Chapter 3 Study Guide
Classifying Rocks
1. What are rocks made of? Mixtures of minerals and other materials (soil, clay,
plant and animal remains)
2. Circle the letter of each characteristic that geologists use to classify rocks.
A. Texture
B. Mineral composition
C. Hardness
D. Color
3. True or False? Most rocks can be identified by color alone.
4. The look and feel of a rock’s surface is its texture.
5. True or False? A rock’s grains give the rock its texture.
6. Circle the letter of each sentence that is true about the grain size in rock.
A. An example of a coarse-grained rock is diorite.
B. An example of a fine-grained rock is slate.
C. Grains in fine-grained rock are easy to see.
D. Grains in coarse-grained rock are microscopic.
7. List the 4 types of rock texture: Grain size, shape, pattern and no visible grain.
8. How do geologists identify the minerals in a rock?
Observe crystals by using thin slices of rock and a microscope or doing mineral id
tests like the acid test.
9. Complete the table
Type of Rock
How it forms
Igneous
Molten rock cools
Sedimentary
Particles are pressed together
Metamorphic
Existing rock is changed
Igneous Rocks
10. Circle the letter of the definition of igneous rock
A. Rock that forms from minerals
B. Rock that contains iron
C. Rock that forms from magma or lava.
D. Rock that contains crystals
11. True or False. Extrusive rock forms beneath the Earth’s surface.
12. The texture of an igneous rock depends on the size and shape of its ___________.
13. True or False Igneous rocks with similar mineral compositions have the same
textures.
14. A rock with large crystals scattered on a background of much smaller crystals has a
porphyrytic texture.
15. What type of texture do extrusive rocks like basalt have? Fine grained
