sedimentary

River Rock

Siliceous rock fragment

Hardness 7 on Mohs scale, brown to gray color, dull to vitreous luster, amorphous crystal structure, smooth rounded shape.

Identified November 8, 2026More sedimentary →

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Physical properties

Hardness 7 on Mohs scale, brown to gray color, dull to vitreous luster, amorphous crystal structure, smooth rounded shape.

Formed through mechanical weathering and aqueous erosion of parent rocks over thousands to millions of years in riverbeds.

Used in landscaping, decorative ground cover, construction aggregate, and garden pathways.

River rocks are continuously smoothed by waterborne abrasion and sediment friction in active fluvial environments.

Found abundantly in and around riverbeds, streams, and beaches worldwide. Identify by its smooth, water-worn texture.

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)