mineral

Limonite/Goethite (Iron Ore)

Hydrous ferric oxides (FeO(OH)·nH2O)

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

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

Identified March 29, 2026More mineral →

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Physical properties

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

Formation & geological history

Secondary mineral formed by the oxidation and weathering of primary iron-bearing minerals like pyrite, magnetite, and hematite in sedimentary or hydrothermal environments.

Uses & applications

Historically used as a major source of iron ore and as a natural pigment (brown ochre) for paints and cosmetics.

Geological facts

Limonite is not a true mineral but a mixture of hydrated iron oxide minerals. It was often the source of iron for early bog iron smelting operations.

Field identification & locations

Identify by its characteristic yellowish-brown streak (when rubbed on unglazed porcelain) and lack of magnetism compared to magnetite. Commonly found in gossans (iron-caps) above ore deposits.

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