The process of ore dressing is carried out to

The ore that is concentrated by the froth floatation process is

In the extraction of aluminium:
Process $X$: applied for red bauxite to remove iron oxide (chief impurity).
Process $Y$: (Serpeck's process) applied for white bauxite to remove $Z$ (chief impurity).
Then,process $X$ and impurity $Z$ are:

Observe the following statements regarding the purification of bauxite and select the correct answer.
$(I)$ During the $Hall$ process,silicon is removed in the form of vapor.
$(II)$ Bauxite containing $Fe_2O_3$ impurities is purified by the $Bayer$ process.
$(III)$ $AlN$ is formed during the $Serpeck$ process.

The role of depressants in the Froth Flotation method is to $.....$.

Leaching is commercially carried out for the concentration of which of the following ores?