Effect of composition on the spectrum of a mineral atmosphere at constant fO₂ relative to the IW buffer (ΔIW-2) and irradiation temperature (2500 K) for an Earth-sized planet. Shown are the stellar spectrum (top), the spectrum of planetary emission (center, coloured) and the secondary occultation depth F_p/F_*, the ratio between the two (bottom, colours). Flux ratios for outgassed atmospheres may overlap, as evident for the CORL and ARS compositions. Only the ultra-SiO₂-poor composition XTREM is slightly distinct by showing less emission in the TiO band. Both iron-free compositions (HERM and XTREM) do not express iron lines.