What are metamorphic rocks? American Geosciences Institute

Metamorphic rocks are rocks that have become changed by intense heat or pressure while forming. In the very hot and pressured conditions deep inside the Earth’s crust, both sedimentary and igneous rocks can be changed into metamorphic rock. In certain conditions these rocks cool and crystallize usually into bands of crystals. Later they can become exposed on Earth’s surface. One way to tell if a rock sample is metamorphic is to see if the crystals within it are arranged in bands.

Metamorphic rock, Definition, Formation, & Facts

How Are Metamorphic Rocks Formed? (Full Explanation)

Glad You Asked: Igneous, Sedimentary, & Metamorphic Rocks - Utah Geological Survey

Metamorphic rock, Definition, Formation, & Facts

8 Metamorphic Minerals and Metamorphic Rocks – Mineralogy

Rocks and Minerals College of Science and Engineering

Gems Formed in Metamorphic Rocks

Basement Geology of Idaho

Metamorphic Rock Physical Geography

Rock (geology) - Wikipedia

What are metamorphic rocks?

What are metamorphic rocks? American Geosciences Institute

The Geoscience Handbook, AGI Data Sheets Fifth Edition

New York Rock Exchange: Understanding the Geological Variations of Central Park - The Observer