7–35 µm opacity curves of pyroxene, olivine, and various iron oxides, compared with the normalized Spitzer spectrum of HD 144432 (brown curve, AOR: 3587072). The Spitzer spectrum was normalized by dividing the data with the source function of our best-fit model. Optical constants of iron oxides were downloaded from the Jena Database of Optical Constants for Cosmic Dust (https://www.astro.uni-jena.de/Laboratory/OCDB/mgfeoxides.html). The original source for wüstite is Henning et al. (1995). Optical data for hematite and magnetite come from Amaury H.M.J. Triaud (unpublished). The opacity curves were generated with optool, using the distribution of hollow spheres (DHS) scattering theory. The upper boundary of the hollow sphere distribution (ƒ_maχ) is 0.7. All curves are arbitrarily scaled and shifted to aid visual comparison.