Informace o publikaci
Vandermeerscheite, a new uranyl vanadate related to carnotite, from Eifel, Germany
| Autoři | |
|---|---|
| Rok publikování | 2019 |
| Druh | Článek v odborném periodiku |
| Časopis / Zdroj | Journal of Geosciences |
| Fakulta / Pracoviště MU | |
| Citace | |
| www | http://www.jgeosci.org/content/jgeosci.288_plasil.pdf |
| Doi | http://dx.doi.org/10.3190/jgeosci.288 |
| Klíčová slova | vandermeerscheite; uranyl vanadate; new mineral; carnotite group; crystal structure |
| Popis | Vandermeerscheite (IMA2017-104), K-2[(UO2)(2)V2O8]center dot 2H(2)O, is a new uranyl-vanadate mineral from the Schellkopf quarry, Eifel, Germany. The new mineral occurs in cavities of volcanic rocks, mostly growing on phillipsite-K. It forms rosette-like aggregates of thin blades up to 50 mu m long. Crystals are flattened on {10 (1) over bar} , and elongated on [101], with crystal forms {010}, {10 (1) over bar} and {111}; crystals are transparent with a vitreous luster. Vandermeerscheite is non-fluorescent under both long- and short-wavelength ultraviolet radiation. The Mohs hardness is similar to 2. The calculated density is 4.502 g. cm(-3) based on the empirical formula; 4.507 g.cm(-3) for the ideal formula. Vandermeerscheite dissolves easily in dilute HCl at room temperature. The new mineral is biaxial (-), with alpha = 1.83 (calc.), beta = 1.90(1), gamma = 1.91(1) (measured in white light at 22 degrees C). The measured 2V is 40(10)degrees estimated from conoscopic observation of interference figure; dispersion is moderate r < v. No pleochroism was observed. Optical orientation X approximate to perpendicular to {10<(1)over bar>}, Y approximate to [101], Z = b. The empirical formula of vandermeerscheite (on the basis of 14 O apfu) is (K-1.87 Ca0.05Na0.04)(Sigma 1.96)[(U-1.0(05) O-2)(2)V-1.99 O-8]center dot 2H(2)O. Raman spectrum is dominated by the vibrations of UO22+. and V2O8 units. Vandermeerscheite is monoclinic, P2(1)/n, a = 8.292(2), b = 8.251(3), c = 10.188(3)angstrom, beta = 110.84(3)degrees, V= 651.4(4) angstrom(3), and Z = 2. The seven strongest powder X-ray diffraction lines are [d(obs), angstrom (I, %)(hkl) ]: 7.49 (100) ((1) over bar 01), 4.147 (22) (020), 3.738 (32) ((2) over bar 02), 3.616 (20) ((1) over bar 21), 3.254 (31) (112, 121), 3.132 (21) ((1) over bar 22, 022), 2.989 (41) (211, 013). The crystal structure of vandermeerscheite was refined from the single-crystal X-ray data to R = 0.0801 for 644 independent observed reflections, with I-obs > 3 sigma(I). The structure, which differs from carnotite in symmetry, is based upon uranyl vanadate sheets of francevillite topology; in the interlayer, there are K+ cations and H2O groups that provide inter-sheet linkage. The new mineral honors Belgian amateur mineralogist and famous mineral photographer Eddy Van Der Meersche, who discovered the new mineral. |