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The crystal structure of dundasite

Published online by Cambridge University Press:  05 July 2018

G. Cocco
Affiliation:
Istituto di Mineralogia, Università di Perugia, Italy
L Fanfani
Affiliation:
Istituto di Mineralogia, Università di Perugia, Italy
A. Nunzi
Affiliation:
Istituto di Mineralogia, Università di Perugia, Italy
P. F. Zanazzi
Affiliation:
Istituto di Mineralogia, Università di Perugia, Italy

Summary

The crystal structure of dundasite from Gonnesa (Italy) was solved by a three-dimensional Patterson function computed using intensity data collected photographically by the Weissenberg method, and refined by successive Fourier maps and least-squares cycles to an R index 0·.066 for 505 independent observed reflections.

The chemical formula resulting from the structural analysis is PbAl2(CO3)2(OH)4·H2O. The mineral is orthorhombic, space group Pbnm, with a 9·08 Å, b 16·37 Å, c 5·62 Å. The dundasite structure consists of a three-dimensional framework of coordination polyhedra around Pb and Al. Pb ions are coordinated by nine oxygen atoms with distances ranging from 2·53 to 2·91 Å. Al ions show the usual octahedral coordination with average Al-O distance 1.90 Å. C-O mean distances are 1·28 and 1·27 Å for the two non-equivalent CO3 groups. The water molecules are not coordinated by the cations.

Type
Research Article
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1972

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