gemstone
Black Onyx
Silicon Dioxide (SiO2) - Chalcedony
Hardness 6.5-7 on Mohs scale, deep solid black color, waxy to sub-vitreous luster, microcrystalline trigonal structure, conchoidal fracture, specific gravity ~2.65.
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Physical properties
Hardness 6.5-7 on Mohs scale, deep solid black color, waxy to sub-vitreous luster, microcrystalline trigonal structure, conchoidal fracture, specific gravity ~2.65.
Formation & geological history
Formed in low-temperature volcanic and sedimentary environments through the deposition of silica in gas cavities of lavas.
Uses & applications
Widely used in jewelry such as rings, beads, and pendants, as well as decorative carvings, ornamental items, and stone healing practices.
Geological facts
Natural solid black onyx is relatively rare; historically, much black onyx traded commercially is microcrystalline chalcedony that has been dyed to enhance color uniformity.
Field identification & locations
Look for a smooth, fine-grained, non-porous surface with a soft, uniform sheen. Highly accessible in gemstone markets worldwide.
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