Tiger's eye (also Tigers Eye, Tiger Eye) is a chatoyant gemstone that is usually yellow- to red-brown, with a silky lustre. It is a fibrous silicified crocidolite (in the quartz family). The gems are usually cut en cabochon in order to best display their chatoyancy. Red stones are brought about through heat treatment. Honey-coloured stones have been used to imitate the much higher valued cat's eye chrysoberyl (cymophane), but the overall effect is unconvincing. An incompletely silicified blue variant is called Hawk's eye.