CEE 437 Lecture 2 Minerals

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CEE 437 Lecture 2Minerals

• Thomas Doe

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Topics

• Mineral Definition
• Rock Forming Minerals
• Physical Proprieties of Minerals
• Mineral Identification
• Mineral Lab

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Mineral Definition

• Naturally occurring material with unique
  combination of chemical composition and
  crystalline structure
• Natural non-minerals glasses, coal, amorphous
  silica
• Pseudomorphs diamondgraphite

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Graphite, C
Galena, PbS
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Crystalline Structure of Calcite
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Crystalline Symmetry Groups
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Crystal Forms, Cubic System
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Crustal Composition
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Bowens Reaction Series
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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
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Mineral Differentiation

• Plate tectonics
• selective melting, selective recrytallization
• differentiation by density
• Weathering and erosion

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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

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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

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Major Silicate Groups

• Silicon Tetrahedron
• separate tetrahedra olivine
• single chains pyroxene
• double chains amphibole
• sheet silicates micas and clays
• framework silicates feldspars (with Al
  substitution), quartz as pure silica

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Silica Tetrahedron
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Forms of Silicates
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Physical Properties

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

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Deformation Mechanisms
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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

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Clay Viewed from Electron Microscope
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Mineral Identification

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

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Hardness Scale
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X-Ray Diffraction
Braggs Law