ABSTRACT A study by a series of single hole blasts, slab blasting, in full scale in a large open pit iron mine was conducted to assess the influence of burden on various blast parameters for safe and economical blasting. The paper has described how the full scale tests were performed and how the optimum and critical burden dimensions were determined. The determined optimum and critical burdens were also expressed in terms of bench height and blasthole diameter. Furthermore, the relations established between burden and angle of breakage, volume of broken material, throw and backbreak respectively were given and discussed. The results show that the maximal volume of broken ore was achieved when the burden is almost equal to half the bench height.