Which one of the following is not an example of calcination?

Calcination is the process of heating an ore in the absence of air (or limited supply of air) to remove volatile substances like water, CO₂, etc.

Option 1: CaCO₃ → CaO + CO₂: This is calcination (removal of CO₂). ✓

Option 2: Fe₂O₃·xH₂O → Fe₂O₃ + xH₂O: This is calcination (removal of water). ✓

Option 3: 2PbS + 3O₂ → 2PbO + 2SO₂: This is roasting (heating a sulphide ore in the presence of oxygen/air). ✗ NOT calcination.

Option 4: CaCO₃·MgCO₃ → CaO + MgO + 2CO₂: This is calcination. ✓

The answer is option 3, which is roasting, not calcination.