Polarized optical absorption and 57Fe Möessbauer study of pegmatitic muscovite

⁵⁷Fe Mössbauer spectra and polarized absorption spectra in the region 4000–6800 Å are reported for 14 common pegmatitic muscovites, 12 of which were selected from an extensive pegmatite complex. They were chosen to cover a wide range of color types (deep green, green, red-green and ruby-red) and ferric/ferrous ion ratios. Optical absorption properties are discussed in terms of the Fe²⁺, Fe³⁺ distribution in the M1 and M2 sites. Background absorption, and hence depth of color, appears to be determined primarily by an intense metal-ligant charge transfer which peaks in the UV and the intensity of which correlates linearly with the Fe²⁺ concentration in the normally unoccupied M2 site. The presence or absence of the Fe²⁺–Fe³⁺ metal–metal charge transfer bands in the region 5000–6000Å gives rise to the red and green hues observed in the muscovites studied.