Name:_______________________
Geology 101 Lab Worksheet: Igneous Rocks
Refer to the Igneous Rocks Lab (http://commons.wvc.edu/rdawes/G101OCL/Labs/IgneousLab.html), and
the Igneous Rocks Basics Page and Table (http://commons.wvc.edu/rdawes/G101OCL/Basics/igneous.html
and http://commons.wvc.edu/rdawes/G101OCL/Basics/BscsTables/igneous.html) for the information you
need to perform this lab and complete this worksheet. Read this entire worksheet before proceeding.
In this lab, you will examine ten different igneous rocks, look at them under a hand lens, look at them
under a low-power microscope, identify the minerals in each rock, determine the igneous composition of
each rock, name its texture, and take a digital photograph of each to include in your lab report. You will
choose which ten rocks you analyze, but at least two of them must be different from those analyzed by
your lab partner.
Materials Needed
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This worksheet
A set of 12 or more igneous rocks
A low-power microscope
Accessories to test and determine the physical properties of minerals, including:
o glass scratch plate
o streak plate
o piece of stainless steel (such as a knife blade)
o hand lens (with two aligned lenses, also called a loupe)
o Because calcite is not a mineral in common igneous rocks, do not use any HCl solution
for this lab
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Digital camera to take close-up, in-focus photographs of the rocks
Computer to upload your pictures and create a single digital document containing all the
photographs you turn in
There are three parts to this lab:
Part 1: Practice determining the characteristics of igneous rocks.
Part 2: Compile a complete listing, in a summary table, of the ten igneous rocks you analyze and
interpret.
Part 3: Produce a digital document that contains the pictures you took of the ten rocks you analyzed,
labeled with numbers in the same sequence as the rocks are listed in your table from Part 2.
Due by the time the next lab begins next week:
1. This work sheet, completed.
2. A single digital document that contains the photographs you took of your igneous rocks, in the
same sequence as the rocks are listed in your completed Table 4. Microsoft PowerPoint and
Word are both available to you on the WVC computers in the lab for creating your digital
document. You can use either program to create your photographs document.
Geology 101 Lab Worksheet: Igneous Rocks
page 1
Part 1: Tables Conveying All You Learn About Each Rock’s Minerals, Texture, and Composition
In the following three tables – Minerals, Composition, Texture – write down the characteristic you
determine for each rock, one by one. In other words, fill in the information for the rock you choose to be
Igneous Rock 1 in each of the three tables before you move on to Igneous Rock 2. After you have
determined and written down the minerals, composition and texture for 2 or 3 rocks, have your instructor
take a look at your work before proceeding through all ten rocks.
Table 1. – Minerals:
In the first column, list the properties you checked to identify each mineral in the rock. In the second
column, list the minerals you identified. Refer to Physical Properties on the Minerals Basics page
(http://commons.wvc.edu/rdawes/G101OCL/Basics/minerals.html#physical)
and to Identifying Minerals on the Igneous Lab webpage
(http://commons.wvc.edu/rdawes/G101OCL/Labs/IgneousLab.html#IgL6)
Many igneous rocks contain several minerals. List all the physical properties that you can determine for
each mineral. Do not write down any physical properties you do not see or test for yourself.
Name each mineral in each rock, once you have seen, and written down, enough of the mineral’s
properties to verify which mineral it is.
Igneous
Rock
Number
Physical properties used to
identify the minerals in the rock
Minerals in the rock
Igneous
Rock
1
Igneous
Rock
2
Igneous
Rock
3
Geology 101 Lab Worksheet: Igneous Rocks
page 2
Igneous
Rock
Number
Physical properties used to
identify the minerals in the rock
Minerals in the rock
Igneous
Rock
4
Igneous
Rock
5
Igneous
Rock
6
Igneous
Rock
7
Igneous
Rock
8
Igneous
Rock
9
Igneous
Rock
10
Geology 101 Lab Worksheet: Igneous Rocks
page 3
Table 2. – Composition:
In the first column, describe in your own words the overall color of each rock. In the second column
assign the corresponding igneous composition to each rock. Refer to Estimating Igneous Composition on
the Igneous Lab webpage
(http://commons.wvc.edu/rdawes/G101OCL/Labs/IgneousLab.html#IgL7)
and to Composition and Color on the Igneous Basics page
(http://commons.wvc.edu/rdawes/G101OCL/Basics/igneous.html#compcolor).
Igneous
Rock
Number
Color
Igneous Composition
Felsic, Intermediate, or Mafic
Igneous
Rock
1
Igneous
Rock
2
Igneous
Rock
3
Igneous
Rock
4
Igneous
Rock
5
Igneous
Rock
6
Igneous
Rock
7
Igneous
Rock
8
Igneous
Rock
9
Igneous
Rock
10
Remember that glassy rocks, particularly obsidian, do not follow the color rule. Obsidian, despite
commonly being black, is usually highly felsic.
Geology 101 Lab Worksheet: Igneous Rocks
page 4
Table 3. – Texture:
In the first column, describe in your own words the texture of each rock, whether it has minerals big
enough to see, whether it has holes, etc. In the second column assign the corresponding igneous texture
term to each rock. Refer to Determining Igneous Texture on the Igneous Lab webpage
(http://commons.wvc.edu/rdawes/G101OCL/Labs/IgneousLab.html#IgL8)
and to Igneous Rock Textures on the Igneous Basics page
(http://commons.wvc.edu/rdawes/G101OCL/Basics/igneous.html#igneoustxt).
Igneous
Rock
Number
Description of texture
Igneous Texture
Igneous
Rock
1
Igneous
Rock
2
Igneous
Rock
3
Igneous
Rock
4
Igneous
Rock
5
Igneous
Rock
6
Igneous
Rock
7
Igneous
Rock
8
Igneous
Rock
9
Igneous
Rock
10
.
Geology 101 Lab Worksheet: Igneous Rocks
page 5
Part 2: Summary Table, In Which You Also Name Each Rock and State How It Originates
Table 4. – Summary:
Now that you have worked through your ten igneous rocks and determined their minerals, composition and texture, compile your analytical information
about each rock into the following table. Add the name of each rock and its likely origin.
Refer to Origins on the Igneous Basics page (http://commons.wvc.edu/rdawes/G101OCL/Basics/igneous.html#igneousorg) and to the Igneous Rock
Classification Table (http://commons.wvc.edu/rdawes/G101OCL/Basics/BscsTables/igneous.html).
Rock
Minerals
Composition
Texture
Name
1
2
3
4
5
6
7
8
9
10
Geology 101 Lab Worksheet: Igneous Rocks
page 6
Origin
Part 3. Photographs You Take of the Rocks, Submitted in a Single Document
Take an in-focus, close-up photograph of your each rock that shows the minerals and texture of the rock.
You are responsible for taking and turning in your own photos. The photos in the digital document you
create for this lab must be only photos that you took yourself. Remember, at least two of the rocks you
analyze must be different from those of your lab partner. Make sure that each rock photo contains the
number it corresponds to in Table 4.
Compile your photographs into a single digital document to submit as part of your igneous rocks lab. The
photographs can be put into a sequence of slides, for example they can be inserted into a PowerPoint
slide show, or they can be inserted into a word-processing document such as Word.
Your igneous rock photographs must be labeled with numbers in the same sequence as the rocks in
Table 4 of this worksheet.
Reminder: Be sure to follow the guidelines at the bottom of page 1 for the filename of your digital
document. I will give you instructions for how to send the digital document to me.
All the parts of this lab are due by the time the next lab is scheduled to begin next week.
Geology 101 Lab Worksheet: Igneous Rocks
page 7