Pearl

Physical Properties

Hardness: 2.5–4.5 (Mohs scale); Color: White, cream, pink, silver, or black; Luster: Pearly (iridescent); Crystal structure: Orthorhombic (as aragonite); Cleavage: None; Specific Gravity: 2.60–2.85

Formation & Geological History

Formed within the soft tissue of a living shelled mollusk. It is biogenic, created through the secretion of nacre (mother-of-pearl) around an irritant. It is organic in origin rather than strictly inorganic/geological.

Uses & Applications

Primarily used in jewelry (necklaces, earrings, rings) and as a gemstone. Historically used in cosmetics and medicines (pearl powder).

Geological Facts

Pearls are the only gemstones made by living animals. The world's largest pearl, the Pearl of Lao Tzu, weighs over 6 kilograms. They are the traditional birthstone for June.

Field Identification & Locations

Identify by the 'tooth test' (feels gritty against teeth) or by observing surface growth patterns under magnification. Found in marine or freshwater environments globally where oysters and mussels thrive.

Identified on: 4/25/2026

Mode: Standard