Feldspar Minerals

1 Crystal Structures.- 1 Introduction.- 1.1 Crystallographic Background.- 1.2 Crystal Structure of Feldspar.- 1.3 Background on Phase Equilibria.- 1.4 Phase Equilibria of Feldspars.- 1.4.1 Alkali Feldspars.- 1.4.2 Plagioclase Feldspars.- 1.4.3 Phase Relations for Natural Feldspars.- 1.4.4 Nomenclature.- 2 Crystal Structure of Feldspar. Principal Features. Related Structures.- 2.1 The Topology of the Aluminosilicate Framework.- 2.2 General Features of Feldspar Structures.- 2.3 Pseudo-Close-Packing of Atoms: Pseudosymmetry.- 2.4 Structures of Related Minerals.- 2.4.1 Minerals Based on 4.8.8 Net.- 2.4.2 Hollandite Structure Type.- 2.4.3 The Hexagonal Structures.- 2.4.4 Pseudo-Orthorhombic CaAl2Si2O8.- 3 Order - Disorder.- 3.1 Mathematical and Crystallographic Bases of Ordering.- 3.2 Experimental Techniques for Determination of Si,Al Order in Feldspars.- 3.3 Mathematical Descriptions of Si,Al Order in Feldspars.- 3.3.1 Algebraic Description of Site Populations and Atomic Order.- 3.3.2 Topochemistry of Ordered Phases.- 3.4 Si,Al Ordering in AlSi3 and Related Feldspars.- 3.5 Si,Al Ordering in Al-Rich Feldspars.- 3.6 Crystal-Chemical Explanation of Ordering.- 3.6.1 Alternation in Al2Si2 Feldspar.- 3.6.2 Choice of T1 Site in AlSi3 Feldspar.- 3.6.3 Limitation of Al:Si Ratio Between 1:3 and 2:2.- 4 Detailed Geometry and Atomic Coordination.- 4.1 General Features.- 4.2 Geometry of the Framework.- 4.2.1 T-O Distances and O-T-O Angles.- 4.2.2 T-O-T Angles.- 4.3 Environment of M Atoms.- 4.4 Atomic Displacements from Thermal Motion and Substitutional Disorder.- 4.5 Temperature Variation of Atomic Positions and Displacements.- 5 Complex Crystal Structures.- 5.1 Summary of Theoretical Concepts.- 5.2 Crystal Structures and Domain Textures in Anorthite (100 to ~90% An).- 5.3 e-Plagioclase.- 5.4 Structural Aspects of Heating. Experiments on Plagioclase.- 2 Physical Properties and Experimental Techniques.- 6 X-Ray and Neutron Diffraction Techniques.- 6.1 Single-Crystal Diffraction Techniques.- 6.1.1 General.- 6.1.2 Alkali Feldspars.- 6.1.3 Plagioclase.- 6.2 Powder Techniques.- 6.2.1 General.- 6.2.2 Alkali Feldspars and Celsian.- 6.2.3 Plagioclase and Reedmergnerite.- 7 Cell Parameters and Macroscopic Thermal Expansion and Compression.- 7.1 General.- 7.2 End-Member Feldspars and General Interpretation.- 7.3 Alkali Feldspars.- 7.3.1 General and Historical.- 7.3.2 Homogeneous Alkali Feldspars.- 7.3.3 Perthites and Coherency Stress and Strain.- 7.3.4 Determinative Methods.- 7.3.5 Thermal Expansion, Compression and Phase Transformations.- 7.4 Plagioclase Feldspars.- 7.4.1 General.- 7.4.2 Cell Parameters of Natural and Synthetic Plagioclases.- 7.4.3 Interpretation in Terms of Crystal Structure.- 7.4.4 Simple Determinative Methods.- 7.4.5 Dimensional Changes Caused by Heating.- 7.5 Ternary Feldspars and K-Exchanged Plagioclase.- 7.5.1 General.- 7.5.2 K-Exchanged Plagioclase.- 7.5.3 Ternary Feldspars.- 7.6 Ba,K,Na Feldspars.- 7.7 Synthetic Analogs.