The state of iron in andalusite

Characterization of Mn oxides in cemented streambed crusts from Pinal Creek, Arizona, U.S.A., and in hot-spring deposits from Yuno-Taki Falls, Hokkaido, Japan

“…Similar large values of QS (quadrupole splitting) parameters were reported for andalusite (Meisel et al 1990) and epidote (Bancroft et al 1967). In those cases, spectra were interpreted to represent Fe 3+ , which appears to occupy irregular polyhedra in the crystal structures.…”

“…However, from the ratios of subspectra areas, it was possible to suggest that for the Pinal Creek samples, nearly 50% of the total Fe in the cemented crust was present as hematite, magnetite, and maghemite and only a small amount (less than 6% of total Fe) as braunite/andalusite or epidote (Meisel et al 1990). The rest of Fe 2+ and Fe 3+ quadrupole split doublets can be attributed to the octahedral sites (cis and trans) in chlorite and mica-type phyllosilicates.…”

Optical absorption of electronic Fe–Ti charge-transfer transition in natural andalusite: the thermal stability of the charge-transfer band

“…1, 2), as well as a relatively broad shoulder at 25000 cm -1 and a couple of weak narrow peaks at ca. 22000 cm -1 and 22900 cm -1 , were all attributed by Faye and Harris (1969) Taking into account that Brazilian andalusites with similar iron contents to those studied here have Fe 2+ /Fe 3+ on the order of one (Meisel at al. 1990) and that the oscillator strengths of electronic spin-allowed transitions are a few orders of magnitude higher than those of spinforbidden ones (e.g.…”

Determination of the locations of Mn and Fe in Mn–bearing andalusite by anomalous X–ray scattering and X–ray absorption fine structure analyses

“…4) coincides with that of aegirine NaFeSi 2 O 6 . This result suggests that Fe atoms are also in the +3 oxidation state, and that a small number or none of them are in the +2 oxidation state in the Mnbearing andalusite sample, as reported by Meisel et al (1990).…”