The Metamorphic Rocks Page
All information on this page
was taken from the Geology 101 Laboratory Guide Fourth Edition - George
Mustoe
All pictures on this page
were taken from Earth, An Introduction to Physical Geology, Fifth Edition
- Edward J. Tarbuck and Frederick K. Lutgens
For individual credits for
the pictures or information, please consult these books
Before looking at each individual
rock, here are a few things you should know about Metamorphic rocks in
general:
Kinds of Metamorphic Rocks
There are two kinds of Metamorphic
rocks, Contact and Regional. Contact metamorphism takes place when
rocks are exposed to high temperatures from adjacent igneous intrusions.
Regional metamorphism takes place in rocks that are deeply buried;
the wieght of the overlying layers and plate tectonic forces produce intense
pressure, accompanied by elevated temperature .
How a Metamorphic Rock is made:
Parent rock (protolith) - slate
- phyllite - schist - gneiss
| Parent Rock (protolith) |
Increased temp. & press. |
Increased temp. & press. |
Increased temp. & press. |
Increased temp. & press. |
| shale |
slate |
phyllite |
schist |
|
| sandy shale |
slate |
phyllite |
schist |
gneiss |
| sandstone |
quartzite |
|
|
|
| limestone |
marble |
(crystal size increases) |
|
|
| basalt |
greenstone |
greenschist |
amphibolite |
|
| granite |
schist |
gneiss |
|
|
| conglomerate |
metaconglomerate |
|
|
|
| dunite |
serpentinite |
|
|
|
Foliation
Slaty cleavage - 1 direction
Phyllitic foliation - has a sheen,
no visable mica grains
Schistose foliation - nice shine,
mica grains visible
Gneissic foliation - compositional
layers
Slate
(Slate)
Has developed slaty cleavage,
rock has become harder
Phyllite
(Phyllite)
Mineral grains are microscopic,
but parallel alignment causes a silky luster
Schist
(Schist)
Grains are visible, producing
a speckled appearance
Gneiss
(Gneiss)
Light and dark minerals have segregated
into distinct zones
Quartzite
A very hard rock that has a texture
like grains in a sugar cube
Marble
(Marble)
Coursely-crystalline, fizzes in
acid, much softer than glass
Metaconglomerate
(Metaconglomerate)
Looks like Conglomerate, but the
individual rocks are squished, elongated
Greenschist
Greenish, often with phyllite-like
texture
Serpentinite
Dark greenish or greenish grey,
with slick, glasser luster
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