mineral

Black Onyx

Cryptocrystalline Quartz (SiO2)

Hardness: 6.5-7 on Mohs scale; Color: Black with potential white bands; Luster: Vitreous to waxy; Crystal Structure: Hexagonal (trigonal); Cleavage: None (conchoidal fracture).

Hardness: 6
Color: Black with potential white bands
Luster: Vitreous to waxy

Identified July 21, 2026More mineral →

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Physical properties

Hardness: 6.5-7 on Mohs scale; Color: Black with potential white bands; Luster: Vitreous to waxy; Crystal Structure: Hexagonal (trigonal); Cleavage: None (conchoidal fracture).

Formation & geological history

Forms in the gas cavities (vesicles) of lava, typically through the deposition of silica from groundwater at low temperatures. Common in volcanic regions worldwide.

Uses & applications

Primarily used in jewelry for cabochons, beads, and carvings. Also used as a healing stone in metaphysical practices and for decorative stone inlay.

Geological facts

The name 'Onyx' comes from the Greek word for fingernail or claw. Historically, most black onyx on the market today is actually gray chalcedony that has been dyed black, which is a globally accepted industry standard.

Field identification & locations

In the field, it is identified by its hardness (it can scratch glass), its heavy density compared to plastic, and its cold feel to the touch. It is often found in river beds or volcanic outcrops.