The aim of the paper is to investigate the effect of the collector dosage on the Zn Rougher performance based on the mass balance of the liberated and locked particle types. Two sampling surveys were conducted in different periods of the collector dosage adjustments. In the high and low dosage limits, the feed, tail and bulk concentrates together with each cell concentrate were sampled and sized in narrow size fractions to facilitate quantitative mineralogical analysis. The metallurgy of the existing, high and low dosage cases was calculated using mass balance. Mineral balancing of the liberated and locked particles was also performed around the bank. The sphalerite was lost to the tail, even in liberated form, with over 21.5% of coarse size in low dosage. Increasing the dosage of the collector did not much affect the liberated pyrite and non-sulphide gangue (NSG) particles, except for finer sizes, which indicated the occurrence of recovery by entrainment. Because sphalerite was mostly locked with pyrite, the amount of sphalerite-pyrite binaries was 21 to 28% higher in the size fractions of the high case. Therefore, it was also concluded that increasing the dosage of the collector in the rougher bank was necessary to collect sphalerite locked particles. (C) 2014 Elsevier B.V. All rights reserved.