gemstone
Black Onyx
Chalcedony (SiO2)
AI-generated identification · may be incorrectHardness of 6.5 to 7 on the Mohs scale, opaque black color, waxy to vitreous luster, and microcrystalline structure.
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Physical properties
Hardness of 6.5 to 7 on the Mohs scale, opaque black color, waxy to vitreous luster, and microcrystalline structure.
Formation & geological history
Forms by the deposition of silica in gas cavities of volcanic and sedimentary rocks over millions of years.
Uses & applications
Widely used in fine jewelry, cameos, beads, and ornamental carvings.
Geological facts
Black onyx has been used for signet rings and intaglios since ancient Roman and Greek civilizations.
Field identification & locations
Identified by its deep opaque black color, conchoidal fracture, and ability to take a high polish. Commonly sourced from Brazil, India, and Madagascar.
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