Abstract
In xonotlite, which has a structure built up of a column parallel to b, various polytypic structural variants may occur which have various periodicities along a and c. Since this phenomenon may be looked upon as a specific polytypism which occurs in two directions, a term‘compound polytypism’has been suggested.
In order to represent the polytypic variants of xonotlite, the use has been proposed of a set of three symbols‘E, A, C’each specifying a stacking mode of columns. The number of the possible polytypes and the space groups were enumerated and listed based on a new version of the Gard's notation.
