. . "We begin by determining the mass fraction, ??j, of each of the various types of particles (Table 3), and the mass concentration, ??j,??, of each mineral, ??, within particles of each type, j (Table 4).The overall mass concentrations of hematite, goethite, and magnetite in the simulated sand is controlled, respectively, by ??h, ??g, and ??m." . .