Synthetic emission spectra of four selected lava planets with outgassed silicate atmospheres: HD 213885 b, 55 Cnc e, K2-141 b and TOI-1807 b. The spectra are computed for the entire JWST wavelength range and convolved to a resolution of R = 800. The blue curves denote blackbody emission of numerically converged surface temperature. Corresponding temperature profiles for each planet are shown in the inset. Error bars are simulated for the JWST MIRI LRS mode, assuming 20 h of observations (3 eclipses) and binned to R = 10. The indicated MIRI coverage region includes both, low resolution and medium resolution modes. Shaded SiO (9 μm) and SiO₂ (7 μm) are likely to be strongest characterisable features of silicate atmospheres. Note that SiO also has an additional band between 4 and 5 μm, however, its magnitude is, in most cases, small. The noise at 4–5 μm is an artefact of generated synthetic stellar spectra.