mineral

Mother of Pearl (Nacre)

Nacre (Aragonite/Conchiolin), CaCO3 + Organic Polymers

Hardness: 3.5-4.5 (Mohs scale); Color: Iridescent white, cream, or silver; Luster: Pearly/Iridescent; Crystal Structure: Orthorhombic (Aragonite platelets); Cleavage: None; Specific Gravity: 2.7–2.8

Hardness: 3
Color: Iridescent white, cream, or silver
Luster: Pearly/Iridescent

Identified March 31, 2026More mineral →

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Physical properties

Formation & geological history

Formed biogenically by mollusks as an inner shell layer. Epithelial cells secrete aragonite platelets separated by organic conchiolin, a process ongoing for hundreds of millions of years in marine and freshwater environments.

Uses & applications

Extensively used in jewelry, watch faces, musical instrument inlays (fretboards), luxury furniture marquetry, and high-end buttons.

Geological facts

Nacreous luster is caused by the interference of light reflecting off microscopic hexagonal platelets of aragonite, which are only 300 to 500 nanometers thick—roughly the wavelength of visible light.

Field identification & locations

Identify by its unique 'orient' (rainbow-like iridescence) and smooth, cool touch. Commonly found within the shells of pearl oysters, freshwater mussels, and abalone. Collectors look for high luster and lack of surface pitting.

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