Reference : Graulichite-(Ce), a new arsenate mineral from the Stavelot Massif, Belgium
Scientific journals : Article
Physical, chemical, mathematical & earth Sciences : Earth sciences & physical geography
Graulichite-(Ce), a new arsenate mineral from the Stavelot Massif, Belgium
Hatert, Frédéric mailto [Université de Liège - ULiège > Département de géologie > Minéralogie et cristallochimie >]
Pasero, Marco [> > > >]
Fransolet, André-Mathieu mailto [Université de Liège - ULiège > Département de géologie > Minéralogie et cristallochimie >]
Lefèvre, Pierre [ > > ]
European Journal of Mineralogy
E Schweizerbartsche Verlags
Yes (verified by ORBi)
[en] graulichite-(Ce) ; new arsenate mineral ; REE ; crandallite group ; Hourt ; Stavelot Massif ; Belgium ; crystal structure
[en] Graulichite-(Ce), ideally CeFe33+(AsO4)(2)(OH)(6), is a new mineral species from Hourt, Stavelot Massif, Belgium. It occurs in the most altered parts of a Devillian quartzite (Lower to Middle Cambrian), in close association with arsenopyrite, scorodite, mimetite, pharmacosiderite, and goethite. Graulichite-(Ce) forms 80 to 150 mum spherical aggregates of rhombohedral crystals, 50 to 80 mum length, which show the forms {10 (1) over bar2} and {10 (11) over bar}. The mineral is transparent and exhibits a light-green to brownish colour, with a resinous lustre. It is non-fluorescent and shows an irregular fracture, without any perceptible cleavage. The calculated density is 4.42 g/cm(3). Graulichite-(Ce) is uniaxial negative, with a mean refractive index close to 1.97(1) (lambda=590 nm), pleochroic from light green to yellowish. Electron microprobe analyses gave As2O5 31.20, P2O5 0.03, SO3 0.06, SiO2 0.03, Al2O3 3.09, Fe2O3 30.65, SrO 0.24, PbO 0.07, BaO 3.95, CaO 0.03, La2O3 2.26, Ce2O3 15.73, Nd2O3 2.08, H2O (calc.) 8.37, total 97.79 wt. %. The resulting empirical formula, calculated on the basis of 6 cations, is (Ce0.67Ba0.18La0.10Nd0.09Sr0.02)(Sigma1.06) (Fe2.683+Al0.42)(Sigma3.10)[(As(1.89)S(.001)square(0.10))(Sigma2.00)O-8][(OH)(5.57)(H2O)(0.43)](Sigma6.00). The single-crystal unit-cell parameters are a=7.288(2) and c=16.812(9) Angstrom, space group R (3) over barm. The seven strongest lines in the X-ray powder-diffraction pattern [d(in Angstrom)(I)(hkil)] are: 3.052(100)(11 (2) over bar3), 3.636(40)(11 (2) over bar0), 2.239(35)(10 (1) over bar7), 1.817(35)(22 (4) over bar0), 2.792(30)(0006), 5.906(25)(10 (1) over bar1), 1.968(25)(30 (3) over bar3). Graulichite-(Ce) is the iron analogue of arsenoflorencite-(Ce), and belongs to the crandallite mineral group, with the alunite-type structure. The crystal structure of graulichite-(Ce) has been refined, based on single-crystal X-ray diffraction data, to R=0.048.

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