sedimentary
Coquina
Bioclastic Limestone
Hardness: 3 (variable), Color: White to tan/brownish, Luster: Dull/earthy, Structure: Highly porous and composed of fragmented shells/skeletons, Specific Gravity: Low (feels light).
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: 3 (variable), Color: White to tan/brownish, Luster: Dull/earthy, Structure: Highly porous and composed of fragmented shells/skeletons, Specific Gravity: Low (feels light).
Formation & geological history
Formed in high-energy marine environments where shell fragments and coral debris are broken up by wave action and later cemented together by calcium carbonate.
Uses & applications
Used primarily in construction for roads and buildings, particularly historical architecture in Florida and the Caribbean. It was historically used for fortifications because its soft nature could absorb cannonballs.
Geological facts
The Castillo de San Marcos in St. Augustine, Florida, was built from coquina; the stone's porous nature allowed it to 'swallow' cannonballs rather than shattering.
Field identification & locations
Identify by its 'granola break' appearance, lack of organized bedding, and presence of visible shell fragments. Commonly found along shorelines and coastal plains.
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