Title: Finders, Keepers: Field Trip to Crater of Diamonds, USA Abstract: Figure 1. These diamonds from Crater of Diamonds State Park were mined previously by other prospectors. They range up to approximately 0.06 ct. Photo by Roy Bassoo.
There’s only one place on earth where the general public can prospect for diamonds directly from a primary kimberlite pipe: Crater of Diamonds State Park. This park is nestled among the pines, 100 miles off the interstate near the town of Murfreesboro, Arkansas. It boasts a network of scenic walking trails, picnic sites, and campsites. At its Diamond Discovery Center, visitors can learn about the local geology. Staff are also on hand to identify any minerals that are taken home, per their “finders, keepers” policy. The park is an ideal spot for a field trip. The state also hosts many other unusual igneous rocks, including carbonatite, lamprophyre, and lamproite. With this in mind, our university petrology class piled into a van to visit Arkansas and learn about mantle-derived magmas and associated volcanism. As a side quest, we wanted to try prospecting.

Figure 2. Prospecting for diamonds at the Mauney mine, now Crater of Diamonds State Park, circa 1908. Photo courtesy of the Crater of Diamonds Archives.
The park’s main attraction is diamonds, but there are also olivine, pyrope, almandine, and amethyst to be found. Most of the diamonds recovered there are small (approximately 0.20 ct or less); see figure 1. Rarely, prospectors have found stones larger than 1 carat, including the famous Uncle Sam, a whopping 40.23 ct. The park’s diamond-bearing rocks are comprised of hypabyssal olivine lamproite and phlogopite-rich tuffs and breccias, characterized by high Mg# values (atomic ratio of Mg to Fe in an igneous rock) and K2O content (E. Walker, “Petrogenesis of the Prairie Creek, Arkansas, diamondiferous olivine lamproite,” PhD thesis, University of Western Ontario, Ontario, Canada, 1991). The deposit grades between 0.01 and 1.25 carats per 100 tons (D.P. Dunn, “Xenolith mineralogy and geology of the Prairie Creek lamproite province, Arkansas,” PhD thesis, University of Texas, Austin, 2002). In the early twentieth century, when the richest material was mined, there was a brief diamond rush in the area (figure 2). After a string of ownership changes and failed business ventures, visions of a South African–style diamond district never materialized. In 1972 the state of Arkansas purchased the land and opened it to public prospecting. Since then, visitors have found more than 33,000 diamonds (www.arkansasstateparks.com).

Figure 3. A local prospector digging for diamond ore and demonstrating sieving technique. Photos courtesy of Glenn Worthington.
After a couple of days learning about the igneous rocks in the area, it was time to test our luck at treasure hunting. We gathered buckets, shovels, and sieves from park headquarters for a small rental fee and headed out to 15 hectares of routinely plowed “blue ground.” We chose a spot, shoveled soil into buckets, and carried these heavy parcels of dirt to the wash station for sieving (figure 3). The trick is to shake the sieve back and forth just beneath the water in the horizontal plane, then rotate and repeat. This motion should concentrate the heavy minerals in the center and bottom of the sieve. Then, like a master chef, the prospector flips the entire mineral concentrate upside down and examines the heavies that sink to the bottom.

Figure 4. Three of the diamonds the authors collected from Crater of Diamonds State Park (approximately 0.01–0.05 ct). Note the irregular and fragmented morphology and brown to yellow colors. Photos by Roy Bassoo.
In three hours, we found a small collection of diamonds! Granted, they were also very small in size, ranging from 0.01 to 0.05 ct (figure 4). Most prospectors at Crater of Diamonds miss stones this small, but as trained mineralogists we were attentive to small crystals. The diamonds were predominantly colorless, although a couple were yellow to brown. Their dominant morphology was octahedral with uncommon dodecahedrons and macles. Resorption pits and terraced surfaces were pervasive. The diamonds were also fragmented, likely due to the explosive nature of the diatreme crater.

Figure 5. Terraced dissolution surface textures and inclusions of rutile and diopside embedded within the diamond. The diopside inclusions are aligned along a growth band. Photomicrograph by Roy Bassoo.
Treasure in hand, we then turned to the science. Back in our lab, we ground and polished the diamonds into wafers to examine their composition and crystal interiors. Raman spectroscopy determined that inclusions of rutile and diopside were common (figure 5). N contents, measured with Fourier-transform infrared spectroscopy, ranged from trace amounts (type IIa) to 1250 ppm (type IaAB). Cathodoluminescence imagery showed blue to turquoise response colors, typical of diamonds mined from primary deposits worldwide. They also feature fascinating patterns of growth banding and resorption truncations, which indicate a complex mantle crystallization history (figure 6).

Figure 6. Cathodoluminescence image of a polished diamond wafer, showing complex banding and truncations that highlight different diamond growth conditions. Image by Roy Bassoo.
We found Crater of Diamonds to be a thoroughly enjoyable treasure hunting adventure. Our visit gave us hands-on experience with diamond-bearing igneous rocks and challenged us to imagine how diamonds formed beneath the North American craton. We have new appreciation for the back-aching labor required by the artisanal miners worldwide who are the foundation of the gem trade. Scientific understanding and trade awareness were the substance of our visit, highlighted by moments of joyful discovery. We encourage readers to put Crater of Diamonds State Park on their gemology “bucket list” to hunt for their very own American diamond. Source: GIA @topic:7


Title: Irradiated and Annealed Blue Type Ia Diamond Abstract: Figure 1. This 0.36 ct fancy deep green-blue diamond is a multi-step treated diamond. Photo by Wenqing Huang.

Many diamonds are subjected to artificial radiation, usually with subsequent annealing to create attractive colors. Most blue diamonds in the market are treated by artificial irradiation, yet irradiated blue diamonds with a multi-step treatment process are rarely seen in the lab. The National Center of Supervision and Inspection on Quality of Gold and Silver Products (Nanjing, China) recently examined such an example.

Figure 2. The DiamondView image showed a characteristic ring-like natural growth pattern. Image by Wenqing Huang.
The 0.36 ct round brilliant, graded as fancy deep green-blue (figure 1), had natural mineral inclusions under the table and a fracture near the girdle. The DiamondView image showed a ring-like natural growth pattern (figure 2). The infrared spectrum revealed the diamond was type IaAB, with absorptions at 1282 cm–1 and 1175 cm–1 (A-aggregated nitrogen and B-aggregated nitrogen, respectively); the spectrum also revealed a radiation-related peak at 1450 cm–1 (figure 3). The H1a center reflected by the 1450 cm–1 band, involving a single nitrogen atom and two equivalent carbon atoms, was formed by irradiation and annealing above 300°C for diamonds with aggregated nitrogen (type Ia) (I. Kiflawi et al., “Nitrogen interstitials in diamond,” Physical Review B, Vol. 54, No. 23, 1996, pp. 16719–16726). The UV-Vis-NIR absorption spectrum showed absorption from a GR1 defect at 741.2 nm and revealed weak absorptions from a defect of uncertain structure (594.4 nm), H3 (503.2 nm), and H4 (496.2 nm) centers (figure 4). The GR1 center, believed to be a neutral vacancy (V0) defect, is a typical radiation-induced defect; the vacancies begin to move at 500°C and the GR1 center begins to decrease until it disappears, at around 800°C (A.T. Collins, “Investigating artificially coloured diamonds,” Nature, Vol. 273, No. 5664, 1978, pp. 654–655). The 595 nm center is also a typical radiation-induced center, which appears at temperatures above 300°C after radiation (Collins et al., 1978). The presence of the H3 and H4 centers was confirmed with photoluminescence (PL) spectroscopy (figure 5). The combination of all the above defects, especially the strong H1a center, indicates that the diamond was subjected to irradiation followed by annealing.

Figure 3. The FTIR spectrum of the 0.36 ct irradiated diamond revealed the sample was type IaAB, with absorptions at 1282 cm–1 (A-aggregated nitrogen) and 1175 cm–1 (B-aggregated nitrogen). The H1a absorption at 1450 cm–1, associated with irradiation and subsequent heating, was also detected. In addition, the spectra showed peaks at 1405, 1096, and 1010 cm–1, all of which are usually seen in type Ia diamond.

Figure 4. The UV-Vis-NIR spectrum of the 0.36 ct irradiated diamond, collected at liquid nitrogen temperature, showed a clear GR1 center defect at 741.2 nm, and weak absorption lines at 594.4 nm, 503.2 nm, and 496.2 nm.

Figure 5. The PL spectrum of the sample excited with a 405 nm laser showed weak emissions at 496.2 nm (the H4 center) and 503.2 nm (the H3 center). A peak at 491.7 nm was also detected.
Natural near-colorless type Ia diamonds are known to be artificially irradiated to introduce blue to green color by displacing carbon atoms in the lattice to create vacancies. Annealing could be used to change the lattice defect configuration, especially GR1, to achieve a purer blue (C.M. Breeding, “A spectroscopic look at green and blue gem diamonds colored by artificial irradiation treatment,” presentation at Geological Society of American 2014 annual meeting). After annealing above 500°C, the vacancies start to migrate, and can be captured by nitrogen centers to create the H1a center (B. Dischler, Handbook of Spectral Lines in Diamond, Volume 1: Tables and Interpretations, Springer-Verlag, Berlin, 2012, pp. 315–316). To the best of our knowledge, this is the first diamond examined in China that has been irradiated and annealed to introduce a blue color. Source: GIA @topic:4


Title: Diamond Mining in Minas Gerais, Brazil Abstract: These diamonds were mined from the Abaeté River region in Minas Gerais, Brazil. Photo by Andy Lucas, © GIA

                      Brazilian diamonds were discovered around 1725 by gold miners along the banks of the Rio Jequitinhonha, in the state of Minas Gerais. For more than a hundred years, the country was the world’s most important diamond source, as the famous Golconda deposit in India was nearly exhausted and South African mines were yet to be discovered.

