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Atoms, Elements and Minerals

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  1. Atoms, Elements and Minerals A. Changing scales to looking at the elements of the earth and its crust (8 most common) B. Introduction to minerals that comprise rocks (11 most common) C. The silicate minerals (7) D. Other important rock-forming minerals (4) E. Mineral properties

  2. Quartz Biotite Feldspar A. Changing Scale: Zooming in from global view to atomic scale The crust is made of rocks>Rocks are made of minerals > …

  3. A. Changing Scale: Zooming in from global view to atomic scale Rocks are made of minerals > Minerals are made of atoms

  4. Atoms and Elements Electron Shells • Nucleus • Protons • + Charge • Has Mass, Atomic # • Neutrons • 0 Charge • Mass same as One Proton • Atomic Mass # • Electrons • In shells (2, 8, 8…) • - charge (balances each proton +) • Very little Mass

  5. Incomplete electron shells tend to be filled E.g. Chlorine (Cl-) 17 protons (at.# 17) 17 electrons would make it neutral (no charge) with the last shell one electron short {2, 8, 7} Soooo… Tends to grab an electron to fill the third shell Making it a negatively charged Ion (anion) Ions

  6. Ions • Other Common Examples • Sodium, at.# 11 {2, 8, 1}  Na+ • Oxygen, at.# 8 {2,6},  O-2 • Silicon, at.# 14 {2,8,4}  Si+4 Sodium (Cation) Oxygen

  7. Most Common Elements of Earth’s Crust Oxygen: O-2 Silicon: Si+4 Aluminum: Al+3 Iron: Fe+2 or +3 Calcium: Ca+2 Sodium: Na+1 Potassium: K+1 Magnesium: Mg+2

  8. B. Introduction to Minerals • Halite (Rock Salt) • Mineral mined for rock salt and table salt • Na gives electron to Cl • Opposites attract, elements bond • NaCl (Sodium Chloride)

  9. Repeating 3-D pattern forms a Crystalline Solid (or Crystal) Naturally occurring crystals are Minerals Crystalline structure and bonding leads to physical properties: hardness, crystal form, cleavage specific gravity (density) (pg. 38-43) Intro to Minerals Crystal Form 3 planes of cleavage

  10. Silica Tetrahedra • The building block of most common rock forming minerals • Four O2-in a tetrahedral configuration • One Si4+ nested in the center • (4  -2) +4= -4 • (SiO4)-4

  11. Silica Tetrahedra • The building block of most common rock forming minerals • Four O2-in a tetrahedral configuration • One Si4+ nested in the center • (4  -2) +4= -4 • (SiO4)-4

  12. Silica Tetrahedra • The building block of most common rock forming minerals • Four O2-in a tetrahedral configuration • One Si4+ nested in the center • (4  -2) +4= -4 • (SiO4)-4

  13. Silica Tetrahedra • The building block of most common rock forming minerals • Four O2-in a tetrahedral configuration • One Si4+ nested in the center • (4  -2) +4= -4 • (SiO4)-4

  14. Silica Tetrahedra • The building block of most common rock forming minerals • Four O2-in a tetrahedral configuration • One Si4+ nested in the center • (4  -2) +4= -4 • (SiO4)-4

  15. Silica Tetrahedra • The building block of most common rock forming minerals • Four O2-in a tetrahedral configuration • One Si4+ nested in the center • (4  -2) +4= -4 • (SiO4)-4

  16. Silica Tetrahedra • The building block of most common rock forming minerals • Four O2-in a tetrahedral configuration • One Si4+ nested in the center • (4  -2) +4= -4 • (SiO4)-4

  17. Silica Tetrahedra • The building block of most common rock forming minerals • Four O2-in a tetrahedral configuration • One Si4+ nested in the center • (4  -2) +4= -4 • (SiO4)-4 -4

  18. Si and O bond in a tetrahedron shape The basic building block of most minerals of the crust Bond with other tetrahedra and cations to form Silicate Minerals C. Silica Tetrahedra and Silicate Minerals

