mineral

Limonite Concretion

Hydrated Iron Oxide Hydroxide, FeO(OH)nH2O

Hardness of 4 to 5.5 on the Mohs scale, yellowish-brown to dark brown color, earthy to submetallic luster, amorphous crystal structure.

Identified October 23, 2026More mineral →

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Physical properties

Hardness of 4 to 5.5 on the Mohs scale, yellowish-brown to dark brown color, earthy to submetallic luster, amorphous crystal structure.

Forms through the oxidation and weathering of primary iron-bearing minerals in sedimentary, igneous, and metamorphic environments.

Used historically as a pigment (ochre) and minor iron ore; valued by collectors for unusual botryoidal or concretionary shapes.

Limonite is not a distinct mineral species, but rather a natural mixture of related iron oxide minerals like goethite and lepidocrocite.

Identified by its characteristic yellowish-brown streak and irregular concretionary form; commonly found in oxidized iron deposit zones worldwide.

Gneiss or Schist

Gneiss or Mica Schist with Garnet

Limonite

FeO(OH)•nH2O

Sandstone (with potential mineral staining/concretions)

Arenite (SiO2 based)

Feldspar

Feldspar Group (Tectosilicate, e.g., KAlSi3O8)

Tumbled granite

Granite, a coarse-grained felsic intrusive igneous rock

Pegmatite with Tourmaline and Quartz

Igneous Pegmatite