Graphite is another allotrope of carbon. Its atoms are bonded in sheets of hexagons, which are "stacked" and can slide over each other.

Graphite is a soft mineral, quite different to diamond. It smudges whatever it touches and it feels oily. Graphite conducts electricity about as well as lead, and its thermal conductivity is somewhere between those of .tin and lead.

Graphite is found naturally in the earth's crust, as a mineral with impurities. It is found in Sri Lanka, Siberia and North America, among other places.

Graphite is used in grey lead pencils. Lead pencils don't have any lead - their cores are graphite mixed with clay. Graphite is also used to make electrodes, especially where corrosive gases are given off, because graphite is unreactive. Graphite can be used as a lubricant by itself, or mixed with other things like oil, grease and water. Graphite can also be used for things that use very high temperatures, for example in furnaces and crucibles.

Graphite is also used in some reactors, to stop the reactions getting out of control. It slows the neutrons down, but doesn't stop them.