Publish Year: 2013 Title: Pseudo-Synthetic Growth Structure Observed in Natural Diamond Abstract: Figure 1. This 0.70 ct, D-color natural round brilliant displayed the cuboctahedral growth structure of an HPHT-grown synthetic diamond. Photo by Jian Xin(Jae) Liao.

Synthetic diamonds created using the traditional HPHT (high-pressure, high-temperature) process ordinarily grow as cuboctahedra. Temperature dictates the crystal form, as cubic growth is predominant at the relatively low temperatures of synthesis. At the higher temperatures of natural formation environments, diamonds typically grow as octahedrons. While small cuboctahedral diamonds are found in nature, these are very rare.
Recently submitted to the GIA laboratory in Israel was a near-colorless 0.70 ct round brilliant (figure 1). Found to be a type IIa diamond with no detectable nitrogen impurity, it was examined further for possible treatments and to verify the origin of color.

Figure 2. DiamondView imaging of the pavilion facets revealed a subtle growth structure. The inset shows the growth structure of a type IIb synthetic diamond. Photo by Wuyi Wang.
In the short-wave UV radiation of the DiamondView, a subtle cuboctahedral growth structure (figure 2) was observed on the pavilion facets. This type of structure usually indicates an HPHT-grown synthetic diamond.
The diamond possessed D color and high clarity, with no internal inclusions to help indicate whether it was in fact natural. Shallow surface-reaching fractures were observed, and a few extra facets close to the pavilion contained these natural-looking fractures.
Microscopic observation with cross-polarized light showed relatively strong tatami strain pattern (figure 3), a feature indicative of natural growth. Further examination at higher magnification revealed small polygonal dislocation networks on the pavilion. These provided conclusive evidence that the stone was a natural diamond crystal (figure 4).

Figure 3. A tatami strain pattern, observed under crossed-polarized light, indicated natural growth. Magnified 40×. Photo by Paul Johnson.

Figure 4. DiamondView imaging showed a micro-dislocation network on pavilion facets, conclusive proof of natural crystal growth. Photo by Wuyi Wang.
This stone was a good example of a very rare natural diamond exhibiting synthetic growth characteristics. It exemplifies the challenges posed to gemological laboratories in separating natural from undisclosed gem-quality synthetic diamonds in today’s jewelry market. We concluded that the diamond had a natural color origin. @topic:4


Publish Year: 2020 Title: Solid Carved Dark Gray Diamond Ring Abstract: Figure 1. This carved Fancy Dark gray diamond ring weighs 13.15 ct. The whitish areas are clear viewing windows. Photo by Jianxin (Jae) Liao.

A ring made entirely of natural diamond (figure 1) was recently submitted to GIA’s New York laboratory. A large rough weighing approximately 196 ct was used to create this unusual 13.15 ct carved piece. It is common to find solid carved rings of jade and wood, which were traditionally worn as symbols of status or wedding rings signifying eternity. This is the first example of a solid diamond ring submitted to GIA for identification.

Figure 2. Needle clusters in the carved Fancy Dark gray diamond ring. Photomicrograph by Stephanie Persaud.
This solid type IaB diamond ring owes its Fancy Dark gray color to the graphite needles (figure 2) trapped during formation deep below the earth’s surface. Like famous gem-quality black diamonds such as the Black Orlov, the Korloff Noir, the Black Star of Africa, and the Spirit of de Grisogono, this diamond has clear spaces creating viewing windows that capture a snapshot of the ring’s formation history. The ring was fashioned from the Beaufort diamond from Canada’s Northwest territories and named the “Beaufort Ring.”

Figure 3. Fluorescence imaging using the DiamondView shows bundled dislocation networks. Image by Stephanie Persaud.
This diamond rough from which the ring was carved likely formed billions of years ago under high pressure. During regional metamorphism, H3 and NiN complexes were formed within the crystal lattice (K. Smit et al., “Black diamonds from Marange (Zimbabwe): A result of natural irradiation and graphite inclusions,” Summer 2018 G&G, pp. 132–148). These impurities were detected by photoluminescence spectroscopy. Infrared spectroscopy was used to detect the B aggregates and hydrogen complexes within the diamond lattice, categorizing this diamond as type IaB. Fluorescence imaging of the ring using the DiamondView showed bundled dislocation networks indicative of natural diamond growth (figure 3). While this diamond ring may not be a traditional piece, it carries many unique aspects capturing a snapshot of Earth’s history within a true infinity band. @topic:10


Publish Year: 2014 Title: Two Fancy Dark Gray CVD Synthetic Diamonds Abstract: Figure 1. This 1.50 ct Fancy Dark gray CVD synthetic diamond was unusual for its combination of color grade and large size. Photo by Jian Xin (Jae) Liao.

              Recently, two colored synthetic diamonds examined in the Carlsbad laboratory were determined to have been grown by the chemical vapor deposition (CVD) method. Both received an unusual color grade of Fancy Dark gray. GIA has graded other gray CVD synthetics before, but within the Fancy Light to Fancy range; it is rare for a synthetic to receive a Fancy Dark color grade. The few Fancy Dark synthetic diamonds submitted in the past have all been HPHT synthetics (most of them Fancy Dark reddish brown) with post-growth treatment that created NV centers. The two gray CVD specimens were also noted for their size—0.80 and 1.50 ct. The latter is shown in figure 1.

In addition to their color grade, both showed similar spectra. Neither sample’s UV-visible-NIR spectrum displayed any distinct absorption peaks. The mid-IR spectra identified them as type IIa diamond but did not contain features that confirmed synthetic origin. Their photoluminescence (PL) spectra had nearly identical features, suggesting that they originated from similar manufacturing processes. Both PL spectra featured a large silicon-vacancy doublet at 737 nm, a strong indicator of CVD growth (though natural diamonds will occasionally show a weak silicon peak along with other natural features); this was confirmed by the DiamondView images. The 1.50 ct specimen showed light blue fluorescence and striations commonly observed in CVD synthetics (figure 2, left) (P. Martineau et al., “Identification of synthetic diamond grown using chemical vapor deposition (CVD),” Spring 2004 G&G, pp. 1–25). The 0.80 ct sample offered a more unusual DiamondView image, with yellow fluorescence interspersed with regions of purple mottling. The purple mottling is seen occasionally in CVD synthetics, but usually combined with a background of pink fluorescence (W. Wang et al., “Latest-generation CVD-grown synthetic diamonds from Apollo Diamond Inc.,” Winter 2007 G&G, pp. 294–312) instead of the yellow fluorescence seen here. Some regions of the 0.80 ct synthetic had natural-looking fluorescence features (figure 2, right), but a thorough examination of the DiamondView fluorescence in conjunction with the silicon peak unambiguously identified it as CVD.

Figure 2. Left: In the DiamondView, the 1.50 ct sample showed the familiar color and striations of CVD synthetics. Right: The 0.80 ct specimen displayed a combination of natural-appearing features in some regions (as shown) and CVD-related striations and purple mottling in others. Images by Sally Magaña.
The DiamondView images of both synthetics also demonstrated blue phosphorescence, which is often associated with boron impurities. No known boron-related peaks were detected in the PL or mid-IR spectra, so the boron concentration would be below the level of detection by FTIR spectroscopy. Boron-related peaks seen in natural and treated type IIb diamonds often are not detected in known IIb HPHT- and CVD-grown synthetics. It is unclear whether the low boron concentration was deliberately introduced to improve growth rate and quality (S. Eaton et al., “Diamond growth in the presence of boron and sulfur,” Diamond and Related Materials, Vol. 12, 2003, pp. 1627–1632). Boron-containing diamonds with low color saturation often appear gray, making this element the likely cause of color in both of these CVD synthetic diamonds. @topic:4


Publish Year: 2022 Title: New Record Size for CVD Laboratory-Grown Diamond Abstract: Figure 1. The new record size for CVD laboratory-grown diamond—16.41 ct, with G color and VVS2 clarity—has been achieved by Shanghai Zhengshi Technology Co. Ltd. This is an as-grown diamond; no post-growth treatment was applied for color improvement, either before or after faceting. Photo by Towfiq Ahmed.
Growth technology of single-crystal diamond has advanced significantly in the last two decades for both the high-pressure, high-temperature (HPHT) and chemical vapor deposition (CVD) methods. In addition to many other applications, laboratory-grown diamonds have become an expanding segment of the jewelry industry. Records for crystal size and quality are frequently broken. In this note, GIA’s New York laboratory reports on a new record for CVD laboratory-grown diamond.

	New Record Size for CVD Laboratory-Grown Diamond

Figure 2. Left: The photoluminescence spectrum with 514 nm laser excitation under liquid nitrogen temperature showed typical features of as-grown CVD diamond. Right: In the photoluminescence spectrum with 457 nm laser excitation under liquid nitrogen temperature, weak emissions from the 3H defect and from the 467.6 nm center were recorded.
This square modified brilliant diamond produced by Shanghai Zhengshi Technology Co. Ltd. (figure 1) weighed 16.41 ct and measured 13.97 × 13.87 × 9.56 mm, with G color and VVS2 clarity. The strong graining distributed throughout it created a “wavy” appearance (see the video). In addition, a few tiny pinpoints were present. Absorption spectroscopy in the infrared region revealed this was a typical type IIa diamond. Except for absorptions from the diamond itself, no other defect-related absorption was detected in this region. Photoluminescence spectroscopy collected at liquid nitrogen temperature with 514 nm laser excitation (figure 2, left) showed emissions from NV centers with zero-phonon lines (ZPL) at 575.0 and 637.0 nm with moderate intensities. Clear emissions from SiV– at 736.6 and 736.9 nm were detected. Weak emissions at 596 and 597 nm, which are specific to CVD diamond and also unstable at high temperature, were recorded overlapping with sidebands of the NV0. Photoluminescence spectroscopy with 457 nm laser excitation (figure 2, right) detected weak emissions at 503.5 nm (3H) and 467.6 nm. Similar to the emission at 596 and 597 nm, the 467.6 nm center is CVD-specific and would be annealed out at very high temperature. No emission from the H3 defect was observed. All these spectroscopic features confirmed this was a CVD diamond with no post-growth treatment to improve the color.

Figure 3. Fluorescence imaging with deep short-wave UV excitation showed the typical orange-red fluorescence of as-grown CVD diamond with irregular blue “banding.” Up to seven growth layers were revealed. Image by Stephanie Persaud.

