Lab Notes
Gems & Gemology, Spring 2017, Vol. 53, No. 1

Rubellite with Incredibly Strong “Pink Sleeves”

Xiaodan Jia and Mei Mei Sit
Tubes and fractures associated with pink sleeves.
Left: Surface-reaching growth tubes and fractures associated with strong pink sleeves, whose color became weaker as they penetrated the stone’s interior; field of view 2.83 mm. Right: Looking down the length of the growth tubes, bleeding of pink color was observed; field of view 1.13 mm. Photomicrographs by Xiaodan Jia.

GIA’s Hong Kong laboratory recently examined a purplish red cabochon-cut rubellite tourmaline. Standard gemological tests yielded a spot refractive index of 1.64 and specific gravity of 3.06, which are consistent with tourmaline. Magnification revealed strong doubling, fluid inclusions, and parallel growth tubes, all typical of tourmaline. What made this specimen unusual were its localized zones of strong pink coloration surrounding surface-reaching growth tubes and fractures (above left). Bleeding of pink color from the growth tubes into the body of the stone was best observed looking down the length of the growth tubes (above right); the pink color gradually faded away into the surrounding tourmaline host. This type of zoning has come to be known as “pink sleeves.” It is different from dye concentrations, which would only be located inside the surface-reaching growth tubes and fractures.

Radiation-induced pink sleeves surrounding surface-reaching growth tubes and fractures have been reported in Paraíba tourmalines from Mozambique. The formation is believed to be due to a radioactive solution entering the growth tubes and fractures by capillary action, and the presence of pink sleeves proves that the stone has not undergone heat treatment. (J.I. Koivula et al., “Solution-generated pink color surrounding growth tubes and cracks in blue to blue-green copper-bearing tourmalines from Mozambique,” Spring 2009 G&G, pp. 44–47). To the best of our knowledge, the incredibly strong pink sleeves seen in this rubellite have not been previously reported in either Paraíba or rubellite tourmaline.

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