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Composite twins of lM mica: derivation and identification.

Abstract : 1"M is the simplest and one of the most common mica polytypes. Because of the special cell dimensions, twinning by reticular pseudo-merohedry is frequently observed. The possible orientations of the individuals in the twin are approximately the same as the possible orientations of layers in polytypes. Because of the presence of a pseudo-hexagonal twin lattice, five pairs of twin laws are possible and they give rise to five pairs of corresponding twins. Thirty-one composite twins can be enumerated, which however give rise to ten different diffraction patterns. In the twin lattice there are nine geometrically independent rows parallel to c*, defining a minimal rhombus in reciprocal space, which allows us to identify the ten independent patterns. A larger unit of translation, called tessellation rhombus, can be built on it; by tessellation of this unit all the reciprocal space can be covered.
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Contributor : Massimo Nespolo <>
Submitted on : Thursday, February 22, 2018 - 5:58:30 PM
Last modification on : Monday, May 17, 2021 - 12:00:05 PM
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Massimo Nespolo, Hiroshi Takeda, Giovanni Ferraris, Toshihiro Kogure. Composite twins of lM mica: derivation and identification.. Mineralogical Journal, 1997, 19 (4), pp.173 - 186. ⟨10.2465/minerj.19.173⟩. ⟨hal-01715531⟩



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