Diamond mining in Brazil continues today, though largely overshadowed by the output of other countries. But despite sporadic production, important stones continue to emerge from Brazil. The country has long fascinated me. Following many visits to colored gemstone deposits there, I took an August 2012 trip to Minas Gerais—Portuguese for “general mines.” What I saw led me to believe that the future of Brazilian diamond mining looks promising.

Brazil has several alluvial diamond sources, where stones are mined from the sands and gravels of river banks. There are also some potentially important diamond pipes that may warrant larger-scale open-pit or underground mining. Diamonds are mined in several Brazilian states, including Mato Grosso do Sul, Bahia, and Rondônia. I visited an alluvial diamond mine in Minas Gerais, which is famous for its gold and colored gemstones, as well as other commercial minerals. Owned by GAR Minerals, the mine is located near the diamond-bearing Abaeté River and the town of Três Marias. GAR Minerals has six properties along the Abaeté River and six others near the town of Coromandel on the Santo Ignacio River, also in Minas Gerais. Each property is around 2 hectares—nearly five acres—and licensed for diamond exploration.

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Coromandel is known for large stones with high clarity that are brown or colorless to near-colorless. The brown stones can be turned colorless by a high-pressure, high-temperature (HPHT) enhancement process. The GAR mines along the Abaeté River mostly contain smaller diamonds, but they have produced some large top-quality pinks.

Important stones GAR has mined in Coromandel include a 263 ct rough diamond that yielded two 70 ct pear shapes, both H color. Coromandel also produced a 140 ct rough that yielded a 10 ct E-color and a 56 ct H-color diamond, both with high clarity. Although the Abaeté River is the better-known source for pink diamonds, Coromandel has also produced some specimens, including a 21 ct Fancy Intense pink rough crystal.

At the Abaeté River, GAR has recovered a 26 ct crystal that yielded a 12.60 ct Fancy Intense purplish pink cushion shape. The company also found a 7 ct rough diamond that produced a 4.24 ct Vivid pink. Colorless stones from these mines weigh 10 ct or less. It is believed that the Abaeté River has supplied some of the most important pink to red diamonds to come on the market in the last 50 years.

The entire length of the river, where GAR Minerals’ properties stretch approximately 40 km along the bank, has considerable diamond potential. GAR is a fourth-generation family-owned business. Company officials anticipate their Abaeté River properties will remain productive for at least another two generations.

I visited a GAR mine near the Abaeté on a working farm owned by the family. Getting there from the town of Três Marias required driving on a dirt road and then crossing a swaying suspension bridge on foot. Like other GAR properties, it is an alluvial deposit with diamond-bearing gravel. This entails small open-pit operations in which excavators remove the gravel all the way down to bedrock and load it into trucks for careful examination. Because diamonds are denser than most other materials in the gravel, depressions indicate where valuable concentrations might be found. Once an area is mined down to the bedrock, operations continue by following the alluvial gravel along the riverbed.

Trucks then haul the diamond-bearing gravel to a processing (or washing) plant, where diamonds are separated from the gravels and other minerals, often referred to as overburden. The processing plant uses a feeder to bring the gravel into an automated system. There it is washed with a water cannon before separation. A vibrating screen then removes coarse material, and sluices transport the remaining gravel to a worker who washes it by hand while a sorter sifts through the material looking for the occasional diamond.

In an effort to restore areas damaged by open-pit mining, GAR has implemented a formal plan to refill the pits, while following guidelines set forth by an environmental impact study. Source: GIA @topic:1


Title: GIA Researchers Evaluate ‘Light Performance’ and Diamond Cut Abstract: The GIA Cut Grades represented in these diamonds (from left, Poor, Good and Excellent) reflect how people see them. Any evaluation of cut quality should reflect what the eye sees. The term “Light Performance” has different connotations in the trade and is not used by GIA to describe diamonds. Kevin Schumacher/GIA

The phrase “light performance” gets a lot of loose use in the diamond trade. Terms such as brightness, brilliance, fire and scintillation are defined by various organizations with both clear and vague descriptions. The correlation of any of these properties to a diamond’s proportions are rather broad, while specific claims of better appearance are made for narrow ranges of proportions (particularly the “Ideal” cut for round brilliants).
Major deficiencies in a round brilliant’s appearance produced by extreme proportions have been understood for a century. Phenomena such as a fish-eye, dark center or dark mains that extend to the stone’s edge, produced, respectively, a too shallow pavilion, a too deep pavilion or a mismatch between crown height and pavilion depth. The discussion for more than 75 years has been focused on “proving” which proportions offer the best appearance.
But does “light performance” have an agreed-upon meaning? Just what does it mean?
In regard to diamond appearance, many would assume that high light performance means all observers will love the diamond. But how much of a part has human observation played in the development of any system for evaluating light performance in polished diamonds? In particular, do observers visually value the properties that are used in various approaches to exploring light performance?

This diamond has a well-distributed contrast of light and dark areas, forming a pattern that “performs” well while rocking and tilting. This dynamic aspect of light performance ‒ where the pattern itself changes as the diamond moves, yet continues with a good distribution of the pattern elements and resulting brightness ‒ is an important part of what the eye sees and its perception should be part of an evaluation of light performance. The angles and proportions of facets used to cut this diamond have been well known for decades to create diamonds that are attractive to most observers. Video by Nicole Phelan/GIA
How is light performance evaluated?
The most widely discussed method for evaluating light performance in recent decades uses a colored dome or cylindrical viewer, some with layers of colors. The colored dome or cylindrical viewer is used either as part of a device for viewing a diamond, or employed in a computer model with the 3D measurement (wireframe) of a diamond as input. This approach yields an image whose colored pattern reveals how the light that exits face-up and perpendicular to the table relates to the angles at which light enters the diamond. The pattern depends on both the proportions and symmetry of the diamond. It does not measure the amount of light exiting the diamond’s crown, and many implementations exclude specific evaluation of either fire or scintillation. There are various criteria for how much pattern difference is permitted within each grade range. Some users of this method include tilting the diamond, while others use only the face-up perpendicular position.
In all its variations, this approach assumes that the chosen standard addresses all issues regarding the balance of brightness, fire, contrast pattern and sparkle that are desirable in a diamond. None of the users of this approach have reported on human observations to verify that their conclusions make visual sense.
Another method uses an imaging spectrophotometer to obtain five images of the diamond at different distances from the light source. These images are analyzed for the amount of bright white light (described as brightness), colored light (described as fire) and differences among them (described as scintillation). This approach yields a measure of light exiting the diamond’s crown, but quantitative results are not presented. Instead, the three analyzed values are displayed on bar graphs relative to a database of thousands of previously measured diamonds of the same shape. The device does not permit tilting of the diamond relative to either the light source or detector. The question looms again, were any human observations conducted to verify that the three output values correlate to what people see?

This diamond has a very poor distribution of light and dark areas, forming a pattern that most find very unattractive. It also “performs” poorly while rocking and tilting. The strong, heavy “spokes” radiating from the center, surrounded at the outer edge by darkness, does not improve when tilted and the pattern itself hardly changes as the diamond moves. Large areas of concentrated darkness or dullness are a result of steeper crown and pavilion angles that the trade has avoided since they know those angles will create a poor looking diamond. Video by Nicole Phelan/GIA
Other factors that affect light performance
Some of the light performance information out there is very questionable. Polished diamonds return less than half the light energy that enters them, not “most” of it. Brighter does not indicate better appearance, because brightness is different than brilliance — both a mirror and a sheet of white paper return a lot of light, but neither is brilliant.
Human perception of brilliance requires a well-distributed contrast of light and dark areas. A diamond with good contrast and somewhat lower light return can look better than one with high light return and little contrast. Additionally, the diamond should also “perform” well while rocking and tilting (the dynamic aspect of light performance). The change in contrast and brightness is an important part of what the eye sees and should be part of an evaluation of light performance.
Personal taste is an important factor of perceived light performance. During our observation experiments, GIA found broad agreement on the displeasing aspects of diamond appearance, such as large areas of darkness, but noteworthy disagreement on what is most pleasing. Focusing on a particular diamond appearance, such as Hearts & Arrows, to the exclusion of all others leaves little room for personal preference. Of course, GIA feels that information provided to a third party needs to be thorough and not just focused on one aspect of a diamond.
Note that light performance in many other systems does not include the impact of other important factors that provide comprehensive information about a diamond. Weight ratio (e.g. thick girdles), durability (risk for chipping) and craftsmanship (which includes symmetry and polish quality) are also very important criteria that should not be ignored in evaluating cut.
Coming back to the original question: what does light performance really mean? Since diamonds are something we wear to show to others, the answer should be tied a diamond’s visual appeal. Physics may say that a certain diamond under specific conditions returns more light than another, or has more fire than another, but do you and I see these things? Light performance should mean that computer modeling, instrumentation or any other methods that claim to evaluate a certain diamond and assign a value or a grade should be linked to what we actually see.
GIA continues to avoid the use of the term “light performance” because of the ambiguity with which the trade uses it. Source: GIA @topic:4


Title: Fish-Like Inclusion in Fancy Yellow Abstract: This pavilion view of the 4.76 × 4.30 × 2.75 mm Fancy yellow diamond displays the “fish” inclusion scene. The fish appears to be facing to the right. Magnified 40×. Photo by Martha Altobelli.

