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The structure of braitschite, a calcium rare earth borate

Clare E. Rowland, Christopher L. Cahill and Jeffrey E. Post
The structure of braitschite, a calcium rare earth borate
American Mineralogist (January 2011) 96 (1): 197-201


The crystal structure of braitschite, Ca (sub 6.15) Na (sub 0.85) RE (sub 2.08) [B (sub 6) O (sub 7) (OH) (sub 3) (O,OH) (sub 3) ] (sub 4) (H (sub 2) O), is reported here in space group P6/m with unit-cell parameters a=12.1506(6), c=7.3678(4) Aa, and V=942.03(8) Aa (super 3) . Data were collected from a single crystal using a MoKalpha source and a CCD detector, solved by direct methods, and refined to an R factor of 2.81%. The mineral structure consists of hexaborate fundamental building blocks that polymerize along [001] and are bound by Ca (super 2+) and REE (super 3+) counter-ions. The framework forms hexagonal channels, which are occupied alternately by Ca (super 2+) cations and water molecules. In an investigation of its thermal stability, braitschite maintains its crystallinity to a temperature of 400 degrees C, after which it undergoes decomposition. Using Rietveld refinements against powder X-ray diffraction data, we were able to track the loss of water molecules in channels and hydroxyl groups in the covalent B-O network with increasing temperature.

ISSN: 0003-004X
EISSN: 1945-3027
Serial Title: American Mineralogist
Serial Volume: 96
Serial Issue: 1
Title: The structure of braitschite, a calcium rare earth borate
Affiliation: George Washington University, Department of Chemistry, Washington, DC, United States
Pages: 197-201
Published: 201101
Text Language: English
Publisher: Mineralogical Society of America, Washington, DC, United States
References: 22
Accession Number: 2011-012703
Categories: Mineralogy of non-silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 6 tables
N38°30'00" - N39°31'00", W110°13'00" - W109°02'60"
Secondary Affiliation: Smithsonian Institution, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, copyright, Mineralogical Society of America. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201108
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