Figure 4. The large CVD diamond showed very strong dislocations under crossed polarizers, the main cause of its wavy appearance. Photo by Stephanie Persaud.
Images collected under deep short-wave UV excitation showed strong orange-red fluorescence with banded blue regions (figure 3). The blue “columns” were nearly perpendicular to the table and extended almost continuously to the pavilion and culet. This feature was consistent with both the strong lattice dislocations observed under the microscope with crossed polarizers (figure 4) and its observable graining. Up to seven growth steps were revealed in the fluorescence and cathodoluminescence images (figure 5), with each layer of similar thickness. This square modified brilliant diamond was faceted with its table face parallel to these layers for maximum weight retention, while keeping excellent proportions and symmetry.

Figure 5. Cathodoluminescence imaging also revealed the seven growth steps. The dark dots in this image are related to the lattice dislocations. Image by Elina Myagkaya.
For CVD growth, this 16.41 ct diamond broke the record previously held by a 14.60 ct diamond (emerald cut, F color, VS2 clarity) produced in India, which surpassed the previous record of 12.75 ct (round brilliant, F color, VVS2 clarity), both reported last year (“IGI certifies world record 14.60 ct lab grown diamond,” IGI GemBlog, August 31, 2021). In comparison, the largest colorless or near-colorless HPHT laboratory-grown diamond is 15.32 ct (cushion cut, H color, I1 clarity); see Summer 2018 Lab Notes, pp. 217–218. The largest laboratory-grown diamond of any kind tested by GIA so far is a 20.23 ct cushion cut (Fancy Vivid yellowish orange, VS2) produced using the HPHT method in 2019. GIA will continue to follow the development of laboratory-grown diamonds to ensure that all are properly identified. @topic:4


Publish Year: 2018 Title: Five CVD Synthetic Diamonds Greater Than Three Carats Abstract: This 3.52 ct sample was the largest of a selection of recently submitted CVD synthetics. Photo by Robison McMurtry.

The quality and carat weight of CVD synthetic gem diamonds has increased dramatically over the last ten years (S. Eaton-Magaña and J.E. Shigley, “Observations on CVD-grown synthetic diamonds: A review,” Fall 2016 G&G, pp. 222–245). Very recently a 6 ct round CVD synthetic was reported (“US lab creates 6ct. CVD synthetic,” Rapaport News, Feb. 1, 2018). However, we still only occasionally receive CVD synthetic diamonds for grading reports, and very rarely do these submissions weigh more than three carats. In fact, GIA graded its first CVD synthetic over three carats not long ago, in October 2015 (Winter 2015 Lab Notes, pp. 437–439), and as of January 2018 had only examined a total of eight. So it was quite interesting when, in late January 2018, we received five CVD synthetics simultaneously (four known to be from the same client) that were all above three carats. The quality factors for these five samples submitted for synthetic diamond grading reports are presented in table 1, and the largest of the five is shown above.

As table 1 shows, four of the five were in the near-colorless range and the smallest one was in the colorless range. Four had clarity grades equivalent to VS1 or VS2, while the largest was equivalent to SI2. All three round brilliants received Excellent cut grades. These results are consistent with a recent survey (Eaton-Magaña and Shigley, 2016), which found that a majority of D-to-Z CVD synthetics are in the near-colorless range (67%) and that a slight majority have clarity grades equivalent to VVS2–VS1.

In keeping with standard GIA procedure, we performed IR absorption and photoluminescence (PL) spectroscopy on all five samples. As expected for CVD synthetics, all were identified as type IIa, showed pronounced silicon-related peaks in their PL spectra, and displayed striations in DiamondView imaging that are characteristic for CVD synthetics. All except the 3.52 ct sample also showed nickel-related peaks at 883/884 nm in their PL spectra with 830 nm excitation. We expect that submissions of CVD synthetics in this weight range and beyond will become more common in the next few years. @topic:4


Publish Year: 2017 Title: First Observation of H4 Defect in CVD Synthetic Diamond Abstract: Figure 1. This 0.26 ct pink synthetic diamond contains the first H4 defect GIA has observed in a CVD synthetic diamond. Photo by Robison McMurtry.

	Diamond consists of a relatively simple lattice of carbon atoms wherein only a few impurities can substitute into the structure. Despite the apparent simplicity, the diversity of defects that can exist in the diamond lattice is astounding. Nitrogen is the most abundant impurity in diamond; one of the defects commonly seen in natural diamonds, the H4 defect, consists of four nitrogen atoms and two vacancies. It is strongly associated with B-aggregated nitrogen impurities, which consist of four nitrogen atoms surrounding a single vacancy. H4 is created through a fairly straightforward formation mechanism where a single vacancy is trapped adjacent to a B-aggregate of nitrogen. H4 is often seen in irradiated and annealed diamonds with suitable amounts of B-form nitrogen, and is a mature aggregate of nitrogen that is very difficult to achieve in synthetic diamond growth or even post-growth treatment.

	We were very surprised to observe an H4 peak at 496 nm in a pink synthetic diamond grown by chemical vapor deposition (CVD) that was recently submitted to GIA’s Carlsbad laboratory for a synthetic colored diamond grading report. This 0.26 ct round brilliant (figure 1) was type Ib (single substitutional nitrogen impurities) with a very low total nitrogen content and no detectable A or B form nitrogen. FTIR spectroscopy also showed a peak at 3107 cm–1, indicating the presence of a defect consisting of three nitrogen atoms surrounding a vacancy along with a hydrogen atom.

	In addition to the observation of the H4 defect (figure 2, left), the synthetic nature of the sample was revealed by the 737 nm SiV– defect in the photoluminescence (PL) spectrum (figure 2, right). The presence of (subtle) growth layers in the DiamondView fluorescence images provided further confirmation. This diamond was grown using gas that was doped with nitrogen, allowing its incorporation into the diamond lattice as single substitutional nitrogen. The pink color was produced by NV– centers created during post-growth irradiation and annealing treatment. Nitrogen aggregation from single substitutional nitrogen to the more complex B-form nitrogen requires very high temperatures and pressures: 2500°C and 9.5 GPa for several hours (I. Dobrinets et al., HPHT-Treated Diamonds: Diamonds Forever, Springer Science & Business Media, 2013, p. 41) and generally requires a high starting concentration of nitrogen. This CVD synthetic diamond had low total nitrogen content and was grown under vacuum and likely irradiated and annealed at atmospheric pressure, making the occurrence of H4 even more puzzling. It is possible that the H4 was created during the irradiation and annealing process, but among the many samples GIA has examined, this was the first observation of this defect in a CVD synthetic diamond.

	Figure 2. Photoluminescence spectra of the pink CVD synthetic diamond showed the occurrence of an H4 defect (left) as well as a SiV– defect (right). @topic:4


Publish Year: 2022 Title: A Closer Look at Internal Etch Channels in Diamond Abstract: Figure 1. A 1.02 ct Fancy Deep brownish yellowish orange diamond with subsurface etch channels (upper right). Photo by Matthew Hardman.
The Carlsbad laboratory recently received a 1.02 ct cushion-cut Fancy Deep brownish yellowish orange diamond (figure 1). The yellowish color of this type Ib/IaA diamond is mainly attributed to single substitutional nitrogen atoms in the diamond lattice. In addition to the presence of multiple pinpoint inclusions, the diamond contained a bundle of internal etch channels extending from a single irregular-shaped opening on the girdle (figures 1 and 2).

Figure 2. A bundle of internal etch channels extending from a single opening on the girdle. Photomicrograph by Matthew Hardman; field of view 2.44 mm.

Figure 3. An irregular-shaped opening on the girdle where fluids/melts permeated through the diamond and formed the internal etch channels. Photomicrograph by Matthew Hardman; field of view 1.26 mm.
Narrow etch channels are rarely observed in gem diamonds. Etch channels can form due to dissolution of the diamond crystal by fluids/melts in the mantle, or during eruption to the surface (T. Lu et al., “Observation of etch channels in several natural diamonds,” Diamond and Related Materials, Vol. 10, No. 1, 2001, pp. 68–75;  J.W. Harris et al., “Morphology of monocrystalline diamond and its inclusions,” Reviews in Mineralogy and Geochemistry, Vol. 88, No. 1, 2022, pp. 119–166). Defects in the diamond structure such as lattice dislocations are local areas of structural weakness, which are more susceptible to etching. In this diamond, multiple narrow etch channels originate from a single surface opening (figure 3), reflecting selective diamond dissolution as fluids permeated through the stone.

Figure 4. Trigons visible in a subsurface diamond etch channel. Photomicrograph by Mei Yan Lai; field of view 1.00 mm.
An intriguing feature observed along the walls of the internal etch channels consisted of multiple triangular etch pits known as trigons (figure 4). Trigons are one of the most common features found on the surfaces of rough diamonds, with various sizes, depths, and shapes (e.g., flat- or point-bottomed, attributed to etching by oxidizing fluids/melts; Harris et al., 2022). When present on diamond surfaces, trigons are restricted to the octahedral crystal face and may occasionally form parallel rows that follow the orientation of plastic deformation lines (often called “grain lines” in the trade, caused by dislocation of carbon atoms along octahedral planes). In faceted diamonds, trigons are usually removed by polishing but are occasionally preserved on the girdle. Conversely, trigons reported within internal diamond etch channels are extremely rare (Lu et al., 2001). The occurrence of trigons within a subsurface channel indicates etching along the octahedral crystal face of this diamond. @topic:4


Publish Year: 2022 Title: Large Orange Rutile Inclusion in a “Chameleon” Diamond Abstract: An orange rutile crystal partially enclosed on the crown of a faceted diamond (the sharp line from top left to bottom right is the facet junction). Photomicrograph by Tyler Smith; field of view 0.8 mm.
The author recently received for analysis a 1.51 ct round brilliant diamond with very light green color and SI2 clarity. The diamond exhibited “chameleon” properties, showing a clear color change from green to yellow upon heating with an alcohol lamp. An ~0.2 mm orange inclusion was clearly visible on the crown (see above). The crystal was partially enclosed, confirming it was an actual inclusion rather than a crystal adhered to the diamond surface. It was also partially exposed, enabling simple Raman spectroscopy for identification without the spectra showing any contribution from the diamond itself. The crystal was determined to be rutile (TiO2), suggesting an eclogitic origin.
Rutile inclusions in diamond are themselves relatively uncommon, and we rarely see such a large, eye-catching crystal. Rutile inclusions can also provide useful clues about a diamond’s age. Geochemists can determine the age of rutile crystals by measuring the concentration of isotopes of various elements that are present at parts-per-million concentrations, allowing for constraints on the age of the diamond itself (see A.K. Schmitt et al., “U-Pb ages of rare rutile inclusions in diamond indicate entrapment synchronous with kimberlite formation,” Lithos, Vol. 350-351, 2019, article no. 105251). It will be interesting to see what scientific information this rare inclusion in diamond may reveal. @topic:10


