sedimentary
Ironstone Concretion / Limonite Node
Goethite and Limonite (FeO(OH) nH2O)
Hardness: 5-5.5 (variable); Color: Yellowish-brown to dark brown; Luster: Dull/Earthy; Structure: Amorphous or microcrystalline; Highly dense and often features a rusted, weathered exterior crust.
- Hardness
- 5-5
- Color
- Yellowish-brown to dark brown
- Luster
- Dull/Earthy
Identified More sedimentary →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 5-5.5 (variable); Color: Yellowish-brown to dark brown; Luster: Dull/Earthy; Structure: Amorphous or microcrystalline; Highly dense and often features a rusted, weathered exterior crust.
Formation & geological history
Formed by the precipitation of iron-bearing minerals around a nucleus (such as organic matter) within sedimentary layers. Often associated with Cretaceous or Tertiary sandstones and shales where groundwater is rich in iron.
Uses & applications
Historically used as an iron ore; currently used as garden specimen, geological study tool, and sometimes as a pigment for natural paints.
Geological facts
These are often mistaken for meteorites by amateur collectors due to their heavy weight and dark, weathered appearance. Some hollow versions are known as 'rattle stones' because they contain a loose pebble or sand inside.
Field identification & locations
Identify in the field by its high density relative to size, yellow-brown streak on porcelain, and characteristic 'rust' appearance. Found worldwide in stream beds and eroding cliffsides.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Sandstone Grain
Clastic Sedimentary Rock Grain (SiO2 dominated)
sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary
Sandstone
Arenite
sedimentary