CEE 437 Lecture 2 Minerals 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 Structure of Calcite

Crystalline Symmetry Groups

Crystal Forms, Cubic System

Crustal Composition

Bowen’s Reaction Series

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

Silica Tetrahedron

Forms of Silicates

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 Optical microscopy Mineral chemistry, x-ray diffraction

Hardness Scale

X-Ray Diffraction Bragg’s Law