The final step for extraction of copper from copper pyrite in bessemer converter involves the reaction

In Bessemer converter, copper-sulphide is partially oxidised to cuprous oxide, which further reacts with the remaining copper sulphide to give copper and sulphur di oxide, i.e. ${\mathrm{Cu}}_2 \mathrm{S}+2{\mathrm{Cu}}_2\mathrm{O}⟶6\mathrm{Cu}+{\mathrm{SO}}_2$

This reaction represents auto reduction. ${\mathrm{Cu}}_2\mathrm{O}$ reacts with ${\mathrm{Cu}}_2\mathrm{S}$ to give copper metal. The solid metal obtained is called as blister copper and is about 99% pure.