Optical constants and diffuse reflectance of opaque minerals: A modeling study using magnetite

We use radiative transfer (RT) models, based upon the Hapke (1993) model, to estimate the imaginary refractive index of magnetite from laboratory reflectance measurements. We used a RT program coupled with a least-squares algorithm to fit measured reflectance data using complex refractive indices of magnetite estimated here and literature values. We included differing representations of the grain size distribution for modeling the measured reflectance of the magnetite samples. Best-fitting models were obtained when using the complex indices of refraction estimated from a specific grain size fraction to fit the same grain size of reflectance data. Magnetite complex refractive indices taken from reported literature studies resulted in the poorest fits to the measured reflectance data.