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
ArtNo. ESP154018103002, Price: 29.00 €
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