(a) Formation of coal:- The formation of coal took millions of years. Coal was formed by the bacterial decomposition of ancient vegetable matter hurried under successive layers of the earth. Under in action of high temperature and pressure, and in the absence of air, the decayed vegetable matter converted into coal.
(b) Types of Coal:
1. Peat: It is light brown in colour and contains only 50 – 60% carbon. It is the most inferior form of coal.
2. Lignite: it contains more than 60% carbon. It is brown in color and harder than peat.
3. Bituminous: It has 90%, 80%, 70 – 75% carbon contents. Bituminous coal is the most common variety of coal and used as household coal.
4. Anthracite: It is the purest variety of coal. Its carbon contents vary between 92 – 98%. It is hard, dense and black, difficult to ignite.
Uses of coal:
1. Coal is used as both domestic and industrial fuel.
2. It is used to prepare coke, coal gas and coal tar.
