Classifying Rocks Notes
Rocks form the earth’s ____________________
• 3 Characteristics are used for Identifying rocks: _____________________
Composition, _________________________, and Texture
1. Mineral Composition
• Rocks are made of mixtures of _____________________________ and other materials.
For example: Granite is made of quartz, feldspar, hornblende and mica.
 There are about __________ minerals that make up the earth’s crust and are known as _________________________________________ minerals
2. Color
• Color provides clues to a rock’s mineral __________________________.
• Granite is generally light colored that is high in silica.
• Basalt is dark-colored that is low in silica
• When identifying rocks, like minerals, color is just a starting point and tests done on minerals are also done on rocks.
3. Texture
• Rocks are made of particles of minerals or other rocks called
_________________________________. Grains give a rock texture.

• Geologists use terms based on _____________________, shape, and
______________________________ of the grain to describe texture.
Grain size:
1.
_____________________________ or small like slate
2.
_____________________________ or large like conglomerate
3.
Some are even microscopic like flint.
Grain Shape:
1.
Grain shape can result from the shapes of the
________________________ that form the rock.
OR
2.
Grain shape may result from _____________________________of several rocks.
Grain Pattern:
1.
Grains in rock often form _______________________. Some lie in
_______________________________ like stacks of pancakes. Others
________________________. Some have _________________of different colors like gneiss.
2.
__________________________ - random pattern - Quartzite
3.
___________________________ - distinct pattern like Gneiss

3 Categories of Rocks
There are 3 major rock groups based on color, texture, and mineral composition.
1.
___
2.
___
3.
___
IGNEOUS o Form from the _____________________________ of magma or lava. o Cooled Magma inside the earth is called
_____________________________________ o Cooled Lava on earths surface is called
_____________________________________
METAMORPHIC
• Forms when an existing rock is changed by __________________,
________________________________ or chemical reactions.
• Most metamorphic rock forms deep underground
SEDIMENTARY
• Mostly made up of pieces of other rocks called ______________________.

• ______________________________________causes large rocks to break then the pieces are transported by ____________________________and deposited in a basin.
• After a period of time they form rocks through processes of
____________________________________ and __________________________________