Graphite is a soft steel-gray or black mineral that is greasy to the touch. It is a form of the chemical element carbon.
Manufacturers use graphite in making a variety of products. For example, they harden graphite with clay to produce the material in pencils that we call “lead.” At one time, graphite was mistaken for lead. But lead is much denser than graphite. The name graphite comes from a Greek word meaning to write. The German geologist Abraham Werner named the mineral in 1789.
Natural graphite is widely distributed in a number of countries. The United States imports most of its natural graphite from Mexico. Graphite can be manufactured from coke by heating the coke in an electric furnace. The American inventor Edward Acheson developed the process for making graphite from coke in 1896. Manufactured graphite is purer and more dense than natural graphite. It also costs more. But manufactured graphite makes up about 80 percent of the graphite used in the United States.
Graphite has many uses in addition to pencils. It conducts electric current and is difficult to burn. For these reasons, many electrodes (electric contact points) are made of graphite. Graphite electrodes work under conditions that would destroy metal electrodes. Graphite conducts heat. It does not combine with other chemicals except at high temperatures. Therefore, many crucibles (melting pots for metals) are made from graphite. Graphite is not easily dissolved. For this reason, it is built into tanks that hold strong acids. Bricks of graphite form the cores of some nuclear reactors. The graphite slows down neutrons (atomic particles) in the reactors to keep the reactors operating properly. Graphite’s slipperiness makes it a good lubricant for clocks, door locks, and other machines with small parts. Graphite is also the major raw material for synthetic diamonds.
Both graphite and diamond are made from pure carbon. But diamond is extremely hard and transparent. Diamond also is much denser than graphite. Graphite and diamond have different crystal structures—that is, the carbon atoms are arranged differently in the two minerals. Graphite consists of carbon atoms arranged in flat layers known as graphene sheets. The layers slide easily over each other. The sliding layers make graphite soft and slippery. In diamond, the atoms are arranged in a strong three-dimensional pattern. That structure prevents the atoms from slipping over each other.
See also Carbon; Geim, Andre Konstantin; Novoselov, Konstantin; Pencil; Powder metallurgy.
