Metamorphic rock

• Metamorphic rock were once Igneous or Sedimentary Rocks but have been changed by great heat or pressure to form Metamorphic Rocks.
• Great pressure can occur when folding or faulting is occuring
• Great heat may be present if magma rises close to rocks in the earth’s crust.
• Metamorphic Rocks can be classified according to how they are formed.
• Thermal Metamorphism occurs when rocks come into contact with molten magma causing great heat.
• Marble is formed from the Thermal Metamorphism of limestone.
• Limestone will melt as a result of the intense heat.
• As limestone melts, its layered structure is destroyed.
• Marble is non-foliated (meaning it does not have any layers) as a result.
• The remains of any marine fossils are also destroyed by the heat.
• As the limestone rock is heated, minerals expand causing large crystals to develop.
• The colour of marble will depend on the purity of the limestone it is formed from.
• Pure marble is white and can be found in Raithlin Island.
• Green marble is found in Connemara due to the presence of copper ore, while black marble is found in Kilkenny due to the presence of carbon.
• Marble can be cut and polished and is used in fireplaces, worktops, headstones and ornaments.
• • Quartzite is formed from the thermal metamorphism of sandstone.
• Quartzite is a light coloured rock, often white although it can be slightly yellow or grey.
• Intense heat caused the quartz and silica minerals to melt.
• Silica fuses together as it cools, creating larger grains than those in sandstone
• Sandstone layers are destroyed by the heat, meaning quartzite is a non-foliated (no layers) rock.
• Quartzite is found on the peaks of mountains such as Croagh Patrick, Co. Mayo and Sugarloaf Mountain in Co. Wicklow.
• Quartzite is used in the making of glass and watches and in the surfacing of roads.
• Metamorphic Rocks may also be formed due to Dynamic Metamorphism.
• Dynamic Metamorphism occurs when plate movements cause great pressure to be placed on rocks.
• Slate forms from the dynamic metamorphism of shale.
• Slate is used as a building material and can be found in Valentia Island Co. Kerry