mineral
Pearl
Organic gemstone (Calcium carbonate / CaCO3 + Conchiolin)
Hardness: 2.5-4.5; Color: White, cream, silver, black, pink; Luster: Pearly (iridescent); Crystal structure: Orthorhombic (Aragonite plates); Specific gravity: 2.60-2.85
- Hardness
- 2
- Color
- White, cream, silver, black, pink
- Luster
- Pearly (iridescent)
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Physical properties
Hardness: 2.5-4.5; Color: White, cream, silver, black, pink; Luster: Pearly (iridescent); Crystal structure: Orthorhombic (Aragonite plates); Specific gravity: 2.60-2.85
Formation & geological history
Biogenic formation; formed within the soft tissue of a living shelled mollusk as a defense mechanism against irritants by secreting layers of nacre.
Uses & applications
Predominantly used in jewelry, fashion ornamentation, and historically in cosmetics or medicine (pearl powder).
Geological facts
Unlike minerals formed in the earth, pearls are organic gemstones. The 'tooth test'—rubbing a pearl against your teeth—is a classic way to detect grittiness, which indicates a real pearl versus a smooth plastic fake.
Field identification & locations
Identify by its unique luster (orient) and surface temperature (cool to the touch). Found in oceans and freshwater lakes/rivers worldwide. Highly valued for its symmetry and 'clean' surface.
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