gemstone

Pearl

Pearl; chiefly aragonite (CaCO₃) with conchiolin

AI-generated identification · may be incorrect

Organic gem formed in mollusks; typically white or cream with nacreous luster. Mohs hardness about 2.5–4.5; aragonite crystals are orthorhombic, though the layered structure gives pearls their distinctive sheen. The image shows assorted drilled pearls, likely cultured.

Identified October 5, 2026More gemstone →

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Physical properties

Formation & geological history

Pearls form as mollusks deposit nacre around an irritant or implanted nucleus. Natural pearls occur over years in marine or freshwater shellfish; cultured pearls are produced in farms, and their age is generally not identifiable from appearance.

Uses & applications

Used mainly in jewelry and ornamentation; pearl nacre has limited decorative and specialty uses.

Geological facts

Unlike most gems, pearls are biogenic and commonly worn without faceting or polishing.

Field identification & locations

Identify by the layered, iridescent nacre and slight surface variation; a gentle tooth test can distinguish nacre from smooth glass or plastic, but may damage jewelry. Cultured pearls are farmed worldwide, especially in China, Japan, and the South Pacific.