A process for separation of at least one metal sulfide from a mixed sulfide concentrate, the mixed sulfide concentrate having at least one sulfide comprising antimony, arsenic and at least two metals, the at least two metals comprising a first metal and a second metal, the process comprising: subjecting the mixed sulfide concentrate to flotation in which at least one sulfide comprising antimony, arsenic and the first metal is floated and at least one sulfide comprising the second metal is depressed, the flotation yielding a first metal concentrate and a second metal concentrate, the first metal concentrate having the at least one sulfide comprising antimony, arsenic and the first metal, and the second metal concentrate having the at least one sulfide comprising the second metal, wherein the second metal concentrate has at least 50% of the original antimony, the arsenic, and the first metal content of the mixed sulfide concentrate removed; leaching the first metal concentrate to yield a further metal concentrate and a leach solution, the further metal concentrate comprising the first metal and the leach solution comprising soluble antimony and soluble arsenic; and one of: (i) oxidizing the leach solution to yield an antimony precipitate and an arsenic solution; and (ii) oxidizing the leach solution to yield an antimony precipitate and an arsenic solution, and forming a stable arsenic compound from the arsenic solution, wherein said oxidizing the leach solution comprises oxidizing the soluble arsenic and antimony in the leach solution to yield soluble antimony and arsenic thiosalts; and removing the soluble antimony and arsenic thiosalts from the leach solution by crystallization, wherein said crystallization comprises forming thioarsenate and thioantimonate salts. subjecting the mixed sulfide concentrate to flotation in which at least one sulfide comprising antimony, arsenic and the first metal is floated and at least one sulfide comprising the second metal is depressed, the flotation yielding a first metal concentrate and a second metal concentrate, the first metal concentrate having the at least one sulfide comprising antimony, arsenic and the first metal, and the second metal concentrate having the at least one sulfide comprising the second metal, wherein the second metal concentrate has at least 50% of the original antimony, the arsenic, and the first metal content of the mixed sulfide concentrate removed; the first metal concentrate having the at least one sulfide comprising antimony, arsenic and the first metal, and the second metal concentrate having the at least one sulfide comprising the second metal, wherein the second metal concentrate has at least 50% of the original antimony, the arsenic, and the first metal content of the mixed sulfide concentrate removed; leaching the first metal concentrate to yield a further metal concentrate and a leach solution, the further metal concentrate comprising the first metal and the leach solution comprising soluble antimony and soluble arsenic; and one of: (i) oxidizing the leach solution to yield an antimony precipitate and an arsenic solution; and (ii) oxidizing the leach solution to yield an antimony precipitate and an arsenic solution, and forming a stable arsenic compound from the arsenic solution, wherein said oxidizing the leach solution comprises oxidizing the soluble arsenic and antimony in the leach solution to yield soluble antimony and arsenic thiosalts; and removing the soluble antimony and arsenic thiosalts from the leach solution by crystallization, wherein said crystallization comprises forming thioarsenate and thioantimonate salts. (i) oxidizing the leach solution to yield an antimony precipitate and an arsenic solution; and (ii) oxidizing the leach solution to yield an antimony precipitate and an arsenic solution, and forming a stable arsenic compound from the arsenic solution, wherein said oxidizing the leach solution comprises oxidizing the soluble arsenic and antimony in the leach solution to yield soluble antimony and arsenic thiosalts; and removing the soluble antimony and arsenic thiosalts from the leach solution by crystallization, wherein said crystallization comprises forming thioarsenate and thioantimonate salts.