Publish Year: 2022 Title: A Synthetic Moissanite Presented as Natural Diamond Rough Abstract: Figure 1. This 7.42 ct light bluish green synthetic moissanite, submitted as a diamond, displays triangular features on each of the octahedral faces. Photo by Jian Xin (Jae) Liao.
A 7.42 ct light bluish green specimen (figure 1) submitted to the New York lab for a colored diamond identification and origin report was identified as a synthetic moissanite crystal carved to resemble a natural diamond rough. Since synthetic moissanite resembles diamond at a glance and has a similar specific gravity and “heft,” it could easily be mistaken for natural diamond. The sample was first identified as synthetic moissanite using Fourier-transform infrared (FTIR) spectroscopy (figure 2). The resulting data displayed a distinctive moissanite spectrum, with peaks occurring at 2079, 2297, and 2392 cm–1 (A.M. Hofmeister et al., “Optical constants of silicon carbide for astrophysical applications,” Astrophysical Journal, Vol. 696, No. 2, 2009, pp. 1502–1516). This finding was confirmed with an analysis of the Raman spectrum, which showed strong 767, 788, and 798 cm–1 peaks, also consistent with synthetic moissanite (figure 3). Although natural moissanite does exist, crystals are tiny and fragmented. Gem-quality specimens have not yet been found (Summer 2014 Gem News International, pp. 160–161).

Figure 2. The peaks at 2079, 2297, and 2392 cm–1 displayed in this FTIR spectrum are consistent with synthetic moissanite.

Figure 3. Raman spectroscopy confirmed the identification as synthetic moissanite, with peaks at 767, 788, and 798 cm–1. (The sharp peak at 970 cm–1 suggests a hexagonal 6H type of silicon carbide.)
The turbid and stained 7.42 ct synthetic moissanite was shaped into a slightly rounded octahedron with prominent stepped edges. Octahedra belong to the cubic crystal class; both natural and synthetic SiC belong to the trigonal class and always display hexagonal prismatic to tabular forms. It was concluded that the synthetic moissanite rough had been carved into an octahedron, and that the detailing of the stepped edges and coarse textures were specifically chosen to imitate the appearance of a natural diamond octahedron that had been partially resorbed by kimberlitic magma, such as the natural diamond in figure 4. Although sharp and well-formed diamond octahedra are occasionally found preserved in mantle rocks entrained in kimberlitic eruptions, the vast majority of natural diamond crystals are exposed to corrosive kimberlitic fluids during their ascent through the cratonic mantle and display a wide variety of resorption textures (R. Tappert and M.C. Tappert, Diamonds in Nature: A Guide to Rough Diamonds, 2011, Springer Verlag, Heidelberg, Germany).

Figure 4. Exposure to kimberlitic fluids rich in O2 and H2O creates varied shapes and textures in natural diamond octahedra. This natural green diamond, known as the “Matryoshka” (Spring 2020 Lab Notes, pp. 127–129) has resorbed points and edges as well as trigonal etching on the {111} faces. Photo by Jian Xin (Jae) Liao.
This investigation is a reminder to take caution when identifying gemstones, as intentional material processing steps such as these may be used to deceive consumers and could damage the integrity of the gem trade. @topic:4


Publish Year: 2022 Title: Treated Orange and Pink CVD Laboratory-Grown Diamond Abstract: Figure 1. These 2.00 ct Fancy Deep orange (left) and 3.00 ct Fancy Vivid orangy pink (right) CVD-grown diamonds were subjected to multiple treatments including HPHT processing, irradiation, and low-temperature annealing to achieve the final color grades. Photos by Diego Sanchez (left) and Sood Oil (Judy) Chia (right).
Recently, GIA received two similarly treated diamonds grown by chemical vapor deposition (CVD): a 2.00 ct Fancy Deep orange and a 3.00 ct Fancy Vivid orangy pink (figure 1). A database search revealed that the Fancy Deep orange was the first CVD-grown diamond with an unmodified orange color ever submitted to GIA. CVD-grown diamonds with an orangy pink color are far more common, and the 3.00 ct sample provided for an interesting comparison. From examination of the visible/near-infrared (Vis-NIR) absorption spectra, both samples had similar features and likely underwent similar treatment processes (figure 2). The subtle differences in relative peak intensities were sufficient to create the distinctly different appearances and color grades.

Figure 2. The 2.00 ct Fancy Deep orange and the 3.00 ct Fancy Vivid orangy pink CVD-grown diamonds underwent similar post-growth treatments and show similar defect centers in their Vis-NIR absorption spectra, including the NV centers, 594 nm, SiV–, and GR1. However, subtle differences in relative defect concentrations lead to their distinct color appearances. Although very small, the GR1 defect was also detected in the absorption spectrum of the 2.00 ct CVD-grown diamond. Spectra are offset vertically for clarity.
The Vis-NIR absorption spectra for both CVD-grown diamonds showed nitrogen vacancy centers (principal absorption for NV0 at 575 nm and NV– at 637 nm), 594 nm peak, and the GR1 center. Both samples also displayed strong absorption of the SiV– center (737 nm). In the Fancy Deep orange sample, the NV centers exhibited lower absorption than in the orangy pink sample and also a slightly greater SiV–-related absorption, which helped shift the transmission window from the red (i.e., pink) toward the orange.
Based on the comparatively low value of the 468 nm emission peak determined by 457 nm photoluminescence spectroscopy, both CVD-grown diamonds showed evidence of high-pressure, high-temperature (HPHT) treatment; they were subsequently irradiated to generate the radiation-related features that included the 594 nm peak and the GR1 center. Irradiation was followed by low-temperature annealing, which was intended to generate additional NV centers without fully annihilating the GR1 center. The 594 nm center is a radiation-related defect in nitrogen-containing diamonds. In the IR absorption spectra of both CVD-grown diamonds, small peaks at 1344 cm–1 were observed. From those peaks, the single nitrogen concentration could be estimated as ~1 ppm (S. Eaton-Magaña and J.E. Shigley, “Observations on CVD-grown synthetic diamonds: A review,” Fall 2016 G&G, pp. 222–245).
Both samples presented red fluorescence when excited by the deep UV wavelengths of the DiamondView, a feature that is consistent with the strong nitrogen-vacancy centers in these CVD-grown diamonds. However, neither sample showed any noticeable photochromic effects from the deep UV exposure, something that can occur in CVD-grown diamonds due to charge transfer of the NV centers or the SiV– centers (S. Eaton-Magaña et al., “Laboratory-grown diamond: A gemological laboratory perspective,” Journal of Gems and Gemmology, 2021, Vol. 23, No. 6, pp. 25–39).
The Fancy Deep orange sample was interesting to observe, as unmodified orange colors are extremely rare among natural diamonds and, until now, laboratory-grown samples. Subtle engineering of defect concentrations during post-growth treatment can lead to vastly different results in the color grades. @topic:4


Publish Year: 2022 Title: Exceptional Natural-Color Fancy Red Diamond Abstract: This 1.21 ct round brilliant diamond is notable for its size and natural Fancy orangy red color. Photo by Diego Sanchez.
The Carlsbad laboratory recently received a 1.21 ct Fancy orangy red round brilliant cut diamond (6.62–6.84 × 4.14 mm; see above) for a colored diamond grading and identification report. Results of standard gemological testing and microscopic observation confirmed it had a natural color and no color treatment or clarity enhancement. The stone displayed faint fluorescence under long-wave UV and none under short-wave UV. Fourier-transform infrared spectroscopy indicated a type IaB diamond, while ultraviolet/visible (550 nm band and H3 [503.2 nm] center) and photoluminescence (PL) spectroscopy indicated natural color without any treatment. The 550 nm absorption band is closely linked to plastic deformation, which is clearly reflected in the broad emission features in the PL results. Due to the extensive plastic deformation, some fractures could have developed.
The rarity and high value of red diamonds has resulted in many attempts to reproduce this color through treatment or even laboratory growth procedures with post-growth treatment (S. Eaton-Magaña and J.E. Shigley, “Observations on CVD-grown synthetic diamonds: A review,” Fall 2016 G&G, pp. 222–245; S. Eaton-Magaña and J.E. Shigley, “Observations on HPHT-grown synthetic diamonds: A review,” Fall 2017 G&G, pp. 262–284). However, treated red diamonds are often accompanied by purplish or brownish color components that are not desirable and are different from the purer hues of naturally red diamonds (W. Wang et al., “Treated-color pink-to-red diamonds from Lucent Diamonds Inc.,” Spring G&G 2005, pp. 6–19). Natural-color red diamonds are so rare that only around a couple dozen true red diamonds are known to exist, and most of these are under half a carat.
The exceptional natural-color 1.21 ct Fancy orangy red diamond examined here is a fine example of natural-color red diamond. It has yet to be named. @topic:4


Publish Year: 2022 Title: Natural Diamond with Extensive Network of Etch Channels Abstract: Figure 1. This 5.19 ct diamond with I color and I2 clarity displays numerous etch channels visible to the eye. Photo by Annie Haynes.
The authors recently examined a 5.19 ct type IIa natural diamond (figure 1) displaying numerous etch channels (figure 2). Etch channels are open tubes whose formation is related to dissolution processes within the stone. They form due to the dissolution of dislocations inside the crystal during or after growth and can result in various patterns; most commonly, they form as trigons or rarely as channels that appear as parallel lines, zigzags, or “worm-like” structures (T. Lu et al., “Observation of etch channels in several natural diamonds,” Diamond and Related Materials, Vol. 10, 2001, pp. 68–75, and references therein; Spring 2018 G&G Micro-World, pp. 66–67). Etch channels terminate at typically rhombic openings visible at the surface of the stone (Spring 2018 G&G Micro-World, pp. 66–67). The extensive network of etch channels in this diamond resulted in an I2 clarity grade.

