C – graphite – is one of the allotropic modifications of carbon. Graphite is a crystalline compound with a metallic luster, ranging in color from grey to coal. Currently, graphite is used to produce artificial diamonds, another allotropic modification of carbon. Graphite is greasy and can leave marks on paper, which is why it is used in the manufacture of pencils. Its high conductivity makes it useful in the production of lithium-ion batteries for laptops, mobile phones, and tablets. It is even utilized in reactors in nuclear power stations.