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The crystal chemistry of the graftonite-beusite minerals

Kimberly T. Tait, Frank C. Hawthorne and Michael A. Wise
The crystal chemistry of the graftonite-beusite minerals
The Canadian Mineralogist (August 2013) 51 (4): 653-662


The crystal structures of seven members of the graftonite-beusite series, ideally (Fe (super 2+) , Mn (super 2+) ,Ca) (sub 3) (PO (sub 4) ) (sub 2) , monoclinic P2 (sub 1) /c, a 8.77-8.81, b 11.43-11.58, c 6.13-6.17 Aa, beta 99.19-99.32 degrees , V 607.5-617.7 Aa (super 3) , have been refined to R (sub 1) indices of 2.1-3.7% using approximately 1300-1600 unique observed reflections (F (sub o) > 5sigma F) collected using a single-crystal diffractometer equipped with MoKalpha X-radiation. The crystals used in the collection of the X-ray data were subsequently analyzed with an electron microprobe and the structural and microprobe results were used to assign site populations. The refined site-scattering values and linear variation in mean bond-length as a function of aggregate-cation radius indicate that Ca is completely ordered at the M(1) site. Similarly Mn is ordered at the M(1) and M(3) sites, with any excess Mn occurring at M(2), and Mg is completely ordered at M(2). Detailed consideration of incident bond-valence sums at the three M sites indicates that the coordination numbers of the M(1), M(2), and M(3) sites are [8], [5], and [6], respectively, although the differences between these and [7], [5], and [5] are very small. Ca is dominant at the M(1) site in a previously refined beusite structure, and there are compositions reported here and elsewhere in which Ca is dominant at M(1) in graftonite-like compositions, indicating the potential for new mineral species in this group.

ISSN: 0008-4476
EISSN: 1499-1276
Coden: CAMIA6
Serial Title: The Canadian Mineralogist
Serial Volume: 51
Serial Issue: 4
Title: The crystal chemistry of the graftonite-beusite minerals
Affiliation: University of Manitoba, Department of Geological Sciences, Winnipeg, MB, Canada
Pages: 653-662
Published: 201308
Text Language: English
Publisher: Mineralogical Association of Canada, Ottawa, ON, Canada
References: 33
Accession Number: 2014-004235
Categories: Mineralogy of non-silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 8 tables
Secondary Affiliation: Smithsonian Institution, USA, United States
Country of Publication: Canada
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, copyright, Mineralogical Association of Canada. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201404
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