Minerals: Which mineral is used in making pencils?

Graphite is the mineral used as the "lead" in pencils, despite the common misnomer. Graphite is a form of carbon with a layered crystal structure that allows it to easily leave marks on paper. Its softness and ability to be mixed with clay in varying proportions creates pencils of different hardness grades. Graphite is also used in lubricants, batteries, and as a moderator in nuclear reactors due to its excellent electrical conductivity and thermal properties.