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Roasting is the process ofconverting sulphide ores to oxides by heating the ores in a regular supply ofair at a temperature below the melting point of the metal. For example,sulphide ores of Zn, Pb, and Cu are converted to their respective oxides bythis process.
On the other hand, calcination isthe process of converting hydroxide and carbonate ores to oxides by heating theores either in the absence or in a limited supply of air at a temperature belowthe melting point of the metal. This process causes the escaping of volatilematter leaving behind the metal oxide. For example, hydroxide of Fe, carbonatesof Zn, Ca, Mg are converted to their respective oxides by this process.
