sedimentary

Chalky limestone fragment

Calcite-rich limestone; predominantly calcium carbonate (CaCO₃)

AI-generated identification · may be incorrect

Soft, white to pale gray, dull and earthy, with irregular fracture; Mohs hardness about 3 and typically reacts vigorously with dilute hydrochloric acid. The fine-grained appearance suggests microcrystalline calcite rather than a visible crystal specimen.

Identified September 22, 2026More sedimentary →

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Physical properties

Formation & geological history

Forms from accumulated carbonate mud, shells, or skeletal material in shallow marine environments; the fragment’s geological age cannot be determined from the image. Commonly associated with sedimentary strata of many ages.

Uses & applications

Used as crushed aggregate, cement and lime feedstock, agricultural soil conditioner, and building stone; this small fragment has negligible commercial or jewelry value.

Geological facts

Calcite limestone may preserve fossils, though none are visible here. Its softness and acid reaction distinguish it from quartz-rich rocks such as chert.

Field identification & locations

Common in limestone regions worldwide, including the United States, Europe, and parts of Asia. Confirm identification by testing a fresh surface with dilute acid and checking that it scratches easily with a steel nail.