sedimentary

Rounded sandstone or siltstone cobble

Clastic sedimentary rock, likely quartz-rich sandstone (possibly fine-grained siltstone)

AI-generated identification · may be incorrect

Light gray-brown, dull earthy luster, very fine sand-sized grains, rounded water-worn shape, and a thin surface fracture or scratch. Likely Mohs hardness about 5–7 depending on quartz content; no visible cleavage or crystal faces.

Identified September 6, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed from compacted and cemented sediment, then rounded by stream or river transport. The reported northern Kentucky location commonly exposes Ordovician sedimentary rocks, including shale, limestone, and sandstone, generally about 445–485 million years old.

Uses & applications

Mostly a natural cobble or specimen; sandstone is used locally for aggregate, building stone, and landscaping. This piece has little commercial value unless it has unusual markings or provenance.

Geological facts

The image cannot distinguish sandstone confidently from fine-grained siltstone or weathered limestone. The uniform granular texture favors sandstone/siltstone over a crystalline igneous rock.

Field identification & locations

Check with a hand lens: visible sand grains and a gritty feel support sandstone; a smooth, powdery texture suggests siltstone. Vinegar fizz would indicate carbonate cement or limestone, while a steel nail should not easily scratch quartz-rich sandstone.