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"Cat's eye effect" redirects here. For other uses, see Cat's eye.

In gemology, chatoyancy (/ʃəˈtɔɪ.ənsi/ shə-TOY-ən-see), or chatoyance or cat's eye effect,[1] is an optical reflectance effect seen in certain gemstones. Coined from the French "œil de chat," meaning "cat's eye," chatoyancy arises either from the fibrous structure of a material, as in tiger's eye quartz, or from fibrous inclusions or cavities within the stone, as in cat's eye chrysoberyl.[2][3] The precipitates that cause chatoyance in chrysoberyl are the mineral rutile, composed mostly of titanium dioxide. Examined samples have yielded no evidence of tubes or fibres.[citation needed] The rutile precipitates all align perpendicularly with respect to cat's eye effect. It is reasoned that the lattice parameter of the rutile matches only one of the three orthorhombic crystal axes of the chrysoberyl, resulting in preferred alignment along that direction.

Quartz cats-eye



The term "cat's eye", when used by itself as the name of a gemstone, refers to a cat's eye chrysoberyl.[citation needed] It is also used as an adjective which indicates the chatoyance phenomenon in another stone, e.g., cat's eye aquamarine.

In woodworking[edit]

Chatoyancy in woodworking occurs where certain finishes cause the wood grain to achieve a striking three-dimensional appearance, also referred to as "pop-the-grain", "wood iridescence", "moire", "vibrancy", "shimmer" or "glow".[4] This highly sought-after effect is sometimes called "wet look", since wetting wood with water often displays the chatoyancy, albeit only until the wood dries. Oil finishes, epoxy, and shellac can strongly bring out the "wet look" effect.

See also[edit]


  1. ^ Reinersmann, Walter Schumann ; [translated by Elizabeth E.; Shea], Daniel (2008). Minerals of the world (2nd ed.). New York, NY.: Sterling Pub. Co. p. 19. ISBN 9781402753398. 
  2. ^ Mukherjee, Swapna (2011). Applied mineralogy : applications in industry and environment. Dordrecht: Springer. ISBN 9400711611. 
  3. ^ Hancock, Paul L.; Skinner, Brian J., eds. (2006). "gemstones". The Oxford companion to the earth (1st ed.). Oxford: Oxford Univ. Press. ISBN 9780198540397. 
  4. ^ Dresdner, Michael. "Start to Finish: the Endurance Test," Woodworker's Journal (Jun. 2000).
  • Webster, R., Jobbins, E. A. (Ed.). (1998). Gemmologist's compendium. St Edmundsbury Press Ltd, Bury St Edwards.
  • Mitchell, T. et al. Proceedings of the Electron Microscopy Society of America (EMSA), 1982.