Wakefieldite-(La), LaVO₄ , a new mineral species from the Glücksstern Mine, Friedrichroda, Thuringia, Germany

Authors: Witzke, Thomas; Kolitsch, Uwe; Warnsloh, Jens M.; Göske, Jürgen

Source: European Journal of Mineralogy, Volume 20, Number 6, November 2008 , pp. 1135-1139(5)

Publisher: E. Schweizerbart'sche Verlagsbuchhandlung

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Abstract:

Wakefieldite-(La), ideally LaVO₄, is a new mineral from the long abandoned Glücksstern Mine, Gottlob hill, Friedrichroda, Thuringia, Germany. The mineral occurs as light pinkish to brown prismatic crystals up to 0.5 mm in length. Wakefieldite-(La) is associated with hausmannite, baryte and gottlobite. The streak is white, the Mohs hardness 4 and the luster adamantine. The crystals are transparent to translucent. Electron microprobe analysis gave (wt.%) La₂O₃ 43.87, Ce₂O₃ 0.31, Nd₂O₃ 9.49, Pr₂O₃ 6.65, Sm₂O₃ 0.58, Y₂O₃ 0.31, CaO 0.10, UO₂ 0.01, V₂O₅ 34.91, As₂O₅ 0.06, P₂O₅ 0.02, SiO₂ 0.04, total 96.35. The empirical formula is (La_0.71Nd_0.15Pr_0.11Sm_0.01Y_0.01)_Σ0.99V_1.01O_4.00, ideally LaVO₄. The new mineral (IMA 89-035a) is the La analogue of wakefieldite-(Ce) and wakefieldite-(Y) and a member of the xenotime group. Wakefieldite-(La) has a zircon-type crystal structure (tetragonal, space group I4₁/amd), with a = 7.406(4), c = 6.504(8) Å, V = 356.8(6) Å³ from X-ray powder diffraction data, and a = 7.432(1), c = 6.521(1) Å, V = 360.18(9) Å³ from the single-crystal structure refinement (R₁ = 1.04 %). The La site is eight-coordinated to O atoms, with La-O distances of 2.4558(13) Å (× 4) and 2.5381(14) Å (× 4). The V-O distance equals 1.7133(13) Å (× 4). The calculated density for the measured composition is 4.703 g/cm³. Wakefieldite-(La) is uniaxial positive with ω and ε > 1.90, birefringence is medium, pleochroism E pale pinkish and O pale pinkish yellow.

Keywords: WAKEFIELDITE-(LA); NEW MINERAL; CRYSTAL STRUCTURE; XENOTIME GROUP; ZIRCON TYPE; FRIEDRICHRODA; THURINGIA; VANADATE

Document Type: Research article

DOI: http://dx.doi.org/10.1127/0935-1221/2009/0021-1875

Publication date: 2008-11-01

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