Phlogopite

Phlogopite is a yellow, greenish, or reddish-brown member of the mica family of phyllosilicates. It is also known as magnesium mica.

Phlogopite is the magnesium endmember solid solution series, with the chemical formula KMg3AlSi3O10(F,OH)2. Iron substitutes for magnesium in variable amounts leading to the more common biotite with higher iron content. For physical and optical identification, it shares most of the characteristic properties of biotite.