Short brown prismatic crystals of the rare mineral ferroindialite from the famous Bellerberg (Bellerberg, Ettringen, Eifel Mountains, Rhineland-Palatinate, Germany). Ex. Erich Laskowski collection (USA). — Photo: David Hospital · CC BY 4.0
Ferroindialite
Ferroindialite is an IMA-recognized mineral species in the silicate class, with the chemical formula (Fe²⁺,Mg)₂Al₄Si₅O₁₈.
It crystallizes in the hexagonal crystal system (space group P6/mcc). It is a member of the Beryl structural group.
Key properties: Mohs hardness 7; specific gravity 2.66; White streak; Vitreous luster; optically biaxial.
IMA symbol Find, IMA status: approved, named in 2013.
Found in a metamorphosed pelitic xenolith in alkaline basalt.
It is found associated with Sillimanite, sanidine, phlogopite, enstatite-ferrosilite, wagnerite, fluorapatite, tridymite, zircon, high-Mg almandine.
As the iron-dominant (ferro) analog of indialite.