The element used in pencil-lead is Carbon in the form of graphite. Pencil ‘lead’ is not made of the metal lead. It is primarily composed of graphite, which is an allotrope of Carbon, mixed with clay. Graphite is a soft, black, slippery solid that conducts electricity. Its layered structure allows it to leave marks on paper. The amount of clay mixed with graphite determines the hardness of the pencil lead.