The objective of this investigation constitutes a detailed study of the fragmentation characteristics for blasted magnetite ore from a specific ring in the sublevel caving (SLC) mine in Kiruna.For comparison lab scale data from crushing and grinding as well as blasting plus historical full-scale data from the mine were analysed. The present data confirms that the material basically follows the “Natural Breakage Characteristics” criteria within the fines region. The complete fragmentation distributions yield an extremely large variation for the parameter x50. The shapes of the complete sieving curves do not entirely fit the Swebrec function since they are flatter, roughly over the range 25-75 mm. The relative flattening of the sieving curves may be due to “selective” breakage in the mid-range, which would increase the amount of fines. This resembles the behaviour in autogenous grinding, i.e. the self-breakage of large fragments createspebbles that grind the mid-fractions to fine, and also an effect attributable to secondary fragmentation in block caving. Several different mechanisms are conceivable to account for an altered fragmentation mechanism. From the present large SLC layout one could expect more comminution occurring in the debris flow, due to longer flow paths. On the other hand, the present samples were taken before 10 % draw, which speaks in favour of relatively short paths, unless the draw has been extremely uneven. Despite this flattening deviation from Swebrec distribution behaviour – which is likely to be caused by the internal flow mechanisms in the SLCprocess – the main conclusion is still that magnetite itself behaves like waste rock from a blasting point of view.