Abstract
Talc specimens heated to 700–1450° C were examined with an analytical high-resolution transmission electron microscope. Neither the amphibole-like structure nor the MPP structure (M = mica, P = pyroxene-layer), proposed by Avgustinik and Vigdergauz (1948) and Sueno et al. (1980), was found. On the contrary, a disordered pyribole structure was observed. This pyribole showed a structure disordered in terms of chain widths, with single and double chains predominant. A local MPP structure with 4–6 repeated units of (21) sequence was generally observed in a disordered region. The electron diffraction data were consistent with maximum symmetry A2/m for the proto-MPP structure. A HRTEM study of the fine structures associated with the depolymerization of talc was the basis of a structural model proposed for the depolymerization of biopyriboles. In this model, a pair of (010) faults with a displacement of 1/2 (a+c) took an important role. The acceptor and donor regions model was also discussed.
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Konishi, H., Akai, J. Depolymerized pyribole structures derived from talc by heating. Phys Chem Minerals 17, 569–582 (1991). https://doi.org/10.1007/BF00203836
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DOI: https://doi.org/10.1007/BF00203836