mineral

Pearl (as a biogenic mineral/gemstone)

Calcium Carbonate (mostly Aragonite), CaCO3

Hardness: 2.5-4.5 (Mohs scale); Color: White, cream, pink, silver; Luster: Pearly (iridescent); Crystal structure: Orthorhombic (as aragonite microlayers); Cleavage: None; Specific gravity: 2.60-2.85

Hardness: 2
Color: White, cream, pink, silver
Luster: Pearly (iridescent)

Identified April 25, 2026More mineral →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Hardness: 2.5-4.5 (Mohs scale); Color: White, cream, pink, silver; Luster: Pearly (iridescent); Crystal structure: Orthorhombic (as aragonite microlayers); Cleavage: None; Specific gravity: 2.60-2.85

Formation & geological history

Biogenic formation within the soft tissue of a living shelled mollusk. Layers of nacre are secreted around an irritant over several years. They are common in both saltwater and freshwater environments.

Uses & applications

Primarily used in jewelry (earrings, necklaces, rings) and as a traditional symbol of wealth and purity. Crushed pearls are sometimes used in cosmetics or traditional medicine.

Geological facts

Pearls are the only gemstones produced by a living organism. Unlike most other gems, they require no cutting or polishing to reveal their natural beauty. The most expensive pearl ever found is valued at approximately $100 million.

Field identification & locations

Identify by the 'tooth test' (feeling a gritty texture against teeth) or by observing the orient/iridescence under light. Commonly found in pearl oysters and freshwater mussels in regions like the Persian Gulf, China, and Japan.

Other mineral specimens

See all

Sandstone (with potential mineral staining/concretions)

Arenite (SiO2 based)

sedimentary

Schist

Metamorphic

Epidote

Epidote | Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH)

metamorphic

Nephrite Jade

Nephrite

Mineral/Rock

Banded Gneiss (River Rock/Pebble)

Gneiss (specifically a banded variety often found as a river rock)

Metamorphic Rock

Green Apatite on Albite

Fluorapatite [Ca5(PO4)3F] on Albite [Na(AlSi3O8)]

mineral