sedimentary

Rounded quartz-rich sandstone cobble

Quartz arenite (sandstone), likely iron-stained

AI-generated identification · may be incorrect

Fine- to medium-grained, pale tan-gray, dull to slightly sandy luster, with rounded water-worn surfaces and rusty iron-oxide staining. Dominantly quartz with possible feldspar and clay cement; hardness approximately 6–7 for quartz grains, with no obvious cleavage.

Identified August 14, 2026More sedimentary →

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Physical properties

Formation & geological history

Lithified sand compacted and cemented in an ancient river, beach, or basin, then exposed and rounded by later stream transport. Its exact geological age cannot be determined from the image.

Uses & applications

Common sandstone is used for aggregate, building stone, paving, and landscaping; this rounded cobble has modest decorative or educational value rather than gemstone value.

Geological facts

The large central feature appears to be a natural fracture or vein filled with lighter cement, not a fossil. Surface rounding and smoothness indicate prolonged abrasion in flowing water or surf.

Field identification & locations

Identify it by gritty texture, visible sand grains, quartz-rich composition, and sedimentary layering or cement veins; sandstone scratches glass only if quartz-rich and cemented. Common in riverbeds, beaches, glacial deposits, and sedimentary outcrops worldwide.