gemstone

Pearl

Calcium carbonate (CaCO3) + organic conchiolin

Hardness: 2.5-4.5 on Mohs scale; Color: Creamy white to silver; Luster: Pearly (iridescent); Crystal structure: Orthorhombic (as aragonite); Specific gravity: 2.60-2.85

Hardness: 2
Color: Creamy white to silver
Luster: Pearly (iridescent)

Identified July 17, 2026More gemstone →

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Physical properties

Hardness: 2.5-4.5 on Mohs scale; Color: Creamy white to silver; Luster: Pearly (iridescent); Crystal structure: Orthorhombic (as aragonite); Specific gravity: 2.60-2.85

Formation & geological history

Organic gemstone formed within the soft tissue (mantle) of a living shelled mollusk. Layers of nacre are deposited over an irritant over several years.

Uses & applications

Primarily used in jewelry such as necklaces, earrings, and rings; also historically used in cosmetics and medicines.

Geological facts

Unlike minerals formed in the earth, pearls are of biological origin. The largest pearl ever found, the Pearl of Puerto, weighs 34 kg.

Field identification & locations

Identify by the 'tooth test' (feels gritty against teeth) or by observing concentric growth rings under magnification. Commonly found in saltwater oysters and freshwater mussels worldwide.

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