Amongst the following, how many ores can be concentrated by froth  flotation  process : Galena,  sphalerite,  cassiterite,  calamine, chalcocite,  haematite,  argentite

Three, i.e., galena , sphalerite , chal- cocite .  Although argentite (Ag2S) is a sulphide ore, it is not concentrated by froth floatation process since its silver content is low. It is better concentrated by leaching with NaCN.