It is always a pleasant surprise to find a new and interesting inclusion during routine observation. But an inclusion that reminds us of a particular shape, an effect known as pareidolia (Winter 2007 Lab Notes, pp. 363–364), is a geologic wonder.
The New York laboratory recently received a natural yellow (graded as Fancy yellow) “Cape” 0.51 ct rectangular faceted diamond exhibiting such a feature. Examination of the stone revealed a series of table-reaching fractures and clouds that seemed to form the outline and scale-like detail of a fish (pictured at top). The inclusion is large in relation to the stone, encompassing nearly 75% of the table.
Nearly all fractures in diamond result from the interaction among multiple cleavage directions (The MicroWorld of Diamonds, Gemworld International, 2000, p. 97). While often detrimental to the value of a stone, this inclusion serves as a useful identifier, and such findings help keep the study of gems enjoyable. Source: GIA @topic:4


Title: Optical Defects in Diamond: A Quick Reference Chart Abstract: ABSTRACT
Gem diamonds owe much of their value to their color, or lack thereof. Defects in the atomic structure of diamond are responsible for this color and are important for the identification of color treatments. This article and its tables are intended as a quick reference for gemologists as they read about various common diamond defects in the gemological literature.
INTRODUCTION
Despite the commercial value of natural-color diamonds, distinguishing them from treated diamonds remains a significant identification challenge. While some diagnostic visual features exist (inclusions, color or growth zoning, and absorption bands seen with a spectroscope), the separation of natural from synthetic or treated diamonds is not always possible using standard gemological methods. In such cases, advanced spectroscopic analysis at a professional gem-testing laboratory is required. Imaging of luminescence distribution patterns is also a helpful tool for recognizing synthetic diamonds (Martineau et al., 2004; Shigley et al., 2004).

In a laboratory setting, the identification of diamonds is based mainly on the detection of tiny imperfections in the atomic lattice. These “defect centers” may include foreign impurity atoms (typically nitrogen, and occasionally boron or hydrogen); carbon atom vacancies in the lattice (either single or clusters of neighboring vacancies); carbon atoms positioned in between normal lattice locations (interstitials); and dislocations where planes of carbon atoms are offset from one another due to plastic deformation. Not all of these lattice imperfections create spectroscopic features, but several do so by allowing the diamond to absorb particular energies of incident light or radiation. Defects can occur randomly or in particular locations within the lattice. Diamonds can contain more than one type of defect, and in natural diamonds, defects can be altered over geologic time in the earth or by exposure to heat or radiation during color treatment.

So-called optical defects (or optical centers) cause absorption in the visible or near-visible portions of the electromagnetic spectrum, often producing coloration (e.g., figure 1). Luminescence reactions result when defects absorb higher-energy incident radiation and then reemit lower-energy radiation as visible light. Optical defects occur in very low concentrations in all diamonds, and their presence can be detected using spectroscopic techniques. A theoretically “pure and perfect” diamond containing no such defects would appear colorless.

Figure 1. The red color of the graining in this Fancy red diamond from Brazil is caused by absorption related to the 550 nm band. This band, the most common cause of pink to red color in natural, untreated diamonds, is thought to be the result of a defect created by plastic deformation. Photomicrograph by Jian Xin (Jae) Liao; magnified 50×.
As a quick reference for gemologists, table 1 lists the most common lattice defects, including those that can create color and/or luminescence reactions in diamond. The scientific name of the defect, as well as the wavelength (or wavenumber) and electron volt (eV) positions of the main and associated spectral bands, are shown along with photos of representative diamonds. The most common spectroscopic technique used to detect the defect center is indicated by a code shown in italics.

Download a Larger Version of this Optical Defects Chart

Table 1. Important optical defects in diamond and their effect on color and luminescence.
Some precautions should be kept in mind when using this table. Each lattice defect is known to produce a particular diamond color or luminescence. For instance, the GR1 center produces green or blue-green color. But the reverse is not necessarily true—for example, not all green diamonds owe their color to the GR1 center. In fact, there are several causes of green color. In some cases, a diamond contains more than one optical defect, and its color stems from a combination of defects. In other cases, a diamond’s color may arise from absorption caused by one optical center, while its luminescence may result from another optical center.

Table 2 provides a comparison of the most common spectroscopic techniques for diamond characterization. For further reading on color in diamond, the Additional Reading list serves as a reference guide to access the much larger range of gemological and technical literature on diamond identification. Source: GIA @topic:4


Title: CVD Synthetic Diamond with Unusual DiamondView Image Abstract: Figure 1. This G-color, 0.32 ct CVD-grown synthetic showed DiamondView features typically associated with a natural origin. Photo by Robison McMurtry.

Over the last several years, CVD-grown synthetic diamonds have evolved rapidly in overall quality, including size and clarity. GIA’s laboratory frequently documents new, sometimes subtle developments in this material.

Recently a 0.32 ct, G-color CVD synthetic (figure 1) was submitted to the Carlsbad laboratory. DiamondView imaging (figure 2) showed a few interesting characteristics. Most of the sample displayed a deep blue fluorescence, a feature typically derived from the N3 optical center and often observed in natural diamonds. CVD-grown synthetic diamonds usually have either a greenish blue or an orange to red fluorescence, depending on whether they have been treated to generate high concentrations of NV centers. The deep blue, N3-related fluorescence is so prevalent among mined diamonds that the color itself can often verify that a diamond is not synthetic. In addition to the deep blue color of the fluorescence, its visual pattern closely resembled the dislocation networks commonly seen in natural-origin type IIa diamonds rather than the striations caused by stepwise growth in CVD synthetics (P.M. Martineau et al., “Identification of synthetic diamond grown using chemical vapor deposition [CVD],” Spring 2004 G&G, pp. 2–25).

Figure 2. In addition to blue fluorescence, the CVD synthetic’s DiamondView image displayed yellow-green fluorescence lines indicating the stop/start cycling that occurred during the growth process. Image by Sally Eaton-Magaña.
Taken together, the blue fluorescence and apparently random patterning closely resemble DiamondView images of natural-origin type IIa diamonds. This indicates that CVD manufacturers are becoming quite adept at mimicking natural growth. It is unclear whether this resemblance was a deliberate goal or a by-product of advances in CVD growth; regardless, the blue fluorescence for this CVD synthetic diamond does not appear to derive from the N3 center. Photoluminescence (PL) spectroscopy, collected with 325 nm excitation, showed only a very weak peak at 415.2 nm.

Yet this stone also contained two features that clearly indicated its synthetic origin: a large concentration of the Si-V center at 737 nm, revealed by PL spectroscopy, and the pronounced yellow-green parallel lines in the DiamondView image.

These parallel lines, with a nearly uniform spacing of approximately 0.8 mm in this sample, are created when the CVD reactor undergoes stop and start cycles during growth. These cycles create a temporary change in chemical composition, especially at the growth interface. Willems et al. (“Exploring the origin and nature of luminescent regions in CVD synthetic diamond,” Fall 2011 G&G, pp. 202–207) proposed that a change in surface roughness promotes the incorporation of impurities, which alters the fluorescence and creates new dislocations.

Four PL spectra were collected from these yellow-green lines and from the blue-fluorescing regions, using 488 nm laser excitation and normalized to the Raman peaks. The relative intensities of the peak areas from both regions were averaged to compare the optical defects that altered the fluorescence. The H3 center at 503.2 nm, the NV centers at 575 and 637 nm, and the Si-V center at 737 nm all showed higher concentrations along the yellow-green lines. These vacancy-related defects increased by a factor of approximately 1.5 for NV0 and Si-V, 3 for NV–, and 5 for H3, indicating a higher presence of vacancies at the growth interface. Several sequential growth runs were likely necessary to achieve high CVD quality, leaving behind these fluorescence lines as evidence of synthetic origin. Source: GIA @topic:4


Title: Rough Diamond Fragment with a Large Green Cleavage Surface Abstract: This 2.02 ct rough diamond displays prominent green coloration along an internal cleavage surface. Such coloration is thought to result from the presence of a natural radioactive solution within the cleavage. Photo by James Shigley.

A colorless 2.02 ct flattened diamond crystal fragment (see above), from Mr. Rowan Beach of San Francisco, was examined at GIA’s Carlsbad lab. The fragment exhibited a large bluish green internal surface that was readily visible without magnification. Initially thought to be a colorful mineral inclusion, it proved to be a radiation-induced coloration along the internal surface. When a diamond is irradiated (during laboratory color treatment or occasionally in nature), carbon atoms are removed from their normal position in the diamond lattice; this creates what scientists call the “GR1” optical defect (i.e., a vacant atom position in the lattice). The presence of this defect causes the diamond to selectively absorb light toward the red end of the visible spectrum, while the remaining portions are transmitted through the diamond and, when recombined, seen as a green or bluish green color. The GR1 optical defect can be removed in the lab by heating the diamond to over 600°C; this heating changes the green color to yellowish brown. The added energy allows a carbon atom to again occupy the vacant lattice position.

Green or bluish green color in diamonds is most often the result of exposure to a source of radiation in a geologic environment near the earth’s surface. The source of exposure could be a nearby grain of a radioactive mineral that gives rise to a small “radiation spot” on the outer surface. Conversely, the source could be a radioactive solution that was able to penetrate surface-reaching cleavages in the diamond. In both cases, the source produced alpha-particle radiation, which has a limited penetrating distance in diamond. As a result, the radiation spot or stain is confined to a zone close to the radioactive material. Such radiation stains are not uncommon in diamonds, though they are often removed by the faceting process.

The presence of a large green internal radiation stain indicates that this diamond was irradiated in a near-surface geological environment where temperatures high enough to modify the GR1 were unlikely. This means that the irradiation took place in the crust after the diamond was transported up from the mantle by the kimberlite magma eruption. Although the geographic origin of this rough diamond is uncertain, it is one of the more intriguing examples of a natural “radiation-stained” diamond we have seen. Source: GIA @topic:4


Title: Irradiated Green-Blue CVD Synthetic Diamonds Abstract: Figure 1. These intensely colored CVD synthetic diamonds, weighing 0.64 ct (left) and 0.43 ct (right), are color graded as Fancy Deep green-blue and Fancy Deep greenish blue, respectively. Photo by Sood Oil (Judy) Chia.

