The foliation is a feature that the many metamorphic rocks. Similar to the layering of sedimentary rocks, the foliation is a layered (planar ) texture of the rock. However, unlike the stratification, the foliation is not a result of the deposition process, but rather is caused by tectonic processes that affect the rock at high pressure and temperature. Foliation surfaces must not necessarily run parallel to existing Sedimenationsebenen. In the event of their non-parallel arrangement is called Transversalschieferung.
Minerals that the formation of sheet-like structures tend to be very strong (eg, mica, clay minerals, representatives of the chlorite group ), are governed under the directed pressure of the metamorphosis process so that the areas largest crystal growth, namely the edges are exposed to the slightest pressure, because it is energetically most favorable for crystal growth. The largest areas of these minerals therefore be perpendicular to the direction of the directed Drucks. The thus formed foliation surfaces form in many rocks as a result of further mechanical influences a system of joint planes, which can significantly affect the stability of the rock body concerned. This circumstance has geotechnical and industrial importance.
Rocks in which these features typically occur are primarily the slate, quartzite or further Prasinite. Chance have marbles, partly those which are called cipollino, set this property to.