Diamonds are the dense quintessence of carbon. Carried near the surface in eruptions of rock from the mantle from below 100 km, diamonds are scientifically significant because they prove the existence of Earth's deep carbon. They also matter because the bubbles or inclusions in them hold precious evidence about Earth at depths that are otherwise inaccessible. This grant funds an initiative led by Steven Shirey of the Department of Terrestrial Magnetism of the Carnegie Institution of Washington to form an international group of diamond researchers that aspires to take diamond research in new directions beyond the traditional bounds of geology, physics, and chemistry. Tapping a group of more than 30 researchers from a dozen nations, the consortium aims to forge a new understanding of the conditions of diamond formation in the deep mantle, how carbon is transported and stored in the mantle now and in the past, and whether a significant reservoir of mantle carbon is primordial or recycled. Grant funds will support the development of consortium organizational infrastructure; the assembly of an internationally accessible diamond reference collection for collaborative research; outreach activities to potential partners in government, academia, and industry; and the creation of information sharing technologies to facilitate cooperation between members. The consortium has the potential to revolutionize our understanding of diamonds and the role they play in the deep mantle and to augment and inform the scientific agenda of the Deep Carbon Observatory.