sedimentary

Weathered sandstone or siltstone cobble

Clastic sedimentary rock, likely quartz–feldspar sandstone/siltstone

AI-generated identification · may be incorrect

Gray-brown, fine-grained, dull to earthy luster, with thin rusty-brown staining or bedding/fracture lines. Likely hardness about 5–7 for grains, though the rock may crumble locally; cleavage absent and density roughly 2.2–2.7 g/cm³.

Identified September 3, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed when sand- or silt-sized sediments were deposited, compacted, and cemented, probably millions to hundreds of millions of years ago; surface weathering produced the muted color and iron staining.

Uses & applications

Common sandstone is used for building stone, paving, aggregate, and landscaping; an ordinary cobble has little commercial or jewelry value.

Geological facts

The image shows a rounded, weathered natural stone rather than a crystal or polished gemstone. Its broad curved line may be bedding, a healed fracture, or weathering—not enough detail is visible to identify a fossil.

Field identification & locations

Likely found in stream beds, beaches, glacial deposits, and sedimentary outcrops. Check for visible grains, layering, acid reaction, and whether a steel knife scratches it; a hand lens and fresh broken surface would improve identification.