Manganese-rich olivines: Identification from spectral reflectance properties

Abstract

Reflectance spectra of manganese-rich olivines were examined to determine which spectral features allow these minerals to be distinguished from forsteritic-fayalitic olivines. The results indicate that manganese-rich olivines can be distinguished on the following bases: Fe2+ M2 absorption band depths are reduced relative to Fe2+ Ml depths, the wavelength position of the Fe2+M2 absorption band is shifted to longer wavelengths(>1.08 μm) for olivines containing between ~10 and 70 mol % Mn2Si04 , and the presence of an isolated Mn2+ transition band near 0.4 μm . The absence of Fe2+ spin forbidden features in the visible wavelength region is not a reliable method for identifying manganese-rich olivines.