Onyx is a banded variety of the oxide mineral chalcedony. The colors of its bands range from white to almost every color (with the exception of some shades, such as purple or blue). Commonly, specimens of onyx contain bands of black and/or white.
Imitation Rhodium uses a similar-looking material to substitute for rhodium. It makes the jewelry more affordable, but at the same time keeps the same appearance and quality as a rhodium coating.