Limestone is used in more dairy products than one might think. Limestone is a sedimentary rock, formed by inorganic remains, such as shells or skeletons, that have compressed for a very long time. The main element found in limestone is calcium carbonate but it may contain magnesium, iron or manganese as well, which affect the whiteness and hardness. Limestone is one of the major ingredients used in construction materials but also has many other uses in daily life.