sedimentary

Fossiliferous limestone

Bioclastic carbonate rock, chiefly calcite (CaCO₃), containing marine fossil fragments

AI-generated identification · may be incorrect

Typically light gray and weathered, with a dull to subtly crystalline luster; Mohs hardness about 3, poor cleavage, and specific gravity around 2.6–2.7. The visible circular and shell-like forms are likely fossilized crinoid or mollusk fragments in a calcite matrix.

Identified August 21, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed when marine organisms accumulated on an ancient seafloor and their carbonate remains were compacted and cemented. Exact age cannot be determined from the photograph, but similar fossil limestones range from Paleozoic to Cenozoic.

Uses & applications

Used as aggregate, cement and lime feedstock, building stone, and educational or collector specimens; fossil-rich pieces are commonly sold as display stones.

Geological facts

Calcite-rich limestone effervesces strongly with dilute hydrochloric acid or vinegar, especially on a freshly scratched surface. Fossil preservation and texture suggest a marine depositional environment.

Field identification & locations

Identify it by abundant embedded fossil shapes, gray carbonate matrix, and acid reaction; do not confuse it with concrete, which usually has uniform manufactured aggregate. Common worldwide, including marine sedimentary basins in the United States, Europe, and North Africa.