Niobium is a critical metal for high-tech and energy transition applications. The processes forming the Brazilian world-class lateritic deposits of Seis Lagos (2.81 wt% Nb2O5) and Catalão-I (1.22 wt% Nb2O5) will be assessed and compared. Unlike the Catalão-I deposit and most Nb deposits worldwide in which pyrochlore is the main ore (type-1 deposits), the Seis Lagos laterite is characterised by an elusive Nb speciation defined by neoformed Ti, Fe and Ce oxides (type-2 deposits) that formed from the alteration of primary Nb minerals to de identified. μ-XAS and μ-XRD spectra will precise Nb speciation in these lateritic deposits. The ore minerals observed in situ will be compared to the Nb average speciation and to the quantitative mineralogy obtained by bulk analyses. Preliminary geochemical and mineralogical analyses will be used to relate our interpretations to the nature of crystal-chemical processes and geochemical conditions required to form either type-1 or type-2 deposits.