Performance of some distributions to describe rock fragmentation data

Ten functions (Weibull, Swebrec, Gilvarry, Grady and Lognormal, and their bi-component versions) are fitted to 448 sets of screened fragment size data from blasted and crushed rock. The ordinary least squares criterion has been used for the fits and two minimization techniques have been tested, in both cases running the problem repeatedly with different initial values of the unknown parameters in order to ensure a global minimum. There is a distinct behavior of errors across the passing range, which has been divided in four zones, coarse (>80%), central (80%–20%), fine (20%–2%) and very fine (