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Synthetic Blue Diamonds Hit the Market
Jul 16, 1999 3:47 PM
By Christopher P. Smith and George Bosshart
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Christopher P. Smith and George Bosshart
Since the advent of synthetic diamonds in both Sweden and the U.S. during the 1950’s, our industry has expressed concern over the eventuality of synthetic diamonds becoming commercially available. These concerns were intensified when single crystal synthetic diamonds of gem-quality, sufficient for use in jewelry, became achievable beginning with General Electric in 1970, then by DeBeers later in the 1970’s and in particular during the past fifteen years with Sumitomo in Japan, as well as a number of research facilities in the former Soviet Union.
However, over the course of the past four decades the use of synthetic diamonds has been almost solely directed towards industrial or high-tech applications. The first to attempt the sale and distribution of gem-quality synthetic diamonds for the gemstone and jewelry trade, in 1992, were Tairus (a Thai and Russian joint-venture) and Chatham Created Gemstones (famous for their synthetic emerald, ruby and sapphire), who had contracted with the Russian Academy of Sciences, research facility. While Tairus has achieved moderate success with its primarily type Ib deep yellow to brownish-orange synthetic diamonds (these diamonds may also be annealed to a type IaA), Chatham Created Crystals has experienced continued difficulties bringing the colorless to near-colorless version of synthetic diamonds to the market.
The most recent entrant to this field is Ultimate Created Diamond Co. (UCD), in Golden, Colorado. Towards the end of 1995, it started marketing its synthetic diamonds to the gemstone and jewelry trade. In the beginning, it also dealt primarily with type Ib deep yellow to brownish-orange colored synthetic diamonds, however, during the Tucson Gem and Mineral Show in February of this year, it showcased its commercial production of gem-quality, type IIb synthetic blue diamonds. UCD had begun experimenting in 1998 with the growth of single crystal synthetic type IIb diamonds, containing boron as the color causing impurity. At this year’s Tucson show in February, it proudly displayed more than 60 faceted gemstones ranging in size from 0.03 to 0.45 carats, as well as numerous crystals.
The largest crystal it has grown to date has been slightly larger than 1 carat, whereas the largest faceted gemstone was 0.62 carats. Alex Grizenko, president of UCD, has indicated that its crystal growth is accomplished by thermal gradient method called the TOROID method. This is a high-cost method that is different from the "belt" apparatus utilized by De Beers for its synthetic diamond production or that of the "BARS" split-sphere method, employed by Sumitomo and various other research facilities in the former Soviet Union. Tiny seed crystals are typically used to instigate the growth process, however, Grizenko also indicated that occasionally, their scientists find small crystals which grew by spontaneous nucleation, when they open the vessel after a run has been completed.
Following is a brief description of the various inclusions and gemological properties observed in the type IIb synthetic blue diamonds examined by the Gübelin Gem Lab so far, providing the trade with initial information and the means to identifying them. A more complete study will be forthcoming in the gemological literature.
Gemological Properties of Commercially Available
Synthetic Type IIb Blue Diamonds
Color Appearance
Since these synthetic diamonds owe their color to the same chemical impurity as natural type IIb blue diamonds (i.e. boron), visually they have the same color appearance as their natural counterpart. Therefore, it will be probably best understood if the color terms familiar to the trade are applied to describe these synthetics.
All of the rough and faceted samples examined by the authors ranged in color from fancy light blue to fancy deep blue, while the majority of the faceted samples displayed a very attractive, strong fancy blue to a rich fancy deep blue face-up color appearance (Figure 1). Also as with natural blue diamonds, a small number of the gemstones revealed a slightly grayish modifier.
Inclusion Features
The most frequently observed inclusion features consisted of metallic remnants of the flux catalyst utilized within the growth vessel. Readily visible with a standard loupe or microscope, these opaque inclusions appear black or gray and reveal a high metallic luster when light reflects off of them. They most frequently occur as thick tablets, which are oriented along growth zones (Figure 2A and B), or angular, more equidimensional bodies (Figure 3).
Another, less distinctive inclusion feature that was regularly seen consisted of randomly scattered clouds, composed of pinpoint particles (Figure 4). Fracture planes, or feathers, were also observed, however, they revealed no unique or distinctive appearances (Figure 5).
Color Zoning and Internal Growth Zoning
Weak to prominent sectorial color zoning was present, sharply bordered along growth zones (Figure 6). Straight internal growth planes (grain lines) were observed, however, they did not form "cross" or "hour-glass" patterns as have been noted in other synthetic diamonds.
Strain Patterns
Very weak to weak low-order strain was noted when the stones were observed between crossed polaroid filters. No distinct patterns were noted, besides weak localized strain surrounding the included metallic remnants.
