sedimentary

Fossiliferous limestone with a fossil shell

Calcite-rich limestone (CaCO₃), containing a likely brachiopod or bivalve fossil

AI-generated identification · may be incorrect

Gray, coarse and irregular, with a pale calcite-rich area and a rounded fossil-like structure. Calcite has Mohs hardness 3, vitreous to dull luster, and rhombohedral cleavage; limestone texture varies and may fizz in dilute acid.

Identified October 15, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed from carbonate sediment in a marine environment; the embedded shell may be hundreds of millions of years old, but age cannot be determined from the image alone.

Uses & applications

Limestone is used for cement, aggregate, and building stone; fossil-bearing pieces are mainly collected or displayed.

Geological facts

The rounded feature appears to preserve shell material or its impression, while the white portion may be calcite cement or vein fill.

Field identification & locations

Look for shell-like symmetry, ribs, or growth lines and test a fresh spot with dilute acid for effervescence. Fossiliferous limestone is common in ancient marine sedimentary deposits worldwide.