Samples of blue to blue-green, copper-bearing tourmaline containing surface-reaching growth tubes surrounded by intense pink “sleeves” have recently been seen in the trade. In response to rumors of possible diffusion treatment, GIA Laboratory staff members John I. Koivula, Kevin Nagle, Andy Shen and Philip Owens carefully examined several of these tourmalines over the past year. Based on this examination, the GIA team determined that the pink zones were produced by fluids containing naturally occurring radioactive material. %% In all instances where pink colouration was observed, the growth features surrounded by the pink colour reached the surface of the stones. In cases where growth tubes did not reach the surface, no pink colour was seen. When these pink zones were viewed down their length, the colour was observed to bleed out into the surrounding tourmaline host, becoming weaker until it gradually faded away. If post-growth matter in the tube created a blockage, colouration occurred only to that point. Additionally, any cracks extending from or between the growth tubes also showed a pink colour. %% Radiation is known to produce pink-to-red colour in tourmaline. The colouration of surface-reaching features in tourmaline by invading radioactive fluids has not been reported in the literature; however, there have been reports of both smoky quartz and green diamonds with colouration that was caused by exposure to naturally occurring radioactive fluids. This mechanism explains all the observations of pink and red in these tourmalines. %% “Since radiation is the cause of pink colour in tourmaline, the presence of these features should not be attributed to any type of intentional diffusion, but rather to the influx of radioactive fluids in their post-growth environment,” said GIA Laboratory Chief Gemologist John I. Koivula, one of the study’s authors. %% All the copper-bearing tourmaline samples with this feature observed thus far have come from Mozambique. This suggests that this type of inclusion feature may be characteristic of that locality. %% The presence of the pink zones in these otherwise blue to blue-green gems also provides proof that the host tourmalines were not heat treated, since the temperature needed to treat copper-bearing Mozambique material exceeds the published stable temperature for pink-to-red colour in tourmaline. %% An article by Koivula and his colleagues detailing these observations will appear in the Spring 2009 issue of GIA’s Gems & Gemology, due out in April.