When plant die, the remains usually rot and break down into water, carbon dioxide and simple salts. But is swamps and bogs, layers of rotting plants are often buried and the decay is halted. Slowly, these plant remains are pressed into a compact substance called peat.
When peat is dug up, 90 percent of its weight is often water. However, when it is dried, up to 60 percent of its weight is carbon, and so it is a useful fuel. As the plant remains are buried deeper and deeper, the pressure increases and the peat changes into lignite, which still contains a lot of water, then bituminous coal, and finally anthracite. Carbon forms up to 95 percent of anthracite. This hard, shiny coal doesn’t dirty your hands when you pick it up, and burns slowly giving out intense that.