mineral

Pearl

Biogenic Calcium Carbonate (Aragonite/Calcite), CaCO3

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

Hardness: 2
Color: White, cream, pink, silver, or black
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

Formation & geological history

Formed within the soft tissue of a living shelled mollusk. It is biogenic, created through the secretion of nacre (mother-of-pearl) around an irritant. It is organic in origin rather than strictly inorganic/geological.

Uses & applications

Primarily used in jewelry (necklaces, earrings, rings) and as a gemstone. Historically used in cosmetics and medicines (pearl powder).

Geological facts

Pearls are the only gemstones made by living animals. The world's largest pearl, the Pearl of Lao Tzu, weighs over 6 kilograms. They are the traditional birthstone for June.

Field identification & locations

Identify by the 'tooth test' (feels gritty against teeth) or by observing surface growth patterns under magnification. Found in marine or freshwater environments globally where oysters and mussels thrive.

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