Publish Year: 2015 Title: Visible Absorption Spectra of Colored Diamonds Abstract: ABSTRACT
Diamond color is usually the result of selective absorption of incident white light. The unabsorbed portion of this light is transmitted through the diamond and is interpreted by the human vision system as the perceived color. The spectroscope allows a gemologist to observe some of the more intense and narrower absorptions in the visible spectrum of diamond as dark bands at specific wavelengths. Yet the broader regions of absorption, which can be difficult to observe with the spectroscope, often have a greater influence on a diamond’s color. A chart has been prepared to illustrate the visible spectra of various colored diamonds as recorded at low (liquid-nitrogen) temperatures with a spectrophotometer. The chart shows how similar diamond colors can result from different light absorption patterns. In 2013, the authors published a simple chart listing the major optical defects that can occur at the atomic lattice level in diamond (Shigley and Breeding, 2013). The chart presented some basic information on those defects, including the ones responsible for the colors and ultraviolet fluorescence reactions of most diamonds. The brief article that accompanied the chart discussed the ongoing challenge presented by the identification of natural, treated, and synthetic diamonds. It also discussed how spectroscopy techniques, used to detect absorption and/or emission bands caused by those optical defects, play a leading role in making this important determination. GIA’s laboratory staff, which has the opportunity to examine a large number of colored diamonds, faces this identification challenge on a daily basis.
A theoretically pure and defect-free diamond would be completely colorless, and a unique attribute would be its transparency (or lack of light absorption) across a wide portion of the electromagnetic spectrum from the ultraviolet through the visible and into the infrared regions. There are, however, intrinsic absorption features in the spectra of all actual diamonds. As discussed in our 2013 article, most diamonds also contain lattice defects which, in sufficient concentrations, can produce selective absorption of incident light. (In these instances, the lattice defects are often referred to as optical defects.) When white light strikes a polished diamond, some of the light is reflected, while the rest enters the diamond where it is refracted and dispersed based on wavelength. Some of the light energies (i.e., wavelengths) are absorbed by the defects, while the unabsorbed wavelengths are transmitted. When they exit the diamond, these transmitted wavelengths in combination can create the sensation of color in the human vision system (figure 1). Visible absorption spectroscopy is the analytical tool for understanding most causes of diamond coloration.

Figure 1. In most cases, transparent gemstones owe their color to selective absorption of light. In the case of a yellow diamond, the blue portions of the incident white light are absorbed by the diamond, while the remaining portions in combination are transmitted to the eye and interpreted by our vision system as a yellow color. In the spectroscope, this selective absorption is seen as a darkening toward the blue end of the spectrum (below 425 nm). Recording the spectrum with a spectrophotometer produces a graph of wavelength (horizontal scale) versus absorption (vertical scale). Greater absorption is represented by the higher portions of the spectrum trace, and greater transmission by the lower portions. Below 425 nm, the height of the spectrum trace increases. In the case of this yellow diamond, superimposed on this increasing absorption are several sharp absorption bands or peaks on the spectrum trace between 415 and 478 nm due to the N3 optical center. Gemologists often refer to this set of dark bands as the “Cape” absorption lines characteristic of type Ia yellow diamonds.
At GIA’s laboratory, visible spectra of diamonds are recorded with a spectrophotometer. Since diamond is optically isotropic, the same spectrum can be recorded in any direction through the sample. The faceted stone can be positioned in any orientation as long as the light transmitted through it is sufficient to reach the instrument’s detector. The gem’s shape and facet arrangement can make this a challenge, though. The best positions are those where the light travels directly from the table facet to the culet, or across the diamond through the opposing girdle facets. The diamond is held in a cryogenic unit and cooled to low temperatures with liquid nitrogen. Removing heat from the sample produces a less noisy spectrum. Under these conditions, absorption features that result from certain optical defects are stronger and sharper. Data collection conditions are selected to produce a spectrum that extends from about 350 to 800 nanometers (nm).

Because of a polished diamond’s high refractive index, light can be internally refracted a number of times within it, so the total distance traveled cannot be directly measured or calculated. This uncertainty makes it difficult to relate the strength of the light absorption (as recorded by the spectrophotometer) to the path length of light traveled within the gemstone. Yet this relationship can be estimated by comparing absorption peak height to the heights of some intrinsic absorption features. This relationship also provides an indirect way of comparing the visible spectra of diamonds of different sizes and faceting styles. Because of internal reflection and longer path lengths within the polished diamond, the face-up saturation of the color may appear stronger than the intensity of the absorption features (i.e., height of the absorption bands) in the visible spectrum would suggest.

Natural diamonds occur in all colors of the spectrum. A few colors, such as yellow and brown, are very common, but most are very rare. Nitrogen is the most widespread and abundant impurity element in diamond. It can be present in several optical defects, all of which produce absorption toward the blue end of the spectrum. These factors help explain the prevalence of yellow diamonds in nature. While the face-up appearance of colored diamonds is also influenced by their size and the choice of faceting style, visible absorption spectra provide a tool to understand most causes of diamond coloration.

The accompanying chart representative visible spectra and photos of the major color categories of diamond. The spectra are shown over the 400–750 nm wavelength range. Relative absorption is shown on the vertical scale of each graph, with light absorption increasing higher on the scale (and, conversely, light transmission increasing lower on the scale). Thus, the lower portion of each graph represents the transmitted portion of the spectrum that creates the material’s color sensation. The chart summarizes the major categories of colored diamonds; it is not intended as a detailed discussion of diamond coloration. The graphs are grouped in columns and ranked in descending order of frequency. The colored diamonds included in the chart were selected because their spectra (and color) are principally the result of one main lattice defect. As discussed in our 2013 article, the cause of some defects is well understood, while others are not. We occasionally encounter unusual colors in diamonds whose visible spectra do not correspond to any of the categories shown on the chart.

Download a Larger Version of this Visible Absorption Spectra Chart
The information presented on the chart suggests several observations:

In most cases, diamond colors result from different absorption spectrum patterns, with each pattern originating from one or more optical defects. This can be seen for the different yellow diamonds shown in the first column.
Broad and intense spectral absorption features are more important in producing various colors than sharp or weak bands. Conversely, sharp absorption bands (such as the N3 observed at 415 nm, H4 at 496 nm, and H3 at 503 nm) that can be seen using the spectroscope are helpful in gem identification. We used a spectrophotometer to record the visible spectra, as it can better capture broad absorption bands that are difficult or impossible to see with the eye through a spectroscope.
Similar diamond colors can result from different absorption spectra patterns. In other words, since perceived color is a combination of the wavelengths transmitted to the eye, different absorption patterns can produce similar colors. For example, type Ia and type Ib diamonds, which have different visible spectra patterns, can both exhibit a yellow color (although the color is usually more intense for the latter).
Some diamond colors are the result of just one optical defect, while others result from more than one defect. For example, the chart indicates that the GR1 defect can create a blue or a green color. The defect alone produces a blue color, but when there is also absorption toward the blue end of the spectrum due to nitrogen impurities, the resulting color is green.
Some diamond colors are simply the result of selective light absorption, while others stem from a combination of light absorption and light emission (or luminescence). For example, certain greenish yellow diamonds are yellow due to absorption, while the green component is due to luminescence.
Variations in the types of optical defects, and in their relative concentrations, produce slight color variations among similar diamonds.
Where a diamond photo is shown without an accompanying visible spectrum, the color is due to physical causes other than light absorption—most often the presence of mineral inclusions (e.g., numerous graphite inclusions causing black color in natural diamonds).

This chart is intended as a simple reference for those interested in understanding diamond coloration. While the visible spectra of diamonds are often presented in the gemological literature, compilations of spectra are rarely encountered. @topic:4


Publish Year: 2013 Title: Diamond with Unusual Laser Manufacturing Remnant Abstract: It is common to see laser manufacturing remnants on diamonds, especially stones in blocked form where the cut is not finished. Cutters may use lasers to show where to cut, which features to remove, or the desired shape. The remnants usually appear as straight or sinusoidal lines along the areas to be cut or removed.
A 3.59 ct Fancy Light brownish greenish yellow diamond recently submitted to the Carlsbad laboratory for examination displayed an unusual laser feature.

Figure 1. The 0.9 mm diameter laser manufacturing remnant on this diamond showed an interesting pattern. Photo by Troy Ardon.
The table of the blocked heart shape showed a laser remnant with an interesting pattern that resembled a watch face (figure 1). Unlike the typically linear remnants, this feature was circular and located directly on the table. The cutter’s intentions for placing the 0.9 mm diameter circle on the table are unclear, but it makes for a striking pattern rarely seen on diamonds, especially finished stones. @topic:4


Publish Year: 2013 Title: A Large Irradiated Green-Yellow Diamond Abstract: Figure 1. This 24.16 ct oval-cut diamond (20.47 × 14.00 × 10.72 mm) was color graded as Fancy Intense green-yellow, and identified as artificially irradiated and annealed. Photo by Jian Xin (Jae) Liao.

		Artificially irradiated diamonds are common in the trade, and identifying them remains a challenge. The New York lab recently identified a large diamond as artificially irradiated based on careful spectroscopic analysis and a review of the lab’s database.

	This 24.16 ct oval-cut diamond (20.47 × 14.00 × 10.72 mm) was color graded as Fancy Intense green-yellow (figure 1). The color was distributed evenly throughout the stone, with no color zoning detected. It showed strong yellow and blue fluorescence to long-wave UV radiation, and moderate yellow fluorescence to short-wave UV radiation. This fluorescence reaction and absence of chalkiness are seen in some natural diamonds with a similar bodycolor. Absorption spectrum in the mid-infrared region showed saturated absorptions in the one-phonon region, indicating a type Ia diamond with a high concentration of nitrogen. Also recorded were a moderate platelet peak at 1368 cm–1 (approximately 2.1 cm–1 intensity) and a weak absorption at 1433 cm–1. No hydrogen-related absorption or H1b/H1c center in the near-infrared region was recorded. Absorption spectrum of this diamond in the ultraviolet/visible/near-infrared (UV-Vis-NIR) region at liquid-nitrogen temperature (figure 2) showed a moderately strong absorption from the N3 (415.2 nm) and H4 (496.0 nm) centers, as well as weak absorptions at 512.8, 594.4, and 741.2 nm (GR1).

