Four rock-forming mineral series: (1) clinozoisite-epidote series, (2) diopside-hedenbergits series from skarns, (3) cummingtonite-grunerite series and (4) gros-sular-andradite series from skarns may be determined by small-diameter (57.3mm) X-ray powder camera. Three regression equations are given for the first three series as follows:(1) for clinozoisite-epidote series,Fex1 = -34.0218 + 32.5026d(446) (Fig. 2) where Fex = Fe+3/(Fe+3 + Al),(2) For diopside -hedenbergite series in skarns, Fe1 = -70.5762 + 65.8647 d(750) (Fig. 3)where Fex = (Fe+2 + Fe+3 + Mn)/(Fe+2 + Fe+3 + Mn + Mg),(3) For1 cummingtonite-grunerite series, Fex = -53.7665 + 54.9886d(0,12,4)(Fig. 4)where Fex = (Fe+2 + Fe+3 + Mn)/(Fe+2 + Fe+3 + Mn + Mg). The determination diagram of a0 vs. f value(f =(And /(Gro +And) )× 100) for grossular-andradite series in skarns is a curveinstead of a straight line (Fig. 5).