Michalskiite, Cu 2+ Mg 3 Fe 3+ 3.33 (VO 4 ) 6 , an Mg analogue of lyonsite, from the Ronneburg uranium deposit, Thuringia, Germany

[摘要] Michalskiite (IMA2019-162), Cu2+Mg3Fe33.+33(VO4)6, is a new mineral found on specimens from the dump of the Lichtenberg open pit, Ronneburg uranium mining district, Thuringia, Germany. It is a secondary mineral occurring with arcanite,epsomite, hematite and syngenite on matrix consisting of fine-grained quartz, K-feldspar and mica. It forms striated prismsand needles, elongated on [001], up to about 0.2 mm long. Crystals are brown-red with a light orange streak. They aretransparent and have adamantine lustre. The mineral is brittle with curved fracture, very good {001} cleavage and a Mohshardness of ~3½. The calculated density is 3.848 g.cm–3 based on the empirical formula. The new mineral is biaxial (–),with 2Vmeas = 49(1)°. No pleochroism was observed. Optical orientation is X = c. The empirical formula of michalskiite(on the basis of 24 O apfu) is (Cu21.+33Mg2.76Fe32.+75Al0.21Ni0.16Ti40.+14Mn30.+06Zn0.01)Σ7.40(V55.+96Si0.02)Σ5.98O24. The Raman spectrumis dominated by the vibrations of VO43– units. Michalskiite is orthorhombic, Pmcn, a = 10.2356(9), b = 17. 3689(16),c = 4.9406(4) Å, V = 878.35(13) Å3 and Z = 2. The five strongest powder X-ray diffraction lines are [dobs, Å (I, %) (hkl) ]:3.27 (100) (221,150), 2.74 (40) (241,151), 2.52 (50) (331), 1.55 (30) (282), 1.42 (25) (063). The crystal structure ofmichalskiite was refined from the single-crystal X-ray data to R = 0.0386 for 888 independent observed reflections, withIobs > 2σ(I). Michalskiite is isostructural with lyonsite; however, the Cu2 site in the lyonsite structure is split into M2 andM2’ sites in the michalskiite structure with Mg occupying the M2’ site. The new mineral name honours German mineralcollector and dealer Dipl. Min. Steffen Michalski, who discovered this mineral.

[学科分类] 自动化工程

[关键词] michalskiite;new mineral;lyonsite;crystal structure;Raman spectroscopy