Publish Year: 2023 Title: Misfit Diamonds: Beauty in the Imperfect Abstract: Figure 1. Alex Skachkov of Misfit Diamonds. Photo by Jennifer Stone-Sundberg.
At the AGTA show, we spoke with Alex Skachkov of Misfit Diamonds (Vancouver, Canada) about some of their unusual diamonds (figure 1). When asked what was popular, he showed us their aptly named “salt and pepper” diamonds (see also figure 5 of the Tucson 2023 overview), which contained eye-visible black and white inclusions. These had a very distinct look and were cut into various nonstandard shapes (figure 2).

Figure 2. “Salt and pepper” diamonds. Left to right: a 4.30 ct hexagonal step cut, a 5.56 ct octagonal step cut, a 3.58 natural-color orange cushion cut, and a 3.39 ct pear cut. Photo by Robert Weldon; courtesy of Misfit Diamonds.

Figure 3. Nontraditional diamond cuts and slices in a range of sizes. Photo by Jennifer Stone-Sundberg; courtesy of Misfit Diamonds.
Skachkov described the appeal of these unique and beautiful “imperfect” diamonds, particularly to younger designers and consumers. In his words, younger customers are not necessarily interested in absolutely flawless gems. Rather, many are looking for gems that charm in their distinctive and rare “perfect imperfection.” He noted that these diamonds are also a more budget-friendly option. In addition to the “salt and pepper” diamonds, we got a close look at diamonds and sapphires cut into nontraditional shapes, including slices (figure 3).
Skachkov mentioned that many of their customers now look for full disclosure of the entire mine-to-market custody chain. Misfit Diamonds provides this information whenever possible, though at times their diamonds arrive in mixed-origin parcels, with stones from a variety of global locations. Moving forward, they aim to meet the challenge of reporting full chain of custody, as they predict increasing demand for this feature. @topic:10


Publish Year: 2017 Title: Diamond with Concentric Inclusions Abstract: This 2.34 ct Fancy Intense yellow-green diamond (left) contains abundant inclusions that outline concentric octahedral growth layers. Through the table, the layers resemble nested rhombuses (center, field of view 3.54 mm). The inclusion shapes appear to be controlled by the layering, as seen through the pavilion (right, field of view 1.99 mm). Photos by Evan Smith.
As a diamond grows, layer by layer, it may incorporate small pieces of the surrounding mantle rocks as mineral inclusions. The three-dimensional arrangement of inclusions in most diamonds has the appearance of being somewhat random, with no discernible pattern. However, GIA’s New York laboratory recently examined a noteworthy exception.

A 2.34 ct Fancy Intense yellow-green type IaAB diamond was found to have abundant silicate inclusions with a more systematic pattern delineating growth layers (see above). Collectively, the inclusions outline con centric octahedral layers. The growth layers are made even more noticeable by a sort of optical graining that could be caused by layered distortions in the diamond crystal from variations in nitrogenconcentration. Many of the individual inclusions have an elongate or flattened oblate shape that conforms to the growth layering (bottom image). Thus, both the shape of individual inclusions and the collective distribution of multiple inclusions imitate the geometry of concentric octahedral diamond growth. This kind of symmetrical, growth-outlining texture is rarely observed in diamond.

The vibrant orange and green inclusions were identified as almandine-pyrope garnet and omphacitic clinopyroxene, respectively. Such mineral inclusions are distinctive of diamonds grown in an eclogite host rock, one of two common diamond rock types in the lithospheric mantle, the other being peridotite (S.B. Shirey and J.E. Shigley, “Recent advances in understanding the geology of diamonds,” Winter 2013 G&G, pp. 188–222). Diamonds like this one with eclogitic inclusions are sometimes called E-type, while those with peridotitic inclusions are denoted as P-type.

This is an interesting sample from a geological perspective. There are still many unanswered questions about exactly how diamonds form. Detailed analysis of this sample could provide valuable clues as each layer captures successive chemical snapshots of the diamond growth process. Of particular interest here is the question of how long it takes to make a diamond. It is possible that this diamond grew over the span of millions of years and the inclusions serve as an encrypted record of the process. @topic:10


Publish Year: 2014 Title: Color-Change Garnet in Diamond Abstract: Figure 1. This inclusion, a color-change pyrope-spessartine garnet crystal in diamond, appeared grayish green in fluorescent light (left) and purplish red in incandescent light (right). Photomicrographs by Meenakshi Chauhan; field of view 2 mm (left) and 3 mm (right).

The Indian Gemological Institute’s Gem Testing Laboratory recently examined a 0.30 ct colorless round brilliant-cut diamond containing an interesting inclusion. Infrared spectroscopy revealed features found in type IaA diamond, with a slight absorption peak due to hydrogen impurities. With a clarity grade of SI2, the diamond contained several colorless crystals and one surface-breaking grayish green crystal (figure 1, left). Under incandescent light, the grayish green crystal appeared purplish red (figure 1, right), displaying a strong color-change phenomenon.

Under the Chelsea filter the inclusion showed a bright red reaction, suggesting the presence of chromium. There was a polished area of the included crystal on the surface, but it was too small for us to measure the refractive index.

The included crystal did not display pleochroism under microscopic observation with crossed polarizers. Viewed in immersion, it appeared to be singly refractive. DiamondView imaging showed the fluorescence pattern of growth planes found in natural diamond (figure 2). Typical octahedral growth zones of blue N3 fluorescence were evident, with no disturbance in the zones around the color-change crystal.

Figure 2. This DiamondView image of the host diamond shows octahedral growth zones (notice the crystal inclusions). Image by Meenakshi Chauhan.
For conclusive identification of the inclusion, we sent the diamond to the Gem Testing Laboratory in Jaipur for laser Raman spectroscopy. As the color-change crystal broke through the diamond’s surface, a clear Raman spectrum could be obtained (figure 3). The peak at approximately 1332 cm–1 is assigned to diamond, and the peaks at approximately 1046, 910, 858, 637, 549, and 362 cm–1 are assigned to garnet. The 910 cm–1 peak is associated with the pyralspite isomorphous series, which is comprised of pyrope, almandine, and spessartine garnet. The inclusion was therefore identified as garnet belonging to the pyralspite series.

Figure 3. The Raman spectrum of the color-change pyrope-spessartine garnet inclusion  showed the 1046, 910, 858, 637, 549, and 362 cm–1 peaks assigned to garnet. The 1332 cm–1 peak is assigned to diamond. @topic:4


Publish Year: 2017 Title: Cape Diamond with Yellow Phosphorescence Abstract: Figure 1. This yellow-green 0.75 ct cape diamond displayed yellow phosphorescence to long-wave UV light. Photo by Sood Oil (Judy) Chia.

	Phosphorescence in a cape diamond is very rare, especially after exposure to long-wave UV light. The New York laboratory recently examined a cape diamond exhibiting yellow phosphorescence after exposure to a long-wave UV source. The 0.75 ct Faint yellow-green round brilliant is shown in figure 1.

	Cape absorption peaks were observed at 415 and 477 nm, along with a GR1 peak (figure 2, left). The IR spectrum confirmed that this was a type Ia diamond, with nitrogen aggregates detected in the one-phonon region. Hydrogen-related peaks were also detected at 1405, 2785, 3107, 3237, 4169, and 4496 cm–1. Brown radiation stains were found on the girdle. The diamond contained contacted partially graphitized omphacite crystals with cuboctahedral morphology (figure 2, right). Strong blue fluorescence and medium yellow phosphorescence were observed under a desktop long-wave UV light source. Under short-wave UV, medium yellow fluorescence was noted but phosphorescence was absent. DiamondView imaging (<225 nm excitation) also showed greenish blue fluorescence but no phosphorescence. Fiber-optic illumination revealed the blue “transmission” luminescence that occurs when a strong light travels through a diamond. The UV-Vis spectrum of such diamonds shows an absorption peak at 415 nm and a luminescence peak at the lower energy end of the peak. Such is the case with this stone.

	Figure 2. The diamond displayed “cape” absorption peaks at 415 and 477 nm along with a GR1 peak (left). It contained contact crystal inclusions of green omphacite (right; field of view 1.41 mm). Photo by Kyaw Soe Moe.

	Nearly 30 years ago, a bicolor diamond with a near-colorless central portion and light yellow tips was reported in G&G (Winter 1989 Lab Notes, p. 237). It showed very weak chalky yellow phosphorescence for approximately 10 seconds after the long-wave UV lamp was turned off. This yellow phosphorescence was observed throughout the stone regardless of its bicolor nature. Its central colorless region exhibited weak cape lines and strong blue transmission, similar to the green diamond in this note. Unlike our sample, the bicolor diamond also showed very weak yellow phosphorescence to short-wave UV. A chameleon diamond may display strong yellow phosphorescence to a long-wave UV light source (Summer 1992 Lab Notes, p. 124; Spring 2000 Lab Notes, pp. 60–61). Our sample was not a chameleon diamond, however.

	Greenish yellow phosphorescence in a chameleon diamond has been systematically measured using a spectrometer (see S. Eaton-Magaña et al., “Fluorescence spectra of colored diamonds using a rapid, mobile spectrometer,” Winter 2007 G&G, pp. 332–351). The peak maximum recorded for the chameleon diamond was 557 nm. We used an Ocean Optics USB2000 charge-coupled device (CCD) spectrometer similar to the one described in Eaton-Magaña et al. (2007), but with a different UV source. In place of a deuterium source, we used GIA’s new LED desktop long-wave UV (365 nm excitation) light source. A broad peak at approximately 570 nm, which is responsible for the yellow phosphorescence, was observed in the emission spectra (figure 3, left). The phosphorescence decay curve at 570 nm, representing the rate of decreasing intensity with time, is plotted in figure 3 (right). Half-life is defined as the time required for the initial peak intensity to decrease to one-half its original value (again, see Eaton-Magaña et al., 2007). The half-life value measured for our sample was 5.0 seconds.

	Figure 3. Phosphorescence spectra (left) show a peak maximum at 570 nm, which is responsible for the cape diamond’s yellow phosphorescence. Shown on the right is the phosphorescence decay curve at 570 nm.

