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Straetlingite; crystal structure, chemistry, and a reexamination of its polytype vertumnite

Romano Rinaldi, Michele Sacerdoti and Elio Passaglia
Straetlingite; crystal structure, chemistry, and a reexamination of its polytype vertumnite
European Journal of Mineralogy (December 1990) 2 (6): 841-849

Abstract

The crystal structure of stratlingite Ca (sub 2) Al(AlSi)O (sub 2) (OH) (sub 10) . 2.25H (sub 2) O (Z=3) from Montalto di Castro (VT), Italy, was solved and refined in space group R3m (isotropic R=0.080). The structure contains ordered Ca (super VII) and A1 (super VI) polyhedra fully occupying "octahedral" brucite-type layers (main layers of all aluminate hydrates) hydrogen bonded to partially occupied double tetrahedral (Si/Al=1) layers formed by sharing the apical oxygens of the two component tetrahedral sheets. Cell dimensions: alpha =5.745(7); c=37.77(l)A imply the stacking of three main ("octahedral") layers and three "interlayers" (double-T layers) along the [001] direction as compared with two main layers for the mineral vertumnite which has therefore been proved to be a polytype with a c parameter equal to two thirds that of stratlingite. New chemical data on vertumnite holotype, obtained by accurate electron probe microanalysis together with those obtained for stratlingite holotype as well as for this second occurrence, show very close analogies between the two mineral species also in terms of their crystal chemistry, with a tendency of stratlingite to have a larger proportion of vacant T sites and a higher hydration degree than the polytype vertumnite.


ISSN: 0935-1221
Serial Title: European Journal of Mineralogy
Serial Volume: 2
Serial Issue: 6
Title: Straetlingite; crystal structure, chemistry, and a reexamination of its polytype vertumnite
Affiliation: Univ. Perugia, Dip. Sci. Terra, Perugia, Italy
Pages: 841-849
Published: 199012
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Federal Republic of Germany
References: 18
Accession Number: 1994-008244
Categories: Mineralogy of silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 4 tables
N41°13'60" - N42°49'60", E11°30'00" - E14°00'00"
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from Geoline, Bundesanstalt fur Geowissenschaften und Rohstoffe, Hanover, Germany
Update Code: 199404
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