mineral

Limonite (Iron Ore)

FeO(OH)·nH2O (Hydrous ferric oxide)

AI-generated identification · may be incorrect

Hardness: 4-5.5 on Mohs scale; Color: Dull yellow, brown, to ochre; Luster: Earthy, dull; Crystal structure: Amorphous/microcrystalline; Cleavage: None; Specific Gravity: 2.7-4.3

Hardness: 4-5
Color: Dull yellow, brown, to ochre
Luster: Earthy, dull

Identified March 21, 2026More mineral →

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Physical properties

Hardness: 4-5.5 on Mohs scale; Color: Dull yellow, brown, to ochre; Luster: Earthy, dull; Crystal structure: Amorphous/microcrystalline; Cleavage: None; Specific Gravity: 2.7-4.3

Formation & geological history

Formed as a secondary material through the oxidation and weathering of other iron-bearing minerals like pyrite, magnetite, and hematite in sedimentary or metamorphic layers.

Uses & applications

Historically used as a common iron ore and as a source of ochre pigment for paints and cosmetics. Currently used in industrial chemical processes and environmental remediation.

Geological facts

Limonite is not a true mineral but a mixture of hydrated iron oxide minerals. It was the primary source of iron for many early civilizations because it is found on the Earth's surface and is easy to smelt.

Field identification & locations

Identify by its distinctive yellowish-brown streak on a porcelain plate and its earthy, rusted appearance. Often found in bog deposits, gossans, or as a coating on other rocks. Common globally in oxidized zones.