Original paper

(010) disorder, partial Si,Al ordering, and Ca distribution in triclinic (C1) epistilbite

Yang, Ping; Armbruster, Thomas

European Journal of Mineralogy Volume 8 Number 2 (1996), p. 263 - 272

17 references

published: Apr 26, 1996
manuscript accepted: Oct 26, 1995
manuscript received: Jun 1, 1995

DOI: 10.1127/ejm/8/2/0263

BibTeX file

ArtNo. ESP147050802002, Price: 29.00 €

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Abstract The crystal structure of epistilbite, Na0.3K0.2Ca2.7Al6.2Si17.9O48· 16 H2O, from Gibelsbach, Fiesch (Valais, Switzerland) was refined from X-ray single-crystal data at 100 K and 293 K in space group Cl (100 K: a = 9.051(3), b = 17.689(6), c = 10.152(7) Å, α = 89.93(4), ß =124.35(4), γ= 89.95(3)°; 293 K: a = 9.083(1), b = 17.738(3), c = 10.209(1) Å, α = 89.95(1), ß = 124.58(1), γ= 90.00(1)°). In contrast to previous studies where the space groups C2 or C2/m were assumed, reflection intensities clearly suggest triclinic symmetry. The reason for the symmetry lowering from monoclinic C2 to triclinic C1 is partial Si,Al ordering accompanied by a preferred distribution of the channel cations close to the underbonded oxygen atoms of the tetrahedral framework. The hitherto enigmatic occurrence of two domain variants (A, B) formed by different tetrahedral configurations could be modelled by (010) disorder caused by a local mirror plane.


epistilbitezeoliteSi,Al-orderingdisordercrystal structure