Mineral Composition of the Clay Fraction: III. of Some Main Soil Groups of China

Eighteen soil samples from China, representing Great Soil Groups of varying degree of weathering from Desert Soils to a Latosol were analyzed by fractionation at 5, 2, 0.2, and 0.08 µ, and application of X‐ray diffraction and elemental analysis procedures. In the weighted mean of these fractions of Pedocals, illite constituted 35%; of Pedalfers, vermiculite (5–12%) and kaolinite (11–50%) were more abundant; of Podsolic soils, vermiculite (5–12%) and kaolinite (11–21%) were abundant, and illite was also still important (15–23%); of the Latosols, gibbsite (25%) and hematite (23%) were dominant, but kaolinite, vermiculite, and illite were present. Montmorinic dioctahedral illite was found in the Desert soils and shows a young stage of soil weathering. The content of the montmorin series was low in most of the soils studied, attributed to drier cool climates than in the regions of the United States where it commonly occurs. The weathering mean is suggested for use in the measurement of the degree of soil mineral weathering. The weathering mean ranges from 2.5 to 11.0 for the soils of China examined.