mineral

Mother of Pearl (Nacre)

Aragonite (layered with organic polymers), CaCO3

Hardness: 3.5-4.5 (Mohs); Color: White, cream, or iridescent silvery-white; Luster: Pearly to iridescent; Crystal Structure: Orthorhombic (as aragonite platelets); Cleavage: None; Specific Gravity: 2.7-2.8

Hardness: 3
Color: White, cream, or iridescent silvery-white
Luster: Pearly to iridescent

Identified January 29, 2026More mineral →

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Physical properties

Formation & geological history

Biogenic formation; produced by certain mollusks as an inner shell layer. It is formed by the secretion of thin, alternating layers of aragonite and conchiolin (a protein) by the mantle tissue of the organism. This specimen is modern (Holocene).

Uses & applications

Primarily used in jewelry (beads, pendants), watch faces, musical instrument inlays, furniture marquetry, and high-end button manufacturing.

Geological facts

The iridescent 'orient' of mother of pearl is caused by the interference of light as it reflects off thin, overlapping microscopic layers of aragonite. It is chemically identical to the pearl itself.

Field identification & locations

Identify in the field by its distinct iridescent 'shimmer' that changes when rotated under light, and a hardness that is significantly lower than quartz or glass. Commonly harvested from pearl oysters, freshwater mussels, and abalone found in both marine and freshwater environments worldwide.

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