sedimentary

Weathered limestone (probable)

Limestone, chiefly calcite (CaCO₃); exact identification is uncertain from the image

AI-generated identification · may be incorrect

Tan, rough, irregular specimen with a dull to slightly earthy luster and no obvious crystals. Calcite has Mohs hardness 3 and rhombohedral cleavage; limestone commonly fizzes with dilute acid, though impurities can mask the reaction.

Identified October 4, 2026More sedimentary →

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Physical properties

Formation & geological history

Forms when carbonate mud, shells, or other calcium-carbonate material accumulates and lithifies, often in marine settings. Its age cannot be determined from appearance alone.

Uses & applications

Limestone is widely used in cement and lime production, aggregate, and building stone; this small, rough piece has little commercial value.

Geological facts

Limestone can preserve fossils, but none are clearly visible here.

Field identification & locations

Look for a relatively soft, calcite-rich rock and test a freshly exposed spot with dilute acid. Limestone occurs worldwide, especially in ancient marine sedimentary formations.