Osumilite, (K,Na)(Fe+2,Mg)2(Al,Fe+3)3(Si,Al)12O30, with Tridymite. 4 cm
Monte Arci, Marrubiu, Oristano, Sardegna, Italy
Coll. Pierre Perroud (now in NHM Geneva), from Salvatore Scanu, Cagliari, 1985
Photo Philippe Wagneur, MHN Genève. © Athena 2016