In the Serpek process for the purification of bauxite,what is used to remove silicon dioxide?

The method of concentrating the ore which makes use of the difference in density between ore and impurities is called:

$A$ process used for the concentration of ore is

Explain the leaching of:
$(i)$ Alumina from Bauxite (Bayer's Process)
$(ii)$ Gold and Silver (Cyanide Process)

Given below are two statements :
Statement $I :$ Sphalerite is a sulphide ore of zinc and copper glance is a sulphide ore of copper.
Statement $II :$ It is possible to separate two sulphide ores by adjusting proportion of oil to water or by using 'depressants' in a froth flotation method.
Choose the most appropriate answer from the options given below :

If bauxite contains $SiO_2$ as an impurity,which of the following methods can be used for its purification?