mineral

Black Onyx or Dyed Agate Node

Cryptocrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

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 July 5, 2026More 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.

App Store Google Play

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.