gemstone
Black Onyx
Chalcedony (SiO2)
Hardness of 6.5 to 7 on the Mohs scale, opaque black color with a waxy to vitreous luster, microcrystalline (cryptocrystalline) quartz structure, conchoidal fracture, and specific gravity of 2.60 to 2.65.
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Physical properties
Hardness of 6.5 to 7 on the Mohs scale, opaque black color with a waxy to vitreous luster, microcrystalline (cryptocrystalline) quartz structure, conchoidal fracture, and specific gravity of 2.60 to 2.65.
Formation & geological history
Formed by the deposition of silica in gas cavities of volcanic lavas or groundwater solutions, often occurring in secondary environments.
Uses & applications
Widely used in jewelry making, rings, cameos, beads, and ornamental carvings.
Geological facts
Black onyx has been used for thousands of years in ancient Egyptian, Greek, and Roman civilizations for signet rings and protective amulets.
Field identification & locations
Identified by its deep solid black color, lack of natural bands (unlike banded onyx), and smooth waxy polish. Commonly found in Brazil, India, Madagascar, and the USA.
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