ZnCO3 → ZnO + CO2
2Cu2S + 3O2 → 2Cu2O + 2SO2
Fe2O3·xH2O → Fe2O3 + xH2O
CaCO3·MgCO3 → CaO + MgO + 2CO2
Calcination in carried out for carbonates and oxide ores in absence of oxygen. Roasting is carried out mainly for sulphide ores in presence of excess of oxygen.