Titre du document / Document title

Alacranite, As⁸S⁹: structural study of the holotype and re-assignment of the original chemical formula

Auteur(s) / Author(s)

BONAZZI Paola ; BINDI Luca ; POPOVA Valentina ; PRATESI Giovanni ; MENCHETTI Silvio ;

Résumé / Abstract

Alacranite from the type locality (Uzon caldera, Kamchatka, Russian Federation) was submitted for structural analysis. A single crystal was selected and the following lattice parameters were determined: a = 9.942(4), b =9.601(2), c = 9.178(3) Å, β = 101.94(3)°, V = 857.1 (5) Å₃ The crystal structure was solved in the P2/c space group using direct methods and refined to R = 6.79% for 472 observed reflections. The structure of alacranite consists of an ordered sequence of As⁴S⁴ and As⁴S⁵ cage-like molecules, with a molecular packing closely resembling that found in the β-As⁴S⁴phase. Both As-As and As-S intramolecular distances are in the range usually observed for covalent bonds. The structural model confirms the chemical formula As⁸S⁹ for alacranite, and accounts for differences in the unit-cell parameters of alacranite compared to those of the natural analogue of β-As⁴S⁴. This latter mineral, therefore, should receive a new name.

Revue / Journal Title

The American mineralogist   ISSN 0003-004X   CODEN AMMIAY 

Source / Source

2003, vol. 88 (1), n^o11-12, pp. 1796-1800 [5 page(s) (article)]

Langue / Language

Anglais

Editeur / Publisher

Mineralogical Society of America, Washington, DC, ETATS-UNIS  (1916) (Revue)

Localisation / Location

INIST-CNRS, Cote INIST : 503, 35400011883510.0200