Redetermination of clinobaryl­ite, BaBe2Si2O7

• Published in: Acta Crystallographica Section E Structure Reports Online
• Main Authors: Domizio, Adrien J. Di, Downs, Robert T., Yang, Hexiong
• Format: Text
• Language: English
• Published: International Union of Crystallography 2012
• Subjects: Inorganic Papers; Khibiny; Kola Peninsula; kola peninsula
• Online Access: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3470124; http://www.ncbi.nlm.nih.gov/pubmed/23125568; https://doi.org/10.1107/S1600536812040457

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 BaM 2+ 2Si2O7, with M 2+ = 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].