Abstract: The zinc slag from a lead and zinc smelter has complex chemical composition. Each metallic mineral has a mutual metasoniatism and a close disseminated relationship. The main useful element contains silver of 267.00 g/t in complex occurrence. 65.43% of silver occurs in the form of plumbojarosite, resulting in difficulty to realize direct flotation. The technical conditional tests are made for the zinc slag processed by the chemical heat decomposition. The results show that under the optimum conditions, silver concentrate with silver grade of 5 434.00 g/t and recovery of 72.59% were obtained by adopting the process of one-roughing, one cleaning, one scavenging and middles back to the flow-sheet in turn.

Key words: Zinc slag, Silver, Plumbojarosite, Thermal decomposition, Flotation