Title: International Diamond School Abstract: View Gallery

	International Diamond School
In late January 2015, nearly 100 scientists gathered in the northern Italian town of Brixen to attend the Second International Diamond School (IDS). The program, titled “The Nature of Diamonds and Their Use in Earth’s Study,” was designed so that attendees from varied educational and professional levels could learn from leaders in the field of natural diamond research.

The school successfully blended student and professional perspectives, as well as the cross-disciplinary nature of the participants and speakers. Over four days, IDS attendees from a wide range of backgrounds—including experimental researchers, petrologists, mineralogists, crystallographers, isotope geochemists, and diamond industry experts—were treated to a wide scope of lectures and workshops. Presentations provided insight into diamond exploration, advanced research-level analysis, diamond morphology, inclusion chemistry, and geologic occurrences.

George H. Read (Shore Gold Inc., Vancouver) presented a recent history of diamond exploration, culminating with his company’s new Canadian diamond mine: Star-Orion in Saskatchewan, a $2.5 billion project. He provided context on production history, sources, and trading centers. He outlined future diamond mining projects in Botswana, Canada, Lesotho, and India, concluding that the small number of viable projects might signify a shortfall in rough supply. The complexity and financial risks involved with bringing new diamond mines online was made evident.

Bruce Kjarsgaard (Geological Survey of Canada, Ottawa) reviewed kimberlite eruptive models based on 1970s and 1980s research in South Africa. He explained the revision of these models after new kimberlite discoveries in the 2000s in Canada’s Slave craton. He defined kimberlite as a strongly homogenized and “mixed-up” hybrid rock, representing a blend of crystallization out of the magma with country rock, that is often highly variable from place to place. In a second presentation Kjarsgaard examined the major techniques used for exploration for diamondiferous kimberlites, focusing on the Canadian experience and its applicability to glaciated shield areas such as Canada, Russia, the northern United States, and Finland. These techniques have been remarkably successful, partly because of the solid scientific research behind them.

Jeff Harris (University of Glasgow, UK) reviewed the characteristics of lithospheric diamonds based on his experience as a De Beers research director and his access to an unparalleled proportion of run-of-mine diamonds. He showed how different pipes produce distinct diamond size ranges and morphologies. He covered the age relationships between inclusions and host diamond, inclusion chemistry, formation pressures and temperatures, fluid inclusion chemistry, and the abundance of different carbon and nitrogen isotopes in diamond.

Michael Walter (University of Bristol, UK) discussed the super-deep carbon geodynamics of Earth’s mantle along with information provided by analysis of lower-mantle fluids found as inclusions in “superdeep” (sublithospheric) diamonds from Brazil’s Juina field. He explained how new thinking over the past five to six years has provided a model for diamond formation by subduction of carbonate-bearing hydrated oceanic crust in the transition zone of the mantle at depths of 440 to 600 km.

Paolo Nimis (University of Padua, Italy) discussed thermobarometry, a technique that uses mineral phase diagrams to discover the original formation conditions (pressure, temperature, and therefore depth) of rocks in the mantle. He also related the possibility of applying similar techniques to inclusions in diamonds to help determine their formation conditions. His talk explored the accuracy and precision of the different thermobarometers and where future improvements are likely to occur.

Ross Angel (University of Padua) discussed elastic barometry for inclusions in diamonds. This new field uses Raman shift or X-ray diffraction (lattice distortion) to measure decompression effects on the surrounding diamond crystal caused by inclusions formed at high pressure to estimate pressure of diamond formation.

Fabrizio Nestola (University of Padua) explained the advanced X-ray diffraction methods used in their laboratory, which permit very rapid crystal orientation and data collection. This work has shown that some olivine inclusions cannot be syngenetic, as they share no preferred orientation with the host diamond.

Graham Pearson (University of Alberta, Canada) overviewed the petrology and geochemistry of cratonic mantle roots. He explained the effects of melt depletion (removal of clinopyroxene and orthopyroxene) to produce very magnesium-rich melts in the sub-continental mantle, which removes rhenium (Re) to “freeze in” the osmium (Os) isotopic system to allow radiometric dating. This gives very different mean Re/Os model ages for “on-craton” (2.5 billion years) and “off-craton” (2.0 billion) mantle xenoliths (potential diamond host rocks) for the Kaapvaal craton, which underlies southern Africa.

Steven Shirey (Carnegie Institution of Washington) reviewed the topic of age-dating diamonds, beginning with work in the 1980s using rare-earth element ratios in silicate mineral inclusions within the diamonds. He covered rhenium/osmium dating techniques devised in the late 1990s and perfected in the 2000s, finishing with recent Re/Os dating work on zoned diamonds from Yakutia, which showed two-billion-year-old cores surrounded by younger rims of one billion years.

Oded Navon (Hebrew University of Jerusalem) presented on silicic and low-magnesium carbonatitic fluids in fibrous diamonds and their relationship to fluids in gem-quality diamonds. He explained how new work on inclusions along the twin planes of otherwise gem-quality diamonds—macles—revealed fluids of very similar compositions. One can generalize from previous studies of fibrous diamond that most diamonds form under similar growth conditions most of the time.

Thomas Deining (WITec Instruments Corp., Ulm, Germany) introduced WITec’s confocal Raman spectrometer system and described its ability to map three-dimensional fields of features at very high resolution. This instrument is ideally suited to looking into diamond, and his talk set the stage for the Raman workshops the following day.

Maya Kopylova (University of British Columbia) discussed fluid inclusions and volatiles in monocrystalline, octahedral diamonds, with a focus on nitrogen (N2) and carbon dioxide (CO2). She related this new work to previous studies on fibrous diamonds, showing it has wider relevance than previously thought.

Wuyi Wang (GIA, New York) covered diamond treatment and synthesis. He introduced the various causes of color in natural diamonds and explained how combinations of irradiation and high-pressure, high-temperature (HPHT) treatment might alter or remove color. He also reviewed improvements in synthetic diamond size and quality due to advances in HPHT and chemical vapor deposition (CVD) synthesis technology.

Frank Brenker (Goethe University, Frankfurt) outlined the latest findings on ultra-high pressure mineral phases in diamonds. Much of this work is nanostructural in nature and requires removing exceptionally thin wafers of diamond by focused ion beam lithography, a technique borrowed from the electronics industry. Brenker dealt specifically with the idea that some of the inclusion minerals thought to have grown in the lower mantle (e.g., Mg perovskite and ferropericlase) might actually have formed at the shallower depths of the mantle transition zone or even the upper mantle.

Dan Frost (University of Bayreuth, Germany) presented on the experimental petrology of the mantle, using state-of-the-art multi-anvil presses capable of achieving pressures of 250,000 bar at 1,800°C. This work demonstrates the possibility that at certain temperatures and pressures, a system may exist where carbon dioxide (CO2) and methane (CH4) produce carbon (C) plus water (H2O). He presented this as a new model for diamond formation in the deep mantle.

Pierre Cartigny (Institut de Physique du Globe de Paris) showed how carbon and nitrogen isotopes are used to characterize the fluid sources and fractionations that can occur with diamond growth. One of his long-standing conclusions is that even though subduction of C and N can occur and is thought to be a major process for introducing fluids into the mantle, the signatures of subduction are not as clear as one would expect. The possible isotopic changes that can occur between the diamond and its host fluid during diamond growth need much further study.

Andy Davy (Rio Tinto Plc., Bristol, UK) drew upon his experience as a consulting geologist to discuss the role of engineers and natural diamond scientists in evaluating diamond deposits. His talk covered the exploration and evaluation of prospective deposits, improvements in recovery methods to prevent diamond breakage, and assessing the performance of deposits through time. He left the audience with a realistic picture of the complications in establishing diamond grade, price, and hence the viability of any given diamond project. He further showed how exceedingly rare good diamond-producing kimberlites are.

The school was a fantastic opportunity for attendees to learn about diamond exploration, advanced research-level analysis, diamond morphology, inclusion chemistry, and geologic occurrences in a way that will inspire their future studies and career choices. GIA’s contribution directly benefited these up-and-coming research scientists by reducing the attendance fees for the conference, permitting many students to attend who otherwise would have been unable to do so.

IDS was organized by Fabrizio Nestola, Graham Pearson, and Steven Shirey, under the auspices of the Diamonds and Mantle Geodynamics of Carbon (DMGC) consortium, part of the Deep Carbon Observatory (DCO). The school was sponsored by GIA, the DCO, the Italian Society of Mineralogy and Petrology (SIMP), and the University of Padua. The IDS website is at www.indimedea.eu/diamond_school_2015.htm. Source: GIA @topic:7


Title: Unusual Dumbbell-Like Inclusion in Diamond Abstract: Figure 4. This 0.40 ct round brilliant diamond displayed a large, unusually shaped inclusion. Photo by Aurélien Delaunay.

              The French Gemmological Laboratory (LFG) in Paris had the opportunity to grade a 0.40 ct near-colorless round brilliant diamond with a large, unusual inclusion (figure 4). Initial inspection under the loupe showed an unusual internal feature consisting of a thin middle “bar” and two broader appendices (figure 5). Viewed under certain angles, it appeared almost metallic. This feature, which lowered the clarity grade to SI2, was reminiscent of the metallic dumbbell inclusions observed in HPHT synthetic diamonds.

	Figure 5. At first inspection, this dumbbell shape was reminiscent of the metallic flux inclusions seen in HPHT synthetic diamond. Photomicrograph by Aurélien Delaunay; magnified 120×.
DiamondView luminescence images demonstrated that the inclusion was crystallographically oriented, parallel to the edge between two octahedral faces (figure 6). Dumbbell inclusions in HPHT synthetics have a clear crystallographic orientation, often along an octahedral edge as well.