		Figure 2. After irradiation and annealing treatment, a significant amount of optical center H4 was introduced. This is mainly responsible for the color improvement from Fancy brownish greenish yellow to Fancy Intense green-yellow. N3 absorptions in two spectra in this plot were normalized to the same intensity.

		Absence of the H3 optical center was confirmed by photoluminescence spectroscopy at liquid-nitrogen temperature with 488 nm laser excitation. A fluorescence image collected using the DiamondView showed a gradual change from a predominantly blue table region to a mostly green upper pavilion and girdle area. The spectral features observed in this large diamond are rarely encountered in natural diamonds, raising the possibility of artificial irradiation treatment.

		A search of the GIA database found a very good match between this stone and a previously tested diamond. The two diamonds were identical in measurements and weight, as well as their infrared absorption spectroscopic features, though the previous grade was Fancy brownish greenish yellow. This significant improvement in color appearance is attributed to the relatively high concentration of the H4 center produced by the artificial irradiation/annealing treatment confirmed in this study.

		Despite its suspicious spectroscopic features, this irradiated diamond showed some gemological features normally observed in diamonds with similar natural color. This example demonstrates the value of careful spectral and gemological analysis, combined with a review of the GIA database, in gem identification. @topic:4


Publish Year: 2014 Title: Heavily Irradiated CVD Synthetic Diamond Abstract: Figure 1. The visible-NIR spectrum of the 0.46 ct irradiated synthetic diamond showed a clear Si-doublet at 737 nm.

A Fancy Deep gray-blue diamond weighing 0.46 ct was submitted to the Carlsbad lab for an identification and origin report. Its UV-Vis-NIR spectrum showed a large GR1 center, indicating artificial irradiation. Furthermore, a small 737 nm silicon doublet was seen and later confirmed with photoluminescence (PL) spectroscopy (figure 1). The silicon doublet is a feature in CVD synthetic diamonds, and only very rarely in natural diamonds.

To confirm the synthetic origin of the material, DiamondView images were collected. This required setting the DiamondView at the highest exposure time, because heavily irradiated diamonds tend to show very weak fluorescence, making the image difficult to resolve. The DiamondView image showed a pattern of growth dislocations, which is characteristic of CVD synthetics (figure 2). The infrared spectrum showed some unknown features in the nitrogen region at 1250 and 1116 cm−1. The infrared spectrum lacked the 3123 cm–1 hydrogen-related defect diagnostic of CVD growth (P.M. Martineau et al., “Identification of synthetic diamond grown using chemical vapor deposition [CVD],” Spring 2004 G&G, pp. 2–25), or the 3107 cm–1 peak sometimes created in synthetic diamonds containing hydrogen by HPHT treatment (I. Kiflawi et al., “The creation of the 3107 cm−1 hydrogen absorption peak in synthetic diamond single crystals,” Diamond and Related Materials, Vol. 5, 1996, pp. 1516–1518).

Figure 2. With DiamondView imaging, the growth dislocations in the irradiated CVD synthetic diamond can be clearly seen as the blue sections among the green fluorescence. Image by Wuyi Wang.
CVD synthetic diamonds are known to be treated post-growth to improve color, but this has been seen as HPHT treatment or a combination of irradiation and annealing. HPHT treatment of a CVD synthetic diamond can partially or completely remove a brownish color created during the growth process. If a CVD synthetic is grown with nitrogen impurities, irradiation and annealing will create nitrogen-vacancy centers, producing a pink to red color (J. Shigley et al., “Lab-grown colored diamonds from Chatham Created Gems,” Summer 2004 G&G, pp. 128–145).

This is the first CVD synthetic examined at GIA that has been irradiated to a blue color. The fact that the diamond is synthetic automatically means that the irradiation was done in a laboratory; however, the material displayed color zoning near the culet in a manner identical to natural diamonds that have been irradiated artificially. Electron paramagnetic resonance determined a 20 (+/- 5) ppb concentration of isolated nitrogen. If the specimen were to be annealed, the vacancies would combine with the nitrogen to form NV– centers, as mentioned above. It is possible that the diamond was submitted in an intermediate phase before the final treatment, or that the owner believed it to be a natural but treated stone. Indeed, in the absence of PL spectroscopy and DiamondView images, this specimen could easily be mistaken for an irradiated natural diamond.

As CVD synthetics become more prevalent and subject to a wider variety of treatments, it will only reinforce the role of the gemological laboratory as the most reliable way to separate synthetic from natural diamonds. @topic:4


Publish Year: 2014 Title: CVD Synthetic Diamond with Unusual Inclusions Abstract: A 0.34 ct square modified brilliant was submitted to GIA’s Carlsbad lab as a synthetic diamond. The specimen, which exhibited good polish and symmetry, received a color grade of K and a clarity grade of SI2. During advanced testing, the photoluminescence spectra displayed a large 737 nm doublet, a silicon vacancy peak seen in CVD synthetic diamonds. A DiamondView image showed subtle growth dislocations on the pavilion and almost no growth layer structure on the crown (figure 1). A mid-IR spectrum did not show the 3123 cm–1 peak, once considered characteristic of CVD synthetics (P.M. Martineau et al., “Identification of synthetic diamond grown using chemical vapor deposition [CVD],” Spring 2004 G&G, pp. 2–25).

Figure 1. This DiamondView image of the 0.34 ct CVD synthetic shows a pattern of growth dislocations. Image by Troy Ardon.
The most unusual features were the inclusions. As seen in figure 2, this item is deserving of its SI2 clarity grade. In addition to several fractures, there were numerous indented crystal surfaces and included growth remnants. A close-up of the indented crystal surfaces revealed an irregular shape and surface texture (figure 3). The fully included growth remnants lacked any discernible pattern or regularity. Inclusions have been reported in CVD synthetic diamonds, but they have been confined to growth planes (Spring 2013 Lab Notes, pp. 47–49). This specimen’s inclusions, which were scattered in a random way, showed no uniformity in size, shape, color, or placement. They were whitish or black, pinpoint-sized and larger structures (as seen in figure 3, lower right). Some were flat and pointed, while others were more rounded in shape. Furthermore, some were grouped together, similar to cloud-like inclusions, while others were freestanding, mimicking the inclusion distribution in natural diamond. The strain was mottled around the inclusions and crosshatched in cleaner areas.

Figure 2. The pavilion displayed a wide variety of inclusions. Photomicrograph by Troy Ardon; field of view 3.6 mm.

Figure 3. A close-up of some of the indented crystal structures showed etch-like patterns. Photomicrograph by Troy Ardon; field of view approximately 1.4 mm.
The chemical structure and composition of these inclusions is unknown, and why they formed this way is a mystery. It is possible that this material is from a new growth method that yields heavily included product. Synthetic diamond research is a rapidly growing field; as it expands, many new and different types of samples find their way into the trade. The inclusions in this specimen could pass for natural inclusions if observed with a standard 10× loupe or a quick glance in the microscope. The DiamondView image is also difficult to interpret if one is not accustomed to the many fluorescent patterns CVD synthetic diamonds can display. This case is an important reminder to exercise caution when determining natural or synthetic origin, because some synthetic diamonds in the market look very natural. @topic:4


Publish Year: 2014 Title: Chameleon Diamond with Nickel Absorption Band Abstract: Figure 1. The chameleon diamond is shown before and after heating (left and right). Photos by Robison McMurtry.

              The Carlsbad laboratory recently examined a 0.31 ct Light greenish yellow marquise-cut diamond. The stone displayed the strong yellow fluorescence, persistent yellow phosphorescence, and green color component of a chameleon diamond. A chameleon diamond has a green or greenish color component under normal conditions. When heated or left in the dark for long periods of time, the green component temporarily disappears, giving way to an orange component. Figure 1 shows the diamond before and immediately after heating, in which the removal of the green component leads to an orange-dominant hue, demonstrating that the stone was in fact a chameleon diamond. Unfortunately, the stone’s low saturation makes the effect less noticeable.

Examination of the visible-NIR spectrum revealed a noticeable nickel-related absorption band at 685 nm (figure 2). DiamondView images were taken to prove the stone was not synthetic, as nickel is a common catalyst in HPHT synthetics (figure 3). While nickel has long been known to occur as a trace element in chameleon diamonds (T. Hainschwang et al., “A gemological study of a collection of chameleon diamonds,” Spring 2005 G&G, pp. 20–34), its role in the color-change effect is unknown. Nickel has also been reported as a cause of green coloration in certain diamonds (W. Wang et al., “Natural type Ia diamond with green-yellow color due to Ni-related defects,” Fall 2007 G&G, pp. 240–243), but this may be the first time it has been identified as the major cause of a green component in a chameleon. The rarity of chameleon diamond, combined with the rarity of Ni-related natural green diamonds, makes this a truly unique specimen.

	Figure 2. The absorption spectrum of the chameleon diamond shows a nickel-related band at 685 nm.

	Figure 3. DiamondView imaging showed uneven blue and green fluorescent zones, proving the stone’s natural origin. @topic:4


Publish Year: 2014 Title: Very Large Irradiated Yellow Diamond Abstract: Figure 1. This 22.27 ct Fancy Vivid yellow diamond was identified as artificially irradiated and annealed. Treated diamonds of this size and attractively saturated color are rare. Photo by Sood Oil (Judy) Chia.

              Artificial irradiation, with or without annealing, has been used to improve the color of natural diamonds for several decades. This technique is usually applied to brownish or light yellow diamonds of relatively small size. The New York lab recently tested a very large yellow diamond that had been artificially irradiated.

This emerald-cut stone weighed 22.27 ct and was color graded as Fancy Vivid yellow (figure 1). Faint color concentration was observed along the culet. The diamond showed medium yellow-green, slightly chalky fluorescence to long-wave UV and weak orange fluorescence to short-wave UV. No obvious internal features were observed. Its infrared absorption spectrum showed high concentrations of nitrogen and weak absorptions from defects H1b (4935 cm–1) and H1c (5165 cm–1). A weak hydrogen-related absorption at 3107 cm–1 was also detected. In the Vis-NIR region, the absorption spectrum collected at liquid-nitrogen temperature showed strong absorptions from the N3, H4, H3, and 595 nm optical centers (figure 2). These spectroscopic and gemological features demonstrated that the diamond had been artificially irradiated and annealed to introduce additional absorptions from the H3/H4 defects, enhancing its yellow color. This Fancy Vivid yellow color would have been much lighter and less saturated before the treatment.

