Sulphide ores are typically concentrated using the froth flotation method. This method is highly effective for separating sulphide minerals from gangue (impurities) because sulphide ores are generally hydrophobic and tend to attach to oil froths, while the gangue particles remain in the water phase. In this process:
Other methods such as washing, hand picking, and magnetic separation are not suitable for sulphide ores:
Final Answer: The most suitable method for the concentration of sulphide ores is \( \mathbf{\text{froth flotation}} \), which corresponds to option \( \mathbf{(3)} \).