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Rocks.notebook
September 29, 2010
ROCKS
Rocks are considered the building blocks of the Earth
Rock is defined as a group of minerals bound together in some way
Igneous
Metamorphic
Sedimentary
There are three types of rocks
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Igneous
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Felsic Magma
Igneous rocks form from magma
High in silicates. Magma comes in different types
Light in color
Felsic
Mafic
There are two types of igneous rocks
Intrusive
Typically forms at the top of a magma chamber
Extrusive
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Rocks.notebook
September 29, 2010
Mafic Magma
* low in silicates
* higher in magnesium and iron
* dark colored
* typically forms at the bottom of the
magma chamber
Intrusive
Form underneath the Earth's surface as magma cools and solidifies
These rocks tend to have visible mineral crystals because of the slow cooling
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Common Intrusive Igneous Rocks
Granite
Extrusive Igneous Rocks
Form outside of Earth's crust
Cool quickly
Diorite
Very few mineral crystals are visible
Rhyolite
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Rocks.notebook
September 29, 2010
Dichotomous Key for Igneous Rocks
Common Extrusive Rocks
Obsidian
Are your rock grains sand­sized or smaller?
No
Does your rock contain quartz?
Yes
Yes
Yes
Obsidian
Granite
Does your rock look like black glass?
No
Pumice
No
Is your rock mostly dark colored?
No
Yes
Yes
Gabbro
Will your rock float on water?
Basalt
No
Diorite
Does your rock contain quartz?
Basalt
Yes
Rhyolite
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No
Andesite
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