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

March 27th, 2012  Posted by jmwarnsloh

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 (La0.71Nd0.15Pr0.11Sm0.01Y0.01)Σ0.99V1.01O4.00, 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.

Witzke, T., Kolitsch, U., Warnsloh, J.M. and Göske, J. (2008) Wakefieldite-(La), LaVO4, a new mineral species from the Glücksstern Mine, Friedrichroda, Thuringia, Germany. Eur. J. Min., 20, 6, 1135-1139.