Abstract: A process for the beneficiation of base metal sulfide mineral values from base metal sulfide ores with selective rejection of gangue sulfide minerals at pH values of below about 10.0 by froth flotation is disclosed. The process includes the use of a new and improved collector which at pH values below 10.0 exhibits unexpectedly high collector activity for base metal sulfide minerals such as copper, lead and zinc and selectively rejects gangue sulfide minerals, such as pyrite and pyrrhotite. The collector for base metal sulfide mineral values for use in the process comprises at least one hydrocarboxycarbonyl thionocarbamate compound having the formula: ##STR1## wherein R.sup.1 is C.sub.1 -C.sub.6 alkyl or phenyl and R.sup.2 is C.sub.1 -C.sub.8 alkyl. In a preferred embodiment of the present invention, the froth flotation is conducted under acid pH conditions by adjusting the pH of the flotation slurry with sulfuric acid.