mineral
Limonite (Ironstone)
Goethite/Limonite (Hydrated iron(III) oxide-hydroxide)
AI-generated identification · may be incorrectHardness: 4 to 5.5 on Mohs scale; Color: Yellowish-brown to dark brown or black; Luster: Dull, earthy, or submetallic; Crystal Structure: Amorphous or microcrystalline; Streak: Yellow-brown.
- Hardness
- 4 to 5
- Color
- Yellowish-brown to dark brown or black
- Luster
- Dull, earthy, or submetallic
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Physical properties
Hardness: 4 to 5.5 on Mohs scale; Color: Yellowish-brown to dark brown or black; Luster: Dull, earthy, or submetallic; Crystal Structure: Amorphous or microcrystalline; Streak: Yellow-brown.
Formation & geological history
Formed usually by the oxidation and hydration of iron-rich mineral deposits (like pyrite) in the weathering zone. It is a secondary mineral found in sedimentary beds and bog iron deposits.
Uses & applications
Historically used as an iron ore; currently used as a pigment in paints (yellow ochre) and as a low-value collector specimen.
Geological facts
Limonite is not a true mineral but a mixture of hydrated iron oxides. It was once the primary source of iron for early civilizations and was used by prehistoric humans as an art pigment.
Field identification & locations
Identify by its characteristic yellowish-brown streak on a porcelain plate and its earthy appearance. Commonly found in gossans (weathered tops of ore deposits) or as bog iron.
