sedimentary
Ironstone Concretion (Nutstone)
Ironstone (with High Limonite/Hematite Content)
AI-generated identification · may be incorrectHardness: 5-6 (Mohs), Color: Dark brown to reddish-orange, Luster: Dull/Earthy, Crystal Structure: Amorphous or Fine-grained, Specific Gravity: 3.0-4.0
Identified More sedimentary →
Explore Ironstone Concretion (Nutstone) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 5-6 (Mohs), Color: Dark brown to reddish-orange, Luster: Dull/Earthy, Crystal Structure: Amorphous or Fine-grained, Specific Gravity: 3.0-4.0
Formation & geological history
Formed by the precipitation of mineral cement (iron oxides) within the spaces between sediment grains, often during the diagenesis of sedimentary rocks in bog or lake environments.
Uses & applications
Historically used as an low-grade iron ore; used today in landscaping and as minor curiosities for rock collectors.
Geological facts
These are sometimes called 'nut stones' or 'omphalos stones' due to their rounded, often pitted shapes. They can sometimes contain a core of a different mineral or even a fossil.
Field identification & locations
Identify by its unusually high weight (density) for its size and its dark rusty color. Often found in areas where sandstone or shale has weathered away.
More like this
Other sedimentary specimens
Fossil-bearing concretion, possibly containing a fossil shell or other organic inclusion
Calcareous concretion; exact fossil and host-rock composition are not identifiable from the image
fossil
Fossiliferous Sedimentary Rock
Sedimentary limestone with invertebrate fossil imprint
fossil
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Sandstone
Arenite
sedimentary
Shale
Shale (clastic sedimentary rock)
sedimentary
Shale (or Mudstone/Siltstone)
Sedimentary Mudrock (SiO2, Al2O3 base with clay minerals)
sedimentary