sedimentary

Fossiliferous limestone

Bioclastic limestone, chiefly calcite (CaCO₃), with fossil shell fragments

AI-generated identification · may be incorrect

Typically gray, brown, or reddish and fine- to coarse-grained, with visible shell or coral fragments; calcite has Mohs hardness 3, vitreous to dull luster, rhombohedral cleavage, and reacts vigorously with dilute hydrochloric acid. The rounded shape and smooth surface indicate water abrasion.

Identified August 16, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed when marine organisms accumulated, were buried, and cemented on an ancient seafloor; the fossils may date from Paleozoic to Mesozoic or younger strata, depending on locality. Iron staining accounts for the reddish-brown color.

Uses & applications

Used as aggregate, cement and lime feedstock, building stone, and decorative material; attractive polished pieces may be collected, but this example has modest commercial value.

Geological facts

The prominent inclusions appear to be fossil shells, crinoid fragments, or possibly coral rather than crystals. Acid testing and a close examination of broken surfaces can confirm calcite-rich limestone.

Field identification & locations

Common in former shallow-marine regions worldwide, including the United States, Europe, and Australia. Look for identifiable fossil structures, relatively low hardness, and effervescence with acid; avoid damaging legally protected fossils.