mineral

Pearl

Calcium carbonate (CaCO3) - mainly Aragonite

Hardness: 2.5-4.5 (Mohs scale); Color: White, cream, pink, lavender, or gold; Luster: Pearly (iridescent nacre); Crystal Structure: Orthorhombic/Amorphous; Specific Gravity: 2.60-2.85

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

Identified January 22, 2026More mineral →

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Physical properties

Hardness: 2.5-4.5 (Mohs scale); Color: White, cream, pink, lavender, or gold; Luster: Pearly (iridescent nacre); Crystal Structure: Orthorhombic/Amorphous; Specific Gravity: 2.60-2.85

Formation & geological history

Formed as a biological defense mechanism within the soft tissue of shelled mollusks (oysters or mussels). Concentric layers of aragonite and conchiolin are deposited around an irritant. Modern pearls are typically cultured (farmed).

Uses & applications

Primarily used in jewelry for necklaces, bracelets, and earrings. Also used in cosmetics and traditional medicine when ground into powder.

Geological facts

Pearls are the only gemstones created by living animals. The largest pearl ever found is the Pearl of Lao Tzu, weighing over 14 pounds. They are the birthstone for June.

Field identification & locations

Identify by the 'tooth test' (rubbing against teeth feels gritty, not smooth), or checking for subtle surface irregularities. Commonly found in coastal salt waters or freshwater rivers and lakes worldwide.

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