This paper outlines the results of the double impact failure of individual cores of rock, the progeny of which were described by a fragmentation fractal dimension. This, swing pendulum generated, data was compared to that previously established from the single impact breakage of rock cores, and the fragmentation fractal was found to be a suitable tool by which the two mechanisms could be assessed. The swing pendulum data was seen to adequately comply with an empiric based fractal model of fragmentation derived from the above mentioned single impact tests. Although an additional consideration was necessary to account for the velocity of the impact event, this indicated that the model may have wider application and be relevant to the impact failure of rock in general. However, ultrafast load cell testing of selected rocks illustrated that a previously postulated function for describing the relation of fragmentation fractal and size of the parent particle did not hold. The extrapolated fragmentation fractal significantly under estimated that directly obtained from the progeny of the ultrafast load cell experiments.