V-Muscovite

John M. Hughes¹, Andreas Ertl², Heinz-Jürgen Bernhardt³, John Rakovan¹, and George R. Rossman⁴

¹Department of Geology, Miami University, Oxford, OH 45056, U.S.A.
²Institut für Mineralogie und Kristallographie, Geozentrum, Universität Wien, Althanstraße 14, A-1090 Vienna, Austria
³Institut für Geologie, Mineralogie und Geophysik, Ruhr-Universität Bochum, D-44801 Bochum, Germany
⁴Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91125-2500, U.S.A.

The crystal structure of a green, transparent, vanadium-rich 2M₁muscovite (V₂O₃ = 11.35 wt%, the highest amount reported to date in muscovite) with the optimized formula (K_0.94Na_0.06) (Al_1.20V³⁺_0.61Mg_0.12Cr³⁺_0.07) (Si_1.54Al_0.46)_T₁ (Si_1.54Al_0.46)_T₂ O₁₀ (OH)₂and space group C2/c, a = 5.2255(6), b = 9.070(1), c = 20.032(2) Å, b = 95.773(2)º, Z = 4 has been refined to R = 7.2% for 1,037 unique reflections (Mo Ka). This muscovite, which occurs in small quartz dikes in graphite schist from Weinberg Mountain, near Amstall village, Lower Austria, is distinctly low in Cr (Cr₂O₃: ~1.4 wt%) and in Mg (MgO: ~1.1 wt%); Fe, Mn and Ti are below the detection limit. All octahedral cations occupy the M2 site, and the average octahedral bond (M2-O) distance is 1.953 Å. Structural distortions to accommodate tetrahedral-octahedral sheet misfit include a = 8.89^O, and Dz = 0.193 Å, resulting in an interlayer spacing of 3.35 Å. The optical absorption spectrum of this V-rich muscovite shows absorption features at 427 and 609 nm that define a transmission window centered at 523 nm. These absorption features are consistent with those expected for V³⁺ in mica, but the 609 nm band has a slightly longer wavelength compared to low V-content micas.

Vanadium-rich muscovite from Austria: Crystal structure, chemical analysis, and spectroscopic investigations

Abstract