After more than 80 volumes of Reviews in Mineralogy and Geochemistry (RiMG), we now have a volume on diamond—Diamond: Genesis, Mineralogy and Geochemistry. Diamond is the record-setter in many mineralogical properties such as hardness, diffusivity, thermal conductivity, purity, and covalency of bonding. Similarly, diamond, as the premier gemstone of the mantle holds primacy for geological features such as age and depth of origin. Diamond was among the first crystalline structures to be solved by X-ray diffraction and the first materials measured for their Raman spectrum. The second issue of the multi-society journal Elements was devoted to diamonds. At more than 80 billion USD in yearly commercial value, diamond sets the record for the most traded, valuable mineral on the planet. Despite its chemical simplicity, diamond has been the object of more research effort, and had more scientific and popular press pages written about it, than any other mineral. How odd it is then that a RiMG volume on diamond took fifty years to be published! Here we address that shortcoming.