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Metamorphic Rocks Meta – Change Morphic - Form Metamorphic rocks are formed beneath the Earths surface (usually deeper than 5 miles). Metamorphism is a process which brings about physical and/or chemical changes in a rock due to extreme pressure, high temperature, or exposure to chemically active fluids. The change to the rock occurs while the rock is solid, not liquid. The deeper a rock is buried, the higher the pressure, and the higher the temperature. Metamorphic rock texture: Foliation – A layering or banding effect in some metamorophic rocks. Caused by the parallel alignment of minerals, due to high pressure. Names are based on whether the rock is foliated, the degree of metamorphism, and the parent rock. 2 Foliated rocks: 1) Gneiss – a coarse grained, foliated metamorphic rock, containing large minerals. Parent rocks are often granite, gabbro, conglomerate. If the parent rock is discernable, name the rock with its parent rock as an adjective. e.g. Granite gneiss 2) Schist – a medium grained rock, usually with flaky, shiny minerals present. Non-foliated metamorphic rocks: Slate – a very fine grained rock, resulting from a low grade metamorphism of shale. The appearance of slate is shinier than shale, and is used to make blackboards, pool tables, roofing, tile,.. Slate Quarry in Pennsylvania Quartzite – Formed from the metamorphism of quartz rich sandstone. Can be any color, and will be very hard. Quartzite is a very durable rock, which is used frequently for tile and countertops. Marble – Formed from the metamorphism of limestone. Can be coarse to fine grained, and many colors. Will fizz with acid, since it is made of the mineral calcite. Migmatite – This is a rock that has partially melted, then solidified. It will have both igneous and metamorphic rocks within it.