The Crystal Structure of Buttgenbachite

L. Fanfani, A. Nunzi, P. F. Zanazzi and A. R. Zanzari
Istituto di Mineralogia, Università di Perugià, Perugia, Italy

Summary: The crystal structure of buttgenbachite from Likasi (Congo) 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 refinement to an R index 0·055 for 328 independent observed reflections. The cell content resulting from the structural analysis is Cu36·6Cl6·7(NO3)2·6(OH)63·9.2·1 H2O. The space group is P63/mmc with a = 15·750 Å and c = 9·161Å. The buttgenbachite structure is not completely ordered. It consists of a rigid three-dimensional skeleton formed by Cu co-ordination polyhedra sharing edges and corners. The large channels in the framework show a zeolite-like nature; inside the channels the disorder is caused by the different orientations of nitrate groups and by the occurrence of the substitution 2NO3−⇄Cl−. The crystal structure of buttgenbachite is closely related to that of connellite. The mechanism of forming an isomorphous series is discussed: the present study shows that the replacement is more complicated than was supposed in the literature.

Mineralogical Magazine; September 1973 v. 39; no. 303; p. 264-270; DOI: 10.1180/minmag.1973.039.303.02
© 1973, The Mineralogical Society
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