Criptomelana cuprífera formada durante o intemperismo das rochas da jazida de cobre do Salobo 3α, Serra dos Carajás

Geochemical and mineralogical studies of the weathering mantle over the copper mineralized rocks of Salobo 3α, Serra dos Carajas, Brazil, show that copper, released from sulfides by dissolution, accumulates in situ, and is mainly located in three mineralogical phases: silicatic, ferruginous and manganesiferous. Only the manganesiferous phase is treated here. It is a cryptomelane phase (hollandite group) with variable potassium contento Diverse methods (X-ray diffraction, infra-red spectrometry, chemical microprobe) show clearly that cryptomelane contains up to 20 % Cu0.