sedimentary

Rounded sandstone boulder

Quartz-rich sandstone, likely arkosic or lithic sandstone

AI-generated identification · may be incorrect

Tan, fine- to medium-grained, dull earthy luster, and strongly rounded surface from abrasion or weathering. Typical hardness is about 6–7 for quartz grains, with variable porosity and no visible cleavage; exact texture is obscured by the smooth exterior.

Identified August 15, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed when sand accumulated, compacted, and cemented by silica, calcite, or iron oxides, commonly in rivers, beaches, or deserts. Its precise geological age and cement cannot be determined from the photograph.

Uses & applications

Used as landscaping stone, garden ornament, paving material, and occasionally building stone; generally little jewelry value.

Geological facts

The unusually smooth, egg-like shape likely reflects prolonged stream or shoreline transport, or deliberate mechanical tumbling. Color commonly comes from iron staining or weathered feldspar.

Field identification & locations

Look for visible sand grains, layered bedding, weak acid reaction if calcite-cemented, and a gritty texture on a fresh break; quartz-rich sandstone will not scratch easily with a steel knife. Common worldwide, including river gravels and sedimentary basins.