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To sum up, the following conclusions can be reached from this work: 1. The analytic results for Mn2+ contents of the eight marble samples of different colors indicate that the color has nothing to do with Mn2+. Brown-black or darkred color of the three samples collected from the surface is caused mainly by high-valence Mn and contamination by oxides and hydroxides of Fe. The Fe3+ spectra of sample N5 at 83 m underground indicate that Fe3+ did not enter the crystal lattice. Its dark-red color is basically caused by locally enriched Fe3+ compounds. 2. The approach parameters of EPR spectra for dolomite (Fu Yude et al., 1986) and dolomite-marble indicate that almost all the Mn2+ in dolomite-marble are at the Mgsite. This cannot be explained by the crystal — field theory. Based on ion radius and the distortion degree of ligand-polyhedron, a satisfactory explanation has been proposed (Fu Yude et al., 1986 ). 3. EPR technique, in conjunction with other methods, is not only an important tool for studying trace paramagnetic impurities in minerals and mineral colors, but also possesses great significance for studying the colors of rocks. The explanation of spectra, however, must be based on detailed mineralogical observation.

In studying the degree of order (or disorder) in kaolinite, X-ray diffraction and DTA are commonly used, but spectroscopic method (as EPR, IR)has become a useful and additional tool now. The total iron content and the intensity of Fe3+(I) line are not always correlated negatively with order degree in natural kaolinite. But in the present case, they show direct correlations. So it appears that they cannot be used as an ideal parameter for measuring the order degree in kaolinite. The ratio of Fe3+(E)line and Fe3+(I)line intensities obtained directly from EPR spectrum of Fe3+at geff=4 appears to be a better EPR parameter for measuring the magnitude of order degree in kaolinite and for determining the intensity of some geological processes (such as weathering, hydrothermal alteration and so on) with aid of kaolinite. However, EPR data can only be used to qualitatively estimate the degree of order in kaolinite and related geological process for the present. There is still much work to be done in order to make EPR a method of quantitative estimation in the field.