sedimentary

Weathered limestone or calcareous sandstone

Calcite-dominated carbonate rock (CaCO₃), possibly fossiliferous limestone

AI-generated identification · may be incorrect

Gray-tan, fine to medium grained, dull earthy luster with porous, solution-weathered surfaces; calcite hardness ~3 Mohs, typically massive with no obvious cleavage in the specimen. The pale areas may be recrystallized calcite or weathered fossil material.

Identified August 28, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed from accumulated marine carbonate mud, shell debris, or calcareous sediment later lithified; likely Phanerozoic in age, though the exact age cannot be determined visually. Surface pitting reflects dissolution by mildly acidic groundwater or weathering.

Uses & applications

Common limestone is used for aggregate, cement, lime, dimension stone, and soil treatment; attractive pieces may be collected or used decoratively. This specimen appears primarily of modest geological interest rather than gem value.

Geological facts

A drop of dilute hydrochloric acid or vinegar should produce visible fizz if calcite-rich, especially on a freshly scratched surface. The irregular cavities may represent dissolved fossils, shell fragments, or weathered carbonate cement.

Field identification & locations

Common in marine sedimentary terrains worldwide, including coastal zones and limestone belts. Confirm with acid effervescence, a scratch test against a copper coin or knife, and inspection for fossil textures; the image alone cannot distinguish limestone confidently from calcareous sandstone.