We report here preliminary results, on the crystallisation behaviour of Lead Borate and Barium Borate glasses doped with Fe2O3 (congruent to 30 mol %) in the melt. In these glasses different crystalline phases can be observed, two of them are magnetic and the: third is a crystalline Pb Borate or Ba Borate. Thermal treatment temperature was chosen close to the lower point in order to avoid deformation of the samples. Samples were prepared and subjected to two schedules of thermal treatment: (4 and 8 hours) with and without magnetic field (approximately 1 Tesla). The following techniques were employed to analyse the samples: accurate density measurements, X-ray diffraction, high-resolution optical microscopy, Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray analysis (EDAX). The effect of the field during the heat treatment can be considered in two categories. In one case, application of the magnetic field can lead to dissolution of the non-magnetic phase while in the other case it can help grow the magnetic phase. We offer a tentative explanation of the observations.