Apparatus for separating the organic membrane portion and the non-organic mineral portion of broken egg shells includes at least one separating tank into which a slurry of water and finely ground egg shells is introduced. A plurality of overlapping vanes is in the interior of the tank. Separated low specific gravity membrane is withdrawn from near the top of the tank for dewatering and drying; the separated high specific gravity mineral portion is withdrawn from near the bottom of the tank for drying. Water from the dewatering means is returned to the bottom of the tank with sufficient force to cause an upward serpentine flow past the vanes, but not so as to preclude the settling of the mineral portion.