As-grown CVD synthetic diamonds are routinely treated in order to create attractive colors. Irradiated CVD synthetic diamonds without a multi-step treatment process are rarely seen in the lab, though an irradiated Fancy Deep gray-blue CVD synthetic has been reported (Fall 2014 Lab Notes, pp. 240–241). The New York lab recently examined two such examples: a 0.64 ct Fancy Deep green-blue and a 0.43 ct Fancy Deep greenish blue specimen (figure 1).

Figure 2. DiamondView images reveal linear striations in the pavilions of the 0.64 ct (left) and 0.43 ct (middle) specimens. A face-up image of the 0.43 ct synthetic shows a yellowish green zone of growth interruption (right). Images by Kyaw Soe Moe.
Dark inclusions, faint color bands, and chips on the girdle were observed in both specimens under the microscope. Tatami-like strain was also seen in both diamonds under cross-polarized light. DiamondView images revealed parallel green linear striations in the pavilions (figure 2). Face-up DiamondView images also showed yellowish green zones, which were formed by growth interruptions (again, see figure 2). Both stones were pure type IIa diamonds with no other defects in the IR spectra. High-resolution UV-Vis-NIR absorption spectra detected Si-V center defects at the 736.5–736.9 doublet (737 nm center, (V-Si-V)–); the spectra also revealed radiation-related peaks at 393.5, 464.3, 469.9, 594.2, 666.5, 735.8, and 741.2 nm (figure 3). The 393.5 band is from the ND1 center, a negatively charged vacancy (V–). An intrinsic radiation center (TR12) was detected at 469.9 nm. The TR13 center at the 464.3 peak is a local vibrational mode associated with the TR12 center, and the 594.2 band (595 nm center) is a typical radiation-induced center. The 666.5 peak is attributed to a neutral self-interstitial (I0) defect. The 735.8 band, also caused by the I0 defect, is related to the 666.5 band. Strong absorption from the GR1 center, which contains neutral vacancies (V0), was detected at 741.2 nm. All these radiation-related peaks can be destroyed by HPHT treatment, while peaks at 666.5 and 735.8 nm can be annealed out at temperatures ranging from 420º to 540ºC (see A.T. Collins, “Spectroscopy of defects and transition metals in diamond,” Diamond and Related Materials, Vol. 9, Nos. 3–6, 2000, pp. 417–423). The presence of these peaks indicates that these CVD synthetics were either annealed at lower temperatures (420º to 540ºC) or irradiated without annealing.

Figure 3. Absorption spectra of the two green-blue CVD synthetics at liquid nitrogen
temperature revealed radiation-related peaks. The peaks at 666.5 and 735.8 (both neutral
self-interstitial defects) indicate that these samples were annealed at lower temperatures
or irradiated without annealing. The Si-V center defect (737.0 nm center) can also be
observed at the 736.5–736.9 nm doublet. Many unknown absorption bands (unlabeled
in this spectra) are also detected.
Although microscopic features such as strain pattern can be helpful in the identification of CVD synthetics, they are not conclusive. DiamondView imaging is very useful for this purpose due to its ability to detect linear striations. As CVD growth techniques continue to improve, we anticipate that intensely colored, high-quality CVD synthetic diamonds will become more prevalent in the trade. Source: GIA @topic:4


Title: Graphite Inclusions Forming Octahedral Outline in Diamond Abstract: Figure 1. This 1.30 ct Fancy brownish greenish yellow diamond contains an octahedral-shaped inclusion. Photo by Jian Xin (Jae) Liao.

Primary diamond deposits are usually found in mantle-derived igneous rocks, with the principal hosts being kimberlite and lamproite. During the ascent to the earth’s surface, diamonds may be converted, partially or entirely, to graphite and chemically dispersed and eliminated (A.A. Snelling, “Diamonds – Evidence of explosive geological processes,” Creation, Vol. 16, No. 1, 1993, pp. 42–45). GIA’s New York laboratory recently received a 1.30 ct Fancy brownish greenish yellow diamond (figure 1) containing an octahedral-shaped inclusion outlined by minute crystal inclusions along the junctions of the crystal faces.

Gemological examination at 60× magnification reveals that the octahedral-shaped inclusion is outlined by numerous irregular dark crystals (figure 2). Advanced gemological analysis with UV-Vis and FTIR spectroscopy confirmed that this was a natural diamond with a natural color origin.

Figure 2. Minute graphite inclusions outline the octahedral crystal faces in this diamond.
Photo by Yixin (Jessie) Zhou; field of view 7.19 mm.
Further analysis using Raman spectroscopy reveals that the dark inclusions are graphite crystals with a Raman peak at 1590 cm–1 (figure 3), which corresponds to the graphite G band (I. Childres et al., “Raman spectroscopy of graphene and related materials,” in J.I. Jang, Ed., New Developments in Photon and Materials Research, Nova Science Publications, 2013). Since this G band is at a slightly higher energy level than that from the primary graphite, which usually peaks at around 1580 cm–1, we propose that the crystals tested are likely the secondary graphite converted from part of the original diamond into graphite form during the specific growth episode when oxidized fluids rich in CO2 and H2O passed through diamond bearing horizons. This also explains the shift of the G band to a higher energy, due to the higher strain near these newly formed secondary graphite crystals (J. Hodkiewitcz, “Characterizing graphene with Raman spectroscopy,” Application Note: 51946, Thermo Fisher Scientific, Madison, Wisconsin, 2010). Late formation of additional diamond layers on top of the graphites would have converted them to covered internal features within the larger diamond (R.H. Mitchell, Kimberlites and Lamproites: Primary Sources of Diamond, Geoscience Canada Reprint Series 6, Vol. 18, No. 1, 1991, pp. 1–16). Primary graphite crystals could also mix into the crystal clouds during the diamond’s growth due to changes in environmental temperature, pressure, and the growth fluid’s chemical elements. These minute graphite crystals would tend to form along the junctions of crystal faces, since they usually have a higher surface energy. Thus, we believe that both primary and secondary graphite formation, occurring between the diamond’s growth episodes, contributed to this phenomenal octahedral outline.

Figure 3. The graphite G band at 1590 cm–1 is found on the minute crystals along the
crystal junctions, confirming that they are graphite crystals.
Graphite inclusions are commonly seen in diamonds as isolated crystals or jointed crystal clouds. It is very unusual to see these minute graphite inclusions formed at the junctions of the original diamond crystal faces and outlining the octahedral growth pattern. This stone not only captures the amount of stress and extreme conditions under which the diamond grew, but also shows the beauty of the formation of crystalline diamond. Source: GIA @topic:4


Title: Large Blue and Colorless HPHT Synthetic Diamonds Abstract: Figure 1. The largest blue HPHT synthetic diamonds to date: a 5.26 ct heart shape and a 5.27 ct emerald cut. Both were graded as Fancy Deep blue. Photo by Johnny Leung.

The technology for producing gem-quality synthetic diamonds is making rapid progress. In May 2016, GIA’s Hong Kong laboratory examined five large HPHT synthetic diamonds grown by New Diamond Technology (NDT) in St. Petersburg, Russia (table 1). Examination confirmed that all of them had the known characteristics of HPHT synthesis.

Two of the synthetic diamonds were color graded as Fancy Deep blue (figure 1). The 5.26 ct heart shape and the 5.27 ct emerald cut both surpassed the previous record for largest blue HPHT synthetic, a 5.02 ct specimen reported very recently. Infrared absorption spectroscopy showed that both were type IIb, with strong absorption bands from boron impurity. We observed the typical color banding of HPHT synthetics, with more blue color concentrated in the {111} growth sector. Photoluminescence analysis at liquid nitrogen temperature with various laser excitations revealed no impurity-related emissions, indicating these stones were surprisingly pure in composition and lacking in defects.

Figure 2. The emerald cut on the left is the largest colorless HPHT synthetic diamond ever reported (10.02 ct, E color). The other two, a 5.06 ct round and a 5.05 heart, both had D color. Photo by Johnny Leung.
The other three samples were colorless (figure 2). The largest one was a 10.02 ct emerald cut with E color equivalent. This stone was previously reported in 2015. The round cut weighed 5.06 ct and the heart shape 5.05 ct; both were graded as D color equivalent. Infrared absorption spectroscopy confirmed these three were type IIa diamond, but with a very weak boron-related absorption band at ~2800 cm–1. Photoluminescence spectroscopy revealed very weak emissions from the [Si-V]– doublet at 737 nm, the Nii+ doublet at 884 nm, and NV0 at 575 nm.

For all five samples, multiple growth sectors were observed in DiamondView fluorescence images, showing features similar to other HPHT synthetic diamonds. Strong blue phosphorescence was also detected. Unlike natural type IIa or IIb diamonds, they showed no dislocation or strain when examined under a cross-polarized microscope, a strong indication of high-quality crystallization. Their clarity ranged from VS2 to VVS2, attributed to a few tiny metallic inclusions trapped during diamond growth. No fractures were observed. All of these gemological and spectroscopic features are consistent with typical HPHT synthetic diamonds. This material can be accurately identified with GIA’s existing protocols for analysis.

In addition to their size, these five HPHT synthetic diamonds displayed gemological features comparable to those of top-quality natural diamonds, when graded using the system for natural diamonds. This group of laboratory-grown diamonds demonstrated the quality and size HPHT growth technology has achieved. It is obvious that more and more high-quality HPHT synthetic diamonds, including those with significant size, will be introduced to the jewelry industry. GIA’s decades of research into both HPHT and CVD synthetic diamonds allows for the ready identification of these synthetic diamonds.

TABLE 1. Large HPHT synthetic diamonds recently examined by GIA.

Sample
Weight (ct)
Cut
Color (ct)
Clarity

1
5.26
Heart
Fancy Deep blue
VVS2

2
5.27
Emerald
Fancy Deep blue
VS1

3
10.02
Emerald
E
VS1

4
5.06
Round
D
VS2

5
5.05
Heart
D
VS2 Source: GIA @topic:4


Title: Blue HPHT Synthetic Diamond Over 10 Carats Abstract: Figure 1. This 10.08 ct (13.54 × 11.39 × 7.36 mm) HPHT-grown diamond, with color equivalent to Fancy Deep blue, was the largest HPHT synthetic to date. Photo by Johnny Leung.

