Abstract:
Phengite, K(Mg,Fe)0.5Al1.5[Si3.5Al0.5O10](OH)2, is a dioctahedral mica intermediate between muscovite and aluminoceladonite in the nomenclature. Divalent cations, mainly Mg2+ and Fe2+, substitute for Al in the octahedral sites of phengite. Since the total number of octahedral cations in the mineral remains two per formula unit, the content of tetrahedrally coordinated aluminum also decreases.
