A kaolinized intrusive body occurring in Precambrian rocks of the Espinhaço (Middle Proterozoic) and Rio Paraúna (Upper Proterozoic?) Groups in the Diamantina region was studied. X-ray diffractometry (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM) and cation exchange capacity (CEC) data have shown that this kaolinite is a well crystallized, non-expansive, chemically purê clay mineral. These studies, together with field observations, suggest that the kaolinite originated by direct precipitation from subsurface solutions deriving from weathering alteration of the aluminosilicate minerais of the basic intrusive rock
