Sulphide ores of metals are usually concentrated by Froth floatation process. Which one of the following sulphide ores offers an exception and is concentrated by chemical leaching? (AIPMT 2007)

Froth floatation is used for the concentration of ore. This process is based on the fact that gangue particles are wetted by water and oils whereas ores are not. However, this process is not used for the concentration of argentite. For argentite, treatment with NaCN i.e. cyanide process is used.Chemical leaching is involved METALLURGY 48 in the concentration of Argentite ore and the reactions are given below- 2 2 2 4 2 [ ( ) ] Ag S NaCN Na Ag CN Na S -> Therefore, the correct answer is option (b) argentite.