sedimentary
Limonite Geode / Ironstone Concretion
Hydrated Iron Oxide (FeO(OH)·nH2O)
Hardness 4-5.5 on Mohs scale, earthy to submetallic luster, rusty orange-brown to dark brown exterior and interior, amorphous/microcrystalline structure, dense and heavy, earthy fracture.
Identified More sedimentary →
Explore Limonite Geode / Ironstone 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 Mohs scale, earthy to submetallic luster, rusty orange-brown to dark brown exterior and interior, amorphous/microcrystalline structure, dense and heavy, earthy fracture.
Formation & geological history
Formed by the precipitation of iron oxide minerals from aqueous solutions around a nucleus or within cavities in sedimentary rocks, creating a hollow or secondary mineral-filled concretion over millions of years.
Uses & applications
Primarily collected as geological curiosities and mineral specimens; historically used as a minor iron ore source and mineral pigment (ochre).
Geological facts
Ironstone geodes are often colloquially referred to as 'rattle stones' or 'etites' when a small loose piece inside creates a rattling sound when shaken. Historically, they were believed to have magical or medicinal properties.
Field identification & locations
Identified by its distinctive spherical or nodular form, thick rusty crust, reddish-brown streak, and hollow interior filled with iron-rich earthy masses or small crystals. Commonly found in sedimentary deposits in the US Midwest, Europe, and Australia.
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
Shale (clastic sedimentary rock)
sedimentary
Shale
Sedimentary Shale
sedimentary