	In September 2016, GIA’s Hong Kong laboratory tested a 10.08 ct blue synthetic diamond grown by the high-pressure, high-temperature (HPHT) method. This was the largest HPHT synthetic diamond recorded to date. It was also the largest HPHT blue synthetic diamond GIA has examined, surpassing a 5.27 ct sample examined by the Hong Kong lab in May 2016 (see more on the two previous record holders). The manufacturer of all three stones is New Diamond Technology (NDT) in St. Petersburg, Russia.

	The 10.08 ct emerald cut measured 13.54 × 11.39 × 7.36 mm and had a color grade equivalent to Fancy Deep blue (figure 1). The client submitted the stone for scientific examination and disclosed that it was a synthetic diamond. Magnification revealed very weak color zoning with a banded structure. A few very small metallic inclusions and fractures were observed, resulting in a clarity grade equivalent to SI1. Microscopic examination with crossed polarizers showed no detectable strain, indicating a very low density of dislocations. Fluorescence images collected using the DiamondView revealed the distinctive “hourglass” growth pattern, which are significant in revealing HPHT growth. Strong blue phosphorescence, another indicator, was also detected. These images were dominated by the {111} growth sector, which had much stronger blue fluorescence. The {100} growth sector with very weak fluorescence was much smaller, indicating this synthetic diamond was produced with dominant octahedral growth. It also exhibited a strong red-orange fluorescence to long-wave UV radiation and a yellow fluorescence to short-wave UV (figure 2), both of which are uncommon.

	Figure 2. The blue synthetic diamond showed strong red-orange fluorescence to long-wave UV radiation and yellow fluorescence to short-wave UV. Photos by Johnny Leung.

	Infrared absorption spectroscopy confirmed this was a type IIb diamond, with a strong absorption band at ~2800 cm–1 in its infrared absorption spectrum attributed to boron impurity. Photoluminescence analysis was conducted at liquid nitrogen temperature with varying laser excitations showed it was surprisingly pure, with no detectable impurity-related emissions.

	Based on these gemological and spectroscopic features, we concluded that this sample was an HPHT synthetic diamond. This offered another indication of the rapid progress in HPHT synthetic technology, which offers an option for the diamond jewelry industry as well as many promising industrial and research applications. NDT also plans to offer large colorless and blue HPHT-grown diamonds made from unique donor carbon “DNA,” such as car leather and wood trim that have been turned into ultra-clean graphite. With standard protocols in place at GIA laboratories, every type of synthetic diamond on the market can be confidently identified. Source: GIA @topic:4


Title: HPHT Synthetic Diamond with Intense Green Color Abstract: Figure 1. This 0.42 ct green HPHT synthetic diamond displayed strong growth sectors that were observed without magnification. Photo by Jian Xin (Jae) Liao.

HPHT-grown synthetic diamonds are predominantly colorless, yellow, and blue, depending on the control of impurities during growth. Other colors are very rare. In this study, we report on an intensely colored green HPHT synthetic diamond identified in the New York laboratory.

This square-cut synthetic diamond, which weighed 0.42 ct and measured 4.42 × 4.34 mm with a depth of 2.59 mm, was graded as Fancy Deep green (figure 1). Initial observation revealed strong color zoning with narrow, colorless growth sectors on the pavilion that were visible without magnification. An abundance of small metallic inclusions observed under magnification (figure 2) caused the sample to exhibit magnetism. Magnetism is a common but not diagnostic feature in HPHT synthetic diamonds. Natural diamonds may also exhibit magnetism, though only in extremely rare cases (G.R. Rossman and J.L. Kirschvink, “Magnetic properties of gem-quality synthetic diamonds,” Fall 1984 G&G, pp. 163–166).

Figure 2. The green synthetic diamond displayed strong magnetism, caused by abundant metallic inclusions. Photo by Paul Johnson; field of view ~1.4 mm.
Upon further examination, the diamond was determined to be type IIb (containing the impurity boron), as seen from its mid-FTIR absorption spectrum (figure 3). The concentration of uncompensated boron in this diamond was 0.013 ± 0.003 ppma. This amount, though detectable, did not contribute to the green color. Many synthetic diamonds grown by New Diamond Technology (NDT) in Russia reportedly also contain this level of boron impurity, as it is incorporated during the growth process (B. Deljanin et al., “NDT breaking the 10 carat barrier,” Contributions to Gemology, No. 15, 2015). DiamondView imaging revealed the typical hourglass growth structure of HPHT synthetic diamonds (figure 4), along with extremely strong phosphorescence for which the presence of boron might be responsible. Noted in the FTIR spectrum was an absorption feature related to nitrogen impurity, a relatively strong peak at 1332 cm–1 caused by N+. It is unusual to see such features in today’s synthetic diamonds. A UV-Vis-NIR absorption spectrum showed strong nickel-related absorption, with a band observed at ~685 nm (figure 5). This center, due to a Ni+ interstitial vacancy, creates a “transparent” window at approximately 555–585 nm, resulting in an observed green color. This diamond was most likely HPHT treated post-growth to activate the Ni+ and cause this intense absorption. It is very rare to see HPHT synthetic diamond with an intense green color attributed to a nickel-related impurity.

Figure 3. The green synthetic diamond’s mid-FTIR spectrum, which determined
that the material was type IIb, showed an uncompensated boron concentration at
~0.013 ppma.

Figure 4. An oriented DiamondView image (left) and 633 and 785 nm PL maps (right) show the SiV– and Ni+ defects confined to the {111} growth sectors. Images by Paul Johnson.

Figure 5. The HPHT synthetic diamond’s UV-Vis-NIR spectrum displayed a very intense
Ni-related absorption.
In addition to boron and nickel, this synthetic diamond also contained the SiV– impurity in its crystal lattice. Recent studies have shown that while this impurity is common in CVD-grown diamonds, it may also be observed in HPHT-grown diamonds (U.F.S. D’Haenens-Johansson et al., “Near-colorless HPHT synthetic diamonds from AOTC Group,” Spring 2014 G&G, pp. 30–45). The distribution of Si and Ni impurities were mapped using Raman mapping techniques, and the results proved consistent with previous studies of near- colorless HPHT-grown diamonds also observed in the trade (P. Johnson et al., “Discovery and distribution of the [Si-V]- defect in HPHT-grown gem-quality diamonds,” 2015 GSA Annual Meeting, paper No. 300-12), with both the Ni+ and SiV– confined to the {111} growth sectors. Typically observed in HPHT-grown diamonds, these {111} sectors are the most developed and dominate the diamond crystal’s morphology. The SiV– center does not contribute to the color of these synthetic diamonds, and it is either intentionally or unintentionally incorporated during crystal growth (again, see figure 4).

These spectroscopic and gemological features, with the exception of the green color resulting from nickel, were consistent with typical HPHT synthetic diamond. This is the first instance in which nickel has been reported to contribute to the deep green color of a synthetic diamond. This finding could indicate a new development in growth technology and a new material making its way into the diamond trade. This example was submitted as an undisclosed synthetic diamond and was subsequently issued an identification report.

Developments in synthetic diamond growth technologies (both CVD and HPHT) continue to emphasize the need for careful observation and testing techniques to identify the new types of materials encountered in the gem trade today. Source: GIA @topic:4


Title: Christmas Tree–Shaped Internal Feature In Diamond Abstract: Left: A 3.32 ct fancy-color diamond hosts a laser manufacturing remnant of unusual shape; here, it is seen with diffused fiber-optic illumination. Right: Rheinberg illumination accentuates the LMR’s resemblance to an evergreen tree. Photomicrographs by Jonathan Muyal; field of view 2.90 mm.
A 3.32 ct Fancy yellow marquise diamond recently submitted to GIA’s Carlsbad laboratory for color origin determination was of particular interest for its large, eye-visible laser manufacturing remnant (LMR). This LMR extended along a relatively straight path from a star facet through the pavilion and featured lily pad stress fractures stacked in parallel along its length, a composition reminiscent of a Christmas tree preserved within the diamond. With its resulting “green foliage” against a dark blue night, the use of Rheinberg color contrast illumination technique (N. Renfro,“Digital photomicrography for gemologists,” Summer 2015 G&G, pp. 144–159; Fall 2015 Micro-World, pp. 328–329) dramatically accentuated this already evocative scene (see above).

Unlike the remnants of laser drilling used to remove small inclusions, LMRs are an unintended consequence of either carelessness or unpredictable laser optics. As such, they are graded as clarity characteristics that can reduce the overall quality and value of a diamond. LMRs can occur during the laser cutting of a diamond. They appear in a variety of shapes but often resemble the remnants of internal laser drilling (Fall 2013 Lab Notes, p. 174).

Ironically, an accidental feature that might otherwise downgrade a diamond’s value can have a positive outcome. This unique and aesthetically pleasing internal feature has created an interesting collector’s gemstone, a perfect gift for the Christmas season! Source: GIA @topic:4


Title: D-Color Natural IIa Diamond with Walstromite Inclusion Abstract: Figure 1. A CaSiO3-walstromite inclusion (100 μm) in a 3.0 ct diamond with fan-shaped black fractures. Graphite (less than 10 μm) was identified in the black fracture. Photomicrograph by Ying Ma.
Nondestructive testing methods such as Raman, photoluminescence (PL), and infrared spectroscopy have been widely applied to identify diamond and its inclusions. The NV0/− (nitrogen-vacancy) and V0 (vacancy) centers are used as a probe to confirm whether the color of a type IIa diamond is natural or caused by high-pressure, high temperature (HPHT) treatment or irradiation (Fall 2016 Lab Notes, pp. 299–301; D. Fisher et al., “The vacancy as a probe of the strain in type IIa diamonds,” Diamond and Related Materials, Vol. 15, No. 10, 2006, pp. 1636–1642).
Recently, the National Gemstone Testing Center (NGTC) laboratory in Shenzhen received a 3.0 ct diamond for identification. The stone was a standard round brilliant cut with D color, SI2 clarity, and a diameter of 9.2 mm. When exposed to DiamondView imaging, the diamond exhibited medium blue fluorescence. It was identified as type IIa because no nitrogen- or boron-related absorptions were detected in the 800–1400 cm–1 range and at 2802 cm–1. Nitrogen-vacancy centers NV0 (575 nm) and NV– (637 nm) were not detected, either.

