sedimentary
Coquina
Biogenic Limestone (Coquina)
AI-generated identification · may be incorrectHardness: 2-3 (Mohs scale), Color: tan, buff, or white, Luster: dull/earthy, Structure: clastic/fragmental, Cleavage: N/A, Specific Gravity: 1.5 - 2.5
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Physical properties
Hardness: 2-3 (Mohs scale), Color: tan, buff, or white, Luster: dull/earthy, Structure: clastic/fragmental, Cleavage: N/A, Specific Gravity: 1.5 - 2.5
Formation & geological history
Formed in high-energy marine environments like beaches and barrier islands where shell fragments accumulate and are rapidly cemented by calcium carbonate; typically Holocene or Pleistocene in age.
Uses & applications
Used as a construction material, in road base, as decorative landscaping stone, and historically as a primary building material for coastal fortifications due to its ability to absorb cannon fire.
Geological facts
The Castillo de San Marcos in St. Augustine, Florida, is the most famous structure built of coquina; its porous nature allowed it to absorb cannonball impacts rather than shattering.
Field identification & locations
Identify by its 'oatmeal' or 'shredded wheat' appearance consisting almost entirely of visible, broken shell fragments; commonly found along coastlines of Florida and the Carolinas.
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