Ferro-ferri-hornblende is an amphibole-supergroup mineral with the formula ☐Ca2(Fe2+4Fe3+)(Si7Al)O22(OH)2. It contains essential vacancy (☐). It was discovered in the Traversella mine, Canavese, Torino, Piedmont, Italy.Oberti, R., Boiocchi, M., Hawthorne, F.C., Ball, N.A., Pagano, R., and Pagano, A., 2015. Ferro-ferri-hornblende, IMA 2015-054. CNMNC Newsletter No. 27, October 2015, 1227; Mineralogical Magazine 79, 1229–1236
References