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 • Sri Lanka (Ceylon) • Enhancements: None Detected (None) • Lighting Conditions: Dark Field
Photographer: Richard W. Hughes •
Image Number: A-001-3194-2 • Date Posted: 10 November 2015
Koivula, J.I. (1987) Internal diffusion. Journal of Gemmology, Vol. 20, No. 7/8, pp. 474–477; RWHL*.
Gübelin, E.J. and Koivula, J.I. (2005) Photoatlas of Inclusions in Gemstones, Volume 3. Basel, Switzerland, Opinio Publishers, 672 pp.; RWHL*.