sedimentary
Limonite Boxwork / Iron Ore Concretion
FeO(OH)qnH2O (Hydrated iron oxide)
Hardness: 4.0 - 5.5; Color: Dark brown to yellow-brown; Luster: Dull or earthy; Structure: Amorphous or microcrystalline; Highly porous and irregular shape.
- Hardness
- 4
- Color
- Dark brown to yellow-brown
- Luster
- Dull or earthy
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Physical properties
Hardness: 4.0 - 5.5; Color: Dark brown to yellow-brown; Luster: Dull or earthy; Structure: Amorphous or microcrystalline; Highly porous and irregular shape.
Formation & geological history
Formed through the oxidation and hydration of iron-rich minerals. Often found as a secondary mineral in the oxidation zones of ore deposits or as bog iron in swamps.
Uses & applications
Primary source of iron ore in historical times; currently used as a pigment (ochre) and for mineral collecting.
Geological facts
Limonite is not a single mineral but a mixture of hydrated iron oxide minerals, most commonly goethite. It was historically used to produce brown and yellow paints.
Field identification & locations
Identify by its yellowish-brown streak, lack of magnetism compared to magnetite, and irregular, often hollow or 'bubbly' (botryoidal) texture. Found worldwide in weathered bedrock.
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