Crystal structure of Cr-bearing Mg3BeAl8O16, a new polytype of magnesiotaaffeite-2N′2S

Acta Crystallographica Section E: Crystallographic Communications

ter, J.¹  Malcherek, T.²  Schlü⁴ 

[1] Centrum füMineralogisch-Petrographisches Institut, Universitär Naturkunde (CeNak), Mineralogisches Museum, Universität Hamburg, Grindelallee 48, 20146 Hamburg, Germany

关键词: CRYSTAL STRUCTURE;    MAGNESIOTAAFFEITE;    GEMSTONES;    POLYTYPISM;    POLYSOMATISM;    MODULAR STRUCTURE;   

DOI  :  10.1107/S2056989016010215

学科分类：数学（综合）

来源: International Union of Crystallography

【 摘 要 】

The crystal structure of a new polytype of magnesiotaaffeite-2N′2S, ideally Mg3BeAl8O16 (trimagnesium beryllium octa­aluminium hexa­deca­oxide), is described in space-group symmetry P-3m1. It has been identified in a fragment of a mineral sample from Burma (Myanmar). The new polytype is composed of two Mg2Al4O8 (S)- and two BeMgAl4O8 (N′)-modules in a stacking sequence N′SSN′′ which differs from the N′SN′S-stacking sequence of the known magnesiotaaffeite-2N′2S polytype. The crystal structure can be derived from a close-packed arrangement of O atoms and is discussed with regard to its polytypism and its Cr3+ chromophore content.

【 授权许可】

CC BY