mineral

Pearl

Calcium Carbonate (CaCO3)

Hardness: 2.5-4.5 (Mohs), Color: White to cream with iridescent luster (nacre), Crystal structure: Orthorhombic (Aragonite), Cleavage: None, Specific Gravity: 2.60-2.85

Hardness: 2

Identified June 20, 2026More mineral →

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Physical properties

Hardness: 2.5-4.5 (Mohs), Color: White to cream with iridescent luster (nacre), Crystal structure: Orthorhombic (Aragonite), Cleavage: None, Specific Gravity: 2.60-2.85

Formation & geological history

Formed biogenically within the soft tissue of living shelled mollusks as a defense mechanism against irritants over months to years.

Uses & applications

Primarily used in jewelry such as necklaces, earrings, and rings; historically used for cosmetics and medicines in powdered form.

Geological facts

Pearls are the only gemstones created by living animals. Natural pearls are extremely rare; most available pearls today are 'cultured' pearls grown in oyster farms.

Field identification & locations

Identified by their unique 'orient' or luster and smooth or slightly gritty texture on the teeth. Found in freshwater and saltwater environments globally.