	Figure 6. DiamondView luminescence images demonstrated the diamond’s natural origin, as only traces of octahedral growth were found. The inclusion is crystallographically oriented, parallel to the edge between two octahedral faces, as highlighted by the slightly more inert elongated rectangle beside it. Photomicrograph by Aurélien Delaunay, magnified approximately 60×.
But the stone fluoresced weak blue under long-wave UV radiation and was inert in shortwave UV, a classic luminescence behavior for natural diamond and unknown in synthetic specimens. Furthermore, the infrared absorption spectrum was typical of a natural type IaAB diamond with minor hydrogen. This proved the natural origin of both the stone and its inclusion. With magnification, the inclusion appeared colorless and transparent rather than metallic and opaque, though with a high optical relief. Its morphology was not cuboctahedral—as with inclusions in synthetic diamond—but rounded octahedral. The exact nature of the crystal remains unknown, as we could not obtain a Raman spectrum due to its intense luminescence, but colorless inclusions in diamonds are often forsterite. Source: GIA @topic:4


Title: Very Large Rough Diamond Abstract: This 1,138 ct single-crystal natural diamond (62.51 × 47.61 × 45.56 mm) is the largest ever examined by GIA. Photo by Joshua Balduf.

		Throughout history, the discovery of very large diamond rough has been a rare occurrence. Not only is it unlikely to survive the journey from deep in the earth to the surface, but modern extraction methods, including the use of crushers to break large rock, can reduce such specimens to smaller pieces.

			Therefore, the recent examination of a 1,138 ct rough diamond (62.51 × 47.61 × 45.56 mm; pictured above) provided a unique opportunity to document the largest single-crystal natural diamond ever examined by GIA. While it is possible there have been larger unreported specimens, a search of public sources (e.g., I. Balfour, Famous Diamonds, 5th ed., Antique Collectors Club, 2008) suggests this could be the second-largest rough diamond in history—between the 3,106 ct Cullinan and the 995 ct Excelsior, both of gem quality.

			Known to be from the Democratic Republic of the Congo, this stone displayed Raman spectroscopic features characteristic of diamond. The sheer size presented a challenge with IR absorption spectroscopy analysis, as it was too large for the regular sample chamber, beam condenser, or DRIFT units. Instead, we used an infrared microscope with reflective mode and obtained a high-quality absorption spectrum. The rough was identified as a natural type IaA diamond with very high nitrogen concentration. We also detected a weak hydrogen-related absorption peak at 3107 cm–1, a common feature in natural diamond. Also recorded were strong absorption bands at approximately 3300, 2920, 1700, and 1550 cm–1, attributed to micron and sub-micron inclusions. Photoluminescence spectra were recorded at liquid-nitrogen temperature with various laser excitations. The main emission features were broad bands at 700 and 787 nm. The crystal also displayed a very weak blue fluorescence under long- and short-wave ultraviolet radiation, another typical feature.

			The irregular morphology of the 1,138 ct rough was quite interesting, as diamond usually occurs in octahedral or dodecahedral forms. But such a morphology is less likely to be maintained as a large crystal forms. Numerous randomly shaped and distributed inclusions may have contributed to the irregular crystal growth. These inclusions also caused the gray color appearance.

			The specimen’s strong surface dissolution provided a visual document of its journey from deep in the earth. At the high temperatures in the earth’s interior, diamond can remain stable only under very high pressure. As the diamond was transported to the surface, the decrease in pressure would have dissolved the stone unless it made the journey rapidly. The surface of the 1,138 ct crystal speaks to the change that took place during its journey and represents the fine line between our experiencing this rare item and never having known it at all. Source: GIA @topic:4


Title: Mixed-Type Cape Diamond Abstract: Figure 1. This 2.16 ct Fancy orangy yellow diamond is a mixed-type IaA>B. Image by Jian Xin (Jae) Liao.

                      Natural yellow type Ia or “cape” diamonds, the most common of all colored diamonds, are identified by the N3 (415 nm) and N2 (478 nm) absorption lines in the UV-visible range. These defects produce the characteristic yellow hue, and the N3 produces the blue luminescence, so often observed in these stones. Weaker bands at 452 and 465 nm may also be visible (C.M. Breeding and J.E. Shigley, “The ‘type’ classification system of diamonds and its importance in gemology,” Summer 2009 G&G, pp 96–111).

The New York laboratory recently examined a 2.16 ct Fancy orangy yellow diamond (figure 1) with unusual features for a cape stone. When analyzed with a UV-Vis spectrometer, it exhibited an unexpected 480 nm band in addition to a cape spectrum, a defect usually associated with orange color (figure 2). Infrared spectrometry revealed a well-defined IaAB diamond, as opposed to the saturated Ia spectrum typically associated with cape diamonds. These abnormal features prompted further testing, and the DiamondView revealed zoned blue and yellow fluorescence (figure 3). Raman spectroscopy of the transparent, elongate crystal within the diamond, visible in the DiamondView, identified it as a colorless garnet, a common inclusion in cape diamonds.

Figure 2. UV-visible spectrum displaying “mixed” cape (red) with overlay of “normal” cape (blue).

Figure 3. The cape diamond’s DiamondView image displays blue and yellow fluorescence, along with an elongated crystal. Image by Paul Johnson.
While the specific structure of the 480 nm optical defect is not yet understood, it is known to be associated with yellow fluorescence (Y. Luo and C.M. Breeding, “Fluorescence produced by optical defects in diamond: Measurement, characterization, and challenges,” Summer 2013 G&G, pp. 82–97). The defect is also sometimes attributed to substitutional oxygen in type I diamonds. From our data and test results showing no evidence of laboratory-produced alteration, we can conclude that this stone is a natural and very rare example of a cape diamond mixed with a 480 nm band causing the orange component. Source: GIA @topic:4


Title: The Diamond Deposits of Kalimantan, Borneo Abstract: The island of Borneo is one of the oldest known —and least reported on—sources of diamonds. Although diamond mining historically was concentrated in the western area of what is now Kalimantan, recent activity has focused on the alluvial deposits in the southeast. A progress report on the first bulk sample pit in this area found that significant amounts of diamonds appear to be concentrated beneath the center of the Danau Seran swamp. The traditional hand-mining methods contrast greatly with the sophisticated techniques used to mine the first bulk sample pit. Virtually all of the diamonds recovered are gem quality, although most are relatively small, averaging about 0.30 ct. Future potential for southeastern Kalimantan appears excellent. Source: GIA @topic:7


Title: Pink Diamonds from Australia Abstract: During the first few months of 1985, the New York office of the GIA Gem Trade Laboratory examined more than 150 gem-quality fancy pink diamonds, most of which had similar color, spectra, luminescence, color zoning, surface textures, and inclusions. This dramatic increase in the number of pink diamonds offered in the trade recently, along with the fact that a great majority exhibit similar physical properties, suggested a new source of pink diamonds. This observation, together with information received from several diamond dealers to the effect that pink diamonds had been recovered from the Australian deposits, suggests that most or all of the above-mentioned stones originated in Australia. This article reports on the gemological properties of these "new" pink diamonds and describes a number of characteristics that, seen in combination in a stone, are indicative of Australian origin. Source: GIA @topic:7


Title: The Legendary Dresden Green Diamond Abstract: The approximately 41-ct Dresden Green diamond is the largest, and perhaps the finest, green diamond known to have a color of natural origin. A diamond so rich in history is well worth studying for that reason alone, but the Dresden Green offers the unique opportunity of adding valuable data to the quest for means to distinguish natural from laboratory-irradiated green diamonds. In November of 1988, two senior GIA staff members visited the Green Vaults with this goal in mind. The Dresden Green diamond proved to be not only of extraordinary quality but also a very rare type IIa – one of the purest forms of diamond. In addition, the spectral characteristics of this stone were found to overlap those of k n m treated diamonds. The history locality origin, and properties of the Dresden Green diamond are discussed in detail in this article. Source: GIA @topic:4


Title: Modern Diamond Cutting and Polishing Abstract: This article examines the sophisticated techniques and equipment currently used to fashion a polished gem from a rough diamond. The basic manufacturing techniques— sawing, bruting, blocking, and polishing—are described with regard to the decisions that must be made to obtain the greatest value from a specific piece of rough. Over the last 25 years, the diamond-cutting industry worldwide has been revolutionized by sophisticated instruments for marking, laser sawing machines, laser kerfing machines, automatic bruting machines and laser bruting systems, automatic centering systems, and automatic polishing machines. Source: GIA @topic:4


Title: The Characteristics and Identification of Filled Diamonds Abstract: The filling of surface-reaching cleavages, fractures, and other separations in diamonds has generated a great deal of concern during the last two years. This article reports on the study of six diamonds both before and after a filling treatment and the examination of 12 additional filled stones. Microscopy provides the best means of identifying that a stone has been filled. Chemical and other analyses indicate that the filling material is a type of glass. The filling will not withstand all standard jewelry manufacturing and repair procedures. Source: GIA @topic:4


Title: The Identification of Artificial Coloration in Diamond Abstract: Since Robert Crowningshield's discovery in the late 1950s that diamonds that have been artificially colored by irradiation and subsequent annealing could be identified by their characteristic absorption spectra (in particular, the band at 595 (592) nm), much more information has become available about the radiation-related bands seen in the visible spectra of diamonds. The introduction of cryogenics has made the observation by hand spectroscope or the recording by spectrophotometer of a diamond's visible spectrum less troublesome. But it has also opened the eyes of the gemologist to the fact that virtually any band that can be artificially induced in the spectrum of diamond by irradiation and subsequent annealing can also occur naturally. This makes identification of the source of color in some diamonds, particularly fluorescent green and some yellow stones, very difficult. Source: GIA @topic:4


Title: Gemesis Laboratory-Created Diamonds Abstract: High-quality yellow, orange-yellow, and yellow-orange laboratory-created type Ib diamond crystals up to 3.5 ct are being produced commercially by the Gemesis Corp. of Sarasota, Florida. In some samples, color zoning (yellow and narrower colorless zones) and a weak UV fluorescence pattern (a small green cross-shaped zone combined with an overall weak orange luminescence) provide means of identification; when present, metallic inclusions also indicate laboratory growth. Some samples lack these diagnostic visual features, but all of these Gemesis synthetic diamonds can be identified by advanced instrumentation such as the De Beers DiamondView luminescence imaging system and EDXRF chemical analysis. Source: GIA @topic:4


