Name: __________________________________________ Date: _______________ Period: ________
Lab: Igneous Rocks
Have you ever looked closely at a rock? It may have formed as magma cooled. You can
learn much about rocks just by looking at them.
Lab Preview:
What will you be doing in this lab? ___________________________________________
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Purpose: To use the color and texture of igneous rocks to help classify them.
Materials: igneous rock samples, magnifying glass
Procedure:
1. Observe your samples using the magnifying glass.
2. Identify your rock samples based on color: light-colored rocks and dark-colored rocks.
Record this information on your data table in the color column- Use the labels of light and
dark.
3. Next, observe your rock samples for size of mineral grains. Record information on data
table in the mineral grain size column. Use the labels of big or small.
4. Using your notes and book, tell which minerals are present in each rock sample. Record
information in the minerals present column. (Remember some are glass, some have iron
and magnesium, some have silicate minerals)
5. Decide whether each rock is basaltic or granitic. Then, decide whether each rock is
intrusive or extrusive. Record information in the appropriate columns.
6. When your data table is complete, answer all questions.
Rock
Color
Mineral Grain
Size
Minerals present
1.
2.
3.
4.
5.
6.
Conclusions:
1. Which rocks were basaltic? Which rocks were granitic?
2. Which rocks were intrusive? Which rocks were extrusive?
3. Would you classify obsidian as basaltic or granitic?
4. What did you learn from doing this lab?
Basaltic or
Granitic
Intrusive or
Extrusive