Onyx
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Onyx is a typically black-and-white banded variety of agate, a silicate mineral. The bands can also be monochromatic with alternating light and dark bands. Sardonyx is a variety with red to brown band
Onyx with concentric banding
Cabochons of red onyx, also called sardonyx
Black onyx with white streaks
The Gemma Augustea is a Roman cameo produced 9–12 AD and carved in a two-layered onyx gem (19 × 23 cm).
Chalcedony
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Chalcedony is an aggregate of cryptocrystalline or microcrystalline silica, or in simpler terms, a mass of individual silica crystals that are too small to be seen without magnification. It is compose
Onyx
…fingernail'. Onyx with pink and white bands can sometimes resemble a fingernail. The English word "nail" is cognate with the Greek word. Onyx is formed of chalcedony bands in alternating colors. It is cryptocrystalline, consisting of fine intergrowths of the silica minerals quartz and moganite. Its bands are parallel…
A botryoidal geode specimen from Chihuahua
A rare pseudomorph of a spiral Turritella-like snail shell that has been replaced by chalcedony
Chalcedony mouse, by Avenir Sumin
Agate