sedimentary
Limonite Concretion
Limonite (Hydrated iron oxide) FeO(OH)·nH2O
Hardness: 4.0-5.5; Color: Dark brown to yellowish-brown; Luster: Dull or earthy; Texture: Characterized by small circular pits or a botryoidal (grape-like) surface; Specific Gravity: 2.7-4.3.
- Hardness
- 4
- Color
- Dark brown to yellowish-brown
- Luster
- Dull or earthy
Identified More sedimentary →
Explore Limonite Concretion in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 4.0-5.5; Color: Dark brown to yellowish-brown; Luster: Dull or earthy; Texture: Characterized by small circular pits or a botryoidal (grape-like) surface; Specific Gravity: 2.7-4.3.
Formation & geological history
Formed by the precipitation of iron oxides in sedimentary environments, often found in soil or rock cavities where groundwater has concentrated minerals over thousands to millions of years.
Uses & applications
Historically used as a low-grade iron ore (ochre); today primarily used as a pigment in paints and as mineral specimens for education.
Geological facts
Limonite is not a single mineral but a mixture of hydrated iron oxide minerals, mostly goethite. The pitted appearance is often caused by the weathering of softer inclusions within the nodule.
Field identification & locations
Identify in the field by its high density relative to other stones and its rusty-brown streak when rubbed against tile. Often found in wetlands or areas with historic iron-rich runoff.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Sedimentary Sandstone
Arenite (Sedimentary Rock)
sedimentary
Fossiliferous Concretion
Septarian Concretion containing Brachiopods/Crinoids
fossil
Shale
Shale (clastic sedimentary rock)
sedimentary
Brown Sandstone (River Rock)
Arenite
sedimentary
Shale
Argillaceous sedimentary rock
sedimentary