Schist
The individual mineral grains in schist, drawn out into flaky scales by heat and pressure, can be seen by the naked eye. Schist is characteristically foliated, (~leaf-like) meaning the mineral grains split off easily into flakes or slabs. The word schist is derived from the Greek word σχίζειν schíxein meaning "to split". This refers to the ease with which schists can be split along the plane in which the platy minerals lie.