Mineral Guide · Material
Limonite is a natural iron-oxide and hydroxide mixture recognised by yellow-brown earthy colour, ochre textures and its role in weathered ore deposits.
Limonite is a natural iron-oxide and hydroxide mixture recognised by yellow-brown earthy colour, ochre textures and its role in weathered ore deposits.
Reference formula: No single formula applies because this is a natural mixture or amorphous material.. Limonite is not a single crystalline mineral species and has no fixed formula or unique crystal lattice. It commonly contains variable goethite, lepidocrocite, hematite and poorly crystalline iron oxyhydroxides; this page therefore describes it as a natural material rather than assigning an artificial structure. Limonite is classified with a mineral-like material rather than one mineral class and has a not applicable because the material has no single crystal lattice crystal system. Typical hardness is 4–5.5 on the Mohs scale and specific gravity is approximately 2.7–4.3.
Typical colours include yellow, brown, red-brown, black. The usual earthy, massive, botryoidal habit and earthy, dull, sub-metallic lustre help describe a specimen, but colour alone is not diagnostic.
Limonite forms in or is associated with weathering and oxidation of iron-bearing rocks, hydrothermal deposits, soils and bog iron environments. Important documented localities include worldwide, including major occurrences in Europe, North America, South America, Africa and Australia.
Limonite is one of the most useful natural materials for understanding weathering: golden ochre, brown crusts and iron-rich cavity fillings reveal how rocks respond to oxygen and water. It is a strong reference piece when the mixture is labelled honestly and its locality is known.
Avoid dust, aggressive acids and waterlogging; retain the locality because appearance alone cannot determine the exact iron-mineral mixture.
Reviewed by NotOnlyRocks Editorial Team
Last reviewed: 28 August 2026
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