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Classifying Metamorphic Rocks

by Chris and Asyraf (7B)


Metamorphic Rocks
Metamorphic rocks are formed from igneous, sedimentary, and other types of rocks. Metamorphism is the alteration of a parent rock.The rocks morph by the heat, pressure and hot fluids that come in contact with the rock. When a parent rock alters, it must adapt to the new conditions. The parent rock, therefore, changes its mineral composition and texture. Scientists classify metamorphic rocks by these two ways: the texture and the composition. For more information, please visit Metamorphic Rocks.




Texture

Metamorphic_Rocks_01.gif


qtz-micschist.jpg
Foliated Texture
The mineral grains on the metamorphic rock lines up in parallel layers. Examples of metamorphic rocks with foliated textures are slate, and gneiss.

The three types of foliated texture:

⇥ Slately Cleavage
⇥ Schistosity
⇥ Banding


Slate forms from shale, a sedimentary rock. When shale is exposed to either heat or pressure, the minerarls within it arrange into layers. Therefore, slate seperates easily into layers. The minerals arrange into such tight layers that few particles can pass between them. Slate is widely known as watertight. Throughout the world, slate is commonly used for swimming pools, and roofing.

Gneiss forms by the change of granite and other rocks. The foliated texture of gneiss showsup as alternating light and dark bands.Non-foliated_texture.jpg



Non-Foliated Texture (Granular)
Like metamorphic rocks with a foliated texture, metamorphic rocks with a non-foliated texture has mineral grains that grow and rearrange. However, these mineral grains do not form layers. Examples of this are sandstone and marble.

Sandstone is composed mostly of quartz grains. After heating sandstone under very heavy pressure, the grains will grow and interlock. This results in quartzite.

Marble forms from limestone, composed of calcite. It is widely used for sculptures.


Composition
The composition varies by the type of rocks; for example, gneiss is different from schist. Every rock is different, for example, a gneiss and another piece of gneiss has a completely different chemical composition because the rocks have a different quantity of minerals and sediments.




Vocabulary
  1. foliated texture - ( noun ) describes a metamorphic rock, whose mineral grains line up in parallel layers
  2. non-foliated - ( noun ) describes a metamorphic rock, whose mineral grains rearrange and grow but do not form layers
  3. metamorphism - ( noun ) alteration of a parent by contact with heat, pressure, and hot fluids


Downloads:
Foliated & Non-Foliated Table OS
→ Windows

→ Mac OS





Foliated Rocks

marble.jpg
phyllite.jpg
slate.jpg
MARBLE
PHYLLITE
SLATE
garnet-schist.jpg
muscovite-schist.jpg
gneiss.jpg
GARNET-SCHIST
MUSCOVITE-SCHIST
GNEISS

Non-foliated Rocks
hornfels.jpg
amphibolite-2.jpg
quartzite.jpg
HORNSFEL
AMPHIBIOLITE
QUARTZITE



Links
Home
Rock Cycle
Metamorphic Rocks



Bibliography
Classifying Common Metamorphic Rocks
Pictures of Foliated and Non-Foliated Rocks
Classifying by Composition
Classifying by Foliated & non-Foliated Texture
Foliated Textures Information
Non-foliated texture
Foliated Texture