Carbon, in the form of diamond, is the hardest natural material on Earth.
Carbon is found in a wide variety of rocks, such as chalk and limestone.
Compounds of carbon such as coal, natural gas and oil, provide the world's most important fuels. Carbon dioxide is also found dissolved in all water. Carbon is an essential element in many of the man-made, or synthetic, substances that we use in the modern world, for example, plastics, all synthetic fabrics, many medicines and a wide variety of other chemicals. Not surprisingly, perhaps, among this huge variety of substances, most of which are good for our way of living, there will be some that cause concern. Carbon-containing compounds called CFCs have been responsible for destroying part of the world's protective ozone layer.