Ch 15 Rocks/Minerals Review Guide
1. What two properties are used to classify rocks?
2. A quartz crystal has one silicon atom for every two oxygen atoms. The ratio of silicon atoms to oxygen atoms is 1:2. If there are 8 million oxygen atoms in a sample of quartz, how many silicon atoms are there?
3. What two properties are used to classify igneous rock?
4. How do you determine a mineral's streak?
5. What is the difference between cleavage and fracture?
6. Identify how a mineral's physical and chemical properties can influence the mineral's development into everyday items.
7. If two minerals have the same hardness, which other properties could you use to determine the minerals' identities? Explain your answer.
8. Name and describe at least four physical properties that can be used to identify minerals.
9. How might an area of Earth's surface look after a period of uplift?
10. Some sedimentary rock is buried deep inside the Earth. Predict the next step in the rock cycle.
11. If you need a saw to cut through quartz, would you purchase a blade made from fluorite or one made from corundum? Explain.
12. How does the cooling rate of magma affect the texture of an igneous rock?
13. Compare a sill with a dike. What makes them different from each other?
14. Describe the process by which clastic sedimentary rock forms.
15. Explain the difference between chemical limestone and organic limestone.
16. List two sedimentary rock structures, and explain how they record geologic processes.
17. Both clastic and chemical sedimentary rocks are classified by texture and by composition. Which property is more useful for classifying each type of sedimentary rock? Explain.
18. Explain how minerals react chemically to form new minerals during metamorphism.
19. What is the difference between foliated and nonfoliated metamorphic rock?
20. If you had two metamorphic rocks, one with garnet crystals and the other with chlorite crystals, which one probably formed at a deeper level in the Earth's crust? Explain.
For each pair of terms, explain how the meanings of the terms differ.
21. fracture/cleavage
22. extrusive/intrusive
23. color/streak
24. density/hardness
25. mineral/rock
26. foliated/nonfoliated
27. Define the term mineral.
28. Summarize the rock cycle.
29. An igneous rock forms at the surface of the Earth. Predict the next step in the rock cycle. Explain your answer.
30. In one or two sentences, explain how the cooling rate of magma determines the texture of the igneous rock that forms.
31. Suppose you have three rings; one has a diamond, one has an amethyst (purple quartz), and one has a topaz. You mail the rings in a small box to your friend. When the box arrives, two of the gems are damaged. One gem, however, is more damaged than the other. What scientific reason can you give for the difference in damage?
32. If you were looking for fossils in the rocks around your home and the rock type that was closest to your home was metamorphic, would you find many fossils? Why or why not?
33. Imagine that you want to quarry, or mine, granite. You have all of the equipment, but you have two pieces of land to choose from. One area has a granite batholith under it, and the other has a granite sill. If both plutonic bodies are at the same depth, which one would be a better choice for you? Explain your answer.
34. Imagine that you work at a jeweler's shop and someone brings in some gold nuggets that they want to sell. You are not sure if the nuggets are real gold. Which physical properties would help you determine whether to buy the nuggets?
The curve on the graph below shows how the melting point of a particular rock changes with increasing temperature and pressure. Use the graph to answer the questions below.
35. Would you find liquid or solid at point A? at point B? Explain.
36. Points C and D represent different temperature and pressure conditions for a single, solid rock. Why does this rock have a higher melting temperature at point D than it does at point C?
37. Use the following terms to create a concept map: minerals, oxides, nonsilicates, carbonates, silicates, mica, calcite, and quartz.
38. Why is color not always a reliable way of identifying a mineral?
39. What affects the way a rock changes through the rock cycle?
40. Describe felsic and mafic rocks, and name three elements that occur in each type of rock.
41. What is the difference between intrusive and extrusive rock?
42. How does chemical limestone form?
43. What is stratification, and why is it important to Earth scientists?
44. Explain what a regionally metamorphosed rock is.
45. What does the composition of a metamorphic rock tell you about the rock's origin and formation?
46. Why isn't color very useful for classifying minerals?
47. Describe how two of the three types of sedimentary rock are formed.
48. Describe the difference between foliated and nonfoliated metamorphic rock.
49. Gold classified as 24 karat is 100 percent gold. Gold classified as 14 karat is 14 parts gold and 10 parts another, similar metal.
a. What is the percentage of pure gold in 14-karat gold?
b. What is the percentage of similar metals?
50. Rebecca found a glimmering crystal that looked like a diamond, but Judy said it was only quartz. How could Rebecca use a crystal that she already knows is quartz to find out if her crystal is diamond or quartz? How else could she try to determine whether she found a diamond?
51. Use the table to answer the item that follows.
Comparative Hardness ScaleHardness / Common material
2.5 / fingernail
3 / copper penny
5 / steel knife blade
Bobby found a rock that he could scratch with his knife. The rock scratched a penny. Estimate the hardness of the rock.
52. Use the following terms to complete the concept map below: luster, nonsilicate minerals, carbonates, hardness, silicate minerals, chemical composition.
Ch 15 Rocks/Minerals Review Guide
Answer Section
SHORT ANSWER
1. composition and texture
2.
3. texture and composition (color)
4. You determine a mineral's streak by scraping the mineral across a ceramic streak plate. The color of the material that rubs off the mineral sample is the mineral's streak.
5. If a mineral has cleavage, it breaks along flat surfaces. Fracture is the way a mineral breaks along curves or irregular surfaces.
6. Answers will vary. Sample answer: The chemical properties of a mineral determine whether it will make a good cement, medicine, building material, or fertilized. The physical properties of a mineral determine whether it will make a good abrasive, gemstone, or cutting tool.
7. Answers will vary but should indicate that color is not a reliable test.
8. Answers will vary. Students may choose to describe color, luster, streak, cleavage, fracture, hardness, density, or special properties.