	Yellow phosphorescence is a very rare feature in cape diamonds. The defect responsible for this optical feature remains unknown. @topic:4


Publish Year: 2022 Title: Omphacite in Pink Diamond Abstract: A bluish green omphacite crystal with surrounding stress fractures seen in a Fancy brown-pink diamond. Photomicrograph by Britni LeCroy; field of view 1.42 mm.
Photomicrography of colored crystal inclusions is a field of seemingly endless possibilities in the realm of colored stones. With regard to diamond, however, the possibilities are far more limited. This is due to the growth origin of diamond within the earth’s mantle—an environment few other minerals are able to endure. While colored crystal inclusions in diamond are uncommon, known possibilities include garnet, diopside, corundum, olivine, kyanite, and omphacite, the latter of which was seen in the Fancy brown-pink diamond in the above figure and identified via Raman spectroscopy.
Omphacite is a mineral within the clinopyroxene solid solution series, which also contains the members jadeite, diopside, and aegirine. It typically occurs in eclogite, a high-pressure, high-temperature metamorphic rock also containing garnet. Eclogites form from igneous oceanic crust that has subducted into the mantle. The presence of an omphacite inclusion proves the diamond formed in an eclogitic environment. This is a rare inclusion not often seen at GIA. @topic:10


Publish Year: 2022 Title: A “Galaxy” within a Diamond Abstract: Figure 1. This particle cloud, a typical inclusion in diamond, shows an iridescent appearance and is grouped in a triangular shape viewed in fiber-optic illumination. Photomicrograph by Aprisara Semapongpan; field of view 2.8 mm.
The 2.01 ct, D-color, I1-clarity type IaB diamond in figure 1 reveals an intriguing cloud of particles grouped in a triangular shape. These tiny crystal and particle cloud inclusions resemble a galaxy, as if seeing the Milky Way at night.

Figure 2. DiamondView imaging of the type IaB diamond reveals a fibrous pattern and a hazy triangular cloud area with blue fluorescence. Image by Aprisara Semapongpan.
The DiamondView image in figure 2 reveals blue fluorescence with a hazy triangular glowing area that matches perfectly with the position of the particle cloud in figure 1. Furthermore, this type IaB natural diamond displays a fibrous pattern in the DiamondView instead of the tree-ring pattern that is typical in type Ia diamond. This fibrous pattern is related to a weak B-aggregated (B-center; 4N+V) signal in Fourier-transform infrared spectroscopy.
Finding and analyzing inclusions in diamonds is fascinating, as you never know where the next diamond will lead you—perhaps you will even discover your own galaxy. @topic:4


Publish Year: 2021 Title: Asterism in Natural Diamond Cabochons Abstract: Figure 1. Photos show internal cloud inclusions in profile view (left) and asterism in top view of the polished cabochons using fiber-optic illumination (right). The diameters of the two cabochons are 11.33 mm (top) and 11.32 mm (bottom). Photos by Christopher Vendrell.
The New York laboratory received two cabochon diamonds from Hong Kong, both displaying asterism. Gemologists initially questioned whether these stones were in fact diamond because of the cabochon cutting style and the white four-rayed “stars” observed using fiber-optic illumination. The polished cabochon is a popular cutting style in colored stones but rarely attempted with diamond due to its hardness. This cutting and polishing technique yielded two semitransparent to translucent round cabochon diamonds with a very light yellow color, weighing approximately 6.29 ct and 6.07 ct (figure 1).

Figure 2. FTIR spectra reveal natural type Ia diamonds with strong hydrogen concentrations in the 3000–4000 cm–1 region and aggregated nitrogen in the one-phonon region at 1400–800 cm–1. The 6.29 ct diamond cabochon spectrum is denoted in red and the 6.07 ct diamond in blue.

Mid-infrared spectroscopy revealed strong hydrogen-related absorption bands (e.g., 3107 cm–1) and those attributed to aggregated nitrogen in the one-phonon region, evidence of natural type Ia diamonds (figure 2). Microscopic observation from the base of the cabochons revealed prevalent clouds distributed throughout the diamonds. The clouds were composed of small whitish pinpoints, and when aligned linearly formed small needle-like internal inclusions (figure 3).

Figure 3. Cloud and needle-like inclusions observed in bottom view of the two very light yellow round cabochon diamonds: 6.29 ct (left, field of view 1.8 mm) and 6.07 ct (right, field of view 6.5 mm). Photomicrographs by Christopher Vendrell.
Fluorescence images collected using the DiamondView revealed yellowish green fluorescence in the sectors with clouds. The cloud-free sectors were inert to UV radiation. Symmetrical fluorescence patterns were observed in both stones with nearly mirror images (figure 4).

Figure 4. DiamondView images of the very light yellow round cabochon diamonds reveal the location of asterism using ultra-short-wave illumination, approximately 225 nm. The top view is shown on the left in each pair of images, the bottom view on the right. Images by Christopher Vendrell and Kyaw Soe Moe.
Natural diamonds are dominated by {111} octahedral growth sectors, but occasionally the {100} cubic sector is well developed, forming a crystal with mixed growth habits. The cubic growth sector could preferentially contain a significant amount of pinpoint cloud inclusions. This feature occurs quite often in diamonds from Zimbabwe. Unlike other diamonds with clouds, these clouds concentrated in the {100} growth sectors linearly aligned to form needle-like inclusions. The distribution of these needle-like inclusions within the {100} growth sectors generated the asterism feature seen in these gem diamonds.
Gemological and spectroscopic features strongly indicated that these diamonds were cut from the same large rough diamond crystal. The crystal was very likely cut through the center along the (100) plane and then polished into two relatively large cabochon diamonds. Taking advantage of the widespread needle-like inclusions in this otherwise well-included large diamond crystal was a clever design choice to produce two cabochons displaying the rare asterism phenomena. @topic:4


Publish Year: 2022 Title: Breyite Inclusion in Diamond Abstract: A breyite inclusion in diffuse illumination. Doubling of some features to the right and left of the inclusion is an artifact of viewing through multiple pavilion facets. Photomicrograph by Evan M. Smith; field of view 1.58 mm.
Sublithospheric or “superdeep” diamonds are rare, estimated to make up only 1–3% of mined diamonds globally. They are recognized on the basis of their mineral inclusions. Breyite (CaSiO3) is one of the minerals sometimes encountered in this curious geological family of diamonds. Diamonds containing breyite are often interpreted to come from depths greater than 360 km, where the breyite would have initially had a high-pressure perovskite-type crystal structure. The perovskite-structured CaSiO3 would have changed to the breyite crystal structure in response to the drastic decrease in pressure during the diamond’s journey to the surface. Alternatively, it is theoretically possible that breyite could be trapped directly in a diamond at much shallower depths, say within 150–200 km, although such an occurrence within a known lithospheric diamond has yet to be encountered.
The breyite inclusion (see above) was recently observed in a 1.00 ct D-color type IIa diamond submitted to GIA’s New York laboratory. Raman spectroscopy was used to identify it as breyite. This large inclusion, 450 μm in its longest dimension, is colorless and transparent. A conspicuous healed fracture surrounds it, containing graphite (black) and smaller “sub-inclusions” of breyite that appear to emanate from the main inclusion. Based on this breyite inclusion, the diamond is suspected to be sublithospheric in origin @topic:10


Publish Year: 2020 Title: Formation of the “Matryoshka” Diamond from Siberia Abstract: Figure 1. The 0.62 ct green “Matryoshka” diamond (4.8 × 4.9 × 2.8 mm) from Siberia has an internal open cavity connected by two small channels to the outside. The surface is covered by etched trigons and striations. A small diamond crystal can move freely inside the cavity. Photo by Jianxin (Jae) Liao.

A freely moving diamond trapped inside another diamond was discovered in Siberia by Alrosa in 2019. The unusual diamond, nicknamed the “Matryoshka” after the traditional Russian nesting dolls, attracted widespread interest in how this feature formed.

Figure 2. The small, flat diamond crystal enclosed in the cavity showed a hexagonal outline. The surface of the small diamond was covered with groups of parallel straight striations following the diamond crystal symmetry. Photo by Towfiq Ahmed.

	Mobile diamond inclusion in the Matryoshka diamond

The 0.62 ct flat octahedral diamond, a twinned macle, was recently examined by the New York laboratory. Flat-bottom trigon etch pits were well developed on the face {111} (figure 1). The crystal showed a clear green bodycolor, with small dark green radiation stains in shallow fractures along the edges when viewed from the top of the crystal. Two etch channels on opposite sides of the edges had rectangular openings about 0.2 mm in width. The channels extended into the internal enclosed cavity. These features made this diamond unique. Trapped in the cavity was a small, flat diamond crystal with a hexagonal outline. The small diamond, covered with some green radiation stains on the surface, is entirely detached from its host crystal and can move freely inside. The surface of the small diamond was covered with groups of straight parallel striations following the diamond crystal symmetry. No etched trigons were observed on the surfaces of the small diamond (figure 2). Except for tiny foreign-material contaminations at the two entrances of the open channels, no other inclusions were observed in this crystal (figure 3).

Figure 3. An open channel about 200 μm in width connected the internal cavity with the outside. Image by Elina Myagkaya.
Absorption spectroscopy in the infrared region indicated a type Ia diamond, with high concentration of aggregated nitrogen. A moderately strong absorption at 3107 cm–1 from the N3VH defect was also observed. More detailed analysis of selected areas with and without the small internal crystal showed almost identical spectral features, confirming that the small crystal is a diamond with nearly identical trace element chemistry as the host. The UV-Vis absorption spectrum collected at liquid nitrogen temperature (–196°C) showed clear absorptions from the N3 defect (ZPL at 415 nm) and GR1 (ZPL at 741 nm). These spectral features are typical for a natural type Ia diamond, except for the strong GR1 absorption, which is attributed to irradiation. Occurrence of the small dark green radiation stains revealed that this diamond was naturally irradiated. Under various laser excitations at liquid nitrogen temperature, photoluminescence spectroscopy showed emissions at 911, 787, 741 (GR1), 700, 535, 503.5 (3H), 489, and 468 nm. Absence of emission from the H3 defect (N2V, ZPL 503.2 nm) indicated that the diamond crystal was not annealed to any elevated temperature after being naturally irradiated.

