Dariusz Malczewski and colleagues present their study on natural radioactivity in nephrite. After examining 11 serpentinite-related nephrite samples from Poland, Russia, Canada, and New Zealand, the authors determined that there is no radiological risk to handling nephrite and that the levels of the radioactive isotopes studied are very low.
Our regular columns deliver interesting finds from around the world. Highlights from the Lab Notes, section include a very rare large bright orange benitoite, the famed De Beers Cullinan Blue diamond, and pearls embedded with RFID devices. In Micro-World, the inner beauty of gems comes alive with an impressive blue apatite inclusion in garnet, eye-visible etch channels in a natural diamond, and a rock fragment exhibiting a very realistic eye pattern. Gem News International keeps you up to date with the latest developments, including unusual chatoyancy in omphacite fei cui jade, a company with a mission to support women in the gem trade, testing of color instability in yellow sapphire, and a museum exhibit celebrating a major tourmaline discovery in Maine. Colored Stones Unearthed returns to cover inclusions in gems, explaining how they form, how they are studied, and what they mean for gemologists and geoscientists.
Finally, we invite you to join the Gems & Gemology Facebook group at www.facebook.com/groups/giagemsgemology. Since its launch in February 2020, our growing community has surpassed 25,000 members. Thank you for your continued support and interest in G&G! @topic:2


Publish Year: 2022 Title: Acicular Troughs Coincident with Green Stains on Rough Diamond Surface Abstract: Figure 1. A ~0.12 ct green-skinned diamond from Guyana. Photo by Roy Bassoo.
The author acquired an alluvial rough diamond from Guyana showing unique surficial features that do not appear to have been documented elsewhere. The specimen was a twinned crystal consisting of two intergrown octahedral crystals, ~0.12 ct in weight, with numerous flat-bottomed hexagonal etch features and trigons and a nearly pervasive green skin (figure 1). Most interesting were fine, linear, and randomly oriented features on the diamond surface that were spatially associated with the green stains (figure 2). Radiation stains are known to cause localized expansion in diamond (L. Nasdala et al., “Radio-coloration of diamond: A spectroscopic study,” Contributions to Mineralogy and Petrology, Vol. 165, 2013, pp. 843–861; S.C. Eaton-Magaña and K.S. Moe, “Temperature effects on radiation stains in natural diamonds,” Diamond and Related Materials, Vol. 64, 2016, pp. 130–142). These features also cross-cut trigons, implying that they post-date the diamond’s growth in the earth’s mantle and its surface dissolution within the kimberlite magma (figure 3). These features may be the result of localized dissolution caused by proximal acicular, radioactive, and as yet unknown minerals, leaving behind a cast impression. Green color in diamond can be produced by natural irradiation of the crystal lattice by exposure to radiation from proximal and adjacent radioactive grains (e.g., zircon, monzonite, uraninite, and K-feldspar) or salts dissolved in percolating fluids surrounding the diamond (C.M. Breeding et al., “Natural-color green diamonds: A beautiful conundrum,” Spring 2018 G&G, pp. 2–27). Gamma, alpha, or beta radiation emanating from these sources are thought to cause collections of defects and impurities within the diamond. Gamma and beta radiation have low energies and long penetration depths producing green bodycolors. Due to its high energy, alpha radiation has the shortest penetration depth and only within the first 25 μm of the diamond surface, creating green skins, stains, and spots.

Figure 2. Left: A magnified view of green radiation stains on an unpolished diamond surface in transmitted light. Right: An image of the same surface in reflected light with the radiation staining (outlined in red) and preserved acicular troughs. Photomicrographs by Roy Bassoo; field of view 0.5 mm.

Figure 3. A further magnified view of the green radiation stains on an unpolished diamond surface in transmitted light (left) and an image of the same surface in reflected light with the radiation staining outlined in red and preserved acicular troughs which cross-cut a flat-bottomed trigon (right). Photomicrographs by Roy Bassoo; field of view 0.25 mm.
Although unusual, radiation-related surface features have been previously documented (e.g., Spring 2021 G&G Micro-World, pp. 66–67). The ones seen in this diamond from Guyana appear to be unique, however. It is quite likely that these features are pervasive in placer diamonds but have not been studied in detail. @topic:10


Publish Year: 2005 Title: A Review of the Political and Economic Forces Shaping Today’s Diamond Industry Abstract: During the past 15 years, political and economic forces have converged to radically transform the structure of the diamond industry worldwide. This article examines how upheavals in the former Soviet Union and several African nations—as well as the arrival of new sources such as Australia and Canada—led to the restructuring of the rough diamond market. This in turn created new competitive pressure at the wholesale and retail levels, including the movement to establish new diamond cuts and diamonds as branded items. At the same time, technological advances have enabled the faster, more efficient manufacturing of rough diamonds, created new treatments, and fostered the introduction of economically viable gem-quality synthetics. While demand for diamond jewelry remains strong in the U.S., which accounts for nearly 50% of world consumption, new markets such as India and China are likely to spearhead continued growth. In addition, new social and governmental initiatives have affected how the entire industry conducts business. @topic:12