Figure 2. The irradiated yellow diamond’s Vis-NIR absorption spectrum, collected at liquid-nitrogen temperature, showed strong absorption from the H3 and H4 defects, which were artificially introduced to enhance the yellow color.
Artificially irradiated diamonds of this size and attractive color are rarely examined in gem laboratories. @topic:4


Publish Year: 2015 Title: Unusual Graining Structure in Pink Diamond Abstract: Left: A colorless hole within a natural pink diamond, observed with darkfield illumination. Field of view approximately 2 mm. Right: The colorless hole in polarized light, showing the cone of strain. Field of view approximately 2 mm. Photos by Nathan Renfro.

	Natural pink diamonds examined for origin of color determination often display visible pink coloring along planes of stress. This graining is visible at a slight angle to the plane and can occur as a single plane or multiple parallel planes. The color may be either uniform or unevenly distributed along the graining. One pink stone recently examined in the Carlsbad lab was noted to have a uniform plane of pink color with a colorless hole, seen in the image on the left. The diamond was graded Very Light pink, so the colored plane had low saturation, but the irregularity was impossible to miss in the microscope. When examined under polarized light, a cone of strain could be seen intersecting the plane and fitting perfectly in the colorless hole, as seen in the image on the right.

	Pink graining is the result of an unknown defect with an unknown formation mechanism (J.G. Chapman and C.J. Noble, “Studies of the pink and blue coloration in Argyle diamonds,” Summer 1999 G&G, pp. 156–157). It seems to be related to the plastic deformation of diamond, evidenced by the color lying along planes of stress. Whether pink graining occurs during diamond growth or is formed after by stresses or heat from the earth (or a combination of the two) is also poorly understood. It is therefore a mystery as to whether the cone of strain formed first or concurrently and prevented the formation of pink graining at the circle of intersection, or if the cone formed afterward and destroyed the color centers associated with pink graining. Until diamond formation is more fully understood, this dynamic interplay of strain will remain a mystery. @topic:4


Publish Year: 2015 Title: Artificially Irradiated Color-Change Diamonds Abstract: Figure 1. These two chameleon diamonds (0.35 and 0.27 ct) were color-treated with
artificial irradiation. Photo by Jian Xin (Jae) Liao.

Diamonds that exhibit a temporary color change, commonly referred to as “chameleon” diamonds, are rare in nature. Their color changes with gentle heating, or when they are left in darkness for a period of time. The change from a dark greenish to a lighter yellow hue upon gentle heating is due to the thermochromic properties of these diamonds (D.J. Content, Ed., A Green Diamond: A Study of Chameleonism, W.S. Maney & Son, Leeds, England, 1995, 42 pp.).

Recently the New York laboratory examined two chameleon diamonds, a 0.35 ct Fancy Deep yellow-green marquise and a 0.27 ct Fancy Deep grayish yellowish green marquise (figure 1). Spectroscopic analysis and gemological observations confirmed that these were typical chameleon diamonds. After excitation with short-wave UV light, both exhibited a strong blue to yellow phosphorescence often seen in natural chameleon diamonds. Their UV-Vis absorption spectra showed a broad band at about 480 nm, as expected for this type of diamond. But the spectra also displayed a peak at 741 nm (figure 2), known as GR1 (general radiation damage), that can contribute to a green color in diamonds. Because this radiation-related feature is not found in untreated natural chameleon diamonds, we concluded that both stones had been artificially irradiated.

Figure 2. The UV-Vis spectra for the two chameleon diamonds show a broad absorption peak around 480 nm and an atypical GR1 feature at 741 nm.
A chameleon diamond is an unlikely candidate for artificial irradiation treatment to enhance the stone’s green or blue bodycolor. It is likely that this property was not known or understood before the irradiation process. A permanent color change may occur if these treated chameleon stones are heated for a prolonged period, so it is important to exercise caution during testing. Because the diamonds’ original colors are unknown, they were issued reports stating that they had been artificially irradiated to enhance their color. @topic:4


Publish Year: 2016 Title: Largest Blue HPHT Synthetic Diamond Abstract: Figure 1. A 5.03 ct Fancy Deep blue HPHT synthetic diamond was examined by GIA (left). Faint but sharp color zoning was observed (middle, field of view 4.77 mm) along with small metallic inclusions and a cavity at the girdle (right, field of view 2.19 mm). Photos by Sood Oil (Judy) Chia (left) and Kyaw Soe Moe (center and right).
Recently, large colorless and near-colorless HPHT-grown diamonds by the Russian company NDT have been investigated, with sizes up to 5.11 ct (U. D’Haenens-Johansson et al., 2015, “Large colorless HPHT-grown synthetic gem diamonds from New Diamond Technology, Russia,” Fall 2015 G&G, pp. 260–279; Spring 2015 G&G Lab Notes, pp. 65–66). The largest faceted colorless HPHT-grown synthetic diamond reported to date is a 10.02 ct E-color, VS1-clarity specimen, reported by IGI Hong Kong in 2015. In January 2016, GIA’s New York laboratory examined a 5.03 ct fancy-color HPHT-grown type IIb synthetic diamond (figure 1, left) produced by NDT, the largest faceted blue laboratory-grown diamond studied so far.
This emerald-cut synthetic diamond was color graded as Fancy Deep blue. This is a very attractive color with no other color component, a prized rarity among natural type IIb diamonds (the Blue Moon, for instance, was graded as Fancy Vivid blue). When viewed under a microscope, faint but sharp color zoning could be seen (figure 1, center), indicative of the uneven impurity incorporation of HPHT synthetic diamonds. No strain was observed under crossed polarizers, indicating a very low dislocation density, which is also characteristic of HPHT-grown diamonds. It had VS1 clarity, with only very small metallic inclusions and a cavity observed at the girdle (figure 1, right). Fluorescence and phosphorescence images collected using a DiamondView instrument revealed the sample’s cuboctahedral growth pattern (figure 2, left), another feature of HPHT synthetics. The long-lasting chalky blue phosphorescence was further analyzed using spectroscopy, and the emission was found to originate from two broad bands centered at approximately 500 and 575 nm (figure 2, right). These bands have previously been reported in NDT’s type IIa and IIb HPHT synthetic diamonds (D’Haenens-Johansson et al., 2015).

Figure 2. DiamondView images of fluorescence (top left), and phosphorescence (bottom
left) revealed a cuboctahedral growth pattern, which is typical for HPHT-grown synthetic
diamond. Phosphorescence spectra (right) show two peaks at approximately 500 and
575 nm, contributing a chalky blue color.
Absorption spectroscopy for the mid-infrared region confirmed the sample was type IIb, with strong boron-related features at 1290, 2458, and 2800 cm–1. The average bulk boron concentration was 0.82 to 1.12 ppm, calculated according to the equation NA-ND = (1.00 ± 0.15) × H1290 ppm cm–3 , where NA is acceptor concentration, ND is donor concentration, and H1290 is peak height at 1290 cm–1 (A.T. Collins, “Determination of the boron concentration in diamond using optical spectroscopy,” Proceedings of the 61st Diamond Conference, Warwick, UK, 2010). Otherwise, this large synthetic diamond exhibited an extremely low concentration of optical defects. Photoluminescence spectroscopy was conducted at liquid nitrogen temperatures using a range of laser excitations covering the UV-visible-IR range. The PL spectra only revealed emission from a single defect species, a Ni-related emission multiplet with peaks at 483.6/483.8/484.1/484.4 nm (484 nm center) detected using 324.8 nm laser excitation (A.T. Collins, “The characterisation of point defects in diamond by luminescence spectroscopy,” Diamond and Related Materials, Vol. 1, 1992, pp. 457–469). As with previous type IIb synthetic diamonds, its visible-NIR spectrum showed a transmission window in the blue region and an absorption in the red, caused by the presence of boron, resulting in the observed blue bodycolor.

This 5.03 ct sample is the largest HPHT-grown blue synthetic diamond examined at a GIA laboratory. As the size and quality of synthetic diamonds improve, careful identification is essential. Representative HPHT synthetic diamond characteristics seen in this specimen, such as the lack of tatami strain patterns (which are typically observed in natural type IIb diamonds), faint but sharp color zoning, and small metallic inclusions from the metal-catalyst flux, can be detected using a gemological microscope, emphasizing its continued importance in gem identification. Examination of this large IIb synthetic diamond, combined with those previously reported from NDT, illustrates the rapid progress in HPHT growth technologies. This is a development that will eventually impact the jewelry industry. @topic:4


Publish Year: 2018 Title: Three Irradiated CVD Synthetic Diamonds Abstract: Figure 1. These 1.12 ct, 1.14 ct, and 1.34 ct laboratory-irradiated CVD synthetic diamonds all have similar appearance, with color grades equivalent to Fancy Deep green-blue. Photos by Robison McMurtry.
While laboratory-irradiated diamonds are often submitted for grading reports, irradiated synthetics with a green-to-blue color are still a rare occurrence. Before the submissions described here, GIA’s laboratory had examined only three irradiated CVD synthetics (Fall 2014 Lab Notes, pp. 240–241; Fall 2015 Lab Notes, pp. 320–321) and two irradiated HPHT synthetics. So it was interesting when the Carlsbad laboratory received three irradiated CVD synthetics, apparently from the same client.
All three synthetics showed very similar features in terms of color (equivalent to Fancy Deep green-blue; figure 1), clarity (equivalent to VVS2), and weight (1.12 ct, 1.14 ct, and 1.34 ct), along with comparable features detected by fluorescence imaging (figure 2) and spectroscopy (figure 3).

Figure 2. All three irradiated CVD synthetics displayed very weak fluorescence in the DiamondView, as seen in the 1.14 ct sample shown here. All showed the characteristic striations of CVD growth. Image by Sally Eaton-Magaña.

