Potential low-grade iron ore deposits in metamorphosed banded iron formations, Northern Province, South Africa

Exploitation of low-grade iron ore would be quite unique in a South African context as South Africa is well endowed with high-grade iron ore resources. Low-grade iron ore, defined as containing between 20 and 47% iron, is thought to be the primary iron-bearing lithology from which most high-grade ore deposits formed, through different processes of enrichment. The low-grade iron ores in the Northern Province represent meta-banded iron formations (BIFs), with an average iron content of about 36%. The main iron-bearing mineral is magnetite. The Northern Province ores have to be milled to sizes smaller than 150 μm in order to liberate the iron minerals from the host rock, and beneficiation is accomplished through a series of magnetic separation processes. Irrespective of the in situ quality of the ore, final concentrates of exceptionally good quality with more than 69% iron and very low contaminant levels can be produced. This, combined with mass yields of between 40 and 50% and iron recoveries greater than 80%, are excellent for this type of iron ore deposit. The beneficiation products are suitable for use in iron- and steel-making processes. Received: 4 July 1996 / Accepted: 7 January 1997