sedimentary

Fossiliferous Limestone (Coquina / Shell Limestone)

Biogenic Limestone (Calcium Carbonate, CaCO3)

AI-generated identification · may be incorrect

Hardness: 3-4 (Mohs scale); Color: Brownish-red matrix with white/cream fossil inclusions; Luster: Dull to earthy; Texture: Clastic/Bioclastic with visible shell fragments.

Hardness: 3-4 (Mohs scale)
Color: Brownish-red matrix with white/cream fossil inclusions
Luster: Dull to earthy

Identified May 3, 2026More sedimentary →

Explore Fossiliferous Limestone (Coquina / Shell Limestone) in the encyclopedia →

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Physical properties

Hardness: 3-4 (Mohs scale); Color: Brownish-red matrix with white/cream fossil inclusions; Luster: Dull to earthy; Texture: Clastic/Bioclastic with visible shell fragments.

Formation & geological history

Formed in shallow marine environments where shells and skeletal remains of organisms like mollusks and brachiopods accumulated. Over millions of years, these sediments were compacted and cemented by calcite.

Uses & applications

Used as a construction material, decorative stone, architectural facing, and in the production of lime and cement. Well-polished pieces are used in lapidary work.

Geological facts

This specific specimen appears to be water-worn, likely found on a beach or in a riverbed, which has smoothed the outer surface to reveal cross-sections of the fossils inside.

Field identification & locations

Identify by the presence of visible shell fragments or 'swirly' white patterns against a darker matrix. It will react and fizz if a drop of weak acid (like vinegar) is applied. Highly common in coastal regions.