	X-ray computed microtomography of the Matryoshka diamond

X-ray computed microtomography (μ-CT) scanning and analysis revealed some very interesting observations. First, the small internal crystal showed the same intensity of X-ray absorption as the host diamond supporting the conclusion that the small crystal is a diamond. Second, CT technology can accurately compile the morphology of the internal cavity through stacked imaging. The cavity showed a flattened octahedral shape, composed of two octahedron crystals of parallel growth. The crystal habit of the void, an extremely important observation of this study, strongly indicated that the open cavity was originally occupied by another diamond crystal instead of other mantle minerals. Once crystallized in the earth’s mantle under very high pressure, it is not possible for a diamond crystal to have any internal open space. Other mantle minerals such as garnet, olivine, or pyroxenes will show entirely different crystal habits. Finally, volumes of different parts of this crystal were calculated. The external crystal was 33.16 mm3 in volume (0.58 ct), while the internal small crystal had a volume of 1.51 mm3 (0.03 ct). The total calculated weight of 0.61 ct is very close to the actual weight of 0.62 ct (excluding the contaminations at entrances of the etching channels). The volume of the open cavity was 5.99 mm3, equal to 0.11 ct of diamond originally occupying that space. Based on these calculations, the total initial weight of this crystal would have been about 0.72 ct.
In summary, this diamond crystal was initially a solid diamond without the cavity when it formed in the earth’s mantle. Due to chemical heterogeneity in trace element chemistry or sub-micro inclusions/structure (such as those fibrous diamonds), the middle part of the diamond crystal (now represented by the void) was selectively dissolved during interactions with special type(s) of melt/fluid after its crystallization. About 0.11 carats of diamond dissolved through the two small open channels that created the pathway for the internal cavity. The host diamond and the small internal diamond crystals were inactive or less active to the melt/fluid and consequently survived. Fluid with radioactive elements responsible for the green bodycolor and formation of radiation stains would have been the last step in decorating this crystal. Special chemistries and interactions with multiple types of melt/fluid subsequent to its initial crystallization led to the formation of this unique diamond in Siberia. @topic:10


Publish Year: 2007 Title: An Examination of the Napoleon Diamond Necklace Abstract: Napoléon Bonaparte gave an extraordinary diamond necklace to his empress, Marie-Louise, in 1811. Its intriguing history involves both royals and con artists (and one individual who was both), and it was ultimately donated to the Smithsonian Institution in 1962. Infrared absorption analysis of 101 stones in the necklace revealed that a high proportion of the larger diamonds are the relatively rare type IIa; most of the smaller stones are type IaAB. The luminescence behavior of the diamonds to ultraviolet exposure correlates with their diamond types.

	DATA DEPOSITORY

Table: Type and Description of the Luminescence for the 52 Main Diamonds in the Napoléon Necklace
	Submitted by Eloïse Gaillou
	Winter, 2007 @topic:10


Publish Year: 2022 Title: Hematite Crystals in Diamond Abstract: Several small brownish orange crystals found within the fracture of a diamond were identified as hematite. Photomicrograph by Abadie Ludlam; field of view 1.26 mm.
A 1.51 ct G-color diamond with I2 clarity recently caught the authors’ attention due to several brownish orange inclusions. These tiny crystals, only a few nanometers in size, were concentrated along two fractures in the stone (see above). They were identified using Raman spectroscopy as hematite (Fe2O3). Although it is common to find oxide staining within fractures in diamond, crystalline oxide inclusions such as these are a rarity. The concentration of the hematite crystals along the cracks suggests that, rather than being syngenetic inclusions, these are secondary (epigenetic) minerals. They likely precipitated inside the fractures when the diamond interacted with fluids while being stored in the crust. This rare sight offers a glimpse into the long and unique journey each diamond takes to the earth’s surface. @topic:10


Publish Year: 2021 Title: Radioactive Green Diamond Abstract: Figure 1. Green diamond treated with radioactive salts. Photo by Diego Sanchez.

The rarity of naturally colored green diamonds has created the demand for artificially irradiated green diamonds. One 2.42 ct green diamond recently examined by the author showed signs of radiation treatment by the use of radioactive salts (figure 1).

Figure 2. A mottled green appearance was visible on the table facet of the green diamond treated with radioactive salts. Photomicrograph by Nathan Renfro; field of view 4.70 mm.
Microscopic analysis revealed telltale green mottled and shallow radiation stains over large areas of the stone, causing its green bodycolor (figure 2). These radiation stains were produced by exposing a cut and polished diamond to radioactive salts for an extended period. The inert to ultraviolet light radiation stains were easily visible against the diamond’s blue fluorescence seen in the DiamondView (figure 3).

Figure 3. This diamond’s blue fluorescence provides strong contrast to the inert radiation stains, as shown by the DiamondView. Image by Michaela Stephan; field of view 8.265 mm.
Treatment using radioactive salts (such as radium) is not often used anymore, as this method may produce dangerously radioactive diamonds. Today, most artificially irradiated diamonds are treated with a low-energy electron beam (Spring 2013 Lab Notes, pp. 46–47). When tested with a Geiger counter, this stone was revealed to be weakly radioactive. @topic:10


Publish Year: 2021 Title: Rainbow Graining in Diamond Abstract: This yellow diamond displayed a remarkable example of rainbow graining that appears and disappears as the stone is tilted. Photomicrograph by Nathan Renfro; field of view 4.64 mm.

One of the more subtle inclusion scenes gemologists sometimes observe in natural diamonds is the presence of crystallographically oriented structural defects known as “internal graining.” Often resulting from octahedral and cubic growth sectors of a diamond crystal competing for space during growth, these structural disconformities present as colorless, whitish, reflective, colored, and rarely rainbow varieties of graining (J.I. Koivula, The Microworld of Diamonds, Gemworld International, Northbrook, Illinois, 2000). Colorless graining is the most common type encountered, while whitish graining is somewhat less common and shows, as the name implies, a hazy white appearance in the immediate area of the structural defect zone. Colored graining often occurs when plastic deformation along the cleavage direction results in color causing defects in the diamond crystal lattice. If the defects are numerous enough, they can impart a bodycolor, which in the case of pink and red diamonds greatly enhances their value. Reflective graining occurs as a result of excess strain buildup from the crystallographic defects. The diamond’s accumulated strain is released by separating along cleavage planes, leaving a reflective, mirror-like separation as the most obvious characteristic of this type of graining. The rarest of all types is known as “rainbow graining.” In these remarkable stones, the structural defects in the diamond’s crystal lattice are ordered layers, which act as a diffraction grating to reveal a vibrant display of spectra colors (Summer 2007 Lab Notes, p. 155).

	Rainbow Graining in Diamond

Recently, the author had the opportunity to examine a spectacular example of a yellow diamond containing prominent rainbow graining (see video above). When the stone was rocked and tilted, the rainbow colors would appear and disappear. The elusive beauty of this type of graining and the difficulty with which it is observed make this type of graining a rare and welcome sight in natural gem diamonds. @topic:4


Publish Year: 2021 Title: Xenomorphic Olivine Inclusion in Diamond Abstract: This three-spoke radial inclusion of olivine owes its unique morphology to the extreme temperature and pressure applied to it. This mineral inclusion forced to adopt the shape of its host is an example of xenomorphism. Photomicrograph by Nathan Renfro; field of view 2.25 mm.

The author recently examined a faceted diamond that contained an oddly shaped near-colorless crystal with a low-relief tension crack surrounding it. The inclusion was identified by Raman spectroscopy as olivine, a rather common inclusion in diamond. The remarkable thing about this particular example was its shape, which consisted of three spokes intersecting at approximately 120° (see above). This is not the shape one would typically associate with the orthorhombic mineral olivine, but there is an explanation for the unusual morphology of this inclusion.
As diamonds form at extreme temperature and pressure conditions, they can impose their morphology on syngenetic minerals that become included in them. When a guest mineral adopts the host diamond’s morphology, this is known as xenomorphism. The triangular morphology seen here suggests that the olivine inclusion is oriented parallel to an octahedral crystal face of the host diamond crystal. This is one of the most unusually shaped inclusions observed in diamond examined by the author. @topic:10


Publish Year: 2021 Title: Phenakite as a Diamond Imitation Abstract: Figure 1. A set of phenakite gems ranging from 0.20 to 0.98 ct, with a total weight of 5.85 carats, sold as diamonds. Photo by J. Hyršl

              In my gemological laboratory, I see some interesting imitations from time to time. The latest was quite unusual: a set of 12 loose stones submitted as diamond (figure 1) for certification. Testing their thermal conductivity with a Presidium Gem Tester and their electrical conductivity with a Ceres Secure II device indicated diamond and ruled out synthetic moissanite. The next property examined was fluorescence, and all the stones were completely inert to both short-wave and long-wave UV. It would be unusual for a group of 12 natural diamonds to all be inert, so the next step was determining whether they might be laboratory-grown diamonds. Working under the assumption that they were indeed diamonds as submitted, the stones were tested for short-wave UV transparency and all were very transparent, suggesting they could be type IIa (which would be consistent with laboratory-grown near-colorless diamonds). Finally, I performed Raman analysis; instead of a sharp diamond peak at 1332 cm–1, it showed only a small peak at 878 cm–1, indicating that these stones were not diamonds.

Only then did I remember a natural crystal of phenakite, sold as diamond, that I tested a few years ago. It was very similar to natural rough diamond, but instead of typical trigons, it had a surface covered by many rhombs. But its thermal conductivity was the same as diamond’s, and therefore it was a plausible diamond imitation for a mineral or gem dealer without knowledge of crystallography. When I remembered this, the identification was easy—the refractive index of the loose cut stones was 1.655–1.670, and the Raman line matched very well with phenakite. And upon further examination, the stones appeared doubly refractive in the microscope and polariscope.

Phenakite is trigonal Be2SiO4, colorless, and similar to beryl. Normally it forms hexagonal prismatic crystals that look very different from diamond. Nevertheless, some crystals from Nigeria are irregularly developed (figure 2) and could be mistaken for a rough diamond without careful examination, especially if mixed with real diamonds.

Figure 2. Natural phenakite crystal from Nigeria, width 38 mm. Photo by J. Hyršl.
Cut stones are quite rare and well known only to collectors of rare gemstones. Distinguishing a cut phenakite from diamond is quite easy when one can measure refractive index, see a double refraction in the polariscope or microscope, or calculate weight from measurements. Much more difficult would be phenakite set in jewelry, where it can be very difficult to measure RI. Cut phenakite has much lower brilliance than diamond, of course, but can resemble low-quality cut diamonds. @topic:4


Publish Year: - Title: Diamonds Under the Scope Abstract: Cloud inclusions are relatively uncommon in diamonds. They can be beautiful and complex, like this dramatic hydrogen cloud, masquerading as a Venetian mask. Photo by John I. Koivula/GIA

Another world exists in gemstones when they are viewed through a microscope. Landscapes and whimsical creatures appear to come to life as you explore a gem’s internal features and formations.

