Abstract: The invention relates to a spiral jet mill (1) having a grinding chamber (10), which is delimited by a bottom (11), a cover (12), and a wall (13) that connects the bottom (11) and the cover (12), and having a plurality of grinding gas nozzles (14) that pass through the wall (13) and are connected to a grinding gas source, wherein each of at least part of the grinding gas nozzles (14) is provided with an associated switchable shut-off mechanism (15), which is able to independently open and close the connection to the grinding gas source. In addition, a method for grinding milling materials in a spiral jet mill is also disclosed.