mineral
Black Onyx
Silicon dioxide (SiO2)
Hardness: 6.5-7 (Mohs), Color: Black, Luster: Vitreous, Crystal Structure: Trigonal (Cryptocrystalline), Cleavage: None, Specific Gravity: 2.65-2.67
- Hardness
- 6
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Physical properties
Hardness: 6.5-7 (Mohs), Color: Black, Luster: Vitreous, Crystal Structure: Trigonal (Cryptocrystalline), Cleavage: None, Specific Gravity: 2.65-2.67
Formation & geological history
Formed through the deposition of silica in gas cavities (vesicles) in lava. This particular black variety is often created by treating gray chalcedony with sugar solution and heating it.
Uses & applications
Primarily used in jewelry for beads, pendants, and rings. Also used for ornamental carvings and historic cameos.
Geological facts
Onyx is a variety of chalcedony with parallel banding. In ancient times, it was believed to provide protection and strength during battle.
Field identification & locations
Identify by its waxy luster, lack of transparency, and resistance to scratches. Found globally in volcanic deposits, specifically in Brazil, India, and Madagascar.
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