- 7.7.1 Substitutions in M-Sites.- 7.7.2 Substitutions in T-Sites.- 8 Light Optics.- 8.1 Techniques and Precision.- 8.2 Alkali Feldspars.- 8.2.1 Introduction.- 8.2.2 Albite.- 8.2.3 Potassium Feldspar.- 8.2.4 Alkali Feldspars.- 8.2.5 The Effect of Dry Heating on the Optics of Alkali Feldspars.- 8.3 Plagioclase.- 8.3.1 Introduction.- 8.3.2 Optic Axial Angle.- 8.3.3 Refractive Indices.- 8.3.4 Optical Orientation and Extinction Angles.- 8.4 K,Ba and Other Feldspars.- 8.5 Determinative Methods.- 8.5.1 Alkali Feldspars.- 8.5.2 Plagioclase.- 9 Nomenclature, General Properties of Feldspars and Simple Determinative Diagrams.- 9.1 General.- 9.2 A Simple Chemical and Optical Classification of Feldspars.- 9.2.1 Nomenclature for Homogeneous High-Temperature Disordered Feldspars.- 9.2.2 Nomenclature for Partly to Fully Ordered Feldspars.- 9.2.3 Compositional Restrictions in Different Geological Environments.- 9.2.4 Procedure for Naming a Feldspar.- 9.3 Alkali Feldspars.- 9.3.1 Orthoclase and Or-Rich Feldspars.- 9.3.2 A Simple Determinative Diagram for Or-Rich Feldspars.- 9.3.3 The Stability of Intermediate Microcline.- 9.3.4 Polymorphism of Albite.- 9.3.5 Phase Transformations in the Ab-Or System.- 9.4 Plagioclase Feldspars.- 9.5 Other Feldspars.- 10 Electron-Optical Techniques.- 10.1 General.- 10.2 Transmission Electron Microscopy.- 10.2.1 Experimental Details.- 10.2.2 Dislocations, Deformation, Twinning.- 10.2.3 Translational Variants-Antiphase Domains.- 10.2.4 Compositional Variants - Exsolution and Modulated Structures.- 10.2.5 Inclusions and Alteration.- 10.3 Scanning Electron Microscopy.- 10.4 Photoemission Electron Microscopy.- 11 Spectroscopy - IR, Raman, NMR, NQR, EPR, NGR (Mössbauer), XAS, EXAFS, ESCA, XPS.- 11.1 General.- 11.2 Infrared and Raman Spectroscopy.- 11.2.1 K-Feldspars.- 11.2.2 Albite and Alkali Feldspars.- 11.2.3 Plagioclase and MAl2Si2O8 Species.- 11.2.4 Glasses.- 11.2.5 Assignment of IR and Raman Bands.- 11.2.6 Water in Feldspars.- 11.2.7 Iron in Feldspars.- 11.3 Nuclear Magnetic and Electrical Quadrupole Resonance.- 11.3.1 Alkali Feldspars.- 11.3.2 Plagioclase Feldspars.- 11.3.3 Crystal-Chemical Interpretations.- 11.4 Electron Paramagnetic Resonance.- 11.4.1 Fe3+ in Alkali Feldspar.- 11.4.2 Paramagnetic Species in Plagioclase.- 11.4.3 Radiation Defects.- 11.5 Mössbauer (Gamma-Ray) Resonance.- 11.5.1 Alkali Feldspar.- 11.5.2 Plagioclase.- 11.6 Techniques Using X-Rays.- 12 Miscellaneous Physical Properties.- 12.1 Color.- 12.1.1 Yellow Feldspars.- 12.1.2 Blue and Green Feldspars; Amazonite.- 12.1.3 Smoky Feldspar.- 12.1.4 Colored Feldspars with Inclusions.- 12.2 Luminescence.- 12.2.1 Electron- and Proton-Excited Luminescence.- 12.2.2 Thermoluminescence.- 12.3 Electrical Phenomena.- 12.3.1 Electrical Conductivity.- 12.3.2 Dielectric Phenomena.- 12.4 Thermal Conductivity.- 12.5 Mechanical Properites.- 12.5.1 Elastic Deformation, Photoelasticity, Grinding Hardness, Surface Energy, Cleavage.- 12.5.2 Controlled Uniaxial Deformation and Natural Phenomena.