Figure 2. A network of natural etch channels gives this diamond a distinctive appearance. Most of the channels have a width of ~100–150 μm, while some (e.g., lower left) show evidence of brown radiation stains. Photomicrograph by Nathan Renfro; field of view 4.69 mm.

Figure 3. Left: False-color map showing the peak area intensity of the radiation-related TR12 center (ZPL at 469.9 nm); this 455 nm PL map was compiled from 18,768 spectra collected at 45 μm pixel size. Right: The false-color map overlain with a reflected light image of the table facet. Most of the etch channels seen in the false-color map correspond with an opening observed on the table.
Photoluminescence (PL) mapping using 455 and 532 nm laser excitation (figures 3 and 4) revealed an increase in the GR1, 3H, and TR12 centers along the walls of the etch channels; all of these centers are defects associated with radiation exposure. The nitrogen vacancy centers NV0 (zero-phonon line [ZPL] at 575 nm) and NV– (ZPL at 637 nm) were also concentrated along these channels. The concentration of these defects along the etch channels suggests that radioactive fluids once flowed through the tubes. The radioactive fluids had an impact on the areas in direct contact, creating elevated concentrations of radiation-related peaks. Other prominent PL peaks along the cavities were centered at 474, 598.75, and 461.5 nm. The radiation in these fluids would have been low enough to not create much observable staining, as patches of green to brown color associated with radiation staining were not observed in most of the etch channels. However, there were some isolated spots of green radiation stains and some channels with a brownish appearance (figure 2) and elevated concentrations of radiation-related features (figures 3 and 4). Additionally, the exposure to radioactive fluids must have occurred after the diamond was brought to the near-surface region following kimberlite eruption, as these radiation-related features would not withstand the high temperatures within the mantle.

Figure 4. GR1/Raman peak area ratios calculated from the 532 nm PL map (inset) cutting across multiple channels along the orange line. Higher GR1/Raman areas are concentrated along the etch channels.
Similar radiation features have previously been observed in another stone with cavities (Spring 2020 Lab Notes, pp. 126–127), but to a much lesser degree. The extensive network of etch channels within this diamond is one more example of the extraordinary possibilities within the natural world. @topic:4


Publish Year: 2022 Title: The Type IIb De Beers Cullinan Blue Diamond Abstract: Figure 1. The 15.10 ct De Beers Cullinan Blue diamond. Photo by Towfiq Ahmed.
Type IIb blue diamonds are extremely rare in nature. When people think of blue diamonds, the Hope diamond immediately springs to mind. The famed 45.52 ct Fancy Deep grayish blue cushion-cut treasure, now housed in the Smithsonian National Museum of Natural History in Washington, DC, has a long and fascinating history. First examined by GIA in 1960 and graded by GIA in 1988 (R. Crowningshield, “Grading the Hope diamond,” Summer 1989 G&G, pp. 91–94), it shares many special gemological characteristics with other rare type IIb (boron-containing) diamonds such as the Wittelsbach-Graff, once assumed to be cut from the same rough crystal as the Hope. Here we report another special diamond of this group.

De Beers Cullinan Blue Diamond

Recently graded by GIA and the recipient of a special monograph report was a 15.10 ct (17.47 × 11.53 × 7.94 mm) Fancy Vivid blue cut-cornered rectangular step cut. Named the De Beers Cullinan Blue diamond (figure 1; see video), it was cut from a 39.34 ct rough type IIb diamond crystal mined by Petra from the Cullinan (formerly Premier) mine in South Africa. Compared to the Hope and Wittelsbach-Graff, both of which were mined in the Golconda region of India, the De Beers Cullinan Blue has some important similarities in gemological and spectroscopic features but shows clear variations. Natural type IIb blue diamonds over 10 carats are exceedingly rare.
The blue color is distributed evenly throughout the stone. Visual observation under a gem microscope revealed a very clean stone. No inclusions or graining were observed. Accordingly, the diamond received a clarity grade of Internally Flawless. Under conventional long-wave and short-wave UV radiation, it showed no observable fluorescence or phosphorescence. This feature is dramatically different from that of the Hope and Wittelsbach-Graff, two large type IIb blue diamonds that exhibit strong and prolonged red phosphorescence to conventional short-wave UV radiation.

Figure 2. The mid-infrared spectrum of the type IIb De Beers Cullinan Blue
diamond.
The absorption spectrum in the mid-infrared region showed typical absorption features related to boron in diamond, such as strong absorption at ~2800 cm–1 and a weak absorption peak in the range of 1332–1200 cm–1 (figure 2). The intensities of these absorptions indicated a high concentration of uncompensated boron of ~0.33 ppm. Natural type IIb diamonds typically contain 0.24–0.36 ppm (E. Gaillou et al., “Study of the Blue Moon diamond,” Winter 2014 G&G, pp. 280–286). The diamond’s boron concentration is close to that of the Hope (~0.36 ppm) and higher than that of the Wittelsbach-Graff (~0.19 ppm). Absorption from boron is the main contributor of color in natural type IIb diamonds.

Figure 3. Observed with cross-polarized light was a strong tatami strain pattern with a dark gray color. Photo by Madelyn Dragone.
Observation with a gemological microscope equipped with crossed polarizers revealed a clear tatami pattern with a dark gray color (figure 3). Both the Wittelsbach-Graff and the Hope have different patterns and higher interference colors, a good indication that the De Beers Cullinan Blue has a much less distorted lattice structure. Under very strong short-wave UV, this diamond showed a weak aqua blue fluorescence with a subtle network of dislocations in the crystal structure, a pattern clearly different from the tight mosaic patterns observed in the Hope and the Wittelsbach-Graff (figure 4) (Gaillou et al., 2014).

Figure 4. Under very strong short-wave UV, a weak aqua blue fluorescence with a subtle network of dislocations was observed (top). After exposure, a weak pinkish red phosphorescence was observed (bottom). Images by Stephanie Persaud.
These blue diamonds are among the rarest of gems. Recent research (E. Smith et al., “Blue boron-bearing diamonds from Earth’s lower mantle,” Nature, Vol. 560, No. 7716, 2018, pp. 84–87) has demonstrated that their boron derived from pieces of the earth’s crust sinking to the extremely deep depths of diamond formation. The gemological characteristics of the De Beers Cullinan Blue suggest it is one of these superdeep diamonds. Its combination of Fancy Vivid blue color grade in a step cut (a cut that does not enhance color, unlike other faceting styles) (see video), 15.10 ct weight, and Internally Flawless clarity grade is exceptionally rare. It will remain one of the world’s most important diamonds. @topic:10


Publish Year: 2022 Title: Smithsonian’s Great American Diamonds Exhibit Abstract: Left: The 16.87 ct Freedom, from Kelsey Lake in Colorado, is the largest faceted diamond from the U.S. Right: The 12.42 ct Uncle Sam is the largest faceted diamond from Arkansas, cut from a 40.23 ct crystal uncovered at the Crater of Diamonds. Photo by James Tiller and Brittany M. Hance; courtesy of Department of Mineral Sciences, Smithsonian Institution.
Two extraordinary American diamonds (see above) have found a home at the Smithsonian’s National Museum of Natural History, where they were unveiled as part of the new Great American Diamonds exhibit in June. The 16.87 ct Freedom diamond, the largest faceted diamond of U.S. origin, was fashioned from a 28 ct crystal unearthed at Colorado’s Kelsey Lake mine in 1997. The cushion-cut diamond is now set in a ring donated by Robert E. and Kathy G. Mau. The second diamond on exhibit, the emerald-cut Uncle Sam, was faceted from the largest uncut American diamond crystal ever discovered at 40.23 ct. Uncovered at Arkansas’ Crater of Diamonds in 1924, the flawless 12.42 ct pinkish brown stone was recently recovered from a private collection (after being missing for decades) and donated by Peter Buck. This is the first time the Uncle Sam has been exhibited in more than 50 years.
While diamonds from the United States are exceptionally rare, the two mines in Colorado and Arkansas produced tens of thousands of carats of rough diamonds, from 1919 to 1926 at the Crater of Diamonds and 1996 to 2001 at Kelsey Lake. “Most people are surprised to learn that diamonds have been mined in the United States, and as the national museum, we are delighted to introduce these great American diamonds to our visitors,” said Dr. Jeffrey Post, the museum’s curator-in-charge of gems and minerals.
Joining these two impressive donations in the Great American Diamonds exhibit are two uncut diamonds from the museum’s existing collection. The Canary, a golden yellow crystal weighing 17.85 ct, is one of the largest uncut diamonds from Arkansas. The 6.45 ct Colorado, which displays the typical octahedral shape of a natural diamond crystal, was recovered from the kimberlite host rock during mining operations at Kelsey Lake. As part of the Smithsonian’s National Gem and Mineral Collection, these four stones are among more than 10,000 precious stones and pieces of jewelry, including the iconic Hope diamond. @topic:8


Publish Year: 2015 Title: Intense Blue Diamond with Very High Boron Concentration Abstract: Figure 1. This 1.18 ct Fancy Deep blue diamond was recently seen in the New York lab. Photo by Jian Xin (Jae) Liao.

Natural blue diamonds are extremely rare in nature and highly desired within the gem industry. One of the world’s most famous gemstones, the Hope diamond, is classified as a natural type IIb blue diamond. It contains the impurity boron within the diamond carbon lattice. The presence of boron as an impurity in natural diamond is rare, as the amount of uncompensated boron found is typically less than 0.5 ppm.

Housed in the Smithsonian Institute in Washington, DC, the Hope is part of a collection incorporating many boron-containing natural type IIb diamonds, and has been part of a study relating boron concentrations and the intensity of blue coloration in natural and synthetic diamond (E. Gaillou et al., “Boron in natural type IIb blue diamonds: Chemical and spectroscopic measurements,” American Mineralogist, Vol. 97, 2012, pp. 1–18).

The East Coast laboratory recently received a 1.18 ct Fancy Deep blue diamond (figure 1) for a colored diamond grading report. The diamond’s old European-style cut indicated that this was not a recently faceted gemstone. The clarity was very high, adding to the rarity of this blue diamond. When exposed to short-wave UV fluorescence (about 230 nm), the diamond displayed blue phosphorescence (figure 2). Phosphorescence is a diagnostic feature of natural type IIb diamonds; red phosphorescence is also frequently observed, the most notable example being the Hope diamond.

