sedimentary
Coquina
Bioclastic Limestone
Hardness: 2-3 (Mohs scale), Color: tan, brownish-white, or gray-white, Luster: dull to earthy, Crystal Structure: amorphous/biogenic, Cleavage: none, Specific Gravity: 2.3-2.5
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Physical properties
Hardness: 2-3 (Mohs scale), Color: tan, brownish-white, or gray-white, Luster: dull to earthy, Crystal Structure: amorphous/biogenic, Cleavage: none, Specific Gravity: 2.3-2.5
Formation & geological history
Formed in high-energy marine environments (beaches/reefs) by the accumulation and cementing of whole or broken shells and coral fragments. Most common in the Holocene epoch.
Uses & applications
Used as a historical building material (forts), road base material, landscaping, and in the production of lime.
Geological facts
The Castillo de San Marcos in Florida was built from coquina; its porous nature allowed it to absorb cannonball impacts rather than shattering.
Field identification & locations
Identify by its distinctly 'crunchy' appearance made of visible shell fragments. Common in coastal regions like Florida and North Carolina.
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