a ph value in the range of about 5 to 7 the ore feed is finely divided and the feed to the cleaner and recleaner flotation stages is normally reground to further liberate the desired mineral in zinc sulfide flotation using conventional depressants regrinding must be carried out to a degree such that about 80 of the solids in the flotation feed slurry are smaller than about 19 micron in order to obtain a satisfactory gangue rejection in the tailing when using the present depressants however we have found that regrinding to a degree whereby 80 of the particles are smaller than about 27 micron 80 lt 27 u03bc is sufficient for depressing the gangue materials in the tailing to give a zinc sulfide concentrate containing less than about 1 5 silica the coarser regrind also effects lower energy requirements and yields zinc sulfide concentrates that are acceptable to more smelters the invention will now be illustrated by means of the following nonlimitative examples a sample of a lead zinc and iron containing complex sulfide ore from alaska containing gangue materials including 47 silica and quartz was ground and subjected to froth flotation operations to obtain a lead sulfide concentrate and a zinc sulfide rougher concentrate using reagents conventionally used to obtain such concentrates the zinc sulfide rougher concentrate comprised 36 21 by weight of the original ore sample and assayed 3 1 pb 44 9 zn and 6 4 fe.