sedimentary

Iron-rich rock or Concretion

Ironstone or Limonite concretion

Hardness varies (limonite is 4-5.5), reddish-brown to rust color, dull to earthy luster, massive or concretionary structure.

Identified August 20, 2026More sedimentary →

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Physical properties

Hardness varies (limonite is 4-5.5), reddish-brown to rust color, dull to earthy luster, massive or concretionary structure.

Forms through chemical precipitation of iron oxides in sedimentary environments or as a weathering product of iron-bearing minerals.

Historically used as low-grade iron ore or pigment; commonly collected for educational purposes.

These concretions can sometimes form around a central nucleus, like a fossil or a grain of sand.

Identified by its rusty color, relatively high density for its size, and earthy appearance; commonly found in sedimentary rock formations and soils.

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

Fossiliferous Sedimentary Rock

Sedimentary limestone with invertebrate fossil imprint

Sandstone or Siltstone

Arenite (if sandstone)

Sandstone

Arenite

Shale

Shale (clastic sedimentary rock)

Shale (or Mudstone/Siltstone)

Sedimentary Mudrock (SiO2, Al2O3 base with clay minerals)