Metamorphic Rock Classification

Metamorphic rock is classified by texture and composition. The texture can be foliated or nonfoliated.

Foliated metamorphic rocks appeared banded or layered. Foliated rocks can be ordered in terms of increasing metamorphism. In the chart below notice how each of the first three rocks become the parent rock for the next. In each of these it takes more heat and pressure to to move to the next level of metamorphism. Nonfoliated metamorphic rock usually contains one mineral. It is uniform in texture.

Grain size is another characteristic of texture.  It ranges from very fine to coarse. The metamorphic rock classification chart below may help you make sense of the many different types of rock.

Classification of Metamorphic Rocks
Name of Rock
Parent Rock
Texture
Grain Size
Notes
Slate
Shale, mudstone, siltstone
Foliated
very fine
smooth dull surfaces
Phyllite
Slate
fine
glossy sheen
Schist
Phyllite
medium to coarse
micaceous minerals
Gneiss
Schist, granite, volcanic rocks
medium to coarse
mineral banding
Marble
limestone
Nonfoliated
medium to coarse
Interlocking calcite or dolomite grains
Quartzite
quartz sandstone
medium to coarse
fused quartz grains
Anthracite
bituminous coal
fine
black, shiny, organic rock


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