Hawk’s eye is a blue-gray to blue-green opaque gemstone variety of fibrous quartz. More specifically, it is a variety of macrocrystalline quartz. Hawk’s eye is actually a pseudomorph of quartz. A pseudomorph is one mineral that changes into another mineral over time. In the case of hawk’s eye, it began its life as crocidolite and was later transformed into quartz. Crocidolite is a fibrous blue mineral belonging to the riebeckite family of amphibole silicates. It is considered to be one of the several forms of asbestos. The transformation of hawk’s eye begins as quartz slowly becomes embedded between the fibers of crocidolite, eventually completely replacing it while retaining the fibrous shape of the original mineral.