sedimentary

Fossiliferous limestone (reef or shell-rich limestone)

Bioclastic calcarenite/calcirudite; predominantly calcite (CaCO₃)

AI-generated identification · may be incorrect

Typically Mohs 3, white to gray, earthy to sugary luster, porous and irregularly bedded; visible shell or coral fragments and possible iron-oxide brown staining. Calcite may effervesce vigorously with dilute hydrochloric acid.

Identified September 10, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed when marine shells, corals, and other carbonate debris accumulated, were compacted, and cemented in shallow warm seas; age cannot be determined from the image and may range from Paleozoic to Cenozoic.

Uses & applications

Used as crushed aggregate, cement and lime feedstock, building stone, and decorative specimens; fossil-rich pieces are mainly collected or displayed.

Geological facts

The rounded dark and pale inclusions likely represent fossil fragments or cement-filled cavities rather than igneous crystals. Acid reaction and fossil identification are useful for confirming the diagnosis.

Field identification & locations

Common in former reef, shallow-marine, and coastal environments worldwide, including Florida, the Bahamas, the Mediterranean, and many uplifted marine basins. Test a hidden spot with dilute acid and inspect inclusions with a hand lens.