Understanding Gamsberg – A geometallurgical study of a large stratiform zinc deposit

The Gamsberg zinc deposit in the Northern Cape in South Africa has been the subject of a number of studies by Anglo American over the years. Two distinct ore types have been identified, namely pelitic and garnet-magnetite ore. The ore is characterised by relatively high manganese levels. Manganese reporting to the flotation concentrate is problematic for downstream refining.Anglo Research was asked by the exploration division of Anglo Base to study the relationship between the mineralogy and the floatability of the ore from reef intersections obtained from the eastern ore body. The two ore types were found to have different mineralogical characteristics resulting in different flotation responses both in terms of zinc and manganese recoveries and concentrate grades.The presence of the manganese sulphide, alabandite, was also established, and was found to be extremely detrimental to sphalerite flotation. The reasons for this were explained using the surface analysis facility at Anglo Research.