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  • Thread: Coated Tanzanite Warning! (9 Posts)
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    Default Coated Tanzanite Warning!

    AGTA GTC and AGL IDENTIFY COATED TANZANITE.
    NEW YORK, NY - 23 May 2008 -


    Recently the American Gem Trade Association Gemological Testing Center (AGTA GTC) and American Gemological Laboratories (AGL) received a number of faceted tanzanite samples that were determined to be coated. Evan Caplan of Omi Gems, Inc. sent samples to several labs after a light repolishing of a few stones resulted in a noticeable loss of color.

    "Until now, we had not identified a coating on tanzanite to improve its color." indicated Dr. Lore Kiefert, Director of the AGTA GTC.

    "Although the coating is not immediately obvious, careful examination with a microscope and in immersion provided clear indications of the coating in most instances." stated Christopher P. Smith, Vice President and Chief Gemologist of AGL. "This was evidenced by abrasions along facet junctions and at the culet where the coating had worn off, as well as a subtle iridescence when viewing the surface with reflected light." Smith further added.

    Advanced analytical testing identified that the coating was composed at least in part to cobalt. "The most reliable means to substantiate the presence of the coating is with the use of X-ray fluorescence spectroscopy." Kiefert explained "The coating is colored by cobalt, which is readily detected using this analytical technique."

    Although the gemstone industry has become very familiar with the practice of heating zoisite to achieve the best violet to blue color in tanzanite, these stones represent the first time either lab has identified a coating on tanzanite to further improve its color.

    The majority of the tanzanite sample was comprised of smaller calibrated stones. Fine color tanzanite in this size range is rarely sent to a lab and therefore would avoid detection unless closely scrutinized. "This is just a further reminder that each and every gemstone should be fully examined to determine whether or not it has been treated." Smith indicated "Today, it is not uncommon to see stones that have been treated using multiple or compound techniques to achieve a particular result."

    As a closing statement, both Kiefert and Smith emphasized "Any treatment used to modify the color of a gem should be disclosed. Coatings in particular are not considered permanent and in the U.S. are required by FTC guidelines to be properly disclosed at the point of sale."

    Figure 1: These two tanzanites were part of a group of stones recently examined at both the AGTA GTC and AGL facilities in New York. Both were identified as having a thin coating layer to artificially improve their color. Photograph by Fred Kahn and Sun Joo Chung.

    Figure 2: The cobalt-coating produced a subtle iridescence that could be seen when observing the stone's surface in reflected light. The rectangular area near the point of this facet also highlights an area on the host tanzanite where the coating did not adhere. Photomicrograph by Christopher P. Smith

    Figure 3: In immersion it was also noted that along facet junctions and at the culet the color was lighter. This was a result of where the coating had been abraded away, revealing the lighter, inherent color of the tanzanite. Photomicrograph by Christopher P. Smith

    # # #
    About American Gem Trade Association-Gemological Testing Center
    The American Gem Trade Association is a not-for-profit Association serving the natural colored gemstone and cultured pearl industry since 1981. The AGTA serves the industry as The Authority in Color™ and has its headquarters office in Dallas, Texas and the world-renowned Gemological Testing Center in New York, New York (www.agta-gtc.org).
    About American Gemological Laboratories

    Founded in 1977 by C. R. "Cap" Beesley, American Gemological Laboratories (AGL), a subsidiary of the publicly traded Collector’s Universe (NASDAQ: CLCT), pioneered the development of the world’s first comprehensive Colored Stone Grading System (www.aglgemlab.com) AGL has also provided detailed country of origin and enhancement reports for some of the most prestigious retailers and auction houses in the world for the past three decades. In 2007, AGL was the designated official North American laboratory of the International Colored Gemstone Association (ICA). In addition, the laboratory is the official colored gemstone laboratory of the 2007 Fine Jewelry CEO Summit and the JCK Las Vegas Shows, as well as the 2007 Platinum Sponsor of the ICA World Congress in Dubai.
    -----------------------------------
    -- JCK-Jewelers Circular Keystone, 5/26/2008 1:18:00 PM

    Recently the American Gem Trade Association Gemological Testing Center and American Gemological Laboratories received a number of faceted tanzanite samples that were determined to have been coated.

    Evan Caplan of Omi Gems, Inc. sent samples to several labs after a light repolishing of a few stones resulted in a noticeable loss of color.

    “Until now, we had not identified a coating on tanzanite to improve its color.” said Lore Kiefert, Director of the AGTA-GTC.

    “Although the coating is not immediately obvious, careful examination with a microscope and in immersion provided clear indications of the coating in most instances.” stated Christopher P. Smith, Vice President and Chief Gemologist of AGL “This was evidenced by abrasions along facet junctions and at the culet where the coating had worn off, as well as a subtle iridescence when viewing the surface with reflected light.” Smith further added.

