If limestone is relatively pure calcium carbonate, it is called calcitic limestone. However, limestone can also contain some magnesium carbonate, MgCO 3 . If limestone contains appreciable amounts of magnesium carbonate, it's known as dolomitic limestone.
Limestone occurs in thick beds that can be hundreds of feet thick.
To be useful in agriculture, limestone must be quarried and ground into a very five powder. The ground limestone is then spread on farm fields to reduce the amount of acidity in the soil. When soils are too acidic, crops do not grow well. Ground limestone also provides calcium and magnesium to crops. Plants can't live without these nutrients.