Figure 3. Radiation-related features dominate the CVD synthetic diamonds’ Vis-NIR absorption spectra when collected at liquid nitrogen temperature. Features include the GR1 at 741.2 nm, the 595 nm center at 594.2 nm, the TR12 center at 469.9 nm, a radiation-related peak at 464.3 nm, and the GR2 at 429 nm.
The Vis-NIR and IR absorption spectroscopy and the photoluminescence (PL) spectroscopy were nearly identical among the three specimens, indicating that they were probably grown and treated under similar if not identical conditions. The IR absorption spectra showed very weak 3107 cm–1 and 1344 cm–1 peaks. Based on the integrated area of the 1344 cm–1 peaks (I. Kiflawi et al., “Infrared absorption by the single nitrogen and A defect centres in diamond,” Philosophical Magazine B, Vol. 69, No. 6, 1994, pp. 1141–1147), we determined the single N concentration as about 0.4–0.5 ppm for all three samples. The Vis-NIR absorption spectra showed typical features for irradiated diamonds: the TR12 (a radiation-related feature tentatively ascribed to a divacancy/di-interstitial defect at 469.9 nm), the 595 nm center, and GR1 [V0] at 741.2 nm (figure 3). PL spectra showed a weak SiV– doublet at 736.6 and 736.9 nm along with a very strong GR1 center. PL spectroscopy also indicated the presence of the H2 peak at 986.2 nm and the lack of the 596/597 nm doublet that is normally seen in as-grown CVD synthetics and generally disappears with post-growth treatment. This combination, along with the 3107 cm–1 peak in the IR spectra, suggests these diamonds were HPHT treated before irradiation.
Owing to their extreme rarity and individuality, creating a set of matching natural-color diamonds can be quite challenging. In contrast, synthetic diamonds can demonstrate uniformity in features and appearance due to the manufacturer’s ability to control the growth conditions, defect concentrations, and the subsequent treatment parameters. @topic:4


Publish Year: 2019 Title: CVD Layer Grown on Natural Diamond Abstract: Figure 1. Face-up image of the natural diamond with CVD synthetic diamond overgrowth. The blue color is due to the boron-doped CVD layer. Photo by Robison McMurtry.

A 0.64 ct Fancy grayish greenish blue cushion modified brilliant (figure 1) was recently found to be a composite of synthetically grown and natural diamond. During testing, the infrared spectrum showed both strong absorption of nitrogen and the absorption of uncompensated boron, features characteristic of type Ia and type IIb diamonds, respectively (figure 2). The UV-Vis-NIR spectrum showed “cape” peaks, which are nitrogen-related defects, but also a sloping absorption into the red portion of the spectrum caused by uncompensated boron. It is very unusual for boron- and nitrogen-related defects to be seen together in natural diamonds, though an example has been seen before (Spring 2009 Lab Notes, pp. 55–57). Mixed-type diamonds always call for additional scrutiny.

Figure 2. The infrared spectrum shows both nitrogen- and boron-related defects. This combination of defects is very unusual in natural diamonds and a cause for concern.
The DiamondView fluorescence image taken on the pavilion showed a blue hue, caused by luminescence from the N3 defect, and natural growth features. The image taken on the crown showed a greenish blue color common to boron-bearing diamonds and the dislocation patterns characteristic of CVD-grown diamonds. In the image taken from the side, a layer can be seen between the natural substrate and the CVD-grown addition (figure 3). These two distinct fluorescence patterns—the greenish blue from the CVD layer and the darker blue from the naturally grown layer—prove that a layer of CVD synthetic diamond was grown on a natural substrate. A wireframe model generated from a non-contact optical measurement device was uploaded to the DiamCalc diamond modeling program. Using the fluorescence images as a guide, we obtained a 3D section that represented only the CVD layer. From this, we calculated an approximate layer weight of 0.10 ct and a thickness of approximately 200 microns. A similar diamond previously reported was also a type IIb CVD layer grown on a natural Ia substrate (Summer 2017 Lab Notes, pp. 237–239). That composite was Fancy blue, weighed 0.33 ct, and had a CVD layer that was 80 microns thick.

Figure 3. A DiamondView image showing the separation plane. Image by Garrett McElhenny.
When viewed through a microscope, small pinpoint-like polish features were observed from facet to facet along with a faint line resembling surface graining. These polish features were visible along the entire area of this division and correlated with the separation plane seen in the fluorescence images. Examination with an electrical conductivity tester showed that the crown was conductive but not the pavilion. This is consistent with a type IIb crown and type Ia pavilion.

Figure 4. In immersion, the blue color of the CVD layer is clearly visible. Photo by Jonathan Muyal.
In immersion, the CVD layer was grayish blue whereas the natural substrate had a yellowish bodycolor (figure 4). The blue color in the CVD layer is from the uncompensated boron, and the yellowish color in the substrate is due to the “cape lines” in the visible spectrum. The final color, Fancy grayish greenish blue, is caused by the gray and blue components from the CVD layer and the yellow from the substrate. The resulting color was likely the main motivation for growing the CVD layer on top of the natural diamond, though the extra weight gained could also be a factor. Viewing under crossed polarizers in immersion revealed dislocation bundles that started at or near the interface and grew upward and outward (figure 5). This proves that it was a thick CVD layer and not a coating of CVD overgrowth.

Figure 5. Dislocation bundles in the CVD layer are visible under crossed polarizers in methylene iodide. Photo by Troy Ardon; field of view 1.90 mm.
In CVD-grown diamonds, there is some indication in PL spectra that the diamond has been grown in a laboratory—usually the presence of the silicon doublet peak at 736.5 and 736.9 nm or the 596/597 nm defect. Numerous PL spectra were collected in standard and confocal mode on both the crown and pavilion of the diamond in search of any indication of this synthetic overgrowth. In this case, neither of these CVD features were evident, likely due to the thinness of the layer.
With the second of these composites seen at GIA, this could be a new type of product entering the market. Earth-grown diamonds with synthetic diamond grown on the surface require extra scrutiny due to the presence of natural-looking features, both spectroscopic and gemological. Careful inspection still reveals the presence of synthetic indicators, which expose the true nature of the diamond. @topic:4


Publish Year: 2019 Title: The Largest Diamond Ever Discovered in North America Abstract: Figure 1. This 552.7 ct yellow diamond (54.5 × 34.9 × 31.8 mm) from the Diavik mine in Canada is by far the largest diamond found to date in North America. Photo by Jian Xin (Jae) Liao.

In October 2018, a diamond weighing a remarkable 552.7 ct was recovered from the Diavik mine in Canada. This is by far the largest known gem diamond found to date in North America. It is nearly three times larger than the 187.63 ct Diavik Foxfire which was unearthed from the same mine in August 2015, and about twice the size of a 271 ct white diamond mined from the Victor mine in Canada. GIA’s New York laboratory had the opportunity to examine this notable diamond in late January 2019, before it went on public display at the Phillips Auctions in New York.
This large diamond (54.5 × 34.9 × 31.8 mm) has a striking yellow bodycolor and a rounded irregular ovoid shape (figure 1). The markedly rounded overall shape is due to strong resorption of the crystal surface, leaving a coarse surface texture of complex terraces and hillocks. Negative trigons were sparsely distributed. A fracture oriented perpendicular to the length divides a portion of the diamond, about a quarter of the way in from the smaller end (the left side in figure 1). In and around the fracture there are a few small black inclusions, possibly graphitic or sulfide. At high magnification, a portion of the fracture is slightly resorbed, suggesting that at least part of the fracture developed during ascent in the kimberlite. Patches of surface abrasion up to 7 mm across, but limited to a very shallow depth, are spread widely over the surface. According to a statement by Dominion, these markings are thought to be the result of abrasion during the recovery process, and the fact that the diamond remains unbroken is remarkable.
Infrared absorption spectroscopy reveals that the diamond is type Ia, with a very high concentration of aggregated nitrogen. A very weak absorption at 3107 cm–1 from the N3VH lattice defect was also recorded. UV-visible absorption spectroscopy reveals strong absorption from N3 (415 nm) and N2 (478 nm), a typical feature of “cape” diamonds. No other absorption features were detected in the UV-Vis spectrum, consistent with the pure yellow bodycolor visible to the eye. Under long-wave UV radiation, this diamond has strong blue fluorescence and weak but long-lasting yellow phosphorescence. Moderate whitish blue fluorescence and very weak orange phosphorescence were observed under short-wave UV radiation. All these gemological and spectroscopic features are very similar to those observed in the Diavik Foxfire. Photoluminescence analysis at liquid nitrogen temperature with varying laser excitations from the UV to the infrared region revealed additional features of a typical “cape” diamond. Main emission peaks included very strong N3 at 415 nm and weak H3 at 503 nm. In addition, weak emissions at 489, 535, 604, 612, 640, 700, 741, 787, and 910 nm were recorded. No emission from H4 (496 nm) or H2 (986 nm) was observed.
This diamond has a combination of size, color, and top gem quality that is extremely rare. It will be exciting to see this special diamond crafted into polished form. The Diavik mine is jointly owned by mining companies Rio Tinto and Dominion Diamond Mines.

	552.7 ct Diamond from the Diavik Mine @topic:10


Publish Year: 2019 Title: Faint Green HPHT Synthetic Diamonds Abstract: Figure 1. This 0.50 ct HPHT synthetic diamond, color equivalent to Faint Green, owed its color to nickel impurities. Photo by Robison McMurtry.

The Carlsbad lab recently received 25 diamonds for grading reports that all proved to be undisclosed HPHT synthetics, ranging in weight from 0.46 to 0.52 ct. Of these, nine were equivalent to the colorless to near-colorless range, eight equivalent to Faint yellow-green, seven equivalent to Faint green (e.g., figure 1), and one equivalent to Very Light green. We found that the green coloration was due to high concentrations of nickel. Nickel is a common impurity in HPHT synthetics, but rarely in amounts significant enough to affect the color.
Previously, GIA gemologists described an HPHT synthetic diamond whose color was equivalent to Fancy Deep yellowish green due to massive amounts of nickel creating an absorption band at ~685 nm (Spring 2017 Lab Notes, pp. 96–98). They showed that the optically active nickel impurities were preferentially incorporated into the {111} growth sectors, as detected by the photoluminescence (PL) spectral maps and observable color zoning.
Among this set of 25 HPHT synthetic diamonds, none showed the SiV– defect at 737 nm with 633 nm PL excitation while 16 showed detectible amounts of uncompensated boron at 2800 cm–1 in their infrared absorption spectra. In this suite, five showed the 685 nm absorption band generally associated with strong nickel impurities while the others showed a broader, less pronounced absorption band ranging from 650 to 800 nm. The quantity of uncompensated boron was relatively low, with most containing 0.2–5.6 ppb and one near-colorless sample containing 18 ppb. Uncompensated boron is also a common impurity in HPHT synthetics, as it is incorporated during the growth process; these low concentrations did not contribute to the coloration. Additionally, several showed distinctive metal flux inclusions, also indicative of HPHT growth (e.g., figure 2).

