Original paper

Crystal chemical and structural characterization of an Mg-rich osumilite from Vesuvius volcano (Italy)

Balassone, Giuseppina; Mormone, Angela; Rossi, Manuela; Bernardi, Alessandro; Fisch, Martin; Armbruster, Thomas; Malsy, Anna; Kathrin Berger, Alfons

Abstract

At Vesuvius, osumilite, (K, Na)(Fe, Mg)2(Al, Fe, Mg)3(Si, Al)12O30, has been found for the first time in rare contact-metamorphosed rocks ejected during the 1872 A.D. eruption, one of the most violent eruptions of the 19th century. Chemical analysis shows that osumilite is homogeneous and characterized by high Mg numbers (between 88 and 90). Fe shows an average value of 0.247 apfu and K is always greater than 0.810 apfu, with an average value of 0.872 apfu. Structure refinement is consistent with space group P6/mcc.

Keywords

osumilitevesuviusdouble-ring silicatescrystal chemistrycrystal structure