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Coquina () is a sedimentary rock that is composed either wholly or almost entirely of the transported, abraded, and mechanically sorted fragments of mollusks, , , or other . (2025). 9780922152766, American Geological Institute. ISBN 9780922152766 The term coquina comes from the Spanish language word for "cockle" and "shellfish".English Wiktionary: '' mussel, shell."
For a sediment to be considered to be a coquina, the particles composing it should average or greater in size. Coquina can vary in hardness from poorly to moderately cemented. Incompletely consolidated and poorly cemented coquinas are considered in the Dunham classification system for carbonate sedimentary rocks. A well-cemented coquina is classified as a biosparite (fossiliferous limestone) according to the Folk classification of sedimentary rocks.
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 environments associated with coquinas include beaches, shallow submarine raised banks, swift tidal channels, and barrier bars. (1983). 9780891813101, American Association of Petroleum Geologists. ISBN 9780891813101
St Andrew's Anglicanism Church, the Old Pearler Restaurant, and parts of the Shark Bay Hotel in Shark Bay were built from coquina shell blocks. The church, built in 1954, has walls infilled with coquina shell blocks between a light steel frame and a shell facing, while the Old Pearler was built in 1974–1977 with buttressed coquina shell block walls.
The Palynology record of coquinas of the Sergipe-Alagoas Basin has been analyzed and the sediments dated to the late Barremian; the results suggest a marine and/or brackish environment. Daniel Thompson (2013) asserts that the coquinas of the Morro do Chaves Formation include a wide range of marine mollusca characteristic of brackish environmental conditions, suggesting periodic marine ingression during the Early Cretaceous.
According to a paper by Senira Kattah published in The Sedimentary Record, the discovery of the Lula Field by Petrobras and partners in 2006 opened petroleum exploration in the Barremian/Aptian pre-salt play in the offshore Santos and Campos basins, and consequently deeper coquina reservoirs have become important targets. He says the two main reservoir targets recognized for the pre-salt within the study areas are: "late rift coquinas, lacustrine facies deposited at the Late Barremian to Early Aptian, and the younger rift/sag microbial limestones deposited during the Aptian, just before the establishment of the major evaporitic sag basin between South America and Africa." There are abundant beds of coquina in the Outer High of the Santos Basin, similar to those from the neighboring Campos. (2015). 9781862397279, Geological Society of London. ISBN 9781862397279 Pre-salt stratigraphy of the Santos Basin shows lacustrine sediments composed of coarse pelecypod (bivalve) coquina during the Barremian and Aptian sag phase of the continental crust subsidence. (2017). 9781786202437, Geological Society of London. ISBN 9781786202437
Other Pleistocene outcrops occur along both coastlines of the upper Gulf of California. On the Vizcaino Peninsula of western Baja California, the informally named "Tivela stultorum" coquina is abundant in shells of the Pismo clam. Until analysis of the shells by U-series and amino-acids methods is concluded, this marine transgression is assigned an approximate age of 200,000 ybp. Outcrops in Bahía de San Hipolito and Bahía de Asunción are loosely consolidated, sandy beachrock a few meters thick, found above present mean sea level.
The ancient Maya built their city of Toniná in the highlands of what is now Chiapas in southern Mexico using native rocks to construct its masonry buildings, among them large coquina from which they made blocks and bricks for floors, walls, and stairways.
Still occasionally quarry or mining, and used as a building stone in Florida for over 400 years, coquina forms the walls of the Castillo in St. Augustine. The stone made a very good material for building forts, particularly those built during the period of heavy cannon use. Because of coquina's softness, cannonballs would sink into, rather than shatter or puncture the walls. The first Saint Augustine lighthouse, built by the Spanish, was also made of coquina.
Coquina was used as building stone in St. Augustine as early as 1598 for construction of a powder house. This was the beginning of a building tradition that extended into the 1930s along Florida's Atlantic Coast. In the St. Augustine vicinity, the Castillo de San Marcos, Fort Matanzas, the old city gates, the Cathedral, Spanish and British Period residential structures, property line walls and tombs were constructed of coquina quarried on Anastasia Island. To the south in New Smyrna, a large storehouse and wharf were constructed of coquina at the 1770s Andrew Turnbull colony. Around 1816, John Addison constructed a kitchen house of coquina on his plantation on the Tomoka River. The material was also used in the construction of sugar mill buildings on sugar plantations in the 1820s and 1830s. Examples are the Bulow, Dunlawton and New Smyrna sugar mills. In these early structures, the porous coquina was protected by lime plaster. With the exception of a few residences that have been restored in St. Augustine, the coquina masonry of these structures is today exposed to the elements and is slowly deteriorating.
Historical records and extant buildings, foundations, basements, and retaining walls indicate that coquina was being mined in North Carolina by at least 1760, evidenced by the extant architectural ruins at the colonial-era Clear Springs Plantation near New Bern.
Sedgeley Abbey, an 18th-century plantation house on the lower Cape Fear River was built of locally quarried coquina. The house that once stood on a vast tract of land directly across the river from Orton Plantation was described by local historian and author James Sprunt as "the grandest colonial residence of the Cape Fear". Sprunt compared Sedgeley Abbey in dimensions and appearance to the two-story, cellared, Governor Dudley mansion that still stands in Wilmington. Like many southern plantations, Sedgeley Abbey was abandoned after the Civil War. The vacant house was demolished in the 1870s and the coquina rubble was burned and spread on the fields as fertilizer. A cellar eight feet deep carved into solid coquina was located during archaeological investigations on the site of the former plantation in 1978.
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. In the 1930s, large-scale mining of coquina for use in highway construction began at Fort Fisher in North Carolina. 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.
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