metamorphic
River Cobble (Quartzite / Fine-grained Sandstone)
Quartzite / Meta-sandstone (primarily SiO2)
AI-generated identification · may be incorrectHardness 6.5–7 Mohs, dull to earthy luster, rounded oblong shape with a brownish-tan weathering rind, specific gravity around 2.6–2.7.
Identified More metamorphic →
Explore River Cobble (Quartzite / Fine-grained Sandstone) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness 6.5–7 Mohs, dull to earthy luster, rounded oblong shape with a brownish-tan weathering rind, specific gravity around 2.6–2.7.
Formation & geological history
Formed from quartz-rich sandstone subjected to regional metamorphism, subsequently shaped and rounded through long-distance fluvial or glacial abrasion.
Uses & applications
Commonly used in landscaping, road aggregate, construction ballast, and decorative garden rockery.
Geological facts
Naturally rounded river rocks like this cobble acquire their smooth, elongated shape through tumbling along riverbeds over thousands of years.
Field identification & locations
Identifiable by its smooth, water-worn exterior, high hardness that easily scratches glass, and fine-grained siliceous texture; found globally in gravel deposits and riverbeds.
More like this
