sedimentary

Fossiliferous limestone with a fossil sea urchin

Bioclastic limestone containing an echinoid fossil (class Echinoidea)

AI-generated identification · may be incorrect

The pale, rounded fossil has a radial pattern typical of an echinoid test; the surrounding rock is gray limestone with lighter fossil or mineral fragments. Calcite is Mohs 3, vitreous to dull, and rhombohedral; exact hardness and composition cannot be confirmed from the image.

Identified September 24, 2026More sedimentary →

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Physical properties

Formation & geological history

Marine organisms accumulated on an ancient seafloor, and their remains were buried and cemented into limestone. The fossil’s age is indeterminate from the photograph and may range from hundreds of millions to tens of millions of years old.

Uses & applications

Collected and displayed as a fossil specimen; limestone is also used for cement, aggregate, and building stone.

Geological facts

Sea urchin tests are commonly preserved in limestone, sometimes with their distinctive five-part symmetry visible.

Field identification & locations

Look for the fossil’s radial symmetry and calcite-rich, often fizzing-in-dilute-acid matrix; echinoid fossils occur in marine sedimentary rocks worldwide. The photo does not show enough detail to identify the species or locality.