X-ray and electron diffraction study of penfieldite: average structure and multiple cells
- 1 June 1995
- journal article
- Published by Mineralogical Society in Mineralogical Magazine
- Vol. 59 (395) , 341-347
- https://doi.org/10.1180/minmag.1995.059.395.17
Abstract
Penfieldite is a lead hydroxychloride mineral with composition Pb2Cl3(OH). It belongs to the hexagonal system, space group P, a = 11.393(3), c = 4.024(1) Å. The 4 Å c parameter corresponds to the basic sub-cell, whereas modulated structures are known with a true c axis 12 times longer. The average crystal structure of penfieldite has been solved with direct methods and refined to Rw = 0.041 for 871 refections collected with Mo-Kα radiation. The chemical and structural relationships between penfeldite and laurelite, Pb2F3(F,Cl,OH), are briefly discussed. An electron diffraction study of penfieldite revealed the occurrence, besides the common modulated structure with C = 12c, of domains with a 15c periodicity. Moreover, a 9c periodicity has been observed in crystals heated at 180°C Penfieldite is quickly destroyed above 200°C.Keywords
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