mineral

Limonite Nodule

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

Hardness: 4-5.5 on the Mohs scale; Color: Yellowish-brown, brown, to dark reddish-brown; Luster: Earthy, submetallic, or silky; Crystal structure: Amorphous or microcrystalline (pseudomorphic after other minerals); Cleavage: None; Specific gravity: 2.7-4.3.

Hardness: 4-5
Color: Yellowish-brown, brown, to dark reddish-brown
Luster: Earthy, submetallic, or silky

Identified August 6, 2026More mineral →

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Physical properties

Formation & geological history

Forms as a secondary mineral resulting from the weathering and oxidation of various iron-bearing minerals, often found in gossans, bog iron deposits, and sedimentary iron formations.

Uses & applications

Historically used as a pigment (ochre), a source of iron ore, and occasionally cut and polished for lapidary purposes or collected as mineral specimens.

Geological facts

Limonite is not a single distinct mineral, but rather a mixture of related hydrated iron oxide minerals such as goethite, akaganeite, and lepidocrocite. The yellow-brown streak is its most diagnostic property.

Field identification & locations

Can be identified in the field by its characteristic yellowish-brown to brownish-black streak, earthy texture, and lack of visible cleavage. Commonly found globally wherever iron-rich rocks undergo weathering.

Other mineral specimens

See all

Sandstone (with potential mineral staining/concretions)

Arenite (SiO2 based)

sedimentary

Soil with Mineral Detritus and Quartz Fragments

Regolith / Silicate Mineral Aggregate

sedimentary

Limonite / Goethite (Iron Ore Mineral nodule)

FeO(OH)·nH2O / FeO(OH)

mineral

Septarian Pebble

Septarian nodule / Concretion

sedimentary

Potassium Feldspar (Orthoclase)

Orthoclase (KAlSi3O8)

mineral

Schist

Metamorphic