Ferro-ferri-hornblende

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.^[2]

Ferro-ferri-hornblende
General
Category	Inosilicate Amphibole supergroup
Formula	☐Ca2(Fe2+4Fe3+)(Si7Al)O22(OH)2
IMA symbol	Ffhbl[1]
Crystal system	Monoclinic
Crystal class	Prismatic (2/m) (same H-M symbol)
Space group	C2/m
Unit cell	a = 9.93, b = 18.22 c = 5.32 [Å], β = 104.86° (approximated)
Identification
References	[2][3]