Carbonado has been dated directly. After acid treatment to remove all non-diamond material, Ozima and Tatsumoto analyzed Central African stones by mass spectrometry and Sano and colleagues analyzed Brazilian stones by ion probe; both reported ages of 2.6 to 3.8 billion years based on implanted radiogenic lead[1,2]. Haggerty notes the method is unconventional but that the Archean result agrees with trapped crustal inclusions of zircon, rutile and quartz and with the 3.3–3.7-billion-year basement of the São Francisco craton[1].
Its carbon is isotopically light, with δ¹³C reported between about −21 and −34 per mil[1].
Both deposits sit on cratons, the ancient, stable cores of continents: the São Francisco craton in Brazil and the Congo craton in Africa[1]. According to Haggerty, these blocks shared a common geological setting for more than a billion years, within the supercontinent Rodinia and its predecessor Nuna, also called Columbia[1]. Alkmim and colleagues describe a “São Francisco–Congo cratonic bridge” that remained intact until the Cretaceous[3].
This is the best-supported chapter of the timeline. The ages, the cratons and their former union are matters of published record; what remains unresolved is how carbonado came to be there.