sedimentary

River Pebble (Graywacke/Sandstone)

Lithic Sandstone

AI-generated identification · may be incorrect

Hardness: 6-7 on Mohs scale; Color: Dull gray to grayish-green with orange/brown iron oxidation; Luster: Matte; Crystal structure: Clastic (grainy texture); Cleavage: None

Hardness: 6-7 on Mohs scale
Color: Dull gray to grayish-green with orange/brown iron oxidation
Luster: Matte

Identified July 1, 2026More sedimentary →

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Physical properties

Hardness: 6-7 on Mohs scale; Color: Dull gray to grayish-green with orange/brown iron oxidation; Luster: Matte; Crystal structure: Clastic (grainy texture); Cleavage: None

Formation & geological history

Formed through the accumulation and lithification of sand, rock fragments, and clay minerals. The rounded shape indicates long-term transport and erosion in a river or lacustrine environment.

Uses & applications

Primarily used in construction as aggregate, landscaping, or as garden stones. Smooth pebbles are often used in decorative zen gardens or as painting stones.

Geological facts

The orange-brown staining on the surface is likely limonite or goethite, which forms when iron-bearing minerals inside the rock react with oxygen and water (rusting).

Field identification & locations

Commonly found in riverbeds, glacial deposits, and beaches. Identify it by its grainy texture, rounded edges, and lack of visible crystals or fossils.