Abstract: A process for treating fine minerals, for example clays, to separate therefrom mineral impurities. The fine mineral is conditioned in the form of an aqueous slurry containing a deflocculant, for example sodium silicate, and a collector is added to the aqueous slurry of the mineral which is then subjected to a froth flotation process in a flotation cell having a central, internal, submerged impellor which comprises a base plate, to which there are attached a plurality of blades in radial arrangement, and a stationary cover plate which is separated from the tips of the blades by a small clearance, the impellor being rotated at a peripheral speed of at least 2000 feet/minute.