Metamorphic rocks that consist of only one mineral that forms large interlocking crystals often have a non-foliated texture. Metamorphic rocks are rocks that are formed from existing rocks as a result of their exposure to heat, pressure, and chemical processes, mostly while buried deep underneath the earth's surface. The existing rocks from which metamorphic rocks are formed may be an igneous, sedimentary or earlier metamorphic rock. Examples of metamorphic rocks include gneiss, schist, marble, quartzite, and novaculite.
