Limonite

Limonite is a yellow-brown iron-oxide material, usually a mixture of hydrated iron oxides rather than a distinct mineral species. It commonly forms through the weathering of iron-bearing minerals.

Goethite: Goethite is an iron oxyhydroxide mineral with the formula α-FeO(OH). It is commonly a major crystalline component of material identified as limonite.
Chemical weathering: Chemical weathering alters rocks and minerals through reactions with water, gases, and dissolved substances. It transforms iron-bearing minerals into the hydrated iron oxides associated with limonite.
Yellow ochre: Yellow ochre is an earthy pigment whose yellow color comes mainly from iron oxyhydroxides such as goethite. Limonite-rich earth has long supplied the iron-bearing colorant used as yellow ochre.
Hematite: Hematite is a crystalline iron(III) oxide mineral with the formula Fe₂O₃. Unlike limonite, it is a distinct mineral species with a defined composition.
Lepidocrocite: Lepidocrocite is a red-orange iron oxyhydroxide mineral with the formula γ-FeO(OH). It is one possible iron oxyhydroxide constituent in limonitic mixtures.
Laterite: Laterite is iron- and aluminum-rich soil or rock formed by intense leaching in warm, wet climates. Limonitic iron oxides can accumulate in lateritic profiles as soluble components are leached away.
Iron ore: Iron ore is rock or mineral material mined as a source of metallic iron. Some limonitic deposits have been mined as iron ore despite their variable composition.
Magnetite: Magnetite is a crystalline iron oxide mineral with the formula Fe₃O₄ and strong magnetic properties. Its fixed mineral identity and magnetic behavior contrast with limonite’s variable mixtures.
Ferrihydrite: Ferrihydrite is a poorly crystalline, hydrated ferric iron oxide formed in soils and waters. Its low crystallinity helps explain why limonite can be compositionally variable.
Gossan: A gossan is an oxidized, iron-rich zone formed near the surface above a sulfide ore deposit. Its rusty cap may contain abundant limonite produced by sulfide weathering.

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