The Northwest manganese mineralization comprises of supergene ores developed in a weathering crust of the Neoarchean manganiferous dolostones of the Transvaal Supergroup. These are near-surface accumulation of manganese wad and nodules. The manganese wad is preserved in a typical karstic structures on top of the weathered manganiferous dolostones within the Waterval Saprolite. The saprolite is in turn overlain with a sharp erosional contact by West-wits alluvium hosting manganese nodules. Ore formation is attributed to in-situ surficial weathering, partial dissolution and leaching of ore substances from the manganiferous dolostones. These combined processes led to the release of Mn and Fe rich colloidal particles into the overlying water column of the depository, which later precipitated as manganese nodules upon interaction with alluvial sediments which acted as substrates and centers of accretion. This study presents results on the mineralogy, geochemical constituents and geological occurrence of the ore mineralization. Mineralogical studies indicated the occurrence of romanechite, cryptomelane and galaxite as predominant manganese oxide phases, and pyrolusite and vernadite occurring in minute quantities. Geochemical and mineralogical data anomalies obtained in this study were used to develop a genetic classification of the ore deposit. On the basis of trace element geochemistry applied in this study coupled with studies of mineralogical and diagenetic features of the samples, different manganese classification schemes were adopted and inferences were made from the data interpretation which indicated supergene and hydrogenetic nature of the ore mineralization suggesting precipitation of ore substances from the weathered Mn colloids in a supergene zone.