Chapter+3a+-+Earth+Materials - Grotzinger • Jordan...

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Unformatted text preview: Grotzinger • Jordan Understanding Earth Sixth Edition Chapter 3: EARTH MATERIALS Minerals and Rocks © 2011 by W. H. Freeman and Company Chapter 3: Chapter Earth Materials: Materials: Minerals and Minerals Rocks Rocks About Earth Materials About • All Earth materials are composed of All atoms bound together. atoms • Minerals are composed of atoms bonded Minerals together and are the building blocks of rocks. • Rocks are composed of minerals and Rocks they record various geologic processes. they 1. What Are Minerals? 1. Minerals are the building Minerals blocks of rocks. 1. What Are Minerals? What Naturally occurring = found in nature Solid, crystalline substance = atoms are arranged in orderly patterns are Usually inorganic = not a product of living tissue living With a specific chemical formula = unique chemical composition unique Thought questions for this chapter Thought Coal, a natural organic substance that forms from Coal, decaying vegetation, is not considered to be a mineral. However, when coal is heated to high temperatures and buried under high pressures, it is transformed into the mineral graphite. Why is it, then, that coal is not considered a mineral, but graphite is? Explain your reasoning. reasoning. Coal has no defined molecular structure and is organic, Coal Graphite has a defined molecular structure with no evidence of biological origin. evidence 2. The Structure of Matter 2. The atom is the smallest unit The of an element that retains the physical and chemical properties of that element. 2. The Structure of Matter Atomic nucleus: protons and Atomic protons neutrons. Electrons: cloud of moving Electrons cloud particles surrounding the nucleus. nucleus. Example: the carbon atom (C) The Carbon Atom electron cloud atomic nucleus Carbon has 6 electrons… …and a nucleus of 6 protons … …and 6 neutrons having no charge. electron (–) proton (+) neutron 2. The Structure of Matter Isotopes – atoms of the same Isotopes element with different numbers of neutrons. This was wrongly neutrons termed protons in previous version of slides version Example: the carbon atom (C) Example: typically has 6 neutrons and 6 protons (called C12), but there are protons ), 13 13 14 2. The Structure of Matter Chemical reactions – interactions of the atoms of two or more elements in certain fixed proportions. Example: H + H + O = H2O Example: Example: Na + Cl = NaCl 2. The Structure of Matter Chemical compounds that are minerals form by: electron sharing electron or electron transfer Electron Sharing: Electron Carbon atoms in a diamond Electron Transfer: Electron Sodium (Na) + chlorine (Cl) = Sodium NaCl (halite) NaCl Electron Transfer: Electron Sodium (Na) + chlorine (Cl) = Sodium NaCl (halite) NaCl sodium ion (circled in red) rounded by 6 chloride ions d in yellow), and vice versa. in 3. The Structure of Minerals 3. How do minerals form? Crystallization – atoms come together in the proper proportion and proper arrangement 3. The Structure of Minerals Electrical charges of atomic ions Electrical Cation – positively charged Anion – negatively charged Atomic ions arrange themselves Atomic according to charge and size. according 3. The Structure of Minerals The forces of electrical attraction between protons (+) and electrons (-) that hold minerals and other chemical compounds together covalent bonds covalent ionic bonds metallic bonds 3. The Structure of Minerals When do minerals form? When • During cooling of molten rock • During evaporation of water • Upon changes in temperature Upon and pressure on existing minerals minerals 4. Classes of Rock-forming Minerals Chemical classes of minerals: Chemical • • • Silicates – contain O and Si Carbonates – contain C and O Oxides – contain O and Oxides metallic cations metallic • Sulfides – contain S and metallic Sulfides cations cations • Sulfates – contain SO4 and metallic cations cations 4. Classes of Rock-forming Minerals Chemical classes (cont.): Chemical • • • Halides – contain Cl, F, I, or Br Hydroxides – contain OH Native elements – masses of all Native the same element metallically bonded bonded Quartz structure Silicate ion (SiO44–) The silicate ion forms tetrahedra. Oxygen ions (O2–) Silicon ion (Si4+) Tetrahedra are the basic building blocks of all silicate minerals. About 95% of Earth’s minerals are silicates. Thought questions for this chapter Thought Draw a simple diagram to show how silicon and oxygen in Draw silicate minerals share electrons. silicate You need to be able to do this without looking at your You notes! notes! 