Lime is generally not available in the free state in nature. It is mainly produced by burning limestone. Depending on the percentage of calcium carbonate (CaCO3) in the limestone, lime is classified into A, B and C types, which are used for masonry, mortar and plaster and whitewash respectively. Type C type is also called pure lime or fat lime. Class A variety is available only in slaked form, while Class B and C are available in slaked and unslaked forms. Lime is also obtained by burning pebbles, sea animal shells, and limestone boulders from old river beds.
Lime obtained by calcination of pure limestone is called quicklime. It consists mainly of calcium oxide and is not crystalline. It shows a strong correlation with humidity.
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