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Introduction
The Iron Ore Division is made up of the high grade Khumani Mine situated on the farms Bruce, King, Mokaning and Parsons located near the town of Khatu, as well as the Beeshoek Mine situated on the farms Beeshoek and Olynfontein located outside the small town of Postmasburg. Both mines are located in the Northern Cape Province of South Africa, approximately 200 kilometres west of the town of Kimberley.
Location
The Khumani open pit operations are adjacent to, and south east of, the Sishen Mine, located at a latitude 27°45'00''S/longitude 23°00'00''E, while the Beeshoek open pit operations are situated approximately 7 kilometres west of the town of Postmasburg, located at a latitude 28°30'00''S/longitude 23°01'00''E.
Geology
The iron ore deposits are contained within a sequence of early Proterozoic sediments of the Transvaal Supergroup deposited between 2 500 and 2 200 million years ago. In general, two ore types are present, namely laminated hematite ore forming part of the Manganore iron formation and conglomerate ore belonging to the Doornfontein Conglomerate Member at the base of the Gamagara Formation.
The older laminated ore types occur in the upper portion of the Manganore Iron Formation as enriched high-grade hematite bodies. The boundaries of the high-grade hematite ore body crosscuts primary sedimentary bedding, indicating that secondary hematisation of the iron formation took place. In all of these, some of the stratisgraphic and sedimentological features of the original iron formation are preserved.
The conglomeratic ore is found in the Doornfontein Conglomerate Member of the Gamagara Formation and is lenticular and not persistently developed along strike. It consists of stacked, upward fining conglomerate-grit stone shale sedimentary cycles. The lowest conglomerates and grit stones tend to be rich in sub rounded to rounded hematite ore pebbles and granules and form the main ore bodies. The amount of iron ore pebbles decreases upwards in the sequence so that upper conglomerates normally consist of poorly sorted, angular to rounded chert and banded iron formation pebbles.
The erosion of the northern Khumani deposit is less than that in the southern Beeshoek area. The result is that Khumani is characterized by larger stratiform bodies and prominent hanging wall outcrops. The down-dip portions are well preserved and developed, but in outcrop the deposits are thin and isolated. Numerous deeper extensions occur into the basins due to karst development. A prominent north-south strike of the ore is visible. The southern Beeshoek ore bodies were exposed to more erosion and are more localized and smaller. Outcrops are limited to the higher topography on the eastern side of the properties. Down-dip to the west, the ore is thin and deep. The strike of the ore bodies is also in a north-south direction, but less continuous. Hematite is the predominant ore mineral, but limonite and specularite also occur.