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Plavnoite, a new K-Mn member of the zippeite group from Jachymov, Czech Republic

Jakub Plasil, Pavel Skacha, Jiri Sejkora, Anthony R. Kampf, Radek Skoda, Jiri Cejka, Jan Hlousek, Anatoly V. Kasatkin, Radim Pavlicek and Karel Babka
Plavnoite, a new K-Mn member of the zippeite group from Jachymov, Czech Republic
European Journal of Mineralogy (March 2017) 29 (1): 117-128


The new mineral plavnoite (IMA2015-059), ideally K (sub 0.8) Mn (sub 0.6) [(UO (sub 2) ) (sub 2) O (sub 2) (SO (sub 4) )].3.5H (sub 2) O, is a member of the zippeite group. It was found in the Plavno mine, in the eastern part of the Jachymov ore district, Western Bohemia, Czech Republic, where it occurs as a supergene alteration phase formed by hydration-oxidation weathering of uraninite in hydrothermal U-veins. It was found to be associated with marecottite, magnesiozippeite, blatonite and gypsum. The mineral occurs as reddish to reddish-orange thin blades, elongated on [001] and flattened on {010}, which are intergrown in globular aggregates up to 0.5 mm across. Crystals are transparent with a vitreous to silky lustre. The streak is pale orange. The mineral is non-fluorescent under both long- and short-wave ultraviolet (UV) radiation. The Mohs hardness is about 2. Crystals are brittle with perfect {010} cleavage and uneven fracture. The density calculated from the empirical formula is 4.926 g cm (super -3) Optically, plavnoite is biaxial (+), with alpha = 1.740(5), beta = 1.770(5), gamma = 1.850 (5) (measured in white light). The measured 2V is 64.6(4) degrees ; the calculated 2V is 65.3 degrees . Dispersion could not be observed; no pleochroism was observed. Electron-microprobe analyses yielded the empirical formula (based on 2U atoms per formula unit, apfu) K (sub 0.77) (Mn (sub 0.51) Zn (sub 0.04) Ni (sub 0.03) Mg (sub 0.02) ) (sub Sigma 0.60) [(UO (sub 2) ) (sub 2) O (sub 1.08) (OH) (sub 0.92) (SO (sub 4) ) (sub 0.96) (SiO (sub 4) ) (sub 0.24) ] (H (sub 2) O) (sub 3.50) . Plavnoite is monoclinic, C2/c, a = 8.6254 (16), b = 14.258(3), c = 17.703(4) A, beta = 104.052(18) degrees , V = 2122.0(8) A (super 3) and Z = 8. The structure (R (sub 1) = 4.99 % for 989 reflections with I > 3sigma [I]) contains UO (sub 7) pentagonal bipyramids and SO (sub 4) tetrahedra forming sheets of the well-known zippeite topology. The interlayer region contains infinite zig-zag chains of corner-sharing Mn (super 2+) Phi (sub 6) octahedra (Phi = O, H (sub 2) O) with K-centred polyhedra. The K atom sits at the partially occupied, mixed K/O site, the non-shared corner of the Mn2 octahedron. The mineral is named after the type locality - the Plavno mine.

ISSN: 0935-1221
EISSN: 1617-4011
Serial Title: European Journal of Mineralogy
Serial Volume: 29
Serial Issue: 1
Title: Plavnoite, a new K-Mn member of the zippeite group from Jachymov, Czech Republic
Affiliation: Czech Academy of Sciences, Institute of Physics, Prague, Czech Republic
Pages: 117-128
Published: 201703
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Germany
Accession Number: 2017-025977
Categories: Mineralogy of non-silicates
Document Type: Serial
Bibliographic Level: Analytic
N50°00'00" - N50°00'00", E12°00'00" - E12°00'00"
Secondary Affiliation: Mining Museum Pribram, CZE, Czech RepublicNational Museum, Department of Mineralogy and Petrology, CZE, Czech RepublicNatural History Museum of Los Angeles County, USA, United StatesMasaryk University, CZE, Czech RepublicRussian Academy of Sciences, Fersman Mineralogical Museum, RUS, Russian Federation
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, copyright, Schweizerbart'sche Verlagsbuchhandlung. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201716
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