sedimentary

Fossiliferous limestone

Bioclastic limestone, commonly crinoidal or shelly limestone (calcite, CaCO₃)

AI-generated identification · may be incorrect

Brown, fine- to medium-grained carbonate rock containing abundant pale fossil fragments and possible shell/crinoid sections; polished surface has a dull to waxy luster. Calcite hardness is 3 Mohs, with low-to-moderate density and vigorous effervescence in dilute hydrochloric acid.

Identified September 14, 2026More sedimentary →

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Physical properties

Formation & geological history

Forms when marine shells, crinoids, and other skeletal debris accumulate, are compacted, and cemented on shallow seafloors; the exact geologic age cannot be determined from the image and may range from Paleozoic to Cenozoic.

Uses & applications

Used as dimension stone, decorative polished stone, aggregate, cement and lime feedstock; attractive fossil-rich pieces are sold as lapidary or display specimens.

Geological facts

The visible white markings are fossil remains preserved in calcite, not crystal veins. Polishing can make the fossil pattern considerably more apparent.

Field identification & locations

Identify by its abundant fossil textures, carbonate reaction, relatively soft surface, and lack of interlocking igneous crystals; common in marine sedimentary formations worldwide, including the Midwest and many European limestone regions.