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.

Fossiliferous Sedimentary Rock

Sedimentary limestone with invertebrate fossil imprint

Sandstone or Siltstone

Arenite (if sandstone)

Quartz pebble

Silicon dioxide (SiO2)

Generic Pebble / Rock Fragment

Lithic fragment / Weathered rock

Sedimentary Sandstone

Arenite (Sedimentary Rock)

Shale (or Mudstone/Siltstone)

Sedimentary Mudrock (SiO2, Al2O3 base with clay minerals)