sedimentary

Rounded gray river pebble

Likely fine-grained quartz-rich sandstone or siltstone; exact identification requires a fresh surface and tests

AI-generated identification · may be incorrect

Gray-green, dull to weakly satin luster, fine-grained and smoothly water-worn; likely hardness about 5–7 if quartz-rich, with no visible cleavage. Specific gravity is probably about 2.5–2.7.

Identified August 18, 2026More sedimentary →

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Physical properties

Gray-green, dull to weakly satin luster, fine-grained and smoothly water-worn; likely hardness about 5–7 if quartz-rich, with no visible cleavage. Specific gravity is probably about 2.5–2.7.

Formation & geological history

Formed as lithified sediment, then rounded and smoothed by stream or shoreline abrasion. The rock’s depositional age cannot be determined from the photograph.

Uses & applications

Primarily a natural decorative or landscaping stone; occasionally used in teaching collections and lapidary work. Collector value is generally minimal unless locality or composition is unusual.

Geological facts

The rounded form is a transport feature rather than a diagnostic mineral property. Pale speckling may represent quartz grains, feldspar, or weathered cement.

Field identification & locations

Common in riverbeds, glacial deposits, and beaches. Test streak, acid reaction, grain texture, and hardness; a fresh broken face is needed to distinguish sandstone from basalt, altered volcanic rock, or quartzite.