Inclusions spin a tale of provenance and tell of the diamond's journey from deep within the earth to the surface. They are a geological time capsule that tells a story of a gem’s formation. Feather inclusions in a diamond, for example, can be indicative of a rough ride from the earth’s mantle to the surface. These birthmarks are signs of a diamond’s natural origin and make your diamond unique in the world.

In 1645 an Englishman saw a red crystal inclusion (probably a garnet) in a diamond belonging to a Venetian nobleman by the name of Rugini. This discovery sparked an interest in colored crystal “guest” minerals or inclusions in diamond. A number of crystal mineral inclusions have been reported since then.

"Inclusions impart character, beauty and essence to their host gems."
Dr. Edward J. Gübelin

The renowned Swiss gemologist Dr. Edward J. Gübelin (1913-2005) built a legacy on the study and systematic classification of the internal world of gemstones. His research demonstrated the importance of these internal features in determining a gem’s identity.

John I. Koivula, GIA’s analytical microscopist and longtime chief research gemologist, wrote to Dr. Gübelin as a teenager, sending along his first photomicrographs (photos taken through a microscope). This began a collaboration that would culminate in the three-volume "Photoatlas of Inclusions in Gemstones," landmark works that established the importance of inclusions as an aid to identifying gemstones. Their photomicrographs of inclusions illustrate common features in gemstones from particular localities. Their richly illustrated tomes also help separate natural from synthetic or treated gemstones, including diamonds.

Diamonds present some of the most striking inclusions to view under the microscope and host a variety of gemstone guest crystals. Some of the most frequently found are pyrope garnet, olivine or peridot, diopside, chrome-spinel, and much less frequently, ruby and sapphire. Diamond crystals are also frequently seen as inclusions within diamond itself.

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Let your imagination take flight as you view the diamonds in this gallery.

The study and documentation of inclusions in diamond has inspired poetic and descriptive names: feather, cloud, halo, knot, needle, bearding and pinpoint.  With magnification, these scenes are clues to the natural origin of a diamond and give you a renewed appreciation for its characteristics and qualities. The possibilities of what you can see in these photomicrographs is almost endless. @topic:10


Publish Year: - Title: What Country Do My Diamonds and Other Gemstones Come From? Abstract: Dr. James Shigley, GIA Distinguished Research Fellow, giving a lecture for students and the public on “Gemstone Country of Origin Reporting” March 2020 at GIA in Carlsbad. Photo by Emily Lane/GIA

“Since 1931 (GIA’s founding), we have shared everything we have learned with you.”

This quote from Richard T. Liddicoat, GIA’s legendary second president, is how Dr. James Shigley began his recent lecture, “Gemstone Country of Origin Reporting.”

“It is the best short description of why GIA is here,” said Shigley, who is GIA’s distinguished research fellow and holds a Ph.D. in geology from Stanford University. Shigley proceeded to share everything (or many of the things) he’s learned about gemstone origin in his 37 years working in GIA’s research department. He focused most of his presentation on colored stone origin identification, which is detailed in a special Winter 2019 issue of Gems & Gemology (G&G) on country of origin.

“Country of origin reporting [for colored stones] is probably the most difficult challenge we have in the lab for identifications purposes,” Shigley said.

GIA researchers are uniquely able to offer insight into colored gem origin, he explained, because of the sheer volume of stones they see in the lab and in the field. In the past decade, GIA field researchers have gone on 95 field expeditions to 21 countries and collected more than 22,000 samples totaling more than 1 million carats. GIA also has 60 researchers on staff, including more than 20 with doctoral degrees in fields such as geology, chemistry and material science.

The knowledge gained from these field expeditions is part of the “foundation” of the information GIA can provide to the gem trade in its colored stone report service, Shigley said. The GIA Colored Stone Identification and Origin Report has been around for decades, but the GIA Diamond Origin Report is relatively new.

A ruby crystal in calcite, left, and a round cut ruby, both from Myanmar (formerly known as Burma). Specimen courtesy of the Dr. Eduard J. Gübelin collection. Photo by Robert Weldon/GIA
How Does GIA Determine Where Colored Gems are From?
“It’s important to recognize that a country of origin report is an expert opinion. We [often] weren’t there when it [the gemstone] was found,” Shigley said. “It is an expert opinion based on examination of the sample that is presented to us.”

The assumption is that stones from different places should have different gemological properties he said, but it “doesn’t always pan out that way.”

Shigley reviewed some of the challenges of country of origin reporting for colored gemstones:

The geology of the gem deposit is often not well known and many are alluvial occurrences have an uncertain source (“We don’t know where the original host rock is located,” he said. “it could be miles and miles away.”)

Access to the deposit may be difficult.

Gem deposits do not stop at country borders.

Deposits in different countries can produce very similar material (such as sapphires from Madagascar, Kashmir and Sri Lanka).

Different deposits can be found in the same country.

“What these challenges show,” Shigley said, “is that the geology determines the gemological properties — the inclusions, the chemistry and all of the other properties of the gem material.”

Country or geographic origin reporting began in the 1950s when the famous Swiss gemologist Eduard Gübelin started to provide letters about where the stones his company was selling came from, Shigley said. Gübelin also wrote a series of articles for G&G on how inclusions can help you determine where colored stones come from.

A 7.04 ct oval sapphire from Madagascar. Sapphire is courtesy of Mayer & Watt, Maysville, Kentucky. Photo by Robert Weldon/GIA
Building on what researchers have learned and documented in the past, GIA created a field gemology program a decade ago to “go to where the gems are,” Shigley said. They are collecting samples to build a reliable database, videotaping and photographing the area and interviewing miners to get a complete picture of what’s going on in that particular time and place. He said this program is the foundation of GIA’s Colored Stone Country of Origin Reports, and it provides valuable information for GIA education courses.
While colored gemstones continue to be found in Australia, Brazil and Columbia, in many cases today they are found in two regions of the world. The first is the arch of countries between the Indian subcontinent and Asia (Iran, Pakistan, Afghanistan, northern India, Myanmar, Cambodia Vietnam and Thailand) that represent the collision zone between India and Asia — this collision zone produced the metamorphic and magmatic conditions necessary to form gem deposits. The second region represented is Eastern Africa (Ethiopia, Somalia, Kenya, Tanzania, Madagascar, Mozambique), as well as Sri Lanka and southern India — another continental collision zone with the right geologic conditions that produce gem deposits.

Two Madagascan miners look through river gravel for sapphires. This photo was taken on a GIA Field Expedition to Madagascar in September 2010. Photo by Vincent Pardieu/GIA
GIA field gemologists travel to these countries to collect gem specimens for research. These specimens are classified according to how closely they are collected to the source:

Type A ‒ collected onsite by a GIA gemologist

Type B ‒ the gemologist witnesses the samples being mined

Type C ‒ samples are purchased from a miner at the mining site

Type D ‒ samples are purchased from a miner but not onsite

Type E ‒ samples are purchased from a secondary source (not the miner) close to the mine

Type F ‒ samples are purchased from a secondary source on the international market

Most of the samples GIA collects are Type D or E, supported by types A, B and C when available. These samples are taken back to the lab so researchers can study their color, fluorescence, inclusions, growth zoning, chemical composition, spectra (visible and infrared), Raman spectroscopy and photoluminescence. These stones are also photographed, often at 100x magnification, so their inclusions and other visual features are recorded. The data collected lets scientists determine the cause of color in the gem material at hand, which helps to determine origin or to classify gemstones into different types.

This emerald crystal buried in its host rock was found in Colombia, the world’s largest producer of emeralds. Photo by Orasa Weldon/GIA
The instruments needed to collect all of this data, such as the scanning electron microscope and the laser-ablation mass spectrometer, cost anywhere from $100K to $1 million each. Some of these instruments are able to detect very tiny quantities of trace elements in the parts per billion (PPB), and can pick up elements that are unique to certain countries of the world. The greatest challenge in collecting data on gemstones is using non-destructive ways to analyze gemstones.
Another challenge to gemstone origin determination is that countries are continually being added to the list as gemstones are discovered at new locales, so GIA field researchers are always on the march to document more gemstones. Shigley used ruby as an example of how the discovery of new deposits have increased over the years: in 1950 there were eight known ruby sources in the world, today there are 30.
“They don’t necessarily produce the best quality of material, but material from all of these deposits are in the market and may show up here for an origin report,” he said. “The challenge is the growing number of localities with very different geology — and sometimes with very similar geology.”
“The database is accessible in GIA’s identification laboratories for comparison with client stones for country of origin services. Each expedition expands the database and improves the reliability of the reference collection and GIA’s laboratory services.”
Can GIA Figure Out Where a Diamond is From?
Shigley also discussed how determining colored stone country of origin differs from determining country of origin for diamonds, which is nearly impossible, because once a diamond is cut, there are no distinctive features to determine where it came from.

“We cannot tell where a diamond comes from based on the diamond itself,” Shigley said.

Certain mines, however, are associated with a certain size or quality of diamond, e.g. the Cullinan Mine in South Africa, which is renowned for having produced several legendary large, high-clarity diamonds, including the Cullinan, the largest diamond rough ever found. The Argyle Mine in Australia has been the world’s primary producer of pink diamonds for decades.

The 302.37-carat Graff Lesedi La Rona diamond was found in Botswana. The provenance of large, high-quality, record-breaking diamonds tends to be easier to track. Diamond courtesy of Graff and photo by Donald Woodrow

Shigley outlined the main reasons why it is impossible to determine the geographic origins of diamond based on gemological and scientific examination.

Where they form: Diamonds form deep in the Earth, where conditions are more homogenous. Also, there aren’t any distinctive mineral inclusions associated with any particular location.

Diamond structure, chemistry and analytical challenges: Diamonds are made up of carbon and sometimes a small amount of nitrogen and boron, which are next to each other in the periodic table, Shigley said, so the atoms are about the same size and can easily substitute for one another in the diamond structure.

“Diamond is a very close-packed tetrahedral arrangements of carbon atoms that are held together by very strong short, covalent bonds,” he said. “It is hard to get other trace elements into the diamond structure in very much quantity. [If they are there] they are very trace amounts in the parts per billion level.”