- 12.5.3 Shock Deformation.- 12.6 Density.- 12.7 Thermogravimetry and Differential Thermal Analysis.- 12.8 Separation and Visual Identification Procedures.- 12.8.1 Separation of Feldspars.- 12.8.2 Rapid Visual Identification.- 3 Chemical Properties and Experimental Techniques.- 13 Analytical Techniques: Their Precision and Accuracy.- 13.1 Introduction.- 13.2 Techniques: Specific Applications to Feldspars.- 13.2.1 Gravimetric and Volumetric Analysis: Colorimetric Methods.- 13.2.2 Microprobe Techniques Using Excitation by Particles and Photons.- 13.2.3 Optical Spectrography.- 13.2.4 Radio-Activation Analysis.- 13.2.5 Mass Spectrometer Analysis.- 14 Chemical Properties.- 14.1 General.- 14.1.1 Brief History.- 14.1.2 Basic Stoichiometry: Deviations Therefrom.- 14.1.3 Theoretical Models on Chemical Substitution and Distribution.- 14.2 Major Chemical Substitutions.- 14.3 Experimental Data on Element Distribution.- 14.3.1 Sr, Ba, Ca, Y, Eu2+, Eu3+, and Other Rare Earths Between Plagiociase and Magmatic Liquid.- 14.3.2 Fe and Mg Between Plagiociase and Basaltic Liquid.- 14.3.3 Alkalis and Alkaline-Earths Between Alkali Feldspar Crystals, Melt and Hydrous Halide Solution ("Brine").- 14.3.4 Rb, Cs, Sr and Ba Between Two Feldspars.- 14.3.5 Miscellaneous.- 14.4 Chemical Substitution in Natural Feldspars.- 14.4.1 Introduction.- 14.4.2 Substitution in T-Sites.- 14.4.3 Substitution of Other First-Series Transition Metals.- 14.4.4 Substitution of Li, Rb, Cs, Tl, NH4, Sr, Ba, Pb.- 14.4.5 Substitution of Other Elements.- 14.5 Isotope Distribution.- 14.5.1 Oxygen Isotopes.- 14.5.2 Lead Isotopes.- 14.5.3 K/Ar Isotopic Ratio.- 14.5.4 Other Isotopic Ratios.- 4 Diffusion, Growth, Twins and Intergrowths.- 15 General Review of Phenomena and Processes.- 15.1 General.- 15.2 Point and Line Defects.- 16 Diffusion in Feldspars, Liquids and Glasses. Viscosity.- 16.1 General.- 16.2 Self-Diffusion and Tracer Diffusion.- 16.2.1 M Atoms.- 16.2.2 Argon and Other Gases.- 16.2.3 Oxygen.- 16.2.4 Aluminum and Silicon.- 16.2.5 Summary and Diffusion Compensation.- 16.3 Interdiffusion.- 16.3.1 Alkali Feldspars.- 16.3.2 Plagioclase.- 16.4 Diffusivity and Viscosity in Liquid and Glass.- 16.4.1 Diffusion in Glasses and Melts of Feldspar Composition.- 16.4.2 Viscosity.- 16.4.3 The Glass Transition and the Structure of Glasses.- 17 Nucleation, Growth, Melting, Dissolution, Chemical Zoning and Morphology.- 17.1 Nucleation.- 17.1.1 General.- 17.1.2 Nucleation in Melts.- 17.2 Growth and Dissolution.- 17.2.1 General.- 17.2.2 Growth Rates From Melts.- 17.2.3 Growth Morphologies and Undercooling.- 17.2.4 Effect of Undercooling on the Chemical Composition.- 17.2.5 Melting and Dissolution.- 17.2.6 Melt and Fluid Inclusions.- 17.2.7 Comparison with Growth and Dissolution in Magmatic Rocks.- 17.2.8 Growth in the Solid State.- 17.3 Chemical Zoning.- 17.3.1 General.- 17.3.2 Experimentally Produced Zoning.- 17.3.3 Internal Morphology of Zoned Feldspars.