Pearl

Physical Properties

Hardness: 2.5–4.5 on Mohs scale; Color: Cream, pink, silver, white; Luster: Pearly (iridescent); Crystal structure: Orthorhombic (Aragonite micro-crystals); Specific gravity: 2.60–2.85

Formation & Geological History

Biogenic formation inside the soft tissue (mantle) of a living shelled mollusk. It is formed as a defense mechanism against irritants by secreting layers of nacre. While they are organic gems, they are classified as mineraloids.

Uses & Applications

Primary use is in jewelry (necklaces, earrings, rings) and as a birthstone for June. Historically used in cosmetics and traditional medicine in powder form.

Geological Facts

A pearl is the only gemstone in the world that is extracted from a living animal. The oldest known pearl jewelry belonged to a Persian Princess who died in 520 BC.

Field Identification & Locations

Identify by the 'tooth test' (feels gritty when rubbed against teeth) or by observing the concentric layers under magnification. Found in both saltwater (oysters) and freshwater (mussels) environments globally, with major hubs in Japan, China, and the South Pacific.

Identified on: 5/1/2026

Mode: Standard