mineral

Pearl

Calcium carbonate (CaCO3) as Aragonite or Calcite

Hardness: 2.5-4.5; Color: White, cream, pink, or gray; Luster: Pearly (iridescent nacre); Crystal Structure: Orthorhombic/Trigonal; SG: 2.60-2.85

Hardness: 2
Color: White, cream, pink, or gray
Luster: Pearly (iridescent nacre)

Identified May 1, 2026More mineral →

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Physical properties

Hardness: 2.5-4.5; Color: White, cream, pink, or gray; Luster: Pearly (iridescent nacre); Crystal Structure: Orthorhombic/Trigonal; SG: 2.60-2.85

Formation & geological history

Biogenic formation within the soft tissue (mantle) of a living shelled mollusk. Created as a defense mechanism against irritants.

Uses & applications

Primarily used in jewelry (necklaces, earrings, rings) and as a decorative organic gemstone for centuries.

Geological facts

Pearls are the only gemstones created by living animals. 'La Peregrina' is one of the most famous historical pearls, once owned by Mary I of England and Elizabeth Taylor.

Field identification & locations

Identify by their unique luster and the 'tooth test' (feels gritty against teeth). Found in freshwater and saltwater environments across the globe where oysters and mussels reside.

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