The carbonado diamond conundrum

摘要: Abstract The reviewer presents the results of a literature search on enigmatic occurrences carbonado; form (but not only form) polycrystalline diamond, which is mined for industrial diamonds. principal are in Brazil, Central African Republic (CAR) and Siberia (Yakutia). In latter name yakutite has been coined, but, though there differences between these diamonds Brazil/CAR minerals, they would seem to be little more significant than within ‘Gondwana’ occurrences, ‘yakutite’ should probably regarded as another carbonado. Most placers minerals have recycled once by sedimentary processes, ultimate source being unknown. Polycrystalline diamond described from Udachnaya pipe, Yakutia and, it strictly framesite (defined an eruptive pipe variety carbonado), differs other carbonados. fact that all known areas with kimberlites gem developments present, suggests carbonado does stem terrestrial necessarily kimberlite pipes. Nevertheless, this can provisional, personal conclusion, much contradictory evidence literature. subjection radiogenic agencies CAR carbonados seems unexplained, but may secondary effect present This conundrum still calls research.