Graphite is the mineral typically used in making pencils. It is a form of carbon that is distinguished by its layered structure, which allows the layers to slide over each other easily, giving graphite its lubricating properties. When combined with clay and formed into solid cores, graphite becomes the pencil lead that produces marks on paper. The ratio of graphite to clay in the mixture determines the hardness or softness of the pencil, allowing for a range of writing experiences. This versatile material has been used for centuries in writing instruments.