Limestone is a sedimentary rock, mainly composed of mineral calcite. The primary source of the calcite is usually marine organisms, which settle out of the water column and are deposited on the ocean floors as pelagic ooze (but see lysocline for information on calcite dissolution). Secondary calcite may also be deposited in super-saturated meteoric waters, as is evidenced by the creation of stalagmites and stalactites.
Bands of limestone emerge from the Earth's surface in often spectacular rocky outcrops and islands. For example the Verdon Gorge in France, Malham Cove in North Yorkshire, England and the Ha Long Bay National Park in Vietnam.
It is quarried for roadbeds and gravel roads, building and landscape construction, and cement manufacture. It is composed of animal shells and chemical precipitates with a large component of CaCO3 in them. In the Michigan basin, lime stones formed at many different times, when the basin was filled with water of varying depths. Below, the environment of deposition during Niagara time (when a lot of dolomites were forming in the Michigan Basin).
Uses of Limestone
It is used in road making, concrete aggregate, cement, lime for agricultural use, flux for smelting steel, building and walling stone, and even in toothpaste
History
In some way, the first bacteria and one-celled plants learned to take lime (CaCO3) from the water; they collected in jelly-like masses. Lime collected on these early plants, layer upon layer, and built up into great masses of limestone. Later, when animals came upon the earth they were also one-celled creatures living in the sea, but as they struggled for existence they evolved to more complex creatures, and in time they also took lime from the sea water to make protecting external coverings or shells.
