First occurrence of britholite-(Ce) in Italy (Monte Somma, Vesuvius)
Orlandi, Paolo; Perchiazzi, Natale; Mannucci, Gregorio
European Journal of Mineralogy Volume 1 Number 5 (1989), p. 723 - 725
published: Nov 16, 1989
manuscript accepted: Sep 8, 1989
manuscript received: Feb 22, 1989
ArtNo. ESP147050105013, Price: 29.00 €
Abstract The first occurrence of britholite-(Ce) in Italy consists of small (0.2 mm) transparent pale blue hexagonal tabular crystals in volcanic ejecta, mainly composed of sanidine, from Monte Somma, Vesuvius. The mineral is hexagonal, space group P63/m (or P63) a = 9.597(9), c = 7.04(1) Å. The anhydrous crystal-chemical formula, derived from electron microprobe analysis, is : Ca4(REE3.1Ca1.54Th1.23U0.08)5.95(Si5.42P0.94)6.36)O26 with REE = Ce1.77, La0.70, Nd0.47, Pr0.16' BrithoIite-(Ce) from Monte Somma has a high calcium content and the highest thorium content so far reported for this mineral. It is uniaxial negative, with nω> = 1.772(2).