Fig. 4. X-ray diffractograms of Mg-saturated, glycerated, and oriented Fithian illite (I) (<2 µm) before and after treatment with 10% (wt/wt) H₂O₂ (Fithian illite: 85% illite, 15% mixed layers, kaolinite, quartz). The treatment was conducted in the presence of straw and manure (S, M, diam. 0.1 mm). Before treatment, organo–mineral associations (5% organic matter) were prepared by three drying and wetting cycles. Treatments: (a) no, (b) I + H₂O₂, (c) I + H₂O₂ + S, and (d) I + H₂O₂ + M.