Complex refractive index of limestone in the visible and infrared

Near normal-incidence relative spectular reflectance was measured throughout the 0.2-32.8-microm wavelength region for three cut and polished samples of Bethany Falls limestone. Water, for which the complex refractive index is well known, was the reflectance standard. Although the visual appearances of the three samples were quite different, the relative reflectance spectra for the three samples were nearly identical. The three relative reflectance spectra were averaged to obtain a composite relative reflectance spectrum. Kramers-Kronig analysis of the composite relative reflectance spectrum then provided spectral values of the complex refractive index for limestone. A classical Lorentz dispersion analysis was also made of the composite relative reflectance spectrum, and the resulting dispersion parameters were tabulated. Infrared bands characteristic of the carbonate ion CO(3)(-2) of the calcite comprising the limestone appeared as strong features in the spectra.