sedimentary

Weathered limestone or calcareous concretion

Calcite-rich carbonate rock; primarily CaCO₃

AI-generated identification · may be incorrect

Pale tan, fine-grained, dull to earthy luster, irregular polygonal weathering cracks, and no visible crystals; calcite hardness is Mohs 3 and it should effervesce with dilute hydrochloric acid or strong vinegar if fresh. Exact identification is limited without a fresh surface, acid test, or magnification.

Identified September 15, 2026More sedimentary →

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Physical properties

Formation & geological history

Likely formed from accumulated marine or freshwater carbonate mud, shell debris, or cemented carbonate sediment, then exposed and weathered; age cannot be determined from the image. The dark cracks may reflect shrinkage, mineral-filled fractures, or surface weathering.

Uses & applications

Common limestone is used for cement, aggregate, lime, soil conditioning, and building stone; this unremarkable specimen has little commercial or jewelry value.

Geological facts

Limestone commonly contains microscopic fossils and can develop distinctive solution cracks, stylolites, or hard calcareous crusts during weathering.

Field identification & locations

Look for fizzing in dilute acid, low hardness, pale powder, and possible fossils or calcite veins; common worldwide in sedimentary basins. It could also be a weathered dolostone, which fizzes weakly unless powdered.