Cat's eye (SiO2 or BeAl2O4) displays the simplest form of chatoyancy (reflections of light from microscopic inclusions of other minerals within the stone), in which needle-like inclusions, most often rutile, are oriented in one direction producing a single band of light, much like the vertical pupil in the eye of a cat.


The term cat's eye is applied to two different minerals: one a variety of chrysoberyl (most often used by jewelers) and the other a variety of quartz. Oftentimes the quartz variety will be called Occidental cat's eye to differentiate it from the more valuable Oriental cat's eye, the chrysoberyl variety. The most desirable form of cat's eye is honey-yellow or greenish-yellow. The main source of cat's eye quartz is the gem gravels in Sri Lanka.


Hindus once believed that a cat's eye guarded its owner's health and provided assurance against poverty.