6.9 State the role of silica in the metallurgy of copper.

During the roasting of pyrite ore, a mixture of FeO and Cu2O is obtained
                                                              2CuFeS2+O2Cu2S+2FeS+SO2
2Cu2S+3O22Cu2O+2SO2
2FeS+3O22FeO+2SO2

The role of silica in the metallurgy of copper is to remove the iron oxide obtained during the process of roasting as ‘slag’. If the sulphide ore of copper contains iron, then silica (SiO2) is added as flux before roasting. Then, FeO combines with silica to form iron silicate, FeSiO3(slag).
                      FeO+SiO2FeSiO3
(Slag)