Garnet in Sapphire

Michaela Stephan

The author recently examined a 3.26 ct sapphire that changed from green-blue in fluorescent light to reddish purple in incandescent light. The color-change sapphire contained a large eye-visible crystal inclusion (see above). Microscopic examination of the singly refractive inclusion revealed garnet’s characteristic dodecahedral crystal shape with rounded edges.

Of all the possible inclusions contained within sapphire, garnet is a rare and beautiful occurrence. When garnet crystal inclusions do occur, they often indicate an origin of Tanzania or the U.S. state of Montana (E.J. Gübelin and J.I. Koivula, Photoatlas of Inclusions in Gemstones, Vol. 3, Opinio-Verlag Publishers, Basel, Switzerland, 2008, pp. 228–242). In this sapphire, a large vibrant orange garnet is followed by a trail of dust-like rutile particles, much like an asteroid streaking across the night sky.