mineraloid
Pearl
Aragonite and Conchiolin (CaCO3 + organic protein)
Hardness: 2.5–4.5 on Mohs scale; Color: white, cream, pink, silver, or black; Luster: Pearly (iridescent nacre); Crystal system: Orthorhombic (microcrystalline); Specific gravity: 2.60–2.85.
- Hardness
- 2
- Color
- white, cream, pink, silver, or black
- Luster
- Pearly (iridescent nacre)
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Physical properties
Hardness: 2.5–4.5 on Mohs scale; Color: white, cream, pink, silver, or black; Luster: Pearly (iridescent nacre); Crystal system: Orthorhombic (microcrystalline); Specific gravity: 2.60–2.85.
Formation & geological history
Formed biogenically inside the soft tissue (mantle) of a living shelled mollusk. It is composed of concentric layers of calcium carbonate deposited around a microscopic irritant.
Uses & applications
Primarily used in jewelry for necklaces, earrings, and rings. Historically used in cosmetics and medicines (pearl powder) in various cultures.
Geological facts
Pearls are the only gemstones created by living animals. 'La Peregrina' is one of the most famous pearls in history, once owned by Mary I of England and later Elizabeth Taylor.
Field identification & locations
Identified by their orient (iridescence) and the 'tooth test' (feeling gritty when rubbed against the edge of a tooth). Founding locations include the Persian Gulf, Japanese coasts, and various freshwater rivers.
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