Coquina

A detrital limestone composed wholly or chiefly of mechanically sorted fossil debris that experienced abrasion and transport before reaching the depositional site and that is weakly to moderately cemented, but not completely indurated; esp. a porous light-colored limestone made up of loosely aggregated shells and shell fragments, such as the relatively recent deposits occurring in Florida and used for roadbeds and construction.

Ref: AGI

For a sediment to be considered to be a coquina, the particles composing it should average 2 mm or greater in size. Coquina can vary from poorly to moderately cemented. Incompletely consolidated and poorly cemented coquinas can also be considered Lime-sand while well-cemented coquina can be classified as a Lime-grainstone or fossiliferous limestone. The fossils are typically molluscs and other shelly fossils, including coral. (Adapted from Wikipedia)

Commonly useful as a construction material.