mineral
Black Onyx
Silicon Dioxide (SiO2)
Hardness: 6.5-7 Mohs; Color: Jet black (often dyed); Luster: Vitreous when polished; Crystal Structure: Hexagonal (trigonal), microcrystalline; Specific Gravity: 2.65-2.677
- Hardness
- 6
- Color
- Jet black (often dyed)
- Luster
- Vitreous when polished
Identified More mineral →
Explore Black Onyx in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6.5-7 Mohs; Color: Jet black (often dyed); Luster: Vitreous when polished; Crystal Structure: Hexagonal (trigonal), microcrystalline; Specific Gravity: 2.65-2.677
Formation & geological history
Formed in the gas cavities of volcanic rocks through the deposition of silica. Found in various geological ages and secondary deposits like river gravels.
Uses & applications
Used extensively in jewelry for beads, cameos, and intaglios. Historically popular for ornamental carvings and healing stone collections.
Geological facts
Historically, what we call Black Onyx is often natural gray chalcedony that has been dyed black. It is one of the most popular gemstones for signet rings throughout history.
Field identification & locations
Identify by its smooth, glassy surface and high polish. Unlike obsidian, it is unlikely to have tiny bubbles or flow lines. Common locations include Brazil, India, and Madagascar.
More like this
Other mineral specimens
Sandstone (with potential mineral staining/concretions)
Arenite (SiO2 based)
sedimentary
Schist
Schist
Metamorphic
Epidote
Epidote | Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH)
metamorphic
Gypsum (variety Selenite or Alabaster)
Calcium sulfate dihydrate (CaSO4·2H2O)
Mineral
Nephrite Jade
Nephrite
Mineral/Rock
Granite
Granite (Phaneritic intrusive igneous rock)
igneous