This image clearly illustrates what master photomicrographer John Koivula has termed “chromophore cannibalization.” As titanium is drawn out of solid solution to form exsolved rutile silk, the area in the vicinity is decolorized, losing its blue color. This is a natural process and is the reverse of “internal diffusion,” where heat treatment sends the titanium back into solution, creating blue clouds or “inkspots” around the rutile remnants.
Natural Sapphire • Madagascar • Enhancements: None Detected (None) • Lighting Conditions: Diffuse Light Field (Transmitted Light)
Photographer: Patharaphum Sudprasert •
Image Number: A-001-4761-1 • Date Posted: 19 February 2016
Koivula, J.I. (1987) Internal diffusion. Journal of Gemmology, Vol. 20, No. 7/8, pp. 474–477; RWHL*.