gemstone
Black Onyx
Chalcedony (SiO2)
Hardness of 6.5-7 on the Mohs scale, solid black color, vitreous to waxy luster, microcrystalline (cryptocrystalline) crystal structure, conchoidal fracture with no true cleavage, specific gravity of 2.60-2.65.
Identified More gemstone →
Explore Black Onyx in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness of 6.5-7 on the Mohs scale, solid black color, vitreous to waxy luster, microcrystalline (cryptocrystalline) crystal structure, conchoidal fracture with no true cleavage, specific gravity of 2.60-2.65.
Formation & geological history
Formed by the deposition of silica from underground water solutions, typically in gas cavities of volcanic and sedimentary rocks. Geologically ancient, often millions of years old.
Uses & applications
Widely used in jewelry, signet rings, carvings, beads, and ornamental objects.
Geological facts
Black onyx has been used historically since ancient Egyptian and Roman times for cameos and intaglios. Much of the commercial black onyx today is color-enhanced gray chalcedony or agate.
Field identification & locations
Easily identified by its deep, uniform black color and waxy luster when polished. It is commonly found globally, including in Brazil, India, Madagascar, and the US.
More like this
Other gemstone specimens
Gemstone Ring
N/A - Set piece of jewelry, likely Amethyst or Garnet with Diamond or CZ
gemstone
Diamond and Gold Jewelry
Carbon (Diamond) / Au (Gold)
gemstone
Ammolite
Ammolite (Biogenic Aragonite with trace elements; fossils of Placenticeras meeki and Placenticeras intercalare)
mineral
Cubic Zirconia (simulant) or Diamond
ZrO2 (Cubic Zirconia) or C (Diamond)
gemstone
Red Jasper
Silicon Dioxide (SiO2) with Hematite inclusions
sedimentary
Black Opal Ring (Carved Opal)
Hydrated Silicon Dioxide (SiO2·nH2O)
gemstone