Title: GE POL Diamonds: Before and After Abstract: This study of type IIa GE POL diamonds before and after HPHT annealing by GE significantly expands on their characterization. The color change was dramatic: from the N–O range through Fancy Light brown before, to D–H after. However, there was little change to the inclusions, graining, and strain as a result of HPHT exposure. Photoluminescence (PL) studies—conducted at liquid helium, liquid nitrogen, and room temperatures in the 245-700 nm range—identified a significant reconfiguration of the lattice involving substitutional impurities, vacancies, and interstitials. Key regions of PL activity included the areas of the N3, H3, and N-V centers. X-ray topography identified the extent of lattice distortion. Cathodoluminescence may help establish that a diamond is not HPHT annealed. A distinction between non-enhanced and color-enhanced type IIa diamonds can be made through a combination of observations and features. Source: GIA @topic:4


Title: A New Lasering Technique for Diamond Abstract: A new laser treatment for diamonds, which typically does not have a surface-reaching drill hole, recently entered the trade. For a better understanding of this new technique, observations were made on several round-brilliant-cut diamonds before and after treatment. Diamonds with dark inclusions near the surface are favored for this new method, which causes small cleavages to develop or expand around an inclusion. Once the cleavage reaches the surface, it serves as a conduit for the solution that is used to bleach the dark inclusion. Irregular, wormhole-like channels are used to widen the cleavage to facilitate entry of the bleaching solution. Source: GIA @topic:4


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

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

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

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

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

Type Ib CVD synthetics are also of interest for technological applications, especially for quantum computing (see E. Gibney, “Flawed to perfection: Ultra-pure synthetic diamonds offer advances in fields from quantum computing to cancer diagnostics,” Nature, Vol. 505, 2014, pp. 472–474). The N-V electron spin could be used as a basic unit of quantum computing, known as a quantum bit or “qubit.” Qubits are not limited to the binary “0” or “1” states of bits in traditional computers, but can simultaneously exist in both binary states and any state in between—a difficult concept to grasp but one that will lead to vastly enhanced computational capacity. Type Ib yellow CVD diamonds of micrometer size were grown and subsequently electron beam–irradiated and annealed by P. Neumann to create NV centers, as noted in his 2012 PhD thesis, “Towards a room temperature solid state quantum processor: The nitrogen-vacancy center in diamond.” After irradiation, the color changed from the as-grown yellow to green, then to purplish pink after annealing. Source: GIA @topic:4


Title: A History of Diamond Treatments Abstract: Although various forms of paints and coatings intended to alter the color of diamond have likely been in use for almost as long as diamonds have been valued as gems, the modern era of diamond treatment—featuring more permanent alterations to color through irradiation and high-pressure, high-temperature (HPHT) annealing, and improvements in apparent clarity with lead-based glass fillings—did not begin until the 20th century. Modern gemologists and diamantaires are faced with a broad spectrum of color and clarity treatments ranging from the simple to the highly sophisticated, and from the easily detected to the highly elusive. The history, characteristics, and identification of known diamond treatments are reviewed. Source: GIA @topic:4


Title: A Glimpse into the Russian Diamond Trade Abstract: “New Reality of the Russian Jewellery Market,” Russian Diamonds & Jewellery, No. 1, Spring 2013, pp. 14–15.

              More than 20 years after the dissolution of the Soviet regime, published statistics about Russian diamond and gem production are still difficult to come by. This article from Russian Diamonds & Jewellery is especially welcome, even if the translation into English is difficult to follow. Among the highlights:

		The 2013 initial public offering of the Russian diamond producer Alrosa was not expected to attract other major players such as De Beers because only 14% of the company’s stock went on the block. The remainder was held by the Russian government (42.9%), the Republic of Sakha (25%), and private blocs (17%).

		Alrosa also signed a deal to supply the auction house Sotheby’s with large diamonds to market through its retail diamond division. Alrosa provided two diamonds weighing between 40 and 60 ct in the first sale of this agreement. The diamonds to be sold by Sotheby’s carry GIA grading reports.

		Russia’s largest diamond polishing operation, Smolensk Kristall, has become increasingly more active in the auctioning of polished diamond. Fifty-one of 80 lots sold for $1.9 million in the first sale, which largely consisted of diamond melee.

		Russian jewelry imports have increased in recent years. In 2012, Russia imported 89.35 million tons of gold jewelry and 285.17 million tons of silver jewelry, an increase of 6.7% over the previous year.

		Local press reports have noted an increasing problem with undisclosed synthetic or imitation gemstones, diamonds and pearls being passed as natural. Source: GIA @topic:8


Title: Taming Zimbabwe’s Diamond Production Abstract: With the EU’s removal of sanctions against Zimbabwean diamonds, rough stones from the controversial Marange deposit are being auctioned in Antwerp. These diamonds often have a greenish tint. Photo by Mike Breeding and Wuyi Wang.

                      In mid-December 2013, some 280,000 carats of rough diamonds from Zimbabwe’s Marange deposit were auctioned off in Antwerp through the auspices of the Antwerp World Diamond Center (AWDC).

This sale was a trial run, consisting of mostly low-end material, but it represented a major step in efforts to transform what had been a wild card in the world diamond market—in terms of accountability, pricing and supply—into an orderly flow of rough to mainstream diamond manufacturers and dealers. Until this auction, all Marange rough had been sold through Zimbabwe’s capital city of Harare, with little or no vetting of buyers or price transparency. According to Mark Van Bockstael, who chairs the Kimberley Process Working Group of Diamond Experts, the December auction was the first step in a long-term movement to eventually route most or all Marange rough sales through Antwerp. This sale was made possible by the European Union’s Sept. 24 decision to remove all sanctions against diamonds from Zimbabwe.

Van Bockstael, who is also an executive of the AWDC, has spent considerable time on the ground in Zimbabwe. From November 2011 to December 2012, he was one of two official monitors working toward establishing Marange’s compliance with the KP.

	Mark Van Bockstael, chairman of the Kimberley Process Working Group of Diamond Experts, spent two years bringing Zimbabwe’s Marange operations into compliance with Kimberley Process standards. Photo by Russell Shor.
The auction drew criticism from many quarters, including activist groups and some members of the diamond industry who claimed the sale aided a repressive regime which routinely violates human rights. Yet Van Bockstael says the days of forced labor and uncontrolled diamond digging are long over. All seven mining concessions are secured and professionally run and mechanized, he explains, stressing that the Kimberley Process Certification Scheme (KPCS) has instituted three major steps to make certain Marange’s mining operations conform to standard.

“First, we have ensured that all of the diamond production is accounted for,” he says, pointing to a satellite map of the Marange area mounted on the wall of his Antwerp office. “We can track production via satellite imaging. We know the grade (carats per ton of ore) of each concession, and through satellites we can see how much material is extracted each month. We check this information against company ledgers to verify their reporting.

“Second, all production data is matched against the exports listed on Kimberley Process certificates to ensure it is all sold legitimately.

“Third, we monitor the security of the area. All unlicensed mining is illegal, and we made sure local officials enforce this law,” he notes, adding that incidents of illegal artisanal mining have fallen to near zero in the past two years. All of the mining concessions are enclosed, with double fencing around the actual mining areas and additional security features at the processing plants to minimize unauthorized production.

“An additional fourth step is unrelated to the KPCS, but is a result of moving the rough diamond sales to Antwerp, which puts them under strict European Union guidelines regarding finance and transparency.”

The controversy over Marange erupted in 2007–2008 after thousands of artisanal diggers migrated there to work the newly discovered diamond deposit. Forces controlled by the country’s leader, Robert Mugabe, evicted the miners in a brutal campaign in late 2008 that reportedly left 180 dead and hundreds wounded. Following these forced evictions came allegations that Zimbabwe’s government forces continued to commit human rights abuses, including rape and forced labor, against the remaining miners and their families. As a result, the U.S. and the European Union, which had already imposed sanctions on enterprises controlled by Mugabe and his inner circle, banned diamond companies based on their own soil from dealing in Marange diamonds.

The abuses at Marange created a crisis within the Kimberley Process as well. The KPCS was established in 2003 to prevent rebel or terrorist groups from illegally mining and selling diamonds to finance their activities, requiring certificates for all rough diamonds to guarantee they were exported legally. The fact that the officially recognized Zimbabwean government, rather than a rebel group, was charged with the human rights abuses created sharp divisions within the organization, and brought intense criticism from human rights organizations and some governments. The KPCS was portrayed as toothless—or, worse yet, complicit in the country’s disregard for human rights, particularly after its 2011 decision to conditionally approve Marange diamonds for export.

Van Bockstael has heard all of the criticisms, but stresses that the KPCS has gone far beyond its charter to bring order to Marange’s chaotic diamond production.

“They accuse us of doing nothing, but we worked hard for two years to make certain all of the operations were compliant with KPCS standards,” he says, adding that in his time on the ground he did not witness human rights abuses. He also notes that the seven government-approved concession holders “have done their due diligence in regards to water use, ecological and environmental protection. We have monitored their operations so we know they are fully compliant to KPCS standards.”

Van Bockstael does acknowledge there are complaints from NGOs, especially over artisanal mining. “It’s even illegal for people to dig for diamonds—even in their own villages, in their own backyards. They don’t like that, but allowing such digging makes it impossible to account for the production.”

One of the mining companies working the Marange deposit, the Chinese-Zimbabwean venture Anjin, relocated 417 families from its concession. The workers are now complaining they haven’t received the benefits they were promised, but Van Bockstael says it was considered an exemplary move at the time and a model for future relocations, even by local NGOs.

Critics of the KPCS insist that the repressive Mugabe regime benefits from the diamond funds, siphoning off the proceeds to fund the state’s security forces, which continue to engage in human rights abuses. People living in the diamond-producing areas, they add, do not benefit from diamond production in their midst.

