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

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

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

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