    Advanced analytical testing identified that the coating contained cobalt. “The most reliable means to substantiate the presence of the coating is the use of X-ray fluorescence spectroscopy.” Kiefert explained “The coating is colored by cobalt, which is readily detected using this analytical technique.”

    Although the gemstone industry has become very familiar with the practice of heating zoisite to achieve the best violet to blue color in tanzanite, these stones represent the first time either lab has identified a color-enhancing coating on tanzanite.

    The majority of the tanzanite sample was comprised of smaller calibrated stones. Fine color tanzanite in this size range is rarely sent to a lab and therefore would avoid detection unless closely scrutinized.

    “This is just another reminder that each and every gemstone should be fully examined to determine whether or not it has been treated.” Smith said. “Today, it is not uncommon to see stones that have been treated using multiple or compound techniques to achieve a particular result.”

    As a closing statement, both Kiefert and Smith emphasized “Any treatment used to modify the color of a gem should be disclosed. Coatings in particular are not considered permanent and in the U.S. are required by FTC guidelines to be properly disclosed at the point of sale.”

  2. #2
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    hi, I have checked with some Tanzanite dealers here in Thailand, and they have no knowledge of any coating treatments, so I don't think it is being done here!....however , I am hearing some whispers of a new diffusion treatment being used on pale coloured Tanzanite, will let you know when I find out more details.

    cheers Jeff.

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    Default Supplies not quite so low...

    Retailers get the scoop on tanzanite
    June 02, 2008

    By By Teresa Novellino

    Las Vegas—From a new, universal grading system for tanzanite to concerns that the gem's rarity is being described incorrectly on cruise ship presentations, retailers were able to find out the latest on the blue-violet gemstone and ask questions at a Tanzanite Foundation seminar, held on Sunday at the JCK Las Vegas show.

    The goal of the seminar was to introduce retailers to the Tanzanite Quality Scale, which is used in tanzanite grading reports by the American Gem Trade Association Gemological Testing Center (AGTA-GTC). The scale, an internationally recognized tanzanite-specific grading system, was launched in North America in March 2007 and in Hong Kong in September 2007.

    The system uses the Four C's criteria of carat weight, color, clarity and cut, and also includes a fifth C for confidence. Retailers in the audience said they liked the color scale, but several were interested in getting a larger version that would allow them to better present the different color gradations to customers since the richer hues of the gem command higher prices.

    The foundation is also hoping by the end of the year to offer color-grading software especially for tanzanite through the company GemeWizard, which provides the software for colored-gemstone dealers.

    After the presentation, however, other questions arose. Several audience members were concerned that tanzanite was being misrepresented by promotions on cruise ships, where several retailers in the audience said that consumers were being told that supplies of the stone would run out in a year or two. This is contrary to the Tanzanite Foundation's own research, which indicates that supply of the stone should last 10 to 20 years.

    "We give them the marketing materials, but we have no control over what they say," the Tanzanite Foundation's Hayley Henning said after the presentation.

    She said that Tanzanite International, one of the company's sightholders, has "port lecturers" who promote a variety of products on cruise ships, and that the organization would get in touch with the sightholder to make sure that these lecturers were describing the stones' supply levels accurately.

    Retailers were also updated on the coated tanzanite treatment that was recently detected in a batch of smaller stones received by the AGTA-GTC and American Gemological Laboratories (AGL). The treatment is difficult to detect, though lab officials from both labs said they were able to do so.

    AGL Vice President and Gemologist Christopher Smith said the coating can be detected by using a microscope and immersion techniques, which reveal abrasions along facet junctions and at the culet where the coating has worn off.

    Tanzanite Foundation officials said retailers should be leery of small, vividly colored tanzanite stones selling at cheaper prices

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    Un-True Blue: Cobalt-Treated Tanzanite Is Here
    By David Federman, Editor-in-Chief, Colored Stone

    For years, jewelers have complained about the paleness of tanzanite in calibrated sizes. Now there’s an avalanche of deep sapphire-blue material. Alas, it’s color-coated.
    These two tanzanites were part of a group of stones recently examined at both the AGTA-GTC and AGL facilities in New York. Photo by Fred Kahn and Sun Joo Chung.

    There is a positive spin to the bombshell news that tanzanite is now being widely colored-augmented using cobalt coatings -- and Hayley Henning, a publicist for the Tanzanite Foundation isn’t wasting any time finding it. “The use of this treatment,” she says, “only proves how important tanzanite has become.”

