Mineraller ve √∂zellikleri Ortoklas General Orthoclase Information Chemical Formula: KAlSi3O8 Composition: Molecular Weight = 278.33 gm Potassium 14.05 % K 16.92 % K 2 O Aluminum 9.69 % Al 18.32 % Al 2 O 3 Silicon 30.27 % Si 64.76 % SiO 2 Oxygen 45.99 % O ______ ______ 100.00 % 100.00 % = TOTAL OXIDE Empirical Formula: KAlSi 3O 8 Environment: Intrusive and extrusive igneous, and metamorphic rocks. Name Origin: From the Greek orthos - "right" and kalo -" I cleave" in allusion to the mineral's right angle of good cleavage. Synonym: Adularia Orthose Orthoclase Crystallography Axial Ratios: a:b:c =0.6636:1:0.5534 Cell Dimensions: a = 8.625, b = 12.996, c = 7.193, Z = 4; beta = 116.016¬į V = 724.57 Den(Calc)= 2.55 Crystal System: Monoclinic - PrismaticH-M Symbol (2/m) Space Group: C 2/m X Ray Diffraction: By Intensity(I/I o): 3.18(1), 4.02(0.9), 3.8(0.8), Forms: Forms: [ 1 1 0] [ 1 0 1] [ 0 0 1] [ 0 1 0] Physical Properties of Orthoclase Cleavage: [001] Perfect, [010] Good Color: Colorless, Greenish, Grayish yellow, White, Pink. Density: 2.56 Diaphaniety: Transparent to translucent Fracture: Uneven - Flat surfaces (not cleavage) fractured in an uneven pattern. Habits: Prismatic - Crystals Shaped like Slender Prisms (e.g. tourmaline)., Massive - Granular - Common texture observed in granite and other igneous rock., Blocky - Crystal shape tends to be equant (e.g. feldspars). Hardness: 6 - Orthoclase Luminescence: None. Luster: Vitreous (Glassy) Streak: white Optical Data: Biaxial (-), a=1.518, b=1.522, g=1.523-1.524, bire=0.0050-0.0060, 2V(Calc)=52-70, 2V(Meas)=65- 75. Dispersion relatively strong.