Figure 2. Blue phosphorescence was observed in the DiamondView after the stone’s exposure to strong short-wave UV radiation. DiamondView image by Paul Johnson.
Infrared absorption spectroscopy identified the diamond as type IIb, with a very high concentration of uncompensated boron for a natural diamond, even for a stone with synthetic boron doping (figure 3). Further analysis, including photoluminescence spectroscopy, proved it to be a natural diamond. From the mid-infrared absorption spectrum, we determined a boron concentration of 5.84 ppm atomic. By normalizing the mid-IR spectrum, we obtained the integrated intensity of an absorption peak centered at 1290 cm–1 (A.T. Collins, “Determination of the boron concentration in diamond using optical spectroscopy,” Proceedings of the 61st Diamond Conference, 2010, Warwick, UK). Most documented type IIb diamonds in this color range only have recorded uncompensated boron concentrations between approximately 0.24 and 0.36 ppm (E. Gaillou et al., “Study of the Blue Moon diamond,” Winter 2014 G&G, pp. 280–286).

Figure 3. Normalized mid-IR absorption spectrum of the 1.18 ct Fancy Deep blue type IIb diamond, with saturated boron–related absorption and a 1290 cm–1 peak.
This is the highest boron concentration ever reported in a natural diamond. Compared to other documented type IIb diamonds, the concentration is staggeringly high. This diamond’s intense blue color rivals that of the Hope, leading one to believe that boron contributes strongly to the color of natural blue type IIb diamonds. This has never been proven, however, and there is not a well-defined relationship between blue color and uncompensated boron concentration in diamond (Gaillou et al., 2012).

Further observation and analytical study may prove a correlation between optically active boron and the intensity of blue color in natural diamonds. @topic:4


Publish Year: 2018 Title: Type IIa Diamond with Extraordinary Etch Channels Abstract: Figure 1. A rare 1.77 ct type IIa diamond with significant etch channels caused by dissolution along dislocations. Photo by Aurélien Delaunay.

Etch channels are rare inclusions in natural diamonds, both type I and type II (see T. Lu et al., “Observation of etch channels in several natural diamonds,” Diamond and Related Materials, Vol. 10, No. 1, 2001, pp. 68–75). Recently, the Laboratoire Français de Gemmologie received a 1.77 ct round brilliant-cut diamond containing numerous large etch channels, a feature appreciated by inclusion collectors. The gem had K color and I1 clarity due to the etch channels and their reflectors (figure 1). Infrared absorption spectroscopy revealed a type IIa diamond.

Figure 2. Etch channels with rhombic openings at the surface of the diamond. Photomicrograph by Aurélien Delaunay; field of view 2.22 mm.

Figure 3. Rare etch channel with a pyramidal termination in a 1.77 ct type IIa diamond. Note the lateral continuation of the dissolution. Photomicrograph by Aurélien Delaunay; field of view 1.39 mm.
Dissolution etch channels in diamond are rare but can have various forms (M. Philippe and E. Fritsch, “Dissolved dislocation: Inclusions not always easy to identify, part I,” Revue de Gemmologie, Vol. 200, 2017, pp. 11–22, in French). They are due to the dissolution of dislocations inside the crystal. These dislocations might be growth dislocations or caused by later deformation. One type of etch channel in diamond consists of regular and parallel lines related to diamond’s crystallographic structure. The other type, the kind exhibited in this diamond, is a worm-like ribbon due to crystallographic defects. All dissolution etch channels have rhombic openings at the surface of the diamond (figure 2); a few have a pyramidal termination and restart in another direction (figure 3). This is a rare occurrence and confirms that dissolution can be stopped—or slowed—by defects in the crystal structure. In addition, the dissolution can start in an easier direction, such as a dislocation.

Etch channels are rarely observed in cut gem diamonds. But when gemologists observe a specimen like this one, it is always a pleasure for the eyes and a curiosity of nature. @topic:4


Publish Year: 2022 Title: HPHT-Processed Natural Type Ia Diamond Abstract: Figure 1. This 5.17 ct Fancy Deep yellow-orange HPHT-treated diamond was resubmitted to the New York laboratory. Photo by Towfiq Ahmed.
There are two types of high-pressure, high-temperature processes related to diamond: HPHT treatment and HPHT diamond growth. HPHT laboratory-grown diamonds were developed in the mid-1950s, with the first gem-quality production in the early 1970s and extensive production beginning in the 1990s.
HPHT treatment to change the color of natural diamonds was discovered as a byproduct of annealing natural diamond anvils. The General Electric Company (GE) and Lazare Kaplan International marketed the first commercial HPHT-treated color diamonds in March 1999 (K. Schmetzer, “Clues to the process used by General Electric to enhance the GE POL diamonds,” Winter 1999 G&G, pp. 186–190). The same machines, such as a hydraulic press that produces extremely high pressure and temperature environments, are also used to treat both mined and laboratory-grown diamonds. HPHT treatment can change the color of diamonds or make them colorless.

Figure 2. Table-down images showing the diamond before HPHT treatment (left) and after (right).

Figure 3. This natural anhedral crystal was formed during diamond growth and acquired a graphitized halo after HPHT treatment. Photomicrograph by Sally Ruan; field of view approximately 1.26 mm.
A natural 5.20 ct type Ia SI2 Fancy Dark yellowish brown diamond with natural anhedral crystal inclusions was submitted to the New York laboratory for grading services and returned. After being treated, it was resubmitted as a 5.17 ct type Ia SI2 Fancy Deep yellow-orange diamond (figure 1), with the disclosure that it had been HPHT processed. After analysis, the diamond was confirmed to have been treated using an HPHT process that changed the color from a dark yellowish brown to a deep yellow-orange (figure 2). After the HPHT process, each of the natural anhedral crystal inclusions developed a graphitized halo (figure 3). In the natural diamond, the visible/near-infrared (Vis-NIR) absorption spectrum showed a slight 550 nm band—a feature that may impart a pinkish color component depending on its absorbance and other features present within the diamond. After HPHT treatment, there is instead an increase in absorption from ~500 nm toward the lower wavelengths; this absorption rise is due to the creation of single, isolated nitrogen (figure 4).

Figure 4. Vis-NIR spectra show the untreated natural diamond with the 550 nm band (orange line). After HPHT treatment (blue line), the 550 nm band is not apparent. Instead, there is an increase in absorption from 500 nm toward the lower wavelengths (higher energy). Spectra are offset for clarity.

Figure 5. The B region of the mid-infrared spectrum shows a new isolated nitrogen peak at 1344 cm–1 and a diminished ~1363 cm–1 platelet peak after HPHT processing (orange line). The A region of the mid-infrared shows that the natural amber center at ~4165 cm–1 (shown in orange) was destroyed after HPHT processing. The spectra are baseline corrected.
As expected (I.M. Reinitz et al., “Identification of HPHT-treated yellow to green diamonds,” Summer 2000 G&G, pp. 128–137), FTIR data from after the HPHT treatment showed that a peak associated with isolated nitrogen at 1344 cm–1 was introduced, the ~1363 cm–1 platelet peak was diminished, and the natural amber center at ~4165 cm–1 was destroyed (figure 5). Since the spectroscopic data changed after treatment, crystal inclusions plotted on the original grading diagram for this diamond confirmed it was the same stone. The 550 nm band in the Vis-NIR absorption spectrum related to a pink or brown diamond is stable at lower temperatures of HPHT treatment. Since the 550 nm band was not detected after the process, we believe this diamond was treated at the higher end of the HPHT regime or for a prolonged duration that required repolishing, which caused it to lose three points of carat weight.
While there are many different treatments that can be performed on diamonds, HPHT treatments are permanent and require a stable and controlled environment. In this stone, the treatment resulted in some of the nitrogen aggregates being split apart into single, isolated nitrogen that introduced new color centers and altered the color of the treated stone. The treatment also graphitized inclusions; however, this change was not sufficient to lower the clarity grade. As technology advances, HPHT treatments are becoming more common for both natural and laboratory-grown diamonds. @topic:4


Publish Year: 2022 Title: Unusual Laser Drill Holes in a Laboratory-Grown Diamond Abstract: Figure 1. Flux inclusion in a laboratory-grown diamond connected to a laser drill hole. Photomicrograph by Najmeh Anjomani; field of view 3.57 mm.
Diamonds with dark inclusions have been laser drilled to enhance their clarity for more than 60 years. The internal inclusion is drilled from the diamond surface and then acid-boiled to bleach it out. GIA has identified many natural diamonds treated by this technique, but the Carlsbad laboratory recently received for a colored diamond identification and origin report an undisclosed laboratory-grown diamond with unusual laser drill holes.
The diamond was a Fancy yellow cushion modified brilliant weighing 2.02 ct. Gemological and spectroscopic analysis confirmed it was an HPHT-grown synthetic diamond. The diamond was attracted to a small magnet due to the numerous metallic inclusions. No strain was visible under crossed polarizers, and DiamondView imaging showed the typical cuboctahedral HPHT growth pattern.
Clarity was low due to the presence of numerous large flux inclusions, so laser drilling was likely done to enhance the appearance and clarity. One of the laser drill holes connected to a large flux inclusion can be seen in figure 1. A metallic flux inclusion cannot be bleached as some mineral inclusions can and so it must be dissolved out, which could pose additional challenges to improving the clarity. It appears there was an unsuccessful attempt to remove the flux, as the inclusion was still eye visible.

Figure 2. Clusters of unusual laser drill holes in a laboratory-grown diamond. Photomicrographs by Najmeh Anjomani; fields of view 3.57 mm (left) and 2.61 mm (right).
Three clusters of intersecting laser drill tubes resembling corals were observed (figures 2 and 3). We could see numerous roundish openings on the surface filled with dark materials. Raman spectroscopy confirmed they were all non-diamond carbon materials. Here the laser beam was likely reflected off a flux inclusion and refocused to a new point farther than intended, resulting in the unusual branching pattern. Other flux inclusions could have been successfully dissolved by acid because they were smaller than the one in figure 1 or because there were more drilled tubes for the acid to enter. This may have caused the unique crossed tubes inside the stone. Burn marks on the surface next to some of the laser drill holes might have been due to the heat generated by the laser beam (figure 3).