Figure 2. In these Raman spectra, the blue line represents a reference spectrum for CaSiO3-walstromite (Smith et al., 2016, supplementary materials; 500–1100 cm–1). The red trace is from CaSiO3-walstromite in the 3.0 ct diamond (500–1100 cm–1) in the inset photo. The black line shows that the fissure is filled with black graphite; the peak at 1576 cm–1 is the G band of graphite, and the D peaks belong to diamond.
Magnification revealed some mineral inclusions and fan-shaped fractures (figure 1). Part of the fissure was filled with black material. We identified the inclusion in figure 1 as CaSiO3-walstromite and confirmed that the black fracture contained graphite using a Renishaw inVia micro-Raman confocal microscope equipped with a green solid laser (532 nm) focused through a 50× short-working-distance objective (figure 2). As the most abundant Ca-bearing mineral inclusion found in superdeep diamonds, CaSiO3-walstromite is believed to derive from CaSiO3-perovskite. Perovskite-structure minerals are predominant in the earth’s lower mantle more than 600 km below the surface. The presence of CaSiO3-walstromite and Ca-silicate inclusions is a strong indication of superdeep origin (C. Anzolini et al., “Depth of formation of superdeep diamonds: Raman barometry of CaSiO3-walstromite inclusions,” American Mineralogist, Vol. 103, No. 1, 2018, pp. 69–74).

Figure 3. In this DiamondView image of the 3.0 ct diamond, the black arrow indicates the site of dislocation networks. Image by Ying Ma.
The 3.0 ct diamond was similar to CLIPPIR (Cullinan-like, Large, Inclusion-Poor, Pure, Irregular, and Resorbed) diamonds (E.M. Smith et al., “Large gem diamonds from metallic liquid in Earth’s deep mantle,” Science, Vol. 354, No. 6318, pp. 1403–1405). Many CLIPPIR diamonds are of top color grades and type IIa, originating from a depth between 360 and 750 km. Dislocation networks, a relatively common feature in type IIa diamonds, were also found (figure 3). Dislocation networks in diamond are interpreted to be equivalent to the polygonized structure of dislocations in other minerals that have been deformed and subsequently annealed (H. Kanda et al., “Change in cathodoluminescence spectra and images of type II high-pressure synthetic diamond produced with high pressure and temperature treatment,” Diamond and Related Materials, Vol. 14, No. 11-12, 2005, pp. 1928–1931; K. De Corte et al., “Overview of dislocation networks in natural type IIa diamonds,” Fall 2006 G&G, pp. 122–123). High-temperature experimental treatment of synthetic type II diamond can also reproduce dislocation structures (H. Kanda et al., 2005; D. Fisher et al., “Brown colour in natural diamond and interaction between the brown related and other colour-inducing defects,” Journal of Physics: Condensed Matter, Vol. 21, No. 36, 2009, 364213).

Figure 4. The diamond’s infrared spectrum shows no detectable nitrogen-related absorption in the 800–1400 cm–1 range. The diamond absorption peak is at 1332 cm–1, while the peaks at 5785, 1263, 1124, and 437–669 cm–1 are unknown.

Figure 5. The diamond has a strong V0-GR1 center (741, 745 nm) and a weak (NVN)0 center (503 nm). The NV0 (575 nm) and NV– centers (637 nm) were not detected at liquid nitrogen temperature at either 325 nm (top) or 473 nm (bottom) laser excitation. The designation of the 505, 524, 668, 694, and 706 nm bands is unknown.
CLIPPIR diamonds sometimes exhibit infrared absorption at 3107 cm–1; this is a nitrogen-bearing (VN3H) defect (J.P. Goss et al., “Identification of the structure of the 3107 cm–1 H-related defect in diamond,” Journal of Physics: Condensed Matter, Vol. 26, No. 14, 2014, 145801). This diamond has no clear signature of infrared absorption at 3107 cm–1 or NV centers (PL: 575 and 637 nm). We believe that the cause of this is an extremely low level of nitrogen, below the detection limits of the instrument (figures 4 and 5). The lack of nitrogen in type IIa diamond is associated with less color in the diamond. This diamond has a strong V0-GR1 center (741, 745 nm) and no NV0/− (575 nm) and V0 (637 nm) centers (figure 5).
The CaSiO3-walstromite inclusion in this 3.0 ct diamond indicates a natural diamond from a very deep origin. Source: GIA @topic:4


Title: Large Pinkish Orange CVD Synthetic Diamond Abstract: Figure 1. This CVD-grown diamond, weighing 5.01 ct and Fancy Intense pinkish orange in color, stands out among all CVD synthetics GIA has tested so far. Photo by Jianxing (Jae) Liao.

Natural diamonds with intense pink-orange color are very rare, particularly in large sizes. GIA’s New York lab recently tested a pinkish orange CVD synthetic diamond, submitted by Unique Lab Grown Diamond Inc. in New York, that showed some outstanding gemological features.

This square cut weighed 5.01 ct (9.45 × 9.10 × 6.05 mm) and was color graded as Fancy Intense pinkish orange (figure 1). The color was distributed evenly throughout. A few small feathers and pinpoints were observable under the microscope at about 20× magnification, and the clarity was equivalent to SI1. Infrared absorption spectroscopy revealed this was a type IIa diamond, with nitrogen concentration below the instrument’s detection limit. A clear and sharp peak detected at 3123 cm–1 is a well-known specific feature of CVD synthetic diamond. The absorption spectrum in the UV-Vis region indicated that the observed bodycolor was caused by a very strong and broad absorption band around 520 nm (figure 2). This band can be introduced to a CVD diamond during its growth. It creates a color effect similar to the one from the ~550 nm band in natural pink diamonds. There is no report of the ~520 nm band being introduced to a CVD synthetic diamond after its initial growth. In photoluminescence spectroscopy, clear emissions at 737 nm from SiV– and 503 nm from the H3 defect were recorded. In addition, strong emissions at 575 and 637 nm from NV centers were detected. As a result, this synthetic diamond showed strong orange-red fluorescence in DiamondView imaging. Unlike other large CVD-grown diamonds, this diamond’s fluorescence images hardly revealed the multiple growth layers responsible for its significant thickness. Instead, the multiple growth layers with subtle boundaries could only be detected in high-resolution cathodoluminescence (CL) images.

Figure 2. The UV-Vis spectrum of this CVD synthetic revealed that its intense pinkish orange bodycolor was caused by a strong and broad absorption band around 520 nm.
Based on all spectroscopic features, we believe that this CVD synthetic diamond was not treated by HPHT annealing after its growth for color improvement, though heating to a moderate temperature could not be entirely ruled out. The combination of size, color, and clarity made this the most remarkable CVD synthetic diamond GIA has tested so far. Source: GIA @topic:4


Title: Diamond Market in Recovery, Top-end Auction Results Abstract: This GIA-graded Fancy Deep blue 7.03 ct diamond from London jeweler Moussaieff drew a top bid of $11.6 million ($1.65 million per carat) at Christie's Nov. 12 Geneva auction. Photo courtesy of Christie's Images Ltd.

Diamond Mining Industry
De Beers and Alrosa, the world’s two largest diamond producers, say the diamond market is stabilizing after several months of severe cutbacks in rough sales and are expecting reasonably strong demand during the U.S. holiday season and Chinese New Year.
Both companies cut sales more than 25% as inventories of rough and polished diamonds increased earlier in the year and prices of both softened. The banks also continued their tight credit policies for the industry.
At the Nov. 4-8 cycle, De Beers increased rough allocations by about $100 million to $390 million, but reduced prices by 5% or more. This was an extraordinary move, because De Beers rarely lowers prices by such an amount, especially on larger, better quality rough diamonds. The company usually “adjusts” prices - raising them on a few of the more than 5,000 rough categories and lowering them on others, or it simply disguises decreases by shifting better quality rough into lower categories.
De Beers never lowers prices across the board, as it did in this last cycle. But a 5% reduction is impossible to disguise. Some reports indicate that small, less expensive qualities were lowered much more. De Beers also increased its buy-back allowance from 10% to 20% for larger goods, which permits clients to sell goods back to De Beers, which it cannot absorb or cut profitably.
De Beers was likely forced into lowering prices after the September announcement by ABN Amro Bank that it would no longer provide credit for rough purchases that cannot be cut profitably, which included almost all categories of diamonds at that time.
Russia’s Alrosa announced that its third quarter rough sales fell 37% by value compared to the same period last year. The drop would have been larger if not for a recovery in October that saw an increase in revenues from the same month in 2018. One reason for the precipitous drop is that the company shifted its focus to smaller diamonds, thus sales by volume were down only 5%.
Alrosa said that October’s sales increase of 7% meant that demand was stabilizing as excess supplies in the market are being drawn down.
The ultra-large diamond market has slowed as well: Gem Diamonds, which operates the Letseng Mine in Lesotho, said the average price of diamonds recovered this year is down 23% to $1,417 per carat. Letseng’s production is small – about 110,000 carats yearly – but it routinely produces diamonds over 50 carats.
RETAIL JEWELRY MARKET
Global diamond jewelry demand increased 1.9% to a total of $76 billion, De Beers reported in its “Diamond Insight” survey released this month.
The U.S. remained the world’s largest market for diamond jewelry, accounting for $36 billion in sales; just over 47% of the world total. The diamond content in jewelry sold in the U.S. totaled $12.3 billion.
China’s retail diamond demand just topped $10 billion, with diamond content totaling $3.47 billion. Japan, at $5 billion ($1.16 billion), and India, at $3 billion ($1.3 billion), are the other top retail diamond markets.
The report noted that female self-purchase is the fastest growing category of diamond jewelry worldwide, but that gifts from men to women still represent 52% of non-engagement ring sales.
The report also noted that, because De Beers changed how it evaluates the diamond content in jewelry, the company revised previous downward estimates of total diamond sales.

