Graphite

Graphite is the most stable form of carbon in nature. This black mineral is very brittle and can easily be broken by hand. The name derives from the Greek word grapho (to write), as graphite is the material used to make pencils. Graphite occurs naturally in different types of ores; crystalline graphite usually shows hexagonal or angular edges when freshly broken. This is a reflection of the crystalline structure in which the carbon atoms are arranged in honeycomb layers stacked on top of each other. Apart from its use in pencils, graphite is also used for its ability to conduct electric current (i.e. carbon microphones and arc lamps) and thanks to its lamellar structure, it is a solid lubricant, typically used in machines that operate at high temperatures.