Mineraller ve √∂zellikleri Biotit 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 % K 2 O Magnesium 14.02 % Mg 23.24 % MgO Aluminum 6.22 % Al 11.76 % Al 2 O 3 Iron 6.44 % Fe 8.29 % FeO Silicon 19.44 % Si 41.58 % SiO 2 Hydrogen 0.41 % H 3.64 % H 2 O Oxygen 43.36 % O Fluorine 1.10 % F 1.10 % F - % F -0.46 % -O=F 2 ______ ______ 100.00 % 100.00 % = TOTAL OXIDE Empirical Formula: KMg 2.5Fe 2+ 0.5AlSi 3O10(OH) 1.75F 0.25 Environment: Granitic rocks. Forms a series with phlogopite. Has several polytypes (1M, 3T, 2M1) Name Origin: Named after the French physicist, Jean Baptiste Biot (1774 - 1862), who studied the optical properties of the micas. Synonym: Iron Mica Lepidomelane (Fe) Manganophyllite (Mn) Micaceous Iron Ore Biotite Crystallography Axial Ratios: a:b:c =0.5771:1:1.1046 Cell Dimensions: a = 5.343, b = 9.258, c = 10.227, Z = 2; beta = 100.26¬į V = 497.79 Den(Calc)= 2.89 Crystal System: Monoclinic - PrismaticH-M Symbol (2/m) Space Group: C 2/m X Ray Diffraction: By Intensity(I/I o): 3.37(1), 10.1(1), 2.66(0.8), Forms: [ 1 1 2] [ 2 2 1] [ 0 1 0] [ 0 0 1] Physical Properties of Biotite Cleavage: [001] Perfect Color: Dark brown, Greenish brown, Blackish brown, Yellow, White. Density: 2.8 - 3.4, Average = 3.09 Diaphaniety: Transparent to translucent to opaque Fracture: Uneven - Flat surfaces (not cleavage) fractured in an uneven pattern. Habits: Micaceous - Platy texture with "flexible" plates., Lamellar - Thin laminae producing a lamellar structure., Pseudo Hexagonal - Crystals show a hexagonal outline. Hardness: 2.5-3 - Finger Nail-Calcite Luminescence: None. Luster: Vitreous - Pearly Streak: gray Optical Properties of Biotite Optical Data: Biaxial (-), a=1.565-1.625, b=1.605-1.675, g=1.605- 1.675, bire=0.0400-0.0500, 2V(Calc)=0, 2V(Meas)=0-25. Dispersion r > v or r < v.