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
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A rare pseudomorph of a spiral Turritella-like snail shell that has been replaced by chalcedony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
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
Chalcedony
…chalcedony, which is colored by chromium compounds. It is also known as "mtorolite" when found in Zimbabwe and "chiquitanita" when found in Bolivia. Onyx is a variant of agate with black and white banding. Similarly, agate with brown, orange, red and white banding is known as sardonyx. Chalcedony was…
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).