Figure 2. This 0.52 ct Faint yellow-green HPHT synthetic diamond also showed pronounced metal flux inclusions, further proof of its lab-grown origin. This view shows the pavilion facets, with the girdle at the top of the photo. Photomicrograph by Jonathan Muyal; field of view 1.76 mm.

Figure 3. Left: This PL map, collected with 785 nm excitation, shows that the highest amounts of nickel are concentrated within {111} growth sectors of this 0.52 ct Faint yellow-green HPHT synthetic diamond. This false-color map shows the area of the 883/884 nm doublet normalized with the diamond Raman peak. Right: The average PL intensity of the nickel-related 883/884 nm peak within the {111} sectors increases as the equivalent color increases from colorless to Very Light green.
Having such a large dataset of similar but unusually colored HPHT synthetic diamonds in the laboratory simultaneously also allowed us to perform additional analyses to compare them. Photoluminescence maps using 785 nm excitation were collected on the table facet of eight samples, spanning across the various graded colors (figure 3). As expected, the nickel peaks showed the highest concentration within the {111} sectors. From each of the collected maps, we could identify the {111} sectors and determine the average PL intensity of the nickel-related 883/884 nm peaks. When these were plotted according to their equivalent color, the peak intensity was seen to generally increase as the color grade went from the colorless to near-colorless range to Very Light green. Nevertheless, the nickel-related defect at 883/884 nm is not believed to be the same nickel-related defect creating visible absorption. A similar PL map, not shown, was collected on the Fancy Deep–equivalent yellow-green HPHT synthetic diamond (again, see Spring 2017 Lab Notes, pp. 96–98); the nickel intensity in that case was approximately 10× greater than the Faint green samples studied here.
As laboratory-grown diamond manufacturers continue to experiment with their recipes and the process further evolves, we will likely see greater quantities and a wider variety of color ranges. @topic:4


Publish Year: - Title: Inside De Beers’ Lightbox Diamonds Abstract: GIA research scientist Dr. Sally Eaton-Magana analyzes the image of a marquise diamond in the DiamondView to determine whether or not the stone is synthetic. Photo by Russell Shor/GIA

De Beers’ line of laboratory-grown diamonds, Lightbox, made its retail debut in the fall. Shortly afterward, GIA researcher, Dr. Sally Eaton-Magana, who has been identifying and analyzing lab-grown diamonds for 11 years, took a close look at the new De Beers-produced product for the Winter 2018 issue of Gems & Gemology.

Lightbox diamonds are produced in quarter carat, half carat and full carat sizes in colorless, pink and blue, and are uniformly priced at $800 per carat. Eaton-Magana examined two colorless specimens of .24 ct and .26 ct, respectively.

Both stones had color equivalent to G on the GIA diamond color scale, with cut grades of excellent and very good. Both were very high clarity, the equivalent of VVS2 on the GIA clarity scale. The smaller diamond had a pinpoint in a bezel facet, while the other had a tiny feather in a star facet. The laser-inscribed Lightbox logo (2 equilateral triangles base to base with an isosceles triangle in the middle) under the table – large enough to be easily visible with a microscope – would reduce the equivalent clarity grade to VS2. GIA Synthetic Diamond Grading Reports use ranges, rather than specific grades, to describe the color and clarity of laboratory-grown diamonds.

Magana confirmed that the Lightbox diamonds were grown using the chemical vapor deposition (CVD) process, which means they are Type IIa with no detectable nitrogen. “The identification criteria for high pressure, high temperature (HPHT) and CVD synthetics can be quite distinct from each other,” she explained, adding that synthetic products have become much more varied over the last 10-15 years.

“When the GIA synthetic diamond grading report was first launched in 2007, CVD synthetics were not commercially available,” she noted. “The commercially available sizes of lab-grown diamonds have expanded such that both very large and very small stones are possible. Also, colorless to near-colorless synthetics were once quite rare and are now the majority seen at the lab.”

Although Lightbox is new to the market, and the variety of lab grown diamonds is increasing, the fundamental identification criteria have not changed. They are based on growth morphology and optical properties. “We also regularly conduct research on emerging products and GIA has a program to grow synthetics ourselves to stay ahead of any new trends,” she said.

Similarly, the basic equipment for identification has not changed. Researchers and grading laboratory staff continue to rely on microscopy, fluorescence imaging, absorption spectroscopy, and photoluminescence (PL) spectroscopy. What has evolved, she said, is the speed and efficiency of these devices.

The evolution of PL mapping capabilities is important, she explained, because it enables GIA to collect thousands of spectra at micron-sized intervals across the surface of a diamond in mere minutes.

“This technology allows us to map the defect concentrations of synthetic diamond to visualize the growth sectors in HPHT synthetics,” Eaton-Magana explained. “The recent ability to collect many thousands of PL spectra instead of just one spectrum on a diamond gives us opportunities to draw correlations that would not have been previously possible. We have also expanded our research into largely previously unexplored variables – such as what are the effects on spectra within the diamond at various temperatures and timescales; for example, exploring diamond’s luminescence at the nanosecond to millisecond time ranges.”

She said that PL spectra showed the Lightbox diamonds were not subjected to post-growth HPHT processing to improve their color. The researchers noted that about 75% of all CVD-grown diamonds they encounter have been subjected to such treatment. This is because quite often these diamonds are grown with a brownish color, especially if the manufacturers attempt to grow them quickly. While the HPHT treatment process is effective in improving the color of CVD diamonds, the large amount of energy used to create sufficient heat and pressure can add significantly to the cost of production. The Lightbox products, however, are priced much lower than most other lab-grown diamonds in the market.

Both diamonds showed visible red fluorescence in imaging by the DiamondView synthetic detector, but had no detectable fluorescence under long wave UV light. The lab-grown diamonds did show tell-tale CVD growth striations, but they were difficult to spot, requiring careful DiamondView imaging.

Lightbox lab-grown diamonds are readily identifiable as CVD by spectroscopic techniques, DiamondView imaging and, of course, the inscribed logo under the table, her article noted.

Magana earned her doctoral degree in chemical engineering with Dr. John Angus, one of the early pioneers of CVD synthetic diamond growth. For her Ph.D. and post-doctoral work, she worked mainly on growing CVD synthetics for engineering and semiconductor applications.

“While at my post-doc assignment, we collaborated with the Smithsonian Institution to study the phosphorescence of type IIb diamonds in their collection, including the Hope Diamond. With this introduction to gem diamonds, I wanted to transition into this field and was fortunate to obtain a position at GIA following my post-doctoral assignment,” Magana said. “Since then, I have spent much of my time delving into the physics of gem diamonds, concentrating on various treatments, detection methods, and distinguishing synthetics from their natural counterparts.” @topic:4


Publish Year: 2018 Title: Natural Diamond Mistaken as HPHT Synthetic Abstract: Figure 1. This D-color 2.23 ct natural diamond was originally submitted as a synthetic. Photo by Robison McMurtry.

When a declared synthetic diamond is submitted to a GIA laboratory, it is not often that the diamond turns out to be natural. But this was the case recently when a D-color 2.23 ct round brilliant was submitted to the Carlsbad laboratory for a synthetic diamond grading report (figure 1). Its infrared absorption spectrum established it as type IaA>B, with nitrogen aggregates around 80 ppm, confirming a natural color origin. Since it was stated as synthetic, further analysis was performed.
There are very few gemological indicators of lab-grown diamonds (S. Eaton-Magaña and C.M. Breeding, “Features of synthetic diamonds,” Summer 2018 G&G, pp. 202–204). Yet one of the most reliable and easily seen observations is the lack of birefringence (or strain) patterns in HPHT synthetics when viewed between crossed polarizers. To our knowledge, visible strain in HPHT-grown synthetic diamonds has only been documented in one rare case (Winter 2016 Lab Notes, pp. 417–418).

Figure 2. An apparent lack of strain was observed throughout most of the stone, with strain visible only around inclusions (left). Such observations are common in HPHT synthetics and not generally seen in natural or CVD synthetic diamonds. With extensive searching and careful positioning, linear strain was visible within small areas of the stone (right). Photomicrographs by Garrett McElhenny; fields of view 7.19 mm.
Although strain observations are rarely used by many in the trade, this natural diamond was perhaps presumed to be synthetic due to its apparent lack of observable strain. When viewed under crossed polarizers, the strain was very difficult to discern (figure 2, left), and this apparent absence was consistent with our observations of HPHT synthetics. With extensive searching and careful positioning, the strain was visible in a few scattered areas of the diamond. The observed strain was linear in appearance, consistent with type Ia natural diamonds (figure 2, right).

Figure 3. Microscopic examination shows discernible dark mineral inclusions that occur naturally in diamonds and could have been mistaken for metallic flux inclusions. Photomicrograph by Garrett McElhenny; field of view 3.57 mm.
With further investigation using a variety of techniques such as photoluminescence spectroscopy and DiamondView imaging, all tests confirmed a natural origin. Additionally, microscopic observation revealed unidentified dark natural crystal inclusions (figure 3), which might have been mistaken for metallic flux.
Subsequently the client indicated that this stone was believed to be synthetic after examination by another party in the trade. However, several gemological and spectroscopic tests confirmed its natural origin.
This diamond demonstrates why stones of uncertain origin should be submitted to a gemological laboratory for further testing. It also provides confirmation that occasional exceptions exist for the general guidelines that help distinguish natural from lab-grown diamonds. In this case, the correction worked to the client’s advantage. @topic:4


Publish Year: 2016 Title: Ring with a CVD Synthetic Melee Diamond Abstract: Figure 1. One of the round-cut melee mounted in this ring was identified as a CVD synthetic diamond. Photo by Johnny Leung.

The separation of synthetic diamond melee from natural diamond melee is a significant concern. Some specimens have been identified by GIA and other laboratories as synthetic, but those products were predominantly HPHT grown. GIA’s Hong Kong lab recently identified a CVD synthetic melee mounted in a ring (figure 1).

The round-cut synthetic measured approximately 2.8 mm in diameter and weighed about 0.08 ct. Color could not be graded due to the mounting, but it was estimated to be in the F-H range. The material showed no notable visual features using the microscope other than a small surface scratch at the table. Infrared absorption spectroscopy indicated the typical features of a type IIa diamond; no defect-related absorption feature was detected. A PL spectrum was collected at liquid nitrogen temperature with a very wide range of laser excitation wavelengths. Major features included emissions from [N-V] and [Si-V]– centers (figure 2). The emission at 575.0 nm from [N-V]0 is much stronger than the peak at 637.1 nm from [N-V]–, similar to many natural type IIa diamonds. Most notably, this specimen showed very strong emissions at 736.6 and 736.9 nm from the [Si-V]– defect. Using 514 nm laser excitation, the intensity of the [Si-V]– defect was about eight times that of the diamond Raman line. DiamondView imaging revealed strong orange color with small irregular areas of blue fluorescence (figure 3). All these observations confirmed that this melee is an as-grown CVD synthetic.

