sedimentary
Coquina
Bioclastic Limestone
AI-generated identification · may be incorrectHardness: 3 (Mohs scale), Color: tan, cream, or light brown, Luster: dull to earthy, Structure: poorly consolidated mass of shell fragments, Porosity: very high
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Physical properties
Hardness: 3 (Mohs scale), Color: tan, cream, or light brown, Luster: dull to earthy, Structure: poorly consolidated mass of shell fragments, Porosity: very high
Formation & geological history
Formed in high-energy marine environments like beaches and barrier islands where wave action accumulates shell fragments. Most recognizable deposits are from the Pleistocene and Holocene epochs.
Uses & applications
Historically used as a building material (notably in St. Augustine, Florida), road base material, and in landscaping or aquarium decoration.
Geological facts
The Castillo de San Marcos in Florida was built from coquina; the stone's porous nature allowed it to absorb cannonball impacts rather than shattering.
Field identification & locations
Identify by looking for a 'cereal bar' appearance made of visible broken seashells. Found along coastlines, particularly in Florida, the Carolinas, and Australia.
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