Chatoyancy

question mark article explains the optical phenomenon of chatoyance click button to shop online with Stone Mania

 

Chatoyancy or chatoyance is an optical phenomenon which can be seen in certain minerals and gemstones one of the best known of which is tigers eye.  Originating from the French word for cat's eye, it is caused because of either the fibrous structure of a mineral or the fibrous inclusions or cavities which reflect from within.  Chatoyancy can usually be seen as the mineral or gemstone is gently moved around hence catching the light at various angles and it gives the impression that the patterns or markings are moving.

Further Reading:
Understanding chatoyancy