Chatoyant Quartz as it is also known, there are three varieties of this type of quartz. It is the inclusion of croicidolite (blue asbestos) that causes a cat’s eye effect known as chatoyancy.
Each stone will display different colors according the exact nature and amount of the inclusions. Grayish yellow, semi translucentappearance of the cat’s eye is due to inclusions of croicidolite and , less commonly hornblende, it has quite a silky luster. Tiger’s Eye is black with iron oxide staining that gives the yellow and golden brown stripes. Hawk’s Eye forms when the croicidolite changes to quartz but the blue-gray or blue-green color of the original material remains. Whew!