The mottled, translucent, brownish covering of the shells of certain tortoises or turtles, especially the hawksbill, used to make combs, eyewear, jewelry, and other objects. It is formed of the same protein substance (keratin) which forms horns, hoofs, claws, and other parts of some animals. Pictured here is a Russian tortoise shell, one of many species. Beware: some species may be endangered. "Tortoiseshell" is sometimes used to refer to a faux or synthetic imitation of this material.