Abstract: The process for converting a copper sulphide matte to blister copper, is achieved by adding the copper sulphide matte and flux to a suitable agitated slag phase; and injecting, from a discharge tip at the lower end of a top-submerged lance, an oxidizing gas suitable for reacting with the matte to produce blister copper which forms or adds to a continuous blister copper phase below the slag phase. The lance tip is located within the slag phase at a depth enabling the injected gas to agitate the slag phase, and to react with copper sulphide matte dispersed therein, while precluding a substantial proportion of the gas from contacting the continuous blister copper phase.