Figure 2. The photoluminescence spectrum collected at liquid nitrogen temperature with
514 nm laser excitation shows moderate emissions from [N-V] centers and a very strong
emission from [Si-V]–.

Figure 3. DiamondView imaging showed strong orange fluorescence with small irregular areas of blue fluorescence, a typical feature of as-grown CVD synthetic diamond. Photo by Carmen Lo.
This was the first mounted CVD synthetic melee diamond identified by GIA. While synthetics of this size are overwhelmingly HPHT grown, we do expect to see more CVD synthetic diamond melee in the future. @topic:4


Publish Year: 2015 Title: Yellow HPHT-Processed Rough Diamond Abstract: Figure 1. This 2.47 ct rough diamond was HPHT processed to improve its color. Unlike conventional HPHT-treated diamonds, this stone has a natural-looking surface. Photo by Jian Xin (Jae) Liao.

High-pressure, high-temperature (HPHT) annealing is a very effective method for changing the color of diamonds, particularly those with an undesirable brownish color. This treatment process has been practiced in the trade for more than 15 years. An important feature of this treatment is the etching often left behind on the diamond surfaces. Recently, one loose yellow diamond rough, weighing 2.47 ct and measuring 7.09 × 6.59 × 5.46 mm, was examined in the New York lab (figure 1). Without magnification, the rough had a vibrant yellow color and an overall clean-looking surface. Closer microscopic observation showed a very slightly etched surface, as well as some altered graphitized crystal inclusions in the diamond. Distinctive fluorescence reactions to long- and short-wave ultraviolet radiation similar to those of HPHT-processed material were observed, with a medium chalky bluish green under long-wave and medium to strong greenish yellow under short-wave UV. This was suspect, and further testing was needed. UV-Vis-NIR and mid-IR spectroscopy revealed the rough diamond to be HPHT processed.

The UV-Vis-NIR spectrum, seen in figure 2, showed a rise in absorption from 500 nm, associated with strong H3 (503 nm) and H4 (496 nm) peaks, along with a sharp H2 (986 nm) peak. These are indicative of HPHT treatment. Mid-IR spectroscopy (figure 3) revealed peaks at 1170 and 1332 cm–1, indicating that the starting material of this diamond appeared to be type IaB. The high temperature and high pressure of the treatment created isolated nitrogen with a corresponding absorption peak detected at 1344 cm–1. Occurrence of isolated nitrogen in a pure type IaB diamond is a strong indicator of HPHT treatment.

Figure 2. The yellow rough’s UV-Vis-NIR spectrum, showing H2 (986 nm), H3 (503 nm),
and H4 (496 nm) peaks, indicates HPHT treatment.

Figure 3. Mid-IR spectroscopy revealed an absorption peak at 1344 cm–1, indicating the
presence of isolated nitrogen. This occurrence and corresponding peak are characteristic
of HPHT processing.
The majority of HPHT-treated rough diamonds have severely burned, etched, and pitted surfaces. This is the first time we have seen an almost eye-clean yellow rough post-HPHT treatment. With new technologies available to diamond merchants, HPHT processing techniques are becoming more sophisticated, allowing for the retention of carat weight during the cutting process. This case serves as a clear reminder that buying rough does not assure a lack of treatment. @topic:4


Publish Year: - Title: Man-made Diamonds: Questions and Answers Abstract: A natural faceted diamond, on the left, and a man-made faceted diamond on the right. Photo by GIA

If it looks like a diamond and sparkles like a diamond, it’s a diamond – right?
These days it’s not so easy to pick out a natural diamond from among the assortment of colorless, shiny stones on display at a jewelry counter. Synthetic diamonds (also known as man-made and lab-grown) and imitation gem materials may also have a spot among the natural diamonds mined around the world. It can be confusing to know what you are looking at and what best fits what you want in a piece of jewelry.
Natural diamonds are one of nature's wonders. They can be several billions of years old, made of a single element (carbon), and are formed deep in the earth under extreme pressure and high temperature. These intense geological conditions produce the physical properties – transparency, optical appearance and hardness – valued in a cut and polished diamond.
“When it comes to a natural diamond, we are looking at something that is really a rarity and a treasure from Earth,” says Brenda Harwick, manager of on campus and lab gemology instruction for GIA. “But man-made diamonds have a place in the market as long as consumers know exactly what it is that they are buying. There are other synthetics out there – such as synthetic ruby, emerald and sapphire – so it’s not something new for the jewelry industry to have a synthetic alternative.”

A factory in Shandong, China, is producing a large number of colorless HPHT man-made diamonds for the jewelry industry. These colorless crystals are up to 3.5 carats. Jinan Zhongwu New Materials Company Ltd. Shandong, China. Photo by Jian Xin Liao/GIA
The jewelry industry uses special terms for manufactured and look-alike materials: synthetic (man-made, lab-grown or lab-created) and imitation (simulants).
Man-made diamonds are grown in a laboratory or factory. Their growth structure and atomic level defects allowing them to be readily separated from natural diamonds by a well-equipped laboratory such as GIA. Because natural diamonds and man-made diamonds have some of the same physical and other properties, even a skilled jeweler or trained gemologist cannot distinguish them by sight alone. It takes specialized equipment and trained staff in a gemological laboratory for a conclusive identification.

Cubic zirconia can be created as colorless or with color, such as these large pieces. From left: 44.49 cts, 29.86 cts and 56.60 cts. Photo by Tino Hammid
Diamond imitations only mimic the look of natural diamonds. Common simulants include colorless sapphire, colorless zircon, synthetic cubic zirconia (zirconium oxide, CZ) and synthetic moissanite (silicon carbide). Cubic zirconia and synthetic moissanite are the most important in the market. They may be natural or made in a lab, but do not share the chemical composition or physical properties of natural or man-made diamonds. Because simulants do not share those properties with diamond, they are more easily distinguished by gemologists.

Near-colorless synthetic moissanite is marketed for jewelry purposes as a diamond imitation. The faceted pieces shown here, weighing from 0.09 to 0.57 ct, illustrate the appearance of this material. Photo by Tino Hammid.
Man-made diamonds are a more common topic of discussion at the jewelry counter these days because they are being used more frequently in jewelry.
“They may be an option for some jewelry buyers as long as they are correctly identified,” says Dr. James Shigley, a long-time member of GIA’s research team who has studied and published research on man-made diamonds for decades.
It is important that you have some basic information about man-made diamonds and know what questions to ask before you shop.
What are man-made diamonds? Are they real diamonds?
Man-made diamonds have been produced for industrial purposes since the 1950s and are used in a wide variety of applications: telecommunications, laser optics, healthcare and more. In 1970, researchers at General Electric created the first, small, gem-quality synthetic diamonds that could be faceted as gems. By the mid-1980s, other manufacturers were able to grow them. Initially, they were mostly small and yellow, but the quality steadily improved, and today both colorless and colored gem-quality man-made diamonds are available to use in jewelry.

The identification of natural, man-made and treated diamonds has been the principal focus of the gem research program at GIA for more than 60 years. This is a group of natural colored diamonds (0.38 to 1.04 cts). Photos by Robert Weldon, composite by Kevin Schumacher/GIA
Robert Crowningshield, one of the pioneers of GIA’s research on diamonds and vice president of GIA for many years beginning in 1950, was able to examine some of GE’s man-made diamonds in 1970. He reported on them in a Gems & Gemology article titled “General Electric’s Cuttable Synthetic Diamonds” in 1971.
“Based on his examination of a few of these first experimentally grown synthetic diamonds, it’s amazing to me that he was able to recognize some of the distinctive visual gemological properties of synthetic diamonds – and that those are the same visual features we look at today to identify them,” Shigley says.
The material ‘diamond’ is defined as carbon atoms in a cubic structure; both natural and synthetic diamonds are made of this material.
“The vastly different conditions under which natural diamonds and synthetic diamonds form result in differences in their growth structure and in atomic level defects, so to say that they are identical is misleading,” says Tom Moses, executive vice president and chief laboratory and research officer for GIA. “If they were identical, we would not be able to tell them apart.”
But because they share essentially the same physical and optical characteristics of natural diamonds, man-made diamonds have the shine and sparkle of a natural diamond when fashioned as gems.
“One of the beautiful aspects of a polished diamond is the way light interacts with it, and it has superior hardness on the Mohs scale (which means that polished surfaces are not easily scratched or damaged),” Harwick says. “A synthetic diamond has those properties as well.”
What are they called?
Many different terms are used to describe diamonds grown artificially. Look for the use of the terms synthetic, man-made, laboratory-grown or laboratory-created. These and other terms are listed in the Federal Trade Commission (FTC) guidelines on diamonds.
“The industry uses many terms to describe them, so if you see any of these terms it’s an indication that it is synthetic,” Harwick says. “But they likely won’t use the term synthetic.”

In HPHT synthesis, a press (left) applies extremely high pressures and temperatures to a central growth chamber that contains the necessary ingredients. This results in synthetic diamond crystals with combinations of cubic and octahedral faces (center and right). Illustrations: Peter Johnston/GIA. Photo copyright: GIA & Tino Hammid
How are they made?
Man-made diamonds are produced in two ways:
High Pressure, High Temperature (HPHT): A man-made diamond is produced in a laboratory or factory by mimicking the high-pressure, high-temperature conditions that form natural diamonds in the Earth. Within a growth chamber, a source of carbon dissolves in a molten metal, and carbon atoms travel through the metal to a small man-made or natural diamond seed to produce a distinctively shaped man-made diamond crystal.
Chemical Vapor Deposition (CVD): A man-made diamond is produced in a laboratory utilizing carbon-rich gas (such as methane) in a vacuum chamber. The CVD process involves breaking down the molecules of methane gas into carbon and hydrogen atoms, which then are deposited on diamond seeds to produce a square-shaped, tabular man-made diamond crystal.
Like natural diamonds, synthetic diamonds can be subjected to treatments to change their color, or to improve their face-up appearance and clarity,” Shigley says.