Figure 3. Burn mark on the surface next to laser drill holes. Photomicrograph by Najmeh Anjomani; field of view 2.01 mm.
This diamond was identified as a laboratory-grown diamond. It was issued a laboratory-grown colored diamond report stating, “Laser drill holes are present.” @topic:4


Publish Year: 2022 Title: Large Green and Yellow Diamonds Colored by Nickel Impurities Abstract: Figure 1. Large gem diamonds with strong color saturations resulting from nickel-related impurities. Top: 5.02 ct Fancy Intense green-yellow cushion. Bottom left: 5.03 ct Fancy yellow-green pear. Bottom right: 5.06 ct Fancy Intense green-yellow pear. Photos by Diego Sanchez.
Diamonds colored by nickel impurities were previously thought to only occur in lower carat weights and with weaker color saturations. However, the Carlsbad laboratory recently received several large examples with strongly saturated color. Among the stones examined, a Fancy Intense green-yellow cushion weighing 5.02 ct, a Fancy yellow-green pear weighing 5.03 ct, and a Fancy Intense green-yellow pear weighing 5.06 ct were the most notable (figure 1).

Figure 2. Vis-NIR spectra collected from each diamond show a strong asymmetrical absorption band around 670 nm along with a distinct peak at 883 nm. These defects together, with the lack of any other color-causing defects, indicate that nickel is the main cause of color.
Gemologically, these diamonds were mostly free of inclusions except for faint internal graining and small reflective platelets. Along with natural inclusions, FTIR spectra showed that all three stones were type IaA, confirming that these are naturally mined diamonds and not of synthetic origin. Vis-NIR spectra revealed an asymmetrical absorption band around 670 nm and a notable peak at 883 nm for all three (figure 2). These features in the UV-Vis-NIR strongly suggest that the color is caused by the presence of nickel-related defects.
Previously, the largest and most intensely colored gem diamonds reported to have been colored by nickel defects were a 2.54 ct Fancy Light greenish yellow diamond (see Fall 2013 Lab Notes, pp. 173–174) and a 2.81 ct Fancy Intense yellowish green diamond (W. Wang et al., “Natural type Ia diamond with green-yellow color due to Ni-related defects,” Fall 2007 G&G, pp. 240–243).
The stones described in the present report are nearly twice as large and have significantly more saturated hues. Therefore, it appears that nickel-colored diamonds can occur over a wider range of sizes and color saturations than previously suspected. @topic:4


Publish Year: - Title: The Type IIb De Beers Cullinan Blue Diamond Abstract: Figure 1. The 15.10 ct De Beers Cullinan Blue diamond. Photo by Towfiq Ahmed.
From the Summer 2022 issue of Gems & Gemology
Type IIb blue diamonds are extremely rare in nature. When people think of blue diamonds, the Hope diamond immediately springs to mind. The famed 45.52 ct Fancy Deep grayish blue cushion-cut treasure, now housed in the Smithsonian National Museum of Natural History in Washington, DC, has a long and fascinating history. First examined by GIA in 1960 and graded by GIA in 1988 (R. Crowningshield, “Grading the Hope diamond,” Summer 1989 G&G, pp. 91–94), it shares many special gemological characteristics with other rare type IIb (boron-containing) diamonds such as the Wittelsbach-Graff, once assumed to be cut from the same rough crystal as the Hope. Here we report another special diamond of this group.

Recently graded by GIA and the recipient of a special monograph report was a 15.10 ct (17.47 × 11.53 × 7.94 mm) Fancy Vivid blue cut-cornered rectangular step cut. Named the De Beers Cullinan Blue diamond (figure 1 and the video clip below), it was cut from a 39.34 ct rough type IIb diamond crystal mined by Petra from the Cullinan (formerly Premier) mine in South Africa. Compared to the Hope and Wittelsbach-Graff, both of which were mined in the Golconda region of India, the Cullinan has some important similarities in gemological and spectroscopic features but shows clear variations. Natural type IIb blue diamonds over 10 carats are extremely rare.

Blue color is distributed evenly throughout the stone. Visual observation under a gem microscope revealed a very clean stone. No inclusions or graining were observed. Accordingly, the diamond received a clarity grade of Internally Flawless. Under conventional long-wave and short-wave UV radiation, it showed no observable fluorescence or phosphorescence. This feature is dramatically different from that of the Hope and Wittelsbach-Graff, two large type IIb blue diamonds that exhibit strong and prolonged red phosphorescence to conventional short-wave UV radiation.

Figure 2. The mid-infrared spectrum of the type IIb De Beers Cullinan Blue diamond.
The absorption spectrum in the mid-infrared region showed typical absorption features related to boron in diamond, such as strong absorption at ~2800 cm–1 and a weak absorption peak in the range of 1332–1200 cm–1 (figure 2). The intensities of these absorptions indicated a high concentration of uncompensated boron of ~0.33 ppm. Natural type IIb diamonds typically contain 0.24–0.36 ppm (E. Gaillou et al., “Study of the Blue Moon diamond,” Winter 2014 G&G, pp. 280–286). The diamond’s boron concentration is close to that in the Hope (~0.36 ppm) and higher than that in the Wittelsbach-Graff (~0.19 ppm). Absorption from boron is the main contributor of color in natural type IIb diamonds.

Figure 3. Observed with cross polarized light was a strong tatami strain pattern with a dark gray color. Photo by Madelyn Dragone.

Figure 4. Under very strong short-wave UV, a weak aqua blue flourescence with a subtle network of dislocations was observed (top). After exposure, a weak pinkish red phosphorescence was observed (bottom). Images by Stephanie Persaud.
Observation with a gemological microscope equipped with crossed polarizers revealed a clear tatami pattern with a dark gray color (figure 3). Both the Wittelsbach-Graff and the Hope have different patterns and higher interference colors, a good indication that the De Beers Cullinan Blue has a much less distorted lattice structure. Under very strong short-wave UV, this diamond showed a weak aqua blue fluorescence with a subtle network of dislocations in the crystal structure, a pattern clearly different from the tight mosaic patterns observed in the Hope and the Wittelsbach-Graff (figure 4) (Gaillou et al., 2014).

	The Type IIb De Beers Cullinan Blue Diamond

These blue diamonds are among the rarest of gems. Recent research (E. Smith et al., “Blue boron-bearing diamonds from Earth’s lower mantle,” Nature, Vol. 560, No. 7716, 2018, pp. 84–87) has demonstrated that their boron derived from pieces of the earth’s crust sinking to the extremely deep depths of diamond formation. The gemological characteristics of the De Beers Cullinan Blue suggest it is one of these superdeep diamonds. Its combination of Fancy Vivid blue color grade in a step cut (a cut that does not enhance color, unlike other faceting styles) (see video), 15.10 ct weight, and internally flawless clarity grade is exceptionally rare. It will remain one of the world’s most important diamonds. @topic:10


Publish Year: - Title: New Record Size for CVD Laboratory-Grown Diamond Abstract: Figure 1. The new record size for CVD laboratory-grown diamond—16.41 ct, with G color and VVS2 clarity—has been achieved by Shanghai Zhengshi Technology Co. Ltd. This is an as-grown diamond; no post-growth treatment was applied for color improvement, either before or after faceting. Photo by Towfiq Ahmed.
Growth technology of single-crystal diamond has advanced significantly in the last two decades, for both the high-pressure, high-temperature (HPHT) and chemical vapor deposition (CVD) methods. In addition to many other applications, laboratory-grown diamonds have become an expanding segment of the jewelry industry. Records for crystal size and quality are frequently broken. In this note, GIA’s New York laboratory reports on a new record for CVD laboratory-grown diamond.
This princess-cut diamond produced by Shanghai Zhengshi Technology Co. Ltd. (figure 1; GIA report number 2225246686) weighed 16.41 ct and measured 13.97 × 13.87 × 9.56 mm, with G color and VVS2 clarity. The strong graining distributed throughout it created a “wavy” appearance (view the video clip below). In addition, a few tiny pinpoints were present. Absorption spectroscopy in the infrared region revealed this was a typical type IIa diamond. Except for absorptions from the diamond itself, no other defect-related absorption was detected in this region. Photoluminescence spectroscopy collected at liquid nitrogen temperature with 514 nm laser excitation (figure 2, left) showed emissions from NV centers with zero-phonon lines (ZPL) at 575.0 nm and 637.0 nm with moderate intensities. Clear emissions from SiV– at 736.6 and 736.9 nm were detected. Weak emissions at 596 and 597 nm, which are specific to CVD diamond and also unstable at high temperature, were recorded overlapping with side bands of the NV0. Photoluminescence spectroscopy with 457 nm laser excitation (figure 2, right) detected weak emissions at 503.5 nm (3H) and 467.6 nm. Similar to the emission at 596 and 597 nm, the 467.6 nm center is CVD-specific and would be annealed out at very high temperature. No emission from the H3 defect was observed. All these spectroscopic features confirmed this was a CVD diamond with no post-growth treatment to improve the color.

Figure 2. Left: The photoluminescence spectrum with 514 nm laser excitation under liquid nitrogen temperature showed typical features of as-grown CVD diamond. Right: In the photoluminescence spectrum with 457 nm laser excitation under liquid nitrogen temperature, weak emissions from the 3H defect and from the 467.6 nm center were recorded.

	New Record Size for CVD Laboratory-Grown Diamond

Images collected under deep short-wave UV excitation showed strong orange-red fluorescence with banded blue regions (figure 3). The blue “columns” were nearly perpendicular to the table and extended almost continuously to the pavilion and culet. This feature was consistent with both the strong lattice dislocations observed under the microscope with crossed polarizers (figure 4) and its observable graining. Up to seven growth steps were revealed in the fluorescence and cathodoluminescence images (figure 5), with each layer of similar thickness. This princess-cut diamond had been faceted with its table face parallel to these layers for maximum weight retention, while keeping excellent proportions and symmetry.

Figure 3. Fluorescence imaging with deep short-wave UV excitation showed the typical orange-red fluorescence of as-grown CVD diamond with irregular blue “banding.” Up to seven growth layers were revealed. Image by Stephanie Persaud.

Figure 4. The large CVD diamond showed very strong dislocations under crossed polarizers, the main cause of its wavy appearance. Photo by Stephanie Persaud.

