Crystal structure of Schüllerite, a new mineral of the heterophyllosilicate family

Abstract

90 The representative family of heterophyllosilicates includes, in particular, the lamprophyllite group. The structure of the lamprophyllite group minerals is based on three layer blocks composed of the cationic wall made of edge sharing octahedra and the anionic net work of Si diortho groups combined by Ti semioctahe dra. The anionic networks are attached to the octahe dral layer through the vertices of the tetrahedra and semioctahedra. Large A cations (Sr, Ba, K, Ca, and Na) are located between the heterosilicate НОН layers (Н is hetero, O is octahedra), (Fig. 1). In particular, lamprophyllite described initially as a strontium min eral [1] was later described as having a variable compo sition as regards the large cations located in the inter layer spacings. Baritolamprophyllite and its Ba,Na ordered analog, nabalamprophyllite, are Ba domi nant members of the lamprophyllite family.