Q.Which one of the following ores is best concentrated by froth-floatation method?

Sulphide ores (like galena, zinc blende, copper pyrites) are concentrated by the froth flotation process, which exploits the preferential wetting of sulphide particles by oil.

In froth flotation, the powdered ore is mixed with water and a small quantity of pine oil (collector/frothing agent) in a large tank. Air is blown through the suspension. The sulphide ore particles are preferentially wetted by the oil and stick to the air bubbles, rising to the surface as a froth, which is skimmed off; the unwanted gangue (silicate/earthy impurities) is wetted by water and settle …

Concentration means separating and discarding the gangue (unwanted rocky/earthy matter) from the ore so the metal-bearing mineral is enriched before metallurgical extraction.

An ore as mined is never pure — it is mixed with sand, clay, and other rocky impurities collectively called gangue. Before a metal can be extracted economically, this gangue must be removed as far as possible. This step is called concentration or ore-dressing.

The method chosen depends on the physical/chemical differences between the ore particles and the gangue, e.g.:

• Hydraulic washing / gravity separation — for ores denser than gangue.
• Magnetic separation — for magnetic ores like magnetite. …