Magnetic separation method is applicable for the concentration of which of the following ores?

The pair of oxides,which can be leached out when powdered bauxite containing certain impurities is digested with a concentrated solution of $NaOH$ at $473-523 \ K$ temperature and $35-36 \ bar$ pressure,are:

For the purification of alumina,the modern processes most useful when $(i)$ the impurity present is a lot of iron oxides and $(ii)$ the impurity present is a lot of silica,are:

In the extraction of $Al$,the chemical used in Serpeck's process is:

The function of potassium ethyl xanthate in the froth floatation process is to make the ore

The process of ore dressing is carried out to