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95 results on '"Bernhardt, Heinz-Jürgen"'

2. Confirmation of Siderazot, Fe3N1.33, the Only Terrestrial Nitride Mineral

Author

Bette, Sebastian, Theye, Thomas, Bernhardt, Heinz-Jürgen, Clark, William P., and Niewa, Rainer

Subjects
lcsh:Mineralogy, lcsh:QE351-399.2, iron, silvestrite, Fe3N, siderazot, nitride
Abstract

Siderazot, the only terrestrial nitride mineral, was reported only once in 1876 to occur as coating on volcanic rocks in a fumarolic environment from Mt. Etna and, to date, has been neither confirmed nor structurally characterized. We have studied the holotype sample from the Natural History Museum, London, UK, originally collected by O. Silvestri in 1874, and present siderazot with ε-Fe3N-type crystal structure and composition of Fe3N1.33(7) according to crystal structure Rietveld refinements, in good agreement with electron microprobe analyses. Crystal structure data, chemical composition, and Raman and reflectance measurements are reported. Possible formation conditions are derived from composition and phase stability data according to synthetic samples.

Published
2021
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8. Vanadium-rich Muscovite from Austria: Crystal Structure, Chemical Analysis, and Spectroscopic Investigations

Author

Ertl, Andreas, Rakovan, John, Hughes, John M., Bernhardt, Heinz-Jürgen, and Rossman, George R.

Abstract

The crystal structure of a green, transparent, vanadium-rich muscovite-2M_1 (V_2O_3 = 11.35 wt.%, one of the highest amounts reported to date in muscovite) with the optimized formula (K_(0.94)Na_(0.06))M2(Al_(1.20)V^(3+)_(0.61)Mg_(0.12)Cr^(3+)_(0.07))T1(Si^(1.54)Al_(0.46))T2(Si_(1.54)Al_(0.46))O_(10)(OH)_2 and space group C2/c, a 5.2255(6), b 9.0704(10), c 20.0321(21) Å, β 95.773(2)°, Z = 4 has been refined to R = 6.97% for 1070 unique reflections (MoKα). 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 (Cr_2O_3 ∼1.4 wt.%) and Mg (MgO ∼1.1 wt.%); Fe, Mn, and Ti are below 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 V^(3+) in mica, but the 609 nm band has a slightly longer wavelength than in low-V micas.

Published
2019

40. Duhamelite discredited

Author

Krause, Werner, primary, Kolitsch, Uwe, additional, Bernhardt, Heinz-Jürgen, additional, and Effenberger, Herta, additional

Published
2003
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46. Serendibite from Sri Lanka

Author

Schmetzer, Karl, primary, Bosshart, George, primary, Bernhardt, Heinz-Jürgen, primary, Gübelin, Edward J., primary, and Smith, Christopher P., primary

Published
2002
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