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17. What are metamorphic rocks? What limits the maximum
QUESTIONS FOR THOUGHT temperatures possible in metamorphism? Explain.
18. Describe what happens to the minerals as shale is
1. What are the characteristics that make a mineral different from metamorphosed to slate, then schist, then gneiss. Is it possible to
other solid materials of Earth? metamorphose shale directly to gneiss, or must it go through the
2. Describe the silicate minerals in terms of structural arrangement; slate and schist sequences first? Explain.
in terms of composition. 19. What is the rock cycle? Why is it unique to the planet Earth?
3. Explain why each mineral has its own unique set of physical
properties.
FOR FURTHER ANALYSIS
4. Identify at least eight physical properties that are useful in
identifying minerals. From this list, identify two properties that are
probably the most useful and two that are probably the least useful 1. What are the significant similarities and differences between
in identifying an unknown mineral. Give reasons for your choices. igneous, sedimentary, and metamorphic rocks?
5. Explain how the identity of an unknown mineral is determined 2. Is ice a mineral? Describe reasons to support the idea that ice is a
by finding out what the mineral is not. mineral. Describe reasons to argue that ice is not a mineral.
6. What is a rock? 3. If ice is a mineral, is a glacier a rock? Describe reasons to support
7. Describe the concept of the rock cycle. or argue against calling a glacier a rock according to the
definition of a rock.
8. Briefly explain the basic differences among the three major kinds
of rocks based on the way they were formed. 4. The rock cycle describes how igneous, metamorphic, and
sedimentary rocks are changed into one another. If this is true,
9. Which major kind of rock, based on the way it is formed, would
analyze why most of the rocks on Earth’s surface are sedimentary.
you expect to find most of in Earth’s crust? Explain.
10. What is the difference between magma and lava?
11. What is meant by the “texture” of an igneous rock? What does INVITATION TO INQUIRY
the texture of an igneous rock tell you about its cooling history?
12. What are the basic differences between basalt and granite, the
Building Rocks
two most common igneous rocks of Earth’s crust? In what part of
Earth’s crust are basalt and granite most common? Explain. Survey the use of rocks used in building construction in your com-
munity. Compare the types of rocks that are used for building inte-
13. Explain why a cooled and crystallized magma might have
ferromagnesian silicates in the lower part and riors and those that are used for building exteriors. Where were the
nonferromagnesian silicates in the upper part. rocks quarried? Are any trends apparent for buildings constructed in
14. Is the igneous rock basalt always fine-grained? Explain. the past and those built more recently? If so, are there reasons (cost,
shipping, other limitations) underlying a trend, or is it simply a mat-
15. What are clastic sediments? How are they classified and named?
ter of style?
16. Briefly describe the rock-forming process that changes sediments
into solid rock.

PARALLEL EXERCISES

The exercises in groups A and B cover the same concepts. Solutions to group A exercises are located in appendix E.
Group A Group B
1. A sample of the mineral halite measures 3.18 cm long by 3.06 cm 1. A sample of the mineral sylvite measures 2.68 cm long by
wide by 2.79 cm high and has a mass of 58.75 g. What is its 2.72 cm wide by 2.11 cm high and has a mass of 30.57 g. What is
specific gravity? (The cleavage of halite causes it to break into a its specific gravity? (The cleavage of sylvite causes it to break into
rectangular solid.) a rectangular solid.)
2. A rectangular crystal of sodium plagioclase feldspar in an 2. A rectangular crystal of calcium plagioclase feldspar in an
igneous rock measures 2.89 cm long by 1.86 cm wide by 1.79 cm igneous rock measures 2.99 cm long by 1.82 cm wide by 1.77 cm
high and has a mass of 25.09 g. What is its specific gravity? Based high and has a mass of 26.59 g. What is its specific gravity? Based
on Figure 17.11, does sodium plagioclase feldspar crystallize at on Figure 17.11, does calcium plagioclase feldspar crystallize at
high temperature or low temperature on Bowen’s reaction series? high temperature or low temperature on Bowen’s reaction series?
3. A spherical specimen of the mineral chalcopyrite measures 3.2 cm 3. A spherical specimen of the mineral quartz measures 3.4 cm in
in diameter and has a mass of 72.04 g. What is its specific gravity? diameter and has a mass of 55.64 g. What is its specific gravity?
4. Geologists separate nonferromagnesian silicates from 4. Geologists separate nonferromagnesian silicates from
ferromagnesian silicates by placing sediment in liquid ferromagnesian silicates by placing sediment in liquid
bromoform, which has a specific gravity of 2.89. Feldspar sand tetrabromoethane, which has a specific gravity of 2.96. Olivine
with spherical grains with an average diameter of 0.16 cm and sand with spherical grains with an average diameter 0.158 cm
−3
−3
mass of 5.7 × 10 g are placed in bromoform. Will the sand and mass of 6.76 × 10 g are placed in tetrabromoethane. Will
grains float or sink? the sand grains float or sink?
452 CHAPTER 17 Rocks and Minerals 17-20