NEW INSIGHT INTO THE CRYSTAL STRUCTURE OF ORTHORHOMBIC EDINGTONITE: EVIDENCE FOR A SPLIT BA SITE

Abstract

Orthorhombic edingtonite has been found coexisting with tetragonal edingtonite in a specimen from Ice River, British Columbia, Canada. We report data on the composition and crystal structure of the orthorhombic sample. Lattice parameters are: a = 9.5341(6), b = 9.6446(6), c = 6.5108(7)Å, V = 598.68(8)Å ³ . The crystal structure was refined in space group P 2 1 2 1 2 to R1 = 1.8% using 879 observed reflections. For the first time, evidence for splitting of the extra-framework Ba site in two different sites (Ba1, Ba2), ~0.37 Å apart, is demonstrated. A comparison with the published crystal structures of tetragonal and orthorhombic edingtonite is made. The present result supports the suggestion that the two edingtonite phases are a consequence of different nucleation phenomena and not different physicochemical conditions.