Phengite is a series name for dioctahedral micas of composition K AlMg 2 OH 2 SiAl 4O10 similar to muscovite but with addition of magnesium It is a non IMA
The mineral paragenesis of ltre blueschist facies in granitic orthogneiss is quartz albite microcline phengite biotite almandine rich garnet occurs in tona