Organic Mineraloid
Pearl (in a decorative hair comb setting)
Calcium carbonate (CaCO3) primarily as Aragonite, bonded with Conchiolin
Hardness: 2.5–4.5 (Mohs scale); Color: White, cream, or silver shimmer; Luster: Pearly (iridescent nacre); Crystal structure: Orthorhombic micro-crystals; Specific Gravity: 2.60–2.85
- Hardness
- 2
- Color
- White, cream, or silver shimmer
- Luster
- Pearly (iridescent nacre)
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Physical properties
Hardness: 2.5–4.5 (Mohs scale); Color: White, cream, or silver shimmer; Luster: Pearly (iridescent nacre); Crystal structure: Orthorhombic micro-crystals; Specific Gravity: 2.60–2.85
Formation & geological history
Biogenic formation within the soft tissue (mantle) of a living shelled mollusk. Layers of nacre are deposited over an irritant. While they occur in modern ecosystems, fossilized pearls date back to the Cretaceous period.
Uses & applications
Primarily used in jewelry, fashion accessories, and cosmetics. Cultured pearls are common in contemporary industry, while natural pearls remain high-value collector items.
Geological facts
La Peregrina is one of the most famous pearls in history, once owned by Mary I of England and later Elizabeth Taylor. Unlike minerals formed in the earth, pearls are unique because they are created by living organisms.
Field identification & locations
Identification includes the 'tooth test' (feeling a gritty texture against teeth) or observing overlapping plate-like structures under magnification. Found in marine and freshwater environments globally, particularly in areas like the Persian Gulf or oyster farms in Japan.
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