mineral
Limonite (Yellow Ochre)
Hydrated Iron Oxide (FeO(OH)·nH2O)
Hardness: 4-5.5 (variable, often softer when earthy), Color: Ochre-yellow to yellowish-brown, Luster: Dull to earthy, Crystal Structure: Amorphous or microcrystalline, Cleavage: None, Streak: Yellowish-brown
- Hardness
- 4-5
- Streak
- Yellowish-brown
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Physical properties
Hardness: 4-5.5 (variable, often softer when earthy), Color: Ochre-yellow to yellowish-brown, Luster: Dull to earthy, Crystal Structure: Amorphous or microcrystalline, Cleavage: None, Streak: Yellowish-brown
Formation & geological history
Formed as a secondary mineral through the weathering and oxidation of iron-bearing minerals such as pyrite, marcasite, magnetite, and siderite in near-surface oxidized zones.
Uses & applications
Historically and currently used as a natural pigment (yellow ochre), as a minor ore of iron, and occasionally as a soil conditioner or mineral specimen.
Geological facts
Limonite is not a true mineral in the strict sense, but a mixture of hydrated iron oxide minerals, predominantly goethite along with lepidocrocite and jarosite. It was one of the earliest pigments used by humans in cave paintings.
Field identification & locations
Identified by its distinctive yellowish-brown color, earthy texture, and characteristic yellow-brown streak. Commonly found in oxidized zones of iron ore deposits, soils, and weathered iron-rich rocks worldwide.
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