EASC 116 Ch. 2 Minerals
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EASC 116 Ch. 2 Minerals

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    EASC 116 Ch. 2 Minerals EASC 116 Ch. 2 Minerals Presentation Transcript

    • MINERALS Chapter 2
    • MINERALSBasic building block of rocksOver 4,000 minerals identifiedMineral Definition (requirements):1) Solid2) Naturally Occurring
    • Mineral Definition3) Inorganic – no biologic origin4) Definite Chemical CompositionEx: Halite = NaCl Quartz = SiO2
    • Definite Chemical CompositionCan vary within limits Ex: Olivine = (Mg,Fe)2SiO4Mg and Fe can substitute for each other (Fig. 2.22)
    • Definite Chemical CompositionEx: Diamond = C (Carbon) Graphite = C (Carbon)
    • Mineral Definition5) Ordered Crystalline StructureEx: Halite (NaCl)
    • Ordered Crystalline StructureDiamond = high pressure- complex bonding of carbon atomsGraphite = low pressure - carbon atoms bond in sheets
    • Mineral Definition1) Solid2) Naturally Occurring3) Inorganic4) Definite Chemical Composition5) Ordered Crystalline Structure
    • Structure of Minerals1) Atom – smallest building block of an elementComposed of atomic particles - protons (+) - neutrons - electrons (-)
    • Periodic Table of the Elements(p. 38)
    • AtomsAtomic Number = number of protons- defines which element atom belongs toAtomic Mass = sum of protons & neutrons
    • Balanced AtomsNumber of electrons = number of protonsRule:1st energy level = 2 electrons maxAll other energy levels = 8 electrons max
    • AtomsValence electrons = electrons in outermost orbital shellAtoms bond b/c they want full outer shell of electrons
    • Types of Bonding1) Ionic BondingIon = atom with an electrical charge (+) or (-)- caused by losing or gaining electrons
    • Ionic BondingAtoms bond b/c opposites attract (like magnets)Ex: Halite (NaCl)
    • Types of Bonding2) Covalent Bonding- outer orbital shells overlap- atoms share valence electronsEx: Oxygen gas (O2)
    • Atomic Bonding3) Metallic bonding- valence electrons move freely between ions- accounts for high electrical conductivity
    • Structure of Minerals2) Element – composed entirely of same kind of atoms - all atoms have same number of ___________92 naturally occurring elements
    • ElementSome minerals are elements:Ex: Native Copper Gold Sulfur Graphite
    • Structure of Minerals3) Compound – combination of two or more elements- characteristics are different than individual elements Ex: Halite NaCl
    • CompoundMost minerals are compounds: Quartz = SiO2 Galena = PbS (lead sulfide) Hematite = Fe2O3 (iron oxide) Sphalerite = ZnS
    • 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, …
    • Mineral Groups1) Silicate Group - 90% of all minerals Basic building block is the silica tetrahedron SiO44- (Si = silicon; Si+O = silica)
    • Silica tetrahedron (SiO44-)Negative charge bonds with positive ionsOther six abundant elements of crust are positive ions (Ex: K)
    • Mineral Groups2) Nonsilicate Group – scarce compared to silicatesIncludes:a) rock-forming minerals Ex: halite, gypsum, calcite
    • Nonsilicate Mineral Groupb) Native elements Ex: sulfur, copper, goldc) Metal ores Ex: galena (PbS) magnetite (Fe3O4)
    • Nonsilicate Mineral Groupd) Industrial minerals Ex: fluorite, corundum
    • Silicate Mineral StructuresSilicate minerals have unique silica tetrahedra structures (Fig. 2.21)- each structure is related to its cleavage patterns (or fracture)
    • Silicate Mineral StructuresBonds between silica tetrahedra are strongBonds between tetrahedra and positive ions are weakCleavage occurs between tetrahedra and positive ions
    • 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
    • Types of Silicate StructuresMineral StructureAugite Single chain(Mg,Fe)SiO3 One oxygen is Si:O = 1:3 shared
    • Types of Silicate Structures Mineral StructureHornblende Double Chain Two oxygens are shared
    • Types of Silicate StructuresMineral StructureBiotite & Sheet silicatesMuscovite(+) ions link sheets of tetrahedra togetherCreates one plane of cleavage
    • Types of Silicate StructuresMineral StructureQuartz 3-D frameworkSiO2 structure1:2All oxygen atoms are shared (no cleavage)
    • “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)
    • “Silica rich” vs. “silica poor”Ex: “silica poor” Olivine (1:4) (Mg,Fe)2SiO4Ex: “silica rich” Quartz (1:2) SiO2
    • Silicate MineralsHold clues to the environmental conditions where they formMinerals are stable when conditions are similar to where they formed
    • Environments:1) Magma crystallizing- quartz, feldspar, micasEx: Bowen’s Reaction Series
    • Environments:2) Weathering at surface- minerals that are unstable in newconditions at Earth’s surface change into clay mineralsEx: kaolinite
    • Silicate Minerals3) Mountain building processes (high heat & pressure)Ex: garnet, micas
    • Economic Minerals(Nonsilicates)Metal OreOre = useful mineral that can be mined for a profit
    • Profitability depends upon:1) Concentration above the level of average crustal abundance (Figure 2.19)Lower crustal abundance = higher concentration necessary for profitability
    • ConcentrationEx: CopperCrustal abundance ~0.0135%Copper Ore = 50 times this amount
    • ConcentrationEx: AluminumCrustal abundance ~8.13%Aluminum ore (bauxite) = 4 times this amount
    • Profitability depends upon:2) Economic Changes- demand increases, so price increases- previously unprofitable deposits become profitable
    • Profitability depends upon:3) New technology:- decreases overhead costs- withdraws more mineral from the rockEx: Gold mining with cyanide
    • Examples of metal ores:Hematite = Fe2O3 = iron oreSphalerite (Zn,Fe)S = zinc oreGalena = PbS = lead ore
    • RocksMixture of mineralsSome rx are impure quantities of the same mineral Ex: Limestone = calcite (rock) (mineral)
    • RocksMost rx are composed of several mineralsEx: Granite = quartz, feldspar, hornblende
    • 3 groups of rocks1)2)3)