a publication of the International School of Gemology 25.January.2013

Color Infusion of Tourmaline

The latest images along with independent LA-ICP-MS testing

Over the past five years we have watched the developments surrounding the artificial color infusion of gemstones. The work of Ted Themelis has shown that gemstones of all types can be color infused with various materials under a variety of conditions, including far lower heat than was previously imagined as demonstrated by the Tibet andesine fiasco. During this time we have noticed certain indicators in gemstones treated with a color infusion process, such as the strange color zoning as seen in the tourmaline at left. This image from 2008 demonstrates color zoning that does not follow any particular pattern of crystal growth, but rather follows the pattern of surface reaching fissures and tubes.
We recently obtained additional specimens as seen in the banner image at the top of this report. These specimens, on their own merit, provide strong evidence that something artificial has been done to these tourmaline. For instance....
The blue faceted specimen offers us a color that is based on a blue filler material down tubes that has permeated out into the gemstone. In the image at left it is easy to see that the tubes which were blocked and did not allow the coloring material to enter left colorless tubes as the result. We reported on this in 2010 with other blue tourmalines that also showed this same color zoning based on blocked growth tubes rather than true crystal color.

Sold to us from a Thai dealer as natural watermelon tourmaline, the banner item second from left shows the same blocked tube color pattern, only this time in pink, as the blue specimen above. Below is another look at this specimen in a larger image, showing that the coloring is a result of infusion down the growth tubes rather than natural tourmaline color.

Images are taken through our Meiji Techno using a tap water Dixie® cup immersion cell.

The tourmaline slice specimen at the far left of the banner also provides graphic evidence that the color is due to some type of artificial infusion rather than natural color by this 90x image below that shows the growth tubes filled with the coloring material.

Based on our original findings, the ISG commissioned the Evans Analytical Group Labs to perform LA-ICP-MS elemental testing to ascertain if trace elements in a specimen study group could be identified. The findings were profound.

In 2008 we found an unusual green tourmaline specimen with an extremely enlarged growth tube that was full of a very hard red material. One end was full of normal polish compound while the other was full of this red material that was so hard that it actually took a polish during the faceted. We first sent this specimen to EAG for LA-ICP-MS evaluation. The images are below.

The results are seen in a graph provided to us by EAG. The red line is the green tourmaline, the black line is the red filler material. The findings were that this tourmaline has what one scientist terms a "highly abnormal" level of iron when matching to known tourmaline LA-ICP-MS. And the red filler material was composed of iron to an extremely high degree. The result was that this green tourmaline had an iron content that was almost equal to the main constituent element of silicon. Normally aluminum and silicon are the "matrix" level of elements, with the other elements considered "trace" elements. But in this stone, iron was present in "matrix" levels.
In order to further test this idea that iron was being used to artificially enhance the color of green tourmaline, and perhaps artificial levels of manganese was being used to improve the color of pink tourmaline, we sent the two specimens at left to EAG for analysis using LA-ICP-MS. These specimens demonstrated an unusual red or yellow fiber-glass looking crust on the surfaces that has become a "tell" for these stones that give this unusual reactions.
The graph below demonstrates the results of LA-ICP-MS testing of these specimens as compared to the normal LA-ICP-MS tourmaline averages. Trace elements that cause color will normally increase due to natural formation, but will still be in the "trace element" range. In the case of these two specimens, the green specimen showed "matrix" level of iron while the pink tourmaline showed "matrix" levels of manganese based on the reports from EAG. The graph shows how these numbers compare. The actual LA-ICP-MS results from EAG are below.

Conclusion

Given the overwhelming evidence that presents itself in a repeatable and predictable manner, we believe that tourmalines are being artificially color enhanced by some type of color infusion process that follows the general path of the process seen in Tibet andesine. We further believe that there is a significant amount of color infused tourmaline on the market that is not being properly disclosed. The main sources for the specimens we have found and confirmed are dealers from Thailand and China. The methods being used go beyond the ancient art of simply dying of minerals and goes into a level that allows for transparent gemstones to be artificially color enhanced by methods that make identification quite difficult. Clearly, just as was the case with Tibet andesine, we were only able to identify specific specimens as candidates based on the poor quality of treatment result that presented in the specimens. Specimens that are of high quality treatment would be extremely difficult to identify without advanced testing such as LA-ICP-MS or XRF.

There are a myriad of impacts on the market as a result of this situation. The mere use of the term "Paraiba Tourmaline" for tourmalines not from Paraiba, Brazil leaves the door open for unscrupulous dealers to take blue color infused tourmaline and put it on the market in direct competition with the true and natural Paraiba Tourmaline, and allow corrupt profits to be obtained as a result. This does not even count the extreme toll on consumer confidence that this situation foretells. Given the impact on consumer confidence that Tibet andesine fiasco caused, the general impact of undisclosed color infusion of gemstones of all types could well cause a virtual collapse of the natural, mined gemstone industry.
If color infusion can be done to feldspar and tourmalines, and we have a confirmed specimen of color infused garnet, it is a reasonable assumption that any gemstone can be color infused given the right set of conditions and the right "cooker" recipe.

The best short term solution to this situation is for buyers to find established dealers who have verifiable sources direct from the gemstone mines or market centers. Buying from unknown dealers who offer large quantities of cheap gemstones with unusual colors should be a cause for concern and investigation before committing to a large purchase.

We will continue to update our research on this issue as things develop. This is obviously not the end of the road on this issue by any means.

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