Limestones can be made up of many different types of
material. Some are made, like sandstones, of transported and
deposited grains, others are made of the skeletons or shells
of animals, and others are mainly composed of very fine
carbonate mud. Oolitic limestones belong to the first type.
They are made up largely of ooids, which are sand-sized,
rounded pellets of calcium carbonate formed in warm shallow
water where carbonate sediment is moved about by currents.
This example also contains a proportion of shell fragments.
Rounded ooids and platy shell fragments can be made out in
the detailed view below ().