The crystal structure of spangolite, ideally Cu6Al(SO4)(OH)12Cl.3H2O, has been solved from single-crystal X-ray diffraction data. Three different refinements were carried out on three samples of spangolite from Italy (Arenas, Baratti and Rocca di S. Silvestro; final R(w) factors 0.029, 0.048 and 0.047, respectively). The crystal structure of spangolite is characterized by octahedral layers formed by Cu- and Al-centered octahedra in the ratio 6:1, with Cl- and (SO4)2- anions lying on the opposite sides of the layers, together with hydroxyls and water molecules placed between the layers. Spangolite is trigonal, space group P31c. Whereas the a parameter is very similar in all three samples ca. 8.27 angstrom, the c parameter range from 14.37 (Arenas) to 14.54 angstrom (Rocca di S. Silvestro). The increasing of the c axis is attributed, in the latter case, to the partial substitution Cl- = (OH)-+H2O.
|Autori:||MERLINO S; PASERO M; SABELLI C; TROSTI-FERRONI R|
|Titolo:||Crystal structure refinements of spangolite, a hydrated basic sulphate of copper and aluminum, from three different occurrences|
|Anno del prodotto:||1992|
|Appare nelle tipologie:||1.1 Articolo in rivista|