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Unit 5: Earth History and the Rock Record Atoms, Minerals, and Rocks Definitions: p. 42 • Atom • Element • Compound • The smallest part of an element that can be identified as that element • Substance made of two or more elements • Substance that cannot be broken down into simpler substance by chemical means Diamond! What are Minerals? • Thousands of them! • They make up the solid geosphere of earth • Some flashy…some common. Used in everything from your cell phone, to jewelry, to cooking… • 5 part Definition: 1. 2. 3. 4. 5. Solid Naturally occuring (not made by people) Inorganic (not made by plants or animals) Set chemical make-up the same throughout whole mineral Set arrangement of atoms (how they are bonded together) What are minerals made of? • Rocks are made of minerals • Minerals are made of elements or compounds of elements – Ex. Gold vs. quartz • Elements are made of atoms Made of two elements SiO2=chemical formula 1 Silicon atom for every 2 oxygen atoms Example: “Salt”=Halite • • • • Solid Inorganic Naturally occuring NaCl=set chemical composition • Set arrangement of atoms Elements form Compounds • 100s of different elements, most solid at room temperature • Combining 2 or more elements creates compounds with different properties than their elements! • Compounds have set proportions (H2O) Common Minerals • Less than 20 of the thousands of minerals are common • Minerals made with silicon and oxygen are the most common (silicate minerals) Rare Mineral Resources • Minerals containing metals are important resources • Minerals that are hard, rare, and considered beautiful are cut and polished for jewelry How do minerals form? • Crystallization – In hot magma, atoms are not bound in crystal form. As magma cools the atoms arrange themselves into crystalline structures forming minerals! – Happens underground or at the surface in volcanically active places • Evaporation/Precipitation – Atoms can be dissolved in solutions of water. If water evaporates or changes temperature or gets too many atoms in it the dissolved atoms may form crystalline solids…minerals! – Happens at bottom of bodies of water, especially where there is volcanically heated hot water dissolving minerals and then cooling when it touches other water or air. Diamonds and Graphite • Why do they have such different properties? – Same composition! – Both minerals! – Arrangement of atoms • Why is one common and the other rare? • Need to understand the basic building blocks of matter and how minerals form and get their physical characteristics Mineral Characteristics • Minerals can be identified based on characteristics such as – Color, crystal shape, hardness, density – Streak, fracture vs. cleavage plane, luster, reaction to acid, magnetism • These characteristics are caused by – The type of elements in the mineral – The arrangement of those elements How could we make our own minerals? • Why is evaporation/precipitation better than crystallization for us? • What elements could we dissolve in water? • What temperature would dissolve the most? • Will the mineral display crystal form or not? • What shape crystals do you think will happen? Color • Some minerals come in more than 1 color… Streak • There are many minerals with the same color…how do you tell them apart? No matter what color the sample of hematite is, it has a red-brown streak! Streak is useful for dark, metallic minerals that are not super hard What are the two major kinds of Luster? • Metallic and non-metallic • Which has metallic luster? Crystal Shapes • Cubic – Pyrite, galena, halite • Trigonal – quartz • Hexagonal – beryl Quartz Quartz breaks irregularly • fracture Mica breaks in flat sheets • Weak cleavage plane in 1 direction Cleavage • Due to weaknesses planes in the atomic structure Mineral ID 1. 2. 3. 4. 5. Quartz Feldspar Feldspar Calcite Hornblende/amphi bole 6. Biotite mica 7. Muscovite mica 8. talc 9. Magnetite 10 Pyrite 11. galena 12. Hematite 13. Graphite 14. Flourite 15. Rose quartz 16. Sulpher 17. Olivine 18. Garnet Earth’s Geosphere • 1st semster: atmosphere, hydrosphere, and exosphere • 2nd semester: geosphere and exosphere • Densest part of planet, materials solid at surface temperatures including rocks and minerals • Earth is a big rocky metallic planet with a thin film of life, water and air • 3 major compositional layers formed through differentiation – Core, mantle, crust – Focus of this unit is on crust • Composed mostly of just 8 elements • Diamond: each carbon bonded to 4 other carbons • Sheets where each carbon is bonded to 3 carbons in hexagon shape. Sheets weekly bonded together • How does this impact the characteristics of the mineral? • http://www.youtube.com/watch?v=Jd9C 40Svt5g