Organic Mineraloid
Pearl (nacre)
Calcium Carbonate (mostly CaCO3 as Aragonite) and Conchiolin
Hardness: 2.5–4.5; Color: White, cream, or silver; Luster: Pearly (iridescent); Crystal structure: Orthorhombic (microcrystalline); Specific Gravity: 2.60–2.85
- Hardness
- 2
- Color
- White, cream, or silver
- Luster
- Pearly (iridescent)
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Physical properties
Hardness: 2.5–4.5; Color: White, cream, or silver; Luster: Pearly (iridescent); Crystal structure: Orthorhombic (microcrystalline); Specific Gravity: 2.60–2.85
Formation & geological history
Formed within the soft tissue (mantle) of living shelled mollusks; concentric layers of nacre are deposited around an irritant.
Uses & applications
Primarily used in jewelry, fashion accessories, and as a collector's gemstone; historically used in cosmetics and traditional medicines.
Geological facts
Pearls are the only gemstones created by living creatures. Unlike mineral stones, they require no cutting or polishing to reveal their natural beauty.
Field identification & locations
Identify by the 'tooth test' (rub gently against teeth to feel a gritty texture) or by observing orient and overtones; commonly found in both saltwater (oysters) and freshwater (mussels).
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