Rocks And Minerals Lecture


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Rocks And Minerals Lecture

  1. 1. Rocks and Minerals Chapters 4 - 6
  2. 2. Mineral <ul><li>Naturally Occurring </li></ul><ul><li>Inorganic </li></ul><ul><li>Solid </li></ul><ul><li>Specific chemical composition </li></ul><ul><li>Definite crystalline structure </li></ul>
  3. 3. Naturally Occurring & Inorganic <ul><li>Formed in nature </li></ul><ul><ul><li>Natural diamonds are minerals </li></ul></ul><ul><ul><li>Synthetic diamonds are not </li></ul></ul><ul><li>Inorganic </li></ul><ul><ul><li>Are not alive, and never was alive </li></ul></ul>
  4. 4. Question: Is coal a mineral?
  5. 5. Composition <ul><li>Solid </li></ul><ul><li>Definite Composition – Made up of specific compounds or elements </li></ul><ul><ul><li>Copper (Cu), Gold (Au), Silver (Ag) </li></ul></ul><ul><ul><li>Salt (NaCl), Quartz(SiO 2 ) </li></ul></ul><ul><ul><li>Sometimes composition varies slightly (ex : yellow diamonds) </li></ul></ul>
  6. 6. Crystalline structure <ul><li>Crystal – Solid in which atoms are arranged in repeating patterns. </li></ul><ul><ul><li>Atomic Viewer </li></ul></ul><ul><li>Minerals form in open spaces and crystals grow to fill the space </li></ul>
  7. 7. Crystal systems
  8. 8. Mineral Formation <ul><li>Magma – As magma cools, the compounds can no longer move freely and chemically interact to form minerals. If magma cools too quickly, you will have no crystals. </li></ul><ul><li>Solution – If supersaturated, minerals will precipitate. </li></ul><ul><ul><li>Evaporation – if water evaporates solutions become supersaturated </li></ul></ul>
  9. 9. Mineral Groups <ul><li>Silicates (SiO 4 ) Most abundant type of mineral (~96%) </li></ul><ul><ul><li>Ex : Feldspar, Quartz </li></ul></ul><ul><ul><li>Tetrahedral Shape (pg 82) </li></ul></ul>
  10. 10. Carbonates <ul><li>Carbonates (CO 3 ) – Commonly contains metal bonded with CO 3 , combines easily with other minerals. </li></ul><ul><ul><li>Ex : Limestone, Marble and Malachite </li></ul></ul>
  11. 11. Oxides <ul><li>Oxide – Metal and oxygen. </li></ul><ul><ul><li>ex : Hematite and magnetite </li></ul></ul>
  12. 12. Other mineral groups <ul><li>Sulfides (Element + S 2 ) </li></ul><ul><li>Sulfate (Element + SO 4 ) </li></ul><ul><li>Halides (Element + Halide) – NaCl </li></ul><ul><li>Native element (just an element) </li></ul>
  13. 13. Mineral Identification <ul><li>Color – Caused by trace elements or compounds within a mineral </li></ul><ul><ul><li>Least reliable clue to mineral identity </li></ul></ul><ul><li>Luster – The way a mineral reflects light </li></ul><ul><ul><li>Metallic minerals reflect light </li></ul></ul><ul><ul><li>Non-metallic do not shine </li></ul></ul><ul><ul><ul><li>Dull, pearly, waxy or silky </li></ul></ul></ul>
  14. 14. Mineral Identification Cont’d <ul><li>Texture – How minerals feel to the touch. </li></ul><ul><ul><li>smooth, rough, ragged, greasy, soapy, glassy </li></ul></ul>
  15. 15. Mineral Identification cont’d <ul><li>Streak – The color of a mineral when it is broken up and powdered. </li></ul>
  16. 16. Mineral Identification cont’d <ul><li>Hardness – Measure of how easily a mineral can be scratched. </li></ul><ul><ul><li>Moh’s Scale 1 – 10 uses basic items that can be carried anywhere (finger nail, iron nail, glass, streak plate) </li></ul></ul>
  17. 17. Mineral Identification cont’d <ul><li>Minerals break along planes where atomic bonding is weak (mica) </li></ul><ul><li>Cleavage – A mineral that splits evenly along planes </li></ul><ul><li>Fracture – Minerals that break with rough or jagged edges </li></ul>