In CVD synthesis, microwaves split apart the hydrocarbon molecules fed into the reactor (left). These fragments migrate down to the colder diamond seed and attach to the growing diamond surface.. The synthetic diamond grows in thin layers, and its final thickness depends on the amount of time allowed for growth. This results in flat, tabular crystals (center and right) with exteriors coated in black graphite. Illustrations: Peter Johnston/GIA
How long does it take to make a diamond?
It typically takes a few weeks to make a man-made diamond in the laboratory. This is a much shorter period than a natural diamond spends in the Earth, which can be millions or billions of years.
Where are they made?
“We believe that commercial production of synthetic diamonds for jewelry use is taking place in China, Ukraine, Russia, Japan, the United States, and perhaps elsewhere,” Shigley says.
What’s the difference?
Natural diamonds display differences in their properties from man-made diamonds due to the different growth conditions in which they form.
Crystal Shape: The temperatures for natural diamond crystal growth and diamonds made in the laboratory are similar, but diamonds grow as octahedral (eight equilateral triangular faces) crystals and man-made diamonds crystals grow with both octahedral and cubic (six equivalent square faces) crystals.

Natural and man-made growth environments result in diamond crystals with distinctive shapes. From left is a comparison of CVD, HPHT and natural diamonds. Octahedral faces are shown as yellow and cubic faces blue. Most natural diamonds grow as octahedral (right), but HPHT diamonds (center) typically show a combination of cubic and octahedral faces. Octahedral faces are completely absent in CVD diamonds (left). Directions of crystal growth are shown by arrows. Dotted lines represent the position of the seed crystal in the HPHT diamond and the edges of the crystal in the CVD diamond. Illustration by Peter Johnston.
“Cube faces grow more quickly than octahedral faces," Shigley says. “They are preserved on synthetic diamonds, but they are not preserved on natural diamonds.”
Diamonds grow differently, depending on the growth environment:

Natural diamonds grow outward on the octahedral faces
HPHT synthetic diamonds grow outward on the octahedral and cube faces
CVD synthetic diamonds grow mainly upward in one direction (a cube face)

A comparison of rough diamonds shows a 0.83 ct natural diamond crystal on the left and a 1.02 ct HPHT crystal on the right. Both crystals are from the GIA Research Collection. Photo by Orasa Weldon.
Inclusions: Natural and man-made diamonds can exhibit various inclusions (fractures, breaks, other crystals, hollow tubes) so they are not always diagnostic tools for gem identification, Shigley says.
Color: Man-made diamonds are commonly colorless, near-colorless, light to dark yellow or yellow-brown; they are less commonly blue, pink red or green. Man-made diamonds can be subjected to the same color treatments as natural diamonds, so any color is possible.
Clarity: Man-made diamonds can be from low to high clarity.
Cut: The cut of a man-made diamond is the same as a natural diamond – any cut is possible. Round brilliant is the most common shape and cutting style of colorless man-made diamonds.
Colored man-made diamonds and larger man-made diamonds are more often fashioned into a fancy shape to retain more weight from the original crystal. The shape of the crystal also influences the choice of faceting styles.
How big are they?
Man-made diamond producers are capable of growing all different sizes, from melee up to 10 carats or more, Harwick says. Typically, most commercial sizes are less than 2 carats, except for melee-size, which can be abundant.
Man-made polished diamonds fall into three size categories, according to Shigley:

Large size (approximately 5-10 carats or more): These cut stones attract media attention, but they are quite rare and are likely to have been examined and correctly identified by a gem-testing laboratory.
Commercial size (approximately 0.25 to 2.5 carats): These cut stones are more abundant, but again, they are likely to be submitted to a gemological laboratory for evaluation where they should be recognized.
Small or melee size (approximately 0.10 carats or smaller): These cut stones are the most abundant, and because of their small size, they will be more difficult to detect and are not often tested – this is the real identification challenge facing the jewelry industry

A variety of large, commercial and melee cut man-made gemstones are available in the market. These HPHT diamonds, from left, are 0.41 ct, 0.31 ct and 0.50 ct. and three melee-sized stones. Photo by Orasa Weldon/GIA
How does GIA identify and grade man-made diamonds?
Man-made gem diamonds have been extensively studied by gemological researchers for the past 30 years, and much is known today about how they are grown and how they can be identified (there is a lot of published information that has been widely distributed).
“Synthetic diamond identification means distinguishing a natural diamond that formed over a long time, and very long ago, from a synthetic diamond that formed very quickly and very recently,” Shigley says.
GIA has screened every diamond submitted to its laboratory for grading for more than a decade to determine if it is natural or potentially man-made or treated. Following the initial screening, any diamond that is potentially man-made or treated undergoes rigorous examination to confirm if it is natural or man-made, and what treatments – if any – have been applied.
GIA can definitively identify both HPHT and CVD-created man-made diamonds.

All items submitted to GIA for diamond grading services are examined using the GIA DiamondCheck™ to determine if the material is a natural diamond; a diamond that may require further testing for treatments or may be man-made; or non-diamond material. Photo by Jian Xin Liao/GIA.
What will a GIA grading report tell me?
GIA began to offer a report service for synthetic diamonds in 2006. These Synthetic Diamond Grading Reports, which GIA continues to offer, are distinct from GIA grading reports for natural diamonds in both their appearance and the information provided. They clearly identify that the diamond is man-made or laboratory-grown, and they evaluate color and clarity using descriptive ranges rather than the specific grades of the color and clarity scales.
“When these reports were introduced, there was a range of opinion in the trade about GIA grading synthetic diamonds,” Shigley says. “Since synthetic diamonds continue to be rare, and to differentiate them from what is reported on grading reports for natural diamonds, only color and clarity ranges are used.”
In addition, the man-made diamond’s girdle is laser inscribed with its report number and a statement that the stone is laboratory- grown. GIA does this for every man-made diamond identified in its labs.
“The inscription on the girdle can be key to its identification,” Harwick says.
The reports also use the other Federal Trade Commission (FTC) approved terms – man-made and lab-grown – for synthetic diamonds.

There are legal and ethical requirements that a jeweler must disclose a gem’s identity at the time of sale. This helps ensure consumer confidence in what they are purchasing.
Considering a man-made diamond … what to expect?
Make sure you go to a reputable jewelry store with professionally educated gemologist to purchase any diamond jewelry. They can act as your guide as you look at natural and man-made diamonds.
“A sales associate should articulate or represent and disclose accurately what they are presenting to you. If they are calling it ‘diamond,’ you are assuming it is natural,” Harwick says. “[If it’s not natural] they need to be forthcoming in their description and are required by the FTC to call it laboratory-created, synthetic, laboratory-grown or manufacturer-created.”
Ask the sales associate if it is a natural or man-made diamond and how they know this information.
“Synthetic diamonds may be difficult to recognize by a jeweler or a trained gemologist, but they do not present an identification challenge for GIA,” Shigley says. “There are a variety of instruments being offered to jewelers so they can check for synthetic diamonds, but GIA does not use them so it is not appropriate for us to comment on their operation or accuracy.”
Ask for a diamond grading report from a recognized gemological laboratory – these clearly disclose the identity of the diamond. GIA reports for natural and synthetic diamonds look very different.
“When you’re making an investment in something as precious as this, you should ask for a grading report,” Harwick says.
How much do man-made diamonds cost in relation to their natural counterparts?
Russell Shor, senior industry analyst for GIA, says that producing man-made diamonds, either by HPHT or CVD methods, is quite costly.
“The fact they can be sold for a third or less than a natural diamond suggests they are often priced relative to natural diamonds, rather than priced in a way that reflects a true market for synthetics,” Shor says. Like most technologies, however, he notes that innovations may bring down production costs and, accordingly, the demand for them will increase.

These colorless CVD-grown synthetic diamonds can appear the same as natural diamonds to the unaided eye, making proper identification by a gemological laboratory important. Photo by Jian Xin (Jae) Liao/GIA
What is the future potential of man-made diamonds?
No one knows for sure if man-made diamonds will become a popular choice for shoppers long-term. There are personal choice issues for each buyer to consider before they purchase one.
“It is up to the preference of the consumer whether they purchase a natural or synthetic diamond, however, proper disclosure about the nature of their stone is paramount,” says Wuyi Wang, director of GIA’s research and development. “As long as the origin of the diamonds is fully disclosed, consumers and the market will determine the future for synthetic diamonds.” @topic:4


Publish Year: 2017 Title: Interesting Growth Structure in Black Diamond Abstract: Figure 1. This 1.03 ct opaque round brilliant cut was identified as a black diamond. Photo by Yujie Li.

The color of most black diamonds is attributed to graphite micro-inclusions or metallic inclusions (S.V. Titkov et al., “An investigation into the cause of color in natural black diamonds from Siberia,” Fall 2003 G&G, pp. 200–209), and it is rare to see dense clouds of micro-inclusions producing a black appearance (see Spring 2007 Lab Notes, pp. 52–53). Since November 2016, the National Gemstone Testing Center (NGTC) in Shanghai has routinely received large quantities of polished black diamonds. One such stone, a 1.03 ct opaque round brilliant (figure 1) that we believed to have been heat treated, had a striking pattern of micro-inclusions we had never seen before.

Figure 2. The “double cross” pattern seen in the black diamond. This pattern showed that the small inclusions were restricted to certain sectors, indicating that the diamond crystallized through two separate processes. Photo by Yujie Li; field of view approximately 4 mm.
Microscopic observation revealed a “double cross” pattern arising from an abundance of pinpoint-like gray inclusions restricted to certain sectors of the diamond (figure 2). The outer black cross was oriented in the same direction as the inner pale cross. The inclusions’ crystalline forms were too small to resolve at 40× magnification. These small inclusions absorbed a large proportion of the light entering the diamond, causing the black appearance. The FTIR absorption spectrum confirmed the diamond was type IaAB and H-rich, with nitrogen-related absorption from 1000 to 1500 cm–1, a graphite-related peak at 1582 cm–1, and H-related IR peaks at 1405, 2785, 3050, 3107, 3154, 3236, 4169, and 4496 cm–1. We confirmed that the pinpoint-like inclusions were graphitized hydrogen clouds (see P. Johnson et al., “Hydrogen rich treated black diamonds,” poster presentation at Geological Society of America 2016 annual meeting).

