sedimentary

Gray River Pebble (Limestone or Greywacke)

Sedimentary Pebble (Calcite / Quartz composition)

AI-generated identification · may be incorrect

Hardness: 3-7 on Mohs scale depending on exact composition; Color: Medium gray with subtle lighter veins and flecks; Luster: Matte to dull; Cleavage: None visible in smoothed pebble state; Texture: Smooth, water-worn exterior.

Hardness: 3-7 on Mohs scale depending on exact composition
Color: Medium gray with subtle lighter veins and flecks
Luster: Matte to dull

Identified July 27, 2026More sedimentary →

Explore Gray River Pebble (Limestone or Greywacke) in the encyclopedia →

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Physical properties

Formation & geological history

Formed from sedimentary rock layers, such as limestone or fine-grained sandstone, that were broken down and rounded over time through transport by river currents or ocean waves.

Uses & applications

Commonly used as decorative garden stone, landscaping aggregate, aquarium gravel, or aquascaping materials.

Geological facts

Water-worn river pebbles get their smooth, rounded shapes through mechanical weathering as they tumble along riverbeds against other stones and gravel over thousands of years.

Field identification & locations

Can be identified in the field by its rounded, smooth cobble or pebble shape and uniform gray coloration. Extremely common along river banks, lake shores, and beaches worldwide.