Fits to the SED and mid-IR spectra of T Mon and X Sgr for different dust compositions. Top panel: standard model without dust component. Other three panels: models with dust composed of 80, 94, and 100% iron, respectively, with the remainder evenly split between silicates and aluminium oxide. The mid-IR spectrum is scaled to the model based on the average flux in the 10–10.5 μm region.