a method for the treatment of a kaolin clay crude to separate by selective flocculation impurity particles contained in the crude from finely divided kaolinite particle contained in the crude , comprising : forming said crude into a dispersed aqueous slurry b adding water and at least one dispersant to said crude ; conditioning said dispersed aqueous slurry by adding conditioning chemical thereto , the conditioning chemical providing addition of monovalent cations to the slurry without adding multivalent cations thereto ; selectively flocculating said conditioned slurry by adding to said conditioned slurry a composition comprising a high molecular weight component comprising an organic anionic polymer having a molecular weight of at least 1 million ; and a low molecular weight component comprising an inorganic anionic polyphosphate ; said composition causing impurity particles in said slurry to flocculate and settle as a dense lower layer and kaolinite particles in said slurry to be deflocculated and concentrated in an upper layer above said lower layer ; and separating said lower layer and said upper layer ; and wherein the use of said composition in step increases the yield of said kaolinite particles in said upper layer .