A process is provided for separation of at least one metal sulfide from a mixed sulfide concentrate. The process includes: subjecting the mixed sulfide concentrate to flotation in which at least one sulfide including antimony, arsenic and a first metal is floated and at least one sulfide including a second metal is depressed. The flotation yields a first metal concentrate having the at least one sulfide including antimony, arsenic and the first metal and a second metal concentrate having the at least one sulfide including the second metal. The first metal concentrate is leached to yield a further concentrate and a leach solution. The further concentrate includes the first metal and the leach solution includes soluble antimony and soluble arsenic. The process further includes oxidizing the leach solution to yield an antimony precipitate and an arsenic solution, and forming a stable arsenic compound from the arsenic solution.