Ferro-ferri-hornblende is an amphibole-supergroup mineral with the formula âÂÂCa<sub>2</sub>(Fe<sup>2+</sup><sub>4</sub>Fe<sup>3+</sup>)(Si<sub>7</sub>Al)O<sub>22</sub>(OH)<sub>2</sub>. It contains essential vacancy (âÂÂ). It was discovered in the Traversella mine, Canavese, Torino, Piedmont, Italy.