Twinning in chalcostibite revisited

database, nuove specie, discrediti,
ridefinizioni, classificazioni, ecc.
Avatar utente
Marco E. Ciriotti
Messaggi: 24699
Iscritto il: ven 25 giu, 2004 11:31
Località: via San Pietro, 55 I-10073 Devesi/Cirié TO - Italy

Twinning in chalcostibite revisited

Messaggio da Marco E. Ciriotti » sab 09 giu, 2018 14:57

▪ Nespolo, M. (2018): Twinning in chalcostibite revisited. European Journal of Mineralogy, 30, (in press).

Twinning in chalcostibite has been reported to occur on the (104) plane with respect to the standard setting Pnma of the space group. However, different axial settings have been used for this mineral, and in the literature an axial ratio which corresponds to the Pnam setting is often reported. Unfortunately, the same indexing of the twin plane, (104), is incorrectly used for both settings; this has led to an incorrect reticular analysis of the twin, which could have been an example of diperiodic twin, an alleged category which has no known examples to date. In this article, we trace back the origin of the inconsistent indexing, we present a revised reticular analysis which puts back this twin in the category of triperiodic twins, and we discuss the atomic structure at the composition plane, showing that a small adjustment of the metal-sulphur coordination is required to accommodate the change in orientation occurring when the twin forms.
Marco E. Ciriotti

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


Chi c’è in linea

Visitano il forum: Nessuno e 3 ospiti