Diamond

Abstract

“Diamonds are Forever” according to the 1956 Ian Fleming novel, which was made into a film in 1971, about the British secret agent James Bond. Diamonds may last an awfully long time but they are not forever. Diamond is a metastable (long-lived, but not equilibrium) crystalline form of carbon that has a crystal structure referred to as diamond cubic, which is also adopted by both silicon and germanium. The stable or equilibrium form of carbon is graphite, the stuff in the middle of your “lead” pencil. However, not to worry, even though diamonds are only metastable, if kept at room temperature it will likely take billions of years before they turn into graphite. On the other hand, they will burn if heated to 850–1000 °C generating the far less valuable greenhouse-gas carbon dioxide.