Jouravskite: refined data on the crystal structure, chemical composition and spectroscopic properties

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Marco E. Ciriotti
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Jouravskite: refined data on the crystal structure, chemical composition and spectroscopic properties

Messaggio da Marco E. Ciriotti » gio 15 nov, 2018 11:41

Prossima pubblicazione.

Referenza:
▪ Chukanov, N.V., Zubkova, N.V., Pautov, L.A., Göttlicher, J., Kasatkin, A.V., Van, K.V., Ksenofontov, D.A., Pekov, I.V., Vozchikova, S.A., Pushcharovsky, D.Yu. (2018): Jouravskite: refined data on the crystal structure, chemical composition and spectroscopic properties. Physics and Chemistry of Minerals, 45, (in press).

Abstract:
Refined data on the crystal structure, chemical composition and properties of jouravskite, ideally Ca3Mn4+(SO4)(CO3)(OH)6·12H2O, have been obtained on a sample from N’Chwaning 3 Mine, Kuruman, Kalahari manganese field, Northern Cape Province, South Africa. The chemical composition determined using a combination of different methods (including ICP-OES, gas chromatography of products of ignition and electron microprobe) is (wt%): CaO 25.88, SrO 0.19, BaO 0.23, B2O3 0.39, Fe2O3 1.01, MnO2 12.00, SiO2 0.06, CO2 6.8, SO3 12.44, H2O 41.8, total 100.80, which corresponds to the empirical formula (Z = 2): (Са2.98Sr0.01Ba0.01)Σ3.00(Mn4+0.89Fe3+0.08Si0.01)Σ0.98{(SO4)1.00(CO3)1.00[B(OH)4]0.07}Σ2.07(OH)5.78·11.94H2O. Tetravalent state of Mn was confirmed by Mn K-edge XANES spectroscopy. The IR spectrum of jouravskite contains characteristic bands of Mn4+(OH)6 octahedra, CO32− and SO42− anions, and H2O molecules. The crystal structure was determined using single-crystal X-ray diffraction data and refined to R = 0.0332. Jouravskite is isostructural with thaumasite. The parameters of the hexagonal (space group P63) unit cell are: a = 11.07129(14) Å, c = 10.62650(14) Å, V = 1128.02(3) Å3 and Z = 3. Investigation of other samples of ettringite-group minerals from N’Chwaning 3 Mine demonstrates wide variations of the contents of manganese, iron and boron, and possible existence of a Mn4+-dominant analogue of sturmanite with the presumed idealized formula Са6Mn4+2(SO4)2[B(OH)4](OH)10O2·nH2O
Marco E. Ciriotti

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