The mineralogy of the Kalahari Manganese-field north of Sishen, Cape Province

Abstract

The subject matter of this treatise is based on observations of the deposits of manganese ore at the mines Hotazel, Devon, Langdon, Smartt, Adams, Mamatwan and Black Rock which are all in the Kalahario This area is referred to as the Kalahari Manganese-field and the investigation is devoted to the geology and the structure of this field, and in particular to the mineralogy and the geochemistry of the manganese ore and the associated rocks as well as to thermal data on the manganese minerals. It is considered that the rocks of the Upper Griquatown Stage in the Kalahari Manganese-field were deposited in a basin in which the precipitation of manganese was greatly attenuated towards the Korannaberg, the Upper Griquatown Stage of which is correlated stratigraphically with that of the Langberg. The gology of the mines of the Kalahari Manganesefield is described, two geological maps are provided, one for the Kalahari Manganese-field as a whole and one for Black Rock. The mineralogical investigation comprises the main study of this treatise. Altogether 28 minerals are described, some of them in detail. The minerals nsutite, rhodochrosite, ankerite, acmite, cymrite, tremolite, talc and piedmontite have not previously been reported in the rocks of the Upper Griquatown Sta~e of the Kalahari Manganese-field. The mineral cymrite is known from only three other localities els€where in the world. According to the literature there appears to be a close relationship between cymrite and the barium feldsparso Todorokite does not seem to represent replaced asbestos fibre as postulated by many geologists.