Van Bockstael says some critics believe there can only be “satans or saints in the world.” The reality, he stresses, is somewhere in between: that there are huge quantities of diamonds in Zimbabwe, and they will be mined and sold regardless of the circumstances. In this case, he says, the best that can be done is to harness the flow of diamonds from that country and ensure they enter the trade legitimately. Addressing charges that funds are siphoned off, Van Bockstael maintains that “all of the mining companies must provide detailed, transparent accounts of their sales, including taxes and royalties paid to the government. Under Zimbabwe law, mining companies have to pay 15% royalty on the value of diamonds mined, but the investor-friendly laws allow corporate taxes to be deferred until they recoup their capital investment.”

Marange’s 2014 diamond production is expected to reach nearly 17 million carats, valued at $53.10 per carat, the lowest of any major producer except Australia. (The two other mining operations in Zimbabwe, River Ranch and Rio Tinto’s Murowa, were not affected by KPCS sanctions.) According to KPCS figures, a significant percentage of Marange production consists of larger goods up to five carats, but only 8% of the output is of gem quality. An additional 8% is called near-gem or “lower rejections,” meaning that only a small percentage of each rough stone can be polished into a diamond usable in jewelry. The remaining 84% are rejections and bort, the industrial diamonds used primarily as abrasives.

In addition, Marange’s gem-quality diamonds usually trade at a discount, because they often have a slightly greenish tint, even in higher colors. This tint makes them difficult to match in jewelry when using stones from multiple sources. Dealers compare them to rough diamonds from Australia’s Argyle mine, which have a brownish cast and similarly trade at a discount. Despite this, Van Bockstael believes that $53 per carat average price could be improved substantially by moving the sales to Antwerp’s more transparent environment.

	Antwerp’s main diamond trading street, Hoveniersstraat, is the new site for much of the Zimbabwe rough diamond sales. Photo by Russell Shor.
More changes to Marange’s production are anticipated. The deposit is vast, covering more than 400 square miles, but the shallow, easily mined areas are nearly depleted and mining companies will have to dig deeper—much deeper—to extract diamonds. Van Bockstael believes that mining operations will consolidate as production costs rise, particularly because the quality is so low.

Marange, he notes, is technically not an alluvial deposit, nor is it a kimberlite pipe. The diamonds originated from an unknown source and were deposited by seawater into a bowl-shaped bed millions of years ago; they now lie under a conglomerate of rock and soil. The Marange diggings are at the northwest rim of this bowl, where the diamonds can be found under a few meters of overburden. The grade of the rim, or reef, is also very high—about two carats per ton. (By contrast, most diamond mines average about one carat per hundred tons.) About 50 miles to the southeast lies the more recently discovered Chimanimani diamond deposit, which geologists have identified as the opposite rim of this bowl. In between, the bowl deepens to some 3,000 feet.

“First, the companies operating the deposit do not have much experience with deep mining,” says Van Bockstael. “Second, it is much, much more expensive.”

During the same week as the first Marange tender, Anjin Investments Ltd. announced it was laying off 25 percent of its 845-strong workforce because of rising costs and stagnating rough diamond prices. The company attributed the rising costs to the transition to underground mining.

Zimbabwe’s ruler, Robert Mugabe, who will turn 90 this year, was re-elected in July 2013 amid charges of election fraud. Still, Van Bockstael believes Zimbabwe has the means to achieve stability and growth in the future, because there is a well-developed professional class managing a number of enterprises (including the mining sector) and an encouragingly independent judiciary and police force. He warns, however, that old vested interests could still work against making Marange more transparent.

“The sales in Antwerp are encouraging, but they are not a done deal,” he says.

The government claimed the December tender of Marange rough a success. The permanent secretary of mines and mining development, Francis Gudyanga, said the trial tender, attended by 115 buyers, “will allow the government of Zimbabwe to fully optimize a second, larger tender of Marange goods in the future.”

The average price of $38.25 per carat for the low-end parcels was well below the run-of-mine average, but Van Bockstael hopes this figure will increase substantially as goods more representative of the production are offered for sale in the future.

The second Antwerp tender, held Feb. 12–19, consisted of 960,000 run-of-mine from six companies mining the Marange area and realized $70 million, or about $72.90 per carat, substantially above the average price of goods coming from that area. Some 167 companies participated, according to Zimbabwe’s news media. Nevertheless, Secretary Gudyanga stressed that some goods would continue to be tendered in Zimbabwe. Source: GIA @topic:8


Title: Spinel Submitted as Diamond Abstract: Figure 1. This rough spinel, submitted as a diamond, displayed trigons oriented in the direction opposite that of the crystal face. Photo by Joshua Balduf.

              Diamond simulants remain in wide circulation and are a common sight in the GIA laboratory. Even so, it is rare that we encounter a natural gemstone masquerading as a colored diamond. The New York laboratory recently received a 0.50 ct rough sample with a remarkably saturated Fancy Intense to Vivid pink color (figure 1) for a Colored Diamond Identification and Origin Report. The stone displayed octahedral crystal form with numerous trigons on its crystal faces. These triangular etch pits, caused by chemical dissolution, are common characteristics of both natural diamond and spinel but have also been observed in flux synthetic spinels (M.S. Krzemnicki, “Trade Alert: Flux grown synthetic red spinels again on the market,” SSEF Newsletter, October 14, 2008, p. 3). When found on octahedrons, trigons point in the direction opposite that of the crystal face (again, see figure 1). Figure 2 shows a distinctive conchoidal fracture amid the trigons, a feature alien to diamond. This feature, along with the sample’s striking color, indicated something other than diamond.

	Figure 2. In addition to trigons, the spinel displayed a conchoidal fracture (see arrow), a feature not found in diamond. Photomicrograph by Martha Altobelli; magnified 40x.
The high-resolution UV-Vis spectrum displayed emission bands and absorption peaks not seen in natural diamond. Closer examination of the photoluminescence spectrum affirmed chromium peaks at 685, 687, 689, and 700 nm. Chromium causes the red/pink color in spinel but is not present in diamond. The narrow bandwidth of the 685 nm peak, along with the presence of the ~533 nm band in the UV-Vis spectrum, proved this was an untreated stone (S. Saeseaw et. al., “Distinguishing heated spinels from unheated natural spinels and from synthetic spinels: A short review of on-going research,”  www.giathai.net/pdf/Heated_spinel_Identification_
at_May_25_2009.pdf). Other observations included a specific gravity of 3.45–3.48, consistent with spinel, as well as medium to strong red long-wave and short-wave UV. Though submitted for a diamond report, this stone was actually a natural pink spinel.

This finding serves as a reminder of the importance of both standard gemological techniques and advanced spectroscopy in identifying gem materials. Source: GIA @topic:4


Title: Spinel Submitted as Diamond Abstract: Figure 1. This rough spinel, submitted as a diamond, displayed trigons oriented in the direction opposite that of the crystal face. Photo by Joshua Balduf, © GIA

                      Diamond simulants remain in wide circulation and are a common sight in the GIA laboratory. Even so, it is rare that we encounter a natural gemstone masquerading as a colored diamond. The New York laboratory recently received a 0.50 ct rough sample with a remarkably saturated Fancy Intense to Vivid pink color (figure 1) for a Colored Diamond Identification and Origin Report. The stone displayed octahedral crystal form with numerous trigons on its crystal faces. These triangular etch pits, caused by chemical dissolution, are common characteristics of both natural diamond and spinel but have also been observed in flux synthetic spinels (M.S. Krzemnicki, “Trade Alert: Flux grown synthetic red spinels again on the market,” SSEF Newsletter, October 14, 2008, p. 3). When found on octahedrons, trigons point in the direction opposite that of the crystal face (again, see figure 1). Figure 2 shows a distinctive conchoidal fracture amid the trigons, a feature alien to diamond. This feature, along with the sample’s striking color, indicated something other than diamond.

	Figure 2. In addition to trigons, the spinel displayed a conchoidal fracture (see arrow), a feature not found in diamond. Photomicrograph by Martha Martha Altobelli, © GIA. Magnified 40x.
The high-resolution UV-Vis spectrum displayed emission bands and absorption peaks not seen in natural diamond. Closer examination of the photoluminescence spectrum affirmed chromium peaks at 685, 687, 689, and 700 nm. Chromium causes the red/pink color in spinel but is not present in diamond. The narrow bandwidth of the 685 nm peak, along with the presence of the ~533 nm band in the UV-Vis spectrum, proved this was an untreated stone (S. Saeseaw et. al., “Distinguishing heated spinels from unheated natural spinels and from synthetic spinels: A short review of on-going research,”   www.giathai.net/pdf/Heated_spinel_Identification_at_May_25
_2009.pdf ). Other observations included a specific gravity of 3.45–3.48, consistent with spinel, as well as medium to strong red long-wave and short-wave UV. Though submitted for a diamond report, this stone was actually a natural pink spinel.

This finding serves as a reminder of the importance of both standard gemological techniques and advanced spectroscopy in identifying gem materials. Source: GIA @topic:4


Title: Diamond Care and Cleaning Guide Abstract: Consumers know diamond from the slogan “A Diamond is Forever”. With some care considerations this is relatively true. The Asscher cut was popular decades ago and is again a very popular cut style. This stone has exceptional quality being D color and VVS2 Clarity.

                      “A Diamond is Forever” is one of the world’s best-known advertising slogans. It has many different meanings. It refers to diamond’s timeless appeal. It refers to diamond’s icy beauty. And it also refers to diamond’s durability. One result of the diamond formation process is its incredible durability.

Durability is a gemstone’s ability to withstand wear, heat, and chemicals. Durability consists of three properties: hardness, toughness, and stability. Hardness means how well a gemstone resists scratches and abrasion. Toughness describes how well a gemstone resists breaking and chipping. Stability means how well a diamond resists chemicals and temperature changes.

Hardness
Gem and mineral hardness is measured on the Mohs scale. The scale originated in 1812 when German mineralogist Friedrich Mohs chose ten minerals and assigned numbers to them, based on the relative ease or difficulty with which one could be scratched by another. But the Mohs scale is deceptive. The steps between the minerals are not evenly spaced. For example, diamond is only one number away, but it’s many times harder than gems in the corundum family. Only a diamond can scratch a diamond.

Something the Mohs scale doesn’t show, but that’s equally important to the diamond industry, is that diamond can also scratch any of the precious metals used for settings. That means a diamond that’s loose in its setting can wear through a prong over time.