  18. 18. Mineral Identification cont’d <ul><li>Density – Reflects atomic weight and structure of mineral </li></ul><ul><ul><li>D = M / V </li></ul></ul><ul><li>Specific Gravity – Measure of density using water </li></ul><ul><li>Special properties </li></ul><ul><ul><li>Ex : Double refraction - Calcite </li></ul></ul>
  19. 19. Mineral Uses <ul><li>Ores – Mineral that can mined for a profit. </li></ul><ul><ul><li>Ex : Hematite  Iron </li></ul></ul><ul><ul><li>Ex : Bauxite  Aluminum </li></ul></ul><ul><li>Gems – Valuable minerals prized for rarity and beauty. </li></ul><ul><ul><li>Ex : Rubies and Sapphires, both corundum with trace minerals </li></ul></ul><ul><li>Under Sea Deposits </li></ul><ul><ul><li>No owners  international law </li></ul></ul><ul><ul><li>Not enough technology </li></ul></ul><ul><ul><li>Destroy oceans </li></ul></ul>
  20. 20. Rocks: Mixture of minerals
  21. 21. Igneous Rocks <ul><li>Formed from the cooling of magma </li></ul><ul><ul><li>Crystallization- formation of crystals </li></ul></ul><ul><li>Ignis- Latin-”fire” </li></ul><ul><li>Types </li></ul><ul><ul><li>Intrusive- cool slowly under Earth’s surface, large crystals </li></ul></ul><ul><ul><li>Extrusive- cool quickly above Earth’s surface, small/no crystals </li></ul></ul>
  22. 22. Composition of Magma <ul><li>Slushy mixture of molten rock, gases, and mineral crystals </li></ul><ul><li>Contain Elements: </li></ul><ul><ul><li>O, Si, Al, Fe, Mg, Ca, K, and Na </li></ul></ul><ul><ul><li>Silica (SiO 2 ) is most abundant </li></ul></ul><ul><li>What factors affect magma??? </li></ul>
  23. 23. Origins of Magma <ul><li>Rocks melt between 800-1220 °C </li></ul><ul><li>Found in upper mantle or lower crust </li></ul><ul><li>Geothermal gradient (temperature increase with depth) p101 </li></ul>
  24. 24. Melting Temperatures <ul><li>Affected by water content, silica content, Type of mineral in magma </li></ul><ul><ul><li>Oceanic Crust melts at higher temp, than continental crust  b/c high magnesium and iron, low in water </li></ul></ul><ul><li>Partial Melting- Not all parts of a rock melt at the same time  different minerals are added to magma at different times, changing type of rock formed </li></ul>
  25. 25. Melting Temperatures Cont’d <ul><li>Fractional Crystallization- magma cools and crystallizes in reverse order form melting </li></ul><ul><ul><li>Removing minerals form the magma </li></ul></ul>
  26. 26. Bowen’s Reaction Series <ul><li>Predictable pattern of magma cooling </li></ul><ul><li>Feldspars (calcium rich) change composition to sodium rich rocks gradually </li></ul><ul><li>Iron-Rich rocks change stepwise with fractional crystallization </li></ul><ul><ul><li>Rocks form in order of Bowen’s </li></ul></ul>
  27. 27. Crystal Separation <ul><li>Since Olivine changes to pyroxene during cooling, why is found in nature at all? </li></ul><ul><li>Crystal Separate from magma, preserving olivine </li></ul>
  28. 28. Layered Intrusions <ul><li>Sometimes magma cools in layers. </li></ul><ul><li>These “layered intrusions” often have valuable sources of rare metals </li></ul>
  29. 29. Classifying Igneous Rocks <ul><li>Intrusive/Extrusive </li></ul><ul><li>Mineral Composition </li></ul><ul><ul><li>Felsic- light colored, high silica, Contain Quartz and Feldspars Ex: Granite </li></ul></ul><ul><ul><li>Mafic- dark in color, lower silica, rich in iron and magnesium Ex: Olivine, Amphibole </li></ul></ul><ul><ul><li>Ultra-Mafic-Very low silica and very high iron, Magnesium </li></ul></ul>
  30. 30. Classifying Igneous Rock Cont’d <ul><li>Grain size- dependant on cooling rate (fast-smaller) </li></ul><ul><ul><li>Glassy- Cools very quickly, think air or water cooling lava off </li></ul></ul>
  31. 31. Grain Size <ul><li>Fine Grain- Fast cooling </li></ul><ul><li>Course Grain- Slow cooling </li></ul><ul><li>Porphyritic- Both fast and slow cooling </li></ul>
