A rock that has undergone significant modification of original textures by predominantly plastic flow due to dynamic recrystallization. Mylonites form at depth beneath brittle faults in continental and oceanic crust, in rocks from quartzo-feldspathic to olivine-pyroxenite composition. Mylonites were once confused with cataclasites, which form by brittle fracturing, crushing, and comminution. Microstructures that develop during mylonitization vary according to original mineralogy and modal compositions, temperature, confining pressure, strain, strain rate, applied stresses, and presence or absence of fluids.