The limestones arise mostly through precipitation in sea water, either through the medium of living organisms that bind calcite (e.g. mussels) or inorganically. As living organisms play a major role in the development of limestones, it is natural that they should usually contain fossils. Although they are composed exclusively of calcite, these rocks can vary greatly in colour, from a very light shade to black, and their surface patterning can be highly variable, partly on account of the fossils, although they can also be typically fairly fine-grained in the absence of fossils.
A hard, dense limestone that will take a polish is often referred to commercially as marble. Limestone is quarried throughout the world and used, like marble, mainly on the inner surfaces of buildings (it is somewhat susceptible to urban climates).