What are roasting and calcination?

Explanation

Roasting : Roasting is the method, usually applied for the conversion of sulphide ores into their oxides. In this method, the concentrated ore is oxidized by heating it with excess of oxygen in a suitable furnace below the melting point of the metal.
Calcination : It is the process in which the concentrated ore is strongly heated in the absence of air. Hence ore is converted into their oxides.