sedimentary
Coquina
Biogenic Limestone (Calcitic)
AI-generated identification · may be incorrectHardness: 2-3 (Mohs scale), Color: tan, grey, or white with visible shell fragments, Luster: dull to earthy, Structure: clastic/bioclastic with high porosity, Cleavage: poor/none.
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Physical properties
Hardness: 2-3 (Mohs scale), Color: tan, grey, or white with visible shell fragments, Luster: dull to earthy, Structure: clastic/bioclastic with high porosity, Cleavage: poor/none.
Formation & geological history
Formed in high-energy marine or lacustrine environments where shells and coral fragments are accumulated by waves and cemented together by calcium carbonate. Typically spans from the Holocene to several million years old.
Uses & applications
Historical use as building stone (e.g., Castillo de San Marcos), road base material, landscaping, and phosphate source in some regions.
Geological facts
The word 'coquina' is Spanish for 'cockle' or 'shellfish'. It is famous for being incredibly shock-absorbent; during colonial battles, cannonballs would sink into the rock rather than shattering it.
Field identification & locations
Identify by its distinctive 'oatmeal' or 'shredded wheat' appearance with clearly visible, whole or broken shells. Found along shorelines, notably in Florida, USA, and the Caribbean.
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