A 46.93 ct GIA-graded D IF step cut cushion shape diamond sold for $3.1 million, ($66,800 per carat) at Christie's Nov. 12 Geneva auction. Photo courtesy of Christie's Images Ltd.
JEWELRY AUCTIONS
After a calm spring season, demand and prices at the extreme top end have again strengthened.
Christie's Nov. 12 Geneva auction was 93% sold by lot and 88% by value. The top lot of the sale was the GIA-graded Fancy Deep blue 7.03 ct diamond from London jeweler Moussaieff, which drew a top bid of $11.6 million ($1.65 million per carat), within the pre-sale estimate.
Other large gems that sold were:

A 46.93 ct GIA-graded D IF step cut cushion shape diamond for $3.1 million, ($66,800 per carat), just under the pre-sale estimate
A 25.2 ct GIA-graded D VVS rectangular cut diamond for $2.53 million ($100,595 per carat)
A 42.97 ct Burmese octagon cut sapphire for $2.5 million ($59,000 per carat)
A 13.53 ct Colombian emerald for nearly $1.1 million, a very strong $91,575 per carat

Interestingly, all of the buyers chose to remain anonymous, which is unusual for large gems.
The following day, Sotheby’s Geneva auction house sold 80% of the lots offered. The top lot was a Cartier bracelet containing a 47.07 ct Burmese cabochon sapphire, accompanied by two pear shaped diamonds of 9.27 and 8.6 cts for $6.1 million, doubling its pre-sale estimate. The bracelet was made in 1927 and sold to an “Asian female collector,” according to the auction house.
Another buyer paid $3.4 million for a 6.03 ct GIA-graded Fancy Intense purple pink diamond ($563,847 per carat) mounted into a pendant, while a 14.97 ct Kashmir sapphire mounted into a diamond necklace sold for $1.4 million. Source: GIA @topic:8


Title: Faceted Diamond Octahedron with a Remarkable Stellate Cloud Inclusion Abstract: Figure 1. This 3.70 ct brownish greenish yellow faceted octahedron contained a remarkable stellate hydrogen cloud (left) that showed strong yellowish green fluorescence under long-wave UV light (right). Photos by Diego Sanchez.
A 3.70 ct faceted Fancy brownish greenish yellow diamond (figure 1, left) was recently submitted to the Carlsbad laboratory for color origin and identification service. The diamond was remarkable in that it contained an eye-visible stellate cloud inclusion consisting of six legs that each radiated to a point on the polished octahedron. Diamonds containing star-like clouds are sometimes referred to as “asteriated” in the trade (T. Hainschwang et al., “The Rhodesian Star: An exceptional asteriated diamond,” Journal of Gemmology, Vol. 34, No. 4, 2014, pp. 306–315). While GIA occasionally encounters asteriated diamonds, this one was striking due to the well-defined nature of the star and the strong yellowish green color it exhibited under long-wave UV (figure 1, right).

Figure 2. The six-ray star pattern is composed of microscopic particles commonly referred to as “hydrogen clouds” (left) that fluoresce strong green to long-wave UV (right). Photos by Nathan Renfro; field of view 6.27 mm.
Gemological examination revealed a type Ia diamond, showing a typical cape series in the visible spectrum. Hydrogen bands in the infrared spectrum and the UV-Vis-NIR spectrum were consistent with the observed “hydrogen cloud” inclusions (figure 2). These clouds in diamonds consist of a high density of light scattering micro-inclusions consistent with those that have been reported to be graphite (B. Rondeau et al., “Three historical ‘asteriated’ hydrogen-rich diamonds: Growth history and sector-dependent impurity incorporation,” Diamond and Related Materials, Vol. 13, No. 9, 2004, pp. 1658–1673) that correlate strongly with the presence of hydrogen (W. Wang and W. Mayerson, “Symmetrical clouds in diamond—the hydrogen connection,” Journal of Gemmology, Vol. 28, No. 3, 2002, pp. 143–152). Also observed was brown radiation staining in a shallow feather, indicating that the stone had been exposed to natural alpha radiation (figure 3).

Figure 3. An irregularly shaped dark brown radiation stain on the diamond’s surface-reaching inclusion clearly shows that it was exposed to natural alpha radiation. Photomicrograph by Maryam Mastery Salimi; field of view 3.51 mm.
While the cutting style was unconventional, it served to showcase the remarkable inclusion scene contained within the diamond. This is one of the most interesting diamonds of this type examined at GIA’s Carlsbad laboratory. Source: GIA @topic:4


Title: Glass-Filled Polki-Cut CVD Synthetic Diamonds Abstract: Figure 1. These “polkis” exhibiting a square profile, (0.27–0.29 ct) were identified as glass-filled CVD synthetic diamonds. Photo by Gagan Choudhary.

The term polki refers to a flat-cut diamond that is a simple and ancient form of today’s “rose cut” and has been popular in traditional Indian kundan-meena jewelry. Since most commercial-quality polkis are fashioned from flat rough crystals (macles, for example) or chips derived from the cutting of larger crystals, they often contain cleavages or fissures opening on the surface, making them even more delicate. In the past decade, the trade has been flooded with polkis filled with high-RI glass to improve their clarity as well as durability, and these have been widely used in kundan-meena jewelry.

Figure 2. Glass filling in the three polkis from figure 1 was indicated by color flashes along cleavages and fissures (left and right). Also note multiple parallel incipient and intersecting cleavage planes in the left image. Photomicrographs by Gagan Choudhary; fields of view 6.35 mm (left) and 5.08 mm (right).
Recently, the Gem Testing Laboratory (GJEPC) in Jaipur received three light gray to brown polki-cut diamonds (figure 1) with square profiles for identification. They weighed 0.27–0.29 ct and measured 6.86–7.41 mm long and 0.36–0.41 mm thick. The client informed us that the polkis were natural but wanted to know if they were glass-filled. On initial examination under a microscope, glass filling in all three was evidenced by color flashes (figure 2), typically blue, violet, and pink, along with some crackling effects within the fissures and cleavage planes in two directions, intersecting each other at almost 90° (octahedral cleavage in diamond). The presence of glass (containing lead and bromine) was further confirmed by energy-dispersive X-ray fluorescence (EDXRF) analyses. These polkis also displayed a few dark brown grains, some of which were associated with stress cracks. No attempt was made to identify the nature of these grains.
Considering our past experiences with polkis having square profiles, further tests were performed to determine a natural or synthetic origin. When viewed under crossed polarizers, all three polkis displayed a checkerboard strain pattern from the top and sub-parallel columnar patterns from the sides. Infrared spectra confirmed all three specimens as type IIa; DiamondView imaging displayed orange fluorescence, but no distinct growth patterns could be resolved. No phosphorescence was detected in any of the samples. Such growth patterns (under crossed polarizers) and fluorescence have been observed previously in CVD-grown synthetic diamonds by this author, as well as reported in the literature (e.g., P.M. Martineau et al., “Identification of synthetic diamond grown using chemical vapor deposition (CVD),” Spring 2004 G&G, pp. 2–25). Furthermore, photoluminescence spectra using 532 nm laser excitation revealed a distinct silicon vacancy–related peak at ~737 nm, even at room temperature (figure 3). This feature is widely used by gemological laboratories to identify synthetic diamonds (both CVD- and HPHT-grown).

Figure 3. The room-temperature photoluminescence spectrum of each polki sample, with 532 nm laser excitation, revealed a strong silicon-vacancy related feature at ~737 nm.
In the past we have seen numerous examples of polki-cut diamonds with glass filling, as well as many CVD synthetic diamonds fashioned as polkis. This was the first time we had encountered glass-filled CVD synthetic diamond polkis, though their market penetration is unknown. Although glass filling is not challenging to identify, encountering it in synthetic diamonds could lead to a misidentification as natural, especially among the trade. Since diamond polkis are usually fashioned from flat rough or chips derived during cutting larger crystals, they often display triangular or irregular profiles, while the polkis described here had a square profile. In view of this, square-shaped polkis offer the best yield for crystals with square profiles, such as natural cubic crystal or synthetic diamond crystals grown by the CVD process, which display a square and tabular habit. Therefore, this feature is quite useful in raising doubts, especially when mixed in parcels of polki-cut natural diamond. Source: GIA @topic:4


Title: Bank Suspends Credit for ‘Unprofitable’ Rough Diamonds Abstract: Rio Tinto will hold its Argyle fancy colored diamond tender in September, a collection of 64 diamonds, including the 2019 Argyle pink diamond hero stones. They are, from left: the Argyle Verity, an oval shape, 1.37 ct Fancy Vivid purplish pink; the Argyle Enigma, a modified radiant, 1.75 ct Fancy red; the Argyle Amari, a heart-shaped, 1.48 ct Fancy Vivid purplish pink; the Argyle Opus, a round shape, 2.01 ct Fancy Intense pink; the Argyle Elysian, a modified cushion shape, 1.20 ct Fancy Vivid pink; and the Argyle Avenoir, an oval shape, 1.07 ct Fancy red. All were graded by GIA. Photo courtesy of Rio Tinto

