Ferri-obertiite
A sodium-rich amphibole formally approved in 2015, with ferric iron and titanium in key sites.
Intro adapted from Wikipedia (CC BY-SA).
Ferri-obertiite is an IMA-recognized mineral species in the silicate class, with the chemical formula NaNa₂(Mg₃Fe³⁺Ti)Si₈O₂₂O₂.
It crystallizes in the monoclinic crystal system (space group C2/m). It is a member of the Amphibole structural group.
Key properties: specific gravity 3.145; Vitreous luster; optically biaxial.
IMA symbol Fob, IMA status: approved, named in 2015.
From vesicles in silicate veins within basaltic scoria.
It is found associated with Sanidine, α-quartz paramorphic after β-quartz, eifelite, tridymite, rutile, roedderite.
The name refers to an oxo-amphibole with Fe3+ dominant over Fe2+ in the C site.