Shelly limestone
Brachiopods and bryozoans in an Ordovician shelly limestone, southern Minnesota
Shelly limestone is a highly fossiliferous limestone, composed of a number of fossilized organisms such as brachiopods, bryozoans, crinoids, sponges, corals and mollusks. It varies in color, texture and hardness. Coquina is a poorly indurated form of shelly limestone.
Shelly limestone is a sedimentary rock because it is fragmental. To be shelly, it is full of broken shells which are "glued" together with calcite. Calcium carbonate often makes up around 10% of the volume, whilst many varied sized shells from granular to very large pebbles. Its color is gray.