Graphite and diamonds are two forms of carbon that are pure and commonly found in nature. Charcoal and coke are considered impure forms of carbon.
Carbon is the sixth most abundant element in nature and forms the basis for all of the organic molecules in all living organisms, including fats, proteins, carbohydrates and nucleic acids. Behind oxygen, carbon is the second most abundant element in the human body, accounting for 18 percent of body weight. Carbon forms strongly bonded chains, sealed off by hydrogen atoms to create hydrocarbons, such as those found in coal, oil and natural gas. Burning hydrocarbons completely creates water and carbon dioxide.