gemstone
Onyx
Silicon Dioxide (Chalcedony), SiO2
AI-generated identification · may be incorrectHardness of 6.5 to 7 on the Mohs scale, typically black with parallel white or colored bands, waxy to vitreous luster, and cryptocrystalline structure.
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Physical properties
Hardness of 6.5 to 7 on the Mohs scale, typically black with parallel white or colored bands, waxy to vitreous luster, and cryptocrystalline structure.
Formation & geological history
Forms by the deposition of silica in gas cavities of volcanic rocks or in limestone fissures over geological timeframes.
Uses & applications
Widely used in jewelry, cameos, beads, and ornamental carvings due to its ability to be intricately shaped and polished.
Geological facts
Ancient Greeks and Romans used onyx for intaglio gems and seals because the layered colors created striking contrasts when carved.
Field identification & locations
Identified by its dense black color, conchoidal fracture, and high hardness; commonly sourced from Brazil, India, and the USA.
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