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

Wolframite ore is separated from tinstone $(SnO_2)$ by which of the following processes?

Chemical leaching is useful in the concentration of

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:

An ore containing the impurity of $FeCr_2O_4$ is concentrated by

Which of the following is used as a stabilizer during the concentration of sulphide ores?