sedimentary

River Stone (Greywacke)

Greywacke (immature sandstone)

AI-generated identification · may be incorrect

Hardness: 6-7 on Mohs scale; Color: Dull grey to greenish-grey; Luster: Matte/earthy; Texture: Fine to medium-grained; Structure: Compact and dense with some visible light-colored mineral streaks.

Hardness: 6-7 on Mohs scale
Color: Dull grey to greenish-grey
Luster: Matte/earthy

Identified July 5, 2026More sedimentary →

Explore River Stone (Greywacke) in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Hardness: 6-7 on Mohs scale; Color: Dull grey to greenish-grey; Luster: Matte/earthy; Texture: Fine to medium-grained; Structure: Compact and dense with some visible light-colored mineral streaks.

Formation & geological history

Formed by the rapid deposition of poorly sorted sands, silts, and clays in deep marine environments/turbidity currents. Its rounded shape is the result of mechanical weathering and water erosion in a river or beach environment.

Uses & applications

Commonly used as decorative landscaping stone, in construction aggregates, or as base material for roads and drainage systems.

Geological facts

Greywacke is often called 'dirty sandstone' because of its poorly sorted nature and high clay content. It is extremely common in ancient mountain belts and tectonic subduction zones.