From Wiki so it must be true:
It is the raw material for the manufacture of quicklime (calcium oxide), slaked lime (calcium hydroxide), cement and mortar.
Pulverized limestone is used as a soil conditioner to neutralize acidic soils.
It is crushed for use as aggregate—the solid base for many roads.
As a reagent in flue-gas desulfurization, it reacts with sulfur dioxide for air pollution control.
Glass making, in some circumstances, uses limestone.
It is added to toothpaste, paper, plastics, paint, tiles, and other materials as both white pigment and a cheap filler.
It can suppress methane explosions in underground coal mines.
Purified, it is added to bread and cereals as a source of calcium.
Calcium levels in livestock feed are supplemented with it, such as for poultry (when ground up).[11]
It can be used for remineralizing and increasing the alkalinity of purified water to prevent pipe corrosion and to restore essential nutrient levels.[12]
Used in blast furnaces, limestone binds with silica and other impurities to remove them from the iron.
It is often found in medicines and cosmetics.
