sedimentary

River Cobble (Conglomerate context)

Unconsolidated Fluvial Alluvium (comprised of various lithologies like Quartzite, Granite, or Basalt)

AI-generated identification · may be incorrect

Hardness: variable (typically 6-7 if quartz-rich); Color: shades of tan, grey, and brown; Luster: dull to earthy when dry; Crystal structure: various (clastic texture); Cleavage: none; Shape: sub-rounded to rounded due to water erosion.

Hardness: variable (typically 6-7 if quartz-rich)
Color: shades of tan, grey, and brown
Luster: dull to earthy when dry

Identified April 10, 2026More sedimentary →

Explore River Cobble (Conglomerate context) in the encyclopedia →

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Physical properties

Formation & geological history

Formed through the erosion of upstream bedrock, followed by transportation and rounding in high-energy river environments. These deposits are often Holocene to Pleistocene in age, found in alluvial fans and riverbeds.

Uses & applications

Used primarily in the construction industry as aggregate for concrete, road base, and decorative landscaping. Larger smooth stones are popular in xeriscaping.

Geological facts

The rounded shape of these stones is a result of 'attrition,' where rocks collide with each other in moving water, wearing down sharp edges over thousands of years.

Field identification & locations

Identify in the field by their smooth, 'river-worn' rounded surfaces and presence in layered soil banks (alluvial deposits). Common in mountain valleys and glacial outwash plains.