mineral
Black Onyx
Silicon Dioxide (SiO2)
Hardness: 6.5-7 Mohs; Color: Black with potential white bands; Luster: Vitreous to dull; Crystal structure: Trigonal/Microcrystalline; Cleavage: None; Specific gravity: 2.65-2.67
- Hardness
- 6
- Color
- Black with potential white bands
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6.5-7 Mohs; Color: Black with potential white bands; Luster: Vitreous to dull; Crystal structure: Trigonal/Microcrystalline; Cleavage: None; Specific gravity: 2.65-2.67
Formation & geological history
Formed through the deposition of silica in gas cavities (vesicles) in lava. It is found in igneous environments and can date back to various geological eras.
Uses & applications
Widely used in jewelry (rings, beads), ornamental carvings, and historically used for intaglio and cameo seals.
Geological facts
The name comes from the Greek word 'onyx', meaning claw or fingernail, because its white layers can resemble one. It was highly prized in ancient Roman and Greek cultures.
Field identification & locations
Identify by its waxy luster, hardness (won't scratch with a knife), and parallel banding if present. Common in Brazil, India, and Madagascar.
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Arenite (SiO2 based)
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Schist
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Epidote
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Nephrite Jade
Nephrite
Mineral/Rock
Banded Gneiss (River Rock/Pebble)
Gneiss (specifically a banded variety often found as a river rock)
Metamorphic Rock
![Biotite Schist (Biotite-rich Schist [K(Mg,Fe)3AlSi3O10(F,OH)2]) — metamorphic](https://media.rock.id/9ca564b5-bc87-402b-965a-69b21f9aa6bf-thumbnail.jpg)
Biotite Schist
Biotite-rich Schist [K(Mg,Fe)3AlSi3O10(F,OH)2]
metamorphic