In metamorphic rocks, how is foliation produced?

Non-foliated metamorphic rock. Non-foliated metamorphic rocks do not have a platy or sheet-like structure. There are several ways that non-foliated rocks can be produced. Some rocks, such as limestone are made of minerals that are not flat or elongate. No matter how much pressure you apply, the grains will not align! read more

Foliated rocks are a type of metamorphic rock formed under intense pressure that is greater in one direction. This pressure squeezes the flat or long minerals within the rock, causing the minerals to fold or align perpendicularly to the direction of the greatest pressure. read more

Foliated rocks occur as a result of increased strain that distorts the shape of the rock in a single plane. Slate, schist and gneiss are examples of foliated metamorphic rocks. Non-foliated rocks occur when the temperatures are high but the pressure is low or equalized on both sides. These rocks do not have planar shapes of strain. read more