* Metamorphic rocks are formed when existing rocks (igneous, sedimentary, or even other metamorphic rocks) are subjected to intense heat and pressure deep within the Earth's crust. This heat and pressure cause changes in the rock's mineralogy, texture, and chemical composition.
* Recrystallization is a key process in this transformation. Existing minerals within the rock may change their size and shape as they rearrange their atoms to form new, stable minerals under the new conditions.
* Other changes can occur besides recrystallization, including:
* Neocrystallization: Formation of entirely new minerals not present in the original rock.
* Texture changes: The arrangement of minerals within the rock can become more organized or foliated (layered) depending on the pressure.
Examples of rocks that can be metamorphosed:
* Sandstone can become quartzite.
* Limestone can become marble.
* Shale can become slate, phyllite, schist, or gneiss, depending on the degree of metamorphism.
* Basalt can become greenschist, amphibolite, or eclogite.
Essentially, metamorphic rocks are not formed by simply "recrystallizing" existing rocks, but by a complex process of transformation that involves recrystallization, neocrystallization, and texture changes.
