Chapter 5 Outline 1 Roughly 4000 Minerals identified on earth 2 Mineralogists People who study minerals a Began in 1828 with an optical microscope b Used Electron Microscope in 1960 s c Many minerals are detrimental to the environment 3 Minerals Naturally occurring solid formed by Geologic processes Crystalline structure and a definable chemical composition a Naturally Occurring Produced in Nature synthetic minerals are not materials in the geologic sense b Solid State that can maintain its shape indefinitely c Geologic Process i May form by 1 Freezing of molten rock 2 Precipitation of water out of solution 3 Chemical reactions within or on the surface of preexisting rocks ii Biogenic Minerals byproducts of living organisms like calcite in a clam shell are not considered minerals d Definable Chemical Composition i You can write a chemical formula for a mineral e Orderly arrangement of atoms i Atoms are arranged in a fixed pattern that repeats itself over a large region relative to the size of atoms 1 Crystalline solid Orderly pattern 2 Crystal lattice Pattern itself f Inorganic in general i Organic minerals contain carbon hydrogen bonds ii In general because mineralogist do consider 30 organic substances to be minerals g Glass is not a crystalline substance and is not a mineral i Atoms are not arranged in an orderly fashion 4 Physical Properties that distinguish one mineral from a Hardness and magnetization i Scratching ii Holding near magnet iii Placing acid on it b Color way mineral acts with light i Variations in color reflect impurities c Streak Color of powder by pulverizing a mineral d Luster Luster refers to the way a mineral surface scatters light e Hardness ability to resist scratching resistance of bond to be broken i Mohs hardness scale f Specific Gravity i Represents the density of a mineral ratio between the weight of a volume of the mineral and the weight of an equal volume of water at 4 degrees C g Crystal Habit Shape i Morphology shape 1 Single Crystal faces 2 Character of how crystals form in groups or not 3 Dimension it grows 3d or 2d a Blocky platy needle like h Fracture and cleavage Way a mineral breaks i Depends on arrangement of atoms ii If it breaks on planar surfaces it has cleavage iii Conchoidal fractures are smoothly curving clamshell shaped surfaces form in quartz i Special Properties i Ways minerals react ii Chemical reactions 5 50 100 Minerals discovered each year a Baron Berzelius analyzed chemical make up of minerals i Identified by negative ion anion 6 Mineral Classes a Silicates i Silicon Oxygen Tetrahedron 1 Silicon surrounded by 4 oxygen atoms a Pyramid shape with four triangular faces b Oxides c Sulfides d Sulfates e Halides i Metal Cations bonded to oxygen atoms 1 Typical Magnetite and hematite i Metal Cations bonded to a sulfide anion ii Metallic luster iii Ore Minerals i Metal Cation bonded to the SO4 anionic group i The anion in a halide is a halogen ion f Carbonates i CO3 ii Common Calcite and Dolomite g Native metals i Native Metals consist of pure masses of a single metal ii Copper gold 7 Silicate minerals 95 of the continental crust a Independent tetrahedral Independent don t share oxygen atoms i Iron magnesium garnet olivine b Single Chains Share two oxygen atoms each i Pyroxenes elongate crystals with cleavage at 90 degrees to one another 3 oxygen atoms c Double Chain Tetrahedra link to form a double chain by sharing 2 or i Black or dark brown elongate crystals 2 cleavage directions 60 degrees from one another d Sheet Silicates Tetrahedra in this group all share 3 oxygen atoms and e Framework silicates Each tetrahedron shares all 4 oxygen atoms with therefore link to form 2dimensional sheets i Extremely thin flaky sheets micas ii Clay minerals its neighbors forming a 3d structure i Feldspar and quartz ii Ratio 1 2 Chapter 6 Outline 1 Lava up from Volcanos a 60km hr b New Igneous Rock made by freezing of a melt c Igeous from Ignis Latin d Temperature drops below 0 degrees centigrade 2 Magma melt under surface of crust 3 Intrusive Igneous Rock rock made by freeing of magma underground 4 Extrusive igneous rock after it spills out extrudes onto the surface of the earth and comes into contact with the atmosphere or ocean a Pyroclastic debris pyro fire Debris forms when clots of lava fly into the air in lava fountains then freeze into solid chunks b4 hitting the ground i Fine spray of lava Ash b Magma only in special places i Melting as a result of a decrease in pressure Decompression 1 Variation of temperature with depth can be expressed on a graph by a curving line geotherm ii Pressure prevents melting a decrease in pressure permits melting decompression melting c Melting as a result of the addition of volatiles Flux Melting i Volatiles H2O CO2 evap Easily and can exist in gaseous forms ii Melting curve solidus line defining the range of temp and at the earths surface 1 Helps break chemical bonds pressures that rock melts at 1 Wet dry basalt a Wet Contains Volatiles i Water co2 nitrogen hydrogen sulfer dioxide b Dry Volatile Free d Melting as a result of heat transfer from rising magma i Heat flows into and raises the temperature of the surrounding crustal rock e Magma Composition i Silicon and Oxygen ii Liquid grouped in clusters or short chains iii Proportions in percent weight of oxides 1 Common oxides SiO2 iron oxide magnesium oxide iv Felsic Magma 66 76 silica occurrence of feldspar and quartz v Intermediate Magma 52 66 Silica vi Mafic Magma 45 52 silica High in Mafic Minerals 1 MgO FeO or Fe2O3 vii Ultramafic 38 45 Silica f Viscosity Resistance to Flow i Silica tends to Polymerize long chainlike molecules ii Felsic Magmas higher viscosity flow less easily 1 Higher SiO2 the less dense the magma is Felsic less dense 2 Felsic Lower freezing point g Source Rock Composition i Mantle magma is different from crustal magma ii Magma has more silica than original rock 1 Partial Melting Melt carries away silica iii Crystal Mush Enough melt to keep remaining crystals suspended h Assimilation i Magma Mixing magma j Fractional Crystallization i Magma sits in a chamber b4 completely solidifying 1 May collect assimilate rocks in the walls of the chamber i Magma in chambers may come in contact making a whole new i Occurs when a mineral composing the magma freezes at a higher temperature causing some of the minerals to separate removing some atoms from the magma ii Can remove enough atoms that Silica is so aboundant that Felsic Rock Forms 1
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