9. Uplift causes areas of Earth's crust to rise to higher elevations. After uplift, an area of the Earth's crust would probably look like a mountain range.
10. Answers will vary. Sample answer: If rock is buried deep inside the Earth, it will either be metamorphosed by heat and pressure or be melted to form magma.
11. Sample answer: I would purchase a blade made from corundum, because it is made of a mineral that is harder than quartz.
12. When magma cools slowly, crystals have a long time to grow, so the igneous rock that forms is coarse grained. When magma cools quickly, crystals have a short time to grow, so the igneous rock that forms is fine grained.
13. A sill intrudes rock parallel to the surrounding rock layers. A dike cuts across the surrounding rock layers.
14. Clastic sedimentary rock forms when sediments are compacted and cemented together.
15. Chemical limestone forms when dissolved calcium carbonate, CaCO3, separates out of a solution such as water. Organic limestone is made of CaCO3 from the remains of living organisms.
16. Answers will vary. Students could explain how strata, ripple marks, cross-beds, and fossils record geologic processes.
17. Texture is more useful in classifying clastic sedimentary rock because clastic sedimentary rock is made of different sizes of sediments. Composition is more useful in classifying chemical sedimentary rock because chemical sedimentary rock forms from different materials that crystallize out of solution.
18. Rocks metamorphose because of increased pressure and increased temperature. Minerals that were present when the rock formed may no longer be stable. These minerals react chemically with other minerals in the rock to form new minerals that are stable under the new pressure and temperature.
19. The two types of rock differ in texture. Foliated metamorphic rock consists of minerals that are arranged in planes or bands. The minerals in nonfoliated metamorphic rock do not appear to be arranged in a pattern.
20. The rock with garnet crystals would probably have formed deeper in the Earth because the mineral garnet forms at a higher temperature and at a higher pressure than the mineral chlorite.
21. If a mineral breaks along a curved or irregular surface, it has fracture. If a mineral breaks along flat surfaces, it has cleavage.
22. Extrusive igneous rock forms at the Earth's surface. Intrusive igneous rock forms below the Earth's surface.
23. Streak is the color of a mineral in powdered form. The color of a mineral may change, but the mineral's streak is always the same.
24. The hardness of a mineral is its resistance to being scratched, while the density of a mineral is a measure of the amount of matter in a given space.
25. Minerals are naturally formed, inorganic solids that have repeating three-dimensional structures. Rock is a solid mixture of one or more minerals.
26. The minerals in foliated metamorphic rock are arranged in bands. Nonfoliated metamorphic rock does not have bands of minerals.
27. A mineral is a naturally occurring inorganic solid that has a repeating three-dimensional structure.
28. The rock cycle is the process by which all the rock material on Earth is changed into new rock.
29. Rock at the Earth's surface will be affected by weathering and erosion because it is exposed to air and water.
30. Magma that cools quickly forms fine-grained igneous rock. Magma that cools slowly forms coarse-grained igneous rock.
31. Each mineral has a different hardness. The hardest mineral was damaged the least. (The diamond will not be damaged, the topaz will be slightly damaged, and the amethyst will be the most damaged.)
32. You would not find many fossils where you lived because fossils are found in sedimentary rock, not metamorphic rock. (Occasionally, fossils are preserved in metamorphic rock that was once sedimentary rock.)
33. The property with the batholith would be a better buy because batholiths are much bigger than sills.
34. Students should suggest performing several tests to see whether the mineral is gold. Gold is very dense and soft, so one would start with density and hardness tests.
35. Point A is liquid, and point B is solid. Everything above the curve on the graph is liquid, while everything below the curve is solid.
36. Although the rock is at a higher temperature at point D, it has much more pressure on it, which keeps it solid.
37.
38. Factors such as weathering and the inclusion of impurities can affect the mineral's color.
39. the location of the rock and the processes it undergoes
40. Felsic rock is lighter in color and weight ad is rich in aluminum, silicon, sodium, and potassium. Mafic rock is darker and heavier and is rich in iron, magnesium, and calcium.
41. Intrusive rock forms from magma that solidifies while still underground, while extrusive rock forms from magma that solidifies after it has reached the surface.
42. It forms when calcium carbonate crystallizes out of sea water.
43. Stratification is the layering of rock. It is important because it records many events in Earth's history as well as erosion and deposition rates.
44. A regionally metamorphosed rock has been changed by intense pressure and heat across great regions of the crust rather than by direct contact with magma.
45. Different metamorphic minerals indicate the different temperature and pressure conditions that existed when the rock formed.
46. The color of a mineral's streak—the mark left behind when a mineral is rubbed against a hard plate—is not always the same color as a mineral sample. Unlike the surface color of a mineral, streak is not affected by air or water. For this reason, color isn't very useful for classifying minerals, so streak is used instead.
47. Students should give two of the following: Clastic sedimentary rock forms when rock or mineral fragments are cemented together. Chemical sedimentary rock forms when minerals crystallize out of a solution of minerals and water. Organic sedimentary rock forms from the remains of living things.
48. Foliated metamorphic rock contains minerals that are arranged in planes or bands. Foliated rocks tend to form from rocks that contain a variety of minerals. Nonfoliated metamorphic rock contains minerals that do not appear to be arranged in a pattern. Nonfoliated rocks are commonly made of only one or just a few minerals.
49. a. 14/24 = 0.58 = 58%
b. 100% - 58% = 42% or 10/24 = 0.24 = 24% similar metals
50. Sample answers: She could try to scratch a piece of quartz with her crystal. If her crystal scratches the quartz, it might be diamond. Rebecca could measure the mass and volume of her sample, then compare her crystal's density with that of quartz. She could also compare the lusters of the two crystals.
51. The rock's hardness is greater than three but less than five.
52.