Copper matte contains Cu₂S and FeS. When a blast of hot air is passed through molten matte took in a silica lined convertor, FeS present in matte is oxidized to FeO which combines with Silica (SiO₂) to form FeSiO₃, slag.

When the whole of iron has been removed as slag, some of the Cu₂S undergoes oxidation to form Cu₂O which then reacts with more Cu₂O to form copper metal.