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New data on cafarsite; reinvestigation of its crystal structure and chemical composition

Georgia Cametti, Mariko Nagashima, Martin Fisch and Thomas Armbruster
New data on cafarsite; reinvestigation of its crystal structure and chemical composition
European Journal of Mineralogy (May 2018) 30 (4): 859-868

Abstract

The crystal structure of cafarsite from Wanni glacier, Monte Cervandone, was re-investigated by single-crystal X-ray diffraction (space group Pn-3, R1 = 0.022) and new electron-microprobe analyses. The REE (mainly Ce and Y) were found to substitute Ca. A new anion site, four-coordinated by Ca, was located by difference Fourier analysis and refined with F scattering factors. Two octahedral sites (Ti1 and Fe2) are occupied by mainly Ti and Fe (super 3+) , replacing each other whereas the octahedral site Mn1 hosts Mn (super 2+) and Fe (super 2+) . The new structure refinements and chemical analyses lead to the simplified chemical formula (Ca (sub 7.8) Na (sub 0.8) Mn (sub 0.5) REE (sub 0.4) ) (sub Sigma 9.5) (Ti (sub 3.9) Fe (super 3+) (sub 2.1) Fe (super 2+) (sub 0.9) Mn (super 2+) (sub 0.1) ) (sub Sigma 7) (AsO (sub 3) ) (sub 14) F (sub 0.5) . According to our findings, there is no evidence for either H (sub 2) O or OH in the structure. In contrast to the original study of 1977, the structure has no significant cation vacancies and is based on 14 AsO (sub 3) groups per formula unit, not on 12 AsO (sub 3) as previously suggested.


ISSN: 0935-1221
EISSN: 1617-4011
Serial Title: European Journal of Mineralogy
Serial Volume: 30
Serial Issue: 4
Title: New data on cafarsite; reinvestigation of its crystal structure and chemical composition
Affiliation: University of Bern, Institute of Geological Sciences, Mineralogical Crystallography, Bern, China
Pages: 859-868
Published: 20180531
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Germany
References: 12
Accession Number: 2018-064805
Categories: Mineralogy of non-silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 7 tables
N46°19'44" - N46°19'44", E08°12'59" - E08°12'59"
Secondary Affiliation: Yamaguchi University, JPN, Japan
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2018, American Geosciences Institute. Abstract, copyright, Schweizerbart'sche Verlagsbuchhandlung. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201835
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