sedimentary
Coquina
Biogenic Limestone (Calcitic)
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.
Identified More sedimentary →
Explore Coquina in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
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.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Cone-in-cone structure (Limestone)
Cone-in-cone structure (Secondary Sedimentary Structure)
sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Sandstone Grain
Clastic Sedimentary Rock Grain (SiO2 dominated)
sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary