Which of the following ores is concentrated by the process of leaching?

Bauxite containing impurities of iron oxide is purified by

Which of the following ores cannot be concentrated by the froth flotation method?

Given below are two statements :-
Statement $I$: In froth floatation method,a rotating paddle agitates the mixture to draw air into it.
Statement $II$: Iron pyrites are generally avoided for the extraction of iron due to environmental reasons.
In the light of the above statements,choose the correct answer from the options given below :-

The ore which is concentrated by wetting with oil is:

Collectors are the substances which help in attachment of an ore particle to air bubble in froth. $A$ popular collector used industrially is