Metamorphic rock

Part of Hall of Planet Earth.

In the Museum’s Hall of Planet Earth, several specimens of metamorphic rocks on display. One rock display base is marked with the number eleven. AMNH/R.Mickens

The transformation of one rock to another by heat, pressure, and reactive fluids is the process of metamorphism. This process involves the breakdown of the original minerals of a rock and the formation of new ones. Individual minerals can exist only within particular ranges of temperature and pressure. Thus, the presence of specific minerals and knowledge of their compositions allow geologists to calculate the conditions under which the metamorphic rock formed.