Sedimentary
Coquina / Fossiliferous Limestone
Fossiliferous Limestone (CaCO3)
Hardness: 3-4 (Mohs scale), Color: tan, reddish-brown, white, Luster: dull to earthy, Crystal structure: poorly cemented shell fragments, Cleavage: none, Specific gravity: variable depending on porosity
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Physical properties
Hardness: 3-4 (Mohs scale), Color: tan, reddish-brown, white, Luster: dull to earthy, Crystal structure: poorly cemented shell fragments, Cleavage: none, Specific gravity: variable depending on porosity
Formation & geological history
Formed in shallow marine environments from the accumulation and cementation of shell debris over thousands to millions of years.
Uses & applications
Used historically and currently in construction, landscaping, and as an aquifer rock.
Geological facts
Coquina was famously used to build the Castillo de San Marcos in St. Augustine, Florida, because its porous nature absorbed cannonballs rather than shattering.
Field identification & locations
Identify by its highly porous structure composed visibly of shell fragments cemented together. Will fizz vigorously when dilute hydrochloric acid is applied.
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