Publish Year: 2021 Title: Prominent Growth Planes Observed in HPHT-Processed CVD Laboratory-Grown Diamonds Abstract: Figure 1. Face-up images of four CVD laboratory-grown diamonds with an eye-visible growth plane. These four diamonds range from 1.81 to 2.51 ct. Photos by Johnny Leung and Tony Leung.
The laboratory-grown diamond industry is ever evolving and improving. With state-of-the-art growth and treatment technology, high-quality CVD diamonds, in terms of clarity and color, are now commonly seen on the consumer market. Laboratory-grown diamonds are occasionally submitted for natural diamond grading services, and recently GIA’s Hong Kong laboratory received a total of 43 undisclosed CVD-grown diamonds treated by high pressure and high temperature (HPHT), ranging from 0.70 to 2.63 ct in weight, from the same client. Laboratory-Grown Diamond Reports were issued for these synthetics, which received E–I color grades and VVS2–I2 clarity grades.
Four samples had a very eye-catching feature—a dark circle or ring at the center when viewed face-up without magnification. The ring appeared to be a thick grayish layer at the culet when viewed from the pavilion (figure 1). As the extraordinary feature looked shiny and resembled the separation plane often observed in assembled stones, questions about the true identity of these samples were raised.
Microscopic examination of these four samples revealed some interesting findings. There was a textured plane almost parallel to the table facet, each with a different appearance (figure 2): fine clouds all the way across; ripple-like waves with some “holes” (colorless areas); a mixture of both; and a ripple-like plane that was not visible all the way around.

Figure 2. Visible planes with different textures: fine clouds (top left, field of view 3.83 mm) and wave ripples (top right, field of view approximately 3 mm). Colorless “holes” observed in a ripple-like plane under the microscope (bottom left, field of view 3.83 mm) and in immersion (bottom right). The blue color in the top left photo is due to a different white balance to emphasize the texture. Images by Billie Pui Lai Law (top left, top right, and bottom left) and Johnny Leung (bottom right).
An additional 26 samples had visible grayish/brownish planes either at the pavilion, which were much less prominent, or at the pavilion viewing through the table. Eight of these additional samples had a plane at an angle to the table facet. The plane appeared as a line with no color difference when immersed in water and viewed in a parallel direction to the growth plane. All 43 samples generally showed a banded and cross-hatched strain pattern when viewed with crossed polarizers (figure 3).

Figure 3. A banded strain pattern seen across the visible plane. Photo by Billie Pui Lai Law; field of view 11.45 mm.
Spectroscopic analysis of the 43 samples yielded very similar results. They were either type IIa or type IIb and had a very strong silicon vacancy doublet peak (736.5 and 736.9 nm) in their photoluminescence spectra, typical of CVD-grown diamonds. PL spectra were also collected at the table and at the pavilion somewhere between the growth plane and the culet for the samples with a very prominent growth plane, but the data did not show any critical differences. The most diagnostic test was DiamondView imaging, as all 43 displayed very distinct growth layers (figure 4). It also revealed the HPHT treatment history that the CVD diamonds had experienced.

Figure 4. DiamondView imaging provided evidence of CVD growth. Images by Billie Pui Lai Law.
The uniformity of the growth layers observed in DiamondView imaging and under crossed polarizers, together with the immersion test, showed no evidence of assembly and therefore excluded the possibility of a doublet. The color making the growth plane visible is believed to come from the non-diamond carbon deposited between two growths. It could not be removed by the post-growth HPHT treatment. @topic:4


Publish Year: 2020 Title: Yellow and Orange Diamonds, New Identification Techniques, and the Chronicles of Chivor Abstract: Welcome to the Summer Gems & Gemology! This issue is packed with informative contents, including the characteristics of yellow and orange diamonds, new gem identification techniques, and the colorful history of the Chivor emerald mine.
“In the world fancy-color diamonds, yellow diamonds are by far the most common while those with an unmodified orange hue are among the rarest.”
In the world of fancy-color diamonds, yellow diamonds are by far the most common while those with an unmodified orange hue are among the very rarest (kudos to Robert Weldon for capturing them on the cover). Both yellow and orange diamonds owe their color to nitrogen-related defects. In the lead article, a GIA team led by Christopher M. Breeding and Sally Eaton-Magaña presents the last in their series documenting the gemological and spectroscopic properties of fancy-color diamonds.
Next, Colin McGuinness and colleagues present a luminescence imaging technique developed by De Beers Group Technology that can quickly and easily distinguish colorless and near-colorless natural diamond from laboratory-grown diamond. One marker can identify more than 99% of natural type Ia and type IIa diamond. A pair of newly developed instruments expand on the technology of the DiamondView instrument introduced by De Beers a quarter of a century ago.
In the third article, Karl Schmetzer and coauthors conclude a sweeping two-part series chronicling the Chivor emerald mine in Colombia. This article examines events from 1924 to 1970, when the mine was principally owned by an American firm. While the early era was marked by stock market speculation and scandal, there were also highly productive periods at the fabled mine.
Optical brightening agents for pearls, which are separate from bleaching and maeshori treatments, are the topic of the fourth article. A team of GIA researchers led by Chunhui Zhou provides a fluorescence spectroscopy technique for confidently separating optically brightened pearls from non-brightened pearls.
In the final article, a team of researchers led by Kong Gao of NGTC in China provide a means of discriminating the geographic origin of dolomite-related nephrite from the four most important sources worldwide. This determination relies on hydrogen and oxygen stable isotope ratios. Isotope analysis is an emerging method in gemological research.
As always, our regular columns offer an illuminating array of insights. Highlights of the Lab Notes section include an exceptional purple sapphire from Montana, a vivid blue hemimorphite cabochon resembling Paraíba tourmaline, and interesting observations on an irradiated blue diamond and a rough diamond crystal with irradiation staining. Micro-World reveals rare and breathtaking observations from the inner landscapes of gemstones, including what is believed to be the first reported inclusion of fluorophlogopite in spinel (or any other gem material). In Gem News International, you’ll find a characterization of purplish pink diaspore reportedly from a new deposit in Afghanistan, a look at the cutting and identification of the world’s largest faceted kunzite, a study of petrified woods from the Russian Far East, and much more.
On a final note, the G&G Facebook group (www.facebook.com/groups/giagemsgemology) is now more than 10,000 members strong. We thank you for your participation and your continued interest in the journal. @topic:10