sedimentary

Rounded gray-brown river cobble

Indeterminate lithology; possibly weathered quartzite, chert, or fine-grained sandstone

AI-generated identification · may be incorrect

Hardness likely about 6–7 if quartz-rich; gray-brown color, dull to weakly waxy luster, massive texture, and no visible cleavage or crystals. The smooth, rounded surface indicates abrasion and weathering rather than crystal form.

Identified August 11, 2026More sedimentary →

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Physical properties

Formation & geological history

Likely a naturally transported river or beach cobble shaped by prolonged erosion; its exact geological age and parent rock cannot be determined from the photograph. Fine surface texture may reflect iron staining or weathering rind.

Uses & applications

Primarily a decorative, landscaping, teaching, or collection specimen; no specific industrial or jewelry use can be assigned without identification and testing.

Geological facts

The asymmetrical, polished-looking shape is typical of water-worn clasts. A streak, hardness test, acid test, and fresh break would distinguish quartzite, chert, sandstone, and other possibilities.

Field identification & locations

Common in streambeds, beaches, and glacial deposits. Check whether it scratches glass (quartz-rich), leaves a streak, shows grains under magnification, or reacts with dilute hydrochloric acid (carbonate rock).