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

The ore which is purified by the leaching process is

An ore like zinc blende is concentrated by

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

Sulphide ores of metals are usually concentrated by froth floatation process. Which one of the following sulphide ores offers an exception and is concentrated by chemical leaching?

Haematite ore is concentrated by