Crystal-structure refinement of synthetic Fe- and Mg-staurolite by Rietveld analysis of X-ray powder-diffraction data
Koch-Müller, Monika; Kahlenberg, Volker; Bubenick, Wolf; Gottschalk, Matthias
European Journal of Mineralogy Volume 10 Number 3 (1998), p. 453 - 460
published: Jun 22, 1998
manuscript accepted: Dec 29, 1997
manuscript received: Dec 19, 1996
ArtNo. ESP147051003005, Price: 29.00 €
Abstract The crystal structure of Fe-staurolite, synthesized at 5 and 25 kbar and 680°C, and of Mg-staurolite, synthesized at 25 kbar and 700°C, has been refined from X-ray powder-diffraction data using the Rietveld method in the space group Ccmm. The study was aimed to get insight into the distribution of Fe2+, Mg and Al at the tetrahedral T2 and the octahedral M4 sites. Fe-staurolite synthesized at 25 kbar differs from that at 5 kbar by a lower Fe2+ content (2.84 instead of 3.12 pfu) and higher Al content (0.60 instead of 0.32 pfu) at T2. Mg-staurolite synthesized at 25 kbar differs from the 25-kbar Fe-staurolite by higher occupancy of Mg at M4 (0.88 pfu), compared with 0.20 Fe2+ pfu in the case of Fe-staurolite, accompanied with less Mg at T2 (2.12 pfu) and only a small amount of Al at T2 (0.16 pfu).