Optical constants of monoclinic anisotropic crystals: gypsum

The principal complex refractive indices for gypsum have been derived in the infrared region of the spectrum. These values were obtained by dispersion analysis of the reflection spectra for E ‖ b and the a-c (monoclinic) plane. Two sets of complex indices are obtained for the latter plane, taking account of axis wander. The oscillator parameters are presented here, together with formulas for calculating the optical constants at any desired infrared frequency. In addition the usefulness of such optical constants for modeling the infrared properties of powders is demonstrated for gypsum and spodumene.