coal : Coal is a flammable black hard rock used as a solid fossil fuel. It is mainly made up of 65-95% carbon and also contains hydrogen, sulphur, oxygen and nitrogen. It is a sedimentary rock formed from peat, by the pressure of rocks laid down later on top.The four types of coal include peat, lignite, bituminous, and anthracite, with anthracite being most desirable due to its high heat content.
Lignite coal is the lowest rank of coal. It has carbonized past the point of being peat, but contains low amounts of energy. its carbon content is about 25-35%. It comes from relatively young coal deposits, about 250 million years old.Coal formation began during the Carboniferous Period – known as the first coal age – which spanned 360 million to 290 million years ago. The build-up of silt and other sediments, together with movements in the earth’s crust – known as tectonic movements – buried swamps and peat bogs, often to great depths.Where is coal found? Coal reserves are available in almost every country worldwide, with recoverable reserves in around 70 countries. The biggest reserves are in the USA, Russia, China and India. There are an estimated 892 billion tonnes of proven coal reserves worldwide.