Biotite Mineral Data

General Biotite Information
Chemical Formula:	K(Mg,Fe++)3[AlSi3O10(OH,F)2
Composition:	Molecular Weight = 433.53 gm
	Potassium 9.02 % K 10.86 % K₂O
	Magnesium 14.02 % Mg 23.24 % MgO
	Aluminum 6.22 % Al 11.76 % Al₂O₃
	Iron 6.44 % Fe 8.29 % FeO
	Silicon 19.44 % Si 41.58 % SiO₂
	Hydrogen 0.41 % H 3.64 % H₂O
	Oxygen 43.36 % O
	Fluorine 1.10 % F 1.10 % F
	- % F -0.46 % -O=F₂
	______ ______
	100.00 % 100.00 % = TOTAL OXIDE
Empirical Formula:	KMg_2.5Fe²⁺_0.5AlSi₃O₁₀(OH)_1.75F_0.25
Environment:	Granitic rocks. Forms a series with phlogopite. Has several polytypes (1M, 3T, 2M1). Biotite is now a group name for phlogopite, siderophyllite and eastonite.
IMA Status:	Not Approved IMA 1998 - Bitote is now the group name
Locality:	Common world wide. Link to MinDat.org Location Data.
Name Origin:	Named in 1847 after the French physicist, Jean Baptiste Biot (1774 - 1862), who studied the optical properties of the micas.
Name Pronunciation:	Biotite
Synonym:	Iron Mica
	Lepidomelane (Fe)
	Manganophyllite (Mn)
	Micaceous Iron Ore
	Oxybiotite