Coal

Coal varies in quality according to the amount of pressure and heat to which it is subjected to during its formation.

Coal consists largely of carbon, hydrogen and oxygen and a small amount of sulphur. It comes in 3 forms.

A Swampy Forest

Lignite	Bituminous	Anthracite
Soft brown coal	Dull grey in colour Intermediate between lignite and anthracite	It is black in colour Hard coal It is lustrous
38% carbon	65% carbon	96% carbon
19% volatile matter		1% volatile matter
43% moisture		3% moisture
Its calorific value is 14 to 19 KJ/g produces a lot of smoke	Calorific value is 28 to 31KJ/g	Calorific value 31 to 34 KJ/g burns cleanly with less smoke

Sub Topics

Coal from Mines
Open Cast Mine
Drift Mine

Coal from Mines

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Coal is formed in layers called seams. Layers of other rocks are there amidst coal seams. A mine shaft is dug through these rocks and the coal seam is reached. Then tunnels are dug into the coal.

Open Cast Mine

Twisting of the rocks may sometimes bring the coal nearer to the earth's surface, so that an open-cast mine can be made use of. The figure shows an open cast mine.

Drift Mine

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Sometimes a valley is formed naturally due to erosion of rivers exposing a coal seam, making man's work easy. Hence drift mining can be done by digging into the valley.