It is well known that dust clouds selectively absorb radiation in the 700–1300 cm-1 atmospheric window region. Studies have shown that dust clouds are composed of the same minerals as surface soils, although in different proportion. We have examined seventy soil samples from a number of locations around the world to determine their compositions and spectral characteristics. The results indicate that there are five major components which selectively absorb radiation in the 700–1300 cm-1 region. These are three clay minerals, silica, and calcium carbonate. Absorptivity coefficient spectra of representative soil samples are given.
D. F. Flanigan and H. P. DeLong, "Spectral Absorption Characteristics of the Major Components of Dust Clouds," Appl. Opt. 10, 51-57 (1971)