Mineral (Iron Ore)
Limonite (Yellow Ochre)
FeO(OH)·nH2O (Hydrous iron(III) oxide-hydroxide mixture)
Hardness: 4.0-5.5 on Mohs scale; Color: Yellowish-brown to brownish-orange; Luster: Dull, earthy; Crystal Structure: Amorphous or microcrystalline; Cleavage: None; Specific Gravity: 2.7-4.3
- Hardness
- 4
- Color
- Yellowish-brown to brownish-orange
- Luster
- Dull, earthy
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Physical properties
Hardness: 4.0-5.5 on Mohs scale; Color: Yellowish-brown to brownish-orange; Luster: Dull, earthy; Crystal Structure: Amorphous or microcrystalline; Cleavage: None; Specific Gravity: 2.7-4.3
Formation & geological history
Formed as a secondary material through the oxidation or weathering of iron-rich minerals (like pyrite, magnetite, or siderite). It is commonly found in the oxidation zones of ore deposits and as bog iron in marshy environments.
Uses & applications
Historically used as an indispensable source of iron ore. Today, it is primarily used as a natural pigment (yellow ochre) in paints, dyes, and cosmetics. It is also used in the production of iron-rich fertilizers.
Geological facts
Limonite is not a singular mineral but a mixture of hydrated iron oxide minerals, predominantly goethite. It was the primary pigment used in the famous prehistoric cave paintings in Lascaux, France, dating back over 17,000 years.
Field identification & locations
Identify by its characteristic yellowish-brown streak (scratched against unglazed porcelain) and earthy appearance. Found worldwide in weathered rock outcrops and lake beds. Collectors should look for 'pseudomorphs' where limonite has replaced the shape of other crystals like pyrite cubes.
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Limonite (Iron Ore)
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Limonite (Iron Ore/Bog Iron)
Hydrated Iron(III) Oxide-Hydroxide (FeO(OH)·nH2O)
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Limonite / Ironstone Nodule
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Limonite (with Pyrite)
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