The diffusion of tourmaline has been greatly debated in the industry not only for the process itself, but also what to name the process. There are two things that our research has proven on this subject: #1. Tourmalines are indeed being treated to artificially impart colors and #2. Nobody really cares what we call it. We have chosen to name this treatment as color infused due to the suspected combination of using dyes to diffuse into the stones.
In truth, the artificial coloring of tourmaline by the introduction of outside coloring element has been well established by the ISG using both grass roots testing methods and advanced testing by LA-ICP-MS, XRF, Raman and other tests. There is a large segment of the industry who has chosen to ignore this issue until recently due to the extreme impact this issue has on the industry. Indeed, since sapphire has been confirmed to be diffused with beryllium and andesine has been confirmed as diffused with copper, it is not large stretch to believe that tourmaline and a variety of other gemstone can also be artificially color enhanced by use of other types of diffusion processes....no matter what one chooses to name them.
After several years of research costing tens of thousands of dollars, we have produced a library of microphotographs that serve to identify the treatments of tourmaline. And when we say treatments we meed plural in the classic sense of the term as there are several types of treatment that we have identified, and surely many more that we have not. For this purpose we want to show you some of these images below on this page, and then we will take the tourmaline color by color to give you a more specific method of identifying these treated gemstones for yourself.
Primary Test: Magnification will be your best tool for identification of treatments of tourmaline. Just as with the beryllium treated sapphire, the diffusion of outside elements into a tourmaline crystal will leave diagnostic internal features that make the evaluation fairly easy for those with training. Perhaps the most important feature will be unnaturally large growth tubes filled with filler material, fractures that contain filler material, red halos that are the result of the diffusion process, and uneven coloring throughout the stones.
Secondary Tests: The immersion cell will be an important secondary test as the process of artificially diffusing color into tourmalines never creates a uniform color within the stone, the color zoning will also vary across the stone except in the very rare of cases. So be sure to always have your immersion cell and the photographs on the ensuing pages handy when doing any evaluations of tourmaline.
Additional Important Information
Natural untreated tourmalines will normally be cut so that the “C” axis is parallel to the table of the finish stone in order to get the best light return. This causes the natural growth tubes to point essentially from side to side when the stone is viewed through the table. Due to the treatment process the diffusion treated tourmalines will normally have the “C” axis cut perpendicular to the table. This will cause the growth tubes to point up through the table, and be pointed from top to bottom in the stone rather than side to side. When you find growth tubes in a tourmaline that are orientated perpendicular to the table and pointing straight up toward you when viewing the stone face up, this is a very strong indicator that you have a treated tourmaline.
Important Note on the term “Paraiba Tourmaline”: Due to the wide spread treatment of tourmalines it is not proper to use the term “Paraiba Tourmaline” for any tourmaline that does not originate from Paraiba, Brazil. The Lab Manual Harmonization Committee has approved the use of the term “Paraiba” for any tourmaline with “Paraiba-like colors” without doing any research on the various treatments of tourmaline out on the market. The LMHC has done great harm to the true Paraiba, Brazil tourmaline industry by their unwarranted actions. We urge our members to not follow the erroneous path that the LMHC has led so many of this industry down regarding the use of this important gemstone name. The term “Paraiba Tourmaline” should only be used to describe natural tourmalines originating from the region around Paraiba, Brazil.
Repair and Setting: Since the color infusion process has not been fully exposed the impact of this treatment on the integrity of the gemstone structure is not fully known. Therefore extreme caution should be used when repairing any jewelry items with suspected color infusion treated tourmaline, including unsetting for prong repair and sizing. No ultrasonic cleaning in hot solution and not torch heat near the stone.