A combustible black or brownish-black sedimentary rock usually occurring in rock strata in layers or veins called coal beds or coal seams. Primarily burned as a fossil fuel for the production of electricity and/or heat, and is also used for industrial purposes such as refining metals.
Rocks and minerals from which metallic iron can be economically extracted. Usually rich in iron oxides and vary in colour from dark gray, bright yellow, deep purple, to rusty red. 98% of the mined iron ore is used to make steel.