Figure 3. The pattern as seen in the DiamondView. The well-developed cuboid growth sectors exhibited yellowish green fluorescence, while the poorly developed octahedral growth sectors were inert to the short-wave UV light. The DiamondView also revealed a mixed-habit growth structure.
When observed in the high-energy short-wave UV radiation of the DiamondView (figure 3), the bulk of this black diamond displayed moderate yellowish green fluorescence. Four small areas were basically inert to UV radiation; these also corresponded to the dark cross.
The unique double cross pattern and the DiamondView image revealed an interesting growth structure. The diamond apparently underwent two distinct phases of growth, with each phase forming a cross developing from separate mixed-habit growth with contemporaneous cuboid and octahedral sectors. The well-developed cuboid growth sectors contained regions with cloud-like light scattering that caused the black parts; very poorly developed octahedral growth sectors with a small amount of inclusions formed the light cross. The cuboid growth sectors exhibited yellowish green fluorescence, while the inclusion-poor octahedral sectors were inert to the short-wave UV light.

The interesting pattern of inclusions and distinctive growth features of black diamonds such as this one needs more attention.

Contributors’ note: This study was supported in part by the National Natural Science Foundation of China (grants 41473030 and 41272086). @topic:4


Publish Year: - Title: 10 Tips for Buying a Diamond Online Abstract: Engagement rings are one of the most popular choices to showcase a diamond, but regardless of the setting, you can shop with confidence online by following our tips. Courtesy of John O'Hara.

Consumers have more options than ever when it comes to buying diamonds. In addition to jewelry retailers, you can shop from your computer, tablet or smartphone. Many of the same considerations apply whether you’re buying a diamond in person or online, but GIA has a few additional tips for shopping online that will help you click the “Buy Now” button with confidence.
1. Research and learn
As with any significant purchase, start by researching your options. Educate yourself about the 4Cs and determine which diamond qualities are most important to you. This decision, along with your budget, will help guide your diamond purchase.

2. Look for specifics
When shopping online, make sure you know exactly what you are buying. Some sites show diamonds with a range in carat weight, color or clarity. To ensure you know the value of the stone you’re purchasing, look for specifics on its 4Cs, not a range.
Diamond Buying Guide Infographic

GIA Color Grading

GIA Clarity Grading

GIA Cut Grading

Carat Weight

3. Look for a grading report
Make sure the diamond comes with an independent grading report, like those provided by GIA, which provides an unbiased analysis of the diamond’s 4Cs. A diamond’s value is largely determined by quality, so an objective, third-party assessment of the 4Cs is critical.
4. Verify the GIA report with Report Check
If the diamond comes with a GIA report, you can verify the report details on Report Check, GIA’s secure, online database and even print out a facsimile of the report, when available. It’s a convenient way to make sure that the online product description matches the grading results.
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		The GIA Diamond Grading Report provides a full assessment of a diamond’s quality using the 4Cs. View a sample report.
5. Look for a laser inscription
For added security, find out if the diamond’s grading report number is laser-inscribed on its girdle. In some cases the diamond will be inscribed before it is offered for sale, or it can be requested at the time of purchase. In addition to the diamond’s unique GIA report number, the inscription can be a personal message or symbol for identification. The microscopic inscription is viewable under 10X magnification, using a jeweler’s loupe, and because it’s noted on the diamond’s GIA report, it will help ensure that the diamond you receive matches the report issued for it.

Microscopically inscribing the report number on the diamond’s girdle makes it possible for you to easily identify your diamond in case it is ever lost or stolen.
6. Know the seller
Once you’ve decided on the diamond that’s right for you, there are a few quick checks to do on the company you’re considering buying from. You’ll want to know:

How long has the company been in business?
What kind of reviews has the company received?
Does it belong to any jewelry trade associations? (Associations often have ethical guidelines members have to meet.)
Do they offer secure transactions?
Are the online representatives helpful?
What is the return policy?
Where is the seller located?
How will the diamond be shipped? Is the shipment insured? Is signature required for delivery?
In addition to the above, if you’re buying from online auction sites, you’ll also want to look into buyer feedback and ratings and determine if the seller is providing sufficient evidence of the quality of the diamond offered for sale, such as photographs, a grading report, or report number that can be verified

7. Consider the payment method
Each online retailer or auction site will specify how it will accept payment. If you paid with a credit card and if there is a problem with the purchase, most credit card companies provide recourse. Using a check or a money order for your purchase can reduce your options.
8. Proceed cautiously with out-of-country online sites
For example, U.S.-based consumers have options for recourse when buying from a U.S. based company, such as filing complaints with the Federal Trade Commission (FTC), Jewelers’ Vigilance Committee (JVC), Better Business Bureau (BBB), etc., or pursuing a legal case in civil court. Websites that do not have a physical presence in your home country may be insulated from recourse and attempts to recover funds can be frustrating.
9. Get the diamond appraised
Once your beautiful diamond is in-hand, have an independent appraiser confirm that it matches the seller’s description and accompanying paperwork. The appraiser will also provide you with the value of the diamond for insurance purposes.
10. View the diamond in person
The convenience of online shopping can’t be beat if you’re researching your options and trying to narrow your choices. Be aware that diamonds that appear to be almost identical on a grading report − same color, clarity or cut grades − may look different from each other when viewed in person. Ultimately, your decision is a personal one, so seeing the diamond with your own eyes is the best way to determine if it’s right for you. So look for online sellers with retail stores and/or easy and flexible return policies.

The vast majority of online diamond purchases go smoothly. Follow the recommendations above to greatly increase your chances for a stress-free and secure online diamond purchase.

For more diamond buying tips, visit the GIA 4Cs Blog. @topic:10


Publish Year: 2017 Title: Kyanite: A Rare Blue Guest in Diamond Abstract: A deep blue kyanite crystal inside a 2.23 ct diamond identifies its host as being of eclogitic origin. Photomicrograph by Nathan Renfro; field of view 2.18 mm.

Few landscapes in the micro-world of minerals are as exciting as those encountered within diamonds, which can tell us much about the world from which this most precious of gems originates: the otherwise inaccessible deep earth (J.I. Koivula and E.A. Skalwold, “The microworld of diamonds: Images from the earth’s mantle,” Rocks & Minerals, Vol. 89, No. 1, 2014, pp. 46–51). Of the minerals found as inclusions in diamonds, a few are very deeply colored, due to their strong saturation at any dimension (e.g., red chromium-containing pyrope or a vivid green diopside) or their relatively large size (e.g., olivine crystals that are less saturated with diminishing size, ultimately becoming colorless). While ruby is considered one of the rarest inclusions encountered in diamond, inclusions that are vivid blue hold a similar rank. When discovered in routine examination of a diamond gemstone, they elicit not just breathless appreciation for their exquisite hue, but also anticipation of what they might turn out to be.

So it was with great interest that we examined an intensely saturated rounded blue inclusion within a 2.23 ct diamond (see above), a rarity greatly exceeding that of a flawless diamond gemstone. In this case, Raman analysis was used to non-destructively identify the crystal as kyanite, a mineral that occurs only in diamonds of eclogitic origin. This crystal is remarkable for its size (about 0.60 mm long), which in part accounts for its deep color; smaller crystals range from pale blue to colorless. Such colored mineral inclusions in diamonds should not be regarded as imperfections, but rather as hallmarks of beauty and as windows into our planet’s deepest secrets. At the very least, they are a compelling invitation from the micro-world to embark on a fascinating scientific adventure. @topic:10


Publish Year: 2017 Title: Visit Europe’s First Diamond Mine Abstract: If variety is the spice of life, you’ll appreciate our Summer 2017 issue. We offer six diverse articles featuring Russia’s Lomonosov diamond mine, carbonado, photoluminescence (PL) mapping, Vietnamese tourmaline, nephrite color determination, and Montana sapphire. In addition, we provide a full-color wall chart of characteristic sapphire inclusions.

Photoluminescence mapping shows great promise for detecting sophisticated diamond color treatments.

In August 2016, GIA’s Dr. Karen Smit and Russell Shor were fortunate enough to visit Russia’s Lomonosov diamond mine. This deposit is located about 60 miles (100 km) north of the historic port of Arkhangelsk, at a northerly latitude much like Canada’s Diavik mine. In our lead article, they share insight into its geology, operations, and diamond production. Rooted in younger Proterozoic rocks—similar to Australia’s off-craton Argyle lamproite pipe— Lomonosov’s two kimberlite pipes produce a high proportion of small gem-quality diamonds, including a tiny amount of highly valuable fancy colors, including pink. Named for its resemblance to charcoal, carbonado is one of the most intriguing diamond forms. In our second paper, Prof. Stephen Haggerty of Florida International University reviews his findings from a study of hundreds of examples from the only known sources: Brazil and the Central African Republic. He evaluates origin theories, including terrestrial and extraterrestrial models.

High-speed PL mapping can plot the distribution of optical centers in diamond. In his study, GIA research associate Lorne Loudin examines an unusual irradiated HPHT synthetic diamond of mixed type. He demonstrates a clear correlation between concentration of optical centers and diamond growth sectors, confirming that the technique shows great promise for detecting sophisticated diamond color treatments.

Luc Yen tourmaline is the subject of our next paper, from Nguy Tuyet Nhung of the Gemmological Center of the Vietnam Gemstone Association and a team of researchers. They survey the gem’s distribution in the area, its geology, and suitability for use as gems, carvings, or mineral specimens.

In our fifth paper, Xiaoyan Feng, senior engineer at NGTC in Beijing, and her research team use Raman spectroscopy to investigate and define color boundaries in nephrite from China and Taiwan.

Following the Winter 2016 emerald wallchart, we present the next in the series, which features some characteristic internal features of natural, treated, and synthetic sapphire. The chart is from the same team of inclusion specialists, led by GIA’s Nathan Renfro and John Koivula.

In our final article, Tao Hsu and her coauthors survey alluvial sapphire production in the U.S. state of Montana. They note the prevalence of small-scale mining and the importance of gem tourism, but indicate that larger, mechanized operations are expanding production at these sources.

Our Lab Notes section offers entries on melee-size CVD synthetics in parcels and jewelry, CVD synthetic overgrowth on natural diamond, and non-nacreous “rosebud” conch pearls. Topics in our Micro-World section include kyanite in diamond and molybdenite “phantoms” in quartz, while GNI features new gem finds such as Ethiopian sapphires and common opal from Mexico.

Please enjoy the Summer edition! @topic:10