sedimentary

Fossiliferous limestone

Bioclastic calcitic limestone (predominantly CaCO₃)

AI-generated identification · may be incorrect

Typically gray to tan, fine-grained matrix packed with shell fragments and possible whole bivalves or gastropods; dull to slightly earthy luster, Mohs hardness 3, and weak/no cleavage. Calcite-rich surfaces fizz vigorously with dilute hydrochloric acid.

Identified September 17, 2026More sedimentary →

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Physical properties

Formation & geological history

A marine sedimentary rock formed from accumulated shells and skeletal debris that were compacted and cemented on a shallow seafloor. Its exact age cannot be determined from the image; such beds range from Paleozoic to Cenozoic.

Uses & applications

Used as crushed aggregate, road base, cement and lime feedstock, building stone, and decorative fossil stone; well-preserved pieces may be collected or slabbed.

Geological facts

The visible fossils are bioclasts—remains of marine organisms—rather than crystals. Differential weathering commonly leaves shells protruding from the rock surface.

Field identification & locations

Common in former shallow-marine basins worldwide, including the Alps, Mediterranean region, U.S. Midwest, Gulf Coast, and many coastal limestone formations. Confirm with acid fizz and fossil shell textures; avoid confusing it with fossiliferous dolostone, which reacts weakly.