Ardennite is a mixed-anion silicate with ideal chemical formula (Mn,Ca,Mg)4[Al,Fe3+)5Mg](AsO4) (SiO4)2(Si3O10)(OH)6). From the structural point of view, it may be regarded as a member of a polytypic family formed by two different kinds of regularly alternating layers. Such a prototypic family is conveniently described in terms of the OD-theory. The results of a combined chemical and HRTEM study are presented for ardennite sampled at two different localities - Western Alps, France and Evvia island, Greece. A plausible structural model for the most common complex polytype of ardennite is suggested with a doubled c period. Contrarily, ardennite from the Western Alps presents neither significant deviations from ideal stoichiometry nor evidence for polytypic behaviour.

Crystal chemistry, HRTEM analysis and polytypic behaviour of ardennite

PASERO, MARCO;
1991-01-01

Abstract

Ardennite is a mixed-anion silicate with ideal chemical formula (Mn,Ca,Mg)4[Al,Fe3+)5Mg](AsO4) (SiO4)2(Si3O10)(OH)6). From the structural point of view, it may be regarded as a member of a polytypic family formed by two different kinds of regularly alternating layers. Such a prototypic family is conveniently described in terms of the OD-theory. The results of a combined chemical and HRTEM study are presented for ardennite sampled at two different localities - Western Alps, France and Evvia island, Greece. A plausible structural model for the most common complex polytype of ardennite is suggested with a doubled c period. Contrarily, ardennite from the Western Alps presents neither significant deviations from ideal stoichiometry nor evidence for polytypic behaviour.
1991
Pasero, Marco; Reinecke, T.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11568/18669
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