V-Muscovite

Andreas Ertl¹, John Rakovan², John M. Hughes², Heinz-Jürgen Bernhardt³, and George R. Rossman⁴

¹Institut für Mineralogie und Kristallographie, Geozentrum, Universität Wien, Althanstraße 14, A-1090 Vienna, Austria
²Department of Geology and Environmental Earth Science, Miami University, Oxford, OH 45056, U.S.A.
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-2M₁ (V₂O₃ = 11.35 wt%, one of the highest amounts 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 = 9.0704(10), c = 20.0321(21) Å, b = 95.773(2)º, Z = 4 has been refined to R = 7.2% for 1,070 unique reflections (Mo Ka). This muscovite, which occurs in small quartz veins in graphite schist from Weinberg Mountain, near the village of Amstall, 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 include α = 8.89^°and Δz = 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