Ore Reserve Estimation with Special Reference to Opencast Mines—An Overview

Ore reserve estimation is normally carried out in different stages depending upon the purpose. In the preliminary exploration stage the mean and variance of the deposit are studied, the global estimation variance are determined, and the optimum drilling grid at global level is tested. In the project planning and development stage, testing the reliability of the estimates, kriging of the blocks of a given size, determination of the recoverable reserves, drawing of grade-tonnage curves for a given block size, and pit optimisation using different methods are carried out. In production stage, kriging of small blocks, if necessary by using blast-hole drilling information, and calculation of local recoverable reserves of bench by using disjunctive kriging is recommended. When compared to the traditional methods of calculation of reserves by cross-sections, bench plans, polygonal methods, and inverse distance square, geostatistical linear and non-linear methods are advantageous.