Fresnel reflectance and dispersion analysis are used to derive the real and imaginary indices of refraction of hydrous carbonate (dypingite) and hydrous sulfate (fibroferrite), in the 5.0--25 μm wavelength region, and hydrous nitrate/sulfate (darapskite) in the 5--17 μm wavelength region. These indices are useful for theoretical modeling of the radiative transfer that occurs within atmospheres of planets and particulate surfaces of solid bodies in the solar system. ¿ American Geophysical Union 1996