Article (Scientific journals)
A structural, infrared, and Mossbauer spectral study of rosemaryite, NaMnFe3+Al(PO4)(3)
Hatert, Frédéric; Hermann, R. P.; Fransolet, André-Mathieu et al.
2006In European Journal of Mineralogy, 18 (6, NOV-DEC), p. 775-785
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Keywords :
rosemaryite; phosphate mineral; structure refinement; Mossbauer spectroscopy; infrared spectroscopy
Abstract :
[en] Rosemaryite, ideally NaMnFe(3+)AI(PO4)(3), has been collected in the Buranga pegmatite, Rwanda. A single-crystal structure refinement was performed to R-1 = 4.01 %, in the P2(1)/n space group, with a = 12.001(2), b = 12.396(1), c = 6.329(1) angstrom, beta 114.48(1)degrees, Vol. = 856.9(2) angstrom(3), Z = 4. The crystal structure and cation distributions are similar to those of ferrorosemaryite, NaFe2+Fe3+Al(PO4)(3), and qingheiite, Na2MnMgAl(PO4)(3), but aluminium predominantly occurs in the M(2a) site, not in the M(2b) site as observed in ferrowyllieite, Na2Fe22+Al(PO4)(3). The topologies of the X(1a) and X(1b) crystallographic sites are identical to those found in ferrorosemaryite, and correspond to a distorted octahedron and to a distorted cube, respectively. The [7+1]-coordinated X(2) site is a very distorted gable disphenoid, similar to the A(2)' site of the alluaudite structure. Mossbauer spectra have been obtained from 4.2 to 295 K, and fitted with a model including two Fe3+ and two Fe2+ doublets. The Fe2+ component corresponding to 2/3 of the Fe2+ spectral area and having a smaller quadrupole splitting of 2.63 mm/s at 15 K, is assigned to the Fe2+ on the M(2a) site, and the Fe2+ component with the larger quadrupole splitting of 3.17 mm/s at 15 K, is assigned to the Fe2+ on the M(1) site. Fe3+ is located only at the M(2a) and M(2b) sites, and the Fe3+ component corresponding to 3/4 of the Fe3+ and exhibiting the larger quadrupole spitting of 0.77 mm/s at 15 K, is most likely associated with Fe3+ on the M(2b) site. The infrared spectrum of rosemaryite shows absorption bands at 3450 and 1624 cm(-1), bands that arise from the vibrational modes of H2O and confirm the presence of water in the channels of the wyllieite structure. A comparison of both the Mossbauer spectra and structural data of rosemaryite with those of other phosphates of the alluaudite and wyllieite groups, is also presented.
Disciplines :
Earth sciences & physical geography
Author, co-author :
Hatert, Frédéric  ;  Université de Liège - ULiège > Département de géologie > Minéralogie et cristallochimie
Hermann, R. P.
Fransolet, André-Mathieu ;  Université de Liège - ULiège > Département de géologie > Minéralogie et cristallochimie
Long, G. J.
Grandjean, Fernande ;  Université de Liège - ULiège > Département de physique > Département de physique
Language :
English
Title :
A structural, infrared, and Mossbauer spectral study of rosemaryite, NaMnFe3+Al(PO4)(3)
Publication date :
2006
Journal title :
European Journal of Mineralogy
ISSN :
0935-1221
eISSN :
1617-4011
Publisher :
E Schweizerbartsche Verlags, Stuttgart, Germany
Volume :
18
Issue :
6, NOV-DEC
Pages :
775-785
Peer reviewed :
Peer Reviewed verified by ORBi
Available on ORBi :
since 05 March 2009

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