    She’s right, of course. Just as pork now has the reputation of being “the other white meat” tanzanite now has the reputation of being “the other blue stone” -- the original being sapphire. Indeed, this color-coating technique was first used on corundum back in the 1980s.

    This fact puts a second positive spin on the news. The treatment was discovered by two major New York City gem labs -- the American Trade Association’s Gemological Testing Center (AGTA-GTC) and American Gemological Laboratories (AGL) -- working jointly in a very impressive display of gem crisis management.

    According to Christopher P. Smith, AGL’s vice president and chief gemologist, the synergy of both labs working together helped them identify the treatment in a matter of days. “The discovery of cobalt-coated tanzanite is a momentous one,” he says. How so, we asked. “It means labs can no longer take any gemstone for granted. Every gem of commercial importance is a candidate for coating.”

    This is where the spin turns less positive, even ugly. The gemological Blue Meanies have attacked a sector of the market long thought immune to such an invasion. But this time the Meanies are sucking color from the market by adding, not subtracting, it. And their attack raises issues that are both morally and technologically momentous.
    “Hey, good lookin’, what’cha got cookin?”

    The cobalt coating of the tanzanite produced an iridescence that can be seen when observing the stone’s surface in reflected light. The rectangular area near the point of this facet also highlights an area on the tanzanite where the coating did not adhere. Photomicrograph by Christopher P. Smith.
    From a treater’s perspective, cobalt-coated tanzanite is a perfect solution to a problem that has long plagued the tanzanite market: the nagging scarcity of deep-blue tanzanite in smaller sizes. This zoisite usually needs body mass for classy color. But with tanzanite a very popular gem in small calibrated sizes, the market must make do with pale stones -- unless it is willing to accept color coatings.

    So far, it has rejected this option with fine gems. But the popularity of coated topaz may have begun to lessen its resistance to gems with electrifying skin-deep beauty.

    True, coated topaz colors are exotic and fantastic, even hallucinatory, and in no way resemble the colors of natural topaz. The color of cobalt-coated tanzanite, on the other hand, is not extreme in any way -- just too good to be true. Nevertheless, it gives stones an appearance they might have if natural. Indeed, the New York dealer who first became suspicious of color doctoring had bought parcels of calibrated tanzanite which he was assured were natural except for the customary heating which turns zoisite from brown to blue.

    According to a joint AGTA-AGL press release announcing the discovery of cobalt-blued zoisite, the dealer was tipped off to possible coating when he had to repolish a stone and noticed an area of color drop-out. Study of this and other suspect stones under a microscope and in immersion revealed tell-tale signs of coating such as abrasion along facet junctions and culets. Use of X-ray fluorescence, notes Dr. Lore Kiefert, director of the AGTA-GTC, “substantiated the presence of the coating.”
    In immersion, it was noted that the color of the tanzanite was lighter along facet junctions and at the culet. This was a result of the coating having been abraded away, revealing the lighter, inherent color of the tanzanite. Photomicrography by Christopher P. Smith.

    Pause here to consider the implications of these findings. As the recent scandals in the feldspar market surrounding Asian-origin sunstone make clear, traditional heating is no longer the sole gateway method by which gems in need of color enhancement are prepared for the marketplace. Sophisticated face-lift methods involving diffusion of chemical coloring agents are now as much a pillar of gemstone processing as older, far tamer heat-only methods.

    Where does this continuum of high-tech colorization methods lead? How are stones beautified by these methods classified and sold? If surface colorizing using non-intrinsic chemical elements is now a mainstay of gemstone preparation, isn’t it time to develop new categories for this merchandise? Is it enough to say such stones have been color-enhanced?

    One thing’s for sure; it is the ultimate sign of tanzanite’s coming of age that this beautiful one-source East African gem may finally force the jewelry industry to publicly question its excessive reliance on cosmetic beauty in a way that sapphire has yet to do.

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    From GIA Research: Large Coated Tanzanites Lack Typical Identifying Features



    The following report on a new treatment for tanzanite was provided by Shane F. McClure, director of the GIA Laboratory's West Coast Identification Services.

    The coating of gemstones to improve their color has been known for thousands of years, although the typical nonpermanence of the treatment has made it impractical at best and fraudulent at worst. Last year, GIA researchers reported on the emergence of a new generation of coatings -- created using technology from other industries -- that are much more durable than those studied previously (A. H. Shen et al., "Serenity Coated Colored Diamonds: Detection and Durability," Spring 2007 Gems & Gemology, pp. 16-34). That report described colored coatings on diamonds by Serenity Technologies, although we are aware of other companies that are using a similar treatment on diamonds.