  32. 32. Igneous Rocks as Resources <ul><li>Useful building materials  interlocking crystals give strength </li></ul><ul><ul><li>Resists weathering </li></ul></ul><ul><li>Ore Deposits  often found in igneous intrusions </li></ul><ul><ul><li>Veins- Left-overs from Bowen/s Reactions are often valuable gems (gold, silver, lead, copper) </li></ul></ul><ul><li>Pegmatites- Veins of very large grain minerals (ores and gemstones) </li></ul>
  33. 34. Diamonds <ul><li>Kimberlites- ultra mafic rock that diamond is found in </li></ul><ul><li>Found 150-300 Km depth (need VERY high pressure) </li></ul>
  34. 35. Buying Diamonds <ul><li>Color- Range from D-Z (D being colorless and Z being bright yellow </li></ul><ul><ul><li>J and K are great bargains! </li></ul></ul><ul><li>Clarity </li></ul><ul><ul><li>Inclusions- Imperfections inside crystal </li></ul></ul><ul><ul><li>VS 1-2 even SI 1 good deals </li></ul></ul>
  35. 36. Buying diamonds <ul><li>Cut- Many ways of cutting </li></ul><ul><ul><li>Beware of brand cuts </li></ul></ul><ul><li>Carat Weight- Size by weight of your gem </li></ul><ul><ul><li>½ carat diamond about $1,500 </li></ul></ul>
  36. 37. Sedimentary Rocks <ul><li>Sediments- pieces of solid material deposited by wind, water, ice, gravity or chemical precipitation </li></ul><ul><li>Weathering- breaking down by physical and chemical processes </li></ul><ul><ul><li>Produces clastic pieces  “broken pieces” </li></ul></ul><ul><li>Erosion- transport of rock (rain, ice) </li></ul><ul><li>Deposition- sediment laid down or sinks to bottom </li></ul>
  37. 38. Erosion/Deposition
  38. 39. Formation of Sedimentary Rocks <ul><li>Lithification- process by which sediments turn to rocks </li></ul><ul><ul><li>Must have thick layers of sediment, increasing pressure and temperature </li></ul></ul><ul><li>Cementation- a chemical process which mineral growth solidifies sediments </li></ul>
  39. 40. Features of Sedimentary Rocks <ul><li>Bedding- horizontal rock layers </li></ul><ul><ul><li>Graded- large particles fall to bottom </li></ul></ul><ul><ul><li>Cross- inclined layers move across a horizontal surface (sand dune) </li></ul></ul>
  40. 41. Features of Sed. Rocks Cont’d <ul><li>Fossils </li></ul><ul><li>Patterns-- waves </li></ul>
  41. 42. Types <ul><li>Clastic- </li></ul><ul><ul><li>Course Grain- </li></ul></ul><ul><ul><ul><li>Round- Conglomerate </li></ul></ul></ul><ul><ul><ul><li>Angular- Breccia </li></ul></ul></ul><ul><ul><li>Medium Grain </li></ul></ul><ul><ul><ul><li>Sandstone-filters drinking water </li></ul></ul></ul><ul><ul><ul><ul><li>Porosity- % of open spaces </li></ul></ul></ul></ul><ul><ul><li>Fine grain- </li></ul></ul><ul><ul><ul><li>Siltstone- traps water </li></ul></ul></ul>
  42. 43. Types Cont’d <ul><li>Chemical- </li></ul><ul><ul><li>Evaporites- formed from evaporation </li></ul></ul><ul><ul><ul><li>Salts </li></ul></ul></ul><ul><ul><li>Organic- remains of once living organisms </li></ul></ul><ul><ul><ul><li>Limestone </li></ul></ul></ul><ul><ul><ul><li>Coal </li></ul></ul></ul>
  43. 44. Metamorphic Rocks <ul><li>Rocks that are changed </li></ul><ul><ul><li>Meta-change </li></ul></ul><ul><ul><li>Morphe-form </li></ul></ul><ul><li>Forces- Heat and Pressure </li></ul>
  44. 45. Types of Metamorphism <ul><li>Regional- When Heat/pressure affect large regions or bands </li></ul>
  45. 46. Types of Metamorphism Cont’d <ul><li>Contact (touch)- Edges of batholith touch an area changing the rocks </li></ul>
  46. 47. Types of Metamorphism Cont’d <ul><li>Hydrothermal- Hot water (near volcanoes change rock) ex: Brimstone </li></ul>
  47. 48. Metamorphic Textures <ul><li>Foliated- wavy bands of crystals Gneiss (formerly granite) </li></ul><ul><li>Non-Foliated- no visible layers </li></ul>
  48. 49. Rock Cycle