Review Questions and Problem for Chapter 2:
Classification and Nomenclature of Igneous Rocks.
1. What are the three principal categories of igneous rocks? What characterizes each?
2. What is the difference between aphanitic and fine-grained?
3. How does a felsic mineral differ from a mafic mineral? Which minerals on Bowen’s Series are
mafic? Which are felsic?
4. What does the term acidic mean, and how does it differ from felsic? How does basic differ from
mafic?
5. Does the IUGS system consider pure albite to be an alkali feldspar or a plagioclase feldspar? Why?
6. Why does the QAPF diagram present problems for P-rich rocks? What are the three possible
phaneritic P-rich rock names and on what basis they may they be distinguished?
7. What are the two contrasting P-rich aphanitic rock names and how they are distinguished?
8. What would you name a rock in which the weight percentage of Na2O = 2%, K2O = 4% and SiO2 =
49%?
9. What would you name a rock in which the weight percentage of Na2O = 5%, K2O = 3% and SiO2 =
58%?
10. What would you name a rock in which the weight percentage of Na2O = 8%, K2O = 5% and SiO2 =
57%?
11. What would you name a rock containing 60% ash, 30% fragments between 3 and 15 mm, and 10%
fragments over 64 mm if it were a light pink color?
PROBLEM
Complete the table on the next page, and, using the appropriate diagram, name each rock.