Coquina

  Coquina (pronounced /koʊˈkiːnə/) is an incompletely consolidated sedimentary rock of biochemical origin, mainly composed of mineral calcite, often including some phosphate, in the form of seashells or coral. It is created in association with marine reefs. While not usually referred to as such, it is actually a subset of limestone.

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Coquina is quarried or mined 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 fertilizer.

Occasionally used as a building stone in Florida throughout its history, it formed 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 its being soft, 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.

May also refer to the Donax, a type of bivalve.