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Unveiling Earth's Minerals: Composition, Properties, and Formation

Explore the definition, physical properties, identification methods, and differentiation of minerals in the Earth's crust. Learn about rock-forming minerals, their crystalline structures, and elemental fates, along with the role of plate tectonics and weathering processes. Understand the major silicate groups, their forms, and the impact of mineral composition on physical properties and deformation mechanisms. Delve into mineral identification techniques such as density, hardness, color, and X-ray diffraction.

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Unveiling Earth's Minerals: Composition, Properties, and Formation

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  1. CEE 437 Lecture 2Minerals Thomas Doe

  2. Topics • Mineral Definition • Rock Forming Minerals • Physical Proprieties of Minerals • Mineral Identification • Mineral Lab

  3. Mineral Definition • Naturally occurring material with unique combination of chemical composition and crystalline structure • Natural non-minerals — glasses, coal, amorphous silica • Pseudomorphs: diamond:graphite

  4. Graphite, C Galena, PbS

  5. Crystalline Symmetry Groups

  6. Crystal Forms, Cubic System

  7. Crustal Composition

  8. Differentiation of Crustal Composition Weathering differentiating towards higher Silica Carbonate concentrated by organic processes Preferential melting of higher silica Original basaltic composition of crust Concentration of C, Ca, Na, K in sea and air

  9. Mineral Differentiation • Plate tectonics • selective melting, selective recrytallization • differentiation by density • Weathering and erosion

  10. Elemental Fates • Silicon tends to concentrate in crust — quartz is very long lived • Aluminum — transforms from feldspars to clays • Mica — transform to clays • Fe-Mg-Ca-Na-K concentrate in some clays and micas, concentrate in oceans in biosphere

  11. Rock Forming Minerals • Composition of Crust • Dominantly O, Si, Fe, Mg, Ca, Na, K • Near surface importance of bio-processes • Silicates from inorganic processes • Carbonates mainly from shell-forming organisms

  12. Major Silicate Groups • Silicon Tetrahedron • separate tetraheadra — olivine • single chains — pyroxene • double chains — amphibole • sheet silicates — micas and clays • framework silicates — feldspars (with Al substitution), quartz as pure silica

  13. Forms of Silicates

  14. Crystalline Structure of Calcite

  15. Physical Properties • Density (Gravity) • Electrical Conductivity (Resisitivity) • Thermal Expansion • Strength • Elasticity (Mechanical properties, • Seismic/Acoustic Velocity • Rheology (Plasticity,Viscosity)

  16. Deformation Mechanisms

  17. Effects on Physical Properties • Anisotropy • Properties differ by direction • Heterogeneity • Properties vary by location • Mineral properties may have strong anisotropy when crystals are aligned • Heterogeneity may have strong mechanical effects when different minerals have different deformation properties

  18. Clay Viewed from Electron Microscope

  19. Mineral Identification • Density • Hardness • Color, luster (metallic, non-metalic, semi-metallic) • Crystalline habit • Cleavage • Mineral chemistry, x-ray diffraction

  20. Hardness Scale

  21. X-Ray Diffraction Bragg’s Law

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