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OD Interpretation of Pyroxenes
Author(s) -
Sedlacek P.,
Zedler A.,
Reinecke K.
Publication year - 1979
Publication title -
kristall und technik
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.377
H-Index - 64
eISSN - 1521-4079
pISSN - 0023-4753
DOI - 10.1002/crat.19790140905
Subject(s) - silicate , octahedron , tetrahedron , crystallography , symmetry (geometry) , crystal twinning , pyroxene , layer (electronics) , geology , mineralogy , materials science , chemistry , geometry , mathematics , composite material , crystal structure , olivine , microstructure , organic chemistry
The structures of pyroxenes are interpreted as OD structures consisting of layers. The symmetry relations of the idealized structures of “high pyroxenes”, consisting of only one kind of silicate sheets are described by the OD groupoid family:In this case the tetrahedral layers (OD layers) are identical with silicate sheets and the octahedral layers (OD layers) are identical with the chemical octahedral sheets, apart from the fact, that the O atoms are considered to belong partly to one and partly to the other idealized layer. In the idealized pyroxene structures, which are called in this paper “low pyroxenes”, every second silicate sheet is of lower symmetry. A silicate sheet of higher symmetry is considered as an OD layer, called tetrahedral layer. An OD layer of the other kind, called compound layer, consists of one silicate sheet of lower symmetry with an octahedral sheet attached to it on either side. With this definition of the two kinds of layers, the OD groupoid family has the following symbol:Polymorphism, disorder, twinning and parallel intergrowth are explained on this basis.