Metamorphic rocks have had their structure changed and can also have their chemical make up changed because of being reheated to high temperature and subjected to high pressure.

The high temperature doesn't cause the rock to melt, but to recrystallize into new forms; if the rocks melted they would become igneous rocks and not metamorphic rocks.

There is also a contact metamorphic form caused by contact with high temperature magma that flows out of a volcano and comes in contact with the country rocks that are present.

These metamorphic changes can occur to Igneous, Metamorphic or Sedimentary Rocks.

Here are a few of the changes that take place in rocks; Granite becomes Gneiss, Sandstone becomes Quartzite, Slate becomes Schist, Limestone becomes Marble.

TYPES OF METAMORPHIC ROCKS

Eclogue                A metamorphic rock that is high in magnesium and iron. They contain garnets and sodium rich pyroxene and are formed of a high-pressure metamorphism of basalts or gabbros.

Gneiss                  It is characterized by distinct banding in its structure, it resembles schist in composition.

Hornfels              Most hornfels are metamorphosed sandstone, shale, slate and limestone.

Marble                 It is the metamorphic results of heating limestone or dolostone by either by the heat from seduction or by contact with hot magma.

Phyllite                 A low-grade metamorphism of slate, it may split along layer planes.

Quartzite             Is formed by subjecting quartz to high temperature and pressure mostly by tectonic forces.

Schist                   A rock formed by the metamorphism of shales and slates.

Serpentinite        Is formed as the low-grade metamorphic rock that formed from the hydration and oxidation of ultramafic rocks like peridotite.

Slate   Slate is a low grade metamorphic that often starts as shale or siltstone. It splits into parallel-layered sheets.

Soapstone           Soapstone is a rock formed in tectonic seduction zones.