When a rutile-silk containing sapphire (such as this stone from Sri Lanka) is heated, the titanium from the rutile moves into solid solution in the sapphire, coloring the area around the rutile blue, creating a distinctive “ink spot” internal diffusion pattern.
Natural Sapphire • Sri Lanka (Ceylon) • Enhancements: Heat (H) • Lighting Conditions: Light Field + Oblique Fiber Optic
Photographer: Richard W. Hughes •
Image Number: A-001-0988-2 • Date Posted: 12 May 2015
Koivula, J.I. (1987) Internal diffusion. Journal of Gemmology, Vol. 20, No. 7/8, pp. 474–477; RWHL*.