sedimentary

Coquina (Fossiliferous Limestone)

Biogenic Limestone (mostly CaCO3 / Calcium Carbonate)

AI-generated identification · may be incorrect

Hardness: 3-4 (Mohs scale), Color: Cream, tan, or white, Luster: Dull to earthy, Texture: Clastic/Biogenic with visible shell fragments, Specific Gravity: 2.3-2.5

Identified June 21, 2026More sedimentary →

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Physical properties

Hardness: 3-4 (Mohs scale), Color: Cream, tan, or white, Luster: Dull to earthy, Texture: Clastic/Biogenic with visible shell fragments, Specific Gravity: 2.3-2.5

Formation & geological history

Formed in high-energy marine environments where shell fragments and calcaleous remains accumulate and are loosely cemented together by calcite. Commonly found in coastal areas, particularly from the Pleistocene to Holocene epochs.

Uses & applications

Historically used as a building material (notably in Spanish forts like Castillo de San Marcos), as landscape stone, and as a source of lime for cement.

Geological facts

The name comes from the Spanish word for 'cockle' or 'shellfish'. Because it is somewhat porous, it was unique as a defensive material in forts, absorbing cannonballs rather than shattering like harder stone.

Field identification & locations

Identify by visible layers of crushed shells or whole mollusks. It will react and fizz (effervesce) strongly when exposed to dilute hydrochloric acid or vinegar. Common in Florida, North Carolina, and coastal Europe.