In the extraction of copper from sulphide ore the metal is formed by reduction of Cu₂O with

${\mathrm{Cu}}_2\mathrm{O}$ and ${\mathrm{Cu}}_2\mathrm{S}$ are reduced to form the metal during the extraction of copper from its sulphide ore.
The copper sulphide ore is heated in the presence of air until some of it turns into oxide, and then it is heated again without air to allow the oxide to react with the unaltered sulphide.
Either a Bessemer converter or a Pierce-Smith converter can be used to self-reduce $\mathrm{CuS}$ to$\mathrm{Cu}$.$2{\mathrm{Cu}}_2\mathrm{O}+{\mathrm{Cu}}_2\mathrm{S}\stackrel{\mathrm{\Delta }}{⟶}6\mathrm{Cu}+{\mathrm{SO}}_2$