Crystal Structure of Barstowite (3PbCl2·PbCO3-H2O)

I. M. Steele1, J. J. Pluth1, 2, 3 and C. J. Stanley4
1 Department of Geophysical Sciences, The University of Chicago, Chicago IL 60637, USA
2 Consortium for Advanced Radiation Sources, The University of Chicago, Chicago IL 60637, USA
3 Materials Research Science and Engineering Center, The University of Chicago, Chicago IL 60637, USA
4 Department of Mineralogy, Natural History Museum, Cromwell Road, London SW7 5BD, UK

Abstract: The crystal structure of barstowite (3PbCl2·PbCO3·H2O, P21/m, a = 4.2023(5), b = 9.2020(7), c = 16.6608(6)(Å), β = 91.829(9)°) from Bounds Cliff, St Endellion, Cornwall, has been determined to an R = 0.036. The structure can be described in terms of three layers stacked along [001] in the sequence ...CACBCACBC... to give a 16.7 Å repeat. Layer A consists of face-sharing PbCl8 distorted square antiprisms. Layer B is composed of Pb coordinated to 5 Cl and 2 O each with two H to form H2O groups. Layer C is formed by Pb coordinated to 5 Cl and 3 O which are from CO3 groups. The H positions are deduced and are H-bonded to O from carbonates. The structural details were in agreement with previous deductions based on infrared spectra.

Keywords: barstowite • phosgenite • crystal structure • Bounds Cliff • Cornwall

Mineralogical Magazine; December 1999 v. 63; no. 6; p. 901-907; DOI: 10.1180/002646199549005
© 1999, The Mineralogical Society
Mineralogical Society (www.minersoc.org)