Additionally, analysis of trace elements in diamonds requires sophisticated analytical equipment and a method that may destroy part of the diamond sample. Spot analysis can be done using Secondary Ion Mass Spectrometry (SIMS), but this is “probably a million-dollar piece of equipment” usually only found at universities — GIA does not have one, Shigley said

A piece of diamond-bearing kimberlite from South Africa. Photo by Robert Weldon/GIA
Weathering: Some diamond deposits are secondary, where the diamond is recovered from a river or sediment by panning. Diamonds are brought to the Earth’s surface by an explosive eruption that forms a volcanic pipe filled with diamond-bearing igneous rock known as kimberlite. Kimberlite weathers quickly, releasing the diamonds and they go downhill, either by gravity or water, and are then carried by river systems downstream — possibly hundreds of miles away — or incorporated into sedimentary rock.

“The river takes them many miles away from their original pipe location, so we don’t even know where the pipe was,” Shigley said. “And of course, the river crosses many countries. In South Africa, it [the Orange river] transports them all the way to the Atlantic Ocean.”

Lack of a distinctive surface appearance on rough diamonds: Experienced diamond sorters at DeBeers might be able to tell which company mine a rough diamond came from based on its surface features, but this isn’t an exact art and the stones are unrecognizable once surface characteristics are removed in the gem cutting process.

Shigley said the real problem of diamond origin is: Where are you going to get diamonds to study to develop your criteria for country of origin identification?

“You would need a representative sample of diamonds from all of the mines in the world and all of the secondary deposits in the world. And what’s a representative sample — is it 3 or 300 diamonds [from each location]?” he said. Additionally, once you have representative samples, they would have to undergo destructive testing.

“There is no database of rough diamonds available to anyone to tell where they are from and I don’t know of any way, scientifically, to tell where a polished diamond comes from,” he said.  “The database of samples, if it existed, would provide a source of information to try and develop ideas for country of origin determination for diamonds,” he said, adding that the lack of diamonds from secondary alluvial deposits “is a particular problem because of the lack of organized mining efforts and the random finding of diamonds.”

The Diamond Origin Report offers a 4Cs quality analysis as well as confirmation of origin to the gem trade. Pictures of the original rough can be viewed online or on the 4Cs app.
It’s in the leap from rough to polish that GIA breaches the gap. GIA works with diamond mining companies in major diamond-producing countries such as South Africa, Russia, Canada, Namibia, Lesotho and Australia to offer the GIA Diamond Origin Report Program to the gem trade.

“It’s more of a matching service,” Shigley said. GIA takes a rough diamond that comes in a sealed parcel from a client or program participant with its required origin documentation. GIA characterizes it so it is able to later match it to a cut stone submitted for the origin service. The country of origin information confirmed on the report comes directly from the mine.

‘We are saying [on the report] that this is where it is from and we can definitively match it with the original rough diamond,” Shigley said.

GIA matches the gems to their original rough according to their size and color, measurements, gemological observations, absorption and luminescence spectroscopy, fluorescence imaging and information in the GIA database. Each GIA Diamond Origin Report also contains a 4Cs quality analysis in addition to a statement of origin.

GIA has issued nearly 20,000 diamond origin reports. @topic:2


Publish Year: - Title: Diamond Quality Factors Abstract: Diamond is available in a range of sizes and qualities to fit every consumer's tastes.

	One of the first things most people learn about diamonds is that not all diamonds are created equal. In fact, every diamond is unique. Diamonds come in many sizes, shapes, colors, and with various internal characteristics.

	All polished diamonds are valuable. That value is based on a combination of factors. Rarity is one of those factors. Diamonds with certain qualities are more rare—and more valuable—than diamonds that lack them.

	Jewelry professionals use a systematic way to evaluate and discuss these factors. Otherwise, there would be no way to compare one diamond to another. And there would be no way to evaluate and discuss the qualities of an individual diamond. Diamond professionals use the grading system developed by GIA in the 1950s, which established the use of four important factors to describe and classify diamonds: Clarity, Color, Cut, and Carat Weight.

	Diamonds can be fashioned into a variety of shapes and still be beautiful.

	These are known as the 4Cs. When used together, they describe the quality of a finished diamond. The value of a finished diamond is based on this combination.

	A diamond’s value is often affected by the rarity of one or more of the 4Cs. Colorless diamonds are scarce—most diamonds have tints of yellow or brown. So a colorless diamond rates higher on the color grading scale than a diamond that is light yellow. Value and rarity are related: In this case a colorless diamond is more rare and more valuable than one with a slight yellow color. The same relationship between rarity and value exists for clarity, cut, and carat weight.

	The 4Cs describe the individual qualities of a diamond, and the value of an individual diamond is based on these qualities. The terms that people use to discuss the 4Cs have become part of an international language that jewelry professionals can use to describe and evaluate individual diamonds.

	Today, the descriptions of each of the 4Cs are more precise than those applied to almost any other consumer product. And they have a long history. Three of them—color, clarity, and carat weight—were the basis for the first diamond grading system established in India over 2,000 years ago.

Color

	Subtle differences in color can dramatically affect diamond value. Two diamonds of the same clarity, weight, and cut can differ in value based on color alone. Even the slightest hint of color can make a dramatic difference in value.

	This emerald cut diamond is colorless and is a D color grade. – Courtesy Lazare Kaplan Diamonds

	In the normal color range, the closer a diamond gets to colorless, the higher its per-carat price. There’s an especially large leap in the price of a colorless diamond, which is extremely rare.

	Diamonds come in many colors. Diamonds that range from colorless to light yellow and brown fall within the normal color range. Within that range, colorless diamonds are the most rare, so they’re the most valuable. They set the standard for grading and pricing other diamonds in the normal color range.

	These diamonds—graded E, K, and Z—represent diamond colors near the top, middle, and bottom of the GIA Color Scale. - © GIA & Tino Hammid

	At the GIA Laboratory, diamonds are color graded under controlled conditions by comparing them to round brilliant diamonds of known color, called masterstones.

	To eliminate the guesswork from grading a diamond’s color, graders compare it to masterstones that represent known colors in the GIA D-to-Z scale. - © GIA & Tino Hammid

	The GIA D-to-Z scale is the industry standard for color-grading diamonds. Each letter represents a range of color based on a diamond’s tone and saturation.

	Many diamonds emit a visible light called fluorescence when they’re exposed to ultraviolet (UV) radiation. Although invisible to the human eye, UV radiation is everywhere. Sunlight contains it. Fluorescent lights emit it, too. Under the right conditions, you can see fluorescence in about 35 percent of gem diamonds.

	Blue is the most common fluorescent color in gem-quality diamonds. In rare instances, fluorescence can be white, yellow, orange, or many other colors.

	Strong blue fluorescence can make a light yellow diamond look closer to colorless in sunlight. Blue and yellow are color opposites and tend to cancel each other out, so blue fluorescence masks the yellow color. If the fluorescence is too strong it can make the stone look cloudy or “oily,” which can lower the value of the diamond.

Clarity

	Few things in nature are absolutely perfect. This is as true of diamonds as anything else. Diamonds have internal features, called inclusions, and surface irregularities, called blemishes. Together, they’re called clarity characteristics. Clarity is the relative absence of inclusions and blemishes.

	Among other things, blemishes include scratches and nicks on a diamond’s surface. Inclusions are generally on the inside, and some might break the surface of the stone. Sometimes, tiny diamond or other mineral crystals are trapped inside a diamond when it forms. Depending on where they’re located, they might remain after the stone has been cut and polished, and they can affect a diamond’s appearance.

	Clarity characteristics might have a negative influence on a diamond’s value, but they can have positive effects as well. For one thing, they help gemologists separate diamond from imitations. (This is easier with included diamonds than with flawless ones.) And because no two diamonds have exactly the same inclusions, they can help identify individual stones. They can also provide scientists with valuable information about how diamonds form.

	No two diamonds have exactly the same clarity characteristics in exactly the same locations. This fact helps gemologists identify individual diamonds.

	Like the rest of the 4Cs, clarity’s influence on value is directly related to the concept of rarity. Flawless is the top grade in the GIA Clarity Grading System. Diamonds graded Flawless don’t have visible inclusions or blemishes when examined under 10-power (10X) magnification by a skilled and experienced grader.

	As clarity increases, and if all other value factors are equal, diamond price per carat also increases.

	Flawless diamonds are very rare—so rare, in fact, that it’s possible to spend a lifetime in the jewelry industry without ever seeing one, and they command top prices.

	At the other end of the scale are diamonds with inclusions that can be easily seen by the unaided eye. Between the two extremes are diamonds with inclusions visible only under 10X magnification. Stones in the middle range make up the bulk of the retail market.

	There are 11 clarity grades in the GIA clarity grading system. They are Flawless, Internally Flawless, two categories of Very, Very Slightly Included, two categories of Slightly Included, and three categories of Included.
	The effect of a clarity characteristic on the clarity grade is based on its size, number, position, nature, and color or relief.

	The GIA clarity scale includes eleven diamond clarity grades. The scale narrows at the top because there are very few diamonds in the higher clarity grades.

	Sometimes, one factor makes more difference to the clarity grade than the others. But it’s not always the same one. The relative importance of each factor varies from diamond to diamond. For example, an inclusion off to the side of a stone would have less impact on clarity than the same size inclusion located directly under the table. In this case, the position is probably the determining factor.

	A clarity characteristic's effect on a diamond's clarity grade is determined by five factors: size, number, position, nature, and color or relief. - Gary Roskin GG, FGA

	Occasionally, if an inclusion has the potential to cause damage to a stone, it can affect the grade. But this is rare, and usually applies only to Included (“I”) diamonds.

	Diamond professionals use a set of terms that originally included very very slightly imperfect, very slightly imperfect, slightly imperfect, and imperfect. In recent years, the term imperfect has been replaced with included. (GIA uses included in its clarity grading system.)

	These terms were shortened to the initials VVS, VS, SI, and I. The abbreviations eventually gained acceptance throughout the international diamond community. Their use is now widespread regardless of how the words they stand for translate into various languages. Very may translate to tres in French, for instance, but in France a very slightly included diamond is still a VS. Even a country like Russia, with a completely different alphabet, uses the same abbreviations.

Cut

	A beautifully finished diamond is dazzling, with every facet displaying the craftsman’s skill and care. When a diamond interacts with light, every angle and every facet affects the amount of light returned to the eye. This is what gives it its face-up appearance.

	In efforts to differentiate themselves, and because of increasing demand for precision in cutting, many manufacturers fashioned diamonds to exacting standards throughout the decade. Note the precise arrow pattern in this 1.54 ct diamond.

