Minerals and Rocks

1. Minerals and Rocks Chapter 8 phsc001, chapter 8, yuc

2. Earth’s Crust Materials Crust: upper part of earth • 8 light elements and their compounds make up 89% of crust - silicon and oxygen are most abundant • Initially earth was molten - heavy elements sank - light elements stay on top phsc001, chapter 8, yuc

3. Minerals Minerals • Naturally found • Solid element or compound • Crystal structure - ordered repetition of unit cell (structural unit) - unit cell contain one element or more • Example: table salt crystal phsc001, chapter 8, yuc

4. Crystal Form • Each mineral has unique crystal shape • Minerals can be identified by their crystal structures • No two minerals can have same crystal structure • Graphite and diamond both have carbon but different crystal structures diamond graphite phsc001, chapter 8, yuc

5. Quartz crystal structure Quartz: SiO2 phsc001, chapter 8, yuc

6. Gold Crystal Structure phsc001, chapter 8, yuc

7. Topaz Crystal Structure • Topaz: Al2SiO4(F,OH)2 Aluminum silicate fluoride hydroxide phsc001, chapter 8, yuc

8. Mineral Physical Properties • Crystal form • Hardness : measure of resistance to scratching - Moh’s hardness scale: 1 (weak), 10 (hard) Example: Talc (1), feldspar (6), Diamond (10) • Cleavage: break a long planes of weakness into regular shapes • Fracture: break along curved surfaces with irregular shapes. Minerals that fracture do not have planes of weakness Cleaved mineral Fractured minerals phsc001, chapter 8, yuc

9. ( Mineral Physical Properties Cont • Color : not reliable - minerals found in many colors - chemical impurity give special colors. Corundum ( changes into sapphire, rubies • Density: mass/volume a measure how massive a mineral - silver : 10.5 g/cm3 - gold : 19.3 g/cm3 sapphire Ruby phsc001, chapter 8, yuc

10. Minerals Classification phsc001, chapter 8, yuc

11. Silicates • Contain Mostly silicon and oxygen • Make up 92% of Earth’s crust • Two divisions Ferromagnesian silicates • Ions of iron, magnesium • Darker color, high density, • Example: Biotite, augite, hornblend, Olivine Nonferromagnesian silicates • Lighter color, lower density • Example: muscovite, feldspars, quartz phsc001, chapter 8, yuc

12. Nonsilicates • Contain no silicon-oxygen in crystalline structure • Make up remaining 8% of Earth’s crust • Eight groups of nonsilicates • Carbonates (most found) • Sulfates • Oxides • Sulfides • Halides • Phosphates • Hydroxides • Native elements sulfide Halides (CaF2) phsc001, chapter 8, yuc

13. Rocks • Physical combination of one or more minerals • Most are silicates • Classification: Based on how the rock formed • Igneous • Sedimentary • metamorphic metamorphic phsc001, chapter 8, yuc

14. Igneous Rocks • Formed from magma above or below Earth’s surface. Three stages • High temperature to melt rock • Formation of magma • Cooling and recrystalization of magma Examples • Granite - Light colored, less dense - Made up of quartz, mica, feldspar • Basalt - dark colored, high dense phsc001, chapter 8, yuc

15. Sedimentary Rocks • Formed from dissolved materials from previously existing rocks due to Weathering and erosion caused by rain, snow, wind • Sediments • Accumulations of silt, sand or other materials that settled out of water In lakes, rivers, or oceans Examples: sandstone, shale, coal, limestone sandstone shale Limestone coal phsc001, chapter 8, yuc

16. Sedimentary rocks phsc001, chapter 8, yuc

17. Metamorphic Rocks • Previously existing rocks (igneous or sedimentary) changed by heat, pressure into different rock • Sources of heat, pressure • Movement of the crust (earthquake) • Heating from magma • Temperatures must be high enough to cause recrystallization, but not melting • Example: slate, schist, gneiss phsc001, chapter 8, yuc

18. Rocks Cycle • Rocks transformed from one form to another due environmental conditions like rain, wind, snow, which result in weathering and erosion of rocks. Also, by changes in earth’s interior phsc001, chapter 8, yuc