A survey of hybrid twins in silicate minerals

作者：Pignatelli Isabella; Nespolo Massimo^*; Ferraris Giovanni

来源：European Journal of Mineralogy, 2011, 23(5): 779-794.

DOI：10.1127/0935-1221/2011/0023-2142

• twinning
• hybrid twinning
• reticular merohedry
• reticular polyholohedry
• effective twin index
• concurrent (quasi)-restored sublattices

This article is the second part of the survey presenting a systematic crystallographic analysis of hybrid twins in minerals. Here we deal with silicate minerals and in particular the hybrid twins of allanite, augite, axinite, beryl, chloritoid, clinoenstatite, clinozoisite, cordierite, cummingtonite-grunerite, diopside-hedenbergite, enstatite-ferrosilite, epidote, forsterite-fayalite, johannsenite, natrolite, piemontite, pigeonite, protoenstatite, pumpellyite, pyroxmangite, quartz, titanite, spodumene, staurolite, topaz, tourmaline, tremolite-actinolite-ferroactinolite, tridymite. The comparison with the twin analysis of non-silicate minerals shows that the number of hybrid twins for non-silicates is higher than that of the silicates. This well agrees with the fact that the twin formation is favoured by the high symmetries of the close-packing topologies, typical of many non-silicates, especially oxides and simple sulphides, whereas the silicate structures are more complex and characterized by different degrees of polymerization of Si-O tetrahedra.

• 出版日期2011-10