Classifying Rocks

1
Classifying Rocks

• Chapter 4 Section 1

2
Classifying Rock

• When studying rock, geologists observe
• Mineral composition
• Color
• Texture

3
Mineral Composition

• Rocks can contain
• - one type of mineral
• - a mixture of minerals
• mineral and other substances
• Rock Forming Minerals -
• About 20 minerals make up most of the rocks on
  Earths crust

4
Quartz 1 mineral
Granite a mixture of quartz, feldspar,
hornblende, and mica
Coquina Minerals and shells
5
Minerals color and composition

• Granite light colored with high silica content
• Basalt dark colored with little silica content

6
Minerals color and composition

• The shape and color of crystals are used to
  identify rocks
• Some of the same tests to identify minerals are
  used to identify rocks

7
Texture

• Grain size
• Large coarse grained
• (easy to see)
• Small fine grained
• (microscopic)

8
Texture

• Grain pattern
• Flat layers
• Swirling patterns
• Bands of different colors
• Random

9
Rock Formation

• Igneous cooling magma or lava
• Sedimentary fragments of material are cemented
  or pressed together
• Metamorphic rocks that are changed by heat,
  pressure, or chemical reactions