Ferrogedrite
Ferrogedrite is an amphibole mineral with the complex chemical formula of ☐Fe2(Fe3Al2)(Si6Al2)O22(OH)2. It is sodium and calcium poor, making it part of the magnesium-iron-manganese-lithium amphibole subgroup. Defined as less than 1.00 apfu (atoms per formula unit) of Na + Ca and consisting of greater than 1.00 apfu of (Mg, Fe, Mn, Li) separating it from the calcic-sodic amphiboles. It is related to anthophyllite amphibole and gedrite through coupled substitution of (Al, Fe) for (Mg, Fe, Mn) and Al for Si. and determined by the content of silicon in the standard cell.