	Diamond rates highest on the Mohs hardness scale, at number 10.
Toughness
Any stone, including a diamond, will break if it’s hit hard enough in the right place. Toughness is a measure of how well a gem can survive an impact and resist breaking, chipping, or cracking.
Diamonds are tougher in the directions where the atoms are bonded tightly together, less tough where they’re not so tightly bonded.

	Cutting styles with pointed corners or ends are often set with prongs to protect the corners from chipping. - Courtesy Ambar Diamonds
The weakest directions are the ones where the atoms are farthest apart. It’s easier to break a diamond in those directions, which are called cleavage directions. A cutter can cleave a diamond by hitting it sharply in the cleavage direction. But even after cutting, a hard blow can still cleave a diamond. This can happen during the setting process, or even when it’s being worn.

Stability
Stability is a term that describes how well a diamond resists temperature changes and chemicals. Diamonds are very stable. They’re invulnerable to virtually all acids, for one thing. The cutting process generates a lot of heat, but diamonds usually endure intact. Situations that are more threatening to a diamond’s stability are those that involve sudden and extreme temperature changes. Those changes can cause thermal shock and create new fractures and cleavages or cause existing ones to spread.

Diamonds will burn at about 1562°F (850°C). House fires and jewelers’ torches can reach that temperature.

	A house fire caused the white, cloudy appearance of this diamond (left). The stone was recut to remove the burned area, reducing the diamond’s size, but leaving no sign that it was ever damaged (right).
Cleaning
Diamonds can be cleaned safely with lint-free cloths, commercial jewelry cleaning solutions, and household detergents.

Harsher cleaning methods are not recommended for home use. These include powdered abrasive household cleansers, ultrasonic cleaners, and steam cleaners.

	Ultrasonic cleaners and steam cleaners can loosen gemstones in their settings. Jewelry professionals carefully examine jewelry for loose stones before using these devices. Source: GIA @topic:4


Title: Diamond Digging in Ghana Abstract: Artisanal miners work a deposit near Ghana's Birim River.

                      Akwatia, Ghana, is a town built by diamonds. Rows of low, corrugated rooftops branch out from the old town center. On the outskirts, where the small-scale farms begin, an occasional mansion rises beside the highway. Some of these mansions are owned by the lucky ones—diggers who found a cache of large diamonds. Most belong to the concession holders who take a cut from the finds of the galamsey, the local name for artisanal diggers who work the river banks.

A half century ago, Akwatia was one of the most productive diamond spots on the planet. Diamonds were discovered at the nearby Birim River in 1920, when the nation was a British colony called the Gold Coast. By the end of that decade, production neared a million carats yearly, doubling by 1935.

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The Birim River remained one of the world’s most productive sources through Ghana’s independence in 1957, until the late 1970s when the richest areas were mined out and the aging mining equipment was unable to efficiently process smaller, lower-quality stones. Today, that is most of what the artisanal diggers recover: Of the 301,000 carats mined and exported each year, the vast majority are darker stones smaller than 0.10 ct.

	A diamond buyer sorts the finds of a local miner.
In the late 1980s, the government allowed the small-scale miners to work areas along the 40-mile diamond-bearing stretch of the Birim River, an area unsuitable for mechanized mining. While some miners have registered, in compliance with government requirements, about 75% have not.

In 2012, an investor group announced a $100 million plan to revive mechanized mining at Birim River. Still, the government and investors have pledged to maintain concessions for the artisanal diggers who now sustain the economic life of the region. Source: GIA @topic:7


Title: Flame-Like Surface Structure in a Nacreous Atypical Bead Cultured Pearl Abstract: Figure 1. A white button-shaped atypical bead cultured pearl weighing 8.15 ct and measuring 11.73 × 11.35 × 9.03 mm. Photo by Gaurav Bera.
GIA’s Mumbai laboratory recently received an atypical bead cultured pearl with a unique surface appearance. The white button-shaped pearl weighed 8.15 ct and measured 11.73 × 11.35 × 9.03 mm (figure 1).

Figure 2. Rounded depressions forming the flame-like structure. Photomicrograph by Nishka Vaz; field of view 0.4 mm.
Viewed under 40× magnification, the surface exhibited typical fine nacreous overlapping aragonite platelets, but a distinct pattern similar to the flame structures observed in some porcelaneous pearls was also noted (Summer 2021 Lab Notes, pp. 152–153). These flame-like features were formed due to the presence of relatively opaque, frosty white rounded depressions on the pearl’s surface. Although rounded, they seemed to be oriented longitudinally and were more tapered toward the base and apex and broader along the sides of the pearl (figure 2). Also observed on the surface were small white spots with slightly elongated comet tails that flowed tangentially to the circumference of the button. The base and apex of the pearl lacked the whitish subsurface opaque features that produced the flame structure effect, and these two areas appeared more translucent than the other parts of the pearl.
Under long-wave ultraviolet radiation, the pearl showed a strong yellowish green reaction, and a similar but weaker reaction was noted under short-wave ultraviolet radiation. The deep-UV (<230 nm) radiation of the DiamondView instrument revealed a clear bluish reaction, with the surface showing a chalky white flame-like structure extending from the apex center across the pearl. Raman analysis of the pearl’s surface using a 514 nm excitation showed a doublet at 701/704 cm–1 as well as peaks at 1086 and 1464 cm–1 characteristic of aragonite. The photoluminescence spectra revealed high fluorescence, with a maximum centered at approximately 620 nm.

Figure 3. XRF reaction of the pearl, with the sides appearing brighter than the base and apex.
Energy-dispersive X-ray fluorescence spectrometry revealed a low manganese level of 16.9 ppm and a higher strontium level of 1577 ppm, indicative of a saltwater environment. However, when exposed to X-ray fluorescence (XRF) analysis, the pearl exhibited a moderate yellowish green fluorescence with a higher intensity toward the sides but a weaker reaction on the base and apex (figure 3). Saltwater pearls are usually inert when tested by this method, while freshwater pearls and saltwater bead cultured pearls with freshwater shell nuclei tend to fluoresce weak to strong yellowish green. In the case of bead cultured pearls, a thinner nacre usually produces a stronger reaction; conversely, the thicker the nacre, the weaker the reaction.

Figure 4. Left: RTX image of the pearl’s internal structure with a large linear feature. Right: μ-CT image showing a freshwater-type linear feature in the center and a faint boundary (arrow).
Real-time microradiography imaging (RTX) revealed a long, complex linear feature in the center typically associated with non-bead cultured pearls (figure 4, left). When viewed under X-ray computed microtomography (μ-CT), the linear feature looked very similar to those often observed in freshwater non-bead cultured pearls. A faint boundary was also seen around the central linear feature (figure 4, right) and other growth rings. All these observations, together with the XRF reaction of the pearl and the saltwater chemistry, were indicative of an atypical bead cultured saltwater pearl with a freshwater pearl used as its nucleus (P. Kessrapong and K. Lawanwong, “Atypical bead cultured Pinctada maxima pearls nucleated with freshwater non-bead cultured pearls,” GIA Research News, April 6, 2020). The nacre thickness overlying the freshwater non-bead cultured pearl nucleus ranged from approximately 1.09 to 1.90 mm. The thicker nacre was positioned near the base and apex and the thinner nacre toward the sides. This aligned with the XRF reaction observed, as a thinner saltwater nacre will allow more fluorescence from the freshwater pearl nucleus to pass through the nacre layers, while thicker nacre masks the reaction.
Over the years, GIA has encountered similar atypical bead cultured pearls with sizeable freshwater non-bead cultured pearls used as a nucleus (Spring 2023 Lab Notes, pp. 74–76). However, the presence of flame-like structures seen on nacreous pearls is a very rare phenomenon. This combination of interesting culturing along with the unique surface features make this pearl noteworthy. Source: GIA @topic:5


Title: An Unusual Metallic Core in a Natural Pinctada radiata Pearl from Kuwait Abstract: Figure 1. The cream-colored pearl weighing 0.23 ct and measuring 3.20 × 3.12 mm, shown against the anterior of a Pinctada radiata mollusk. Photo by Nuttapol Kitdee.
The pearl (oyster) beds, or heirat in Arabic, around the State of Kuwait in the Persian (Arabian) Gulf have been known throughout history for producing some of the finest natural pearls. GIA’s Bangkok laboratory recently examined a quantity of these pearls obtained from a Kuwaiti pearl diver. The trusted diver said they were fished from wild Pinctada radiata mollusks at depths of 6 to 15 meters from one of the main pearl beds in the waters of Kuwait. The parcel consisted of various shapes and colors ranging from white to light yellow, with a few colored pearls as well.
The samples showed a variety of internal structures, but one round cream-colored pearl in particular, weighing 0.23 ct and measuring 3.20 × 3.12 mm (figure 1), revealed an interesting structure using real-time microradiography (RTX) and X-ray computed microtomography (μ-CT) analyses. When viewed under 40× magnification, the pearl’s smooth and high-luster surface exhibited typical nacreous overlapping aragonite platelets.

Figure 2. Top: RTX images revealing the entire volume of the pearl’s internal structure in two different directions. Bottom: Slightly enlarged μ-CT scans showing the radiopacity of the core more clearly. The darker areas are organic-rich.

Figure 3. RTX image of a bead cultured pearl reference sample with a metal post in the drill hole. The metal appears radiopaque and matches the appearance of the core feature in the pearl examined in the present study.

Figure 4. The 3D models generated using μ-CT scans show the blue area as the metallic core, while the surrounding area represents the pearl’s growth structure.

