What is the function of flux during the smelting of an ore?

What is the role of cryolite in the metallurgy of aluminium?

Which process is used for the extraction of copper from low-grade copper ores?

In the extraction of copper from its sulphide ore,metal is finally obtained by the oxidation of cuprous sulphide with

In the metallurgy of zinc,the zinc dust obtained from roasting and reduction of zinc sulphide contains some $ZnO$. How is this removed?

Low grade $Cu$ ores are available and $Zn$ and $Fe$ scraps are also available. Which scrap among the two would be more suitable for reducing the leached $Cu$ ore (economically)?