Shape of the 9.7 μm silicate feature in optical depth units for our AGN sample (see text, top-left). Black and gray lines show type-1 and type-2 AGN, respectively. Observational diagrams for the AGN sample: 7.5–14 μm versus 5.5–7.5 μm slopes (top-middle); 25–30 μm versus 7.5–14 μm slopes (top-right); S_10 μm versus C_10 μm (bottom-left), and S_10 μm versus 5.5–7.5 μm slope (bottom-right). Black squares and gray diamonds show the measurements in the Spitzer spectra for type-1 and type-2 AGN, respectively.