a publication of the International School of Gemology 15.November.2012

Color Infused Imperial Topaz

As we narrow down the scope of our investigation into this color infusion process being done to colored gemstones, we continue to find certain common denominators that prevail throughout the various species of gemstones being treated. We recently obtained a parcel of Imperial Topaz rough from a dealer in Europe. The origin of the parcel is reported to be Thailand. Utilizing the protocols that we have developed from our investigations of color infused andesine, corundum, tourmaline, tanzanite and others we were able to identify that this parcel has received virtually the same type of treatment as the other gemstones. The parcel is seen at left, and in the banner above is more of this parcel along with a natural Imperial Topaz specimen obtained for the ISG Student Reference Collection several years ago. We maintain a collection of known control stones specifically for comparison testing and evaluation.

 

Although the parcel had a variety of color intensities, the stones appeared to have almost a neon type coloring that was unlike natural Imperial Topaz that we have and have worked with. At right is one of the crystals in dark field and side transmitted illumination to show the transparent quality of these specimens.

When viewed with our LED MikeLite Dual Fiber Optic the neon colors of this topaz became very apparent and easy to photograph. What was most remarkable was that the internal colors demonstrated the same "Mardi Gras" type flash colors that we previously found in tanzanite. These are not stress generated interference colors but are rather a flash effect off of some type of coloring inside the crystal. The colors have become predictable and repeatable in the blue, yellow and pink pastel colors.

Viewed through darkfield illumination and higher magnification we were able to view some type of yellow coloring material, along with the neon flash colors seen in the previous image. These flash colors repeat through these gemstones in the blue, yellow and pink colors with the yellow being the dominant color observed.

In the immersion cell the colors were found to be concentrated along the fracture and fissure lines as previously seen with color infused tourmaline and tanzanite, along with what we term the "Mardi Gras" colors as seen in the image panel below right.

These "Mardi Gras" flash colors are becoming well known with this treatment in tanzanites and now topaz. As seen at left and below, these are not stress induced colors but rather a color sheen visible from the surface of the infusion material inside the stone when specific types of light are applied. As seen in these images the colors are repeatable in form and pattern, and are seen in these patterns in specimens throughout this parcel of topaz.

One of the most remarkable properties that we have discovered in a variety of these color infused gemstones is the added fluorescence due to the reaction of the color infusion material. As seen in this GIF slide of one of the topaz specimens at left, while the coloring material is not apparent in ambient light, under long wave UV radiation the fluorescent reaction is significant and quite unusual. This unusual fluorescence has also been found in color infused "Tibet andesine" obtained from a variety of sources.

The most compelling evidence of this treatment can be seen in this image below. Although it appeared an effort had been made to clean the surface of these crystals, under high magnification we were able to observe what has now become a common denominator to this treatment among a variety of gemstones. The surface openings contained rounded quartz pieces, metal chunks that proved to be annealed graphite as seen previously in the color infused Tibet andesine specimens, and hardened water glass also found on Tibet andesine and a variety of other treated stones. We believe the annealed graphite to be a relic of the crucibles used to treat these and other stones. The image below was the first of many that we took of these features. The "Mardi Gras" colors seen below are inside the stone and not a surface feature.

At left is a 90x image of the rounded quartz along with annealed graphite stuck in a surface breaking fissure of this topaz. By Raman we were able to verify that these materials exactly match the identification of materials from the color infused Tibet andesine.

Below is a profound image of surface fissures filled with hardened water glass, rounded quartz and annealed graphite. All images taken with our Meiji Techno GEMT-5BFDF microscope available from the ISG.

Conclusion:

At this point there is little doubt that these Imperial Topaz crystals have been subjected to a color infusion treatment that is very much like, if not the same as, the treatment we found previously with tanzanite, andesine, etc... We were previously informed that when the Thai and Chinese cookers found a way to color infuse gemstones it was not limited to one variety or species, but rather the method could be applied to virtually any gemstone. We believe that this years long ISG research effort has uncovered the truth of that report, and confirmed the facts surrounding this issue.