Pearl (as a biogenic mineral/gemstone)

Physical Properties

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

Formation & Geological History

Biogenic formation within the soft tissue of a living shelled mollusk. Layers of nacre are secreted around an irritant over several years. They are common in both saltwater and freshwater environments.

Uses & Applications

Primarily used in jewelry (earrings, necklaces, rings) and as a traditional symbol of wealth and purity. Crushed pearls are sometimes used in cosmetics or traditional medicine.

Geological Facts

Pearls are the only gemstones produced by a living organism. Unlike most other gems, they require no cutting or polishing to reveal their natural beauty. The most expensive pearl ever found is valued at approximately $100 million.

Field Identification & Locations

Identify by the 'tooth test' (feeling a gritty texture against teeth) or by observing the orient/iridescence under light. Commonly found in pearl oysters and freshwater mussels in regions like the Persian Gulf, China, and Japan.

Identified on: 4/25/2026

Mode: Standard