Lab 1_ Earth Materials_FA22

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Clark College *

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101

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Geology

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Apr 3, 2024

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pdf

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© Michelle Stoklosa 2022 1 Laboratory Exercise 1: Earth Materials Introduction to Geology II: Earth’s Surface Processes Name____________________ Score: ______/25 Introduction In this exercise, you will examine virtual examples of both rocks and minerals and learn how to identify them. We will be using virtual lab samples organized by Richard Harwood, a professor at Blackhawk College in Moline, Illinois (all website pages used with permission; the links are in the exercise below) and your textbook in order to successfully complete these exercises. Download this exercise and type your answers directly on it. Save your work, include your last name and Lab 1 on the file, upload it to the assignment in Canvas, and click submit. Submit .doc, .docx, or .pdf files only, please! Part A: Mineral Identification Minerals are naturally occurring, solid substances on Earth’s surface. But so are rocks, right? Minerals have a much more precise definition, as you know from your reading of the textbook and the short lesson in Canvas. Use that definition and your textbook (Chapter 3) to help you complete Task A and address the questions below. Task A: Identifying a set of virtual minerals To identify minerals, we observe their physical properties (such as color, crystal form. Hardness, etc.). These properties are defined in Chapter 3 of your textbook and here: http://profharwood.x10host.com/GEOL101/Labs/Minerals/index.htm . After reading over the definitions in the Mineral Physical Properties Chart, click on one of the sample numbers at the bottom and try to describe and identify that mineral (you might want to open the sample page in a new window so that you can refer back to the introduction page when needed). You will click on the physical properties testing buttons to gather your data, then fill out the identification worksheet below it. Compare your descriptions to those of the minerals on the introduction page, also shown here: Mineral Name Diagnostic Physical Properties Apatite Green color, H=5, may show hexagonal crystal form Augite Dark or dull green color, 2 cleavages at ~90 degrees, similar properties to Hornblende Biotite Black color, one perfect direction of cleavage resulting in the mineral pealing into thin, flexible sheets, similar properties to Muscovite Calcite H=3, reacts with HCl, 3 directions of cleavage (rhombic cleavage) Corundum H=9, often shows hexagonal crystal form Dolomite Reacts to HCL in its powdered form, similar properties to calcite Fluorite H=4, 4 directions of cleavage, often purple in color (can be white, clear, yellow, green)
© Michelle Stoklosa 2022 2 Galena Gray, metallic mineral, 3 directions of cleavage (cubic) Garnet Typically reddish brown color, no cleavage, commonly found in twelve-sided crystals (dodecahedrons) Graphite "Pencil lead", soft metallic mineral, gray streak Gypsum H=2, can be scratched with a fingernail Halite "Salt", H=2.5, cannot be scratched with a fingernail, 3 directions of cleavage (cubic), salty taste Hematite Reddish brown streak, "rust" Hornblende Black to dk. green color, 2 directions of cleavage at 120 or 60 degrees, similar properties to Augite Magnetite Magnetic, metallic mineral Muscovite Clear or translucent color, one perfect direction of cleavage resulting in the mineral pealing into thin, flexible sheets, similar properties to Biotite Olivine Apple green or yellowish green color, H=7 (often difficult to determine), conchoidal fracture, no cleavage Orthoclase H=6, salmon pink color is typical, perthitic intergrowths are common, 2 directions of cleavage at 90 degrees, similar properties to plagioclase Plagioclase H=6, white or gray color, striations may be seen on cleavage surface, 2 directions of cleavage at 90 degrees, similar properties to orthoclase Pyrite "Fool's Gold", gold metallic color Quartz H=7, conchoidal fracture, no cleavage, color is typically white or clear but can be pink, red, purple, black Sulfur Yellow color, "rotten egg" smell if burned Talc H=1, very soft, easily scratched by fingernail Which description best matches your observations? Select that mineral name and see if you are correct by clicking on the Grade Identification button. If you were right- congratulations! If not, you know which properties you missed, so try again. Once you have the hang of how these pages work, see if you can figure out which samples numbers on that page are the following minerals. List the correct sample number beside each. (6 points) Mineral Name Sample Number Pyrite Quartz Orthoclase Halite Olivine Biotite Questions: 1. Which of the properties (hardness, color, etc.) was most difficult for you to observe? Explain why in a sentence. (1/2 point) 2. Which of the properties (hardness, color, etc.) was easiest for you to observe? Explain why in a sentence. (1/2 point)
© Michelle Stoklosa 2022 3 Part B: Rock Identification Rocks are also solid, naturally occurring Earth materials, but are defined as a combination of minerals and other materials. The environment in which they form more precisely defines the different rock types. Igneous rocks start as hot, liquid magma below the Earth’s surface. Sedimentary rocks f orm at the Earth’s surface, from processes such as weathering and erosion. Metamorphic rocks typically form slowly, below the Earth’s surface, from high heat and pressure (but without melting). Review each of these rock types in your textbook (there are many images as well), and by reading the information given on each of the websites given below. Task B1: Identifying a few igneous rocks For this task you will need to go to the following website: http://profharwood.x10host.com/GEOL101/Labs/Igneous/index.htm Read through the descriptions of texture and compositions found in igneous rocks, then review the identification chart. Try to identify a few of the samples to see how the website and chart work. When you get the hang of it, address the following questions: Questions: 1. What is the name of sample # 1? (1 point) 2. What is the name of sample # 5? (1 point) 3. What is the name of sample # 7? (1 point) 4. What is the name of sample # 8? (1 point) 5. In a sentence, describe the difference between the terms mafic and felsic . Be sure to describe the meaning of each of these terms and give an example of a mafic and felsic rock. (1 point) 6. Which igneous rock do you think is being shown in the photo below? Explain your reasoning. (1 point)
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