Metamorphic Rocks

Metamorphic rocks are those which have been changed from one form to another by the high pressure and temperature environment of the Earth. "Metamorphism" means the process of changing form. The changes can be applied to either sedimentary or igneous rock. Lutgens and Tarbuck provide a useful table of some of the varieties of metamorphic rock.

Metamorphic rock	Texture	Parent rock	Description
Slate	Foliated	Shale	Very fine grained
Phyllite	Foliated	Shale	Fine-to-medium grained
Schist	Foliated	Shale, granitic and volcanic rocks	Coarse-grained micaceous minerals
Gneiss	Foliated	Shale, granitic and volcanic rocks	Coarse-grained, non-micaceous
Marble	Nonfoliated	Limestone, dolostone	Composed of interlocking calcite grains
Quartzite	Nonfoliated	Quartz sandstone	Composed of interlocking quartz grains
Hornfels	Nonfoliated	Any fine-grained material	Fine-grained
Migmatite	Weakly foliated	Mixture of granitic and mafic rocks	Composed of contorted layers
Mylonite	Weakly foliated	Any material	Hard, fine-grained rock
Metaconglomerate	Weakly foliated	Quartz-rich conglomerate	Strongly stretched pebbles
Amphibolite	Weakly foliated	Mafic volcanic rocks	Coarse-grained

Examples of metamorphic rock

Index

Geophysics

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