CEE 437 Lecture 2 Minerals Thomas Doe. Topics Mineral Definition Rock Forming Minerals Physical...
-
date post
20-Dec-2015 -
Category
Documents
-
view
241 -
download
5
Transcript of CEE 437 Lecture 2 Minerals Thomas Doe. Topics Mineral Definition Rock Forming Minerals Physical...
CEE 437 Lecture 2Minerals
Thomas Doe
Topics
• Mineral Definition
• Rock Forming Minerals
• Physical Proprieties of Minerals
• Mineral Identification
• Mineral Lab
Mineral Definition
• Naturally occurring material with unique combination of chemical composition and crystalline structure
• Natural non-minerals — glasses, coal, amorphous silica
• Pseudomorphs: diamond:graphite
Galena, PbS Graphite, C
Crystalline Symmetry Groups
Crystal Forms, Cubic System
Crustal Composition
Differentiation of Crustal Composition
Weathering differentiating towards higher Silica
Preferential melting of higher silica
Concentration of C, Ca, Na, K in sea and air
Original basaltic composition of crust
Carbonate concentrated by organic processes
Mineral Differentiation
• Plate tectonics– selective melting, selective recrytallization– differentiation by density
• Weathering and erosion
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
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
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
Forms of Silicates
Crystalline Structure of Calcite
Physical Properties
• Density (Gravity)
• Electrical Conductivity (Resisitivity)
• Thermal Expansion
• Strength
• Elasticity (Mechanical properties, – Seismic/Acoustic Velocity
• Rheology (Plasticity,Viscosity)
Deformation Mechanisms
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
Clay Viewed from Electron Microscope
Mineral Identification
• Density
• Hardness
• Color, luster (metallic, non-metalic, semi-metallic)
• Crystalline habit
• Cleavage
• Mineral chemistry, x-ray diffraction
Hardness Scale
X-Ray Diffraction
spacing lattice,angle incidence,wavelength,sin2
dd
Bragg’s Law