Ultraviolet determinations have been made of the optical complex index of refraction of augite, bytownite, enstatite, diopside, troilite, pyrrhotite, and the Bruderheim meteorite, and the results have been used in a Mie-scattering program. From this analysis, bytownite and meteorite particles with radii between 0.1 and 0.001 microns could account for the interstellar extinction peak at 0.22 microns; however, both of these materials would produce a double peak at 0.22 microns. The splitting for the meteoritic material is stronger than that of the bytownite and thus harder to reconcile with the interstellar extinction. Enstatite is improbable because the absorption maximum occurs at about 0.26 microns. The other samples also do not have appropriate absorption curves and are ruled out.