Metamorphic Identification Rock Lab

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Metamorphic Identification Rock Lab
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Metamorphic Rocks
Meta (to change) morphic (form) to change form
Metamorphism to change a rocks compositional and
textural characteristics
by subjecting the rock to
various pressure/temperature relationships Rock
s undergo a solid-state-transformation
The parent rock represents the pre-existing rock
metamorphism Example
Shale (parent) Schist
Limestone (parent) Marble
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Identification of Metamorphic Rocks
Identified by using the rocks Texture and
Composition
Compositional characteristics types of mineral
present common minerals quartz, feldspar,
muscovite special minerals talc, garnet,
chlorite related to P/T relationships
Textural characteristics minerals are oriented
in various
degrees of parallelism platy
sub-parallel parallel
FOLIATED
Grain size distribution fine-grain to
coarse-grain
reflects P/T relationships fine-grain
coarse-grain Low P/T
High P/T
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Slaty
Schistose
Gneissic
compressed layering - platy
Parallel to sub-parallel Mineral alignment
Alternating light and dark mineral bands
Fine-grained Low P/T
Coarse-grained High P/T
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Textural characteristics
Non-foliated texture minerals are not visible
and there
orientation does not exist
Rock is composed of single type
chemistry.
NON-FOLIATED
Example rocks composed of CaCO3
rocks composed of SiO2
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Shows NO foliation Composed of ONE COMPOSITION
How can one Tell the Difference ?
Quartz SiO2
Calcite CaCO3
Fussed glass Scratches glass Hard H 7
Sometimes xln Fizzes in HCl Soft H 3
Plant Material C -carbon
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Classification Procedure

• Step 1
• Determine if the rock is foliated or non-foliated
• does the rock contain parallelism or grains
• does the rock consist of a single chemistry with
• no visible grains?

• Step 2
• If the rock is foliated
• examine the degree of parallelism
• examine the grain-size distribution
• refer to charts for ID

• Step 3
• If the rock is non-foliated
• determine the composition of the rock
• determine the special characteristics
• Refer to charts for ID

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phanaritic porphyritic clastic glassy pyroclast
ic vesicular foliated tuffaceous chemical aphan
itic bio-chemical
I igneous S sedimentary M metamorphic