mineral

Pearl

Calcium carbonate (CaCO3) in the form of aragonite or calcite

Hardness: 2.5-4.5 (Mohs scale), Color: White, cream, pink, silver, or black, Luster: Pearly (iridescent), Crystal Structure: Orthorhombic, Cleavage: None, Specific Gravity: 2.60-2.85

Hardness: 2

Identified May 1, 2026More mineral →

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Physical properties

Hardness: 2.5-4.5 (Mohs scale), Color: White, cream, pink, silver, or black, Luster: Pearly (iridescent), Crystal Structure: Orthorhombic, Cleavage: None, Specific Gravity: 2.60-2.85

Formation & geological history

Formed within the soft tissue (mantle) of a living shelled mollusk. When an irritant becomes trapped inside, the mollusk deposits layers of calcium carbonate around it. Most modern pearls are cultured rather than natural.

Uses & applications

Primarily used in jewelry such as necklaces, earrings, and rings. Historically used in cosmetics and as a symbol of status and wealth.

Geological facts

The pearl is the only gemstone created by a living animal. The most famous pearl in the world, La Peregrina, was owned by Mary Tudor of England and later Elizabeth Taylor.

Field identification & locations

Identify by the 'tooth test' (feels gritty against teeth) or by checking for concentric growth rings under a loupe. Found in saltwater (oysters) and freshwater (mussels) globally, especially in Japan, China, and Australia.

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