gemstone
Black Onyx
Chalcedony (SiO2)
Hardness: 6.5 to 7 on the Mohs scale, Color: Black, Luster: Vitreous to waxy, Crystal Structure: Trigonal (microcrystalline quartz), Cleavage: None, Specific Gravity: 2.60 to 2.65
- Hardness
- 6
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Physical properties
Hardness: 6.5 to 7 on the Mohs scale, Color: Black, Luster: Vitreous to waxy, Crystal Structure: Trigonal (microcrystalline quartz), Cleavage: None, Specific Gravity: 2.60 to 2.65
Formation & geological history
Formed by the deposition of silica in gas cavities of lava and in other geological environments, often found in sedimentary and volcanic rocks.
Uses & applications
Widely used in jewelry, cabochons, beads, cameos, and ornamental carvings.
Geological facts
Black onyx has been used for thousands of years in signet rings, seals, and various protective amulets throughout ancient civilizations like Egypt and Rome.
Field identification & locations
Identified by its deep black color, microcrystalline structure, conchoidal fracture, and lack of cleavage. Commonly sourced from Brazil, India, Madagascar, and the USA.
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