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Materials :
Onyx
(on´Iks) - variety of cryptocrystalline quartz
, differing from agate 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. Onyx was used in Roman
times for the fabrications of vases and cups.“Onyx marble,” “Mexican
onyx,” and “Oriental
alabaster” are terms applied to travertine.