A dry differential flotation reagent for molybdenum-bearing ore is disclosed comprising from about 1 to about 30 percent by weight of NaSH, 0 to 20 percent by weight of NaOH, 60 to 90 percent by weight of a mixture of sodium thiophosphates comprising, as major components thereof, Na.sub.3 PS.sub.4, Na.sub.3 PS.sub.3 O, Na.sub.3 PS.sub.2 O.sub.2, and Na.sub.3 PO.sub.3 S, with Na.sub.3 PS.sub.4 further comprising from about 15 mole percent to about 70 mole percent of the phosphate mixture. The flotation reagent can be prepared by reacting P.sub.4 S.sub.10 with NaOH and NaSH in a molar ratio of about 1:16. When added to a flotation vessel containing molybdenum concentrate, the flotation reagent promotes suppression of lead and copper sulfides, even without the addition of sodium cyanide, to permit the improved recovery of molybdenum with a lower level of impurities.
