mineral
Limonite (Iron Ore)
Hydrated iron(III) oxide-hydroxide (FeO(OH)·nH2O)
AI-generated identification · may be incorrectHardness: 4.0 - 5.5; Color: Yellowish-brown to dark brown; Luster: Dull, earthy; Crystal Structure: Amorphous (lacks definite crystal structure); Streak: Yellow-brown; Specific Gravity: 2.7 - 4.3
- Hardness
- 4
- Color
- Yellowish-brown to dark brown
- Luster
- Dull, earthy
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Physical properties
Hardness: 4.0 - 5.5; Color: Yellowish-brown to dark brown; Luster: Dull, earthy; Crystal Structure: Amorphous (lacks definite crystal structure); Streak: Yellow-brown; Specific Gravity: 2.7 - 4.3
Formation & geological history
Formed usually from the oxidation and hydration of iron-rich sulfide minerals (like pyrite) or as a chemical precipitate in shallow marine or bog environments (bog iron).
Uses & applications
A minor ore of iron; used as a natural earth pigment (yellow ochre) in paints, dyes, and cosmetics. Primarily collected as a secondary mineral or historical iron source.
Geological facts
Limonite is not a true mineral but a mixture of related hydrated iron oxide minerals. It was one of the first pigments used by early humans in cave paintings, such as at Lascaux.
Field identification & locations
Identify by its characteristic yellowish-brown streak on a porcelain plate and its dull, ochre-like appearance. Commonly found in gossans (weathered tops of ore deposits) and sedimentary layers.
