Coquina
Image: <a rel="nofollow" class="external text" href="https://www.flickr.com/people/47445767@N05">James St. John</a> (CC BY 2.0)
Mineral NameCoquina
Chemical FormulaCaCO3 (primary component from shells)
Mohs Hardness3
Streak ColorWhite
CleavageN/A for rock; constituent calcite has perfect rhombohedral cleavage
FractureUneven to earthy
Specific Gravity2.7
Colorswhite, off-white, light brown, pinkish-orange
TransparencyOpaque
Type LocalityCayo Costa Island, Florida, USA (Anastasia Formation)
Mineral GroupSedimentary rock (Biogenic Limestone)
Usesbuilding material, road aggregate, decorative stone, geological studies
Associated Mineralscalcite, aragonite, quartz
Description
A light-colored, porous biogenic sedimentary rock composed predominantly of cemented shell fragments and sand, varying in size from fine grains to whole shells.
Geological Context
Coquina forms in shallow marine, high-energy environments where abundant shell material accumulates and is subsequently cemented by calcium carbonate, often found in Quaternary coastal deposits.