	A diamond’s proportions determine how light performs when it enters the diamond. If light enters through the crown and goes out through the pavilion, the diamond will look dark and unattractive.  Diamonds with different proportions and good polish make better use of the light, and will be bright, colorful, and scintillating.

	A well-cut diamond displays the beauty consumers expect to see in a diamond.

	A beautiful diamond looks the way it does because of three optical effects: white light reflections called brightness, flashes of color called fire, and areas of light and dark called scintillation. Pattern is the relative size, arrangement, and contrast of bright and dark areas that result from a diamond’s internal and external reflections. There must be enough contrast between the bright and dark areas to give the pattern a crisp, sharp look.

	The diamond industry has long known that some proportion combinations make light perform better than others. In recent years, however, scientists and researchers in GIA’s Research Department and the GIA Laboratory have shown that there are many variations and combinations of proportions that will maximize brilliance and fire in round brilliant cut diamonds.

	As a general rule, the higher the cut grade, the brighter the diamond. Under fluorescent lighting, these diamonds (left to right) display high, moderate, and low brightness.
	The term “cut” also can describe a fashioned diamond’s shape. Shapes other than the standard round brilliant are called fancy cuts. They’re sometimes called fancy shapes or fancies. Fancy shapes also have names of their own, based on their shapes. The best known are the marquise, princess, pear, oval, heart, and emerald cut.

	Fancy-shape diamonds, along with the classic round diamonds, are popular choices for today’s jewelry consumer. Courtesy Lazare Kaplan Diamonds

Carat Weight

	Many goods are sold by weight—by the kilogram, ounce, pound, or ton. Even people who have never bought a diamond are used to the idea that weight and price are related. They understand that a larger diamond is probably more valuable than a smaller one. But there are two things that often surprise people when they start learning about diamonds and carat weight.

	The first is the precision with which diamonds are weighed. Diamond weights are stated in metric carats, abbreviated “ct.” One metric carat is two-tenths (0.2) of a gram—just over seven thousandths (0.007) of an ounce. One ounce contains almost 142 carats. A small paper clip weighs about a carat.

	The metric carat is divided into 100 points. A point is one hundredth of a carat.

	Diamonds are weighed to a thousandth (0.001) of a carat and then rounded to the nearest hundredth, or point. Fractions of a carat can mean price differences of hundreds—even thousands—of dollars, depending on diamond quality.

	Over a carat, diamond weights are usually expressed in carats and decimals. A 1.03-carat stone, for example, would be described as “one point oh three carats,” or “one oh three.” Weights for diamonds that weigh under a carat are usually stated in points. A diamond that weighs 0.83 carat is said to weigh “eighty-three points,” or called an “eighty-three pointer.”

	Large high quality diamonds are rare and valuable gems. This diamond weighs a remarkable 100.20 carats and is internally flawless. - © GIA and Harold & Erica Van Pelt, courtesy The Steinmetz Group

	The relationship between rarity, weight, and value can be surprising. People know that a pound of sugar costs twice as much as a half-pound of sugar. But diamonds aren’t a commodity like sugar. Their price depends on a number of variables—weight is just one of them. So it’s not always easy to understand, or explain, why a 1-carat diamond is worth, say, $6,000, while a 2-carat diamond of similar quality might be worth $15,000.

	It’s really a simple concept: Large diamonds are more rare than small diamonds. The more scarce something is, the more it is worth. So a larger stone doesn’t just cost more. It also costs more per carat. A 1-carat diamond weighs the same as four 0.25-carat diamonds. But even if all the other quality factors are equal, the larger diamond is worth much more than the sum of the four smaller diamonds.

	Carat weight can also be symbolic. While the visual difference between a 0.98-carat diamond and a 1.01-carat diamond is negligible, many people will opt for the larger stone—even at a much higher price. Some weights are considered “magic sizes”: half carat, three-quarter carat, one carat, etc. There’s not much difference in their weights, but if both are D-color round brilliants with identical clarity and cut, the size makes all the difference. They really don’t look much different, but if a consumer’s heart is set on the one-carat size, the difference is enormous. The fact that the second stone is slightly over the “magic” one-carat size can give it as much as a 20 percent difference in price with only a 6-point difference in weight.

	This oval shape diamond weighs 1.01 carats and made the 1.00 carat magic size range. When diamonds reach the so called magic sizes the value per carat increases. – Courtesy Lazare Kaplan Diamonds

	Don’t confuse the term carat with karat. Karat is a unit of measure used to describe how much pure gold there is in an alloy. @topic:10


Publish Year: - Title: Diamond History and Lore Abstract: Diamonds have a long history as beautiful objects of desire. In the first century AD, the Roman naturalist Pliny stated: “Diamond is the most valuable, not only of precious stones, but of all things in this world.”

A diamond has to go through a lot before it reaches the jeweler’s display case. It forms deep in the earth under extreme heat and pressure. It’s ejected violently upward until it arrives at or near the earth’s surface. It’s forced from its hiding place by nature or by man. Then it’s cleaved and cut and polished until its natural beauty shines through.

The world’s love of diamonds had its start in India, where diamonds were gathered from the country’s rivers and streams. Some historians estimate that India was trading in diamonds as early as the fourth century BC. The country’s resources yielded limited quantities for an equally limited market: India’s very wealthy classes. Gradually, though, this changed. Indian diamonds found their way, along with other exotic merchandise, to Western Europe in the caravans that traveled to Venice’s medieval markets. By the 1400s, diamonds were becoming fashionable accessories for Europe’s elite.

In the early 1700s, as India’s diamond supplies began to decline, Brazil emerged as an important source. Diamonds were discovered in the pans of gold miners as they sifted through the gravels of local rivers. Once it reached its full potential, Brazil dominated the diamond market for more than 150 years.

While sources changed, the diamond market experienced its own evolution. The old ruling classes—diamonds’ biggest consumers—were in decline by the late 1700s. Political upheavals like the French Revolution led to changes in the distribution of wealth.

The 1800s brought increasing affluence to western Europe and the United States. Explorers unearthed the first great South African diamond deposits in the late 1800s just as diamond demand broadened.

	By the early 1900s, De Beers controlled about 90 percent of the world’s production of rough diamonds. - Courtesy De Beers
The story of the modern diamond market really begins on the African continent, with the 1866 discovery of diamonds in Kimberley, South Africa. Entrepreneur Cecil Rhodes established De Beers Consolidated Mines Limited 22 years later, in 1888. By 1900, De Beers, through its mines in South Africa, controlled an estimated 90 percent of the world’s production of rough diamonds.

The South African sources affected many segments of the diamond industry. This was especially true as diamond mining moved from the surface to farther underground. Because of the huge costs and comparatively low yields involved, the new sources forced the development of more efficient mining techniques. They created the need for better marketing. They also led to advances in cutting and polishing—advances that increased efficiency, reduced costs, and enhanced the appearance of finished stones.

In the 1870s, annual production of rough diamond was well under a million carats. By the 1920s, the figure was around three million carats. Fifty years later, annual production approached 50 million carats, and in the 1990s it surpassed 100 million carats per year.

At the end of the 1970s, the world’s most important rough diamond producers were South Africa, Zaire (now renamed the Democratic Republic of Congo), and the former Soviet Union. In the 1980s, output of higher-quality diamonds from Russia and South Africa remained relatively constant, but Zaire’s production of lower-quality diamonds more than doubled.

In 1982, a highly productive new mine in Botswana added to world production. A prolific source of high-quality diamonds, the Jwaneng mine boosted Botswana’s production so much that the country rose to third in the world in total diamond recovery, and second in diamond value. De Beers contracted with Botswana’s government to buy the mine’s production and Botswana set out to build its own diamond-cutting industry.

World diamond mining expanded dramatically with the discovery of sources in Australia in 1985 and important new deposits in northern Canada in 2000.

The market probably changed as much after 1990 as it did in the years after the 1866 discovery of diamonds in South Africa and the establishment of De Beers. The 1990s brought exciting new sources and encouraged the dramatic growth of some cutting centers. All this was happening as the world economy fluctuated wildly.

As one of the trade’s major participants, De Beers had to change, too. The De Beers of today bears little resemblance to the De Beers of 1989. The company greatly reduced its role as the custodian of diamond supply. Instead of flowing into the market in a single-channel path from De Beers, diamonds now flow into the market through multiple channels.

Not everything changed, though. Regardless of the path they take, diamonds still flow from mines through cutting centers, and ultimately to retail customers.

Diamond’s splendor has been appreciated for centuries, but there was not much scientific knowledge about it before the twentieth century. Since then, diamond knowledge has grown steadily, with research by chemists, physicists, geologists, mineralogists, and oceanographers. In the past 50 years alone, scientists have learned a lot about how diamonds form and how they’re transported to the earth’s surface. That knowledge has made it easier to predict locations for new diamond discoveries.

	The mystique and prestige of diamonds has made them desired around the world to adorn jewelry and watches. - © GIA & Tino Hammid, courtesy Suzanne Tennenbaum @topic:11


Publish Year: 2013 Title: Diamond with High Concentration of Nickel Abstract: Figure 1. This 2.54 ct Fancy Light greenish yellow diamond showed a high quantity of nickel, believed to be related to its fancy color saturation. Photo by Robison McMurtry.

A 2.54 ct cushion-cut diamond (figure 1) was color graded as Fancy Light greenish yellow. Its UV-Vis-NIR spectrum showed a large absorbance caused by nickel-related defects (figure 2). It is unusual for a diamond to be solely colored by nickel, and more so for the diamond to be graded in the fancy color range. Such diamonds have been previously reported (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 was the first time energy-dispersive X-ray fluorescence (EDXRF) spectroscopy has been run to detect the presence of nickel. As seen on the XRF spectrum (figure 3), the nickel content was high enough to be detected. This is likely related to the diamond’s fancy color saturation.

Figure 2. This UV-Vis-NIR spectrum shows an unusually large absorption band related to nickel defects in diamond.

