LIMESTONE
Limestone is a biogenic sedimentary rock composed of the mineral calcite (CaCO3),
which bubbles in acid. There are numerous varieties of limestone (e.g.,
fine-grained limestone/micritic limestone/lime mudstone, coquina, chalk,
wackestone, packstone, grainstone, rudstone, calcarenite, calcisiltite,
calcilutite, calcirudite, floatstone, boundstone, framestone, oolitic
limestone, oncolitic limestone, etc.). The most distinctive type can be
given the generalized name fossiliferous limestone, which is composed of
abundant whole & fragmented fossil shells and skeletons. Most
limestones represent deposition in ancient warm, shallow ocean environments.
Fossiliferous limestone from the Upper Ordovician (Kope Formation, lower
Cincinnatian Series) of southwestern Ohio, USA. It is richly
fossiliferous - mostly brachiopod shells, some bryozoans, some crinoid stem
pieces, and some trilobite fragments.