Clinocervantite, ß-Sb2O4, the natural monoclinic polymorph of cervantite from the Cetine mine, Siena, Italy (original) (raw)

Original paper

Basso, Riccardo; Lucchetti, Gabriella; Zefiro, Liviο; Palenzona, Andrea

Abstract

Abstract Clinocervantite occurs at the Cetine di Cotorniano mine associated with valentinite, tripuhyite, bindheimite and rosiaite. Clinocervantite, appearing generally as aggregates of single prisms elongated along [001] or twinned on {100}, is colourless, transparent, with vitreous lustre, biaxial, with the lowest measured refractive index α´ = 1.72 and the highest one γ = 2.10. The strongest lines in the powder pattern are d111 = 3.244 Å and d311̄ = 2.877 Å. The crystal structure, space group C2/c with a = 12.061(1) Å, b = 4.836(1) Å, c = 5.383(1) Å, ß = 104.60(4)° and Z = 4, has been refined to R = 0.020, confirming the new mineral to be the natural analogue of the synthetic ß-Sb2O4 already known. The structures of clinocervantite and cervantite may be regarded as built up by stacking layers of nearly identical structure and composition accounting for both polytypism in the Sb2O4 compound and twinning of the clinocervantite crystals

Keywords

clinocervantite • crystal-structure refinement • cervantite • twinning