Onyx

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Onyx
A photograph shawin a slice through a stane wi the face displayin alternating bands o bricht reid, bricht white an tan
A slice o sardonyx (width = 2.5 cm)
General
Category Oxide mineral
Formula
(repeating unit)
Silica (silicon dioxide, SiO2)
Identification
Formula mass 60 g / mol
Color Various
Crystal seestem Trigonal, Monoclinic
Cleavage Absent
Fractur Uneven, conchoidal
Mohs scale hairdness 6–7
Luster Vitreous, silky
Streak White
Diaphaneity Translucent
Specific gravity 2.65–2.667

Onyx is a bandit variety o chalcedony. The colours o its bands range frae white tae almaist every colour (save some shades, such as purpie or blue). Commonly, specimens o onyx contain bands o black an/or white.