sedimentary

Rounded sandstone pebble

Quartz-rich sandstone (commonly arkosic or feldspathic sandstone)

AI-generated identification · may be incorrect

Fine-grained, tan-gray, dull to earthy luster, and rounded from abrasion; individual grains are only faintly visible. Typical hardness is about 6–7 for quartz grains, but the rock can crumble or scratch less consistently depending on cement; no obvious cleavage or crystals are visible.

Identified August 12, 2026More sedimentary →

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Physical properties

Formation & geological history

Lithified sand cemented by silica, calcite, or iron oxides, then rounded by stream or glacial transport. Near 46.7°N, 92.0°W, glacially transported sandstone and related sedimentary erratics are plausible, generally derived from Paleozoic rocks exposed around the Lake Superior region.

Uses & applications

Common sandstone is used as building stone, aggregate, landscaping material, and occasionally for carving or polishing; this small pebble has mainly educational or decorative value.

Geological facts

The smooth shape indicates substantial water, wave, or ice abrasion. A dilute acid test may fizz if calcite-cemented, while a fresh surface typically reveals sand-sized quartz and feldspar grains.

Field identification & locations

Likely identifiable in the field by its gritty texture, muted tan color, and visible or feelable sand grains; it is not possible to distinguish sandstone from some fine-grained quartzite confidently from this photograph alone. Common around glacial deposits, streams, and beaches in northeastern Minnesota.