Russian Mineralogical Society
RMS Annual Session combined with the Fedorov Session 2012
The structure of layer, the layer order and charoite polytypes

RMS-DPI code:  2012-1-167-0
Scientific session:  F1. Mineralogical crystallogrpaphy and crystal chemistry
Author listing:  Rozhdestvenskaya I.V., Mugnaioli E., Czank M., Depmeier W., Kolb U.
Principal author:  Rozhdestvenskaya Ira Vasilievna
Language:  Russian
Abstract - Summary 
(short description):
The structure of charoite, (K,Sr,Ba,Mn)15-16(Ca,Na)32[(Si70(O,OH)180)](OH,F)4.0ĚnH2O, (a = 31.96(6), b = 19.64(4), c = 7.09(1) Å, b = 90.0(1)░, V = 4450(24) Å3, space group P21/m) can be visualized as being composed of three different dreier silicate chains, which occur between ribbons of edge-sharing octahedra. From [010] SAED patterns on various single fibres it was found that charoite can form four different polytypes. Different polytypes are form by the shift on c/2 of tetrahedral chains along the octahedral bands in the neighbour unit cells. Charoite polytypism can be explained on the base of the OD-theory as a sequence of layers with parameters b, c, a/2 connected by a screw axis 2½ parallel to c.
Keywords: charoite, polytype
Date of presentation:  09/10/2012
Presentation Place:  Mining University, foyer of the Assembly Hall
RMS-DPI code:  2012-1-167-0
Proceeedings volume 
in the RMS catalogue:
Mineralogy in Ó whole space of the word.
Status:  preprint
Accepted:  28/08/2012
Contact author(s):  Rozhdestvenskaya, Ira Vasilievna

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