sedimentary

Fossiliferous limestone (coral or shell-fragment limestone)

Bioclastic limestone, predominantly calcite (CaCO₃)

AI-generated identification · may be incorrect

Gray-brown, rounded and weathered, with visible cellular or shell-like fossil textures; typically Mohs 3, dull to weakly crystalline, and may fizz with dilute hydrochloric acid. Cleavage is poor in the rock, though calcite crystals have perfect rhombohedral cleavage; specific gravity is about 2.5–2.7.

Identified August 31, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed when marine skeletal material—possibly coral, bryozoans, or shell fragments—accumulated, compacted, and cemented on a shallow seafloor. Its exact age cannot be determined from the photograph and may range from Paleozoic to recent geological deposits.

Uses & applications

Used as crushed aggregate, cement and lime feedstock, building stone, and decorative material; attractive fossil pieces are collected, though this specimen appears common.

Geological facts

The honeycomb-like pattern may represent colonial coral or other carbonate fossils rather than mineral crystals. Acid effervescence is a useful confirmation of calcite-rich limestone.

Field identification & locations

Common in former shallow-marine regions worldwide, including limestone coasts and uplifted reef deposits. Inspect the pattern with a hand lens, test a hidden spot with dilute acid, and avoid confusing it with vesicular volcanic rock.