sedimentary
Coquina with Shell Fragment
Bioclastic Limestone (composed primarily of CaCO3)
Hardness: 3 (Mohs scale); Color: Cream, tan, or white; Luster: Dull to pearly (on shell surfaces); Structure: Fragmental/Clastic; Cleavage: None (fractures irregularly).
- Hardness
- 3 (Mohs scale)
- Color
- Cream, tan, or white
- Luster
- Dull to pearly (on shell surfaces)
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Physical properties
Hardness: 3 (Mohs scale); Color: Cream, tan, or white; Luster: Dull to pearly (on shell surfaces); Structure: Fragmental/Clastic; Cleavage: None (fractures irregularly).
Formation & geological history
Formed in high-energy marine environments (beaches/shallow reefs) where shell fragments accumulate and are cemented together by calcium carbonate over hundreds to thousands of years.
Uses & applications
Used primarily in construction, historically for building forts (like Castillo de San Marcos) due to its shock-absorbing properties, and for landscaping or road base.
Geological facts
Coquina was historically a vital building material in Florida because it is soft enough to quarry but 'elastic' enough to absorb cannonball impacts rather than shattering.
Field identification & locations
Identify by its 'mushy' or 'granola-like' appearance of visible shells. Found along coastlines, particularly in Florida and North Carolina. It will fizz if a drop of vinegar is applied.
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