Onyx is a variety of chalcedony in the quartz family. Naturally is more banded black and white and can be dyed to be a true black. Onyx is a stone of inner strength and enhances endurance and persistence. The ancient Roman's believed it bestowed courage going into battle and carried amulets engraved with Mar, the god of war, into battle. This mineral also enhances high level of focus and can boost memory.