Pearl

Physical Properties

Hardness: 2.5–4.5 (Mohs scale); Color: White, cream, pink, silver; Luster: Pearly (iridescent); Crystal Structure: Orthorhombic (microcrystalline layers); Cleavage: None; Specific Gravity: 2.60–2.85

Formation & Geological History

Formed biologically within the soft tissue of a living shelled mollusk. It is an organic mineraloid created when an irritant enters the shell and the mollusk layers nacre (mother-of-pearl) around it.

Uses & Applications

Primarily used in jewelry (necklaces, earrings, rings) and as a gemstone. Historically used in cosmetics and medicines.

Geological Facts

Unlike traditional minerals mined from the earth, pearls are organic. The oldest pearl jewelry ever found dates back to about 4300 BC. Most pearls today are 'cultured,' meaning humans manually induce the nacre coating process.

Field Identification & Locations

Identify by the 'tooth test' (real pearls feel gritty against teeth, imitations feel smooth). Common locations include the Persian Gulf, regions off Sri Lanka, and freshwater rivers in China and the US.

Identified on: 4/21/2026

Mode: Standard