Onyx
A cryptocrystalline form of quartz. The colors of its bands range from white to almost every color, except blue and purple. Commonly, specimens of onyx available contain bands of colors of white, tan, and brown. Pure black onyx is common as well. It has a long history of use for hardstone carving and jewelery, where it is usually cut as a cabochon, or into beads, and is also used for intaglio or cameo engraved gems.
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