Wiktionary
mylonite
n. (context geology English) Any rock that has undergone modifications due to dynamic recrystallization following plastic flow; a schist created by crushed or ground rock.
Wikipedia
Mylonite
Mylonite is a fine-grained, compact rock produced by dynamic recrystallization of the constituent minerals resulting in a reduction of the grain size of the rock. It is classified as a metamorphic rock. Mylonites can have many different mineralogical compositions; it is a classification based on the textural appearance of the rock.
Usage examples of "mylonite".
Cherty quartzites interbedded with mylonites occur on the flanks of the Nandi hills, but their age is not known.