	3D Model of a Pinctada radiata Pearl with a Metallic Core

RTX imaging revealed a very unusual small ovalish radiopaque white core located in the pearl’s center. The radiopaque core stood out in contrast to the rest of the pearl’s structure (figure 2), indicating that the feature was composed of a material containing elements with higher atomic numbers on the periodic table. The appearance of the core was typical of that seen for metals when examined by X-rays, such as the metal post within the drill hole of the pearl in figure 3. The core measured approximately 0.19 × 0.15 × 0.13 mm and was surrounded by fine concentric rings with a small area of associated radiolucent organic-rich material. The small organic-rich area extending toward the outer growth layers appeared darker gray in the RTX and μ-CT images. Although the metallic core created doubts about the pearl’s origin, the associated concentric ring structure surrounding it was more indicative of natural origin. The μ-CT scan images were also rendered using specialized software (“New 3-D software expands GIA’s pearl identification capabilities,” GIA Research News, May 13, 2016) to create a three-dimensional image that made it easier to visualize the form of the central metal core (figure 4; see video of the 3D model).
Energy-dispersive X-ray fluorescence spectrometry revealed no manganese and a strontium level of 1400 ppm, which is characteristic of a saltwater environment. Raman analysis using 514 nm laser excitation was also carried out on the pearl’s surface and showed a doublet at 702 and 705 cm–1 as well as a peak at 1085 cm–1 indicative of aragonite. Weak polyenic pigment peaks associated with the pearl’s cream coloration were also observed at around 1135 and 1530 cm–1. Ultraviolet/visible reflectance spectra showed features at around 410, 435, and 460 nm and an additional band at 495 nm, in keeping with observations previously recorded for Pinctada radiata pearls (A. Al-Alawi et al., “Saltwater cultured pearls from Pinctada radiata in Abu Dhabi (United Arab Emirates),” Journal of Gemmology, Vol. 37, No. 2, 2020, pp. 164–179).
Although GIA was not permitted to cut the pearl in half or grind the surface down to reach the metal, we believe the feature may be a metal oxide similar to one previously documented (M.S. Krzemnicki, “Pearl with a strange metal core,” SSEF Facette, No. 24, 2018, p. 27). How this apparent metal found its way inside the mollusk is still a mystery. Since the diver found the pearl with other natural pearls that GIA also examined and confirmed, and it came from an area that lacks any pearl farms, it seems unlikely that a human inserted the metal core as a bead nucleus. It is possible that the core resulted from the pollution the region witnessed after the Gulf War in 1992, and a foreign metallic particle found its way into a mollusk. Residue from the shipping industry is another possibility, with potential pollution from the heavy volume of oil tankers and other vessels in the area. Hence, water contamination may be a convincing explanation for the unusual structure observed in this unique and fascinating natural Kuwaiti pearl. Source: GIA @topic:5


Title: A Partially Hollow Natural Blister Pearl Filled with Foreign Materials Abstract: Figure 1. The 169.05 ct filled pearl, viewed from its face (left) and base (right). Note the indented feature on the base through which the filler material was inserted prior to plugging. Photos by Gaurav Bera.
Over the centuries, India has maintained its reputation as a natural pearl trading center. Since the launch of GIA’s pearl identification service in Mumbai in May 2022, the laboratory has received a variety of interesting items for identification. One that stood out owing to its size and internal structure was a unique partially hollow natural blister pearl with unidentified fillers (figure 1).

Figure 2. A: The pearl’s face showed minor surface blemishes; field of view 8.00 mm. B: The plugged area (boundary indicated by arrows) on the base with remnants of an adhesive around the oval opening; field of view 1.60 mm. C and D: Smoothed nacre layers provide evidence of heavy working and polishing on the base; field of view 3.00 mm. Photomicrographs by Nishka Vaz.
The very large baroque white pearl weighed 169.05 ct (33.81 g) and measured 43.12 × 28.83 × 19.26 mm. However, on initial examination, its “heft” (perceived weight compared to its actual weight in comparison to its size) felt heavier than it should have. While the pearl’s face-up side exhibited minor surface blemishes and good nacre condition (figure 2A), its base showed a deep oval indentation that looked a bit suspect to the unaided eye and needed further detailed examination. Under 40× magnification, the area revealed a distinct boundary with remnants of a transparent adhesive around it (figure 2B). Evidence of heavy working and polishing on and around the base was also clearly visible (figure 2, C and D).
Many loose nacreous baroque or semi-baroque pearls of this size are hollow to some degree, and most turn out to be blister pearls that were attached to the shell and removed at some point (“An unusual pearl,” GIA Research News, March 31, 2009) or were shell blisters. In order to ensure the durability of these hollow pearls, and sometimes to add weight and increase their perceived value, they are filled with various materials such as metals, resins, waxes, shell, and other pearls (Fall 2013 Lab Notes, pp. 172–173) and fashioned to improve their external appearance. Although the initial examination indicated that this pearl was likely filled with foreign materials, further analysis was required.

Figure 3. Opaque (white) areas indicate that metal pieces were placed within the pearl’s large internal cavity (left). Natural growth arcs and a small darker organic-rich area are visible at the pearl’s base (right). Images by Jayesh Surve.
Real-time microradiography revealed a large organic void/cavity filled with a radiopaque white material, probably small metal fragments or metal shavings (figure 3; see also Summer 2019 Lab Notes, pp. 251–254). Areas of greater radio-transparency suggested that some type of bonding or stabilizing material, possibly adhesive, may have been used to hold the foreign pieces in place, and there also appeared to be one other type of radiolucent material within the cavity. The pearl was examined in several directions in order to further analyze the internal structure and fillings. The outline of the void was smooth and blended with the external shape of the pearl. The outer nacre layers revealed fine growth arcs and a small organic-rich area was visible at the base, both of which aligned more with the growth features of a natural pearl. It was clear that this was originally a blister pearl or shell blister that had been cut from a shell, and that the indented area, which was the opening on the base of the pearl, was the point of attachment that was subsequently plugged. X-ray fluorescence proved that the pearl formed in a saltwater environment since most of its surface appeared inert and only a small area at the base displayed a very light greenish yellow reaction uncharacteristic of a freshwater environment.
Energy-dispersive X-ray fluorescence spectrometry on two areas (face and base) showed low or below detection levels of manganese and higher strontium levels, above 1000 ppm, both characteristic of a saltwater environment. The higher strontium levels coupled with the large size indicated that the mollusk from which the pearl originated was Pinctada maxima.
Raman analysis using a 514 nm laser excitation on two spots (face and base) of the surface produced high fluorescence due to the pearl’s light color and showed a doublet at 702 and 705 cm–1 as well as a peak at 1085 cm–1 indicative of aragonite. The photoluminescence spectra also displayed high fluorescence together with the aragonite peaks, as observed via Raman, typical of most nacreous pearls. Ultraviolet/visible/near-infrared spectra within the 220–850 nm range collected from the face and base were as expected for white to light cream-colored pearls and showed a predominantly high reflectance. The presence of a prominent 280 nm absorption feature coupled with moderate yellow reaction under long-wave UV excitation indicated that bleaching had most likely not been carried out.
After conducting a full analysis, GIA concluded that this sample most likely formed as a hollow natural blister pearl attached to its shell host. At some point, it was removed and the attachment area left an opening into the pearl. It was eventually worked and filled with foreign fillers (metal shavings/pieces and possibly some other materials) to improve its durability and make it suitable for setting; without the filling, it would not be usable in jewelry. The size, spectral characteristics, and chemistry were also consistent with a Pinctada maxima host mollusk. Source: GIA @topic:5


Title: Conservation Concerns over Use of Tridacna Shell in Imitation Pearls Abstract: Figure 1. Left: This white shell bead (10.08 mm) was visible after the coating was removed from one of the imitation pearls. Right: A subtle flame structure was observed on the surface of the shell bead; magnified 40×. Photos by Jessie Yixin Zhou.

              Last year the New York laboratory reported on the use of shell as a pearl imitation (Summer 2014 Lab Notes, pp. 153–154) and the improper nomenclature applied by those marketing it. We decided to delve deeper and investigate the nature of the shell beads used in such imitation pearls following correspondence with Dr. Henry A. Hänni, who previously reported on this issue (see Summer 2004 Gem News International, p. 178, and references within).

After removing the outer coating on one of the imitation pearls by immersing it in acetone, we observed a banded white bead (figure 1, left). Magnification revealed fine and subtle flame structures (figure 1, right), indicating the bead was most likely fashioned from the shell of a Tridacna (giant clam) species.

All species of the Tridacnidae family are currently listed in Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). Some species, such as Tridacna gigas, are more vulnerable than others, such as Tridacna squamosa or Tridacna maxima. These large saltwater clams can have heavy shells fluted with multiple folds (figure 2) and colorful mantles. Their natural habitats lie in the warm marine waters of the Indo-Pacific, a fragile region that has been heavily impacted by human activities.

Figure 2. These three shells of Tridacna species are part of the collection at GIA’s Bangkok laboratory. The two largest measure approximately 33 × 20 cm each. The two larger shells were found empty by Thai divers, while the smaller shell was donated to the Bangkok lab several years ago and comes from an unknown source. Photo by Nuttapol Kitdee.
These beautiful marine animals are commonly harvested from their natural habitats or aquaculture farms for food (Center for Tropical and Subtropical Aquaculture Publication No. 114, University of Hawaii), and their shells are fashioned into beads or ornaments that are prized by some cultures. Despite their protection under CITES, these shell products are readily available on the Internet and often very inexpensive (figure 3). Imitation shell “pearls” fashioned from these endangered and protected mollusks do not offer any obvious advantages over common freshwater mussel shells, and it is extremely difficult to identify the exact Tridacna species or whether the mollusks were farmed or harvested from the wild. We urge manufacturers to stop using Tridacna shell beads when producing imitation pearls.

