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Saneroite; chemical and structural variations of manganese pyroxenoids with hydrogen bonding in the silicate chain

Mariko Nagashima and Thomas Armbruster
Saneroite; chemical and structural variations of manganese pyroxenoids with hydrogen bonding in the silicate chain
European Journal of Mineralogy (June 2010) 22 (3): 393-402

Abstract

Saneroite, Na (sub 1-1.5) Mn (sub 5) [Si (sub 5) O (sub 14) (OH)](Si,V,As)O (sub 3) (OH)(Z=2, space group P1), has only been reported from two localities: (1) Val Graveglia, Italy, and (2) Fianel, Switzerland. Samples from both localities were studied using electron-microprobe analysis (EMPA), semi-quantitative analysis of the Mn (super 2+) /Mn (super 3+) ratio based on the ratio of the X-ray intensities of the Mn L (sub beta ) and Mn L (sub alpha ) lines, and single-crystal X-ray diffraction methods. The structure has two Na sites (Na1 and Na2), which are 8-coordinated by O. Na1 is fully occupied whereas Na2 is partially occupied. Five crystallographically independent octahedral sites are occupied by Mn (mainly Mn (super 2+) with 10-20% Mn (super 3+) ), with additional small amounts of Ca and V (super 3+) . An undulating pyroxenoid-like chain is built by five SiO (sub 4) tetrahedra. A sixth tetrahedron, forming a branch of the chain, is occupied by V (super 5+) , Si (super 4+) and As (super 5+) . Structure refinements converged to R (sub 1) values of 2.47-2.89%. In agreement with bond-valence analyses, OH groups are found at the O7 and O19 positions. The relationships between donor and acceptor oxygen atoms and their hydrogen bonds in saneroite are O19-H19...O16 and O7-H7...O11. The O19...O16 and O7...O11 distances are 2.868(2)-2.876(2) and 2.475(2)-2.477(2) Aa, respectively. The latter hydrogen bond is extremely short and strong. Corresponding strong hydrogen-bonds were also found in scheuchzerite and several hydrous pyroxenoids with 3- and 5-periodic chains.


ISSN: 0935-1221
EISSN: 1617-4011
Serial Title: European Journal of Mineralogy
Serial Volume: 22
Serial Issue: 3
Title: Saneroite; chemical and structural variations of manganese pyroxenoids with hydrogen bonding in the silicate chain
Affiliation: University of Bern, Institute of Geological Sciences, Mineralogical Crystallography, Bern, Switzerland
Pages: 393-402
Published: 201006
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Federal Republic of Germany
References: 55
Accession Number: 2010-060659
Categories: Mineralogy of silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 10 tables
N36°30'00" - N47°30'00", E06°30'00" - E19°00'00"
N45°45'00" - N47°45'00", E05°49'60" - E10°30'00"
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, copyright, Schweizerbart'sche Verlagsbuchhandlung. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201033
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