sedimentary

River Rock

N/A - Generic term for water-smoothed rock

Smooth, rounded, dark gray to black color, fine-grained texture

Identified August 31, 2026More sedimentary →

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Physical properties

Smooth, rounded, dark gray to black color, fine-grained texture

Formed by water erosion in a river, stream, or beach environment over long periods, smoothing rough edges.

Landscaping, decorative stone, construction material

River rocks are not a specific type of geological rock but a description of their shape resulting from water action.

Identified by its smooth, rounded shape and lack of sharp edges, commonly found in riverbeds, streams, and beaches.

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)