Coquina

coquina

Limestone formed almost entirely of sorted and cemented fossil debris, most commonly coarse shells and shell fragments. Microcoquinas are similar sedimentary rocks composed of finer material. Common among microcoquinas are those formed from the remains of crinoids (marine invertebrates, such as sea lilies, that have limy disks and a limy internal skeleton). A distinction is made between a coquina, which is a rock formed from debris, and coquinoid limestone, which is composed of coarse shelly materials with a fine-grained matrix.

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coquina (clam)

Any clam of the genus Donax, inhabiting sandy beaches worldwide. Coquinas are very active; they migrate up and down beaches with the tide and can reburrow between waves. They have short siphons and feed on suspended plant material and detritus. A typical species, D. variabilis, measures about 0.4–1 in. (10–25 mm) in length. Its shell is wedge-shaped and varies from white, yellow, and pink to blue and mauve.

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coquina [kō′kē·nə]

(invertebrate zoology)

A small marine clam of the genusDonax.

(petrology)

A coarse-grained, porous, easily crumbled variety of limestone composed principally of mollusk shell and coral fragments cemented together as rock.

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coquina

A soft limestone formed primarily of broken shells and coral; cut into blocks and used in construction.

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Coquina 

limestone consisting primarily of the shells of marine animals or fragments of shells. Coquina usually forms in the littoral or sublittoral zones. Depending on the shells of which it is composed, coquina is subdivided into brachiopod, gastropod, ostracod, and other types. It corresponds to gravelpebble sediments in granulometric composition. Coquina has a very high porosity of 22–60 percent. Its specific gravity is 1,100-2,240 kg/m³, and its heat conductivity coefficient is 0.29-0.99 watt/(m-°K), or 0.25-0.85 kcal/(hr-m-°C). Its breaking point upon compression is 0.4-28 MN/m² (4-280 kg/cm²).

Coquina is easily sawed, trimmed, and worked in various other ways. It is used extensively in construction as a wall and facing material; chipped rock and sand from coquina are used as a filler for light concrete. In addition, coquina is used in the production of lime and other binding materials. It is extracted in quarries.

Coquina is widespread in the Neogene beds of the southern USSR: in the Moldavian SSR, in the Crimean (the Mamai, Kutur-Kaia, Bagerovo, and Karalar deposits) and Odessa oblasts of the Ukrainian SSR, in the Azerbaijan SSR (the Apsheron Peninsula), and in the Turkmen SSR. Abroad, coquina is found in Poland and Rumania.