"Chatoyance" is when a band of reflected light, also referred to as a cat's eye" shows in a gemstone. As the stone moves in relation to the viewer, the band of light appears to move across the stone. This movement in the light makes the stones look alive and gives them added interest, which is why they are so popular.
The term "chatoyancy" comes from the French term oeil de chat, meaning ‘cat’s eye’.
One of the most common gemstones which exhibit this affect is the gemstone known as "Tiger's-Eye".
Many spiritual benefits are attributed to cat's eye gems. Wearing them is said to bring luck to the wearer (especially financial or business)