Derivation of Midinfrared (5-25 micrometers) Optical Constants of Some Silicates and Palagonite

The midinfrared 2000-400/ cm (5-25 microns) optical constants (real (n) and imaginary (k) indices of refraction) are presented for: (1) pyrophyllite; (2) kaolinite; (3) serpentine; (4) montmorillonite; (5) saponite; (6) palagonite; and (7) orthopyroxene. Comparison of the values derived here with those previously presented for serpentine, montmorillonite, and palagonite is generally quite good and discrepancies between values are probably due to either chemical differences between the actual samples or different techniques used to derive the values. For montmorillonite, saponite, and palagonite we were able to derive optical constants in the region of the H2O-bending fundamental near 6 microns. We find that if a pellet of pure material can be produced with a mirror-like surface then the optical constants of clays and other noncohesive materials can be readily derived.