Abstract: A vertical crusher having a housing defined chamber, enclosing a vertical axis rotor. The chamber has material(s) feed inlet(s) into the chamber. There is a drop-through outlet, which may be closable, from the chamber from which material(s) of at least a maximum size can drop in use. There are air inlet(s) into said chamber and air classifier outlet(s) from the chamber, for air or fine particles. Within the chamber also is a mass of discrete media, agitatable under the direct and/or indirect action of the rotor.