Rock Group

Sedimentary

Grain Size

Coarse fragments of crinoids and other fossils, such as gastropods, cemented with a matrix of finer calcite.

Composition

Calcium carbonate fragments including crinoid stems.

Key Features

This limestone includes the calcium carbonate skeletons of crinoids, gastropods and other organisms. The crinoid fossils form the segmented tube-like structure in this sample, where fragments are sections along and across the crinoid stem. Limestone can be made from a variety of calcium carbonate components from former living things like corals or shells. This sample could also be described as a crinoidal limestone, referring to the crinoid fossils that it contains.