Method of depressing non-sulfide silicate gangue minerals

A method which comprises beneficiating value sulfide minerals from ores with selective rejection of non-sulfide silicate gangue minerals which comprises:

• a. providing an aqueous pulp slurry of finely-divided, liberation-sized ore particles which contain said value sulfide minerals and said non-sulfide silicate gangue minerals;
• b. conditioning said pulp slurry with an effective amount of non-silicate gangue mineral depressant, a value sulfide mineral collector and a frothing agent, said depressant comprising a polymer of polyvinylalcohol onto which is grafted an acrylamide and, optionally, a comonomer copolymerizable with said acrylamide, and
• c. subjecting said conditioned pulp slurry to froth flotation and collecting the value sulfide mineral having a reduced content of non-sulfide silicate gangue minerals.