sedimentary

Weathered limestone

Calcite-rich limestone (CaCO₃), possibly fossiliferous

AI-generated identification · may be incorrect

Pale tan-gray, dull to earthy luster, fine-grained and porous with irregular fractures; calcite hardness Mohs 3, non-cleavable as a rock, specific gravity about 2.5–2.7. Effervesces strongly with dilute hydrochloric acid or vinegar, especially on a freshly scratched surface.

Identified September 5, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed from compacted and cemented carbonate mud or shell debris in a marine or freshwater setting; the specimen’s age cannot be determined from the photograph and may range from Paleozoic to Cenozoic. Surface dissolution and weathering produced its rounded, pitted appearance.

Uses & applications

Used as crushed aggregate, cement and lime feedstock, building stone, and landscaping material; attractive fossiliferous pieces are collected but this specimen appears common and unpolished.

Geological facts

Limestone is dominated by calcite and can be altered into marble by heat and pressure. Its cavities may reflect dissolved fossils, shells, or natural weathering.

Field identification & locations

Identify by its light color, relatively soft surface, and acid reaction; a steel nail may scratch it, while quartz will not. Common worldwide in former shallow-sea basins, including the United States, Europe, and the Caribbean.