Figure 3. The greenish yellow diamond’s EDXRF spectrum shows a clear peak at 7.5 keV, a characteristic peak of nickel.
In addition to its unusual color origin, the diamond contained a mineral inclusion with a color-change effect. It appeared purple under the incandescent well light of a gemological microscope and dark blue under the fluorescent overhead light on the same microscope. We suspected the inclusion was a color-change garnet, and this was confirmed using Raman spectroscopy. The stone also contained a small cloud of oriented reflective inclusions associated with type IaA diamonds, consistent with this sample’s diamond type. The diamond showed weak green transmission, which was unusual because it had no defects commonly associated with green transmission (i.e., the H3 feature). Whether the transmission is related to the nickel content is not known. @topic:4


Publish Year: 2015 Title: Red Heart Inclusion in Diamond Abstract: A unique expression of romance: Breaking the surface of this 2.00 ct diamond is a red heart-shaped inclusion. Photomicrograph by Nathan Renfro; field of view 1.58 mm.

	Diamonds, like colored gemstones, contain a variety of interesting inclusions. Although some would call them flaws, I prefer to think of them as Mother Nature’s artwork or fingerprint. I have seen inclusions resembling angels and animals of all sorts, some requiring more imagination than others. It is fascinating to think of what might have been captured inside a diamond more than two billion years ago.

	The 2.00 ct round brilliant diamond shown in figure 2 has I color, I1 clarity, and a wonderful cut. But its most remarkable feature is a red heart-shaped inclusion, identified as pyrope garnet based on microscopic examination by GIA’s Carlsbad laboratory. The inclusion is not visible to the eye but jumps out at 10× magnification. It measures approximately 140 microns across where it is exposed at the table facet. The inclusion is much larger and extends along almost half of the image frame, but the reflective interface makes it difficult to see the underlying garnet. We only see the pink color where the inclusion breaks the surface and the mirror-like interface has been removed.

	With the combination of the red heart and diamond, both universal symbols of love, this is a one-of-a-kind gem. We have named it the Forsythe diamond and plan to auction it around Valentine’s Day 2016, in keeping with the theme of romance, and part of the proceeds will go toward a local charity. How lucky are we to be able to work with beautiful gemstones containing hidden secrets just waiting to be unlocked every day. @topic:10


Publish Year: 2016 Title: Diamond Inclusion with Radiation Halo Abstract: Figure 1. Left: This 0.49 ct Fancy pink brown diamond, measuring 4.11 mm wide, contains a monazite inclusion with a brown radiation halo. Right: A photomicrograph of the monazite inclusion shows the halo thickness of about 10–20 µm. The inclusion’s color is masked by the brown radiation stain, but it appears to be yellow or colorless. The dark feature extending from the bottom of the inclusion is a graphitized crack. Field of view 0.36 mm. Photos by Jian Xin (Jae) Liao (left) and Evan Smith (right).

Radiation is known to impart green or brown coloration to diamond. This effect most commonly appears as colored spots, presumably where radioactive mineral grains settled against the diamond for an extended period. Circulation of radioactive groundwater may contribute to a “skin” with more evenly distributed color. In either case, the radiation comes from an external source. GIA’s New York lab recently examined a 0.49 ct Fancy pink brown diamond containing an inclusion with a brown radiation stain in the form of a halo (figure 1). In this case, the radiation originated from the inclusion itself.

Because the inclusion is completely enclosed within the diamond, the material must have been trapped during diamond growth in the mantle. Raman spectroscopy (figure 2) revealed the inclusion to be monazite, (Ce,La,Nd,Th)PO4, a mineral capable of carrying significant amounts of radioactive thorium. Xenotime, YPO4, a similar rare earth phosphate, has also been reported as an inclusion in diamond with a radiation stain (Fall 2014 Lab Notes, pp. 237–238), but that inclusion was interpreted as epigenetic.

Figure 2. A Raman spectrum of the inclusion with a radiation halo shows a strong peak at 972 cm–1 and smaller peaks at 575 and 415 cm–1, all of which correspond to monazite.
Monazite is very rarely reported as an inclusion in diamond. It is not part of the common mineral assemblage of peridotitic or eclogitic mantle host rocks. Instead, a rare earth element–enriched phosphate like monazite could be attributed to carbonatitic fluid or melt that infiltrated the host rocks and contributed to diamond growth. Monazite found within peridotite mantle xenoliths has also been ascribed to carbonatitic metasomatism (R.L. Rudnick et al., “Carbonatite metasomatism in the northern Tanzanian mantle: Petrographic and geochemical characteristics,” Earth and Planetary Science Letters, Vol. 114, No. 4, 1993, pp. 463–475). Other phosphate minerals, chiefly apatite, can be found as a component of the fluid microinclusions that characterize so-called fibrous diamond. Diamond-forming fluids or melts are believed to be an important source of incompatible elements that may re-enrich the otherwise depleted refractory lithospheric mantle. @topic:10


Publish Year: 2017 Title: Unusual Cloud in Diamond Abstract: The delicate interlinked cross-like cloud pattern found in this 0.62 ct diamond has never been encountered in GIA’s laboratories. Photomicrograph by Nathan Renfro; field of view 2.40 mm.

GIA’s laboratories issue clarity grades for many diamonds for the gem trade. So when we observe a diamond with clarity characteristics we have not encountered before, we generally consider those features to be rather rare and worth documenting for future reference.

Recently, just such a diamond was examined in the Carlsbad lab. It was a 0.62 ct round brilliant with very good polish and symmetry and a very light brown bodycolor. The diamond exhibited a faint light blue fluorescence to long-wave radiation and an inert reaction upon exposure to short-wave UV.

The gem’s I1 clarity grade resulted from a delicate cloud of cruciform dislocations (see above), forming numerous small interlinked cross-like patterns in the diamond host, which were visible face-up through the table facet. The shape and orientation of the overall cloud suggests that the cube face of the original diamond crystal was parallel to the table facet of the faceted diamond.
We regularly encounter cloud clarity features in diamonds, but this fascinating geometric network was a “first encounter” for us. @topic:4


Publish Year: 2017 Title: Diamond with Unusual Fluorescence Distribution Abstract: Figure 1. Left: The 2 ct round (second from right) displayed an unusual fluorescence reaction confined to the culet area. Right: When observed face-up, the small fluorescent area by the culet reflected throughout the stone and appeared more intense. Images by Jian Xin (Jae) Liao.
The New York lab recently encountered a round brilliant diamond, weighing just over 2 ct, that displayed little if any reaction to long-wave UV except for a small spot confined to the area around the culet (figure 1, left). This small area appeared to have medium fluorescence intensity. While the laboratory determination of fluorescence strength and color is performed in the table-down position, we noticed a very different appearance when the diamond was observed through the crown (figure 1, right). Because of the location of the fluorescent area, it reflected evenly throughout the face-up position andappeared to have higher intensity, at approximately the strong/very strong boundary.

DiamondView imaging revealed that the diamond was cut with its growth zonation parallel to the girdle. We speculate that the area of fluorescence in the rough was larger and more centrally located, indicating that the earlier growth showed more blue fluorescence than the later growth, which was basically inert to UV radiation. With the given orientation and placement of the finished stone in the rough, a part of this fluorescent area remained at the culet in the cut stone, leading to this unusual feature.

Absorption spectra in the infrared region confirmed this to be a type Ia diamond with a high concentration of aggregated nitrogen and spectral features typical of a natural diamond. The N3 defect was detected by the presence of moderate-intensity absorption in the UV-Vis absorption spectrum, which is consistent with this type of diamond. The N3 defect is a well-known cause of blue fluorescence in natural diamonds. Based on past experience, it should be pointed out that the area at the culet with medium-strength blue fluorescence does not necessarily have higher concentrations of the N3 defect. The occurrence of other impurities or lattice distortion could affect fluorescence intensity from the N3 defect as well.

The effect of blue fluorescence on the appearance of D-to-Z diamonds has been debated for more than 25 years. GIA conducted a study on this subject in the 1990s (see T.M. Moses et al., “A contribution to understanding the effect of blue fluorescence on the appearance of diamonds,” Winter 1997 G&G, pp. 244–259). The study showed that blue fluorescence had little to no impact on color appearance or transparency except in extremely rare examples of “overblues.” With this in mind, the 2 ct round brilliant offered an interesting opportunity to revisit the earlier experiment’s face-up observations.We compared the diamond, which was graded “H” color, with nonfluorescent diamonds—GIA color master stones—of similar color. As seen in figure 2, no visual difference was observed in the standard color-grading environment. This example supports the conclusion from the 1997 article that the industry would be better served by considering each diamond on its own visual merits.

Figure 2. No visible difference in color appearance or transparency was noted when the fluorescent stone was flanked by nonfluorescent diamonds of similar color in a color-grading environment. Photo by Jian Xin (Jae) Liao. @topic:4


Publish Year: 2019 Title: The Rare Sun Diamond Abstract: The Rare Sun diamond, a 5.24 ct Fancy Dark yellowish brown modified octahedron, has a centrally located, eye-visible inclusion resembling a star and its rays. Photo by Jian Xin (Jae) Liao.

While manufacturers typically seek to minimize or remove inclusions in gem-quality diamonds, a few are specifically cut to highlight these features. Certain hydrogen-rich diamonds can yield fascinating inclusion forms when faceted. One such stone is the 5.24 ct Rare Sun diamond (see above), which GIA’s New York laboratory recently had the opportunity to examine. Framed at the center of this Fancy Dark yellowish brown modified octahedron is an eye-visible cloud inclusion that scatters light to form the image of a star and its shining rays. The inclusion’s orientation gives it an unusually distinct six-fold symmetry, which is very rare. The overall shape of the Rare Sun diamond has been precisely polished so that as light touches various parts of its surface, a different ray beams through. Achieving this effect required extremely precise fashioning—even the slightest error in cutting or polishing would have diminished the effect.
Very few diamonds have the potential to display this star-like pattern, and fewer still ever have this potential recognized and achieved. Diamonds with unusual inclusions, especially inclusions that suggest the shape of other objects, are also prized by gem collectors and seekers of the uncommon. The Rare Sun diamond is a large and noteworthy example and could be considered among those unique diamonds.
This diamond, with its particularly distinctive inclusion scene, also serves as a valuable research material. Gemologists welcome the opportunity to study gems with such unusual features. @topic:4


Publish Year: - Title: Diamond Cut: The Wow Factor Abstract: The round brilliant is the most popular diamond cut. Because of its popularity, assessment of this cut has been the subject of considerable research. Courtesy of Harold & Erica Van Pelt.

Ask anyone what the most important characteristic of their diamond is and they’re likely to say it’s the “Wow” factor. You want your friends and family to stop, stare and admire the stone dancing on your finger or from your ears.

Carat weight, color, clarity, and let’s face it, price, help you decide which diamond you like best, but you might not understand how your diamond’s cut – how its facets and angles are cut and polished − affects its overall appearance – its “Wow” factor.

