Onyx is a banded variety of chalcedony. The colors of its bands range from white to almost every color (save some shades, such as purple or blue). Commonly, specimens of onyx contain bands of black and/or white. Onyx comes through Latin (of the same spelling), from the Greek ὄνυξ, meaning "claw" or "fingernail". With its flesh tone color, onyx can be said to resemble a fingernail.
Onyx is formed of bands of chalcedony in alternating colors. It is cryptocrystalline, consisting of fine inter-growths of the silica minerals quartz and moganite. Its bands are parallel to one another, as opposed to the more chaotic banding that often occurs in agates.
Onyx is formed in the gas cavities of lava. Some onyx is natural but much of the material in commerce is produced by the staining of agate.
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