Tiger's eye (also called tiger eye) is a chatoyant gemstone that is usually a metamorphic rock that is a golden to red-brown colour, with a silky lustre. Members of the Quartz group, Tiger's eye and the related blue-coloured mineral Hawk's eye gain their silky, lustrous appearance from the parallel intergrowth of quartz crystals and altered amphibole fibres that have mostly turned into limonite.
Cut, Treatment, and Imitation
The gems are usually cut en cabochon in order to best display their chatoyancy. Red stones are brought about through gentle heat treatment. Dark stones have had their colours improved and been artificially lightened using nitric acid treatments.
Honey-colored stones have been used to imitate the much higher valued cat's eye chrysoberyl (cymophane), but the overall effect is unconvincing. Artificial fibre optic glass is a common imitation of tiger's eye, and is produced in a wide range of colours.