A prominent textural feature of phyllonitic schist in the Brevard zone is the presence of many small lenticular discs.
Petrographic analysis of the “button” or “fish-scale” texture in the fine-grained micaceous rocks in the Brevard zone in Oconee County, South Carolina, indicates that this texture has a polymorphic structure, formed by intense cataclasis, shearing, and partial recrystallization, that accompanied at least two periods of sheared-out folding. The texture can be categorically divided into two structural types. The first type is characterized by “buttons” that are made of platy minerals such as muscovite, sericite, chlorite, and graphite. The second type is an augen-shaped button characterized by inclusions surrounded by a lenticular envelope of platy minerals.
Many homogenous micaceous rock units often lack mesoscopic fabric structures. However, recognition of this type of texture and its relation to other microstructures, which are often abundant in micaceous rocks, may allow a more comprehensive analysis of how such rocks have been deformed.