Pertoldite, trigonal GeO 2 , the germanium analog of α-quartz: a new mineral from Radvanice, Czech Republic

[摘要] The new mineral pertoldite was found in a burning waste dump of abandoned Kateřina colliery at Radvanice near Trutnov,Hradec Králové Department, Czech Republic. The dump fire started spontaneously before 1980 and no anthropogenicmaterial was deposited there. The determination of pertoldite as a natural analogue of synthetic trigonal α-GeO2 is based onits chemical composition, X-ray powder diffraction data, and Raman spectroscopy. Pertoldite occurs as white to brownishaggregates resembling cotton tufts, up to 1 mm in size, composed of acicular crystals up to ~1 μm thick and up to 1 mmin length. Individual crystals are distorted, resembling textile fibers. Pertoldite was formed by direct crystallization fromhot (400–500 °C) gasses containing Cl and F as transporting agents at a depth of 40–60 cm under the surface of a burningcoal mine dump. It nucleated as a thin, delicate crust on a chip of siltstone together with multi-component aggregatesof galena, stibnite, bismuthian antimony, greenockite, and bismuth. The ideal formula of pertoldite, GeO2, requires 100wt. % GeO2. Germanium is partially substituted by silica (2.33–5.67 wt. % SiO2), the extent of Ge1Si–1 substitution islimited to 0.03–0.09 apfu Si, and the empirical formula ranges between (Ge0.91-0.97Si0.03-0.09)Σ1.00O2. Pertoldite is trigonal,P3121 or P3221, a = 4.980(5) Å, c = 5.644(4) Å, with V = 121.2(2) Å3 and Z = 3. The strongest reflections of the powderX-ray diffraction pattern [d (Å)/I (hkl)] are: 4.315/44(100), 3.425/100(101,011), 2.490/31(110), 2.360/41(012,102),1.867/31(112), 1.4179/31(023,203), 1.4124/37 (122,212). The crystal structure of pertoldite is based on corner-sharing[GeO4] tetrahedra forming a three-dimensional network similar to that of α-quartz. Pertoldite is named after ZdeněkPertold (1933–2020), professor of economic geology at the Faculty of Sciences, Charles University in Prague. The mineral and its name have been approved by the Commission on New Minerals, Nomenclature and Classification of theInternational Mineralogical Association (number 2021-074) and the holotype specimen is deposited in the collectionsin the Department of Mineralogy and Petrology, National Museum in Prague, under the catalogue number P1P 31/2021.

[学科分类] 自动化工程

[关键词] pertoldite;new mineral;germanium oxide;GeO2;pyrometamorphism;Radvanice