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 .