Redetermination of clinobarylite, BaBe2Si2O7

• Published in: Acta Crystallographica Section E Structure Reports Online
• Main Authors: Adrien J. Di Domizio, Robert T. Downs, Hexiong Yang
• Format: Article in Journal/Newspaper
• Language: English
• Published: International Union of Crystallography 2012
• Subjects: Crystallography; QD901-999; Khibiny; Kola Peninsula; kola peninsula
• Online Access: https://doi.org/10.1107/S1600536812040457; https://doaj.org/article/603c16c2e9e54a699b5d1c18ab3dac6e

Clinobarylite, ideally BaBe2Si2O7 (chemical name barium diberyllium disilicate), is a sorosilicate mineral and dimorphic with barylite. It belongs to a group of compounds characterized by the general formula BaM2+2Si2O7, with M2+ = Be, Mg, Fe, Mn, Zn, Co, or Cu, among which the Be-, Fe-, and Cu-members have been found in nature. The crystal structure of clinobarylite has been re-examined in this study based on single-crystal X-ray diffraction data collected from a natural sample from the type locality (Khibiny Massif, Kola Peninsula, Russia). The structure of clinobarylite can be considered as a framework of BeO4 and SiO4 tetrahedra, with one of the O atoms coordinated to two Be and one Si, one coordinated to two Si, and two O atoms coordinated to one Si and one Be atom. The BeO4 tetrahedra share corners, forming chains parallel to the c axis, which are interlinked by the Si2O7 units oriented parallel to the a axis. The Ba2+ cations (site symmetry m.) are in the framework channels and are coordinated by eleven O atoms in form of an irregular polyhedron. The Si—Obr (bridging O atom, at site symmetry m.) bond length, the Si—Onbr (non-bridging O atoms) bond lengths, and the Si—O—Si angle within the Si2O7 unit are in marked contrast to the corresponding values determined in the previous study [Krivovichev et al. (2004). N. Jb. Miner. Mh. pp. 373–384].