Abstract
A monoclinic IIb-2 clinochlore from the Achmatov mine, Ural Mountains, U.S.S.R., was investigated by neutron diffraction. The formula, based on electron microprobe and wet chemical analyses, is (Mg4.54Al0.97Fe2+0.28 Fe3+0.18Mn0.01)(Si2.85Al1.15)O10(OH)8. A refinement based on 512 unique reflections converged in space group C2/m to a final R =.066. Cation disorder was found in the two octahedral positions of the 2:1 layer, whereas partial Mg and Al ordering occurs in the interlayer sheet. The two hydroxyl dipoles are roughly perpendicular to the interlayer sheet, forming weak to medium hydrogen bonds with O…O distances of 2.859 and 2.881 Å. The OH-dipole of the 2:1 layer is perpendicular to the (001) plane.
Zusammenfassung
Die Struktur eines monoklinen IIb-2 Klinochlors yon der Achmatov-Mine, Ural, UdSSR, wurde mit Neutronenbeugung untersucht. Mikrosondenanalyse und naßchemische Methoden ergaben die Zusammensetzung: (Mg4.54Al0.97Fe2+0.28Fe3+0.18Mn0.01)(Si2.85Al1.15)O10(OH)8. Die Verfeinerung mit 512 symmetrisch unabhängigen Reflexen konvergierte in Raumgruppe C2/m zu einem R = 0,066. Die Kationen der beiden oktaedrischen Positionen der 2:1-Schicht sind vollständig ungeordnet, während in der Zwischenschicht teilweise eine Ordnung von Mg und Al beobachtet wird. Die beiden Hydroxyl-Dipole stehen senkrecht auf der Zwischenschicht und bilden schwache bis mittelstarke Wasserstoffbrücken mit O…O-Abständen von 2,895 und 2,881 Å. Der OH-Dipol der 2:1-Schicht ist senkrecht zur 001-Fläche.
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Joswig, W., Fuess, H. & Mason, S.A. Neutron Diffraction Study of a One-Layer Monoclinic Chlorite. Clays Clay Miner. 37, 511–514 (1989). https://doi.org/10.1346/CCMN.1989.0370602
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DOI: https://doi.org/10.1346/CCMN.1989.0370602