Abstract: In a process for controlling the product composition in an apparatus for sizing and sorting mineral raw materials, wherein the apparatus comprises at least one chamber, a sizing separation of the sand fraction into a sand product mass and into a micro particle sand fraction to be discharged via the overflow, is additionally performed in the chamber by means of the level of the fluidized bed in the chamber. For the adjustment of a pre-set concentration of micro particle sand in the sand product mass, the fluidized bed level is controlled such that the micro particle sand fraction in the supplied raw material mass is divided, by means of the fluidized bed, as a function of the pre-set admissible concentration into a micro particle sand fraction to be discharged into the sand product mass and a micro particle sand fraction to be discharged via the overflow.