EASC 116 Ch. 2 Minerals

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EASC 116 Ch. 2 Minerals

  1. 1. MINERALS Chapter 2
  2. 2. MINERALSBasic building block of rocksOver 4,000 minerals identifiedMineral Definition (requirements):1) Solid2) Naturally Occurring
  3. 3. Mineral Definition3) Inorganic – no biologic origin4) Definite Chemical CompositionEx: Halite = NaCl Quartz = SiO2
  4. 4. Definite Chemical CompositionCan vary within limits Ex: Olivine = (Mg,Fe)2SiO4Mg and Fe can substitute for each other (Fig. 2.22)
  5. 5. Definite Chemical CompositionEx: Diamond = C (Carbon) Graphite = C (Carbon)
  6. 6. Mineral Definition5) Ordered Crystalline StructureEx: Halite (NaCl)
  7. 7. Ordered Crystalline StructureDiamond = high pressure- complex bonding of carbon atomsGraphite = low pressure - carbon atoms bond in sheets
  8. 8. Mineral Definition1) Solid2) Naturally Occurring3) Inorganic4) Definite Chemical Composition5) Ordered Crystalline Structure
  9. 9. Structure of Minerals1) Atom – smallest building block of an elementComposed of atomic particles - protons (+) - neutrons - electrons (-)
  10. 10. Periodic Table of the Elements(p. 38)
  11. 11. AtomsAtomic Number = number of protons- defines which element atom belongs toAtomic Mass = sum of protons & neutrons
  12. 12. Balanced AtomsNumber of electrons = number of protonsRule:1st energy level = 2 electrons maxAll other energy levels = 8 electrons max
  13. 13. AtomsValence electrons = electrons in outermost orbital shellAtoms bond b/c they want full outer shell of electrons
  14. 14. Types of Bonding1) Ionic BondingIon = atom with an electrical charge (+) or (-)- caused by losing or gaining electrons
  15. 15. Ionic BondingAtoms bond b/c opposites attract (like magnets)Ex: Halite (NaCl)
  16. 16. Types of Bonding2) Covalent Bonding- outer orbital shells overlap- atoms share valence electronsEx: Oxygen gas (O2)
  17. 17. Atomic Bonding3) Metallic bonding- valence electrons move freely between ions- accounts for high electrical conductivity
  18. 18. Structure of Minerals2) Element – composed entirely of same kind of atoms - all atoms have same number of ___________92 naturally occurring elements
  19. 19. ElementSome minerals are elements:Ex: Native Copper Gold Sulfur Graphite
  20. 20. Structure of Minerals3) Compound – combination of two or more elements- characteristics are different than individual elements Ex: Halite NaCl
  21. 21. CompoundMost minerals are compounds: Quartz = SiO2 Galena = PbS (lead sulfide) Hematite = Fe2O3 (iron oxide) Sphalerite = ZnS
  22. 22. Chemical Composition of Crust98.3% of crust composed of 8 elements (Figure 2.19)Other 84 elements share 1.7% of remaining crust- includes gold, zinc, lead, carbon, sulfur, silver, …
  23. 23. Mineral Groups1) Silicate Group - 90% of all minerals Basic building block is the silica tetrahedron SiO44- (Si = silicon; Si+O = silica)
  24. 24. Silica tetrahedron (SiO44-)Negative charge bonds with positive ionsOther six abundant elements of crust are positive ions (Ex: K)
  25. 25. Mineral Groups2) Nonsilicate Group – scarce compared to silicatesIncludes:a) rock-forming minerals Ex: halite, gypsum, calcite
  26. 26. Nonsilicate Mineral Groupb) Native elements Ex: sulfur, copper, goldc) Metal ores Ex: galena (PbS) magnetite (Fe3O4)
  27. 27. Nonsilicate Mineral Groupd) Industrial minerals Ex: fluorite, corundum
  28. 28. Silicate Mineral StructuresSilicate minerals have unique silica tetrahedra structures (Fig. 2.21)- each structure is related to its cleavage patterns (or fracture)
  29. 29. Silicate Mineral StructuresBonds between silica tetrahedra are strongBonds between tetrahedra and positive ions are weakCleavage occurs between tetrahedra and positive ions
  30. 30. Types of Silicate Structures (Fig.2.23)Mineral StructureOlivine Isolated framework(Mg,Fe)2SiO4 No shared oxygensSi:O = 1:4No cleavage b/c (+) ions not in alignment
  31. 31. Types of Silicate StructuresMineral StructureAugite Single chain(Mg,Fe)SiO3 One oxygen is Si:O = 1:3 shared
  32. 32. Types of Silicate Structures Mineral StructureHornblende Double Chain Two oxygens are shared
  33. 33. Types of Silicate StructuresMineral StructureBiotite & Sheet silicatesMuscovite(+) ions link sheets of tetrahedra togetherCreates one plane of cleavage
  34. 34. Types of Silicate StructuresMineral StructureQuartz 3-D frameworkSiO2 structure1:2All oxygen atoms are shared (no cleavage)
  35. 35. “Silica rich” vs. “silica poor”Based on Si:0 ratio- as more oxygen atoms are shared, the percentage of silicon in structure increases (compared to oxygen)
  36. 36. “Silica rich” vs. “silica poor”Ex: “silica poor” Olivine (1:4) (Mg,Fe)2SiO4Ex: “silica rich” Quartz (1:2) SiO2
  37. 37. Silicate MineralsHold clues to the environmental conditions where they formMinerals are stable when conditions are similar to where they formed
  38. 38. Environments:1) Magma crystallizing- quartz, feldspar, micasEx: Bowen’s Reaction Series
  39. 39. Environments:2) Weathering at surface- minerals that are unstable in newconditions at Earth’s surface change into clay mineralsEx: kaolinite
  40. 40. Silicate Minerals3) Mountain building processes (high heat & pressure)Ex: garnet, micas
  41. 41. Economic Minerals(Nonsilicates)Metal OreOre = useful mineral that can be mined for a profit
  42. 42. Profitability depends upon:1) Concentration above the level of average crustal abundance (Figure 2.19)Lower crustal abundance = higher concentration necessary for profitability
  43. 43. ConcentrationEx: CopperCrustal abundance ~0.0135%Copper Ore = 50 times this amount
  44. 44. ConcentrationEx: AluminumCrustal abundance ~8.13%Aluminum ore (bauxite) = 4 times this amount
  45. 45. Profitability depends upon:2) Economic Changes- demand increases, so price increases- previously unprofitable deposits become profitable
  46. 46. Profitability depends upon:3) New technology:- decreases overhead costs- withdraws more mineral from the rockEx: Gold mining with cyanide
  47. 47. Examples of metal ores:Hematite = Fe2O3 = iron oreSphalerite (Zn,Fe)S = zinc oreGalena = PbS = lead ore
  48. 48. RocksMixture of mineralsSome rx are impure quantities of the same mineral Ex: Limestone = calcite (rock) (mineral)
  49. 49. RocksMost rx are composed of several mineralsEx: Granite = quartz, feldspar, hornblende
  50. 50. 3 groups of rocks1)2)3)

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