Soil samples from several forest areas in China were analyzed by X-ray powder diffractometry after mineral separation and enrichment. The density gradient separation method with sequential extraction by acetone-methylene iodide mixtures was applied for the separation of fine sand fraction of the soil samples. The clay fraction (<2um) was separated from silt fraction of soil samples prior to examination. Mineral components in some fine sand and clay samples were compared, and their weathering potentiality an...