mineral
Black Onyx or Dyed Agate Node
Cryptocrystalline Quartz (SiO2)
Hardness: 6.5-7 on Mohs scale; Color: Black with potential faint banding; Luster: Waxy to vitreous; Crystal Structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture).
- Hardness
- 6
- Color
- Black with potential faint banding
- Luster
- Waxy to vitreous
Identified More mineral →
Explore Black Onyx or Dyed Agate Node in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6.5-7 on Mohs scale; Color: Black with potential faint banding; Luster: Waxy to vitreous; Crystal Structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture).
Formation & geological history
Forms in gas cavities (vesicles) in volcanic rocks where silica-rich fluids deposit layers of microcrystalline quartz over time. While natural black onyx exists, many uniformly black specimens are historically produced by dying grey chalcedony.
Uses & applications
Used extensively in jewelry for cabochons, beads, and carvings. Also used for ornamental objects and as a grounding stone in metaphysical practices.
Geological facts
The name 'Onyx' comes from the Greek word 'onux', meaning fingernail or claw, referring to the translucency of the stone. Historically, it was used by Romans for signet rings and cameos.
Field identification & locations
Identified by its conchoidal fracture, lack of visible crystals, and hardness that scratches glass. It feels dense and cold to the touch. The dark, weathered exterior (cortex) is typical of agate nodes found in volcanic regions.
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