Cleusonite, (Pb,Sr)(U4+,U6+)(Fe2+ Zn)2(Ti,Fe2+ Fe3+)18(O,OH)38, a new mineral species of the crichtonite group from the western Swiss Alps

Details

Ressource 1Request a copy Sous embargo indéterminé.
State: Serval
Version: Final published version
Serval ID
serval:BIB_23F850DB013D
Type
Article: article from journal or magazin.
Collection
Publications
Title
Cleusonite, (Pb,Sr)(U4+,U6+)(Fe2+ Zn)2(Ti,Fe2+ Fe3+)18(O,OH)38, a new mineral species of the crichtonite group from the western Swiss Alps
Journal
European Journal of Mineralogy
Author(s)
Wülser P.A., Meisser N., Brugger J., Schenk K., Ansermet S., Bonin M., Bussy F.
ISSN-L
0935-1221
Publication state
Published
Issued date
2005
Peer-reviewed
Oui
Volume
17
Pages
933-942
Language
english
Abstract
Cleusonite, (Pb,Sr)(U4+,U6+) (Fe2+,Zn)(2) (Ti,Fe2+,Fe3+)(18) (O,OH)(38),
is a new member of the crichtonite group. It was found at two
occurrences in greenschist facies metamorphosed gneissic series of the
Mont Fort and Siviez-Mischabel Nappes in Valais, Switzerland (Cleuson
and Bella Tolla summit), and named after the type locality. It occurs as
black opaque cm-sized tabular crystals with a bright sub-metallic
lustre. The crystals consist of multiple rhombohedra and hexagonal
prisms that are generally twinned. Measured density is 4.74(4) g/cm(3)
and can be corrected to 4.93(12) g/cm(3) for macroscopic swelling due to
radiation damage; the calculated density varies from 5.02(6) (untreated)
to 5.27(5) (heat-treated crystals); the difference is related to the
cell swelling due to the metamictisation. The empirical formula for
cleusonite from Cleuson is (Pb0.89Sr0.12)(Sigma=1.01)
(U0.79+4U0.30+6)(Sigma=1.09) (Fe1.91+2Zn0.09)(Sigma=2.00)
(Ti11.80Fe3.44+2Fe2.33+3V0.19+5Mn0.08Al0.07)(Sigma=17.90)
[O-35.37(OH)(2.63)](Sigma=38). Cations were measured by electron
microprobe, the presence of structural (OH) was confirmed by infrared
spectroscopy and the U6+/U4+ and Fe2+/Fe3+ ratios were determined by
X-ray photoelectron spectroscopy. Cleusonite is partly metamict, and
untreated crystals only show three major X-ray diffraction peaks.
Because of this radiation-damaged state, the mineral appears optically
isotropic and shows a light-grey to white colour in reflected polarized
light. Cleusonite is trigonal, space group R $(3) over bar $, and
unit-cell parameters are varying from a = 10.576(3), c = 21.325(5)
angstrom (untreated crystal) to a = 10.4188(6), c = 20.942(1) angstrom
(800 degrees C treatment) and to a = 10.385(2), c = 20.900(7) angstrom
(1000 degrees C treatment). The three cells give a common axial ratio
2.01 (1), which is identical to the measured morphological one 2.04(6).
ne name cleusonite also applies to the previously described
``uranium-rich senaite'' from Alinci (Macedonia) and the
``plumbodavidite'' from Huanglongpu (China).
Create date
01/10/2012 20:07
Last modification date
31/10/2018 8:08
Usage data