Onyx, a banded variety of the quartz family, is mined in Brazil, India, Madagascar, U.S.A and Uruguay. The only difference between onyx and other banded agates is that the stripes of onyx are even and uniform. Black Onyx's uniform black color is achieved by dyeing and or by heat treating. The name Onyx is a Greek word meaning claw or fingernail, as it was once believed that onyx was created from the goddess Venus's fingernail clippings. Onyx and Sardonyx are essentially the same stone: onyx will have a black base, and sardonyx has a brown base.