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Crystal structure and revision of the chemical formula of georgiadesite, Pb4(AsO3)Cl4(OH)

Published online by Cambridge University Press:  05 July 2018

M. Pasero  and
D. Vacchiano
M. Pasero*
Affiliation:
Dipartimento di Scienze della Terra, Università di Pisa e CNR-CSGSDA, Via S. Maria 53, I-56126 Pisa, Italy
D. Vacchiano
Affiliation:
Dipartimento di Scienze della Terra, Università di Pisa e CNR-CSGSDA, Via S. Maria 53, I-56126 Pisa, Italy
*
*E-mail: pasero@dst.unipi.it
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Abstract

The crystal structure of the rare secondary lead mineral georgiadesite has been solved from single-crystal X-ray diffraction data (R = 0.071). The structure can be visualized in terms of alternating puckered (100) layers of [Pbϕ6] octahedra and [Pbϕ8] bicapped trigonal prisms (ϕ = generic anion). Lead also occurs in irregular, lopsided polyhedra. This structural study shows unambiguously that arsenic occurs as As3+ and not as As5+. The chemical formula of georgiadesite has therefore been revised, on structural grounds, to Pb4(AsO3)Cl4(OH).

Keywords

georgiadesitecrystal structurelead halideslone-pair effectLaurion (Greece)
Type
Research Article
Information
Mineralogical Magazine , Volume 64 , Issue 5 , October 2000 , pp. 879 - 884
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2000

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