Pearl

Physical Properties

Hardness: 2.5–4.5 Mohs. Color: White, cream, pink, silver, or black. Luster: Pearly (iridescent). Crystal structure: Orthorhombic (aragonite) or Hexagonal (calcite). Cleavage: None. Specific gravity: 2.6–2.85.

Formation & Geological History

Formed as a defense mechanism within the soft tissue (mantle) of living shelled mollusks, such as oysters or mussels, when an irritant becomes trapped. They are composed of concentric layers of nacre.

Uses & Applications

Primarily used in high-end jewelry (rings, necklaces, earrings) and as a birthstone for June. In some cultures, pulverized pearl is used in cosmetics and traditional medicine.

Geological Facts

Pearls are the only gemstones made by living animals. The most famous large pearl is the 'La Peregrina,' once owned by Elizabeth Taylor and Spanish royalty.

Field Identification & Locations

Identify in jewelry settings by checking for natural surface irregularities and the 'tooth test' (natural pearls feel gritty against teeth). Common locations include the Persian Gulf and coastal waters of Japan and Australia.

Identified on: 4/20/2026

Mode: Standard