It is common for Mg or Fe2+ to substitute for Al on the Y site and a corresponding increase in Si on the Z site in the mica group formula X2Y4–6Z8O20(OH, F)4.

Similar to muscovite but with addition of magnesium.

It is a non-IMA recognized mineral name representing the series between muscovite and celadonite.

[1][2] The silica content of phengite has been proposed as a geobarometer for the metamorphism of low grade schists.

This article about a specific silicate mineral is a stub.