Subsilicic ferrian aluminian diopside from the Chelyabinsk coal basin (Southern Urals) – an unusual clinopyroxene
Kabalov, Yurii K.; Oeckler, Oliver; Sokolova, Elena V.; Mironov, Aleksei B.; Chesnokov, Boris V.
European Journal of Mineralogy Volume 9 Number 3 (1997), p. 617 - 622
published: Jun 2, 1997
manuscript accepted: Dec 17, 1996
manuscript received: Apr 11, 1996
ArtNo. ESP147050903009, Price: 29.00 €
Abstract The crystal structure of a technogeneous Fe3+-rich diopside from the Chelyabinsk coal basin, Southern Urals, has been refined from X-ray powder diffraction data (CoKα radiation) using the Rietveld method (Rwp = 0.049). The refined monoclinic cell dimensions (Z = 4, space group C2/c) are a = 9.786(2) Å, b = 8.860(1) Å, c = 5.338(1) Å and ß = 105.87(1)°. This technog eneous mineral has previously been described as esseneite according to the empirical formula Ca1.00Fe3+0.51Ti0.02Al0.60Si1.43O6, but in contrast to ideal esseneite (end member: CaFe3+AlSiO6), Fe3+ ions are not restricted to the octahedral M(l) site, but are partitioned between the M(l) and the tetrahedral T site. Moessbauer spectroscopy indicates a Fe3+ distribution over the M(l) and T sites with a 2:1 ratio. Site occupancy refinement confirms that the M(l) site is occupied by 0.44(3) Mg, 0.35(3) Fe3+ and 0.20(3) Al, and the T site by 0.70(2) Si, 0.20(2) Al and 0.08(2) Fe3+ .