sedimentary
Coquina
Biogenic Limestone (CaCO3)
Hardness: 3 (Mohs scale), Color: tan, cream, or light brown, Luster: dull to earthy, Structure: poorly cemented fragments of shells and coral, Specific Gravity: 2.3-2.6
Identified More sedimentary →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 3 (Mohs scale), Color: tan, cream, or light brown, Luster: dull to earthy, Structure: poorly cemented fragments of shells and coral, Specific Gravity: 2.3-2.6
Formation & geological history
Formed in high-energy marine environments (beaches or near-shore) where shell fragments accumulate and are loosely cemented together by calcite; typically Holocene or Pleistocene in age.
Uses & applications
Used primarily in construction (building stone, road base), landscaping, and as a natural source of calcium carbonate for agricultural use.
Geological facts
Famous for its use in the construction of the Castillo de San Marcos in Florida; it is a 'soft' rock that was paradoxically resistant to cannon fire because it absorbed the impact instead of shattering.
Field identification & locations
Identify by its 'granola bar' appearance made of visible shell fragments; commonly found in coastal areas of Florida and North Carolina. Collectors look for well-preserved whole shells within the matrix.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Sandstone (Quartz-rich)
Arenite (SiO2)
sedimentary
Sandstone (with man-made markings)
Arenite (composed primarily of Quartz, SiO2)
sedimentary