Vandermeerscheite, a new uranyl vanadate related to carnotite, from eifel, Germany

Abstract

Vandermeerscheite (IMA2017-104), K2 [(UO2)2 V2 O8]·2H2 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 µm long. Crystals are flattened on {10¯1}, and elongated on [101], with crystal forms {010}, {10¯1} 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 ~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 α = 1.83 (calc.), β = 1.90(1), γ = 1.91(1) (measured in white light at 22 °C). The measured 2V is 40(10)° estimated from conoscopic observation of interference figure; dispersion is moderate r 3σ(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 H2 O 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.