sedimentary
Limonite Concretion
Goethite/Limonite concretion (FeO(OH)·nH2O)
Hardness: 4-5.5 on the Mohs scale, Color: yellowish-brown, dark brown, or reddish-brown, Luster: earthy to submetallic, Crystal structure: amorphous or microcrystalline (pseudomorphic after pyrite or marcasite), Cleavage: none, Specific gravity: 2.7-4.3
- Hardness
- 4-5
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: 4-5.5 on the Mohs scale, Color: yellowish-brown, dark brown, or reddish-brown, Luster: earthy to submetallic, Crystal structure: amorphous or microcrystalline (pseudomorphic after pyrite or marcasite), Cleavage: none, Specific gravity: 2.7-4.3
Formation & geological history
Formed through the low-temperature chemical precipitation of iron oxides and hydroxides in sedimentary environments, often replacing precursor minerals like pyrite or accumulating in sandstone pores through groundwater movement.
Uses & applications
Used historically as a pigment (ochre), as an iron ore, and commonly collected as geological specimens or curiosity stones.
Geological facts
Limonite is not a true distinct mineral species, but rather a field term for a mixture of hydrated iron oxide minerals, predominantly goethite.
Field identification & locations
Easily identified by its characteristic yellowish-brown streak, concentric banding or boxwork structure, and rust-like appearance. Commonly found worldwide in weathering zones of iron-bearing rocks.
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
Banded Siltstone / Mudstone Pebble
Siltstone / Argillite
sedimentary
Shale (or Mudstone/Siltstone)
Sedimentary Mudrock (SiO2, Al2O3 base with clay minerals)
sedimentary
Shale
Shale (clastic sedimentary rock)
sedimentary