A large oval complex of about 65 km2 is emplaced into quartzites and phyllites of the Precambrian Bambui Group, which it domes. A thick lateritic cover averages about 150 m in thickness. Drilling has shown the core to consist of carbonatite, pyroxenite, dunite and peridotite. Shonkinites and jacupirangites apparently surround these inner rocks. Pyrochlore, perovskite and baddeleyite occur in the carbonatite and pyroxenite. A little fenitization of the country rocks has been observed.