Definition of cat's-eye

i. Any gemstone that, when cut en cabochon, exhibits under a single strong point source of light a narrow, well-defined chatoyant band or streak that moves across the summit of the gemstone, shifts from side to side as it is turned, and resembles a slit pupil of the eye of a cat. Internal reflection of light from parallel inclusions of tiny fibrous crystals or from long parallel cavities or tubes causes the cat's-eye.

Ref: AGI

ii. Alternate term for tiger's-eye, the silicified form of crocidolite asbestos; sometimes polished and used as ornaments.

iii. A greenish gem variety of chrysoberyl that exhibits chatoyancy.

Synonym of: Cymophane, oriental cat's-eye

iv. A variety of minutely fibrous, grayish-green quartz (chalcedony) that exhibits an opalescent play of light.

Synonym of: occidental cat's-eye

v. A yellowish-brown silicified variety of crocidolite. The term used alone properly applies only to (c).

Compare with: tiger's-eye