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onyx(ŏn`ĭks), variety of cryptocrystalline quartzquartz,
one of the commonest of all rock-forming minerals and one of the most important constituents of the earth's crust. Chemically, it is silicon dioxide, SiO2.
..... Click the link for more information. , differing from agateagate
, translucent, cryptocrystalline variety of quartz and a subvariety of chalcedony. Agates are identical in chemical structure to jasper, flint, chert, petrified wood, and tiger's-eye, and are often found in association with opal.
..... Click the link for more information. only in that the bands of which it is composed are parallel and regular. Its appearance is most striking when the bands are of sharply contrasting colors; black and white specimens are often used for cameos. Onyx was used in Roman times for the fabrications of vases and cups. Sardonyx contains onyx and carnelian or sard. "Onyx marble," "Mexican onyx," and "Oriental alabaster" are terms applied to travertinetravertine
, form of massive calcium carbonate, CaCO3, resulting from deposition by springs or rivers. It is often beautifully colored and banded as a result of the presence of iron compounds or other (e.g., organic) impurities.
..... Click the link for more information. .
a mineral; a variety of agate with alternating black and white bands. Onyx is used as ornamental material or as a gem-stone. Cameos are carved from onyx, with the dark bands serving as the background and the light-colored bands used for the images.
Banded chalcedonic quartz, in which the bands are straight and parallel; natural colors are usually red or brown with white, although black is occasionally encountered.
A banded, varicolored form of quartz, closely related to agate; cut into slabs, polished, and used for decorative building stone.
provokes disagreement and separates lovers. [Gem. Symbolism: Kunz, 98–99]
1. a variety of chalcedony with alternating black and white parallel bands, used as a gemstone. Formula: SiO2
2. a compact variety of calcite used as an ornamental stone; onyx marble. Formula: CaCO3