sedimentary

Weathered limestone or calcareous sandstone

Calcitic carbonate rock, likely limestone (CaCO₃), possibly slightly dolomitic

AI-generated identification · may be incorrect

Pale gray-beige, dull and earthy, fine-grained, strongly weathered, with irregular fracture and no visible crystal faces. Hardness about 3 if calcitic; it should effervesce noticeably with dilute hydrochloric acid or vinegar, though weathering may weaken the reaction.

Identified September 14, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed from compacted carbonate mud or cemented carbonate-rich sediment, commonly in shallow marine environments; exact age cannot be determined from the photograph. The rounded surfaces reflect later erosion and weathering.

Uses & applications

Common limestone is used for aggregate, cement, lime, road base, and building stone; attractive pieces may be collected, but this specimen appears low-grade and non-gem quality.

Geological facts

The surface texture is consistent with weathered sedimentary rock rather than a crystalline igneous rock. No diagnostic fossil is clearly visible, although fossils could be concealed by weathering.

Field identification & locations

A plausible identification for central Iran near 33.5°N, 51.9°E, where extensive sedimentary carbonate formations occur. Confirm by acid testing, examining a fresh break for grains or fossils, and checking whether it scratches with a steel knife.