Figure 5. Cathodoluminescence imaging also revealed the seven growth steps. The dark dots in this image are related to the lattice dislocations. Image by Elina Myagkaya.
For CVD growth, this 16.41 ct diamond broke the record previously held by a 14.60 ct diamond (emerald cut, F color, VS2 clarity) produced in India, which surpassed the previous record of 12.75 ct (round brilliant, F color, VVS2 clarity), both reported last year (“IGI certifies world record 14.60 ct lab grown diamond,” IGI GemBlog, August 31, 2021). In comparison, the largest colorless or near-colorless HPHT laboratory-grown diamond is 15.32 ct (cushion cut, H color, I1 clarity), tested by GIA in 2018. The largest laboratory-grown diamond of any kind tested by GIA so far is a fancy-color 20.23 ct cushion cut (Fancy Vivid yellowish orange, VS2) produced using the HPHT method in 2019. GIA will continue to follow the development of laboratory-grown diamonds to ensure that all are properly identified. @topic:4


Publish Year: 2021 Title: Expanded Diamond Surface Due to Radiation Staining Abstract: Figure 1. Dark green radiation stains on a natural diamond surface. This is a partially faceted diamond with some of its natural surface bounded by laser markings, seen as dark lines in the image. Photomicrograph by Nathan Renfro; field of view 2.24 mm.

The author examined a 0.56 ct Fancy grayish bluish green diamond with prominent green radiation stains. Studies have shown that radiation can cause staining that expands the surface of a diamond (L. Nasdala et al., “Radio-colouration of diamond: A spectroscopic study,” Contributions to Mineralogy and Petrology, Vol. 165, 2013, pp. 843–861; S.C. Eaton-Magaña and K.S. Moe, “Temperature effects on radiation stains in natural diamonds,” Diamond and Related Materials, Vol. 64, 2016, pp. 130–142). This can create a noticeable bump that is visible in the microscope. The effect in this diamond is so pronounced that the radiation stains appear encased in a protective plastic bubble. This expansion effect is believed to be caused by the radiation damage creating an expansion in the diamond lattice (Nasdala et al., 2013).

Figure 2. The radiation stains on a natural surface in reflected light, which highlights the smooth texture of the stained and expanded areas. Photomicrograph by Nathan Renfro; field of view 2.24 mm.
When viewed with transmitted light (figure 1), the raised lattice can be seen extending beyond the dimensions of the stain itself. The green-colored stains are very dark. Using reflected light (figure 2), the difference between surface textures is apparent. The surface that has been damaged and expanded by the radiation staining has a much smoother texture than the unaltered diamond surface. It is unknown why this diamond lattice was so distorted compared to typical radiation stains; they showed no unusual spectroscopic features that might provide a clue as to their formation. @topic:4


Publish Year: 2021 Title: Historic Sales of Pink and Blue Diamonds from the Argyle Mine Abstract: Figure 1. Five diamonds that headlined the final Argyle pink diamond tender, titled “The Journey Beyond.” Courtesy of Rio Tinto.
In October 2021, nearly one year after the end of operations at the Argyle mine in Western Australia, Rio Tinto sold its final production of pink and blue diamonds. The company announced that the 37th Argyle pink diamond tender collection of 70 rare pink and red diamonds delivered record-breaking prices across individual diamonds and for the overall collection. This year’s edition was conducted in a series of virtual and face-to-face viewings. Highlights from the sale (shown left to right in figure 1) were the 2.03 ct Fancy Deep pink Argyle Lumiere, the 1.79 ct Fancy Vivid purplish pink Argyle Stella, the 2.05 ct Fancy Intense pink Argyle Solaris, the 3.47 ct Fancy Intense pink Argyle Eclipse, and the 1.01 ct Fancy red Argyle Bohème. (For more on Argyle’s pink diamond sales, see J.M. King et al., “Exceptional pink to red diamonds: A celebration of the 30th Argyle diamond tender,” Winter 2014 G&G, pp. 268–279.)

Figure 2. A selection of blue and violet diamonds from Rio Tinto’s “Once in a Blue Moon” tender. Courtesy of Rio Tinto.
Along with the pink diamond tender, Rio Tinto sold its final collection of Argyle blue and violet diamonds (figure 2), which the mine has produced sporadically over the years (see C.H. van der Bogert et al., “Gray-to-blue-to-violet hydrogen-rich diamonds from the Argyle mine, Australia,” Spring 2009 G&G, pp. 20–37). The entire lot of 41 diamonds totaling 24.88 carats was purchased by a single bidder. @topic:7


Publish Year: 2021 Title: Novelty Cut Diamond Faceted as Iconic Apple Logo Abstract: Figure 1. This 1.13 ct Fancy yellow diamond resembles the iconic Apple logo. Photo by Diego Sanchez.

A novelty cut 1.13 ct Fancy yellow diamond was recently submitted to the Carlsbad laboratory for color origin and identification service. The diamond was cut in the shape of a bitten apple and bore a striking resemblance to the iconic Apple logo found on Apple Inc. products (figure 1). Standard FTIR absorption spectrum identified it as a type Ia diamond with high nitrogen concentration. Standard UV-Vis spectroscopy revealed the typical UV-Vis absorption spectra of cape diamond, with the N2 (478 nm) and N3 (415.2 nm) defects that are responsible for the fancy yellow color in the “Apple” diamond. The stone showed strong blue fluorescence when exposed to long-wave UV radiation, typical of cape diamond (figure 2).

Figure 2. The novelty cut diamond showed strong blue fluorescence under long-wave UV light. Photo by Diego Sanchez.
New cutting styles of diamonds are often designed either for efficient light return and weight retention properties or to resemble other items. Examples of the latter include the sword-shaped diamond with “fire and ice” fluorescence (Fall 2020 Lab Notes, pp. 416–419) and the “seated Buddha” (Fall 1996 Gems News, p. 215). This particular diamond was most likely fashioned in the shape of an apple as a novelty and to retain weight, as the stone showed significant windowing, which suggests that the rough was too shallow to allow for more efficient light return. This unique shape for a faceted diamond is a welcome addition to the wide range of novelty cut diamonds currently available in the trade. @topic:4


Publish Year: 2021 Title: Faceted Octahedral Diamond with Octahedral-Shaped Inclusion Abstract: Figure 1. This natural 2.01 ct Fancy Light brownish greenish yellow diamond octahedron was faceted to highlight an octahedral-shaped cloud inclusion. Photo by Nathan Renfro.

Recently, the authors examined a 2.01 ct faceted diamond octahedron (6.28 × 5.98 × 7.14 mm) with a Fancy Light brownish greenish yellow color grade that showed a distinctive internal appearance (figure 1). Microscopic examination revealed an octahedral-shaped inclusion scene composed of minute inclusions and clouds. The faceting arrangement of the diamond was likely meant to highlight the octahedron.

Figure 2. The faceting pattern for this diamond includes four hexagonal facets that provide a window of the octahedral-shaped inclusion. From this viewing angle, the octahedron resembles a six-pointed star. Photomicrograph by Nathan Renfro; field of view 4.69 mm.

	Faceted Octahedral Diamond with Octahedral-Shaped Inclusion

Viewed from one perspective, the hexagonal facet shows the internal octahedron in such a way that the inclusion scene resembles a six-pointed star (e.g., figure 2; see the video). Similar octahedral-shaped inclusions have been encountered before in natural diamonds (Winter 2015 Lab Notes, pp. 428–429; Spring 2011 Lab Notes, pp. 50–52).

Figure 3. This detail of one of the octahedron’s vertices indicates that the cloud comprises small inclusions. The portion of the octahedral cloud closest to the vertex within this image has a depth of approximately 1.8 mm below the hexagonal-shaped facet. Photomicrograph by Sally Eaton-Magaña; field of view 1.50 mm.
Oftentimes, such symmetrical clouds are dark-colored or gray (W. Wang and W. Mayerson, “Symmetrical clouds in diamond—The hydrogen connection,” Journal of Gemmology, Vol. 28, No. 3, 2002, pp. 143–152). These can also contain evidence of hydrogen, nickel-related defects, or graphite (S. Eaton-Magaña et al., “Inclusion and point defect characteristics of Marange,” Diamond and Related Materials, Vol. 71, 2016, pp. 20–29). At higher magnification, the individual inclusions that combine to create the cloud can be seen (figure 3).
The cloud inclusion resulted in an SI1 clarity grade. The diamond exhibited no fluorescence to long-wave UV and blue N3-related fluorescence within the diamond when exposed to the deep UV within the DiamondView. The cloud inclusion itself showed no distinctive fluorescence compared to the rest of the diamond. The IR absorption spectrum indicated the presence of strong nitrogen aggregates and a strong hydrogen peak at 3107 cm–1 associated with the N3VH defect. The visible/near-infrared absorption spectrum contained typical cape features and a hydrogen-related band at 835 nm. The hydrogen features detected in the IR and Vis-NIR absorption spectra correspond with the presence of the octahedral cloud inclusion.

Figure 4. Left: This false-color PL map was compiled from thousands of spectra (each pixel is 15 microns in size) and plots the intensity of a peak centered at 694 nm (associated with nickel and often seen in hydrogen clouds). The detection of this peak corresponds well with the hydrogen cloud. The data were collected with 532 nm excitation at liquid nitrogen temperature, and the peak intensity is normalized by ratioing to the diamond Raman peak. Right: These two spectra were collected from a “red” and “blue” portion of the PL map. The diamond Raman areas are scaled equally. The cloud inclusions indicated elevated concentrations of peaks that include those at 694 and 700.5 nm; outside of the inclusion, there are increased concentrations of NV– at 637 nm.
Spectroscopically, the most interesting results came from photoluminescence (PL) mapping of the octahedral-shaped cloud inclusion. This was performed at liquid nitrogen temperature using 532 and 455 nm excitations. Using 532 nm excitation, we saw elevated concentrations of peaks at 694 and 700.5 nm within the cloud inclusion (figure 4). The elevated concentrations of these peaks are consistent with previously characterized hydrogen clouds (e.g., Fall 2020 Lab Notes, pp. 416–419). The 694 and 700.5 nm peaks are ascribed to nickel and are often seen in hydrogen-rich diamonds (K. Iakoubovskii and G.J. Adriaenssens, “Optical characterization of natural Argyle diamonds,” Diamond and Related Materials, Vol. 11, No. 1, 2002, pp. 125–131). In the 455 nm PL mapping, a nickel-nitrogen-related defect at 496.7 nm called the S3 center (T. Hainschwang et al., “The Rhodesian Star: An exceptional asteriated diamond,” Journal of Gemmology, Vol. 34, No. 4, 2014, pp. 306–315) was also detected within the cloud. Outside of the inclusion, we detected higher concentrations of the NV– defect (principal emission at 637 nm).
While the faceting pattern dramatically highlights the octahedral-shaped inclusion to resemble a six-pointed star, the cloud is not confined to a narrow focal plane as it might appear in figures 1 and 2. Instead, the cloud spans throughout much of the volume of the faceted stone. Creative faceting by the polisher provides a unique perspective on the cloud inclusion that makes this unusual diamond even more memorable. @topic:4


Publish Year: 2021 Title: Laboratory-Grown Diamond with Internal Laser Markings Abstract: Figure 1. The 2.44 ct pear-cut CVD-grown diamond with internal spiral markings. Photo by Jian Xin Liao.
With the recent influx of laboratory-grown diamonds into the market and to aid consumer awareness of diamond origin, manufacturers are often marking their laboratory-created diamonds using internal inscriptions. The New York laboratory recently examined a 2.44 ct pear-shaped CVD (chemical vapor deposition) grown diamond with unusual internal spiral markings (figure 1).

