Magnetic separation is used for increasing the concentration of which of the following ores?

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?

Which of the following ores is most commonly concentrated by the froth flotation process?

For the purification of alumina,the modern processes most useful when $(i)$ the impurity present is a lot of iron oxides and $(ii)$ the impurity present is a lot of silica,are:

The substance which is mixed with the ore for the removal of impurities is termed as

Chemical leaching is useful in the concentration of