•The process by which existing rock is changed by heat and pressure is called metamorphism

•Original sedimentary or igneous rock is known as parent rock

•Limestone is the parent rock of marble

Shale transforms to many different rock forms because of heat and pressure.

Shale turns to slate then to phyllite. Then after high temperatures phyllite changes to schist. Deep within the crust schist finally changes to gneiss.

Heat and pressure can break down the bonds that join atoms in minerals. Then the atoms join together differently as new bonds form, this is crystallization.

Recrystallization occurs when shale is formed from silt and clay.

Metamorphic rock can occur over large areas were both heat and pressure are high

The metamorphic rock slate is used for tiles and some roof materials.

Slate is useful for tiles because it displays foliation.

Foliation is an arrangement of minerals in flat or wavy parallel line.

With high pressure and heat minerals can develop such as mica to make the rocks look shiny.

Nonfoilated rocks are rocks that don’t show foliation are mainly made up of one mineral. This type of rock such as marble doesn’t split into layers.

Another reason nonfoilated rock lacks foliation is it lacks pressure.