Chatoyancy

In gemology, chatoyancy (/ʃəˈtɔɪ.ənsi/ shə-TOY-ən-see), also called chatoyance or the cat's eye effect,^[1] is an optical reflectance effect seen in certain gemstones, woods, and carbon fiber. Coined from the French œil de chat, meaning 'cat's eye'. The chatoyant effect is typically characterized by one or more well-defined bands of reflected light, reminiscent of a cat's eye, which appear to glide across the material's surface as the chatoyant object or observer shifts position.

Chatoyancy is caused by either the presence of fibrous structures within the material, such as in tiger's eye quartz, or by fibrous inclusions and cavities, as seen in cat's eye chrysoberyl. In cat's eye chrysoberyl, the chatoyant effect is caused by the presence of rutile, composed mostly of titanium dioxide, which aligns perpendicularly to create the cat's eye appearance.^[2]^[3]

^ Schumann, Walter; Reinersmann, Daniel (2008). Minerals of the World. Translated by Shea, Elizabeth E. (2nd ed.). New York: Sterling Publishing. p. 19. ISBN 9781402753398.
^ Mukherjee, Swapna (2011). Applied mineralogy : applications in industry and environment. Dordrecht: Springer. ISBN 978-9400711617.
^ Hancock, Paul L.; Skinner, Brian J., eds. (2006). "gemstones". The Oxford companion to the earth (1st ed.). Oxford: Oxford Univ. Press. ISBN 9780198540397.

[1] Schumann, Walter; Reinersmann, Daniel (2008). Minerals of the World. Translated by Shea, Elizabeth E. (2nd ed.). New York: Sterling Publishing. p. 19. ISBN 9781402753398.

[2] Mukherjee, Swapna (2011). Applied mineralogy : applications in industry and environment. Dordrecht: Springer. ISBN 978-9400711617.

[3] Hancock, Paul L.; Skinner, Brian J., eds. (2006). "gemstones". The Oxford companion to the earth (1st ed.). Oxford: Oxford Univ. Press. ISBN 9780198540397.

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