1. Chapter 2 Lesson 2: Classifying Rocks

2. 1. What characteristic do geologists observe when studying a rock sample?
Geologists observe the rock’s mineral composition, color, and texture.
2. Name the three major rock groups and describe how each forms.
Igneous- Forms from the cooling of magma or lava.
Sedimentary- Forms when small particles of rocks or remains of plants and animals are pressed and cemented together.
Metamorphic- Forms when a rock is changed by heat or pressure, or by chemical reactions.

3. Rock -forming minerals
3. A material found in magma that is formed from the elements oxygen and silicon. _____________________________________ 4. Generally a light colored rock that has high silica content._____________________ 5. Generally a dark colored rock with relatively low silica content.__________________ 6. The 20 minerals that make up most of the rocks of Earth’s crust are known as ___________________________________
silica
Granite
basalt
Rock -forming minerals

4. The look and feel of a rocks surface.
7. What is texture?
8. To describe the texture of a rock, geologists use terms that are based on______________, _______________, and, ____________________________________.
The look and feel of a rocks surface.
size
shape
Pattern of the grains

5. the way that a rock formed.
13. Rounded grain and jagged grain describe ______________ 14. A rock’s origin is __________________________
9. Rocks with grains that are large and easy to see
9. Fine grain or coarse grain
10. Grains that are so small they can only be seen by a microscope
10. Fine grain or coarse grain
11. Grains can lie in a pattern of flat layers or can form swirls of colored bands
Nonbanded or banded
12. Have grains that do not lie in any visible pattern
Nonbanded or banded
grain shape
the way that a rock formed.