4. Classes of Rock-forming Minerals Types of silicate minerals: Types Isolated silica tetrahedra Single-chain linkages Double-chain linkages Sheet linkages Frameworks Mineral Chemical formula Cleavage planes and number of cleavage directions 1 plane Olivine Isolated tetrahedra (Mg, Fe)2SiO4 2 planes at 90° Pyroxene Silicate structure Single chains (Mg, Fe)SiO3 2 planes at 60° and 120° 1 plane Micas Sheets 2 planes at 90° Amphibole Double chains Three­dimensional framework Ca2(Mg, Fe)5Si8O22(OH)2 Muscovite: KAl2(AlSi3O10)(OH)2 Biotite: K(Mg, Fe)3AlSi3O10(OH)2 Feldspars Orthoclase feldspar: KAlSi3O8 Plagioclase feldspar: (Ca, Na) AlSi3O8 Specimen Thought questions for this chapter Thought Diopside, a pyroxene, has the formula (Ca, Mg)2Si2O6. What does that tell you about its crystal structure and cation substitution? Ca and Mg can exist in varying quantities quantities What physical properties of sheet silicates (mica family) What are related to are their crystal structure? Micas are sheet silicates and they cleave in single Micas cleavage planes. cleavage 5. Physical Properties of Minerals 5. Uses of physical properties: Mineral identification Industrial application of Industrial minerals minerals Thought questions for this chapter Thought Aragonite, with a density of 2.9 g/cm3, has exactly the has same chemical composition as calcite, which has a density of 2.7 g/cm3. Other things being equal, which of density Other these two minerals is more likely to have formed under high pressure? Aragonite because it is denser. high There are at least seven physical properties one can There use to identify an unknown mineral. Which ones are most useful in discriminating between minerals that look similar? Describe a strategy that would allow you to prove that an unknown clear calcite crystal is not the same mineral as a known clear crystal of quartz. same Quartz is harder than average so you would probably base Quartz your strategy on hardness your Thought questions for this chapter Thought Choose two minerals from Appendix 4 that you think Choose might make good abrasive or grinding stones for sharpening steel, and describe the physical properties that cause you to believe they would be suitable for that that purpose. purpose. Anything of greater than a hardness 7 or greater would work but you would need cheap abundant minerals. work 6. What Are Rocks? 6. Rocks are naturally occurring solid aggregates of minerals, or in some cases, non-mineral solid matter. cases, Identity is determined by: texture composition 6. What Are Rocks? 6. Rocks are classified into three groups: groups: Igneous Sedimentary Metamorphic 6. What Are Rocks? 6. Igneous Rocks Igneous Sedimentary Rocks Sedimentary Metamorphic Rocks Metamorphic Thought questions for this chapter Thought In some bodies of granite, we can find very large crystals, In some as much as a meter across, yet these crystals tend to have few crystal faces. What can you deduce about the conditions under which these large crystals grew? They grew out of a melt which restricted crystal growth as the crystals grew into each other. crystals Which igneous intrusion would you expect to have a wider Which contact metamorphic zone: one intruded by a very hot magma or one intruded by a cooler magma? Hot magma – greater thermal gradient. greater Where are igneous rocks most likely to be found? How Where could you be certain that the rocks were igneous and not 7. The Rock Cycle 7. Igneous Rocks in North America Sedimentary Rocks in North America Metamorphic Rocks in North America Thought questions for this chapter Thought What geologic processes transform a sedimentary rock What into an igneous rock? into Subduction and remelting. Describe the geologic processes by which an igneous Describe rock is transformed into a metamorphic rock and then exposed to erosion. Heat and pressure..tends to occur during plate collisions which cause upwarping of crust. Then things erode “downhill” Then Using the rock cycle, trace the path from a magma to a Using granitic intrusion to a metamorphic gneiss to a sandstone. Be sure to include the roles of the plate tectonics climate systems and the specific processes that create rocks. You should be able to do this using slide 41 above You 8. Concentrations of Valuable Mineral Resources Mineral Types of ore minerals: Vein deposits Disseminated deposits Igneous deposits Sedimentary deposits 8. Concentrations of Valuable 8. Mineral Resources Mineral Sedimentary deposits: Sedimentary Copper, iron, other metals Gold, diamonds, other Gold, heavy minerals (placers) heavy Kaolinite (clay) Kaolinite Salts Thought questions for this chapter Thought Back in the late 1800s, gold miners used to pan for gold Back by placing sediment from rivers in a pan and filtering water through the pan while swirling the pan’s contents. The miners wanted to be certain that they had found real gold and not pyrite (“fool’s gold”). Why did this method work? What mineral property does the process of panning for gold use? What is another possible method for distinguishing between gold and pyrite? for Gold is denser than pyrite so you are using specific Gold gravity. You can also use malleability and streak. gravity. Key terms and concepts Anion Anion Atomic mass Atomic number Bedding Biological sediment Carbonate Cation Chemical sediments Cleavage Color Contact metamorphism Covalent bond Crystal Crystal habit Key terms and concepts Density Density Disseminated deposit Electron sharing Electron transfer Erosion Fracture Grain Hardness Hydrothermal solution Igneous rock Ion Ionic bond Isotope Lithification Key terms and concepts Luster Luster Magma Metallic bond Metamorphic rock Mineral Mineralogy Mohs scale of hardness Ore Oxides Polymorph Precipitate Regional metamorphism Rock Rock cycle Key terms and concepts Sediment Sediment Sedimentary rock Silicate Siliclastic sediments Specific gravity Streak Sulfate Sulfide Texture Trace element Vein Weathering ...
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This note was uploaded on 07/12/2011 for the course EAS 2600 taught by Professor Ingalls during the Summer '08 term at Georgia Tech.

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