Onyx

Onyx is a chalcedony that occurs in bands of different colors. Onyx refers to a black and white banded variety of Agate and brown varieties are named Sardonyx. It is composed of relatively straight, parallel layers of different colors. This structure lends itself to cameo making.
It is usually cut en cabochon, or into beads, and is also used for intaglios and cameos. Some onyx is natural but much is produced by the staining of agate. It is available in the regions of USA, Germany, Brazil, Mexico, India, and Africa.

Hardness: 7