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Ore selection and sequencing.

CET Seminar Series

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Jim Everett

A block model of an ore body is used to plan a mine. Ore blocks are first selected, ideally to optimise Net Present Value, but more usually so as to meet target grade, generally in multiple analytes. Commonly, cut-off values for each analyte are used to distinguish ore from waste. However, if more than one analyte is important, this quadrant procedure is wasteful of ore and a composite cut-off function is preferable. A second requirement is to sequence the ore extraction so that the variability in ore grade is controlled: failure to do so will result either in low-quality ore being marketed, or excessive re-handling being required to blend the ore to reduce the grade variability. A third requirement is that the extraction sequence should be such as to limit the amount of movement of equipment to enhance productivity. The discussion will centre on the mining of iron ore, but the issues are relevant to a wide variety of mining situations.