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
                                                              2 CuFeS2  + O2  Cu2S  + 2 FeS + SO22Cu2S + 3O2  2Cu2O + 2SO22FeS  +  3O2  2FeO + 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 + SiO2     FeSiO3                                   (Slag)