A shearing/mixing tool (20) is one of several tools that is preferably mounted on a shaft (2). On both sides, the shaft (2) is rotatably mounted on the end walls of a horizontal drum. The tool (20) has at least one opening (25). Preferably, the shearing/mixing tools (1) are shearing/throwing blades (23) which are formed in a sickle-shaped manner at the end of stirring arms and rotate in the drum at an angle from the transverse axis of the shaft axis in such a way that the tip of the sickle or the spoon-shaped end of the blade (23) is the leading part. The shearing/throwing blade is arranged on an arm (22) made from a web plate that is bent in a Y-shaped manner.