Polytypism in hanjiangite, sheet silicate-carbonate-fluoride of calcium, aluminium, vanadium and barium

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Marco E. Ciriotti
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Polytypism in hanjiangite, sheet silicate-carbonate-fluoride of calcium, aluminium, vanadium and barium

Messaggio da Marco E. Ciriotti » lun 25 dic, 2017 11:03

Referenza:
▪ Merlino, S. (2014): Polytypism in Hanjiangite, sheet silicate-carbonate-fluoride of calcium, aluminium, vanadium and barium. Atti della Società Toscana di Scienze Naturali, Memorie, Serie A, 121, 71-77.

Abstract:
The crystal structure of hanjiangite, sheet silicate-carbonate-fluoride of calcium, aluminium, vanadium and barium is described and its polytypic character is indicated. It is shown that hanjiagite is built up by two distinct structural layers (building layers BL1 and BL2) which alternate along the direction normal to the layers. The analysis of the possible sequences shows that there are three main polytypes: one, hanjiangite-2M, corresponding to the structure of the phase found in nature and studied by Liu et al. (2012), in which two layers of each type alternate for two times in a monoclinic cell; the two other polytypes, hanjiangite-1M and hanjiangite-3T, present a single alternation of BL1 and BL2 layers in a monoclinic cell (hanjiangite-1M) and a triple alternation of BL1 and BL2 in a trigonal cell (hanjiangite-3T). The close metrical and compositional relationships of hanjiangite-1M with a pair of other complex layered minerals are discussed.
Marco E. Ciriotti

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

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