MAMATWAN, an open-pit manganese mine, is part of BHP Billiton's subsidiary, Samancor Manganese, With benches varying from 5 to 45 m, the company was encountering serious overhang and highwall stability problems on the high 'lime' horizon as well as the manganese benches. There are four main rock layers: Sandstone (referred to as top lime). Limestone (mid-lime). Waste manganese (top-cut). Manganese (middle-cut). The height of the three layers of waste on the manganese is 50-90+ m and is removed in three benches of +/-10 m of sandstone, +/-45 m of limestone and 2-40 m of waste manganese. The mine has started to split the mid-lime benches in the southern part of the mine owing to the identification of a dangerous situation with the mine's risk assessments. Mamatwan is also planning to start splitting the northern mid-lime benches for the same reason. The manganese is an orebody of about 22 m that is removed, 60 percent is sintered, 40 percent beneficiated and then railed out.
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