Arsenohopeite, a new zinc arsenate mineral from the Tsumeb mine, Namibia
- Autor(en)
- Franz Neuhold, Uwe Kolitsch, Heinz-Jürgen Bernhardt, Christian Lengauer
- Abstrakt
Arsenohopeite, ideally Zn3(AsO4)2×4H2O, is the arsenate analogue of hopeite, Zn3(PO4)2×4H2O (it isisostructural with a-hopeite). It was found as a single colourless to blue crystalline grain from theTsumeb mine, Namibia. The holotype specimen is ~16161 mm in size. Arsenohopeite is associatedwith tiny white fibres of an unidentified Zn- and As-bearing phase. It is orthorhombic, space groupPnma, with a = 10.804(2), b = 19.003(4), c = 5.112(1) A ° , V = 1049.5(4) A ° 3 and Z = 4. Electronmicroprobe analysis yielded: ZnO 44.92, Fe2O3 0.92, MnO 0.51, MgO 0.20, CuO 0.02, As2O5 45.84(wt.%). The empirical formula is (Zn2.80Fe0.06Mn0.04Mg0.03)S2.93(As1.01O4)2×4H2O, based on 12oxygen atoms. Optically, the mineral is biaxial negative, with a = 1.598(2), b = 1.606(2), g = 1.613(2)(white light) and 2Vcalc = 86º. It is not pleochroic or fluorescent. Arsenohopeite is translucent with avitreous lustre. It is brittle, has an uneven fracture and (by analogy with hopeite) a cleavage that isperfect on {010}, good on {100} and poor on {001}. The calculated density is 3.420 g cm_3. The fivestrongest calculated powder diffraction lines are [d in A ° (I)(hkl)]: 9.502 (100)(020), 2.926 (95)(241),4.937 (50)(011), 4.110 (48)(230) and 3.567 (31)(240). The crystal structure of arsenohopeite has beensolved by direct methods and refined in space group Pnma to R1 = 0.0353. Raman spectroscopyconfirms the crystal-structure data and indicates the presence of weak hydrogen bonds.
- Organisation(en)
- Institut für Mineralogie und Kristallographie
- Externe Organisation(en)
- Naturhistorisches Museum Wien (NHM), Ruhr-Universität Bochum (RUB)
- Journal
- Mineralogical Magazine
- Band
- 76
- Seiten
- 603-612
- Anzahl der Seiten
- 10
- ISSN
- 0026-461X
- Publikationsdatum
- 2012
- Peer-reviewed
- Ja
- ÖFOS 2012
- 105113 Kristallographie, 104006 Festkörperchemie, 105116 Mineralogie
- Link zum Portal
- https://ucrisportal.univie.ac.at/de/publications/0c1a00d0-67e3-4340-b534-a633fed1ac8e