What is coal? A natural dark brown to black graphitelike material, an organic sedimentary rock formed from fossilized plants and consisting of amorphous carbon with various organic and some inorganic compounds: coal is a fossil fuel formed from plants that were buried millions of years ago. The high-temperature, high-pressure conditions transformed the plants physically and chemically, forming coal.
Whith the links you can access at more information and also know more about the techniques of coal mining.
Links:
http://geology.com/rocks/coal.shtml
https://en.wikipedia.org/wiki/Coal_mining
http://www.worldcoal.org/coal/what-is-coal/
http://www.mining-technology.com/features/feature-the-10-biggest-coal-mines-in-the-world/
http://test.stoa.usp.br/articles/0016/5403/coal_for_metallurgical_coke_production.pdf
