Coquina [koh-kee-nuh] is a sedimentary rock that is composed either wholly or almost entirely of the transported, abraded, and mechanically-sorted fragments of the shells of mollusks, trilobites, brachiopods, or other invertebrates. The term coquina comes from the Spanish word for ‘cockle’ and ‘shellfish.’
Coquinas accumulate in high-energy marine and lacustrine environments where currents and waves result in the vigorous winnowing, abrasion, fracturing, and sorting of the shells that compose them. As a result, they typically exhibit well-developed bedding or cross-bedding, close packing, and good orientation of the shell fragments. The high-energy marine or lacustrine (lake) environments associated with coquinas include beaches, shallow submarine raised banks, swift tidal channels, and barrier bars.
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The Daily Omnivore 