sedimentary

River Stone

Water-worn lithic fragment

Hardness varies from 3 to 7 depending on mineral composition, typically smooth and rounded due to water action with a dull to vitreous luster.

Identified November 7, 2026More sedimentary →

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Physical properties

Hardness varies from 3 to 7 depending on mineral composition, typically smooth and rounded due to water action with a dull to vitreous luster.

Formed through mechanical weathering, transportation, and fluvial abrasion of parent rocks in riverbeds over thousands to millions of years.

Widely used in landscaping, garden decoration, aquascaping, and massage therapy.

River stones are shaped by tumbling against other rocks in fast-flowing water, which naturally polishes their surfaces.

Easily identified by their smooth, rounded contours and lack of sharp edges, commonly found along riverbanks and dry streambeds.

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)