Carbon

Carbon is an element. Its atomic weight is 12.011. Different forms and variations of carbon include soot, charcoal, graphite, and diamond. In fact, the word carbon derives from the Latin root "carbo" which means charcoal. With sufficient weight and temperature, it is possible to transform graphite into diamond.
                                                                               

What is usually called the 'lead' of a pencil is in fact graphite. You can also write with charcoal.