Crystal structure and new formula of rameauite

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Marco E. Ciriotti
Messaggi: 31645
Iscritto il: ven 25 giu, 2004 11:31
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Crystal structure and new formula of rameauite

Messaggio da Marco E. Ciriotti » mer 15 giu, 2016 8:46

Prossima pubblicazione.

Referenza:
▪ Plášil, J., Škoda, R., Čeika, J., Bourgoin, V., Boulliard, J.-C. (2016): Crystal structure of the uranyl-oxide mineral rameauite. European Journal of Mineralogy, 28, (in press).

Abstract:
Rameauite is a rare supergene uranyl-oxide hydroxy-hydrate mineral that forms during hydration-oxidation weathering of uraninite. On the basis of single-crystal X-ray diffraction data collected on a microfocus source, rameauite is monoclinic, space group Cc, with a = 13.9458(19), b = 14.3105(19), c = 13.8959(18) Å, β = 118.477(14)°, V = 2437.7(6) Å3 and Z = 4, with Dcalc = 5.467 g cm-3. The structure of rameauite (R = 0.060 for 1698 unique observed reflections) contains sheets of the β-U3O8 topology, with both UO6 and UO7 bipyramids, which is similar to the sheets found in spriggite, ianthinite and wyartite. The sheets alternate with the interlayer, which contains K+, Ca2+ and H2O molecules. Interstitial cations are linked into infinite chains that extend along [10-1]. Adjacent sheets are linked through K–O, Ca–O and H-bonds. The structural formula of rameauite is K2Ca(H2[3]O)1(H2[5]O)4[(UO2)6O6(OH)4](H2[4]O)1. The empirical formula obtained from the average of eight electron-microprobe analyses is (on the basis of 6 U p.f.u.) K1.87(Ca1.10Sr0.04)Σ1.14[(UO2)6O6(OH)4.15]·6H2O. The Raman spectrum is dominated by U–O and O–H vibrations. A discussion of related uranyl-oxide minerals is given.
Marco E. Ciriotti

«Things are interesting only in so far as they relate themselves to other things»

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Marco E. Ciriotti
Messaggi: 31645
Iscritto il: ven 25 giu, 2004 11:31
Località: via San Pietro, 55 I-10073 Devesi/Cirié TO - Italy
Contatta:

Re: Crystal structure and new formula of rameauite

Messaggio da Marco E. Ciriotti » mer 11 gen, 2017 18:03

Pubblicazione effettuata.

Referenza:
▪ Plášil, J., Škoda, R., Čeika, J., Bourgoin, V., Boulliard, J.-C. (2016): Crystal structure of the uranyl-oxide mineral rameauite. European Journal of Mineralogy, 28, 959-967.
Marco E. Ciriotti

«Things are interesting only in so far as they relate themselves to other things»

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