- 17.3.4 Compositional Variation in Zoned Crystals.- 17.3.5 Theories of Zoning in Feldspars.- 17.4 Morphology.- 18 Twins.- 18.1 Twin Geometry and Twin Laws.- 18.1.1 General.- 18.1.2 Normal Twins.- 18.1.3 Parallel Twins.- 18.1.4 Edge-Normal Twins.- 18.2 Genesis of Twins.- 18.2.1 General.- 18.2.2. "Synneusis" Twinning.- 18.2.3 Transformation Twinning.- 18.2.4 Glide Twinning.- 18.3 Transformation Twinning in Alkali Feldspars.- 18.3.1 Anorthoclase.- 18.3.2 Orthoclase and Microcline.- 18.4 Twin Frequency and Glide Twinning.- 18.4.1 Twin Frequency.- 18.4.2 Glide Twins.- 19 Intimate Feldspar Intergrowths.- 19.1 General.- 19.1.1 Nature of the Intergrowths.- 19.1.2 Origin of the Intergrowths.- 19.1.3 Miscibility and Stability Relationships: Order-Independent (Unconditional) and Order-Dependent (Conditional) Miscibility Gaps.- 19.1.4 Exsolution Mechanisms.- 19.1.5 Orientation Relationships and Periodic Twinning.- 19.1.6 Maturation, Coarsening and Replacement.- 19.2 Order-Independent Intergrowths: Perthites and Antiperthites.- 19.2.1 General.- 19.2.2 Strain-Controlled Crypto- and Fine Microperthites.- 19.2.3 Microperthites, Fluid-Induced Coarsening and Deuteric Perthites.- 19.3 Order-Dependent Intergrowths in Plagioclase.- 19.3.1 General.- 19.3.2 The Peristerite Intergrowth in Acid Plagioclase.- 19.3.3 The Bøggild Intergrowth in Intermediate Plagioclase.- 19.3.4 The Huttenlocher Intergrowth in Basic Plagioclase.- 19.3.5 Coarse Intergrowths of Plagioclase in Metamorphic Rocks.- 19.4 Exsolution and Miscibility Gaps in Other Feldspars.- 19.4.1 Ba Feldspars.- 19.4.2 Synthetic Feldspars.- 20 Intergrowths of Feldspars with Other Minerals.- 20.1 Myrmekite.- 20.1.1 Simplified Description.- 20.1.2 Historical Review.- 20.1.3 Critique of Models for Myrmekite.- 20.1.4 Symplectite of Quartz and Calcic Plagioclase.- 20.2 Spherulites, Granophyre, and Graphic Granite.- 20.2.1 General Statement.- 20.2.2 Experimental Synthesis.- 20.2.3 Spherulites in Devitrified Rocks.- 20.2.4 Granophyric Intergrowths.- 20.2.5 Graphic Granite.- 20.3 Nepheline-Feldspar Intergrowths.- 20.3.1 Nepheline-Alkali-Feldspar Symplectite in Larvikite.- 20.3.2 Nepheline-Plagioclase Vermicular Intergrowths.- 20.3.3 Pseudoleucite.- 20.3.4 Anhedral Intergrowths of K-Feldspar with Nepheline and Kalsilite.- 20.4 Aventurine and Red-Clouded Feldspar.- 20.4.1 Nature of Aventurine and Sunstone.- 20.4.2 Nature of Red-Clouded Feldspars.- 20.4.3 Origin of Aventurine and Red-Clouded Feldspar.- 20.5 Clouded Feldspar.- 20.5.1 Early Observations and Ideas on Clouded Plagioclase.- 20.5.2 Later Observations on Clouded Plagioclase.- 20.5.3 Clouded Plagioclase in Anorthositic Rocks.- 20.5.4 Critique.- 20.6 Miscellaneous Associations with Other Minerals.- 20.6.1 Feldspar-Olivine.- 20.6.2 Feldspar-Pyroxene.- 20.6.3 Feldspar-Garnet.- 20.6.4 Feldspar-Spinel.- 20.6.5 Feldspar-Mica and Amphibole.- 20.6.6 Miscellaneous.- 20.6.7 Fingerprint Texture of Feldspar and Glass.- References.- Pre-1973.- Post-1973.- Name Index.- Geographical Index.