Ranciéite crystals from Friesach, Carinthia, Austria
- Autor(en)
- Andreas Ertl, Franz Pertlik, Markus Prem, Jeffrey E Post, Soo Jin Kim, Franz Brandstätter, Ralf Schuster
- Abstrakt
Rancieite from Friesach, Carinthia, Austria, is described from an oxidation zone of a small (Mn-bearing) siderite deposit. This mineral is associated with "buserite-(Ca)", hollandite, braunite, romanechite, todorokite, cryptomelane, pyrolusite, manganite, nsutite, goethite, lepidocrocite, and calcite. Rancieite rarely forms small purple-silver grey crystals with a bright - metallic luster. Single crystals are up to 200 µm in length and ~0.1 \µm in thickness and exhibit well-formed crystal faces in some cases. The foliated habit of these crystals may be due to rapid growth on the plane of fissure. For the first time a relatively large number of X-ray powder diffraction lines (19 lines) of rancieite are described. Structure modeling, by the Rietveld method and with difference-Fourier summations shows, that rancieite is most probably trigonal in structure, in contrast to the monoclinic structure of birnessite. The layers of the (Mn4+,Mn3+)O6 octahedra, arranged parallel to (00.1), are intercalated predominantly by Ca atoms and water molecules, which are in a statistic and disordered arrangement. The powder pattern of this rancieite was indexed on a trigonal cell, space group P 3 [147], with a = 2.845(1) and c = 7.485(1) A, a:c = 1 : 2.632, Z = 1. The unit formula can be written as (Ca0.85Mn2+0.06K0.05Mgo 02Fe3+0.01lBa0.01) (Mn4+3.60Mn3+0.40)O9×ca. 2.8 H2O (calculated on the basis of O = 9; water and the valence states of Mn were calculated), or as Ca0.19Mn2+0.01K0.01(Mn4+0.80Mn3+0.09squareo.11)O2×ca.0.6 H2O (calculated on the basis of O = 2).
- Organisation(en)
- Institut für Mineralogie und Kristallographie
- Externe Organisation(en)
- Smithsonian National Museum of Natural History, Geologisk Museum, Geologische Bundesanstalt
- Journal
- European Journal of Mineralogy: an international journal of mineralogy, geochemistry and related sciences
- Band
- 17
- Seiten
- 163-172
- Anzahl der Seiten
- 10
- ISSN
- 0935-1221
- Publikationsdatum
- 2005
- Peer-reviewed
- Ja
- ÖFOS 2012
- 105116 Mineralogie, 1051 Geologie, Mineralogie
- Link zum Portal
- https://ucrisportal.univie.ac.at/de/publications/bd4c186e-3333-498f-a0a4-cfb1d6d44d3d