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.
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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.
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