An optical phenomenon which appears as a bright band of light across certain gemstones that when cut as cabochons, reproduce the appearance of the narrowed pupil of a cat, hence the more common name ‘cat’s eye’. The reflection is from fine inclusions, all parallel in one direction. and visible when the base of the cabochon is cut in parallel with the direction of the inclusions.

Cat’s-Eye Chrysoberyl Ring Exhibiting Chatoyancy.