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Crystal structure of mattheddleite: a Pb, S, Si phase with the apatite structure

Published online by Cambridge University Press:  05 July 2018

I. M. Steele*
Affiliation:
Department of Geophysical Sciences, University of Chicago, Chicago IL 60637, USA
J. J. Pluth
Affiliation:
Department of Geophysical Sciences, University of Chicago, Chicago IL 60637, USA Consortium for Advanced Radiation Sources, University of Chicago, Chicago IL 60637, USA Materials Research Science and Engineering Center, University of Chicago, Chicago IL 60637, USA
A. Livingstone
Affiliation:
6, St. Ronan’s Terrace, Innerleithen, Peeblesshire EH44 6RB, UK

Abstract

The crystal structure of mattheddleite (Pb5(Si1.5S1.5)O12(Cl0.57OH0.43), P63/m, a = 10.0056(6), c = 7.4960(9) Å) from Leadhills, Scotland has been determined to R = 0.065. The structure is that of apatite where Pb replaces Ca, equal amounts of S and Si replace P and the X anion is OH + Cl. The composition deduced from the structural refinement differs from that of microprobe analyses by giving full occupancy of the tetrahedral site and equal Si and S to preserve charge balance. We conclude that the microprobe analysis is incorrect possibly due to large and inaccurate absorption corrections. For the crystal analysed, the X anion position is zoned from an OH-rich interior to a Cl-rich exterior. The Pb(2) atom is disordered which may be analogous to the disordering of the Ca(2) site in Cl-rich, Ca apatites.

Type
Research Article
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2000

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