collected by means of a cyclone collector or other types of collectors not shown referring to fig4 an apparatus 40 for forming mineral fibers is shown in another embodiment and comprises a tank 41 shafts 42 43 44 45 amp 46 having discs 47 48 49 50 and 51 mounted thereon the shafts 42 43 44 45 amp 46 are journaled in bearings 52 53 54 55 amp 56 the shafts being driven by motors not shown in a manner similar to that shown and described with regard to fig1 3 the discs 47 50 have their lower peripheries disposed within the molten mineral composition the disc 51 has a smaller diameter and does not extend into the liquid pool its purpose is to capture the larger drops and conglomerates of the liquid which have not been transformed into fiber and to return the unfiberized liquid material to the liquid pool contained in the tank as can be seen in fig4 the axial dimensions of the successive discs increase with the disc 51 having the greatest axial thickness this arrangement is provided to facilitate the capture by successive discs of the drops and conglomerates of the molten mineral composition which are ejected by.