Transcript Classifying Rocks

Classifying Rocks
Chapter 4 Section 1
Classifying Rock
When studying rock, geologists observe:
• Mineral composition
• Color
• Texture
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 Earth’s crust
Quartz
1 mineral
Granite – a mixture
of quartz, feldspar,
hornblende, and
mica
Coquina
Minerals and shells
Minerals color and composition
Granite – light colored with high silica
content
Basalt – dark colored with little silica content
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
Texture
Grain size
Large: coarse grained
(easy to see)
Small: fine grained
(microscopic)
Texture
Grain pattern
Flat layers
Swirling patterns
Bands of different colors
Random
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