Abstract: The process for the production of mineral wool fibres is based on melt streams 1 issuing from a melt distributor 3 being reduced to fibres in a drawing nozzle 9 by a blast medium flowing with high velocity in the axial direction. The blast medium charged with fibres then arrives in a subsonic diffuser 11 in order to reduce the flow velocity. The fibre-charged stream 10 is subsequently led onwards in a rectangular shaft 13. To separate non-fibrous constituents (so-called shots), a plurality of gas jets 18 are blown in at the shaft end transversely to the main flow direction at an angle .alpha. of 30.degree. to 120.degree.. As a result the fibre-charged stream is deviated. The stream 22 deviated in a direction of .beta.=60.degree. to 140.degree. is then picked up by a fibre shaft 21 mounted at the same angle .beta. and led to a deposition belt 23.