Which of the following magnetic impurity is present in Cassiterite ore?

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:

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:

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

Which of the following is used as a froth stabilizer in the froth flotation process?

What is the product formed when bauxite ore is treated with sodium hydroxide?