Pearl

Physical Properties

Hardness: 2.5-4.5 on Mohs scale; Color: Cream, white, pink, silver; Luster: Pearly (iridescent); Crystal structure: Orthorhombic (microcrystalline); Cleavage: None; Specific gravity: 2.60-2.85.

Formation & Geological History

Biogenic formation created within the soft tissue (mantle) of living shelled mollusks as a defense mechanism against irritants. Layers of nacre are deposited over time.

Uses & Applications

Primarily used in high-end jewelry (necklaces, earrings, rings) and as a decorative organic gemstone. Historically used in cosmetics and traditional medicine.

Geological Facts

Pearls are the only gemstones made by living creatures. The value is determined by luster, surface quality, shape, and size. Most modern pearls are 'cultured' rather than naturally found in the wild.

Field Identification & Locations

Identify by the 'tooth test' (feels gritty against teeth) and unique iridescent luster called orient. Commonly found in pearl oysters (saltwater) and freshwater mussels in lakes and rivers.

Identified on: 5/1/2026

Mode: Standard