Figure 3. Tridacna shell beads of various sizes (4.5 to 10.5 mm) are readily available from various commercial sites. The carved beads shown on the left are marketed as “Tibetan prayer beads.” Photo by Sood Oil (Judy) Chia. Source: GIA @topic:5


Title: Treated Freshwater Non-Bead Cultured Pearls with an Antique Appearance Abstract: Figure 1. A group of 12 pearls ranging from 7.38 × 6.49 × 6.05 mm to 10.61 × 9.05 × 8.05 mm and weighing 44.37 carats total. Photo by Jayesh Surve.
GIA’s Mumbai laboratory recently received for identification a group of nine drilled and three undrilled pearls weighing 44.37 carats total and ranging in size from 7.38 × 6.49 × 6.05 mm to 10.61 × 9.05 × 8.05 mm. The nine drilled pearls appeared to be old, while the three undrilled pearls looked whiter and much newer overall (figure 1). The shape of the samples varied, and the nine drilled pearls possessed a notable “aged” yellow coloration, which was also evident on some areas of the three undrilled whiter pearls.
The older-looking pearls possessed a dull luster, but the nacre condition was good. Microscopic examination at 70× magnification soon revealed that the color was concentrated on the outer layers and within surface-reaching features, proving that the color was not natural and a treatment had been used to alter their appearance (Summer 2017 Gem News International, pp. 255–256).
Although the color of pearls can change over time due to various causes (e.g., care factors such as storage conditions and contact with chemicals), these changes tend to be very gradual and develop over many years. This is partly due to their biogenic composition, which mainly consists of calcium carbonate with traces of organic substances, residual substances, and water. Dry environments are generally not advisable as they may result in surface alterations and, in rare cases, weight loss. The color can also change over time through wear and tear and the accumulation of external contaminants, so further analysis was required to prove whether these pearls naturally discolored over time or were treated to look antique, thereby inflating their value (M.S. Krzemnicki, “Fake historic provenance: ‘Aged’ cultured pearls,” Facette, No. 25, 2019, p. 28).

Figure 2. Two of the samples showing uneven surface coloration and color concentrations around the large drill holes. The worked surfaces around the drill holes are also clearly visible. Photos by Jayesh Surve; field of view 6.00 mm.

Figure 3. An area of underlying white color below the treated surface of one of the samples. Photomicrograph by Jayesh Surve; field of view 5.00 mm.
Visually, it was readily apparent that the drill holes were very large in relation to the size of the pearls. When viewed with a 10× lens or under a gemological microscope at 70×, color concentrations were observed around the drill holes of all nine drilled pearls. The surfaces were also heavily worked around the drill holes and did not resemble the wear and tear that might be expected on antique pearls. The surfaces of the nine drilled samples (2–4 and 7–12) were also slightly etched, indicating possible exposure to a mild acidic solution to create an “aging” effect. Strikingly, the color was not typical of natural-color pearls (Summer 2017 Gem News International, pp. 255–256) and appeared to be restricted to the surface and around the drill holes (figure 2). Areas on some pearls also revealed the original underlying white color, further proof of treatment (figure 3).

Figure 4. The internal structures of four of the pearls showed twisted void-like features surrounded by fine growth arcs characteristic of non-bead cultured freshwater pearls. The two wide vertical gray features seen in pearls 3 and 4 are the drill holes.
Next, we needed to determine whether the pearls originated from a saltwater or freshwater environment, and whether they were natural or cultured. Real-time microradiography revealed small central twisting void-like features surrounded by fine growth lines typical of freshwater non-bead cultured pearls (figure 4), consistent with those produced by Chinese farms (K. Scarratt et al., “Characteristics of nuclei in Chinese freshwater cultured pearls,” Spring 2000 G&G, pp. 98–109). The freshwater origin was confirmed when the pearls fluoresced a strong yellowish green color upon exposure to X-ray fluorescence, and further substantiated by manganese values ranging from 500 to 1700 ppm and strontium values from 800 to 1000 ppm, obtained by energy-dispersive X-ray fluorescence spectroscopy.
Since Raman spectroscopy is also a valuable analytical tool for differentiating natural versus treated color in pearls, 514 nm ion-argon laser excitation was used on the surfaces. The results revealed a doublet at 702 and 705 cm–1, as well as a peak at 1085 cm–1 indicative of aragonite, which is seen in the majority of pearls. High background fluorescence, often characteristic of treated-color pearls, was also noted in the drilled pearls. The photoluminescence spectra obtained displayed high fluorescence more typical of treated pearls, as well as the expected aragonite peaks. Other than the suspiciously high fluorescence, no other peaks characteristic of dyeing were observed.
All observations and results indicated that the nine drilled pearls had been treated to make them look antique. Pearls 1, 5, and 6 were predominantly white and showed only minimal evidence of any artificial aging attempts. These three showed a reaction to long-wave UV fluorescence more indicative of routine processing carried out on freshwater pearls. We concluded that these freshwater non-bead cultured pearls were also treated to make them appear aged. Hence, the report stated that these were freshwater non-bead cultured pearls from the Unionidae family and that pearls 2–4 and 7–12 had been color modified. Since the majority of the surfaces of pearls 1, 5, and 6 remained white and only showed insignificant areas of discoloration, the modified color description was not applied. Source: GIA @topic:5


Title: Pinctada radiata Atypical Bead Cultured Pearls from the UAE Abstract: Figure 1. Two atypical bead cultured pearls recovered from Pinctada radiata mollusks from Abdulla Al Suwaidi’s farm in the UAE. Pearl A (left) weighs 0.87 ct, and pearl B (right) weighs 0.94 ct. Photo by Gaurav Bera.
Pearling is embedded in the culture and traditions of everyday life in the United Arab Emirates (UAE), especially in the trading center of Julfar. Abdulla Al Suwaidi, grandson of one of the last traditional pearl divers in the UAE, took on the challenge of reviving the country’s pearling industry. He succeeded in establishing the Suwaidi Pearl Farm in Al Rams, Ras Al Khaimah (RAK), in 2005. Suwaidi’s cultured pearl farm is recognized as the first of its kind in the Arabian (Persian) Gulf region.
GIA’s Mumbai laboratory recently examined a quantity of cultured pearls obtained from the farm. The parcel contained variously shaped white to cream-colored pearls. Examination by real-time microradiography (RTX) showed a variety of different internal structures including bead and non-bead cultured pearls, but two pearls in particular (figure 1) revealed very interesting structures and were confirmed to be samples from atypical “bead” culturing experiments conducted by the farm. Pearl A was light cream and near-round, weighing 0.87 ct and measuring 5.13 × 4.93 mm, while pearl B was cream and button shaped, weighing 0.94 ct and measuring 5.42 × 5.12 × 4.93 mm. When viewed under 40× magnification, both pearls exhibited a smooth surface and possessed typical nacreous overlapping aragonite platelets.

Figure 2. Top: RTX images in three directions of the non-bead cultured pearl used as a “bead” with a distinct demarcation and an organic tail-like feature in pearl A. Bottom: μ-CT scans of pearl A. The tail feature is indicated by a yellow arrow.

Figure 3. Top: RTX images in three directions of a natural pearl used as a “bead” with a clear demarcation and an organic tail-like feature in pearl B. Bottom: μ-CT scans of pearl B. The tail feature is indicated by a yellow arrow.
Additional RTX and X-ray computed microtomography (μ-CT) analyses were conducted to further study the internal structures. RTX imaging of pearl A revealed a non-bead cultured pearl used as a “bead” nucleus (figure 2). A light gray core surrounded by organic-rich concentric growth structures followed by finer growth arcs was visible. An obvious demarcation with a small organic tail-like feature just below the surface overgrown with cultured nacre was also apparent. The lack of growth arcs in the nacreous layers was due to rapid growth during the culturing process (“Atypical ‘beading’ in the production of cultured pearls from Australian Pinctada maxima,” GIA Research News, February 13, 2017). Similarly, pearl B revealed a natural pearl used as a “bead” nucleus (figure 3), with a very small but clearly visible dark gray core surrounded by faint growth arcs. As with pearl A, a distinct demarcation with organic-rich areas and a small organic tail-like feature were evident just below the surface overgrown with cultured nacre. X-ray computed microtomography analysis of both samples revealed clearer images of the demarcation between the “bead” pearls used as nuclei and the cultured nacre overgrowths.
Optical X-ray fluorescence examination did not show any fluorescence in either sample. Energy-dispersive X-ray fluorescence spectrometry revealed manganese levels below detection limits and strontium levels of 1130 ppm for pearl A and 1446 ppm for pearl B. The results from both testing methods were consistent with a saltwater growth environment. The ultraviolet/visible reflectance spectra collected for both pearls showed features around 435 and 460 nm and an additional weak band at 495 nm. These features are similar to spectral observations previously recorded for natural Pinctada radiata pearls (A. Al-Alawi et al., “Saltwater cultured pearls from Pinctada radiata in Abu Dhabi (United Arab Emirates),” Journal of Gemmology, Vol. 37, No. 2, 2020, pp. 164–179). Raman analysis using 514 nm laser excitation was carried out on the surfaces of both pearls, and a doublet at 704/705 cm–1 as well as a peak at 1085 cm–1, indicative of aragonite, were observed. Weak polyenic pigment-related peaks at 1130 and 1540 cm–1 were only observed for pearl B and were associated with its cream coloration. The photoluminescence spectra were also consistent with the Raman results and displayed high fluorescence together with the aragonite peaks, typical of most nacreous pearls.
Using lower-quality pearls (both nacreous and non-nacreous), gemstones, and other materials as “bead” nuclei has been a known practice for the last decade (“Chasing cultured pearls at SSEF: Cultured pearls using a natural pearl as a bead,” 2020, https://www.ssef.ch/chasing-cultured-pearls-at-ssef-cultured-pearls-using-a-natural-pearl-as-a-bead/). Although not seen on a regular basis, atypical “bead” cultured pearls (aBCPs) are encountered in laboratories from time to time and can be very challenging to separate from some natural pearls. This would be especially true of the two samples featured in this report: If either of them were drilled and mixed in strands with natural Gulf pearls, an experienced gemologist would find it difficult to separate them from the other pearls. The authors have encountered natural pearls with similar distinct boundaries. It should also be noted that the aBCPs produced at the Suwaidi farm are the result of successful experiments, and they are not commercially available at the time of this writing. The farm continues to conduct various experiments and aims to restore the UAE’s place in the global market by producing the finest Pinctada radiata cultured pearls available. Source: GIA @topic:5


