Ferro-ferri-hornblende
An amphibole with ferrous and ferric iron in two different structural sites, discovered at Italy's Traversella mine.
Intro adapted from Wikipedia (CC BY-SA).
Ferro-ferri-hornblende is an IMA-recognized mineral species in the silicate class, with the chemical formula Ca₂(Fe²⁺₄Fe³⁺)(Si₇Al)O₂₂(OH)₂.
It crystallizes in the monoclinic crystal system (space group C2/m). It is a member of the Amphibole structural group.
Key properties: Mohs hardness 6; specific gravity 3.362; Vitreous luster; optically biaxial.
IMA symbol Ffhbl, IMA status: approved, named in 2015.
Found in a contact metamorphic rock (skarn).
It is found associated with Tremolite, hastingsite, magnesio-hastingsite, quartz, calcite.
Signifies an amphibole in the compositional range of hornblende with essential Fe2+ > Fe3+ and in the C structural site.