sedimentary

River Pebble (Granite / Sandstone Cobble)

Stream-rounded Rock Pebble

AI-generated identification · may be incorrect

Hardness: 6-7 on Mohs scale (quartz/feldspar dominant); Color: Tan, beige, grey, and speckled buff; Luster: Dull to sub-vitreous; Texture: Fine to medium-grained, smooth rounded surface from aqueous erosion; Specific Gravity: Approximately 2.5 - 2.7.

Hardness: 6-7 on Mohs scale (quartz/feldspar dominant)
Color: Tan, beige, grey, and speckled buff
Luster: Dull to sub-vitreous

Identified July 26, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through mechanical weathering and stream transport. Pre-existing granite, quartzite, or coarse sandstone fragments are eroded and continuously tumbled along riverbeds or shorelines, smoothing sharp edges into a rounded cobble.

Uses & applications

Landscaping, decorative garden accents, aquarium gravel, construction aggregate, and tactile rock painting or polished crafts.

Geological facts

Smooth river stones are natural indicators of ancient or active water flow. The process of naturally rounding a pebble can take hundreds to thousands of years of constant water action.

Field identification & locations

Identified by its well-rounded spherical or ovoid shape, fine gritty texture, and lack of sharp edges. Commonly found in riverbeds, glacial till, stream deposits, and ocean beaches worldwide.