    During our investigation of these new coating operations in 2006, we also examined some tanzanite that purportedly had been coated to enhance its durability. Based on the samples we examined at that time, the durability problems and ineffectiveness of the coating did not distinguish this technique from most of the coating techniques reported in the past.

    In April of this year, however, a Los Angeles colored stone dealer contacted us about a parcel of tanzanite his company had just received from New York. Evan Caplan of Omi Gems said the color did not look right, and when the company had one stone repolished it became significantly lighter. This sounded like a coating, so we asked Mr. Caplan if we could examine some of the stones. Initially, Omni Gems loaned GIA two 3-plus ct emerald cuts (figure 1) and four smaller (4-5 millimeter) rounds. Examination of the emerald cuts at about 10× magnification did not reveal any obvious coating characteristics. Coatings are usually visible in reflected light or by looking through the table of the stone toward the pavilion in transmitted light. The features we typically look for -- iridescence in transmitted light, or gaps or worn-off areas in the coating -- were not immediately evident. In fact, polishing lines were plainly visible on most of the facets.

    On closer inspection at higher magnification, however, we observed a number of clues. With reflected light, we saw tiny holes in the coating. These holes seemed relatively sharp-edged, and the coating appeared thicker than we typically see in such material (figure 2). Fiber-optic illumination revealed whitish marks on the surface that looked like dirt but did not wipe off. We also saw several orangy iridescent lines that crossed facet junctions, which were similar in appearance to lines that might be left by a liquid drying on the surface. In addition, there were tiny bright pink to orange flashes of light that turned out to be related to minute areas of damage on the coating.

    At our request, Omi Gems sent us 18 more samples, 4-5 millimeter rounds. Each had a depth of color that would be very unusual for tanzanites this small. In addition, when examined with magnification and reflected light, all the stones showed some characteristics that would be associated with a coating: a pale iridescence on the surface, as well as wear at facet junctions or on the culet that is typical of the "paper wear" often present on gems that are stored together in stone papers (figure 3). The worn facet junctions were readily apparent with immersion in water, since they appeared lighter in color than the rest of the stone. All the features observed in the smaller stones are consistent with those reported by the American Gem Trade Association Gemological Testing Center and American Gemological Laboratories in their joint May 23 press release on this new treatment.

    Energy-dispersive X-ray fluorescence analysis of several samples showed cobalt as a major constituent of the coatings. This chemistry is consistent with the coatings on tanzanite we examined in 2006. In all 20 samples tested, significant amounts of cobalt were found only on the pavilion facets, not on the crown.

    To summarize, it is important to emphasize that these coated tanzanites were sold on the market in New York undisclosed. The smaller stones were immediately suspect because it is very uncommon for tanzanites in these sizes to show such saturated color. All exhibited abrasion on facet junctions or the culet, probably from paper wear, which makes the coating easier to detect. Larger stones that are stored individually, however, may not show these features, and some do not show iridescence in reflected light. Detecting these stones requires careful observation.

    More details on the identification of this coated tanzanite are provided in an article that has been submitted for possible inclusion in a future issue of Gems & Gemology.

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    Luke, just an update, this stuff has now emerged on the Thai markets, and in big sizes!! , it is quite easy to spot, as the colour does not look right, also the girdles are traditional step cut(helps to darken the colour), as opposed to the Portugese cut usually used on Tanzanite.....I would advise anyone purchasing good colour Tanzanite to get them tested by a reputable lab. .... before parting with any cash!

    Jeff.
    Motherearth - Fine Jewelry and Gemstones
    http://www.bidorbuy.co.za/jsp/userpr..._UserId=480951

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    Default tanzanite

    ok ,i bought 2 tanzanites from china - yeh i know big mistake hey! anyway they came back at 176 on th refraction meter- saying it was some sort of sapphire, any ideas what else it can be ??
    these were 6.58 carat stones showing a great dark blue voilet color.
    still trying to work out if its tanzanite,sapphire or something else, any help would be great
    has anyone got any comments regarding the tanzanite the chinese are selling and what it is?
    thanksi new here as i live in australia but enjoy your forum greatly and find a large amount of knowledge here

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    Probably synthetic corundum (sapphire).
    Synthetic Forsterite is the most effective Tanzanite simulant.

  9. #9
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    hi, just an update on Luke's original post! .... there is a huge amount of coated Tanzanite on the Asian markets!! ..... it is not easy to spot the treatment, but there are some giveaway signs! for those in the know!

    Any investment sized pieces should be checked by the EGL !!, do not take the word of a local Jeweler! or some fictitious GIA gemologist advertised by some sellers

    Jeff.
    Motherearth - Fine Jewelry and Gemstones
    http://www.bidorbuy.co.za/jsp/userpr..._UserId=480951

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