Author name: George E. Harlow

Active research on diamond, a carbon mineral with superlative proper- ties, extends into many realms of natural and material sciences. Extreme hardness and transparency make diamond a valuable gem and a high-pressure research tool, as well as a superabrasive. Natural forma- tion at high pressure and resistance to weathering make diamonds our most informative messengers from Earth’s mantle. A review of diamond’s charac- ter and forms leads into the topics of the articles in this issue of Elements.