2015-11-11 · grinding data of the coarse particles. Figs. 7-10 show the second-order plots for the coarse feed sizes (-5+4 mm, -3.15+2.5 mm) of quartz, limestone, iron ore and the mixture of quartz/limestone. Table 1 demonstrates the comparison between the R2 of the first- and second-order plots for the coarse particle sizes of quartz, limestone, iron