For the variety of clam, see Donax .
Coquina outcropping on the beach at Washington Oaks State Gardens, Florida

Coquina (play /kˈknə/; Spanish: "cockle") is a sedimentary rock that is composed either wholly or almost entirely of the transported, abraded, and mechanically sorted fragments of the shells of either molluscs, trilobites, brachiopods, or other invertebrates. For a sediment to be considered to be a coquina, the average size of the particles composing it should be 2 mm or greater in size. Coquina can vary in hardness from poorly to moderately-cemented. The term "coquina" is derived from the Spanish word for cockleshells or shellfish.[1][2] Incompletely consolidated and poorly cemented coquinas are considered grainstones in the Dunham classification system for carbonate sedimentary rocks. [3] Well-cemented coquinas are classified as biosparites according to the Folk classification of sedimentary rocks.[4]

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, which compose them. As a result, they typically exhibit well-developed bedding or cross-bedding, close packing, and good orientation of the shell fragments composing them. The high-energy marine or lacustrine associated with coquinas include beaches, shallow submarine raised banks, swift tidal channels, and barrier bars.[4][5]


Composition and distribution

Coquina is mainly composed of mineral calcite, often including some phosphate, in the form of seashells or coral. It is found in surface exposures along the east coast of Florida from St. Johns County to Palm Beach County. It may occur up to 20 miles inland from the coast in the sub-surface. It is found as far north as Fort Fisher, North Carolina. It has also been formed in the South Island of New Zealand, where it outcrops in a disused quarry near Oamaru. The Oligocene deposits here are composed primarily of very well preserved brachiopod shells, in a matrix of brachiopod, echinoid, and bryozoan detritus and foraminifera.

History and use

Coquina from Florida.
Close-up of coquina from Florida. The scale bar is 10 mm.

Occasionally quarried or mined and used as a building stone in Florida for over 400 years, coquina forms the walls of the Castillo de San Marcos, Saint Augustine. The stone makes a very good material for forts, particularly those built during the period of heavy cannon use. Because of coquina's softness, cannon balls would sink into, rather than shatter or puncture, the walls of the Castillo de San Marcos.

When first quarried, coquina is extremely soft. This softness makes it very easy to remove from the quarry and cut into shape. However, the stone is also at first much too soft to be used for building. In order to be used as a building material, the stone is left out to dry for approximately one to three years, which causes the stone to harden into a usable, but still comparatively soft, form.

Coquina has also been used as a source of paving material. It is usually poorly cemented and easily breaks into component shell or coral fragments, which can be substituted for gravel or crushed harder rocks. Large pieces of coquina of unusual shape are sometimes used as landscape decoration.

Because coquina often includes a component of phosphate, it is sometimes mined for use as fertilizer.

Notable exposures of coquina

Coquina in architecture


  1. ^ U.S. Bureau of Mines Staff (1996) Dictionary of Mining, Mineral, & Related Terms. Report SP-96-1, U.S. Department of Interior, U.S. Bureau of Mines, Washington, D.C.
  2. ^ Neuendorf, K.K.E., J.P. Mehl, Jr., and J.A. Jackson, J.A., eds. (2005) Glossary of Geology (5th ed.). Alexandria, Virginia, American Geological Institute. 779 pp. ISBN 0-922152-76-4
  3. ^ Dunham, R.J. (1962). Classification of carbonate rocks according to depositional texture. In Ham, W. E.. Classification of carbonate rocks. American Association of Petroleum Geologists Memoir. no. 1, pp. 108-121.
  4. ^ a b Folk, R.L. (1980) The Petrology of Sedimentary Rocks. Austin, Texas, Hemphill Publishing Company. 182 pp. ISBN 100914696149
  5. ^ Scholle, P.A., D.G. Bebout, and C.H. Moore (1983) Carbonate Depositional Environments. Memoir no. 33. Tulsa, Oklahoma, American Association of Petroleum Geologists. 708 pp. ISBN-13 978-0891813101

See also

External links

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Look at other dictionaries:

  • Coquina — sur la plage du Washington Oaks State Gardens en Floride …   Wikipédia en Français

  • Coquina — Co*qui na, n. [Sp., shellfish, cockle.] A soft, whitish, coral like stone, formed of broken shells and corals, found in the southern United States, and used for roadbeds and for building material, as in the fort at St. Augustine, Florida. [1913… …   The Collaborative International Dictionary of English

  • coquina — sustantivo femenino 1. Área: zoología Molusco pequeño con una concha de dos piezas ovaladas y muy aplastadas, que abunda en el litoral del suroeste de la península ibérica y es apreciado como alimento: Mi madre compró medio quilo de coquinas para …   Diccionario Salamanca de la Lengua Española

  • coquina — f. Molusco acéfalo, cuyas valvas, de tres a cuatro centímetros de largo, son finas, ovales, muy aplastadas, y de color gris blanquecino con manchas rojizas. Abunda en las costas gaditanas y su carne es comestible …   Diccionario de la lengua española

  • coquina — ☆ coquina [kō kē′nə ] n. [Sp, shellfish, dim. < dial. form of L concha: see CONCH] 1. a soft, whitish limestone made up of broken sea shells and corals: used as a building material 2. any of a genus (Donax) of small, delicately colored… …   English World dictionary

  • Coquina — ► sustantivo femenino ZOOLOGÍA Molusco bivalvo marino de la familia de las tellerinas, pequeños y de forma oval, comunes en playas y costas. * * * coquina 1 (Donax trunculus y otras especies del mismo género) f. Molusco *lamelibranquio comestible …   Enciclopedia Universal

  • coquina — /koh kee neuh/, n. 1. Also called pompano, butterfly shell clam. a small clam, Donax variabilis, abundant in the intertidal zone of eastern and southern U.S. coastal beaches, having fanlike bands of various hues, the paired empty shells often… …   Universalium

  • coquina — {{#}}{{LM C10446}}{{〓}} {{[}}coquina{{]}} ‹co·qui·na› {{《}}▍ s.f.{{》}} Molusco marino de carne comestible, con valvas finas, ovales, muy aplastadas y de color gris blanquecino con manchas rojizas: • Las coquinas abundan en las playas de… …   Diccionario de uso del español actual con sinónimos y antónimos

  • Coquina Beach — is a beach in North Carolina, USA located in the Cape Hatteras National Seashore. It is located not far from the Wright Brothers National Memorial and is off highway 12 at milepost 26, 8 miles (13 km) south of Nags Head, North Carolina.… …   Wikipedia

  • Coquina (roca) — Saltar a navegación, búsqueda Coquina …   Wikipedia Español

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