Title: Microscopic Shells in Natural Pearls from Pinctada radiata Abstract: Figure 1. Two natural pearls recovered from Pinctada radiata mollusks by Bahraini divers, weighing 0.06 ct (pearl A, left) and 0.25 ct (pearl B, right). Photo by Gaurav Bera.
For centuries, natural pearl diving was Bahrain’s main industry. The vast majority of natural pearls fished around the islands of Bahrain are found in the Pinctada radiata bivalve (known in Arabic as mahar). These pearl beds have been known to produce the finest-quality natural pearls in the Arabian (Persian) Gulf region. Given the Gulf’s strategic trading location and the richness of its pearling industry, the pearls from this region are coveted by traders and collectors alike (R. Carter, “The history and prehistory of pearling in the Persian Gulf,” Journal of the Economic and Social History of the Orient, Vol. 48, No. 2, 2005, pp. 139–209). GIA’s Mumbai laboratory recently examined a quantity of these pearls obtained from two local Bahraini divers who claimed they were recovered from wild mollusks living in the nutrient-rich shallow waters off the coast of Sitra, one of Bahrain’s 33 islands.
Natural pearls from Pinctada radiata fished from Bahrain and the Gulf region in general have a wide range of shapes and colors. While most of the pearls examined showed a variety of interesting internal structures, two of them had a noteworthy feature: a minute shell contained within. Natural pearls are very rare and form inside mollusk shells, and a shell within a pearl within a shell is like nature’s version of a nesting doll. Such structures have been encountered by GIA on rare occasion (see Winter 2015 Lab Notes, pp. 434–436).
Both pearls were very small (figure 1). The smaller one (A) had a strong yellow bodycolor and an oval shape, weighing 0.06 ct and measuring 2.07 × 1.93 mm. The larger round one (B) had a light cream color, weighing 0.25 ct and measuring 3.30 mm in diameter. When viewed under 40× magnification, both exhibited typical nacreous overlapping aragonite platelets. Real-time microradiography (RTX) and X-ray computed microtomography (μ-CT) analyses were carried out to examine the internal structures in greater detail.

Figure 2. The gastropod shell, measuring approximately 0.50 × 0.30 mm, observed in pearl A. A: RTX image of the shell. B–D: μ-CT scans of the shell in the X, Y, and Z directions, respectively. (The weak white rings on the lower right image are artifacts and not pearl-related structures.)
A minute gastropod shell measuring approximately 0.50 × 0.30 mm was observed in pearl A. The shell walls were very thin, and minimal growth arcs were present in the nacre surrounding it (figure 2). Marine gastropods are known to range in size from a few millimeters to more than a meter, so the size of the shell inside this pearl suggests it was from a juvenile gastropod just beginning to form its shell. The juvenile shell later forms the protoconch or first whorls of an adult gastropod (A. Nutzel, “Larval ecology and morphology in fossil gastropods,” Paleontology, Vol. 57, Part 3, 2014, pp. 479–503).

Figure 3. The foraminifera test, measuring approximately 0.45 × 0.35 mm, observed in pearl B. A: RTX image of the foraminifera test. B–D: μ-CT scans of the foraminifera test in the X, Y, and Z directions, respectively. (Again, the weak white rings on the lower right image are artifacts.)

Figure 4. 3D images constructed from μ-CT scans of pearl B illustrate the morphology of the foraminifera test. Images by Emiko Yazawa.
RTX imaging of pearl B revealed a minute shell that appeared to be a foraminifera test (shell), measuring approximately 0.45 × 0.35 mm. Foraminifera are small unicellular marine organisms found on the sea floor. A thin layer of organic matter that appeared darker in the RTX and μ-CT images seemed to envelop the foraminifera test, and a few growth arcs were observed within the surrounding nacre (figure 3). The μ-CT scan was also rendered using specialized software (C. Zhou et al., “New 3-D software expands GIA’s pearl identification capabilities,” GIA Research News, May 13, 2016) to create a three-dimensional image that made it easier to see the external morphology of the shell within the pearl (figure 4). The foraminifera test appeared multilocular, or multichambered, with tubular chambers arranged around a growth axis to form a beautiful milioline arrangement of chambers (A.R. Loeblich and H. Tappan, Foraminiferal Genera and Their Classification, Springer, New York, 1988). The minute size of the shells within these tiny pearls is a good indicator of their natural origin.
Energy-dispersive X-ray fluorescence spectrometry on pearls A and B revealed low manganese levels of 39.0 ppm and 17.8 ppm and high strontium levels of 1768 ppm and 1497 ppm, respectively, which is characteristic of formation in a saltwater environment. Raman analysis was also carried out using 514 nm laser excitation on the surface of each pearl. A doublet at 702 and 705 cm–1 as well as a peak at 1085 cm–1 indicative of aragonite were observed, along with minor polyenic pigment peaks at 1130 and 1530 cm–1. Photoluminescence (PL) spectra were also collected on both pearls. Pearl A revealed three broad peaks at 620, 650, and 680 nm, characteristic of many naturally colored pearls, while pearl B showed clear aragonite peaks and low fluorescence. An ultraviolet/visible reflectance spectrum was collected only for pearl B within the 220–850 nm range, as pearl A’s size prevented the detector from obtaining a clear result. Faint features at 420 and 495 nm were, like the PL results, consistent with natural coloration. Similar spectral observations have previously been documented in natural Pinctada radiata pearls (A. Al-Alawi et al., “Saltwater cultured pearls from Pinctada radiata in Abu Dhabi (United Arab Emirates),” Journal of Gemmology, Vol. 37, No. 2, 2020, pp. 164–179).
The gemological examination of these Pinctada radiata pearls proved very rewarding, especially with regard to their internal structures. Research into what causes the formation of a pearl in the wild is ongoing. Hence, finding these minute shells that may be the initiation of growth in these two natural pearls is a truly rare circumstance. Source: GIA @topic:5


Title: Update on the Identification of Dye Treatment in Yellow or “Golden” Cultured Pearls Abstract: Dye treatments in yellow or “golden” cultured pearls have improved to the point that some samples show little surface evidence. In addition to routine gemological observations, analytical techniques such as UV-Vis reflectance and Raman photoluminescence (PL) spectroscopy are critical to identifying the treatment. This study demonstrated three indications of dye treatment: broad reflectance features between 410 and 450 nm, the lack of a reflectance feature at 350 nm in the UV-Vis spectra, and intense fluorescence in the visible spectrum under 514 nm wavelength laser excitation. These diagnostic features may be used independently, even when no visual evidence of a dye exists. Source: GIA @topic:5


Title: Non-Nacreous Purple and White Pearls Reportedly from Spondylus Species Abstract: Figure 1. These three purple and white non-nacreous pearls weighing 7.85, 8.37, and 9.85 ct (left to right) are reportedly from Spondylus calcifer. Photo by Robert Weldon.

The Carlsbad laboratory recently examined three non-nacreous pearls, weighing 7.85 to 9.85 ct and measuring from 10.50 × 10.21 mm to 12.43 × 11.65 × 10.65 mm (figure 1). All three pearls exhibited similar uneven bodycolors and surface characteristics. They displayed purple and white colors with some yellowish brown tints and possessed a porcelaneous surface with mottled to clear fine flames. They were reportedly fished near Ligui, on the eastern coast of the Mexican state of Baja California Sur.

Similar surface structures have been reported in G&G (Fall 2014 Lab Notes, pp. 241–242; Winter 2015 Lab Notes, pp. 436–437; Summer 2016 Micro-World, pp. 202–203). A characteristic reflective blue coloration on the base of the 9.85 ct semi-baroque button (figure 2) was clearly visible when the flame structure was illuminated with a fiber-optic light. Moreover, subsurface to surface-reaching acicular inclusions found in most Spondylus pearls examined previously were also present in these samples. These inclusions, which appear in the form of tubes or needles, are often associated with the flame structure. At first the inclusions were believed to be parasite channels, which are sometimes observed in shells and pearls of various nacreous and non-nacreous mollusks. But after careful inspection they were seen to be part of the structure, radiating from within and reaching the surface in the same direction and with fairly consistent size and shape—whereas the parasite channels are irregularly shaped and in various sizes, running in random directions and usually crossing over each other.

Figure 2. The characteristic reflective blue coloration of Spondylus pearls was visible
within the flame structure of the semi-baroque button pearl when illuminated with a
fiber-optic light. Photomicrograph by Artitaya Homkrajae; field of view 5.77 mm.
The pearls’ dimpled surface texture appears to be caused by the slightly recessed openings where these inclusions reach the surface. This unique feature is also found on the interior of Spondylus shells in GIA’s Bangkok laboratory collection (figure 3). The resemblance between a pearl’s surface and the interior surface of its host are useful in identifying the mollusk species. Yet many marine gastropods and bivalves produce non-nacreous pearls, and their similar surface structure and color sometimes make mollusk identification challenging. As with the previously reported Spondylus pearls, microradiography of all three pearls revealed tight structures, and no obvious growth arcs were seen.

Figure 3. Subsurface to surface-reaching acicular inclusions were found on the interior of a Spondylus shell (left) from the GIA Bangkok reference collection and associated with the flame structure in a Spondylus pearl (right). Photomicrographs by Artitaya Homkrajae (left, field of view 1.31 mm) and Moqing Lin (right, field of view 2.37 mm).
The Spondylus genus (commonly known as “thorny” or “spiny” oyster) consists of about 76 living species distributed in tropical waters around the world. Spondylus princeps and Spondylus calcifer (also known as Spondylus limbatus) are two of the main species on the western coast of the Americas. S. princeps is found from the gulf side of Baja California down the Pacific coast of Mexico through Panama to northwest Peru. S. calcifer is found in the Sea of Cortez (Mexico) and Ecuador (K. Lamprell, Spiny Oysters: A Revision of the Living Spondylus Species of the World, Jean Lamprell, Brisbane, Australia, 2006). Most Spondylus pearls examined by GIA are reportedly from Spondylus princeps, whose bodycolor is typically white to cream or various saturations of pink, orange, and brown. This is the first time GIA has examined pearls with such a dominant purple hue reported to be from Spondylus calcifer. This species has been recorded as producing pearls in Costa Rica (E. Strack, Pearls, Ruhle-Diebener-Verlag GmbH & Co., Stuttgart, 2006, p. 59). Source: GIA @topic:5