Metamorphic rocks were once igneous or sedimentary rocks, but have been changed (metamorphosed) as a result of intense heat and/or pressure within the Earth’s crust. They are crystalline and often have a “squashed” (foliated or banded) texture.

Slate

• Slate is made of fine-grained interlocking crystals which lie flat in the same direction, known as the cleavage direction, along which the rock easily splits.

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Schist

• Schist is made of medium-grained interlocking crystals. Its shiny appearance is due to the mineral mica.
• Crystals line up to give the rock wrinkly layers – this is called foliation.

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Gneiss

• Gneiss is made of coarse-grained interlocking crystals.
• Crystals line up in pale and dark layers to give the rock a banded texture.

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Marble

• Marble (metamorphosed limestone) is made of calcium carbonate (fizzes with acid).
• It has medium-grained Interlocking crystals with no alignment.

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