Limestone is used in more daily 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 used in a wide range of plastic and elastomeric, or rubber, products. The regular and controlled shape of the limestone particles and the size of these particles makes it a great filler material for the production of plastic and rubber. Fillers are used to expand expensive plastics or other materials to increase the product size without the cost. Since limestone is a non-reactive material, it is perfect for this application.