Abstract: A vertical ball mill for grinding a solid input material to form a slurry, and includes a grinding tank which defines a mixing chamber, rotatable main auger assembly having mixing blade in a lower portion of the mixing chamber and a materials flow guide. The flow conduit is provided within the grinding tank interior, and includes one or more conduit segments configured to direct input material downwardly in the grinding tank towards the lower mixing chamber and auger mixing blade. An impeller is provided within the flow conduit, with a blade configuration selected to effect the downward flow of input material through the conduit segments and outwardly therefrom adjacent to the mixing blade as the auger assembly is rotated.