The Northwest manganese ore mineralisation is located at a relative distance from traditionally known manganese mining areas in a new manganese-bearing region (Highveld) in the Northwest Province, Republic of South Africa. The ore occurrence was studied on farms: Buchansvale 61 IQ, Weltevreden 517 JQ, Rhenosterhoek 343 JP and Kafferskraal 306 JP. The data obtained from studying the geology of the area pointed out to interests regarding the development criterias for search of similar ore mineralisations in the northwest region of South Africa. The ore occurs predominantly in the form of powdered manganese wad, manganese nodules and crusts, confined to the karstic structures of the upper section of the dolomites. X-ray powder diffraction (XRD), Scanning electron microscopy with energy dispersive link (SEM-EDS) and X-ray fluorescence were utilized to unveil the mineral and chemical composition of the ore samples. The present study therefore presents the results on both chemical and mineral composition of manganese ores, and their depth and longitudinal distribution. Karstic areas causing an increased local thickness of the ore body were identified. The geochemical and microspcopic study of the ores indicates their supergene nature. The main ore minerals includes cryptomelane, lithiophorite, purolusite, hollandite and romanechite associated with impurity components of Ba, Ce, Co, La, Cr, Zn and V.
MANGANESE MINERALISATIONS AT THE BASE OF MIOCENE SEDIMENTS IN NORTHERN SARDINIA (ITALY)