Igneous or Sedimentary (water-worn)
River Rock (likely Basalt or Greywacke)
Basalt or Lithic Sandstone
Hardness: 5-7, Color: Gray/dark gray, Luster: Dull to slightly waxy in spots, Structure: Fine-grained, rounded by water action.
Identified More igneous or sedimentary (water-worn) →
Explore River Rock (likely Basalt or Greywacke) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 5-7, Color: Gray/dark gray, Luster: Dull to slightly waxy in spots, Structure: Fine-grained, rounded by water action.
Formation & geological history
Formed either from rapidly cooling lava (basalt) or sedimentary processes (greywacke), subsequently weathered and rounded by fluvial (river) or coastal action.
Uses & applications
Commonly used in landscaping, construction aggregate, and hardscaping.
Geological facts
River rocks are not a specific geological type but rather any rock that has been smoothed and rounded by the action of moving water.
Field identification & locations
Identified by its smooth, rounded shape and lack of sharp edges, typically found in riverbeds and on beaches.
More like this
Other igneous or sedimentary (water-worn) specimens
Quartz Pebble
Crystalline Silicon Dioxide (SiO2)
mineral
Magnetite / Ironstone Pebble
Magnetite (Fe3O4)
mineral
Quartz (Pale Rose or Milky Variety)
Silicon Dioxide (SiO2)
mineral
Quartz or possibly Jasper/Chert. Looks like a tumbled or water-worn stone.
SiO2 (Silicon Dioxide)
Mineral or Sedimentary (if chert)
Chalcedony (Agate and Carnelian varieties)
Silicon Dioxide (SiO2)
mineral
Greenstone / Glauconitic Siltstone
Metabasalt or Glauconite-rich Sedimentary Rock
metamorphic or sedimentary