The processes of compaction and recrystallization change the texture of rocks during metamorphism. The grains move closer together. The rock becomes more dense. Porosity is reduced. No changes in overall chemistry.
New crystals grow from the minerals already present.
A preferred orientation of minerals commonly develops under applied pressure. Platy or sheet-like minerals such as muscovite and biotite become oriented perpendicular to the direction of force. This preferred orientation is called foliation . Metamorphic Textures Foliation is a broad term referring to the alignment of sheet-like minerals. Non-foliated or granular metamorphic rocks are those which are composed of equidimensional grains such as quartz or calcite.