Tags: Chemical Substance, Mineral.
Biotite is a common phyllosilicate mineral within the mica group with the approximate chemical formula K(MgFe)3AlSi3O10(FOH)2. More generally it refers to the dark mica series primarily a solid-solution series between the iron-endmember annite and the magnesium-endmember phlogopite; more aluminous endmembers include siderophyllite. Biotite was named by J.F.L.
