Crushing of the Ore
The big lumps of ore are crushed into smaller pieces with the help of jawcrushers. The process of grinding the crushed ore into fine powder with the help of the stamp mills is called pulverisation.
Concentration of Ores
Removal of unwanted materials( e. g., sand. clays, etc.) from the ore is known as ore concentration, ore dressing or ore benefaction. It can be carried out by various ways depending upon the nature of the ore.
Hydraulic Washing / Gravity Separation / Levigation
The process by which lighter earthy impurities are removed from the heavier ore particles by washing WIth water is called levigation. The lighter impurities are washed away. Thus. this method is based on the difference in the densities( specific gravities) of ore and gangue.
This method is commonly used for oxide ores such as haematite, tin stone and native orcs of Au, Ag, etc.
Froth Floatation
This method is used for the concentration of sulphide ores. This method is based on the preferential wetting of ore particles by oil and that of gangue by water.. As a result. the ore particles become light and rise to the top in the form of froth while the gangue particles become heavy and settle down. Thus. adsorption is involved in this method.
The froth can be stabilised by the addition of stabilisers( aniline or cresols).
Activator They activate the floating property of one of the component of the ore I and help in the separation of different minerals present in the same ore( CuSO4 is used as activator.
Depressants These are used to prevent certain types of particles from forming the froth with air bubbled, e. g., NaCN can be used as a depressant in the separation of ZnS and PbS ores. KCN is an another depressant.