Abstract: A hopper has an adjustable opening into a tube that leads to the interior of a drum-shaped housing containing a grinding impeller that also functions simultaneously as a screw-type fan and as a paddle-type fan, formed to maximize air turbulence at the grinding edges thereof and to separate finely ground material from the coarser particles continuously. The grinding impeller is operated by a motor attached to the outside of the drum-shaped, grinder housing. The impeller is adjustable relative to a dam that partially surrounds a discharge port in one end of the housing. The dam intercepts air from the vortex created by the impeller, to promote flow of material through the discharge port. A tube leads from the discharge port to a separating device above a drawer having a partition therein, so that the coarse material may be dropped into one compartment and the fine material into the other.