  19. Naturally Occurring Crystalline Solid With a definite chemical composition A unique composition or A definite range of compositions Mineral Group, e.g. Olivine Definition of Mineral

  20. Silicate Minerals: Examples • E.g., Olivine • Isolated silicate structure • (SiO4)-4 + 2×Fe+2 • Fe2SiO4 • Fe Mg SiO4 • Mg2SiO4 • (Fe,Mg) 2 SiO4  Olivine Mineral Group Definite Range

  21. Silicate Minerals: Examples • E.g., Olivine • Isolated silicate structure • bonded with Fe and/or Mg • Makes up much of Earth’s mantle • Fe/Mg rich • 2/7 = 0.29 = 29% • Silica poor • 1/7 = 0.14 = 14% (Ferromagnesian mineral) % of all atoms

  22. Silicate Minerals: Examples • E.g., Pyroxenes (Mineral Group) • Single Chain Silicate structure • (SiO3)-2 + Fe+2 • FeSiO3 • (Fe,Mg) SiO3 • MgSiO3 (Fe,Mg) SiO3  Pyroxene • Mineral Group • Ferromagnesian

  23. Silicate Minerals: Examples • E.g., Pyroxenes (Group of minerals) • Single Chain Silicate structure • bonded with Fe, Mg, Ca, and Al • Found in Oceanic Crust • Fe/Mg/Ca rich (20%) • Silica poor (<20%)

  24. Single Chain Silicates • E.g., Pyroxenes (SiO3)

  25. Silicate Minerals: Examples • E.g., Amphiboles (Group of minerals) • Double Chain Silicate structure • bonded with Fe, Mg, Ca, and Al • Found in Continental Crust • More silica and less iron than pyroxenes

  26. Double Chain Silicates • E.g., Amphiboles (Si8O22)

  27. Silicate Minerals: Examples • E.g., Micas(Muscovite and Biotite) • Sheet Silicate structure • bonded with Al, K, (biotite has Fe, Mg) • Found in Continental Crust • More silica and less iron than Amphiboles

  28. Sheet Silicates • E.g., Micas (Biotite and Muscovite)(AlSi3O10)

  29. Common Framework Silicates • Feldspar Group • The most common minerals in the crust of the earth • Oceanic Crust: Ca Plagioclase (dark) • Continental Crust: K feldspar (pink) and Na Plagioclase (white) • Quartz • Pure Silica SiO2 • Stable under many conditions • Not easily weathered • Melts at a low temperature • Continental Crust and Sediments

  30. Framework Silicates • E.g., Quartz (SiO2) and Feldspars (AlSi3O8)

  31. Framework Silicates • E.g., Quartz (SiO2) and Feldspar (AlSi3O10)

  32. % of Tot. # of atoms Fe/Mg:Silicon: Systematic SilicateMineralogy 29% 14% <20% 20% <3% 23% <2% 25% (0) 33% (0) 23% (0) 15%* Olivine Pyroxene Group • Fig. 2.9 • From bottom to top • Increasing Fe/Mg/Ca • Decreasing silica • Increasing density • Darker minerals Amphibole Group Mica Group Decreasing Silica Increasing Fe/Mg/Ca Quartz K and Na Feldspar Ca Feldspar Increasing Density

  33. Fig. 2.22 Other ImportantRock-Forming Minerals • Sediments and Sedimentary Rocks • Quartz: resistant to alteration by weathering • Feldspar: moderately resistant to weathering • Clay: most other silicates weather to clay • Carbonates (non-silicates): Deposited in shallow tropical seas be shellfish and coral • Calcite: CaCO3 • Dolomite: CaMgCO3 • Halite: Deposited by evaporating seas

  34. Important Economic Minerals Fig. 2.13 • Elements: • Diamond, Graphite, • Gold, Copper • Sulfur • Iron Oxides: • Hematite (Fe2O3), • Magnetite (Fe3O4) Fig. 21.1

  35. E. Physical Properties Fig. 2.20

  36. Fig. 2.19a E. Physical Properties

  37. Fig. 2.15a E. Physical Properties

  38. E. Physical Properties Fig. 2.15a