De Beers and Alrosa both slashed their rough diamond sales in the second quarter of this year and further cuts are sure to come following ABN AMRO’s announcement that it will no longer finance rough purchases for goods that can’t be cut profitably – that includes the majority of sizes and qualities.
ABN AMRO’s restrictions are stringent. It defines “profitable” sales as those that can achieve “real sales margins for goods sold as soon as possible after purchase of rough without considering credit terms.” This means the bank is likely to finance only a narrow range of goods that are in demand; mostly medium to better quality diamonds above 0.5 cts.
The bank also said that clients wanting to use its rough buying credit facility need to apply on a case-by-case basis for the time being.
Diamond manufacturers in India report that prices have fallen as much as 10% on such diamonds in recent weeks, even though manufacturing output has declined about 40% from the same time last year.
Inventories of rough and polished diamonds in the major cutting centers – especially India – are approaching levels where the supply overhang causes polished prices to drop to levels where it is no longer profitable to cut rough – especially in goods that would result in 0.25 to 0.50 cts.
De Beers will certainly allocate another small cycle sale of rough diamond in July, following a very small June allotment. The May and June rough sales - the company’s smallest in several years - and disappointing results from the Las Vegas and Hong Kong trade shows have not helped diamond market sentiment. The company’s sales in the first half of the year are down nearly 20% compared to last year and will likely drop further during the second half of the year.
Alrosa announced that its rough diamond sales are down 33% by value for the first six months of this year, with June’s allocation down 43% compared to the same month last year. Sales will likely sink further after the ABN AMRO announcement.
Some manufacturers are expecting relief following Rio Tinto’s announcement that it will close its large Argyle diamond mine in Australia at the end of 2020. Rio had indicated it might close the mine on several occasions some years ago but, because inventories of rough and polished have been accumulating to the point that prices for both have been softening, the announcement is real this time.
It is unlikely, however, that taking Argyle’s 14 million carats out of the market will be a cure-all for the industry’s high inventories because much of the mine’s output filled a specific niche – millions of carats for low-priced mass market jewelry. The majority of Argyle’s production is small goods with a brownish tint and an average value of about $13 per carat. Removing such material from the market will not alleviate the large inventories of diamonds larger than 0.20 cts.
Just after making the mine closing announcement, Argyle unveiled its latest collection of fancy colored diamonds, which will go on sale at its annual tender sale in September. This year’s collection of 64 diamonds weighs a total of 56.28 cts.
The six hero stones, all graded by GIA, are the:

Argyle Verity, an oval shape, 1.37 ct Fancy Vivid purplish pink
Argyle Enigma, a modified radiant, 1.75 ct Fancy red
Argyle Amari, a heart-shaped, 1.48 ct Fancy Vivid purplish pink
Argyle Opus, a round shape, 2.01 ct Fancy Intense pink
Argyle Elysian, a modified cushion shape, 1.20 ct Fancy Vivid pink
Argyle Avenoir, an oval shape, 1.07 ct Fancy red

This will probably be the penultimate Argyle fancy colored diamond tender sale, which began in 1984. Source: GIA @topic:8


Title: Is There a Difference Between Natural and Laboratory-Grown Diamonds? Abstract: Laboratory-grown CVD rough diamond (left), laboratory-grown HPHT rough diamond (middle) and natural rough diamond (right)

Two specimens of faceted crystalized carbon - both are crystal clear and give off a kaleidoscope of spectral colors in direct light. They appear to be identical. One, however, is a billion or more years old and the other was recently grown in a laboratory.
Both are diamonds, of course. The first is a natural diamond created by forces deep within the young Earth. The second is from a laboratory and possesses essentially the same chemical, physical and optical properties as its natural counterpart.
Diamond – the material, not the gem – is a mineral consisting of “essentially pure carbon crystalized in the isometric cubic system,” according to the U.S. Federal Trade Commission (FTC), which develops trading guides for the gem and jewelry industry.
Although the FTC says diamonds are essentially pure carbon, the vast majority of natural diamonds contain trace amounts of other substances, particularly nitrogen, which gives them a yellow color or (rarely) boron, which imparts a blue color. In addition, they usually contain inclusions, tiny bits of foreign material that were trapped in the still-forming diamond millions of years ago.
Laboratory-grown diamonds (also sometimes referred to as man-made or synthetic diamonds) entered the gem and jewelry market in commercial quantities about five years ago. Although identical in appearance to natural diamonds, they have very subtle differences that can only be detected by trained gemologists and sophisticated equipment designed for that purpose.

A comparison of rough diamonds shows a 0.83 ct natural diamond crystal on the left and a 1.02 ct HPHT crystal on the right. Both crystals are from the GIA Research Collection. Photo: Orsasa Weldon/GIA
WHERE DO DIAMONDS COME FROM?

Natural Diamonds
Natural diamonds formed deep in the earth under extreme pressure and high temperature as long as three billion years ago. Volcanic activity brought them to the surface where they lay in a type of volcanic rock formation known as kimberlite pipes, waiting to be mined. Only about five percent of kimberlite pipes contain enough diamond to make them economically feasible to mine.

Open pit of the Arkhangelskaya kimberlite in Lomonosov, Russia. Photo: Karen Smit/GIA
Laboratory-Grown Diamonds
Man-made diamonds suitable for industrial use were first produced in a laboratory in the 1950s. While gem-quality diamonds were produced in a laboratory for the first time in 1971, it was not until the mid-2010s that colorless laboratory-grown diamonds entered the gem and jewelry market in commercial quantities.
Today, laboratory-grown diamonds are created by two methods, according to Dr. James Shigley, GIA Distinguished Research Fellow, who has been researching laboratory-grown diamonds at GIA for more than 30 years.
High pressure, high temperature (HPHT) diamonds are produced in a laboratory by mimicking the high pressure, high temperature conditions that form natural diamonds in the Earth. This process produces a distinctively shaped laboratory-grown diamond crystal.
The chemical vapor deposition (CVD) method involves breaking down the molecules of a carbon-rich gas, such as methane, into carbon and hydrogen atoms, which then are deposited on diamond seeds to produce a square-shaped, tabular diamond crystal.
Growing diamonds by either method typically requires less than a month for most sizes. Most CVD-grown diamonds require additional treatments like heat or irradiation to enhance or change their colors after the growth process.
Typically, laboratory-grown diamonds have weighed a carat or less, but as technology and techniques improve, larger stones have appeared in the market.

HPHT (High-Pressure and High-Temperature) presses enclosed in a factory which can produce gem-quality diamonds within a large range of sizes. Photo: Wuyi Wang/GIA
HOW CAN NATURAL AND LABORATORY-GROWN DIAMONDS BE DISTINGUISHED FROM ONE ANOTHER?
It is essential that laboratory-grown diamonds can be identified because consumers need to know what they are buying, and because there are often significant price differences between them and natural gemstones.
As part of its mission to protect and inform the gem-buying public, GIA offers diploma programs, including the GIA Graduate Gemologist credential, and seminars that teach diamond grading techniques and the latest methods used to distinguish natural from laboratory-grown diamonds and diamond simulants.
Because laboratory-grown diamonds are essentially chemically and optically the same as their natural counterparts, traditional gemological observations and old-style “diamond detectors” are not able to tell them apart. Identification at a professional gemological laboratory or using sophisticated devices developed by GIA and other organizations are the only reliable methods to separate them from natural diamonds.
Diamond Morphology – the Telltale Factor
“Natural diamonds that formed in the Earth over millions of years grow differently from diamonds created in a laboratory in a few weeks. In addition, HPHT- and CVD-created diamonds have different growth morphology, or how growth conditions influenced the shape of the diamond crystal,” said Dr. Shigley.
GIA Senior Research Scientist Dr. Sally Eaton-Magaña further explained, “The identification criteria for HPHT and CVD diamonds are quite distinct from each other,” adding that laboratory-grown diamonds have become much more varied over the last 10 to 15 years, requiring GIA researchers to keep pace with new developments.
“We also regularly conduct research on emerging products and GIA has a program to grow diamonds in the laboratory to stay ahead of any new trends,” Dr. Eaton-Magaña said.

This chart shows the different diamond rough based on how they grew, or their growth morphology. Though this shape is lost after a diamond is cut and polished, identification is still possible by looking for fluorescence patterns that result from its particular growth morphology among other things.
DOES GIA OFFER GRADING FOR LABORATORY-GROWN DIAMONDS?
GIA tests every diamond submitted to its gemstone grading and identification laboratory locations around the world to determine whether they are natural or laboratory-grown.

In July, GIA will include the full GIA color and clarity scales on its laboratory-grown diamond reports.
GIA has issued reports for laboratory-grown diamonds for more than 10 years. In March 2019, following the guidelines from the FTC, the Institute announced it will change the name of the reports to GIA Laboratory-Grown Diamond Reports starting in July 2019. To reduce the potential for confusion, GIA grading reports for laboratory-grown diamonds look significantly different from those for natural diamonds. In addition, the terms used to report color and clarity grades for laboratory-grown diamonds are different from those used for natural diamonds. Instead of D-to-Z color grades, broader category terms (Colorless, Near-Colorless, Faint, Very Light and Light) are used. Clarity grades, which are abbreviated on natural diamond reports (VVS1, SI2, etc.), use broader descriptive category terms (i.e., Very Very Slightly Included, Slightly Included) on the reports for laboratory-grown diamonds.
WHAT ABOUT DIAMONDS THAT ARE NOT SUBMITTED TO GEM LABS FOR GRADING?

The GIA iD100 allows retailers to rapidly and accurately screen loose and mounted  diamonds as small as .005 ct.
To identify laboratory-grown diamonds, GIA developed the GIA iD100® screening device. This desktop-sized instrument combines advanced spectroscopic technology with GIA’s 60 years of diamond and gemstone identification research to distinguish natural diamonds from laboratory-grown (HPHT and CVD) diamonds and diamond simulants.
GIA also offers the GIA Melee Analysis Service, which quickly and accurately screens parcels of very small diamonds – the most prevalent in the market. Source: GIA @topic:4