The relative intensities of FeLα anti Lβ X-ray emission peaks Hitler significantly with valence state and bond association, even though the wavelength shift is very small. Lβ/Lα increases systematically with increase in Fe2+/Fe3+ or Mn2+/Mn3+ in their respective oxides, in the hematite-ilmenite series, in Lhe magnctite-ulvospinel series, anil in anhydrous silicates. Fe Lβ/Lα ratios are much higher for Fe-O-Si and Fe-O-Ti bond associations than for Fe-O-Fe. Lβ/Lα ratios clearly distinguish ferric-rich alkali amphiboles from ferrous-rich calciferous amphiboles. No significant variation was found for the individual mineral types—chloritoid, staurolite, and cordierite, but a variation does occur in chlorite. Ferric-rich muscovite is not distinguishable from ferrous-rich biotite.