The mineralogical constituents of the clay fraction(<1μ) of drab soils,including brown-drab soils,leached drab soils,typical drab soils,yellowish drab soils,and meadow drab soils were investigated by chemical analysis,cation-exchange capacity determinations,X-ray diffraction and differential thermal analysis.Data of chemical analysis show relatively higher contents of Fe₂O₃ and Al₂O₃ in these soils,as compared with the contents of the brown forest soils.The characteristic clay minerals of the drab soils as shown by X-rah diffraction patterns and thermo-differential curves are illite and vermiculite,with kaolinite and montimorillonite as minor constituents.The amount of vermiculite tends to increase from lower horizons to the upper.The soils possess a silica-sesquoxide ratio of 2.5-3.1,K₂O content 2.2-2.6,and canon-exchange capacity 45-60 m.e./100g.Characteristics of mineralogical constituent of drab soils are closely related to their parent materials and also to their environments of soil formation.Soils developed on the lossal deposits contain montmorillonite,but no interstratified clay minerals,whereas soils developed on the weathering products of metamorphic rocks apparently contain ractoriteillite interstratified clay minerals (11.4Å).