In the report, the structural relaxation process of Fe10Ni65B15Si10 amorphous spin glass is described. The ribbon samples were prepared by melt spinning and heat treated using two different annealing processes AP1 and AP2. The techniques employed to investigate structural changes in the three alloy states (AQ (as-quenched), AP1 and AP2 were as follows: transmission electron microscopy, scanning electron microscopy with X-ray analysis, differential scanning calorimetry and density determination. Differences were detected in the amorphous structures for two states of relaxation in the alloy. The formation of clusters is proposed for one alloy state and the influence of clustering on the early stages of crystallization is discussed. Originator furnished keywords include: Spin glasses, metallic glasses, magnetic clustering, Fe-Ni-B-Si, and electron microscopy.