It differs from black onyx in terms of both physical and chemical makeup. Chalcedony, or Black Agate, is a member of the quartz family and is recognized for having a finely grained microcrystalline structure. In contrast to black onyx, a kind of cryptocrystalline quartz, black agate often has a waxy shine and is translucent. Black Agate Jewelry is mined from volcanic ash and comes from Brazil, India, Africa, the USA, Uruguay, and Madagascar, among other places in the world.