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Metavivianite, Fe (super 2+) Fe (super 3+) (sub 2) (PO (sub 4) ) (sub 2) (OH) (sub 2) .6H (sub 2) O; new data and formula revision

N. V. Chukanov, R. Scholz, S. M. Aksenov, R. K. Rastsvetaeva, I. V. Pekov, D. I. Belakovskiy, K. Krambrock, R. M. Paniago, A. Righi, R. F. Martins, F. M. Belotti and V. Bermanec
Metavivianite, Fe (super 2+) Fe (super 3+) (sub 2) (PO (sub 4) ) (sub 2) (OH) (sub 2) .6H (sub 2) O; new data and formula revision
Mineralogical Magazine (June 2012) 76 (3): 725-741

Abstract

The composition, structure, X-ray powder diffraction pattern, optical properties, density, infrared, Raman and Mossbauer spectra, and thermal properties of a homogeneous sample of metavivianite from the Boa Vista pegmatite, near Galileia, Minas Gerais, Brazil are reported for the first time. Metavivianite is biaxial (+) with alpha = 1.600(3), beta = 1.640(3), gamma = 1.685(3) and 2V (sub meas) = 85(5) degrees . The measured and calculated densities are D (sub meas) = 2.56(2) and D (sub calc) = 2.579 g cm (super -3) . The chemical composition, based on electron-microprobe analyses, Mossbauer spectroscopy (to determine the Fe (super 2+) :Fe (super 3+) ratio) and gas chromatography (to determine H (sub 2) O) is MgO 0.70, MnO 0.92, FeO 17.98, Fe (sub 2) O (sub 3) 26.60, P (sub 2) O (sub 5) 28.62, H (sub 2) O 26.5; total 101.32 wt.%. The empirical formula is (Fe (super 3+) (sub 1.64) Fe (super 2+) (sub 1.23) Mg (sub 0.085) Mn (sub 0.06) ) (sub Sigma 3.015) (PO (sub 4) ) (sub 1.98) (OH) (sub 1.72) .6. 36H (sub 2) O. Metavivianite is triclinic, P1i, a = 7.989(1), b = 9.321(2), c = 4.629(1) Aa, alpha = 97.34(1), beta = 95.96(1), gamma = 108.59(2) degrees , V = 320.18(11) Aa (super 3) and Z = 1. The crystal structure was solved using a single-crystal techniques to an agreement index R = 6.0%. The dominant cations in the independent sites are Fe (super 2+) and Fe (super 3+) , with multiplicities of 1 and 2, respectively. The simplified crystal-chemical formula for metavivianite is Fe (super 2+) (Fe (super 3+) ,Fe (super 2+) ) (sub 2) (PO (sub 4) ) (sub 2) (OH,H (sub 2) O) (sub 2) .6H (sub 2) O; the endmember formula is Fe (super 3+) (sub 2) (PO (sub 4) ) (sub 2) (OH) (sub 2) .6H (sub 2) O, which is dimorphous with ferrostrunzite.


ISSN: 0026-461X
EISSN: 1471-8022
Coden: MNLMBB
Serial Title: Mineralogical Magazine
Serial Volume: 76
Serial Issue: 3
Title: Metavivianite, Fe (super 2+) Fe (super 3+) (sub 2) (PO (sub 4) ) (sub 2) (OH) (sub 2) .6H (sub 2) O; new data and formula revision
Affiliation: Russian Academy of Sciences, Institute of Problems of Chemical Physics, Chernogolovka, Russian Federation
Pages: 725-741
Published: 201206
Text Language: English
Publisher: Mineralogical Society, London, United Kingdom
References: 35
Accession Number: 2012-092180
Categories: Mineralogy of non-silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 9 tables
S23°30'00" - S14°00'00", W51°00'00" - W39°45'00"
Secondary Affiliation: Federal University of Ouro Preto, BRA, BrazilRussian Academy of Sciences, Institute of Crystallography, RUS, Russian FederationMoscow State University, RUS, Russian FederationRussian Academy of Sciences, Fersman Mineralogical Museum, RUS, Russian FederationFederal University of Minas Gerais, BRA, BrazilFederal University of Itajuba, BRA, BrazilUniversity of Zagreb, HRV, Croatia
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, Copyright, Mineralogical Society of Great Britain and Ireland. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201248
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