2. Each of the following statements describes a silicate mineral or mineral group. In each case, give the appropriate mineral name.

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Marianna Booth
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1 LAST NAME: FRIST NAME: INSTRUCTIONS MIDTERM EXAM # 2 (worth 100 points) There are 18 questions in this test. Print out the test on a white paper and answer all questions. Give all your answers in the space provided; do not exceed the given space. Write legibly. Answers where the handwriting is difficult to read will receive substandard grade. Due date: Thursday, January 26, 8:00 am MINERALS (25 points) 1. Using the geologic definition of mineral as your guide, determine which of the items on this list are minerals and which are not. If not a mineral, explain. (7 points) ITEM OBSIDIAN GLACIAL ICE CUBIC ZIRCONIA DINOSAUR TOOTH BOTTLED MINERAL WATER RUBY PEARL MINERAL, YES OR NO? IF NOT A MINERAL, EXPLAIN WHY NOT 2. Each of the following statements describes a silicate mineral or mineral group. In each case, give the appropriate mineral name. (6 points) DESCRIPTION A common silicate mineral made entirely of silicon and oxygen A silicate mineral that is characterized by striations Forms at a depth of more than 100 miles below the Earth s surface Possesses no cleavage This mineral readily dissolves in water It s the lead in pencils MINERAL NAME Page 1 of 5

2 3. Name the three countries that produce the most gold. (3 points) 4. While mineral hunting, if you found a red mineral and had hopes that it was a ruby, how would you determine what it is using the hardness (scratch) test? Assume that you have at hand all 10 minerals of the Mohs scale minerals. Elaborate your answer. (5 points) 5. Suppose you have a 24-Karat gold and a 24-Carat diamond. Based on this information, carefully read the following questions and provide a well thought-out and complete answer for each. (4 points) i) In terms of purity, which one is pure: the gold, the diamond, both? Why? ii) Which one would cost more, the 24-Karat gold or the 24-Carat diamond? Why? IGNEOUS ROCKS (25 points) 6. Is it possible for two igneous rocks to have the same mineral composition but be different rocks? Use an example to support your answer. (5 points) 7. The statements that follow relate to terms used to describe igneous rock textures. For each statement, identify the appropriate term. (5 points) DESCRIPTION Openings produced by escaping gases The texture of obsidian Consists of crystals too small to be seen without a microscope Texture characterized by two distinctly different crystal sizes Exceptionally large crystals, most exceeding 1 cm in diameter TEXTURE Page 2 of 5

3 8. Describe two mechanisms by which mantle rock can melt without an increase in temperature. How do these magma-generating mechanisms relate to plate tectonics? Explain. (5 points) 9. Mount Whitney, the highest summit (14,505) in the USA, is located in the Sierra Nevada batholith. Based on its location, is Mount Whitney likely composed of granitic, andesitic, or basaltic rocks? Why? (5 points) 10. Match each of the following volcanic landforms with the principle zones of volcanism (convergent plate boundary, divergent plate boundar, or intraplate volcanism) with which it is associated. (5 points) VOLCANIC LANDFORM Yellowstone Deccan Plateau Hawaii s Kilauea East African Rift Mount St. Helens ZONE OF VOLCANISM (Convergent, Divergent, or Intraplate) SEDIMENTARY ROCKS (25 points) 11. During a hike in Utah s Zion National Park, you pick up a sedimentary rock sample. When you examine the sample with your hand lens, you see that the rock consists mainly of rounded glassy particles that appear to be quartz. To be sure, you make two basic tests. When you check for hardness, the rock easily scratches glass, which is what quartz would do. However, when you place a drop of hydrochloric acid on the sample, it fizzes. Explain how a rock that appears to be rich in quartz could effervesce with hydrochloric acid. (7 points) Page 3 of 5

4 12. While on a field trip with your geology class, you stop at an outcrop of sandstone. An examination with hand lens shows that the sandstone is poorly sorted and rich in feldspar and quartz. Your instructor tells you that the sediment was derived from one of two sites in the area: Site # 1: A nearby exposure of weathered basaltic lava flow. Site # 2: An outcrop of granite at the previous field trip stop up the road. Select the most likely site and explain your choice. (8 points) 13. What is the primary basis for distinguishing among detrital rocks? (4 points) 14. Name the most diagnostic feature that you would expect to see in each of the following sedimentary rock types. (6 points) SEDIMENTARY ROCK TYPE Detrital sedimentary rock Chemical sedimentary rock Biochemical (organic) sedimentary rock MOST DIAGNOSTIC FEATURE METAMORPHIC ROCKS (25 points) 15. What is meant by the statement Every metamorphic rock has a parent rock? (5 points) 16. Name at least two features (e.g. type & shape of mineral, texture, structure, etc.) that you find only in one of the rocks listed below, but not in the other two. (9 points) ROCK Sedimentary Igneous Metamorphic TWO FEATURES FOUND ONLY IN THIS ROCK BUT NOT IN THE OTHER TWO ROCKS Page 4 of 5

5 17. Why is heat considered the most important agent of metamorphism? (5 points) Page 5 of 5

Rocks and the Rock Cycle notes from the textbook, integrated with original contributions

Rocks and the Rock Cycle notes from the textbook, integrated with original contributions Alessandro Grippo, Ph.D. Gneiss (a metamorphic rock) from Catalina Island, California Alessandro Grippo review Rocks