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 course.

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 course	micaceous minerals
Gneiss	Shist, granite, volcanic rocks		medium to course	mineral banding
Marble	limestone	Nonfoliated	medium to course	Interlocking calcite or dolomite grains
Quartzite	quartz sandstone		medium to course	fused quartz grains
Anthracite	bituminous coal		fine	black, shiny, organic rock

Metamorphic Rock Formation

Examples of Metamorphic Rocks

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