V3+-bearing, Mg-rich, strongly disordered olenite from a graphite deposit near Amstall, Lower Austria: A structural, chemical and spectroscopic investigation

Abstract

An optical absorption spectrum, structural and chemical data of green V-and Cr-bearing tourmaline from the graphite deposit at Weinberg Mountain, west of the village of Amstall, Lower Austria, were obtained. To address the role of V and Cr in the spectrum of tourmaline, examination of additional samples of V-and Cr-containing tourmalines was conducted. This study confi rmed that V and Cr produce similar spectra in tourmalines. However, the wavelengths of the 600 nm region band (E\\c), and the 440 nm region band (E⊥c) varied in relation to the proportion of Cr in the sample. Likewise, the intensity of the 680 nm region spin-forbidden bands varies in proportion to the absolute amount of Cr in the sample. Molar absorption coeffi cients for both V and Cr in tourmaline were determined for the 600 nm region. For the E⊥c band, ε(V) = 12.3 ± 0.7; ε(Cr) = 39.7 ± 1.4; and for the E\\c band, ε(V) = 11.9 ± 2.0; ε(Cr) =15.9 ± 2.8. In each case the Cr bands are more intense than the corresponding V band.These features can be used to confi rm that the spectroscopic features of the Amstall tourmaline come dominantly from V. The optimized formula, calculated using structural and chemical data for the core of a 4 mm wide crystal, is X (Na 0.69 Ca 0.16 K 0.01 ᮀ 0.14 ) Y (Al 1.46 Mg 1.34 V 3+ 0.11 Ti 4+ 0.05 Cr 3+ 0.02 Fe 0.02 ) Z (Al 4.77 Mg 1.23 ) (BO 3 ) 3 T (Si 5.70 Al 0.30 ) O 18 [(OH) 3.87 O 0.13 ], with a = 15.984(2), c = 7.222(2) Å, R = 0.017. The optimized formula, calculated using structural and chemical data for the rim, is X (Na 0.67 Ca 0.24 K 0.01 ᮀ 0.08 ) Y (Al 1.57 Mg 1.24 V 3+ 0.11 Ti 4+ 0.05 Cr 3+ 0.02 Fe 0.01 ) Z (Al 4.84 Mg 1.16 ) (BO 3 ) 3 T (Si 5.90 Al 0.10 ) O 18 [(OH) 3.35 O 0.65 ], with a = 15.9175 (5), c = 7.1914(4) Å, R = 0.014. Whereas the V 3+ and Cr 3+ contents stay constant, Mg decreases from the core to the rim. This is refl ected by decreasing <Y-O> (from 2.013 to 2.003 Å) and <Z-O> distances (from 1.938 to 1.930 Å). The relative short <Y-O> distances and the enlarged <Z-O> distances show that Al and Mg are strongly disordered between the Y and Z sites in this tourmaline. We assume that the strong Mg-Al disorder between the Y and the Z sites in this tourmaline derived from a high-T overprint (~750 °C, ~6-9 kbar) during crystallization, which is supported by a relatively high amount of [4] Al and low vacancies at the X site.

Thermal stability of extended clusters in dravite: a combined EMP, SREF and FTIR study

“…The sample color is most probably caused by low contents of Cr and V (see below), which are associated with green colors in tourmaline (e.g., Ertl et al 2008;Bosi et al 2014). …”

Vanadium-bearing tourmaline in metacherts from Chvojnica, Slovak Republic: crystal chemistry and multistage evolution

“…Amstall, Lower Austria (Ertl et al 2008). Olenite from Amstall has a very similar composition to tourmaline from Chvojnica, but there is a strong Al-Mg disorder between Y and Z sites, which gives Al > Mg at the Y site.…”

“…Badalov (1951) reported the occurrence of V-bearing tourmaline in black quartz-graphite hornfels from Uzbekistan. Vanadium-bearing tourmaline also occurs in Tanga Province, Tanzania (Basset 1956), Mariposa County, California (Snetsinger 1966, Foit & Rosenberg 1979, the Kwal district, Kenya (Schmetzer et al 1979), Bítovánky, Czech Republic (Houzar & Šrein 1993, Cempírek et al 2006, Primorye, Russia (Kazachenko et al 1993), and Amstall, Lower Austria (Ertl et al 2008).…”

“…A very low Fe content allowed estimation of (OH)and O 2from the chargebalanced formula (Henry & Dutrow 1996). Owing to the likely Mg-Al disorder (Hawthorne et al 1993, Ertl et al 2008 and V occupancy at both Y and Z sites (Foit & Rosenberg 1979), we decided to treat the Y and Z sites as united in the chemical formula. reSUltS…”

Vanadium-rich Muscovite from Austria: Crystal Structure, Chemical Analysis, and Spectroscopic Investigations

“…Green V-rich muscovite from Weinberg mountaiñ 500 m west of the village of Amstall, Lower Austria, occurs with pyrite in small quartz veins in graphite schist. Structural and chemical data and an optical absorption spectrum of green V-and Cr-bearing tourmaline with 0.85 wt.% V 2 O 3 and~0.17 wt.% Cr 2 O 3 from the same locality was described by Ertl et al (2008). The core of this dravite has lattice parameters of a ¼ 15.984(2), c ¼ 7.222(2)Å, while the rim exhibits smaller lattice parameters of a ¼ 15.9175(5), c ¼ 7.1914(4)Å, mainly due to a decreasing Mg content while the V and Cr content does not change significantly.…”