Primary Test: Magnification will be the only test you need due to the identification of this material. The classic yellow and red filler in the growth tubes, the uneven coloration of the stones, and the overly large growth tubes in general are clear indicators of a treatment effort being made on these stones. We have provided a wide selection of microphotographs in order to provide you with the best opportunity to identify this treatment based on the inclusions.
You should remember that the yellow and red filler material is residual material from the diffusion treatment process. That is why this material is caught up in the fissures and engorged growth tubes. This material does not reflect the color that was being imparted into the stone, but rather is a flux used in the process that did not work properly. This is why you will see yellow and red colors even in stones that have been artificially colored blue.
Secondary Tests: Many of the color variations due to this diffusion treatment are much easier to see using a simple immersion cell. Always keep one handy to confirm your findings under magnification.
Remember: 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: Due to the wide spread treatment of blue tourmalines it is not proper to use the term “Paraiba Tourmaline” for any blue tourmaline that does not originate from Paraiba, Brazil. The Lab Manual Harmonization Committee has approved the use of the term “Paraiba” for any blue color tourmaline without doing any research on the various treatments of blue 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.
Repair and Setting: Since the dyefusion 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 dyefusion treated tourmaline, including unsetting for prong repair and sizing. No ultrasonic cleaning in hot solution and no torch heat near the stone.