mineral

Pearl

Aragonite (CaCO3) with Conchiolin

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

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

Identified April 21, 2026More mineral →

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Physical properties

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

Formation & geological history

Formed biogenically within the soft tissue (mantle) of a living shelled mollusk or fossilized conchiolin. Layers of calcium carbonate are deposited around an irritant such as a grain of sand or parasite.

Uses & applications

Primarily used in fine jewelry (necklaces, rings, earrings). Also used in cosmetics and traditional medicine when ground into powder.

Geological facts

Pearls are the only gemstones in the world to be extracted from a living animal. The 'Tooth Test' is a famous historical way to identify them: real pearls feel gritty when rubbed against the edge of a tooth, while fakes feel smooth.

Field identification & locations

Identify by inspecting the surface for orient (iridescence) and checking for small natural imperfections. Cultured pearls are grown in pearl farms in saltwater (oysters) or freshwater (mussels).