Onyx (Black) and Mother of Pearl Inlay

Physical Properties

Hardness: Onyx 6.5-7, Mother of Pearl 3.5; Color: Jet black and iridescent white/rainbow; Luster: Vitreous to pearly; Structure: Cryptocrystalline to organic biomineral layers.

Formation & Geological History

Onyx is formed by the deposition of silica in gas cavities in lava. Mother of Pearl is an organic-inorganic composite material produced by some mollusks as an inner shell layer.

Uses & Applications

Primarily used in jewelry, ornamental carvings, and decorative inlay work (intarsia).

Geological Facts

Black onyx is often treated with heat or chemicals to achieve its uniform black color. Mother of pearl, or nacre, is the same material that pearls are made of.

Field Identification & Locations

Identify by the high-contrast black backdrop against iridescent flakes. Often featured in Southwestern or Zuni-style silver jewelry.

Identified on: 4/25/2026

Mode: Standard