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)

Identified April 21, 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; 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.

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