sedimentary
River Pebbles and Cobbles
Polymictic Gravel / Water-worn Lithic Fragments
Mohs hardness varies from 3 to 7 depending on mineral composition (quartz, quartzite, limestone); colors range from gray, tan, brown to reddish; dull to sub-vitreous luster; smooth, rounded texture due to water abrasion.
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Physical properties
Mohs hardness varies from 3 to 7 depending on mineral composition (quartz, quartzite, limestone); colors range from gray, tan, brown to reddish; dull to sub-vitreous luster; smooth, rounded texture due to water abrasion.
Formation & geological history
Formed through the mechanical weathering and erosion of parent rocks, followed by long-distance transport and tumbling by water in rivers, streams, or coastal beaches over geological timescales.
Uses & applications
Used extensively in landscaping, garden decoration, aquariums, construction aggregate, and pathways.
Geological facts
The rounding of these rocks is caused by 'attrition', where rocks collide with each other and the riverbed as they are transported downstream by moving water.
Field identification & locations
Found abundantly in riverbeds, lake shores, and beaches worldwide. Excellent indicators of past and present hydrological activity in geology.
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