Large Pink Sapphire with Diffusion-Induced Star

Photomicrograph by Christopher P. Smith

Measuring approximately 25 x 22 mm, the oval pink cabochon in this ring proved to be a heated-treated pink sapphire with a Ti-diffusion-induced star.

The thin, sub-surface milky sheen/layer seen in the sapphire using fibre-optic lighting is an indication that the star is the result of a diffusion process. As shown on the left at 60x magnification, minute needles can be discerned. A thermally altered partially-healed fissure with a melted/drippy appearance can be seen at the lower left. The three prominent straight lines are parting planes.

The resulting research was published in the Journal of Gemmology, Vol 35, No 4, 2016 pp. 291-292.

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