Thought Questions

Question 3.15

Describe the creation of an ore mineral deposit by hydrothermal activity.

Question 3.16

Draw a simple diagram to show how silicon and oxygen in silicate minerals share electrons.

Question 3.17

Diopside, a pyroxene, has the formula (Ca,Mg)2Si2O6. What does this formula tell you about its crystal structure and cation substitution?

Question 3.18

In some bodies of granite, we can find very large crystals, some as much as a meter across, yet these crystals tend to have few crystal faces. What can you deduce about the conditions under which these large crystals grew?

Question 3.19

What physical properties of sheet silicates are related to their crystal structure and bond strength?

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Question 3.20

Choose two minerals from Appendix 4 that you think might make good abrasive or grinding stones for sharpening steel, and describe the physical property that causes you to believe they would be suitable for that purpose.

Question 3.21

Aragonite, with a density of 2.9 g/cm3, has exactly the same chemical composition as calcite, which has a density of 2.7 g/cm3. Other things being equal, which of these two minerals is more likely to have formed under high pressure?

Question 3.22

There are at least seven physical properties one can use to identify an unknown mineral. Which ones are most useful in discriminating between minerals that look similar? Describe a strategy that would allow you to prove that an unknown clear calcite crystal is not the same mineral as a known clear crystal of quartz.

Question 3.23

Coal, a natural organic substance that forms from decaying vegetation, is not considered to be a mineral. However, when coal is heated to high temperatures and buried under high pressures, it is transformed into the mineral graphite. Why is it, then, that coal is not considered a mineral, but graphite is? Explain your reasoning.

Question 3.24

What geologic processes transform a sedimentary rock into an igneous rock?

Question 3.25

Which igneous intrusion would you expect to have a wider contact metamorphic zone: one of a very hot magma or one consisting of a cooler magma?

Question 3.26

Describe the geologic processes by which an igneous rock is transformed into a metamorphic rock and then exposed to erosion.

Question 3.27

Using the rock cycle, trace the path from a magma to a granitic intrusion to a metamorphic gneiss to a sandstone. Be sure to include the roles of the plate tectonic and climate systems and the specific processes that create the rocks.

Question 3.28

Where are igneous rocks most likely to be found? How could you be certain that the rocks were igneous and not sedimentary or metamorphic?

Question 3.29

Back in the late 1800s, gold miners used to pan for gold by placing sediment from rivers in a pan and filtering water through the pan while swirling the pan’s contents. The miners wanted to be certain that they had found real gold and not pyrite (“fool’s gold”). Why did this method work? What mineral property does the process of panning for gold use? What is another possible method for distinguishing between gold and pyrite?