sedimentary

Fossiliferous limestone

Bioclastic carbonate rock, chiefly calcite (CaCO₃), with fossil shells/coral fragments

AI-generated identification · may be incorrect

Usually tan to gray, earthy to dull, and porous, with abundant rounded shell-like fossils and cavities; calcite is Mohs 3, has vitreous luster in crystals, rhombohedral cleavage, and specific gravity about 2.7. Strongly effervesces with dilute hydrochloric acid.

Identified August 29, 2026More sedimentary →

Explore Fossiliferous 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 when marine organisms accumulate, are buried, compacted, and cemented by calcite in shallow seas; the apparent age depends on the fossils and locality, commonly Paleozoic–Cenozoic. Some cavities may represent dissolved shells or later mineral-filled voids.

Uses & applications

Used as crushed stone, aggregate, cement and lime feedstock, dimension stone, and decorative material; fossil-rich pieces are popular inexpensive teaching and display specimens.

Geological facts

The specimen appears especially rich in small gastropod/bivalve or coral fragments, with weathered cavities and possible dark secondary mineral filling. Exact fossil identification requires close examination of cleaned surfaces.

Field identification & locations

Look for pervasive carbonate fossils and acid reaction; distinguish it from fossiliferous dolostone, which reacts weakly when powdered. Common in former shallow-marine sedimentary basins worldwide.