sedimentary

Weathered limestone or calcareous concretion

Calcite-rich carbonate rock; primarily calcium carbonate (CaCO₃), commonly calcite

AI-generated identification · may be incorrect

Pale tan-gray, dull to earthy luster, fine-grained and rounded with irregular layering; Mohs hardness about 3, poor cleavage in massive form, specific gravity roughly 2.3–2.7. The whitish veins and crumbly texture are consistent with calcite-rich material.

Identified August 11, 2026More sedimentary →

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Physical properties

Formation & geological history

Likely formed by accumulation and cementation of carbonate mud or shell debris, or as a carbonate concretion in sediment; age cannot be determined from the photograph. Surface rounding and weathering occurred after formation.

Uses & applications

Crushed limestone is used for aggregate, cement, lime, soil conditioning, and construction stone; this unexceptional specimen has little commercial or jewelry value.

Geological facts

Calcite effervesces visibly with dilute hydrochloric acid or strong vinegar, especially on a freshly scratched surface. Layering may reflect sediment deposition or growth around a concretionary nucleus.

Field identification & locations

Common in marine sedimentary basins worldwide, including the United States, Europe, and parts of Asia. Test a hidden fresh area for fizz, inspect for fossils, and compare hardness with a steel nail or copper coin.