Pearl (as a Biogenic Mineral)

Physical Properties

Hardness: 2.5–4.5 (Mohs); Color: White, cream, pink, silver; Luster: Pearly (iridescent nacre); Crystal Structure: Orthorhombic; Specific Gravity: 2.60–2.85

Formation & Geological History

Biogenic formation within the soft tissue (mantle) of a living shelled mollusk. It is formed by depositing thin concentric layers of nacre around an irritant.

Uses & Applications

Primarily used in jewelry (necklaces, earrings, rings) and as a June birthstone. Historically used in cosmetics and traditional medicine.

Geological Facts

Pearls are the only gemstones created by a living animal. The 'La Peregrina' pearl is one of the most famous, owned by royalty and Elizabeth Taylor.

Field Identification & Locations

Identify by the 'tooth test' (real pearls feel gritty against teeth) and by checking for surface overtones and depth of luster. Often found in oysters and mussels in both saltwater and freshwater.

Identified on: 4/21/2026

Mode: Standard