A rock processing plant having a machine frame , which supports a screening unit , wherein the screening unit has at least two screen decks which are arranged offset from each other in the vertical direction (H) of the rock processing plant , wherein the screen decks each have a discharge area (A1, A2), wherein a transport device is connected to the screening unit in the conveying direction, wherein the transport device forms a feed area (15.1) and a discharge area (15.2), wherein a transport means, in particular an endless circulating conveyor belt (15.3), extends in a transport direction (D) at least partially between the feed area (15.1) and the discharge area (15.2), wherein the transport device is attached to the machine frame by means of a mechanical actuator , wherein the mechanical actuator can be used to move the feed area (15.1) of the transport device between two control positions, in which the feed area (15.1) is optionally assigned to one of the discharge areas (A1, A2) of the two screen decks or both discharge areas (A1, A2), and wherein the mechanical actuator can be used to move the feed area (15.1) of the transport device between the two control positions in the vertical direction and in the transport direction (D) of the transport device , wherein a swivel mechanism is effective between the machine frame and the transport device , which swivel mechanism is used to guide the displacement of the feed area (15.1) between the two control positions, wherein the swivel mechanism has a holder and a swingarm , and wherein the holder and the swingarm are each coupled directly or indirectly to the machine frame by means of a joint (62, 64.1) and each coupled directly or indirectly to the transport device by means of a further joint (54.1, 19.1), characterized in that the holder, the swingarm, the machine frame and the transport device form a four-bar linkage system. wherein the screening unit has at least two screen decks which are arranged offset from each other in the vertical direction (H) of the rock processing plant , wherein the screen decks each have a discharge area (A1, A2), wherein a transport device is connected to the screening unit in the conveying direction, wherein the transport device forms a feed area (15.1) and a discharge area (15.2), wherein a transport means, in particular an endless circulating conveyor belt (15.3), extends in a transport direction (D) at least partially between the feed area (15.1) and the discharge area (15.2), wherein the transport device is attached to the machine frame by means of a mechanical actuator , wherein the mechanical actuator can be used to move the feed area (15.1) of the transport device between two control positions, in which the feed area (15.1) is optionally assigned to one of the discharge areas (A1, A2) of the two screen decks or both discharge areas (A1, A2), and wherein the mechanical actuator can be used to move the feed area (15.1) of the transport device between the two control positions in the vertical direction and in the transport direction (D) of the transport device , wherein a swivel mechanism is effective between the machine frame and the transport device , which swivel mechanism is used to guide the displacement of the feed area (15.1) between the two control positions, wherein the swivel mechanism has a holder and a swingarm , and wherein the holder and the swingarm are each coupled directly or indirectly to the machine frame by means of a joint (62, 64.1) and each coupled directly or indirectly to the transport device by means of a further joint (54.1, 19.1), characterized in that the holder, the swingarm, the machine frame and the transport device form a four-bar linkage system. <EOS>