The four types of coal are: (i) Peat: Decaying plants in swamps produce peat. It has a low carbon and high moisture contents and low heating capacity. (ii) Lignite is a low grade brown coal, which is soft with high moisture content.The principal lignite reserves are in Neyveli in Tamil Nadu and are used for generation of electricity. (iii) Bituminous coal is buried deep and subjected to increased temperatures. It is the most popular coal in commercial use. Metallurgical coal is high grade bituminous coal which has a special value for smelting iron in blast furnaces. (iv) Anthracite is the highest quality hard coal.