sedimentary

Fossiliferous limestone

Bioclastic carbonate rock; predominantly calcite (CaCO₃)

AI-generated identification · may be incorrect

Dark gray to black, coarse and irregular, with abundant cream-colored fossil fragments—likely brachiopods, crinoids, or shell debris. Calcite has Mohs hardness 3, vitreous to dull luster, rhombohedral cleavage, and fizzes strongly with dilute hydrochloric acid;…

Identified September 11, 2026More sedimentary →

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Physical properties

Formation & geological history

Forms when marine skeletal debris accumulates, is compacted, and cemented in shallow seaways or reefs. The fossils may be Paleozoic to Mesozoic, but an exact age and locality require stratigraphic or laboratory study.

Uses & applications

Used locally as crushed stone, aggregate, cement or lime feedstock, and as collectible fossil material; attractive polished pieces may be decorative.

Geological facts

The visible ribbed shell-like structure is a fossil, not a mineral crystal. Dark coloration commonly reflects organic matter, pyrite, or other impurities in the carbonate matrix.

Field identification & locations

Identify it by visible fossils embedded in a carbonate matrix and an acid reaction; inspect broken surfaces for shell layering and cleavage. Common in marine sedimentary basins worldwide, especially Paleozoic limestone regions.