CAT'S-EYE, a name given to several distinct minerals, their common characteristic being that when cut with a convex sur face they display a luminous band, like that seen by reflection in the eye of a cat. (I) Precious, oriental or chrysoberyl cat's-eye. This, the rarest of all, is a chatoyant variety of chrysoberyl (q.v.), showing in the finest stones a very sharply defined line of light. (2) Quartz cat's-eye. This is the common form of cat's-eye, in which the effect is due to the inclusion of parallel fibres of as bestos. It is obtained chiefly from Ceylon, but, though coming from the East, it is often called "occidental cats-eye"—a term intended simply to distinguish it from the finer oriental stone. It is readily distinguished by its inferior density, its specific gravity being only 2.65, while that of oriental cat's-eye is as high as 3.7. A greenish fibrous quartz, cut as cat's-eye, occurs at Hof and some other localities in Bavaria. (3) Crocidolite cat's-eye, a beautiful golden brown mineral, with silky fibres, found in Griqua land West, and much used in recent years as an ornamental stone, sometimes under the name of "South African cat's-eye." It con sists of fibrous quartz, coloured with oxide of iron, and results from the alteration of crocidolite (q.v.). (4) Corundum cat's eye. In some asteriated corundum (see ASTERIA) the star is im perfect and may be reduced to a luminous zone, producing an indistinct cat's-eye effect. (F. W. R.)