mineral

Limonite (Iron Ore)

FeO(OH)·nH2O (Hydrated iron(III) oxide-hydroxide)

Hardness: 4.0-5.5 on Mohs scale; Color: Yellowish-brown to dark brown; Luster: Dull, earthy; Crystal structure: Amorphous; Cleavage: None; Specific Gravity: 2.7-4.3

Hardness: 4
Color: Yellowish-brown to dark brown
Luster: Dull, earthy

Identified June 8, 2026More mineral →

Identify your own rocks.

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

App Store Google Play

Physical properties

Hardness: 4.0-5.5 on Mohs scale; Color: Yellowish-brown to dark brown; Luster: Dull, earthy; Crystal structure: Amorphous; Cleavage: None; Specific Gravity: 2.7-4.3

Formation & geological history

Formed usually from the oxidation and hydration of iron-rich sulfide minerals or the weathering of other iron minerals like hematite and magnetite in sedimentary environments.

Uses & applications

Historically used as a major source of iron ore; currently used as a pigment in paints (yellow ochre) and as an abrasive.

Geological facts

Limonite is not a true mineral but a mineraloid mixture of various hydrated iron oxides. It has been used as a pigment since prehistoric times, notably in cave paintings like those at Lascaux.

Field identification & locations

Identified in the field by its characteristic yellowish-brown streak (when rubbed against porcelain) and its earthy, rusted appearance. Often found in swamp edges or weathered rock outcrops.

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

Biotite Schist

Biotite-rich Schist [K(Mg,Fe)3AlSi3O10(F,OH)2]

metamorphic