sedimentary

Porous limestone

Calcite-rich limestone (CaCO₃), possibly fossiliferous or chalky limestone

AI-generated identification · may be incorrect

White to pale gray, dull-to-earthy luster, fine-grained and highly porous; calcite hardness is about Mohs 3, with indistinct cleavage in the rock. It should effervesce strongly with dilute hydrochloric acid or vinegar, though the rough surface may obscure the reaction.

Identified August 19, 2026More sedimentary →

Explore Porous limestone in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Formation & geological history

Forms from accumulated marine carbonate mud, shell fragments, or reef debris, commonly during shallow-marine deposition and later lithification; its precise geological age cannot be determined from the image.

Uses & applications

Used for cement and lime production, aggregate, soil treatment, building stone, and decorative pieces; this specimen has modest collector value unless it contains identifiable fossils or unusual textures.

Geological facts

The pale, cellular appearance may indicate chalk, coquina, or weathered fossiliferous limestone rather than a single mineral crystal. Limestone is one of Earth’s major carbon reservoirs and dissolves readily in acidic groundwater.

Field identification & locations

Common worldwide, especially in former shallow seas; major occurrences include the Caribbean, Mediterranean, England, Indiana, and many U.S. regions. Confirm identification by acid fizz, low hardness, and lack of reaction to a magnet.