FREMGANGSMAATE VED RENSING AV KALSIUMKARBONATHOLDIGE MINERALER

There is disclosed a process for purifying a calcium carbonate-containing mineral which process comprises the following steps:- a) mixing the calcium carbonate-containing mineral with water and a dispersing agent to form a suspension containing from 60% to 80% by weight of the dry mineral; b) comminuting the suspension of calcium carbonate-containing mineral prepared in step a) to give a product containing not more than 5% by weight of particles which are retained on a sieve having a nominal aperture of 53 microns and not more than 50% by weight of particles which are smaller than 2 microns e.s.d.; c) subjecting the suspension containing from 60% to 80% by weight of the dry comminuted mineral prepared in step b) to froth flotation using a collector for disclouring impurities which colletor comprises a cation containing at least one long chain alkyl group having from 10 to 24 carbon atoms, to yield an underflow product containing the calcium carbonatecontaining mineral from which substantially all discolouring impurities have been removed; and d) further comminuting the underflow product of step c) to give a material of which at least 40% by weight of the particles have an equivalent spherical diameter smaller than 2 microns. g