Figure 2. Micro image of the largest spiral marking; the line thickness is 40 microns. Photomicrograph by Paul Johnson.
The three spiral markings were black and all in the same plane (i.e., at the same depth). The line thickness of these markings was about 40 microns (figure 2), whereas laser inscriptions are generally less than 20 microns. It was suspected that these markings were created by accidental laser damage rather than laser inscription. Raman mapping of the surface above the markings revealed a much broader diamond Raman peak compared to the rest of the crystal. This is the result of laser damage to the crystal lattice. Further Raman mapping using confocal settings identified a graphite peak at about 1620 cm–1. This offered proof that a laser, graphitizing the diamond, had created the markings.
The “inclusions” likely resulted from the laser marking the surface; this is done to provide a template to guide the polisher in producing the final shape. The intent would have been to score the surface; however, the laser appeared to have been inadvertently focused below the surface, resulting in the unusual internal markings.
As the markings are internal and graphitized, they are considered clarity features. The clarity grade was determined to be SI1, followed by a report comment stating, “Clarity grade is based on manufacturing remnants that are not shown.” @topic:4


Publish Year: 2021 Title: HPHT-Processed Diamond with Counterfeit GIA Inscription Abstract: Figure 1. Face-up view of the 1.497 ct, E-color HPHT-processed diamond submitted in 2021 for update service. Photo by Ellen Barrie.

In June 2021, GIA’s Antwerp lab received a diamond treated by high pressure and high temperature (HPHT) that was falsely inscribed with a GIA report number referencing an untreated diamond originally graded by GIA in 2010. The diamond was submitted for Update service, in which a stone is matched to its previous report and regraded based on its current condition. Careful comparison of the diamond with its accompanying report number showed that the weight and grading parameters were very similar, but certain differences readily led to the conclusion that this was not the same stone.
The HPHT-processed diamond was a round brilliant weighing 1.497 ct and measuring 7.30–7.34 × 4.50 mm (figure 1), while the original diamond weighed slightly more (1.502 ct) and measured 7.29–7.34 × 4.56 mm. They had the same clarity (IF) and fluorescence (none) but different color grades (D for the original diamond, E for the HPHT-processed diamond).
Additional conclusive differences were detected when the newly submitted stone was further analyzed with advanced spectroscopic techniques. Whereas the diamond from 2010 was type Ia, the submission from 2021 tested as type IIa. Photoluminescence (PL) spectroscopy using various laser excitation wavelengths confirmed a natural origin, but with color enhancement by HPHT treatment.

Figure 2. Remnants of the original GIA report number could still be detected on the girdle of the diamond (in addition to the fraudulent inscription, which is not pictured). Photomicrograph by Ellen Barrie.
In addition to a clearly fraudulent inscription (not pictured), microscopic examination of the girdle revealed remnants of an original GIA inscription (figure 2). Based on this information, we found that this HPHT-processed stone had already been submitted to GIA in 2013 but was repolished afterward in an attempt to obscure the original inscription. Our records showed that in 2013, the diamond was also inscribed with “BELLATAIRE” (indicating HPHT treatment), but this information had been removed from the girdle and the remnants were even less visible than the original GIA inscription.

Figure 3. “TREATED COLOR” was inscribed on the girdle after spectroscopic analysis confirmed that the color of the stone was enhanced by HPHT treatment. Photomicrograph by Ellen Barrie.
In addition to issuing a new report for this HPHT-treated diamond, GIA made the fraudulent inscription unreadable, according to standard procedure, and the stone was inscribed with “TREATED COLOR” (figure 3).
The Antwerp lab had recently reported a similar case of fraud, but that concerned a laboratory-grown diamond with a counterfeit inscription referencing a natural diamond (Summer 2021 Lab Notes, pp. 150–152). Both types of fraud are common in the marketplace and show the importance of careful verification of not only a diamond’s growth method (natural versus laboratory-grown) but also its color origin. @topic:4


Publish Year: 2021 Title: CVD Laboratory-Grown Diamond with Counterfeit GIA Inscription Abstract: Figure 1. This 3.07 ct CVD lab-grown diamond was submitted with a counterfeit GIA inscription that corresponded to a previously graded natural diamond. Photo by Ellen Barrie.

In recent months, GIA has seen a number of laboratory-grown diamonds submitted for update or verification services with counterfeit inscriptions referencing GIA natural diamond reports (“GIA laboratory prevents attempted fraud,” GIA press release, May 17, 2021, https://www.gia.edu/gia-news-press/gia-lab-prevents-attempted-fraud). One recent example is a 3.07 ct round brilliant submitted to the Antwerp lab for update service (figure 1). It bore an inscription matching a GIA report for a natural diamond that had been submitted in 2018. Microscopic examination quickly revealed, however, that the inscription was in fact fraudulent. Further analysis indicated a laboratory-grown origin.

Comparison showed an attempt to precisely match the laboratory-grown diamond to the information contained in the original report (table 1). Both were round brilliants with excellent cut properties and very close in carat weight and measurements. The natural diamond, however, did have a slightly better color and clarity (G-IF compared to H-VVS2). The clarity grade of the laboratory-grown diamond (VVS2) was set by two types of inclusions: pinpoints and needles.
Further analysis of the laboratory-grown diamond was performed using advanced spectroscopic techniques. Whereas the original diamond was type Ia and had a high concentration of nitrogen such that it saturated the detector in the one-phonon region (1335–1085 cm–1), Fourier-transform infrared (FTIR) analysis revealed that the newly submitted diamond was nominally type IIa. The spectrum showed the weak presence of isolated nitrogen at 1344 cm–1 and the absence of both the 3107 cm–1 and the CVD-specific NVH0 band at 3123 cm–1. Photoluminescence (PL) spectra taken with various laser excitation wavelengths and at liquid nitrogen temperature showed the strong presence of the SiV– doublet (736.6/736.9 nm), a defect commonly observed in CVD laboratory-grown diamonds. This strong SiV– center was also conspicuous in the UV-Visible absorption spectrum taken at liquid nitrogen temperature. Other defects detected with PL spectroscopy were strong NV0/– (575 and 637 nm) centers, a strong H3 (503.2 nm) center, and weak nickel-related defects (883/884 nm doublet).

Figure 2. DiamondView imaging confirmed CVD growth and subsequent HPHT treatment. Image by Ellen Barrie.
DiamondView imaging displayed a typical CVD growth structure with a green-blue layered pattern and banded layers, indicating a start-stop growth (figure 2). A weak greenish blue phosphorescence was observed after switching off the UV source.

Figure 3. In accordance with GIA procedures, the LABORATORY-GROWN inscription was added to the girdle (left) and the counterfeit report number inscription was rendered illegible (right). Photos by Ellen Barrie.
Based on all the observations, we concluded this was a CVD laboratory-grown diamond that had undergone HPHT treatment after growth. As with all laboratory-grown diamonds submitted to GIA, it was then inscribed with “LABORATORY-GROWN” (figure 3, left). The counterfeit inscription was overwritten (figure 3, right) and a new GIA report number was placed on the girdle.
This example demonstrates the importance of careful examination to verify a diamond’s origin. A close comparison of the CVD diamond with the earlier report on a natural diamond showed a very precise attempt at matching. @topic:4


Publish Year: 2018 Title: HPHT-Processed Diamond Fraudulently Represented as Untreated Abstract: This 6.30 ct round brilliant diamond (left) with a fraudulent inscription of a GIA report number (right) from a similar-looking diamond was confirmed to have been HPHT processed for color improvement. Photos by Tony Leung (left) and Billie Law (right).
The Hong Kong lab recently encountered another instance of fraud: A natural but HPHT-treated round brilliant diamond (above left) weighing more than 6 carats submitted for verification service was found to be inconsistent with the claimed GIA report issued a few months prior for an untreated diamond. Moreover, the GIA report number and another inscription on the girdle, both supposedly laser-inscribed by GIA (above right), looked convincing but were also found to be fraudulent.

The HPHT-processed round brilliant was believed to have been carefully selected to match the original diamond—its color grade (F) matched, and only minor differences were observed in carat weight and measurements. The HPHT-processed diamond weighed 6.30402 ct and measured 11.73–11.82 × 7.32 mm, whereas the original one weighed slightly less (6.30216 ct), and measured 11.72–11.83 × 7.32 mm. Furthermore, the IF clarity of the HPHT-treated stone was an improvement over the VVS1 clarity of the natural stone.

Despite all the efforts put into those convincing features and measurements, spectroscopic testing easily revealed the stone’s true identity. Infrared absorption spectroscopy showed the HPHT-processed diamond was type IIa, but the original diamond was type Ia. Photoluminescence (PL) spectra were collected at liquid nitrogen temperature with various excitation wavelengths. The slight reversal in the ratio between the 575 and 637 nm peaks (NV centers), together with other spectroscopic features, confirmed the stone had gone through an HPHT treatment process for color improvement. A strain pattern observed under cross-polarized light ruled out the possibility of a synthetic diamond.

This case should raise awareness among the industry and the public that, although rarely encountered in larger stones, this kind of fraud does exist. Verification services at GIA confirm that an item is exactly the same as the one described on a previous report and has not been recut or treated—or, as in this case, replaced with a similar-looking stone. This provides a simple way to check for any type of fraudulent activity if there is doubt about the origin of a diamond. @topic:4


Publish Year: 2020 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. @topic:8