mineral

Pearl

Calcium Carbonate (Aragonite) - CaCO3

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

Hardness: 2
Color: White, cream, pink, silver
Luster: Pearly (iridescent)

Identified May 9, 2026More mineral →

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Physical properties

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

Formation & geological history

Formed biogenically within the soft tissue of living shelled mollusks as a response to an irritant. Layers of nacre are deposited over time. Most modern specimens are cultured in freshwater or saltwater environments.

Uses & applications

Primarily used in jewelry (necklaces, earrings, rings) and as a birthstone. Historically used in cosmetics and traditional medicine.

Geological facts

Pearls are the only gemstones created by a living animal. The 'Hope Pearl' is one of the largest and most famous natural pearls in existence, weighing 450 carats.

Field identification & locations

Identify by the 'tooth test' (feels gritty when rubbed against teeth) and the presence of orient (iridescence). Found worldwide in oceans and rivers wherever oysters, mussels, and clams thrive.