Onyx ia a chalcedony that occurs in bands of different colours. 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 colours. This structure lends itself to
cameo making.
It is usually cut into 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
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