Pearl

Physical Properties

Hardness: 2.5–4.5 (Mohs); Color: White, cream, pink, silver; Luster: Pearly (orient); Crystal structure: Orthorhombic (Aragonite) / Hexagonal (Calcite); Specific gravity: 2.60–2.85.

Formation & Geological History

Biogenic formation within the soft tissue of a living shelled mollusk. Layers of nacre are deposited around an irritant. While pearls themselves are modern biogenic materials, the biological process has existed since the Paleozoic Era.

Uses & Applications

Primarily used in jewelry making (necklaces, earrings, rings) and as a traditional symbol of luxury. Also used in cosmetics and traditional medicine in some cultures (pearl powder).

Geological Facts

Pearls are the only gemstones made by living animals. The 'La Peregrina' is one of the most famous pearls in history, once owned by Mary I of England and later Elizabeth Taylor.

Field Identification & Locations

Identify by the 'tooth test' (rubbing against teeth reveals a gritty texture, unlike glass or plastic mimics) and the presence of slight irregular bands or 'rings' (as seen on these freshwater pearls). Commonly found in freshwater mussels in rivers or saltwater oysters in oceans.

Identified on: 4/21/2026

Mode: Standard