Comminution (crushing and grinding) represents a minimum of 10% of total site production costs, and 53% of energy consumption (CEEC, 2020), and yet due to complexity in estimating specific energy, variable orebody comminution costs are rarely included in mine optimisation, or scheduling. Specific energy is a measure of the amount of energy (kW) required to liberate minerals per tonne of ore processed, it is denoted kWh/t. Estimating specific energy for the purpose of mine scheduling and optimisation is complicated because it requires simultaneous consideration of both the mechanical strength properties of rock, as well as the ‘grind size’ required to liberate the ore minerals from gangue minerals. Furthermore, it is common for metallurgists to ‘optimise’ grind size over the life of the mine, however grind size is not compatible with mine optimisation and scheduling as it is a non-additive ore characteristic which means tonnes weight averaging for block model combinations is not valid.