Coal

Coal
Sedimentary rock
Coal bituminous.jpg
Bituminous coal
Composition
Primary carbon
Secondary
  • hydrogen
  • sulfur
  • oxygen
  • nitrogen
 
Lignite (brown coal)
 
Anthracite (hard coal)

Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata called coal seams. Coal is mostly carbon with variable amounts of other elements; chiefly hydrogen, sulfur, oxygen, and nitrogen.