Igneous Rock Questions
1. An extrusive felsic rock with a glassy texture is called: ________________
2. An extrusive felsic rock with a vesicular texture is called: ________________
3. An intrusive rock made primarily of pyroxene and olivine is ___________________.
4. A coarse-grained rock made of potassium feldspar, biotite and amphibole is called
_________________.
5. What is the relationship between the size of the crystals in an igneous rock and the length of
time it has taken the rock to solidify?
6. Which of the following cooled most slowly?
a. Granite
c. Basalt
b. Obsidian
d. Pumice
7. Which of the following cooled most quickly?
a. Granite
c. Basalt
b. Obsidian
d. Pumice
8. Which would most likely occur during the formation of igneous rocks?
a. Compression & cementation of sediments
b. Recrystallization of unmelted material
c. Solidification of molten materials
d. Evaporation & precipitation of dissolved sediments
9. Generally as the percentage of felsic minerals in a rock increases, the rock’s color will become
a. Darker & its density will decrease
b. Lighter & its density will increase
c. Darker & its density will increase
d. Lighter & its density will decrease
10. A rock that is fine-grained, low in silicates, and composed of dark-colored minerals and
solidified above ground would be considered to have the characteristics of a(n) ______ rock.
a. Intrusive felsic
c. Extrusive mafic
b. Intrusive mafic
d. Extrusive felsic
11. Some extrusive igneous rocks, such as obsidian, are glassy because they—
a. Cool rapidly
c. Have low melting points
b. Contain water
d. Are made of only one mineral
Rocks you need to know…
• GRANITE
o INTRUSIVE or EXTRUSIVE?
o LARGE crystals or SMALL crystals?
o Used for ________________
o Can be found _________________
• OBSIDIAN
o INTRUSIVE or EXTRUSIVE?
o LARGE crystals or SMALL crystals?
o Used for ________________
• PUMICE
o INTRUSIVE or EXTRUSIVE?
o LARGE crystals or SMALL crystals?
o Used for ________________
• BASALT
o INTRUSIVE or EXTRUSIVE?
o LARGE crystals or SMALL crystals?
o Can be found: _________________