Abstract: A process is disclosed for treating mixed metal sulfides containing trivalent antimony sulfide wherein the sulfide concentrates are leached with an excess of sodium sulfide in order to isolate copper sulfide and other insolubles in solid form while solubilizing the remaining metal sulfides and producing sodium thioantimonite, separating the insoluble sulfides from the solution; oxidizing the sodium thioantimonite with elemental sulfur to produce sodium thioantimonate in solution; crystallizing a portion of the sodium thioantimonate along with other available metal sulfides from solution; and recirculating the remainder of the solution to the sodium sulfide leach stage. The crystallized metal sulfides may be further treated, isolated, and recovered as desired.