Original paper

Plumboagardite, a new mineral of the mixite group from an occurrence in the Southern Black Forest, Germany

Walenta, Kurt; Theye, Thomas

Neues Jahrbuch für Mineralogie - Abhandlungen Band 181 Heft 3 (2005), p. 219 - 222

published: Jun 9, 2005

DOI: 10.1127/0077-7757/2005/0019

BibTeX file

ArtNo. ESP154018103002, Price: 29.00 €

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Abstract

Plumboagardite occurs among the secondary minerals of the mine Aitern Süd in the Southern Black Forest, Baden-Württemberg, Germany, in association with quartz, fluorite, chrysocolla and limonite.It forms spherulitic aggregates of radial fibrous structure on chrysocolla composed of acicular crystals elongated [0001] and reaching 0,05 mm in length. Colour green, streak greenish, lustre vitreous, no distinct cleavage, hardness 3, density (calc.) 3.741g/cm3. Optical properties: nω 1.726 (5), nε 1.805 (5), uniaxial (+).Unit-cell dimensions of the hexagonal mineral: a 13.77(2), c 5.94 (1), Z = 2, space group P63/m. Strongest lines of the powder pattern: 12.01 (10) 1010, 4.51 (6) 2130, 1121, 3.60 (8), 2131, 2.98 (6) 4040, 2241, 0002, 2.49 (7) 3251, 3142. Chemical composition (wt.%): PbO 8.99, La2O3 1.91, Nd2O3 1.17, Ce2O3 0.96, Sm2O3 0.20, Pr2O3 0.19, Gd2O3 0,17, Dy2O3 0.10, Y2O3 0.96, CaO 1.44, CuO 40.49, Fe2O3 1.54, As2O5 29.74, P2O5 0.30, SiO2 1.46, H2O (by difference) 10.38, total 100.00%. The empirical formula – based on 12 O + 6 OH structural anions – is: [Pb0.44(La0.13Y0.09Nd0.08Ce0.06Pr0.01Sm0.01Gd0.01Dy0.01)ΣREE = 0.40Ca0.28]Σ = 1.12(Cu5.59Fe0.21)Σ = 5.80(As2.84Si0.27P0.05)Σ = 3.16O12(OH)6 · 3.33H2O simplified (Pb,REE,Ca)Cu6(AsO4)3(OH)6 · 3H2O. The mineral is easily soluble in dilute HCl and HNO3.

Keywords

mixite group • paragenesis • optical properties • crystallographic data • powder pattern • mine aitern sud (southern black forest baden-wurtt