Fluorescence and Phosphorescence
Upon exposure to short-wave UV lamp (254 nm), a chalky yellow reaction of moderate intensity was observed (Figure 7). A strong, long-lasting chalky yellow phosphorescence was also noted upon exposure to SWUV (>90 sec.). No fluorescence or phosphorescence is observed with exposure to long-wave UV lamp (365 nm).
Electrical Conductivity and Magnetism
Since these synthetics are type IIb, colored by boron, they are electrically conductive. In addition, as a result of the metallic inclusions that were present within the gemstones, all of them were magnetic. The strength of the attraction to the magnet was directly related to the number and size of the inclusions within the stones.
UV-Vis-NIR Spectrometry
No distinct bands or lines were observed in the spectrum between 200 and 1400 nm. There was only an increase in the general absorption, as it progresses towards the near-infrared region of the spectrum.
Infrared Spectrometry
The synthetic blue diamonds described herein were identified as type IIb by their mid-infrared spectra. A series of superimposed absorption bands at approximately 1050, 1145, 1195, 1290 and 1332 cm-1 are attributed to lattice vibrations induced by boron impurities and single absorption bands at approximately 2455, 2802 and 2928 cm-1 are attributed to the transfer of electrons within the diamond’s structure, between the carbon and boron atoms.
How to Separate the New Commerically Available Synthetic Type IIb
Diamonds from Natural Blue Diamonds
With careful observation, it is possible for the trade (diamond dealers and jewelers alike) to identify the synthetic origin of these diamonds and thereby to separate them from their natural counterparts. First, the metallic remnants are readily recognized with a standard loupe or microscope. However, the cloud-like inclusion patterns of pinpoint particles may be misleading as they may appear similar to clouds in a natural diamond. There were no noteworthy differences observed in the fracture planes of these synthetic blue diamonds, as compared to natural blue diamonds.
An inspection of the face-up color, by eye (as most in the trade observe diamond colors), offers no indications even to the knowledgeable observer. However with magnification, the sharply bordered color zoning visible within the synthetic diamonds is in contrast to the generally evenly colored natural blue diamonds. Natural blue diamonds may also reveal internal color zoning, but this typically occurs with the color diffusing out as it transitions to the near-colorless or less colored areas.
Natural blue diamonds also typically reveal "silvery" internal graining and Tatami-like (cross-hatch) strain patterns, whereas none of the synthetic blue diamonds examined so far from UCD possessed either of these characteristics.
Another means to readily identify these synthetic blue diamonds, includes observing their distinctive chalky yellow short-wave UV fluorescence and long lasting phosphorescence. Natural type IIb blue diamonds are generally inert to both long-wave and short-wave UV light, although a few may reveal a red to orange-red UV reaction. On rare occasions a natural blue diamond may reveal a yellow fluorescence and phosphorescence to SW-UV, however, the phosphorescent reaction typically reduces rapidly and is very short lived.
Synthetic diamonds alone will be drawn to a magnet, however, both the natural and synthetic type IIb blue diamonds are electrically conductive (i.e. semi-conductors).
To date, no differences have been noted in the UV-Vis-NIR and infrared spectra of natural and UCD synthetic blue diamonds, although this will require additional investigation to conclude further.
Concluding Remarks
Diamonds of a distinct blue hue, are among the rarest and most sought after fancy color diamonds. When they turn up in the trade, or are offered for sale in one of the major auction houses, they never fail to generate great excitement and high per carat prices. The biggest problem which diamond dealers express relating to these rarities, is the difficulty of finding enough good quality material to fill the ever increasing demand.
As of today, the trade may have another concern to contend with. During the first half of 1999, the commercial availability of highly attractive, synthetic type IIb blue diamonds, in smaller sizes, has become a reality which the trade must face. Spurred on by the growing interest and demand for colored diamonds, in particular those with a noticeable blue color, Ultimate Created Diamond Co. of Golden, Colorado, has begun marketing its production of synthetic type IIb diamonds. Alex Grizenko, president of UCD, has indicated that his firm shall increase its current production to approximately 200 carats per month, by the end of this year.
Although the UCD synthetic blue diamonds are visually identical to natural type IIb blue diamonds, they may be separated by the careful observation with a loupe or microscope, of inclusion features, color zoning characteristics, as well as graining and strain patterns, which are different between the two. Additionally, the fluorescent and phosphorescent reactions to UV light also provide a ready means to separate the two (in particular the short-wave ultraviolet light reactions). A more detailed gemological description of these synthetic diamonds will be forthcoming, once additional research into the gemstones has been completed.
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Tags:
De Beers, Japan, Jewelry, Production
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