Give one word or a phrase for the statement : The process by which sulphide ore is concentrated.

Fill in the blank with the correct choice given in the bracket - The most common ore of iron is ……………[calamine/haematite]

Name the most common ore of the metal aluminium from which the metal is extracted. Write the chemical formula of the ore.

Name the process by which impure ore of aluminium gets purified, by a conc. soln. of an alkali.