mineral
Onyx
Chalcedony (SiO2)
Mohs hardness of 6.5 to 7, color is typically black or dark with parallel bands, waxy to vitreous luster, trigonal crystal system, conchoidal fracture.
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Physical properties
Mohs hardness of 6.5 to 7, color is typically black or dark with parallel bands, waxy to vitreous luster, trigonal crystal system, conchoidal fracture.
Formation & geological history
Formed in gas cavities of volcanic and sedimentary rocks where silica-rich groundwater deposits microcrystalline quartz layers over long periods.
Uses & applications
Commonly used in jewelry, cameos, beads, and ornamental carvings.
Geological facts
Onyx has been used since ancient Egyptian times for carving into protective talismans, seals, and cameos.
Field identification & locations
Easily identified by its deep black color and microcrystalline structure, often found worldwide including Brazil, India, and the USA.
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