1. Section 3-7 How are metamorphic rocks classified?
Earth Science
Section 3-7
How are metamorphic rocks classified?

2. Classifying Metamorphic rocks
Petrologists (those who study rocks, and how they are formed) classify metamorphic rocks based on the texture of the rock.
Metamorphic rocks have 2 kinds of textures: foliated, and nonfoliated.
Original rock
Metamorphic rock
Texture
Granite, shale
Gneiss
Foliated
Granite, shale, basalt
Schist
Shale
Slate
Sandstone
Quartzite
Nonfoliated
Limestone
Marble
nonfoliated

3. Branded Metamorphic Rocks
Foliated Texture: The mineral crystals in foliated metamorphic rocks are arranged in bands.—These rocks tend to break along the crystal bands.
Foliated rocks are formed when existing ricks are placed under great heat and pressure until they melt and recrystallize into mineral that form bands
EX: Gneiss, Schist

4. Metamorphic Rocks Without Bands
Nonfoliated Rocks: Metamorphic Rocks that don’t have their minerals arranged in bands.
Nonfoliated Rocks do not break into layers.
EX: Marble and Quartzite