A grinding, separating, and discharging of hard to grind parts of a material mixture of components with different grindability from a spiral jet mill, wherein the hard to grind parts are discharged from the process chamber via at least one additional discharge nozzle. A spiral jet mill for comminuting and classifying grinding material, including at least one process chamber, wherein this at least one process chamber is enclosed by a housing, at least one grinding material feeding, which leads into the at least one process chamber, at least two grinding nozzles, a fine material outlet, which is radially enclosed by a separator wheel, wherein at least one discharge nozzle is assigned to the process chamber.