Managing uncertainty in a Grade Engineering® industrial pilot trial

Preferential grade by size deportment, one of the Grade Engineering® coarse size based separation levers, aims to remove low grade uneconomic material through screening prior to energy intensive and inefficient grinding. Deposit amenability to this coarse separation technique requires an integrated characterisation program involving a carefully designed sampling strategy. A key aspect within this process is the preferential grade by size industrial pilot trial. This paper outlines the screening of 40,000 tons of Run of mine (ROM) material from a word class Cu-porphyry deposit from an area identified as amenable to coarse preconcentration by size based on geometallurgical characterisation, and investigates three sources of uncertainty upon preferential grade by size pilot trial results. Screen efficiency, fundamental sampling errors and the mathematical model employed describing preferential grade by size response are analysed. This methodology recognises the difference between uncertainties associated with preferential grade by size response measurement and variability related to intrinsic geological characteristics. This novel approach aids the optimisation and development of coarse separation control strategies through the understanding of the extent, variability and uncertainty of metal deportment inputs.