Igneous Rock Identification - Honors
________ / 15 Lab Grade
Name_________________________________________________Date________________Period__________
Purpose: Practice the terminology for identifying Igneous Rocks.
Materials: 6 igneous rocks
Dichotomous Key
Pre-Questions:
1. Define the following terms:
a. Intrusive: ______________________________________________________________________
b. Extrusive:______________________________________________________________________
c. Porphyritic:____________________________________________________________________
d. Vesiculuar:_____________________________________________________________________
2. Explain what determines the mineral sizes of igneous rocks: ___________________________________
____________________________________________________________________________________
Data Table:
Fill in the table completely! – Use the table on the back of this paper.
Rock Number
Intrusive/Extrusive
Rock Name
1
2
3
4
5
6
7
Conclusion Questions:
3. Which rock was the easiest to identify? Why? __________________________________________________
4. As you travel deeper into the Earth, what happens to the amount of pressure and heat?
__________________________________________________________________________________________
5. Does obsidian have a large grain size or small grain size? _________________________________________
What does that tell you? _______________________________________________________________
6. What does a rock with porphyritic texture look like?
_________________________________________________________________________________________
7. Explain how heat is directly related to the type of igneous rock formed in a region. (2 points)
__________________________________________________________________________________________
__________________________________________________________________________________________
__________________________________________________________________________________________
8. What is partial melting? Explain how partial melting affects igneous rock formation.
__________________________________________________________________________________________
__________________________________________________________________________________________
__________________________________________________________________________________________
9. What relationship does Bowen’s reaction series illustrate? _______________________________________
__________________________________________________________________________________________
__________________________________________________________________________________________
Yes
Is the
rock a
light
color?
Yes
Basalt
Rhyolite
No
Yes
No
Go back to the beginning and start again!
Yes
Go back to the beginning and start
again!
Obsidian
Scoria
Does
the
rock
float in
water?
Yes
Is the
rock
dark
in
color?
No
Yes
Does
the
rock
have
air
holes?
No
Is the
rock
shiny
like
glass?
No
No
Yes
Does the rock
have minerals
you can see
with
magnification?
Pumice
No
Is the
rock a
dark
color?
Gabbro
No
Is the
rock a
dark
color?
Yes
Yes
No
Yes
No
Does the rock have minerals you can see without magnification?
Is the rock
multi-colored?
Granite
Go back to
the
beginning
and start
again!
Go back to the beginning and start
again!