sedimentary

Rounded limestone pebble

Limestone, predominantly calcite (CaCO₃)

AI-generated identification · may be incorrect

Cream-colored, dull to earthy luster, fine-grained and rounded; calcite hardness is 3 Mohs, with indistinct cleavage in the mass and specific gravity about 2.7. The small pits may be pores, weathering cavities, or tiny fossil traces.

Identified August 12, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed from compacted and cemented carbonate mud, shell debris, or chemical precipitates, commonly in marine environments; its exact geological age cannot be determined from the photograph. Rounding indicates transport by water or shoreline abrasion.

Uses & applications

Used extensively for cement, aggregate, agricultural lime, building stone, and sculpture; this ordinary pebble has little jewelry use.

Geological facts

Calcite-rich limestone effervesces visibly when a drop of dilute hydrochloric acid or strong vinegar is applied, though vinegar may react slowly. Some limestones preserve abundant marine fossils.

Field identification & locations

Common worldwide in sedimentary basins, riverbeds, beaches, and glacial deposits; identify by its light color, relatively soft surface, and acid reaction. A streak or scratch test should be performed inconspicuously.