A beautifully finished (cut) diamond is dazzling; every facet displays the craftsman’s skill and care. When it interacts with light, each facet and angle affects the amount of light returned to the eye. This is what gives a diamond its face-up appearance and what makes it appealing – or not.

That is why for many people, cut is the most important of the 4Cs − the system developed by GIA to describe a diamond’s quality. Those four factors – color, clarity, cut and carat weight  – are the basis of the International Diamond Grading System that GIA created in the early 1950s as the universal standard of diamonds. The GIA Cut Grading System, introduced in 2005 and validated by thousands of observations by retailers, manufacturers and the public who looked at real diamonds and described why they thought certain diamonds were the best looking, can help you understand what to look for in a well-cut diamond.
The Basics
The GIA Cut Grading System applies to the most popular cutting style – the standard round brilliant – and all clarities across the D-to-Z color range. There are five cut grades: Excellent (EX), Very Good (VG), Good (G), Fair (F) and Poor (P).
A diamond with an Excellent cut grade is very bright. It shows an even pattern with good contrast between light and dark areas, so the reflections appear crisp and well-balanced. This tells you that the cutter made the best possible use of the rough.

The Good cut grade diamond isn’t quite as bright – reflections aren’t as sharp and there’s more darkness or dullness in the diamond.

The Poor cut grade diamond has much more prominent dark areas or dullness. Given the choice, most people would pick either of the first two diamonds instead of this stone.

If you look at the photo above, you can see how diamonds with Excellent, Good and Poor cut grades, from left to right, compare to each other.

If all else is equal, an Excellent cut grade pretty much guarantees an extremely attractive diamond. Diamonds in the Very Good and even Good cut grades are also beautiful; they only suffer by comparison with the very best stones.
Words that Describe Diamond Cut
Words like “sparkle,” “fire,” “brightness” and “pattern” are used when talking about a finished diamond’s appearance. You might hear: “Isn’t it beautiful? See how much it sparkles. See how much life this stone has.”

There are optical effects that make a beautiful diamond look the way it does; together, they give the diamond life and determine its visual appeal – especially when you move it. Optical terms include:

Brightness – often called brilliance – is the effect of all the diamond’s internal and external reflections of white light, best observed under diffused lighting. Well-cut diamonds are brighter than poorly fashioned ones, even if they’re of equivalent size, color and clarity. In general, the brighter a diamond is, the higher its grade will be.
Fire results when white light traveling through the diamond is dispersed into its rainbow of spectral colors. Look for red, blue, yellow or orange flashes as you rock and tilt it under store spotlights.
Scintillation is a combination of sparkle and pattern. Sparkle refers to the spots of light that flash when the diamond, you or the light source moves. In an attractive diamond, the reflections should appear even and balanced in size.
Pattern is the relative size, arrangement and contrast of bright and dark areas that result from a diamond’s internal and external reflections. There must be enough contrast between the bright and dark areas to give the pattern a crisp, sharp look, but no distracting dark areas.

Proportions: Everything Works Together
The whole is greater than the sum when it comes to a diamond’s proportions, which are the dimensions and angles of a polished diamond’s facets and how they relate to one another. There is no set “formula” or set of proportions that result in a perfectly cut diamond. All of the numbers you might have heard other people referring to – table size, crown angle, pavilion angle – work together to create the spectacular stone sitting in front of you.

That’s one of the surprising things GIA researchers discovered in the course of the 70,000 observation tests they conducted as they developed the cut grading system. There are a range of proportions that fall within each cut grade, and each specific diamond within that grade may look slightly different in terms of attributes like brightness, fire or pattern. For this reason, a specific stone may be more appealing to one customer than another, even though both may perform equally well.

The GIA system places more emphasis on the overall appearance of the diamond, as opposed to any single set of proportions.

Diamond Cut: What to Look For
Your eye sees those proportions working together – for better or worse – when you look at a diamond face-up. Dark areas in the center, under the table or around the girdle could mean that the shape of the rough forced some compromise. Conversely, bright, even patterns signify a cutter’s attention to detail and precision.

The GIA system downgrades diamonds that carry excess weight in extremely thick girdles, steep crowns or deep pavilions. Diamonds with features that make them vulnerable to damage – like extremely thin “knife-edge” girdles – also tend to receive lower GIA cut grades.

Carefully observe diamonds that have high cut grades. They are often a little different from each other; you may even prefer a diamond with a lower cut grade.

One last tip: A grading report used in conjunction with your own visual observation will confirm what your eye is seeing. But, ultimately, beauty is in the eye of the beholder, so make sure you pick out a diamond that is most appealing to you. @topic:10


Publish Year: - Title: Diamond: Fun Facts Abstract: April’s birthstone. The hardest natural substance on Earth. More than a billion years old.

There’s a wealth of history and knowledge surrounding diamonds. This popular gem is brilliant, glamorous, breathtaking and mysterious. And you’ll add intriguing to the list after you read through these fun facts about diamonds.
Did You Know?

Diamonds were used to engrave gemstones in India by 300 BCE.
Diamonds can be burned. To burn a diamond, it must be heated to between 1290-1650 degrees Fahrenheit. House fires and jewelers’ torches can sometimes reach that temperature.
D-to-Z color diamonds are the most widely used in jewelry, but diamonds come in all colors of the rainbow. For natural colored diamonds, blue, green, orange and red are the rarest; yellow and brown are the most common.
Diamond weight is measured in carats (not carrots or karats). The word carat is derived from keration, the Greek name for the carob tree whose seed was used for centuries as the standard of weighing precious stones. Because the seed could vary slightly in weight, in 1913, carat weight became metric; one metric carat is equivalent to 0.2 grams or 0.007 ounces.
The largest rough diamond, discovered in 1905, is the Cullinan diamond, weighing in at 3,106 carats (ct.)!

Courtesy of Alan Bronstein and Aurora Gems. Photo: Robert Weldon/GIA
Where do diamonds come from?

Diamonds were formed billions of years ago through a combination of tremendous pressure and temperatures of 1652–2372 degrees Fahrenheit at depths between 90 and 120 miles beneath Earth’s surface.
Diamond crystals are brought closer to the Earth’s surface through volcanic activity.
Diamonds can be found in shallow alluvial deposits where the crystals settle after being transported away from the kimberlite pipes by geologic activity and rivers.
Around 30 percent of the diamonds mined worldwide are gem-quality.
Prior to the 18th century, most diamonds were found in India.
Diamonds were discovered in South America as early as 1725. The discovery occurred in Minas Gerais, Brazil, just as the production in India was dwindling.
Diamonds were found in North America in the 1840s, although this was soon eclipsed by the discovery of diamonds in Africa in the late 1860s and early 1870s and the ensuing Great Diamond Rush.
In 2014, Russia produced the most diamonds by volume and value.
With the opening of the Ekati mine in late 1988, and others in Canada, North America produces almost 10 percent of the total world diamond production by volume.
Even though the U.S. produces almost no diamonds for commercial consumption, America buys more than 40 percent of the world’s gem quality diamonds – making it the world’s largest diamond market.

Now that you know some fun facts about diamonds and where they come from, take a look at some of the most famous diamonds ever found.
The Hope Diamond

Courtesy of Chip Clark, Smithsonian Institution. http://geogallery.si.edu/

The Hope diamond, a Fancy dark grayish blue diamond, fashioned into a cushion brilliant cut, was originally 112 ct. before being cut to its present weight of 45.52 ct.
The Hope diamond is said to be cursed. Although one of its owners, Evalyn McLean believed it to be her good luck charm, her life states otherwise; after possession of the gem, her young son died in a car accident, her husband divorced her and died insane, and her daughter committed suicide.
The Hope diamond, perhaps the world’s most legendary gem, arrived at its present home at the Smithsonian Institution on Nov. 10, 1958 via the U.S. mail – albeit registered first class!

The Uncle Sam Diamond

To date the Uncle Sam, discovered in 1924, is the largest diamond ever found in the U.S.
It was found in the world’s only diamond mine open to the public. The Crater of Diamonds State Park in Arkansas is a dig-for-fee operation for tourists and rock hounds.
Since 1906, more than 70,000 diamonds have been discovered there, including the Uncle Sam diamond, weighing 40.23 ct.

In 2015, a park visitor found an 8.52 ct. diamond at the same park the diamond was discovered.
The Cullinan Diamond

Photo by Peter Macdiarmid/Getty Images

The historic Cullinan diamond, found in South Africa in 1905, weighed an astounding 3,106 ct. It was cut into a total of 105 diamonds of exceptional color and clarity.
The Great Star of Africa (Cullinan I) weighs 530.20 ct. and the Lesser Star of Africa (Cullinan II) weighs 317.40 ct. These two diamonds are part of the crown jewels of Great Britain.
Cullinan III through Cullinan IX, and the remaining 96 diamonds cut from the Cullinan are in private collections.
The two largest stones are mounted in the British crown jewels, while eight others are part of Queen Elizabeth II’s private collection.

The Wittelsbach-Graff Diamond

Photo by Robert Weldon/GIA

The 31.06 ct. Wittelsbach-Graff is one of the largest historic blue diamonds ever fashioned.
Blue diamonds are extremely rare. The presence of boron impurities is often responsible for the color of natural blue diamonds. However, their color can also be caused by radiation exposure or associated with hydrogen. Blue diamonds naturally colored by exposure to radiation are usually described as green-blue, whereas those with color that is associated with hydrogen are described as gray-violet to gray-blue.
The diamond belonged to the Bavarian House of Wittelsbach and was displayed in the Treasury of the Munich Residence until it disappeared in 1931. It was secretly sold in 1951, "rediscovered" in 1961, and then sold again in 1964 to an undisclosed private buyer.
In December 2008, the Wittelsbach-Graff (then called the Wittelsbach Blue) was sold at Christie’s London to jeweler Laurence Graff for just over $24.3 million.
The stone is graded Fancy Deep blue with IF clarity.
Because the Wittelsbach-Graff Diamond and the Hope diamond have similar color and long-lasting phosphorescence – and both are believed to have been mined in India– there has been widespread speculation that they were cut from the same crystal. But were they? Research published in the Summer 2010 issue of Gems & Gemology indicates that the two diamonds do not share a common parent.

Want to learn more? Check out diamond in the GIA Gem Encyclopedia to read more about the history, lore and scientific research surrounding this beloved gemstone. @topic:10